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Old 06-03-2019, 01:59 PM   #3071 (permalink)
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Old 06-04-2019, 05:29 AM   #3072 (permalink)
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Quote:
Originally Posted by euromodder View Post
Rear-wheel steering has been tried on some velomobiles because it's far easier to transfer the pedaling power to the front wheels, but was found to be unstable.

To keep them practical, their wheelbase is relatively short, and rear-wheel steering gets rather twitchy at speed.
I was just reviewing this thread, so I apologize for the long delay, but I must protest. The amount of power-robbing pedal wind-up from even a short lateral shaft can easily be more than the combined deflections from chain stretch and sag, and frame strain to rear wheel drive. I did the math, and you need large diameter carbon fiber shafts to start winning.
A long wheelbase is really no problem on the road, as users of tandems, etc. know.
The Dymaxion cars had rear wheel steering, and Bucky drove hands-off at times. It turns out that the proper geometry is just the same as a regular car being driven backwards, but it needs a damper. The damper takes care of the transient forces from the reverse caster, and in a steady-state turn it still tends to straighten as it should. The two main problems with RWS are that unless the rear track is less than the front, it can get trapped against a curb, and that it takes more time to initiate a turn, but still less than it would with two wheels.
The usual cause of twitchy steering in velomobiles, assuming the toe-in is adequate, is the usual steering ratio. People make trikes from bicycle parts, but they should start fresh. Bikes need really quick steering to balance at low speed, and the steering is never upset by side forces on the rider. Cars use 20 times more hand motion to keep it easy.
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Old 06-05-2019, 02:19 PM   #3073 (permalink)
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https://www.symscape.com/examples/ra...ctric-race-car
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Old 06-05-2019, 02:26 PM   #3074 (permalink)
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An early concept of the Clarity?

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Old 06-05-2019, 02:27 PM   #3075 (permalink)
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When I first got involved with Velomobiles, I went to visit Prof. Chet Kyle. The first piece of advice he gave me was to get rid of those sharp seams. They are OK when parallel to the airflow, but the least crosswind or error in estimating will cause big changes.
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Old 06-05-2019, 04:38 PM   #3076 (permalink)
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That is basically what I'm suggesting to aardvarcus in the Deep Blue- Suburban Streamlining thread.
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Old 06-06-2019, 12:10 PM   #3077 (permalink)
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An early concept of the Clarity?

Looks far better than what they ended up with...

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Old 06-06-2019, 03:19 PM   #3078 (permalink)
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Old 06-07-2019, 12:24 PM   #3079 (permalink)
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Quote:
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Looks far better than what they ended up with...

Yes - they got quite timid, when it came to production.
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Old 06-07-2019, 01:17 PM   #3080 (permalink)
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Considering it seems aimed at the same crowd as the Toyota Avalon, I'd say the production styling was probably a safer bet.

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