HUMAN POWER TECHNICAL JOURNAL OF THE IHPVA NUMBER 50, SPRING 2000 Summaries of articles in this issue; mast . 2 Contributions to Human Power . 2 Articles On the efficiency of bicycle chain drives James B. Spicer and others . 3 Offset rims reduce the amount of dish Vernon Forbes . 10 Rolling resistance of bicycle tyres John Lafford . 14 Note on John Lafford’s paper and spreadsheet Jim Papadopoulos . 15 Reply to Jim Papadopoulos John Lafford . 18 Technical notes Power requirements for laid-back recumbents Bert Hoge and Jeroen Schasfoort in HPV nieuws Report and comment by Dave Wilson . 18 My propeller theory E. Eugene Larrabee . 20 Reviews Feet on!: pedal-powered museum exhibit Michael Eliasohn . 21 Human power: the forgotten energy Arnfried Schmitz, reviewed by Dave Wilson. 22 Editorial Cycle Vision, Ronald van Waveren . 23 Letters Number 50 Update, Anil Rajvanshi . 14 Supplement to velocar variations, Arnfried Schmitz. 22 Spring 2000 $5.50 Kudos, Chet Kyle . 23 On the efficiency of bicycle chain drives James B. Spicer,* Christopher J.K. Richardson, Michael J. Ehrlich and Johanna R. Bernstein HUMAN POWER The Johns Hopkins University, Baltimore, Maryland 21218 Number 50 Spring 2000 $5.50/IHPVA members, $4.00 Masahiko Fukuda and Masao Terada Shimano Inc., Product Engineering Division, Sakai Osaka 590-77 IN THIS ISSUE beautifully produced Netherlands HUMAN POWER counterpart to Human Power: HPV Bicycle chain transmissions nieuws. They showed, by testing a range ABSTRACT is the technical journal of the Jim Spicer and his associates at Johns of Dutch recumbent bikes, that the The efficiencies of bicycle drive International Human Powered Vehicle Hopkins have written a paper that will aerodynamic drag decreases as the angle Association change minds, and design directions, on trains have been studied to understand of reclining increases. Number 50, Spring 2000 HPV transmissions. To give just one energy-loss mechanisms in these sys- Editor example: the losses associated with small My propeller theory tems. An analytical study of frictional David Gordon Wilson sprockets on the rear wheel make “mid- Gene Larrabee, whom Human Power energy loss along with a series of named “Mr. Propeller” many years ago, 21 Winthrop Street drives” or countershaft gears suddenly summarizes his propeller theories and the experimental efficiency measurements Winchester, MA 01890-2851 USA attractive, and possibly hub gears too. developments that have resulted from of derailleur-type chain-drive systems [email protected] They also find that chain lubrication doesn’t seem to reduce losses: that will be them. He also pays tribute to those who under a range of power, speed and Associate editors even more controversial. (Your editor has inspired him and gave him the basic lubrication conditions are given to Toshio Kataoka, Japan high confidence in the data: he asked Chet theories on which he built. Was Isaac identify loss mechanisms. These mea- Newton the first to state that we all stand 1-7-2-818 Hiranomiya-Machi Kyle, IHPVA founder and one of the surements of mechanical efficiency are Hirano-ku, Osaka-shi, Japan 547-0046 foremost researchers in bicycle perfor- on the shoulders of giants? compared to infrared measurements [email protected] mance in the world, to look at them before Feet-on! review publication. He had done a proprietary Mike Eliasohn writes a delightful review performed during drive operation that Theodor Schmidt, Europe study on the same topic, and has produced of what sounds to have been an equally show the heating of drive components Ortbühlweg 44 broadly similar results.) delightful and truly interactive museum resulting from frictional losses. The CH-3612 Steffisburg, Switzerland Offset rims exhibit devoted to human power. [email protected] results of this study indicate that chain Vernon Forbes gives us another of his Human power: the forgotten energy tension and sprocket size primarily careful studies of spoked-wheel construc- Your editor reviews a small fascinating Philip Thiel, Watercraft determine chain-drive efficiency. 4720 - 7th Avenue, NE tion incorporating derailleur clusters or book by Arnfried Schmitz, already well- Seattle, WA 98105 USA brake disks that cause the wheel to be known in these pages, on the origins of “dished” (spoked asymmetrically). He HPVs in France, on the characters of the INTRODUCTION Production protagonists, and (very modestly) on his shows that the use of rims that have off- When this study was performed, it Fig. 1. Experimental schematic of test stand showing elements of the drive JS Design & JW Stephens center spoke holes brings about a consid- own part in the revival of interest in these was hoped that through identification assembly erable reduction in the difference in spoke wonderful vehicles. IHPVA of the loss mechanisms primarily tensions that otherwise makes highly Editorial from the Netherlands Paul MacCready, Honorary president responsible for limiting the efficiency tion (Tordion 1996). Since some of these tions (Juden 1997). Without detailed Chris Broome, USA, Chair dished wheels prone to spoke failure and Ronald van Waveren, chair of the occasionally to collapse. of bicycle chain drives, methods for are dynamic effects, the work presented analysis of Keller’s results, it appears Ben Wichers Schreuer, The Netherlands, Netherlands HPV association, writes a Vice-chair, Rolling resistance guest editorial about the astonishing improving efficiency could be realized here was conducted on chain drives that they do not wholly support the idea numbers of recumbent bicycles and HPVs Open, Secretary/treasurer John Lafford has tested, on equipment by eliminating or decreasing the vari- during operation. that the efficiency is governed by fric- of his own design and construction, a in the Netherlands, and in particular about ous losses. Unfortunately, as will be Hollingworth and Hills (1986a) per- tion. Work by Kidd, Loch and Reuben Publisher prodigious number of bicycle tires, mostly the annual celebration known as “Cycle shown, definitive identification of these formed a detailed theoretical and (1998) has attempted to quantify drive IHPVA of a size particularly suited to the front Vision.” Through delays in our publication PO Box 1307 wheels of recumbent bikes. He measured we are too late to encourage you to visit mechanisms has not been successful. experimental study of chain contact efficiency in relation to models of drive- San Luis Obispo, CA 93406-1307 USA rolling resistance and power loss over a this exciting event this year, but we hope Rather, the results provide information forces during link articulation in heavy- train performance based on chain con- Phone: +805-545-9003; [email protected] range of speeds and inflation pressures. that you will do so next year…. on the efficiency of chain drives and, at duty chain drives and used these tact forces. While static measurements Jim Papadopoulos wrote a commentary on Letters include kind words from Chet Human Power (ISSN 0898-6908) is pub- the same time, lead to conclusions results to calculate the theoretical effi- of these forces have agreed with mod- the results, and John Lafford responded, Kyle; comments by Anil Rajvanshi on the lished irregularly for the International eliminating those mechanisms that do ciency of chain drives assuming that els, efficiency-measurement results all in this issue. publication of his article on rickshaws in not dominate efficiency. We hope that frictional losses primarily affected effi- have not appeared in the literature Human Powered Vehicle Association, a Power requirements for the last issue (Human Power 49); and non-profit organization dedicated to pro- unfaired laid-back recumbents comments and corrections by Arnfried the results here contribute to the over- ciency (Hollingworth and Hills, 1986b). (Kidd et al. 1996). moting improvement, innovation and cre- Bert Hoge and Jeroen Schasfoort wrote a Schmitz on his article “Velocar variations”, all body of work on chain-drive effi- They found that the efficiency of the In this work, the efficiencies of bicy- ativity in the use of human power gener- short but valuable technical note in the also in the last issue. ciency and also to the on-going discus- chain drive should increase with the cle chain drives are investigated both ally, and especially in the design and sion of this topic (Cameron 1999; Wil- number of sprocket teeth on each of experimentally and theoretically to iso- development of human-powered vehicles. CONTRIBUTIONS TO HUMAN POWER son 1999). the driver and driven sprockets. Unfor- late factors associated with loss in Material in Human Power is copyrighted The editor and associate editors (you may choose with whom to correspond) welcome Even though design of chain drives is tunately, no experimental results were these systems. A computer-controlled by the IHPVA. Unless copyrighted also by contributions to Human Power. They should be of long-term technical interest. News and fairly well-understood (Vogwell 1994) given to verify their models. drive-train-testing system was designed the author(s), complete articles or repre- similar items should go to HPV News or to your local equivalent. Contributions should be the factors affecting efficiency have In the work by Keller (1983) measure- to measure the performance of the sentative excerpts may be published else- understandable by any English-speaker in any part of the world: units should be in S.I. been considered only in passing as part ments of efficiency were made for dif- chain, chain ring and rear cassette in a where if full credit is given prominently to (with local units optional), and the use of local expressions such as “two-by-fours” should the author(s) and the IHPVA. Individual be either avoided or explained. Ask the editor for the contributor’s guide (available in of the design process. Generally design ferent transmission systems (derailleur, derailleur-type system. This system was subscriptions and individual issues are paper, e-mail and pdf formats). Many contributions are sent out for review by specialists.