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Roy_Rada
Starting Member

USA
11 Posts

Posted - 11/08/2011 :  13:03:06  Show Profile  Visit Roy_Rada's Homepage  Reply with Quote
I have a question for all you other designers out there. Our team has been struggling to build a front wheel drive and front wheel steering bike. As you can imagine this creates a twist chain issue when the rider is turning.

One method that we have considered using to avoid this issue involves using a constant velocity joint in a gear reduction setup to allow for the chain running to the front wheel to rotate with the wheel. We are not sure if this idea is practical, and we do not want to continue with our manufacturing until we have finalized a reasonable solution to the twist chain problem.

Do any other teams plan to use a bike that has both front wheel drive and steering? This should help reduce weight and other issues involved with running a long chain all the way from the crank to the back wheel.

Look forward to hearing opinions!

Speedy
recumbent guru

USA
721 Posts

Posted - 11/08/2011 :  13:34:07  Show Profile  Reply with Quote
a simple twist chain works fine
depending on the length between sprocket centers you may lose some shifting range i.e. only the middle of the cluster is useable
a work around is an internal shifting hub
or another example
7 speed spacers and chains on thinner 9 speed cogs

part of ASME judging is on technology application
try what is on your mind
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Roy_Rada
Starting Member

USA
11 Posts

Posted - 11/08/2011 :  14:07:37  Show Profile  Visit Roy_Rada's Homepage  Reply with Quote
Thanks for the response speedy! I found this cool German manufacturer http://www.zoxbikes.com/ which makes bikes that simply utilize the twist chain. Has anyone else tried building a bike like this?
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purplepeopledesign
recumbent guru

Canada
583 Posts

Posted - 11/08/2011 :  18:37:49  Show Profile  Reply with Quote
quote:
Originally posted by Roy_Rada

Thanks for the response speedy! I found this cool German manufacturer http://www.zoxbikes.com/ which makes bikes that simply utilize the twist chain. Has anyone else tried building a bike like this?



Just going through my old pictures from pre-1996, there are examples by Varna, Ollinger, my mentor Paul Smith, et al. Many current designs are also twist FWD.

:)ensen.

Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/08/2011 :  21:55:52  Show Profile  Reply with Quote
Roy

The Toronto team built 2 bikes with front wheel drive, front wheel steering design, using the twist chain. It works really well (we won ASME east last year with one of the bikes).

2 issues you have to take care of:

1) make sure the chain cannot fall off any of the sprokets. When the wheel turns and there are bumps, the chain can easily fall off. Chain guards (similar to downhill bikes) can easily handle the chain.

2) Keep the tension (driving) side of the chain as parallel as possible to the steering axis. You do not want to affect the steering with your pedaling forces. I am not sure what the max angle can be between the power side of the chain and the steering axis, we always stayed under 10 degrees.

we will build our third bike also with twist chain design for the 2012 races.

cheers
Where is your team from?

Victor
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W Hilgenberg
recumbent enthusiast

USA
283 Posts

Posted - 11/08/2011 :  22:15:04  Show Profile  Reply with Quote
We (Cal Poly HPV Team) have built many different configurations of bikes over the years and have found that chain twist FWD is probably the most elegant design. We have also built two bikes with a FWD and a CV joint and while they function well as a drivetrain, the packaging requirements for the u-joint make it hard to put anywhere and keep the bike compact. But that could also just be the fact that our designs were a bit bulky and in my opinion, a fair bit underthought. For the record we have also built a FWD rear wheel steer recumbent and that was, to say the least, interesting. It was a beautiful solution to the drivetrain problem but it was very difficult to ride any faster than 23 mph and was a handful under that especially if it was mounted in the fairing. I still love to take it out and ride it sometimes. . .

Basically what it all comes down to is to build the smallest and most reliable bike possible, go with a FWD chain twist. It's pretty much bulletproof.
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/08/2011 :  22:24:09  Show Profile  Reply with Quote
A few pics

Our 2010 bike, 63mph top speed at Battle Mountain, could deal with tight ASME course:

http://www.recumbents.com/wisil/whpsc2010/images/larrington__tuesday/4990291259_1d647cd153_o.jpg

http://www.flickr.com/photos/sdelc/4987935662/

http://www.flickr.com/photos/sdelc/4987934950/

Our 2011 bike, 73mph, could also deal with utility ASME course
http://www.flickr.com/photos/mr_larrington/6138865771/

the chain you see would go around the front chainring. The chain going down to the wheel is on the opposite side (left hand), requiring a reverse freewheel on the wheel. The whole package is very narrow, allowing a Q-factor of 100mm and still being able to steer enough for ASME.

couple more twist chain solutions, all from bikes competing at Battle Mountain, which means very little steering, but very good efficiency...

http://www.recumbents.com/wisil/whpsc2010/images/larrington__tuesday/4990893170_9eee777e91_o.jpg

http://www.flickr.com/photos/mr_larrington/6143100558/

http://www.flickr.com/photos/mr_larrington/6142549131/

http://www.flickr.com/photos/mr_larrington/6142549631/

As you can see, to be able to steer a lot, the wheel must be small (we use 406 size wheel). Also, people with short legs might have issues.

Roy, are you from University of Central Florida? They had very nice trikes every year, would be cool if you switch to bikes...

cheers

Victor
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OpusthePoet
recumbent guru

USA
678 Posts

Posted - 11/09/2011 :  14:57:56  Show Profile  Visit OpusthePoet's Homepage  Reply with Quote
quote:
Originally posted by Roy_Rada

I have a question for all you other designers out there. Our team has been struggling to build a front wheel drive and front wheel steering bike. As you can imagine this creates a twist chain issue when the rider is turning.

One method that we have considered using to avoid this issue involves using a constant velocity joint in a gear reduction setup to allow for the chain running to the front wheel to rotate with the wheel. We are not sure if this idea is practical, and we do not want to continue with our manufacturing until we have finalized a reasonable solution to the twist chain problem.

Do any other teams plan to use a bike that has both front wheel drive and steering? This should help reduce weight and other issues involved with running a long chain all the way from the crank to the back wheel.

Look forward to hearing opinions!

That CV joint from a sprocket that's fixed to the frame/boom to a sprocket that's fixed to the fork is patented as a Stanton Hub. Just FYI.

Opus

My gas is up to $0.99 a burrito, $5.99 for premium and I'm only getting 10 miles to the regular burrito. Dang $0.99 burritos are smaller now.
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OpusthePoet
recumbent guru

USA
678 Posts

Posted - 11/09/2011 :  15:27:15  Show Profile  Visit OpusthePoet's Homepage  Reply with Quote
Also I have tried the FWD rear wheel steer trike on the drag trike. It's do-able but tricky. I got away with it because of limited steering lock. I have driven other rear wheel steered vehicles that were even more tricky in the form of taildragger aircraft. Rear steer vehicles without limited steering lock can get into a condition called a "ground loop" where the lateral acceleration on the rear wheels exceed the limits of traction and because the rear wheels steer the vehicle you can't unwind the steering to reduce the slip angle and get the back of the car rolling instead of sliding. The way around that is to have enough weight on the front wheel that pretty much no matter what the front wheel slides first, somewhere around 50% front weight on a delta trike, about 67% on a quad (normal car setup) with a lot of front roll stiffness.

Sorry, I used to build race cars and I get a bit geeky about chassis dynamics.

Opus

My gas is up to $0.99 a burrito, $5.99 for premium and I'm only getting 10 miles to the regular burrito. Dang $0.99 burritos are smaller now.
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sbocher
Starting Member

USA
11 Posts

Posted - 11/09/2011 :  18:53:11  Show Profile  Visit sbocher's Homepage  Reply with Quote
We're (UW-Madison) planning on experimenting with a universal joint front wheel drive vehicle. If the design is unreliable or too much of a weight penalty we'll just use the twist method. For either design we'll need a FWD fork. Are there any 135mm 20" forks available in the U.S.(preferably with a derailer hanger)? Or does everyone fabricate their own? The only ones I could find were raptobike and I think they are in the UK.

-Sean
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sean costin
human power supergeek

Lesotho
1972 Posts

Posted - 11/09/2011 :  19:24:36  Show Profile  Reply with Quote
You should contact Barcroft www.barcroftcycles.com
They might sell you one.

Sean
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JMvD
New Member

Netherlands
82 Posts

Posted - 11/10/2011 :  00:37:57  Show Profile  Visit JMvD's Homepage  Reply with Quote
quote:
Originally posted by sbocher

We're (UW-Madison) planning on experimenting with a universal joint front wheel drive vehicle. If the design is unreliable or too much of a weight penalty we'll just use the twist method. For either design we'll need a FWD fork. Are there any 135mm 20" forks available in the U.S.(preferably with a derailer hanger)? Or does everyone fabricate their own? The only ones I could find were raptobike and I think they are in the UK.

-Sean


The raptobike headquarters are in the Netherlands. The owner of raptobike ocassionally visits this forum.

cheers,

Jan-Marcel
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/10/2011 :  11:56:07  Show Profile  Reply with Quote
you can always order a rapto-bike fork. They are about 130$ and we had very good results with them, using one on our 2010 bike. They are strong and quite heavy, have deraileur and disk brake mounts. The offset is fixed however, so make sure the geometry works with your bike.

Victor
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Larry Lem
human power expert

South Sandwich Islands
2176 Posts

Posted - 11/10/2011 :  12:38:18  Show Profile  Reply with Quote
quote:
Originally posted by sean costin

You should contact Barcroft www.barcroftcycles.com
They might sell you one.

Sean



I wonder how Dana at BentUp Cycles farms out the work to build Barcroft bicycles now that he owns the company. Same supply chain?

Larry Lem
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sbocher
Starting Member

USA
11 Posts

Posted - 11/10/2011 :  14:03:44  Show Profile  Visit sbocher's Homepage  Reply with Quote
Thanks for the suggestions!
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Roy_Rada
Starting Member

USA
11 Posts

Posted - 11/10/2011 :  14:58:47  Show Profile  Visit Roy_Rada's Homepage  Reply with Quote
Wow! Thanks for all the great responses. I'm glad to see that others have had success with this twist chain design that we will be utilizing.

My team is from the University of Florida in Gainesville. I have spoken to some of the University of Central Florida team members. They have some nice designs, but I don't know what they're working on this year. Our school hasn't competed in I believe 8 years so all of our members are new and have never been to competition. We also don't have a faculty adviser so its a lot of independent research and swinging in the dark.

Thanks for the pictures Victor! That looks like a huge chain ring you use on all of the bikes. Do you use software to calculate your gearing set up or do you do it by hand?

In response to sboscher's question, our team constructed our own fork. It wasn't difficult to weld the fork using chromoly tubing, but I'm not sure if it will work properly. Looking forward to sharing pictures with you all soon.
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/10/2011 :  15:19:21  Show Profile  Reply with Quote
I built myself a excel table where i input the RPM range at the pedals, the gear combinations i have, and i get out the speeds i can achieve. This way i can tweak the gear ratio and gear steps for each event...although, it practice, it doesnt make as big of a difference as you think. In 2011 ASME, our gear shifter didnt really work, and the first gear was wayy to high, so everyone rode only in the first gear. We did pretty good...

I recommend you automate as much of the design as possible, excel and Matlab being my tools of choice. If you calculate anything twice, you might as well make a program that calculates it for you for any values...
There is a very good calculator at http://www.soulbikes.com/gears/ , but i wrote my own so i can get nice graphs for the tech report :D

Victor
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Dreamer
recumbent guru

USA
585 Posts

Posted - 11/10/2011 :  20:10:50  Show Profile  Reply with Quote
quote:
Also I have tried the FWD rear wheel steer trike on the drag trike.

Opus,
The rear steering problem is also one of basic physics which become increasingly critical as speed increases. (F = MA combined with the laws of centrifugal force.)
For any vehcile, if the headset is positioned behind the front wheel(s), a turn to the left will shift the direction of travel of the vehicle mass to the right. At slow speeds it's not a big deal but consider a mid-steer or reer stear traveling in a straight line at high speeds. The side force vector of the vehicle is zero, that is, there is no acceleration left or right. For a turn to be initiated the rear of the vehicle must first travel in the opposite direction and then nearly instantly shift direction to follow the front tire(s).
The first shift is easy to do and the resultand force is nearly the same as that of a front wheel steer vehicle only it's reacting in the opposite direction of travel. then it can get exciting. The mass reacting through the center of gravity and gaining momentum to the right must then decelerate to 0 and reaccelerate to vehicle speed along the line of travel to the left to complete the turn. This acceleration to the right, deceleration to 0 and reacceleration to the line of travel will occur in the same time it took the mass of the front wheel steer vehicle to accelerate to the left. At high speeds The stresses generated by this sudden acceleration of the mass in a direction opposite to the direction of travel and the resultant centrifigal force are tremendous and something is going to give.

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Roy_Rada
Starting Member

USA
11 Posts

Posted - 11/17/2011 :  15:45:45  Show Profile  Visit Roy_Rada's Homepage  Reply with Quote
Victor,

Our team is hoping to use a set up that consists of four gears with a gear reduction. After looking through some of your photos on flickr I found a bike using a similar design and I had a question about steering and shifting gears. Here is the picture I'm refering to:

http://www.flickr.com/photos/mr_larrington/6138180809/in/photostream/

Doesn't having the derailleur on the twist chain cause issues? I can't imagine that it would work very well, but I've never had the chance to try it out. Also I'm wondering if this set up severly reduces the bikes turning ability. Was the Varna Torso able to deal with the challenges in an ASME utility race?

Seems like the HPV team in Toronto is very succesful. I hope that someday down the road our team here at the University of Florida will be equally productive.

-Roy
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W Hilgenberg
recumbent enthusiast

USA
283 Posts

Posted - 11/17/2011 :  15:56:24  Show Profile  Reply with Quote
Of note, the Varna Torso trike is not an ASME bike. Therefore it doesn't have enough steering lock in order to compete in ASME.

Toronto built their bike up like so and it seemed to work rather well.

http://www.flickr.com/photos/mr_larrington/6138865771/in/photostream/
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/17/2011 :  17:34:26  Show Profile  Reply with Quote
Hello Roy

The deraileur can be put on either the twisting chain or the chain from the BottomBracket to the intermediate drive, they both work well. You have to make sure there is enough distance from the intermediate drive to the wheel to allow the twist chain to twist enough. The twist chain will also lengthen when twisted, so a deraileur is actually recommended on this chain.
Our first bike had the deraileur on the twist chain, our second on the non-twist chain, our third will probably have 2 deraileurs, 1 on each chain.

One issue we had with the deraileur on the twist chain is that, in the outer gears, the chain can rub the thigh of the rider, if the rider is very low on the bike. This can cause rather bloody thighs.

I recoment spending an afternoon and welding a trial frame together out of old forks and old bike parts. It is a lot of fun to play with and you get a much better sense for how much a chain can twist, and what are the issues.

Victor
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warren
human power expert

4664 Posts

Posted - 11/18/2011 :  09:31:45  Show Profile  Visit warren's Homepage  Reply with Quote
From: http://www.recumbents.com/wisil/foldracer/foldracer.htm



Works great. The only issue is wheel spin when sprinting from a dead stop.

-Warren.
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Victor Ragusila
recumbent enthusiast

Canada
347 Posts

Posted - 11/18/2011 :  10:18:20  Show Profile  Reply with Quote
wheel spin is not an issue, is a FEATURE! I personally love it. Makes one feel badass...

Victor
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Roy_Rada
Starting Member

USA
11 Posts

Posted - 12/27/2011 :  00:30:45  Show Profile  Visit Roy_Rada's Homepage  Reply with Quote
Hey everyone,

I know it has been a while since I posted this topic about FWD and front steering. Our team believes that we will go forth with a twist chain design for our drive train instead of our original cv joint construction.

However, I have done a lot of searching on the internet for twist chain designs/explanations because I do not fully understand how this system works.

If anyone has any resource that they know of (or if they would like to explain it), can you please share it here? It will be greatly beneficial to the advancement of this team's bike construction/design.
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Upright Mike
human power expert

USA
3254 Posts

Posted - 12/27/2011 :  10:50:39  Show Profile  Visit Upright Mike's Homepage  Reply with Quote
Simple bicycle gearing speed calculation...
(chainring / cassette) x wheel diameter x pi / 1056 x rpm = speed MPH

with step-up gear, mid-drive etc...
(chainring / middlegear1) x (middlegear2 / cassette) x wheel diameter x pi / 1056 x rpm = speed MPH

Explanation.....
substitute the number of teeth for chainring, cassette, middlegear1, middlegear2 in the above.

This may sound overly simple, but today's drivetrains can get really complicated, so...Chainring is at the pedals, cassette is the final gear turning with the wheel doing the driving, whether its front or rear wheel drive. Cassettes can be used as middlegear1 gears in front wheel drive designs such as the Varna. Thus there is more than one middlegear1 gear. The Varna does all its shifting on the first chain.

Easy trick to remember which is what...
(Chainring & middlegear1) share the same chain - the first chain at the pedals
(middlegear2 / cassette) share the same chain - the second chain going to the wheel.
middlegear2 contains more teeth than middlegear1 in order to "step-up" increase the overall gear ratio.

pi = 3.14159....(to a billion places)....... just input 3.14 for most calculations its sufficient, and won't change a thing.

wheel diameter is in inches, some common racing tire sizes diameters...
700 x 23c = 26.2 inch
650 x 23c = 24.5 inch
451 x 28c = 20.125 inch
406 x 28c = 18.5 inch

pedal cadence is rpm - about 60 to 80 rpm is normal for most "crusing speeds", about 100 to 110 rpm max for sprinting, though in a streamliner, a lower cadence like 100 rpm can make it easier to control. See other thread entitled "Discovery Channel" in WHPSC forum.

Edited by - Upright Mike on 12/27/2011 10:54:55
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Upright Mike
human power expert

USA
3254 Posts

Posted - 12/27/2011 :  11:11:22  Show Profile  Visit Upright Mike's Homepage  Reply with Quote
Some points about FWD Twist-chain.
1) the twisting part of the chain is aligned more or less with the fork - so that may the twisting forces are minimized. So this chain runs up and down. The closer the chain is to the fork axis, the less the steering moment thats inputted to the wheel. Constrast this to the Swing-Boom design described below. So the middrive or an idler should be close to the steer axis.
2) if you keep the final chain that drives the wheel on the right-hand side, which is a conventional drive, you can have your drive wheel free-wheel, meaning it turns without the chain spinning. I unfortunately have FWD with the twist chain on the left-side of the bike. The twisting part of the chain connects to a fixed gear that is always spinning when the wheel turns. This means my 2nd chain is always spinning as well, even when I'm coasting. Having a chain spin when there is no pedal forces on it, can lead to derailment problems.
3) More than likely, the twist chain will require some sort of tensioner on it, placed on its "return" side, which is the front part of the chain on a FWD with the chain running up and down. It's the part of the chain that runs down - this part of the chain is under less tension than the rear part of the chain which is pulling up and doing the work of turning the wheel. The tensioner keeps a fixed length twist chain on the gears better. On a Varna-style drivetrain (or my own similar design), when you shift the first chain, there can be a momentary lapse in tension on the 2nd chain which can cause it to "bunch-up" or derail easier if there is no tensioner in place to compensate.
4) The best FWD design with twist chain is the Varna-style. Of course, other bikes use this same type of design. All the shifting is done at the middrive1 gears. The two chains are on the same side, the right-side. Some of its good points. Its front wheel can freewheel without the 2nd twist chain having to keep moving when the rier stops pedaling. The front fork can be made narrower with only one cog, instead of multiple cogs located on the drive wheel. The "wider" components like the multi-speed cassette are located up in the wider part of the vehicle. The twist-chain section stays constant length, size, distance from all the other parts of the bike because its not being shifted around. Thus once you get it working correctly with the idler tension, etc, it doensn't need to be changed much.
5) Most bicycle chains have a built-in ability to twist, so there is not a big loss with a twist-chain system that some people might think. Every chain on a multi-speed road bike, mountain bike, etc runs a bit twisted when it is not on gears that aligned the same at the pedals and rear wheel. The few degrees of twist that a FWD twist chain does while the bicycle is turning may actually be LESS TWIST than on some mountain bikes and road bikes. and it will be doing it LESS OFTEN on the FWD drive, because its only twisting when the bike is turning, not when its going ahead straight. Many bikes lean when they are up to speed requiring even less turning of the front wheel, so even less time the chain needs to twist.
6) I'm not exactly sure how to describe this last point, but some designs, including mine, use a rather "large" final cog at the front wheel. Mine is constrained by my hub to be 26 tooth. Some single-speed BMX hubs may be around 18 to 24 tooth. A "large" final cog does make the chain further out from the steer axis, but also makes it less likely to derail. The more teeth you have, means the more chain, less the chain has to bend, and more efficient it can be. Some studies say that using anything smaller than a 13 tooth in a drive system can cause measureable efficiency losses. Nevertheless, the final drive tooth on many upright racing bikes are 11 or 12 tooth to keep the chainrings down to an acceptable size.

The alternative design is the FWD swing boom. It has chains that don't twist, but the front drivetrain swings back and forth connected to the same pieces as the front fork. thus Pedal forces can effect the steering, because as you're pedaling back and forth, your feet are pushing the fork side to side.
My team built a FWD swing boom in school - it wasn't the best idea at least for our design. Others like my friend John M. and manufacturers like Cruzbike have that nailed down better.

Edited by - Upright Mike on 12/27/2011 11:33:33
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