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Bicycle crank makes quantum leap

Promising engineering produces bicycle crank without no power "dead spot".
"... While conventional paired bicycle cranksets have been around since the dawn of the bicycle and they work pretty well. However they do have one fundamental weakness. During the rotation cycle of a conventional crankset there is a point when the rider is not producing any power. On an upright this is when the cranks are straight up and down. This point varies widely on recumbents. Rotor cranks are the latest in a long line of products designed to eliminate that "dead spot". Rotors use a system of cams to make sure that your cranks never become aligned in a way that doesn't allow you to produce any power. Your feet will be at the one o'clock and six o'clock position when they would be at twelve and six on conventional cranks."


Full article:

 http://www.bentrideronline.com/2004Feb/rotor_cranks.htm

other, lower-tech means to this end 05.Jul.2004 10:18

zero_sum0g

elliptical cranks have been around for a while. Shimano's "BioPace" line is one example. They are definitely more relaxing, on a long ride, than the typical round cranks.

encyclopedia velopedia 05.Jul.2004 21:40

glassguy

I have a biopace crank on my old cannondale road bike, which I got in the 80's. As I recall, they dissapeared after a year or two of production because index shifting came out, and the elliptical chainrings were incompatable with index shifting. Given the choice,I'd take index shifting over the biopace.
This device sounds like the old Excel Bio-Cam, which I think I remember from the '70's. I have a vague recollection of Lon Haldeman riding one in Race Across America, kicking everyones ass by a huge margin, and the powers-that-be in the world of bike racing banned it after that.
Anyone got a better memory than me for this stuff?

foo foo toys 06.Jul.2004 00:09

oh boy

these seem like very expensive overkill toys...but having said that...anyone around here actually trial tested them?....how do they hold up...they're definitely different than biopace, based on study of text and graphics on the website...

Offer you can't refuse 06.Jul.2004 18:44

bicyclerider

I have a home made elliptical crank/chainring that I will give to you if you want to experiment. If you've anything to trade that would be OK too. If you want to buy it, well, this is not a commercial site...

I made it in around 1980 out of an old street sign. I used it for years on an old KHS and it worked well until the frame broke just when I needed it the most, but that's another story.

On that bike, the front derailer would change between this elliptical ring and the regular round one and the rear derailer worked pretty normally. I found it very useful climbing hills, but the rhythm was a little different between the two. This was the second attempt -- the first attempt was too extreme and not useful.

if interested send mail to  jimtjimt@hotmail.com

I had Biopace and Deore shifters 07.Jul.2004 16:40

SKiDmark

On my 1st mountain bike in 1987 so that's SIS(index shifting) and Biopace at the same time. It definitely got rid of the *dead spot* but for some reason it would cause tire slippage off-road while in the granny gear. Most people with biopace back then would use a round ring for the granny gear. I think for the most part toeclips or clipless pedals and shoes get rid of the flat spot. Cross training with a fixed gear bike will get rid of any *dead spot* you are experiencing too. It will help you develop a "Round Pedaling Technique" and get rid of the *dead spot*. Most people who ride bikes only push down on the downstroke when they pedal and do not pull up as their foot comes around. That is your *dead spot*. On a recumbent this *dead spot* would be when the pedals are at 3 and 9 o'clock, which is one leg straight and one leg bent just like 12 and 6 on a regular bike. It seems to me that placing the cranks at 1 and 6 would just feel like cranks with a twisted spindle and would upset your pedaling rhythym so much that no benefit from the relief of this so-called *dead spot* would result.

For more info on Biopace, Fixed Gears, and Round Pedaling Technique check out www.sheldonbrown.com

Been there........ 08.Jul.2004 13:43

Jo Routens

Shimano did this in the 1980's with a dropped pedal whose bearing sat inside a specially shaped crank arm; they were called "Dyna Drive." I and a number of other people including former pro rider Alexi Grewal loved these things; the crummy seals on the bearings and need for non-standard toe clips doomed them. Too bad; they truly did remove a dead spot from pedalling. I could climb any hill in a 2 tooth higher gear with them than with either standard clip/strap pedals or the clipless ones I currently use. Shimano did this by a simple rearranging of parts that were already there and it would be real nice to see them reintroduced. There is NO need use a bucket o'bolts solution to this!

these work 13.Jul.2004 01:10

arthropod

i've actually seen these cranks and have spoken with a guy who uses these. this was in minneapolis, i worked in a recumbent specialty shop. i just moved back to portland. i don't miss minneapolis. anyways, recumbent riders generally have more money to throw around on high tech shit that gives you 8% more efficiency(!)and shaves seconds off your time! recumbents ain't cheap.

Pedalling Dead Point 26.Jul.2004 03:35

Al Guthmann aushunt@bigpond.com

I have been thinking about the dead point problem for years and have finally come up with a real solution. No eliptical chainwheel, no cams, no rotor cranks, just plain smooth pedalling without the dead point! Yea, this could change cycling for ever. Who says lateral thinking is a waste of time? Now, I just have to find a company to make the damn thing. Any ideas?

K.I.S.S. 04.Mar.2006 22:33

RedDeMartini

Hey, the essence of the bicycle is simplicity, years of fixing and riding make me recoil with horror at the "progress" that might be achieved with "a series of cams". Just learn to spin and appreciate the elegance of simple design, if we liked complicated we would all be riding full suspension, disc braked, recumbents.

K.I.S.S. 08.Mar.2006 06:49

RedDeMartini

Hey, the essence of the bicycle is simplicity, years of fixing and riding make me recoil with horror at the "progress" that might be achieved with "a series of cams". Just learn to spin and appreciate the elegance of simple design, if we liked complicated we would all be riding full suspension, disc braked, recumbents.

I love it! 24.Apr.2007 00:43

maurice - from the Netherlands

I'v have a mountain bike from the eighties with a 48 teeth shimano biopace. If you like it, I think, denpends on whether you generally prefer a slow or fast pedalling pace/cadence. Rcae bike cyclists are often slim build and prefer a high pedalling frequency. I'm average build (185 lbs) and prefer a rather slow pedalling pace with high torque (so I'm not a slow cyclist :-)). Now, when you mostly use your highest gears and stay on you saddle you sort of experience a pumping action on your pedals. Its like you have to pump your way forward; very tiring. You might argue I should shift down, however with the biopace it feels more like smooth continuous efficient action. You just want to go faster and faster.
Biopace are perfect for me, however some other eliptical gears are far more eliptical which is alittle bit too much. The biopace which is just a little bit off round which just subtlely smoothes out your medium to lower frequency high torque pedalling pace.