Rear-Wheel-Steering Recumbent Bike Prototype Testing

Part of our Cal Poly senior project. This is the prototype for a bike that will compete in the 2010 Human Powered Vehicle competition in 2010.
www.asme.org/Ev...
Many of the features are adjustable, including the head tube angle (the angle of the hinge), the wheelbase by multiple dropouts for the front and rear wheels, the control sensitivity by the lever-arm linkages, and the seat position.
Partial credit for this design goes to Dennis Renner, for giving us the initial idea of a rear-wheel-steered recumbent.
• Recumbent FWDRWS
Before this one, we constructed a proof of concept bike, with no pedals, and a different steering mechanism.
• 2 week prototype
By adjusting the head tube angle on our prototype, we discovered that a forward angle gives us better stability at high speeds.
See footage of our final bike on this channel: / moynihanigan

[@FatalNoogie]

The project happened three years ago. After testing many different angles and wheel configurations, the riders found a forward-leaning head tube angle more desirable at high speeds. That's their preference, not mine. I was/am too short to reach the pedals. The final bike had a forward-leaning head tube angle and it worked for the racers. If you don't like that configuration you can build your own bike.

[@FatalNoogie]

@cbulen There are a lot of factors in play. Because some features are adjustable, each time we changed something, we had to get used to riding all over again. This configuration sacrifices stability for agility: hence the really tight turns you see in this video. The prototype is also much heavier than the Renner bike, and heavier than our final bike. You can see videos of our final bike on the channel for user moynihanigan

[@dr.realshit6512]

Great idea, I like that the chain is much shorter this way

[@tonicedeno]

Simpler Dutch Kervelo design does away with chain.

[@RhisiartGwilym]

If you look at still pics of Dennis Renner's Mark 2 FWDRWS, you see that though he sits on the front part of the bike, he is close to the steering axis, and in fact its centreline passes through his upper back. Also, he tells me, the angle to the horizontal of the steering axis is 71 degrees, and as you can see from the stills, it leans BACKWARDS. All forward-leaning steering heads are going to be more unstable. Dennis's FWDRWS is an easy-ride, safe street bike. He's cracked it. Copy him!

[@Kudem_sky]

Весьма занятный экземпляр! Молодцы!

[@cbulen]

Oh yeah, I should add: A correction to the article was printed in the issue that followed. Vol8 no 1, page 3

[@FatalNoogie]

@wolfekeeper To do that on this bike (with the adjustable head tube) would put the head tube almost horizontal, so I don't see how the back wheel could even turn side to side with so little rotation about the vertical axis. I'd need to see an example to understand what you describe. In any case, the project was finished some time ago. I'll post links in the description.

[@iamtheoriginalcody]

Wow I can't believe the low speed stability over most rear steer diamond frames. Love the adjustability you built in also. Will you be at the east coast event also?

[@cbulen]

@FatalNoogie Cornelius suggested that a 4-bar linkage (pivots oriented vertically) might solve the low balance speed (he called it CBS-critical balance speed) as it would give the bike a long "virtual" trail for the rear wheel placing the instant center far forward. (see pg20 of his article in IHPVA. I am thinking of trying non-parallel 4-bar, with the instant center far forward of the rear wheel. Did you guys explore that?

[@vistigioful]

Cool.

[@stevenboelke6661]

I've been wondering about things like this recently. The mechanical arrangement seems preferable, but can it be made viable for low speed cornering?

[@wolfekeeper]

Steering geometry looks wrong to me; for RWS the trail point of the rear wheel is supposed to be in front of the front wheel. You can do that with the proper linkages or by having the steering axis point there.

[@jdc4316]

Been a decade. Still alive?

[@raftmant]

Hi! I plan to build a rear wheel steer recumbent , but in videos it seems so unstable. Is it stable in high speeds? Can it be driven hands off ? I tought maybe in video it seems unstable becuse of the rider sits above the wheel center? Can anyone help? thanks!

[@COMB0RICO]

NEATO!

[@kanpurunplugged9970]

Make it into a reverse trike with rear wheel steering it will be more stable

[@cbulen]

How come Denrnr's RWSFWD recumbent seems more stable that yours? He mentioned that your group contacted him for info on his bike.

[@Steinklein]

I'm planning on using steering like that in a tadpole trike. Have you tried something like that already?

[@FatalNoogie]

shadaik Nope. Although I got very familiar with bicycle design at Cal Poly, I'm afraid I have no experience with trikes.

[@FatalNoogie]

shadaik After viewing images of tadpole trikes I can see how that could work. Clearance with the ground may be a limiting factor in the design. I don't know whether the part/assembly drawings for our 3 bikes would be useful to you. If so, just message my channel and I'll find a way to send you the full report.

[@jdc4316]

@@FatalNoogie you still use yours?

[@Sstraum]

The bike is way to unstable when cornering. Its a reason why the bikes today are frontwheelsteerd. Rearwheeldsteer will never be the future, its just to unstable, you can never have godt control of a fastgoing vehicle with it.