Human PowerThe technical journal of the

International Human-Powered VehicleAssociation

David Gordon Wilson, editor21 Winthrop Street

Winchester, MA 01890-2851, USAPhones: 617-729-2203 (home)

617-253-5121 (MIT)617-258-6149 (FAX)

dgwilson@mit.edu (email)Associate editors

Toshio Kataoka, Japan1-7-2-818 Hiranomiya-Machi

Hirano-ku, Osaka-shi, Japan 547Theodor Schmidt, Europe

Hoheweg 23CH-3626 Hunibach, Switzerland

Philip Thiel, watercraft4720 7th Avenue, NE

Seattle, WA 98105, USAIHPVA

P.O. Box 51255Indianapolis, IN 46251, USAPhone & FAX: 317-876-9478

OfficersMarti Daily, president and

executive directorAdam Englund, secretaryTess Machlin, treasurer

Paul MacCready, int'l presidentNancy Sanford, VP waterAndrew Letton, VP land

Chris Roper, VP airMatteo Martignoni, VP ATV

Theodor Schmidt, VP hybrid power

Board membersAllan Abbott

Leonard BrunkallaMarti DailyBill Gaines

Gaylord HillChet Kyle

Andrew LettonGardner MartinDennis Taves

Human Power is published approx.quarterly by the International Human-Powered Vehicle Assoc., Inc., a non-profit organization devoted to thestudy and application of human mus-cular potential to propel craft throughthe air, in and on the water and onland. Membership information isavailable by sending a self-addressedstamped business-sized envelope to theIHPVA address above.

Additional copies of Human Powermay be purchased by members for$3.50 each, and by non-members for$5.00 each.

Material in Human Power is copy-righted by the IHPVA. Unless copy-righted also by the author(s), completearticles or representative excerpts maybe published elsewhere if full credit tothe author(s) and the IHPVA is promi-nently given.

We are indebted to the authors, toMarti Daily and to Julie Drennan(MIT), whose dedicated help madethis issue possible. Dave Wilson

In this issueWHY YOUR BICYCLE

HASN'T CHANGED FOR106 YEARS

This exciting piece of history ofthe recumbent bicycle is written byArnfried Schmitz from conversa-tions with one of the people in-volved. The details of howrecumbents broke records estab-lished by more-conventional bicy-cles and the rivalries thataccompanied the desire to be thefirst to exceed 50 km in the one-hour unpaced record will both sur-prise you and will strike many fa-miliar chords. This wonderfularticle was first published by ourco-founder Chet Kyle in CyclingScience, which he also founded.He offered this and the next articlebecause he felt (and we certainlyagree) that they deserve a widerreadership. (pp 4 - 9).

THE CUTTING EDGESTREAMLINED BICYCLE

Matt Weaver attained his presentposition as arguably the leader ofthe new generation of HPV design-ers, builders and riders with hisradical "Cutting Edge" supine bicy-cle. Matt gives us his philosophybehind the design, together withdata, analysis and predictions. Thisis the second of two remarkable ar-ticles reprinted from Cycling Sci-ence that we are proud to reproducein Human Power. (pp 10-16).

LAND ROWING WITHDIRECT LEG-ASSIST

Dennis Schmidlin is intrigued,like many of us, with the potentialfor increased power being given byhuman beings using arm and backas well as leg muscles. He gives ushere a progress report on a mecha-nism he has designed and applied toa semi-recumbent bicycle. He be-lieves that the approach has consid-erable promise. (pp 17-19)

FAIRING VENTILATIONNEED NOT CAUSE HIGH

DRAGMark Drela gave HP permission

to reprint a note he sent out on the"HPV" email net - and he addeddiagrams. If you suffer inside a hotfairing thinking that putting ventila-tion ducts in will result in a highdrag, you should read this informa-tive comment (p.23).

p.2 Human Power, vol. 11, no.

SHOULD HIGH-ALTITUDEDOWN-SLOPE RECORDSHAVE INTERNATIONAL

STATUS?Peter Sharp feels very strongly

that the IHPVA rules should bechanged. They presently allow in-ternational speed records to bemade at any altitude where a com-petitor can find a road having adownslope close to (no greaterthan) that of the track where ourrecords were initially set. HPV en-thusiasts in other countries whodon't have access to similar high-altitude roads generally agree. Ourcolumns are open to reasoned advo-cacy of the status quo. (pp 20-22)

STREAMLINED BICYCLEJim McGurn, who fairly re-

cently wrote a superb book on bicy-cle history called "On Yer Bike!",has now written a beautiful book ofpraise of the bicycle called "Ency-cleopedia". Your editor reviews iton p. 19 & 23.

CORRECTION!We apologize to John Allen

and to Steve Delaire for using anincorrect photo of the Delaire Rota-tor double-recumbent tandem in thelast issue. The correct photo is onp. 23.

PREVIEWS OF HP 11/4We also apologize to those

authors who had hoped to see theirpieces in this issue. We have sev-eral short technical notes ready togo into the next issue. Steve Korenhas written on the aerodynamic ef-fects of partial fairings. BobFairchild of Ecolotech has a note onlow-cost-transportation projects.Izzi Urieli has contributed a fullcomment on Peter Ernst's paper inthe last issue on assisted HPVs, in-cluding the definition of a new unitfor application to human power, the"hup", equal to 75 watts. Mike Eli-asohn has written a short commen-tary on human-poweredlawnmowers. Andreas Weigl hasgiven HP permission to use his arti-cle on future tire developments.John Kingsbury has sent a note anddiagrams about a new pedallingmechanisms he is testing. PeterSharp has two more concepts foryour interest. And there is more!

Dave Wilso,

.

. n~~~~~ I

I-

_

.

3, summer/fall 994

WHYYOUR BICYCLE HASN'T CHANGED

FOR 106 YEARSCharles Mochet and his Recumbent Veltocar were Torpedoed by the UCI in 1934.

Streamlining was Banned in 1914.

ARNFRIED SCHMITZ: Lioux-Gordes, France

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Original mechanical drawing of Charles Mochet's Velocar supine recumbent bicycle, 1933. Francis Faurebroke the world hour record on this bicycle going 45.055 km, July 7, 1933, Parc des Princes, Paris.

If anyone were alive today who rodethe Starley Brothers' Rover Safety cycle in1884/85, they could climb on today'sbikes and pedal away without a secondthought. They could recognize nearlyevery part of a modem bike except the seatstay which was added about 1889 tocomplete the familiar diamond frame.Why? Everything else in this turbulentworld has changed beyond recognition,clothing, architecture, the automobile, theairplane -- why not the bicycle? Theanswer lies in a drama that unfolded in the

early 1930 s when Frenchman CharlesMochet shook the conservative,traditional bicycling establishment withhis sensational Velocar.

The Velocar was a sleek recumbentbicycle, and when raced by several pro-fessionals of the day, it proved to be muchfaster than a standard bicycle. The reasonwas pure and simple - aerodynamics. ButI'm getting ahead of my story, let's start atthe beginning. I'm sure the readers ofCycling Science will want to know all

of the details. Actually this story hasn'tbeen published in the United States formore than 50 years.

I talked at length to Georges Mochet,the son of Charles, and he gave me copiesof original documents as well as many ofthe photos that accompany this article.Georges lived through this whole era,visited the bicycle tracks of Europe, andran his father's business after CharlesMochet's death in 1934. His story is animportant part of bicycling history,

JUNE 1990 CYCLING SCIENCE

p. Human Power vol. 1 no. 3, summer-fall, 1994

3

....

.

·/X r-e- mtaaae

slow due to extracurricular activities andthen college. The Cutting Edge, the firstbicycle I built, was completed in thesummer of 1989, although I didn't prove itin a race until Fall of 1990.

At the 1990 International HumanPowered Speed Championships (IHPSC)held on the two-mile Portland InternationalRaceway, I pulled into the lead uponcompleting the second lap of the 20-milecriterium. By the finish I nearly lapped theentire field except the Gold Rush, whichwas 0.5 mile (47 seconds) behind and untilthen had never been beaten. I reached 56mph on the straights, and averaged 42.4mph for 20 miles while coasting and brakingfor nearly half the distance due to the manyturns. The bike handled very well in theturns, and I found I could gain on the GoldRush in the corners.

An improved Gold Rush, dubbed theGold Rush LeTour, was built followingPortland. With Fred Markham pedalling, itset the flying 1000-meter record of 41.870seconds (53.426 mph) on July 4, 1991. Wemet at the 1991 IHPSC, and again I tookfirst place in the 20-mile criterium, whichcircled 1.8 miles through a park. The GoldRush LeTour was close on my tail for theentire race, but in the final lap I neverdropped below 51 mph and won by severalhundred meters. Even so, I have yet to tryand challenge Freddy Markham's awesometop-speed record set in Gardner Martin'sGold Rush.

Prior to beating the Gold Rush, severalexperts said, "It's a pretty bike, but it's toolow, etc...to handle well or allow the rider topower out. The speeds will be verylimited...." After Portland I heard incontrast, "Of course, it's obvious...." Wellanyway, I'll explain how I did it, since veryfew saw the potential of the bike before Iraced it.

THE DESIGN PROCESSIt is well known that air drag dominates

a bicycle's top speed on level ground. Infact, the power requirement to overcome airdrag goes up with the cube of velocity (thisassumes a constant drag coefficient withspeed, a good approximation in this case).It is important to know relative drag forces,which have been tabulated by Gross andKyle [1,2,12] for many vehicles andcomponents. With this in mind, I first askedwhat is the ideal or theoretical limit forminimizing air drag. The concept of such avehicle helps aim the design process in theright direction. Ignoring everything else,namely that a crank needs room to pedal, I

found the ideal shape would be a two-wheeled, minimum-.frontaarea, nearlyaxisymmetric teardrop enclosing a riderlying horizontal. Such a theoretical vehiclecould average 90 mph with a 0.5 hp input,which is what many cyclists could sustainfor an hour! The estimated vehicleparameters were the drag coefficient Cd =0.05, the rolling resistance coefficient Crr =.003, and weight W = 180 pounds.

Unfortunately, Calvin's daredevil speedsdon't come so easy. The vehicle mustpossess certain properties such ascontrollability, visibility, crash protection,and ventilation. It also needs elements suchas a drive mechanism, a frame and fairing,and possibly suspension. You find yourselfquickly deviating from the ideal limit of ateardrop pod. The goal of course is todeviate as little as possible. I worked hardon designs to achieve this, and succeeded indeveloping a functional design that is muchcloser to the ideal limit than had previouslyever been devised. I will discuss myinsights and findings that make such astreamlined bike possible and also enable itto possess excellent performance properties.

ELEMENTS AND PROPERTIESControllabilityThe property of controllability means

a vehicle in which the rider can follow adesired path with relative ease. This is ofcourse a simple task on most bicycles.However, when you add a fairing, getlower to the ground, and experiencesidewinds it is an entirely different story.The popular solution for some time wasto build a tricycle, but that has since beenoutperformed by the now prevalent semi-recumbent bicycle style initiated by theworld-record-holding Gold Rush andothers. The semi-recumbent style stillhas an excessive amount of frontal area;so, let's examine how we might be ableto reduce this area further and stillmaintain good control.

Before making a turn, the bicycle mustfirst be leaning in the same direction. In aconventional bicycle, the rider can shift hisweight to initiate a lean. Within a smallstreamlined fairing, the rider may not beable to shift his weight. Instead he mustrely on the steering in order to lean. A leanto the left is achieved by initially steering tothe right, and vice versa. This effectivelygets the wheels out from under you and tothe side. The steering will float into thedirection of the lean and then you willbegin turning. The turn is finished by

"leaning" out of it, or in other words bysteering into the turn. This procedure putsmuch greater importance on the inherentstability of a bike.

A properly designed conventionalbicycle will ride upright in a straight linewith "no hands." This ability arises as aresult of the steering geometry of the bike,the fact that it is moving, and variousdampening forces. Contrast that with aunicycle, which is "stable" only with atrained rider who is dynamicallycompensating every little lean before hittingthe pavement. It is desirable to have astable vehicle so that the rider canconcentrate on applying power.

The "no hands" stability of a bicyclechanges considerably as the rider getsmuch lower to the ground. Lower isdesirable because you can pack the riderand wheels "in line" in a single teardropregion with a much smaller frontal area.However, a bicycle is like an upside-downpendulum that pivots about the lineattaching the tire contact patches. As themass of the rider gets closer to the ground,the moment of inertia about this axisdecreases, and the vehicle leans quickerfor a given disturbance. Conventionalroad bike geometry works poorly here, soit is necessary to determine what ifanything may work.

Modeling BicycleDynamicsSeveral articles [3,4,5] I've studied

illustrate trends in the stability of thebicycle. There is much dispute in this area,and I consider it difficult to concludeanything if the rider is free to shift hisweight as with a conventional bicycle.Fortunately I can assume the rider is fixed inthis case, so I went about developing anumerical model in an attempt to simulatethe behavior of the bike.

The model first consists of detailedgeometric calculations which depend onmany parameters including the width of thetires as well as the state of lean and steerangles. The values obtained are then used ina system of differential equations whichaccount for all the dynamic forces such asthe acceleration due to turning and thegyroscopic forces, etc. These equationswere solved iteratively using a Runge-Kuttascheme. By applying different initialconditions and external disturbances, I couldobserve the response of various geometries -overshoot, oscillations, and even crashing.Rather than attempt to discuss the details of

CYCLING SCIENCE 18 SEPTEMBER AND DECEMBER 1991

Human Power vol.11 no.3, summer-fall, 1994, p.11

the modeling here, I will simply say adesirable geometry was found that closelyresembles the Cutting Edge. The CuttingEdge uses a 20.-inch front wheel, a 700Crear wheel, and has a 66 ° head angle, a 1-5/8inch fork offset, a 2.7 inch trail and a 52inch wheel base. If any of the readers wantfurther details about my theoreticalapproach to solving the vehicle stabilityproblem, please write to the address given atthe end of this article.

Sidewind StabilizationA final factor that strongly effects the

controllability of a streamlined bicycle issidewinds. Those familiar with using front-wheel disks know that sidewinds canproduce some unpleasant torques on thesteering. Similar, yet much worse, are thelifting forces on a typical streamlinedbicycle moving along in excess of 40 mph.The force vector points predominantly to theside and slightly forward. This means youmight get propelled forward a little, butmost likely you'll get blown over.

There is neat solution, however. Ifound that by properly setting thegeometry of the bicycle relative to thefairing and its associated center ofpressure (the imaginary point on thefairing where the resultant aerodynamiclift force acts), the bicycle willautomatically lean into a good range ofsidewinds. This results from steeringtorques induced by wind pressure, causingthe bike to momentarily steer away fromthe wind, and thus generate a lean into thewind. The trick is to try to tune this asbest possible. The numerical modeldiscussed previously can be used toanalyze this, where the configuration ofsuch a bike is characterized by the frontwheel being relatively far back from thenose. The Cutting Edge approximatesthis; however, it actually overcompensatesa little - I find myself gently steering outof a lean into the sidewind.

VisibilityThe rider needs a windshield, and

experience has shown that one has muchbetter control with peripheral vision;therefore, a windshield should extendaround the sides of the face. If thewindshield gets too large, it could act as agreenhouse which cooks the rider inside.Second, the more light that gets inside thefairing, the greater the glare. Third, glareincreases as the viewing angle is moreparallel to the windshield surface, which istypical of large windshields. Finally,

because of the poor structural properties of alarge windshield, it is a vulnerable spot in acrash. Clearly, smaller is better so long asthe full visual field is maintained.

To maintain the visual field in the supineposition, you can either sit fairly flat,looking through the legs and have a largemolded windshield on the front of the bikelike the Vector tricycle, or you can sit in amore upright position, raising your eye leveljust above your knees and look out a smallwindshield and over the top of the car. Thesmall windshield profile has slightly morefrontal area, but I found it generallypreferable over the disadvantages of thelarge windshield.

Crash ProtectionDangerous speeds are possible with

streamlined bikes, so safety needs to betaken seriously. You can be severelydamaged internally by a high-speed impactor get gored by something sharp. The bestthing is to find a safe race course with nosolid objects anywhere, but unless you arerunning the race you cannot be sure whatyou'll get.

For impacts you want a "crush zone"which will soften the deceleration. This canbe achieved fore and aft, but it wouldrequire ridiculous aerodynamic costs toenlarge the sides. It is essential to assurethat the sides will protect against abrasion,which most fairing materials will do,provided they remain intact.

You eliminate goring by carefulplacement of components and by makingsure there is nothing sharp or blunt thatmight contact the rider in a crash. In myvehicle, the seat serves as a fairly effectiveseat belt, to restrain forward motion.Padding of frame members that might causeugly bruises is a good idea. Also, it isessential to design the fairing so it doesn'tfall apart. Fiberglass and acrylic tend toshatter and come apart - becoming lethalblades, and possibly exposing you to roadrash at 50 mph.

Most fairings in the past consisted of atop and bottom half that were usually tapedtogether, which has poor integrity in a crash.The Cutting Edge is a one-piece Kevlarfairing with a single split down theunderside which is literally bolted shut.This has excellent integrity, and is also veryaerodynamic since there is only one seamin-line with the wheels. There is no stress at

this seam that would cause the fairing todistort as is the case with side-split fairings.

There are other methods to achieve this sortof integrity, but they involve substantiallymore fabrication.

VentilationIt is necessary to get cooling air to the

rider for longer races. First, you don'twant any more flow than necessary;secondly, you want to vent it as efficientlyas possible. Zero efficiency occurs whenthe air blasts into the fairing and swirlsaround losing all its momentum. Excessventilation or poorly controlled ventilationwill raise the aerodynamic dragsubstantially. The most efficient wayoccurs if the air pressure inside the fairingis near the external stagnation pressure andyou have proper ducts. Then, the airentering decelerates and pressurizes -preserving its internal energy to be lateraccelerated out a nozzle. The difficult partis selecting entry and exit locations suchthat a slight pressure gradient exists andsealing the fairing to maintain pressure. Iwas unable to achieve ideal ventilation dueto limited time available for construction.However, with air entering at a small ventat the base of the windshield, and exitingat the rear of the front wheel, it passesdownward over the body for effectivecooling. I've also found that cooling canbe enhanced by using an evaporativemethod such as a fine water mist added tothe entry flow. I have not used this,however, in racing.

To eliminate undesirable flow at thewheel cutouts, a stretched latex panel withnylon trim was designed to go around thewheels. This not only eliminates almost allthe flow into the wheel holes, but also formsa smooth aerodynamic fillet between thefairing/wheel interface. Under normaloperation, the fillet does not contact therotating wheel. Other ways to achieve thisare more complex.

Riding Position andDrive TrainSince maximum streamlining is desired,

the riding position that can fit into thesmallest teardrop-like shape is optimal.This can be achieved using a sitting positionwith the legs directly in front. It can also bedone with a head-first position, but Iconsider that too unsafe to be an option.Deciding to have the legs in front is only thebeginning. The actual drive mechanism,how you see out and how all thecomponents that make a bike fit around you,are yet to be determined.

CYCLING SCIENCE 19p.12 Human Power vol, 1 io. 3, surmrirei-;ai, 1994

SEPTEMBER AND DECEMBER 1991

TABLE 1. SPECIFICATIONS OF THE CUTTING EDGE.

HeightWidthLengthWheel baseHead AngleFork OffsetTrailWeight

Frontal Area

Drag Coefficient

Drag Area CdAWheelsTires

BrakesGearing

Engine Size

Construction

35 inches, (89 cm)16 inches, (41 cm)114 inches, (290 cm)52 inches, (132 cm)66 inches, (168 cm)1-5/8 inches, (41.3 mm)1.7 inches, (43.2 mm)24.0 lb frame, 10.9 kg12.0 lb fairing, (5.4 kg)Total 36 pounds, (16.3 kg)

2.8 ft2 (average, pedalling), (0.26 m2 )

2.65 ft2 (not pedalling), (0.246 m2 )0.11 -0.13

0.30 - 0.35 ft2 , 0.028 m2 - 0.033 m2)700C rear, 20" front; 32 spokes with Mylar covers20xl inch IRC Roadlight clincher front700x20C Specialized Turbo VS clincher rear.Conventional side-pull rim brakes70 tooth front sprocket24x9 rear cluster76 to 206 gear inches6' 2" (188 cm), 175 lb (79 kg), 1.5 HP (1120w) for 30 sec,1.18 HP (880w) for 60 sec, 0.5 HP (373w) for 1 hour.carbon fiber/epoxy frame, kevlar/vinylester fairing

of building an expensive female mold, Ilaminated two layers of 5 oz. Kevlar withvinylester resin directly over the plug. Theouter surface was meticulously smoothedusing microballoons, and finished with acoat of white enamel paint with a flex agent.The fairing was originally designed for alinear-drive mechanism which was shelvedin favor of a conventional crankset due tolimited time. This meant I'd either startover or else painfully cut holes in the fairingto allow for leg motion. The holes are ofcourse terrible aerodynamically, but ratherthan make "bubbles" they were coveredwith a latex film and an internal nylon linerthus maintaining nearly the original flow.The latex stretches temporarily when theknees penetrate the fairing.

The frame was decidedly asymmetric,and the geometry was analyzed using afinite-member approach. Other geometrieswere considered, but they require certainconsiderations I didn't want to deal with atthe time. The frame was built using carbon-fiber tubes mitered together followed bylayering unidirectional carbon fiber at thejoints to form lugs. The carbon fiber wasmanually impregnated with epoxy betweensheets of plastic using a method whichachieved near-optimal resin ratios beforecompressing the laminate together.Aluminum and steel inserts were embeddedat critical stress points. The seat was sewntogether using nylon fabric and components.

As soon as the bike was assembled, Iwent tearing off around my neighborhood todiscover with great satisfaction and reliefthat it actually worked! My father andbrother-in-law rode next. Later I wasfortunate to have the experienced support ofGardner Martin and Freddy Markham whenI first rode the bike with the fairing on.Everything has worked flawlessly - not evena single derailment of the chain! To giveyou an idea of just what the bike is like, thefinished Cutting Edge is summarized inTable 1.

PERFORMANCEThe big question is, "what will it do?"

To make any estimate we need to know thedrag characteristics, the masses involved,and also the performance of the "engine."From there we can determine cruisingspeeds in different conditions as well as theacceleration behavior.

Drag CharacteristicsModeling the aerodynamics of

something as complex as the Cutting Edgeis next to impossible. To truly account forall the interference, internal flows, etc...would require a model probably ascomplex as that of a large airplane.Likewise, a wind--tunnel model cannotaccount for all these factors. About theonly reasonable thing you can do usingthese methods is to see if there are anygross errors such as separation of the flow

from the fairing using these methods.

Not too surprisingly, this leaves fieldtesting as the only option. A coast-down,or deceleration, test on a level road withno winds will give the best quantitativeresult one can hope for. It is possible todeal with small slopes ( <1%) if a levelroad cannot be found. The test consistsof first recording a time history of thevelocity of the vehicle coasting fromsome initial speed. Then you calculatethe time derivatives of the velocity datato get the negative acceleration rate.Rearranging each sample point into theform given in Equation 1 followed by aleast-squares polynomial fit to the datawill reveal the unknown coefficients onthe right--hand side.

Note that I have neglected rotationalinertia in this case. Also, uncertainty maydrown out the small terms in the equation.There are also other methods of determiningcoefficients from coast-down testing. I've

found CdA to be between 0.3 and 0.35 ft2

for the Cutting Edge, and used ChesterKyle's measurements of rolling-resistancecoefficient, Crr = .0035 [9].

The EngineThe human body is a very dynamic

engine as we know from its aerobic andanaerobic modes of energy utilization.Once fatigue sets in, an extended amount oftime is necessary for recovery. Thisstrongly affects the approach taken duringtop-speed accelerations. To determinepower output, you can either find some sortof ergometer or trainer as Kyle [10] hasshown, or else time yourself up a steep hillof known slope. I did the latter on the same12.5% slope first used by Pavish [11] todetermine Freddy Markham's output. Isimulated the entire climb and the slopevariations that occur during it by integratingEquation 2 to get position and solvediteratively for power.

1. -[(W/g + Iw/r 2 )dV/dt + Wsin(tan'1(slope))] = CrrW + (1/2)pCdAV2

2. dV/dt = (g/W)[TqP/V - CrrW -

(1/2)rCdAV2 - Wsin(tan-l(slope))]

where:

V = Velocity, ft/sec

W = Weight, 211 pounds

Iw = Moment of Inertia of the wheels

Slug-ft2

r = wheel radius, ft.

CYCLING SCIENCE 21 SEPTEMBER AND DECEMBER 1991

p.14 Human Power vol. 11 no. 3, summer-fall, 1994

P = Power output, ft-lb/sec

g = gravitational acceleration

1 = Mechanical Efficiency = 0.95

p = Air Density = 0.002378 slugs/ft 3

@ sea level

Crr = Roll. Res. Coeff. = 0.0035

Cd = Drag Coefficient = 0.125

A = Frontal Area = 2.8 ft2

Slope = rise/run

All aerodynamic and rolling drag forcesare included, but their contribution isminimal and consequently uncertainty inthose parameters is not critical. What youneed to know accurately is starting velocity,distance, time, and total weight. I foundthat I could produce 1.18 ± 0.02hp for alittle over 60 seconds, and between 0.45 and0.5hp during steady 1-hour training ridesthat included the hill. I rode the CuttingEdge unfaired to 39.5 mph during a 30.00'second quarter-mile drag. Simulation showsthat this drag would require a 1.5hp averageoutput. Other studies of power versus timereveal similar results [12].

Maximum SprintA maximum speed will be obtained if

the cyclist first reaches near steady statewith an aerobic output, and then followswith a maximal effort. The rider willnaturally fatigue during the sprint, andideally he will pass through the timing trapswhen his power just equals the drag power.To see just what can be done, I will assumean aerobic output of 0.5hp to be followedwith a 90-second linearly decaying effortthat varies from 1.4hp to 0.8hp. I solvedEq. (2) for velocity and position using aRunge Kutta scheme, and the resultingacceleration curves are given in Figure 1.

Several variations of the sprint areillustrated, such as: (A,B) starting theanaerobic sprint at 1 or 2 miles, (C)increasing aerobic output to 0.6hp prior to

Figure 1. Acceleration Profiles

.E

75

/ /

55A-68.7 mphSprint@1 mileA - 68.7 mph, Sprint 1 mileB - 69.6 mph. rnt @ 2 milesC - 70.4 mph, 0.6 HP Aerobic

4545-- /// -D - 73.7 mph: a(:) feet AlmtuE - 74.7 mph, - 0.5 % Slope

40 0 0.5 1 1.5 2

Distance, miles4

Several variations of the sprint are illustrated such as: (A) starting the sprint atone mile, (B) starting at 2 miles, (C) increasing aerobic output to 0.6 hp prior tosprinting, (D) increasing altitude from sea level to 8000 feet, and (E) runningon a constant 0.5% downhill. It is interesting that the 0.5% downhill does morefor increasing velocity than the 8000 foot altitude (air density = 0.001869slugs/ft3. Also the top speed is largely determined by the anaerobic powerprofile. It would be useful to record time/power histories for different anaerobicpower profiles of the cyclist and determine what is optimal.

sprinting, (D) increasing altitude from sealevel to 8000 feet, and (E) running on aconstant 0.5% downhill. It is interesting tonote that the 0.5% downhill does more forincreasing velocity than the 8000 footaltitude (air density = 0.001869). Also, thetop speed is largely determined by theanaerobic power profile. It would be usefulto record time histories for differentanaerobic power profiles of the cyclist anddetermine which is optimal. Unfortunately,because of wind, or curves along the racecourse, I have never had the chance to usean optimization strategy to achieve top

speed with the Cutting Edge. This remainsas a future project.

Aerobic SpeedsIn extended aerobic events the rider can

reach a steady velocity where his poweroutput equals the drag power. The resultsfor the Cutting Edge are found byintegrating and solving Equation 2 forvelocity. I have shown velocities forseveral slopes, including Calvin's favorite, -20%! It is clear that the velocities increase

dramatically with even small slopes. Partof the explanation lies in the fact that as you

TABLE 2 - PREDICTED STEADY STATE SPEEDS, CUTTING EDGE

POWER UP (+) SLOPE % DOWN (-)(HP) +1 +0.5 0 -0.5 -1 -6 -200.0 0.0 0.0 0.0 18.8 39.2 115.3 213.10.1 12.0 17.3 26.3 37.6 48.5 116.8 213.50.2 21.8 28.4 36.7 45.8 54.7 118.2 214.00.3 29.5 36.1 43.7 51.6 59.5 119.6 214.40.4 35.7 42.2 49.2 56.4 63.6 120.9 214.80.5 41.0 47.1 53.7 60.4 67.1 122.2 215.20.6 45.5 51.4 57.6 64.0 70.2 123.4 215.7

SPEEDS ARE IN MILES PER HOUR

CYCLING SCIENCE 22 SEPTEMBER AND DECEMBER 1991Human Power vol.11 no.3, summer-fall, 1994, p.15

.5 3 3.5

IL.7a)

o

.a,

Figure 2go faster down a hill, you extract more"gravity power" and consequently buildconsiderable speed.

Table 2. shows that with a rider of thelikes of Francesco Moser, you are knockingon the door of a 60 mile 1 hour time trial!Likewise, for ultra-distance events, 1000--mile 24-hour trials may be possible!

CONCLUSIONAs a result of hammering away at the

limits of cycling science, a totally newstreamlined bike with excellent performancecharacteristics has been realized. We haveshown that: 1 - The rider and wheels can bemapped into the same frontal area and thusproduce a very small and nearlyaxisymmetric profile, which has thepotential to have the smallest dragcoefficient and also the least sidewindsensitivity. In fact, you cannot squeeze intoa more streamlined profile withoutperforming undesirable physicalcontortions. 2 - Only two wheel-fairinginterfaces are necessary, and they are farback so as to not disturb the laminar flow atthe nose of the fairing. 3 - Sidewindstability is achieved, allowing better controland rider concentration. 4 - The low centerof mass enables highly responsive turning -theoretically, quicker than anything elsethrough a tight slalom because less time isspent in transitions. 5. - Excellent visibility,protection, ventilation and riding comfortwere achieved with little compromise.Historically, record-setting streamlined

Time, minutes

human-powered vehicles have notperformed as well. Faired upright bikes,low tricycles, and finally semi-recumbentbicycles have suffered from such things asexcessive frontal area, poor aerodynamicshape and ground effects, rolling over inturns, and adverse sidewind behavior.

Top speeds in excess of 70 mph arepresently possible, and are largely limitedby one's anaerobic power capability.Aerobic speeds approaching 60 miles forthe hour, and 1000 miles for 24 hours arealso possible! Of course, you might catchCalvin saying, "Who needs a hill with abicycle like this?!"

REFERENCES1. Gross, A. C., Kyle, C. R., & Malewicki,D. J., "The Aerodynamics of Human-powered Land Vehicles," ScientificAmerican, pp. 142-152, December 1983.

2. Kyle, C. R., "New Aero Wheel Tests,"Cycling Science, pp. 27-30, March 1991.

3. Jones, D. "The Stability of the Bicycle,"Physics Today, p.34, April 1970.

4. Lowell, J. and McKell, H., "The Stabilityof Bicycles," American Journal of Physics,p. 1106, December 1982.

5. LeHenaff, Y., "Dynamical Stability ofthe Bicycle," Human Power, pp. 15-18,Spring, 1987.

6. Abbott, I. H., and Doenhoff, A. E.,Theory of Wing Sections; Including aSummary of Airfoil Data, McGraw Hill,NY, First Edition, 1949.

7. Hoerner, S. F., Fluid-Dynamic Drag, 148Busteed Drive, Midland Park, NJ, 1958.

8. Hoerner, S. F., and Borst, H. V., Fluid-Dynamic Lift, Hoerner Fluid Dynamics,Brick Town, NJ, 1975.

9. Kyle, C.R.,the RacingEngineering.1984.

& E.M Burke. ImprovingBicycle. Mechanical109:6:35-45. September

10. Kyle, C. R., "The Power Output ofBicycle Trainers," Cycling Science, pp. 4-10, September 1991.

11. Pavish, D. L., "UnsaddlingHorsepower," Bike Tech, pp. 13-16, Feb.1988.

12. Nonweiler, T., "The Work Production ofMan; Studies on the Racing Cyclist,"Proceedings of the Physiological Society,January 1958.

AUTHORMatt Weaver, is a seniorMechanical Engineering student at theUniversity of California at Berkeley, whowill graduate in December 1991 with aBSME. He was awarded the prestigiousDrake Scholarship which covers 4 years offull expenses to attend U.C. Berkeley. Inhigh school he was a winning middle.distance runner who was offered aUniversity track scholarship, but hedecided to pursue Engineering studies fulltime. Weaver has had extensiveexperience in Computer Science andEngineering, and was originallyconsidering a double major. The first yearhe entered the International HumanPowered Speed Championships in 1990,he won the road race, beating former U.S.Olympic rid',;r Fast Freddy Markham,who had not been defeated for severalyears. Weaver also won in 1991. He hasnot had a chance to test the machine on anideal course for top speed. For thoseinterested in more information on thestability analysis computer code, write:

Matt Weaver1760 Wilshire Dr.Aptos, CA 95003. (408) 688-5389.

CYCLING SCIENCEp.16 Human Poweri v'i. d : no.

233, summer-fall, 1994

SEPTEMBER AND DECEMBER 1991

.

ighter weight and ease of manufactur-ng. Overall vehicle weight will betround 15 to 18 kilograms (35 to 40)ounds) with ball or needle bearings atll pivots.

Laterally balancing the drive mecha-lism gives a smooth, non-binding motioneven while pushing with one foot. In ad-lition, the downward angle of force fromhe rider's legs on the footrest assembly

Figure 2 Space frame and mechanism

counters the upward angle of force fromthe lever arms. All of this greatly re-duces friction in the linear motion of thefootrests and increases the overall me-chanical efficiency of the system.

The design utilizes all available en-ergy in the power stroke and is aided bythe deflection of the primary drive chainby the journal shaft at pivot "P", figure 3.By "folding" the chain at the end of thestroke, the rider's arms and legs, alongwith the drive mechanism, are deceler-ated, and the energy is transferred di-rectly into the drive train. This occurs atthe point in the motion where the rider'smechanical advantage is very high, anddelivers a small power burst at the end ofeach stroke instead of wasting the rider'senergy in stopping the motion with armmuscle. Acceleration of motion in the

return direction is aided by the returnspring "S", and the return stroke deceler-ates as the rider's legs lift and compress.Thus, kinetic energy is naturally con-served in both directions.

More usable energy may be obtainedthrough the use of spring biasing. Withbiasing, energy can be stored from thereturn stroke to be added to the drivestroke. I still experiment with it, butthrough trial and error, I soon discoveredthat the return stroke (bench-press andstomach-curl motion) is a poor exercisefor driving a H.P.V. Power contribution,overall, is very small. For anyone dis-puting this, try lying on your back andbench pressing even the weight of yourempty hands for one hour. Control of thevehicle also suffers when alternating be-tween pulling and pushing hard on thebars. For distance riding, I prefer just thereturn spring shown, to lightly bias themechanism in the return direction. Itkeeps things simple, and it gives me aquicker return through this low-power orno-power stroke. (This quick returnwould not be possible with Harrison'shypothetical forced rowing machine, norwould the ability to coast or choosestroke length.) Power rowing combinesthe best of forced and free-rowing forms.

Qncara/ M&aclOIct

Of course. performanceis the real test of anyH.P.V., and my results sofar have been very promis-ing. I can cruise comforta-bly at 6 to 7 meters persecond (13 to 16 mph) forlong periods of time and canreach 11 or 12 m/s in shortsprints. This is about asgood as my performance on

p.18, Human Power vol. 11 no. 3, summer-fall 1994

Figure 3 L

my aluminum diamond-frame racing bi-cycle, using just a crudely made 30 kg.(65 pound) test vehicle. Also considerthat I have relatively little rowing experi-ence in my lifetime as compared to bicy-cling for the last 35 years, and the resultslook even better. I fatigue a little soonerwhile rowing, but, again, I attributemuch of this to lack of rowingexperience.

My initial results indicate that my topspeed may be hindered slightly more bywind resistance than that of a pedal-driven vehicle. The row bike begins todecelerate quicker between powerstrokes at high speeds. The same thingbecomes apparent when climbing hills.Fortunately, the mechanism's quick-return stroke and the excellent aerody-namics of the sculling position help tooffset this effect. Perhaps a row bikewould be a perfect place to implement ashort-term energy accumulator or"massless flywheel" such as described byJohn S. Allen in the Fall/Winter 91-92issue of Human Power.

HandlingFor obvious reasons, I am trying to

perfect the bike's handling first, ratherthan concentrating on speed. The steer-ing system is another departure from thenorm, but it is actually very simple andhandling feels quite natural. The handle-bars are mounted on a "floating" steeringhead, supported by the articulated paral-lelogram linkage as shown. This posi-tions the handlebars at a more operableangle to the operator throughout thestroke. The only controlling link to thefront wheel is through flexible sleevedcables. I think most people would expecthe steering to be mushy due to cable-sleeve compression but the heavy-gaugemotorcycle control cables that I use givea very solid feel. The system is light-weight and offers many new possibilities

Wetails of energy-conserving mechanism

Figure 1 Elevation drawing of the leg-assist rowing bicycle.

-

One option is the use of steering ratios)ther than 1 to 1. I have experimentedextensively with this and to my surprise,very stable handling characteristics were)btained with a continuously varying ra-io! To accomplish this, I use mounting)ins "M" on my fork for the cable con-nections, similar to those used by Don3arry on his Infinity recumbent bicycles.rhe opposite cable ends are wrappedwver a round pulley on my steering head.Fhis arrangement results in steering thats slow while on center and quickens asyou turn in either direction. Along withhe enhanced stability, this solved my)nly real problem concerning handling,which was "twitchy" steering while pull-ng hard on the bars. I am experimentingwith a bolted-on head tube with which I:an vary the angle from 60 to 80 degrees,and several different fork rakes to perfectny handling. Factors affecting controlnclude: pulley diameter, stem length,handlebar width and shape, stroke length,)arallelogram geometry, cable frictionmd preload, rake, trail, wheel base, andwidth of seat. I've discovered that thebike's handling becomes a matter of per-,onal taste, but I am working towards thenmost natural feeling combination thatrequires the least attention from the ridern all situations. Overall, I am as pleasedwith my handling performance as I amwith my speed.

Dual-Drive and Tandem CapabilityAnother embodiment of the vehicle

could include crank arms and pedals onthe jack shaft operating as a standard bi-cycle crank. This dual-drive modelwould enable the rider to stand and pedalas an aid in hill climbing, and the onlyadditional weight would be the pedalsand crank arms themselves. If a luggagerack were designed to double as a backseat the bike could then be ridden as atandem. The captain would row and thestoker would pedal. Some sort of quick-release crank arms would be nice be-cause a rider would probably not wantthe pedals under him while rowing aloneon flat ground. I also considered a stair-climber-type lever-drive system inte-grated into the jackshaft for climbing,but I think the added weight would beprohibitive.

ClosingI am 37 years old and in average

physical condition. The various resultsand conclusions given are the result of

very informal testing and observationsmade by me during a couple hundredkilometers of test riding the vehicle.

Speeds were recorded on an inexpen-sive cycle-computer, calibrated to mymeasured wheel diameter. My purposewas merely to test the feasibility of thedesign and get a rough estimate of its ca-pabilities. The test vehicle's perform-ance surpassed my expectations. Ibelieve I can safely say that althoughpower-rowing may not set new top-speedrecords, very high average speeds formedium-duration rides will likely result.

I think the time has come for row-bike technology with its total-body work-out benefits and its intensely enjoyableride. For the image-conscious, the ma-chine has very good aesthetic qualities.The compact, long-wheel-base recum-bent chassis is beautifully suited to row-ing and its look will be that of ahigh-tech piece of exercise equipment onwheels.

The patent issued January 25, 1994,on my power-rowing mechanism, whichcould be adapted to other types ofH.P.Vs as well. I hope to market mycomplete vehicle, a kit, or possibly justthe plans at first to raise capital. I'd liketo see my land rowing vehicles helpbring about more widespread popularityof all H.P.Vs. Unfortunately, on mybudget, the world will have to be patient.I am still in the process of optimizing thedesign and drawing plans for a showable-quality prototype.

If I've failed to mention something ofinterest, you may write for more infor-mation. I welcome any serious ques-tions, comments, suggestions, orpropositions.

Dennis Schmidlin20798 W. S.R. 105Woodville, OH 43469

Dennis Schmidlin holds journeyman'scards as a millwright and as a machinerepairman, and is active with specialprojects at Modine Manufacturing Com-pany. With an engineering educationfrom Owens Technical College he enjoys,tennis, rowing and cycling along the ru-ral roads along the Portage River in NWOhio.

ReviewENCYCLEOPEDIA

the alternative buyers' guide toquality cycling around the world

Alan Davidson & Jim McGurnReviewed by Dave Wilson

This beautifully produced book - it ismore than a catalog - is being recom-mended by all who see it. It is more likea song of praise to cycles of all kinds,with HPVs and recumbents featuredprominently. Mike Burrows and RichardBallantine are contributors, and I suspectthat the superb photography owes some-thing to the perfection demanded byRichard Ballantine in Richards' UltimateBicycle Book. It is a large-format glossypaperback, the European equivalent ofthis sheet size, and the standard entry is atwo-page spread. It starts with surveysof the cycling scene by the three princi-pals. Then there are reviews of all typesof cycles other than standard "ten-speeds" and mountain bikes. There arerecumbent bicycles and tricycles, fold-ables, power-assisted, machines for peo-ple with handicaps, goods-carryingcycles, trailers and some components. Inninety pages there has to have been se-lectivity, and if you have the slightesttendency towards jingoism you will feelthat U.S. designs have been mainlypassed over. In fact, many of the designsappear to be fairly close copies of someU.S. predecessors. But Encycleopediadoesn't make any pretence of being encyclopedaic, and the authors, having put asmuch effort and as much money (onefinds it easy to believe them when theystate that they have lost a bundle on it)into the book's production and distribu-tion as they have, are surely entitled tochoose what they want to feature.

(Review concluded on p. 23).

Human Power vol. 11 no. 3, summer-fall 1994, p.19. --

AN OPEN LETTER TO THERULES COMMITTEE OF THE

IHPVAby Peter A. Sharp

The purpose of this paper is to con-Front four serious problems and to rec-ommend solutions. The problemsinclude the continued use of 1) high ele-vations, and 2) down slopes, for top-speed record attempts; 3) the placing ofaccumulators in the hybrid category; and4) obstructing the development of practi-cal HPVs. Currently, the rules of the IH-PVA are being updated by the RulesCommittee, and I was invited by Dennisraves, the coordinator, and a member ofthe Board, to contribute my input. I amgrateful for the opportunity. I respect allthe members of, and advisers to, theRules Committee (RC), and some areheroes of mine. But I am concerned thatthe RC (despite some notable dissenters)is about to make decisions that couldharm the IHPVA, or worse.

PROBLEMSHigh elevations

I request that the RC consider thenegative implications of using high ele-vations for top-speed record attempts.Using high altitudes to reduce aerody-namic drag is really no different than us-ing a pace car. It only looks legitimate.Low air density is equivalent to a signifi-cant increase in power. At31 m/s (70mph), at 2440 m (8,000 feet), where theair is about 20% less dense than at sealevel, it is worth about 138 watts (0.185hp) (the power required at sea level toovercome aerodynamic drag, minus thepower required at 2440 m). (I have usedthe figures for Matt Weaver's HPV, andfor air density, from his article in Cy-cling Science, Sept./Dec. 1991).

Would we accept as legitimate a topspeed record set in the (currently allow-able) vacuum on the moon, where the topspeed could exceed 90 m/s? Of coursenot. A slightly less improbable scenariowould be for someone with enough re-sources (like NASA) to set the recordusing a banked track, a space suit, and avery large low-pressure chamber (proba-bly a donut-shaped tunnel). This wouldcertainly be dramatic, but it would beirrelevant to real-life conditions. Only abit less extreme would be to use scubagear for breathing (or a native cyclist)and find the highest road in the extreme-altitude plateaus of Tibet. Recordsshould represent the HPV, not thelocation.

We want our records to reflect the re-alistic, meaningful, and incontrovertible

capabilities of our outstanding HPVs.That means near sea level. Also, highelevations favor members in some coun-tries, like the U.S., over other countrieswhere long, flat roads at high elevationsare not available. That is simply not fair.The use of high altitudes is largely re-sponsible for creating the problem offinding long-enough roads for record at-tempts. They should not have been per-mitted in the first place, and their useshould be discontinued. That wouldmake many more record sites available.The main problem with their use is thatthey are deceptive. Just as a balloon willexpand at high elevations, high eleva-tions create artificially inflated records.

Down slopesThe IHPVA currently permits the use

of a "legal" 2/3% down slope for top-speed record runs. The reason is to makeit easier to find long roads (at high alti-tudes) for record attempts. The RC isalready considering the use of a 1%down slope, and might permit it some-time in the future. That solution wouldbe a slippery slope. Steeper down slopeswould produce higher speeds, thus re-quiring longer runs, which would requiresteeper down slopes, and so on. Downslopes provide a large increase in power.At what point would we have a Soap BoxDerby with pedals? A lot sooner thanyou might think.

Each mile (1.609 km, 5,280 ft.) ofrun, using a 1% down slope, for a 91-kg(200 lb.) HPV/rider combination, stores(5,280)(.01)(200) = 10,560 ft-lb (14.3 kJ)of gravitational potential energy. There-for, a 5.1-km (3.2-mile) run (a low esti-mate), which would be required forreaching 31 m/s (70 mph), would store(10,560)(3.2) = 33,792 ft-lb (45.8 kJ).This is equal to descending a hill almostas high as a 17-story building ((51.5 m,168.96 feet). The faster an HPV goes,the faster it is descending, and the morepower it gains from a given down slope.Heavier HPVs (like tandems) gain morepower because more weight is descend-ing. 1 hp is equal to 746 watts or 33,000ft-lb per minute. At 31 m/s (70 mph),the amount of power derived from gravi-tational assist would be approximately(70/60)(10,560) / 33,000 = 0.37 hp (276watts). At 31 m/s (70 mph), a currentlylegal 2/3% down slope would store 2/3of that total (30.542 kJ, 22,528 ft-lb) andproduce 2/3 of that power (184 watts,0.247 hp). This last figure of approxi-mately 1/4 hp was recently pointed outby Andrew Letton, a member of the RCand the Board. It is in direct violation ofthe power rule: "Vehicles must be driven

solely by human power" (3.1.1). Gravitypower is not human power. (It could behuman power, but only if were storedhuman power or accumulated humanpower, neither of which is permitted.)

The IHPVA's use of net down slopesis based on a fantasy physics peculiar tothe IHPVA: the denial that gravitationalpotential energy storage is a form of en-ergy storage. The use of down slopesrequires the storage of large amounts ofgravitational potential energy in the massof the vehicle and rider. That turns theentire HPV/rider combination into an en-ergy storage device.

The IHPVA has been using downslopes, and therefor energy storage, formany years to set top-speed records. Butthe use of any net down slope whatsoeveris in direct violation of the "no storedenergy" rule. That rule is absolute - noexceptions. "No device which stores en-ergy... may be used in any event....""...this means absolutely no... potential...energy storage at the start" (3.1.2). Thatmeans no gravitational potential energystorage. It is not possible to use a netdown slope while excluding stored en-ergy. Admittedly, that rule was poorlywritten, since all HPVs inevitably storeor accumulate energy in a variety ofways. But the use of down slopes is,without doubt, prohibited by that rule.The rule permitting the use of a 2/3%down slope (3.3.1) directly contradictsthe rule prohibiting any stored energy(3.1.2), and the power rule (3.1.1).

The use of stored energy (but not ac-cumulated energy) defines an HPV as ahybrid vehicle. The use of a net downslope turns any top-speed-record HPVinto a hybrid vehicle. Consequently, alltop-speed records, since the first use ofdown slopes, have been set by hybrid ve-hicles. At present. the IHPVA has notop-speed record for HPVs. The "record"applies only to hybrid vehicles. Anyother record set using a net down slopeof any amount is also invalid. The rulesallow a competitor to use a 2/3% downslope, but if he uses it, his record doesnot count. That is, of course, extremelymisleading and unfair to the competitors.

If the RC claims that a down slope isa legitimate exception to the "no storedenergy" rule, then it will establish theprinciple that energy may be stored inorder to make more record sites avail-able. It would also establish the princi-ple, by implication, that there is no realdifference between an HPV and a hybridvehicle (an HPV using stored energy). Icertainly hope that the RC will not estab-lish those principles. There are bettersolutions.

p.20 Human Power vol. 11 no. 3, summer-fall, 1994

But competitors should not be usingeither down slopes or high altitudes. At70 mph, the approximate power to bederived from the combination of an alti-tude of 8,000 feet (0.185 hp) and a 2/3%down slope (0.247 hp) is 0.43 hp (320watts). That is a very large amount ofextra power, considering that the rider'smaximum output at that speed, near theend of his anaerobic sprint, would bearound 895 watts (1.2 hp) (down from apeak of about 1100 watts, 1.5 hp). Itamounts to a 36% increase in power, orroughly a 1/3 increase in power at 70mph.

Besides the fact that the use of downslopes invalidates the records, the use ofall this extra power is deceptive. In prin-ciple, it is no different than secretly usingan electric power assist. The generalpublic and the media have no idea thatthis much hidden power is permitted bythe IHPVA. They trust that the IHPVAis above reproach as the official sanc-tioning organization for HPV world re-cords. No record is worth risking thereputation of the IHPVA. That reputa-tion is now at risk.

AccumulatorsThe RC may ban the use of accumula-

tors from all records and races - evenfrom the road races where accumulatorsare currently legal, and have been for thelast ten years. The RC may place accu-mulators strictly in the hybrid category.

Besides the hypocrisy of this decision,it would be totally arbitrary and regres-sive. There is no justification whatso-ever for classifying a human-energyaccumulator as a hybrid device if the ac-cumulated energy is produced on boardby the rider and is not accumulated priorto the intended route or purpose as de-fined by the rules. There are clear andmeaningful differences between the useof an accumulator and the use of storedenergy. Regenerative braking and pre-generative pedaling are entirely legiti-mate ways to increase the efficiency ofHPVs. Accumulators are completelyconsistent with the physics and functionsof bicycles, just as they are for othertypes of vehicles.

An accumulator would increase theefficiency of an HPV under most circum-stances. Banning accumulators wouldactually require HPVs to be less efficientthan they could be. That would be a se-vere restriction which would show a fla-grant disregard for the values of theIHPVA. "The spirit of these rules is toavoid inhibiting design innovation by notestablishing unnecessary restrictions"(2.0).

I recommended, in my article on ac-cumulators (HP, vol. 10, no. 3, 1993)that the time limit for charging should beset at 1 minute. An accumulator for atop-speed-record attempt would becharged at a rate of about 375 watts, 1/2hp, so as to stay within the aerobic limitof the rider and to avoid exhaustion priorto beginning the run. That would be ap-proximately 33,000 / 2 = 16,500 ft-lb(22.4 kJ). By permitting the use of a2/3% down slope for a 70-mph recordattempt, the IHPVA already permits farmore energy to be stored (22.528 ft-lb)than what I have recommended as thelegal limit for accumulation!

As I mentioned in my article on accu-mulators, I favor the use of vacuums in-side tubes with pistons. Suchaccumulators are gravity devices. Theylift the atmosphere an infinitesimalamount. What they store is gravitationalpotential energy, the same form of en-ergy as a down slope. But whereas usingan accumulator would make a clearstatement that the HPV is deliberatelyusing that extra energy, a down slope(and a high altitude) serve to disguise allthat extra energy - and a lot more of it aswell.

What is the equivalent total of storedenergy? At 70 mph, the power equiva-lent to be derived from an 8,000 foot alti-tude (.185 hp) is almost exactly the sameas using a 1/2% down slope (.185 hp).So the total equivalent down slope, atsea level, would be 1/2% + 2/3% = 7/6%or 1.167%. The total equivalent, interms of stored energy, would be(7/6)(33,792) = 39,424 ft-lb. Comparedto using an accumulator, that amount ofenergy is about (39,424 / 16,500) = 2.39,or 239% as much energy as would bestored in an accumulator, using 1 minuteof pedaling.

Based on the evidence, it is obviouslynonsense to claim that down slopes (andhigh altitudes) are reasonable and legiti-mate while accumulators, using oneminute of preaccumulation, are not. Ifany "purist" still thinks that using an ac-cumulator might somehow be a form of"cheating", then that person has to firstexplain how the use of a net down slopes(and high altitudes) is not cheating.Good luck! Note carefully that if the RCinsists on unreasonably placing accumu-lators in a "hybrid" category, then that iswhere the top-speed records for the GoldRush and the Cheetah, and all other"down-slope records", must go as well.That hybrid category could get verycrowded.

Practical HPVsThere are wider and more serious im-

plications to consider as well. The mem-bers of the RC are aware of thelong-term consequences of the ICU's in-famous declaration - on Fools Day, April1, 1934 - that recumbent bicycles are notbicycles. Fundamental progress in bicy-cle technology was almost frozen untilthe IHPVA was founded 40 years later toremedy that kind of irrational obstruc-tionism. But now, in order to defend itsown obsolete notion of what a bicycle issupposed to be, the RC is about to makeexactly the same kind of absurd declara-tion: that accumulator-equipped bicyclesare not bicycles. This time, however,the consequences of freezing technologywould be far more serious.

Many members, including I myself,believe that advanced HPVs can becomea major component in the world's trans-portation mix, including North Americaand Europe, and that they can replaceautomobiles for the majority of trips.Half of round trips are less than 16 km,specifically 15 km in the U.S., and lessin Europe, according to a recent study byeconomists at the Lawrence BerkeleyLab. (The Christian Science Monitor,8/24/94). This replacement could haveenormous environmental, economic, andsocial benefits, especially if combinedwith public transit, more road access, andhigh-speed piggyback systems. But thenecessary technical advances will proba-bly require, at least, the combined use ofstreamlining, accumulators, and directwind and solar assist. I refer to suchpractical, super HPVs as "Ambient-Energy HPVs". (Paul MacCready hasreferred to this type of HPV as a "naturalenergy" HPV.) Some of them may alsorequire the use of power assist for hills asproposed by John Tetz, and promoted byPeter Ernst.

Both energy accumulation and windassist have always been part of the nor-mal operation of HPVs. There is no wayto avoid them. Simply moving, or ridingup any hill, accumulates energy, and anytailwind provides wind assist. In crosswinds, streamlined components providewind assist because they inevitably pro-duce lift and thrust. The critical choiceis whether to use human energy accumu-lation and wind assist most efficiently, orwhether to officially ban the energy theycould provide, and thereby to seriouslyhandicap the development of practicalHPVs. To opt for wasting that energywould be symptomatic of the energygluttony and energy waste that we takefor granted in North America.

Human Power vol.11 no.3, summer-fall, 1994, p.21... . .

To the extent that the RC fails to nur-ture, or continues to obstruct, the re-;earch and development of practicaliPVs, it will adversely affect environ-nental, economic, and social conditionsaround the world. In the eyes of futuregenerations, that decision would castshame on the IHPVA - especially so,since that negativism would have beenentirely unnecessary. The developmentAf advanced, practical HPVs should be;trongly encouraged by the IHPVA, notliscouraged or impeded, as at present.

The RC must not continue to requireadvanced, practical HPVs to conform tohe same overly narrow definition of anHPV that it now applies to conventionalracing HPVs. Racing and records are tobe used only as a means to an end -which is innovation, the evolution ofHPV technology. "In general it shall bethe intention of the IHPVA rules to avoiddefining what type of vehicle may enterindividual competitions, but to let thecompetition itself determine which typeof vehicle is superior by a normal evolu-ionary process" (2.0). Any elected orappointed official of the IHPVA who be-lieves that innovation should be subordi-nate to racing, is in the wrongorganization and is likely to do moreiarm than good.

SOLUTIONSI wish to recommend straightforward

solutions to these problems. There is noneed for conflict between "purists" and"practicalists". Both can be easily ac-commodated without imposing on theother. The IHPVA can comfortably em-body a wide diversity of opinions andtypes of HPV. Now is the time to makethat possible.

Four basic steps need to be taken: 1)Acknowledge that small-percentage netdown slopes store large amounts of en-ergy, that their use for record attemptswas a mistake, disallow them, set an alti-tude limit of 1,000 feet, and allow smallundulations in the surface of the road(plus or minus 1 meter); 2) Acknowl-edge the current top-speed record as offi-cial under the "special conditions" of thePre-'94 Rules, and establish a newPost-'94 Record; 3) Acknowledge thathuman energy accumulation and windassist are valuable energy resources, andthat they should be developed to the full-est extent possible for the benefit ofpractical HPVs; and 4) Establish an am-bient energy class, with separate and dif-ferent records and events - so as toencourage practical innovations whilevoiding conflicts with traditional racingnd records.

The ambient-energy class would per-mit streamlining, accumulators, and di-rect wind and solar assist. It would limithuman energy accumulation to 1 minute,allow wind speeds for its own records upto 5 meters per sec. (11 mph), limit vehi-cle widths to 1 meter, and prohibit theuse of net down slopes, high altitudes,and energy prestorage. Ambient-energyevents would be designed and updated toencourage innovative solutions to spe-cific problems. That way, the develop-ment of practical HPVs would not in anyway interfere with the current recordsand race events.

Current HPVs would be classified asgold-class HPVs (in honor of the GoldRush). The IHPVA's top-speed recordwould not be available to ambient-energyHPVs. That record would be reservedfor gold-class HPVs. However, theambient-energy-class records and eventswould be open to all gold-class HPVswho chose to participate, thus providingmore opportunities for competition. (Anadditional class with special events couldbe used to encourage the research anddevelopment of power-assisted HPVs.) Ihave submitted a preliminary outline ofthe proposed classes to the RC and theboard.

Please note that a failure to establishan ambient-energy class would probablyforce our "practicalists" to create a com-peting organization. That organization,using limited accumulators and limitedwind assist, could legitimately break allof the IHPVA's records, thus leaving theIHPVA with no records, few incentives,and little purpose. From that perspec-tive, an ambient-energy class would beexcellent insurance against competingorganizations, since our own memberswould remain at the leading edge ofpractical HPV technology.

It is very important that the buildersof the superb HPVs that have set the top-speed records should not be faulted orpenalized. They conformed to the rules,and triumphed. Only the rules were atfault. The current top-speed recordwould remain as official under the spe-cial conditions of the Pre-'94 Rules. Butwe would recognize the "Post-'94 Re-cord", under the fully legitimate andmore difficult conditions of the Post-'94Rules, as the superior record.

Anyone who proposes a different so-lution must be careful not to destroy theofficial record, and unfairly penalize therecord holders. We can still assume thatthe use of down slopes (and high alti-tudes) was an honest mistake, an over-sight, and not a deliberate attempt tocircumvent the "no stored energy" rule.

But if the RC were to continue to insiston the legitimacy of down slopes, thenthe record would become a deliberateviolation of the "no stored energy" rule, adeception of the public, and a disgrace.Incidentally, I would like to know whichHPV would presently hold the Post-'94Record, and what is its record speed?How fast can a current HPV really gowithout hidden sources of power? MattWeaver's calculations indicate that aPost-'94 Record could still be higher thanthe Pre-'94 Record, even without thosehidden sources of power.

For members who still want to usedown slopes to go faster, I recommendthat we establish a "Gravity Derby".Matt Weaver has calculated that a 6%down slope, without pedaling, could pro-vide speeds in excess of 100 mph, and a20% down slope could provide speeds inexcess of 200 mph. Pedaling would beused only to ride 1p to the starting line,where each HPV's drive mechanismwould be temporarily disabled (by tyingthe chain). All HPVs would carry thesame weight. This competition wouldreally be a coast-down test to comparethe aerodynamic efficiencies of ourHPVs. Owner/builders could demon-strate the speed potential of their designswithout having to use a professional cali-ber rider. We could learn a great dealfrom this event. Of course, for the safetyof our competitors, we would appropri-ately limit the slope and the distance foracceleration, and the consequent speeds.

The basic ideas of accumulators,ambient-(natural)- energy vehicles, andseparate classes were all proposed origi-nally by our esteemed InternationalPresident, Paul MacCready. Now is thetime to implement his ideas and recom-mendations. On behalf of the member-ship at large, I call upon the RulesCommittee to protect the credibility andintegrity of the IHPVA, and to set acourse toward a truly innovative future.

Peter A. Sharp, 2786 Bellaire Pl.Oakland, CA 94601

(Editorial note: the IHPVA slope andwind limits came, I believe, from an at-tempt to keep continuity of the recordsafter the Ontario Motor Speedway inCalifornia, where early IHPVA raceswere held, was demolished.

The European and British HPV clubsare as unhappy as Peter Sharp over theuse of high-altitude roadways, which arenot available elsewhere in the westernworld. Dave Wilson)

p.22 Human Power vol. 11 no. 3, summer-fall, 1994. _~~~~~~Y

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