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Author Topic: Bédélia  (Read 249 times)

Tinworm

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Bédélia
« on: 14 May 2022, 07:14:12 am »
I am building a Bédélia, a French cyclecar (the first cyclecar ever), which was designed in 1910, initially as a one-off, with public demand leading to production.

Interestingly, it was quite a successful racer in its time, despite its very odd setup. It had wire and bobbin steering which pivots at the centre of the front axle like a plank go-kart. I was going to change it to Ackerman to benefit from current wisdom but then thought I ought to keep faith with the original design. But it does worry me.

Stefan has suggested I could lean the central pivot to create caster, which could be an exciting compromise

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Jimr1999

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Re: Bédélia
« Reply #1 on: 14 May 2022, 07:45:20 am »
A brave build and I for one am looking forwards to seeing progress on this. Kudos to figuring out how to put the accents in, I struggle with that.  :)
... You can lead a horse to water, but a pencil must be lead.

Graham Hill

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Re: Bédélia
« Reply #2 on: 14 May 2022, 08:28:48 am »
Thanks Peter. I understand that posting photos here is not straightforward. However we are reviewing the whole website and this matter is top consideration.

Seven racer

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Re: Bédélia
« Reply #3 on: 14 May 2022, 09:08:43 am »
I'm glad you have reverted to the original front axle design,  don't let it worry you, fortune favours the brave.

If you build the front end with the thought that you may have to change the layout if things don't go to plan it won't be an irrevocable decision,  i.e. allowing for retro fitting other axle mounts etc.

But if it worked for the real one you have a good chance it will work for you, and will make a fantastic and unique cyclekart. Good luck with the build I look forward to seeing the build.

Peter

Tinworm

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Re: Bédélia
« Reply #4 on: 14 May 2022, 09:18:09 am »
I'm glad you have reverted to the original front axle design,  don't let it worry you, fortune favours the brave.

If you build the front end with the thought that you may have to change the layout if things don't go to plan it won't be an irrevocable decision,  i.e. allowing for retro fitting other axle mounts etc.



Peter

Thanks Peter. That is very encouraging. I have tried to build some flexibility into the design.

Peter

Tinworm

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Re: Bédélia
« Reply #5 on: 14 May 2022, 09:23:26 am »
A brave build and I for one am looking forwards to seeing progress on this. Kudos to figuring out how to put the accents in, I struggle with that.  :)

oh dear ;) Brave is usually a euphemism for stupid :)

Thanks very much Jim

(e acute is Alt 0233  but there must be some way of creating a single stroke macro to save me all that keying-in!)

TheGiantTribble

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Re: Bédélia
« Reply #6 on: 14 May 2022, 10:57:17 am »
Interesting the Pilot is behind the passenger, is that
you can't where you are going to crash!!! Joking  :D

I think this is going to look great, and ironing out
the little kinks is a big part of the fun.

Tinworm

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Re: Bédélia
« Reply #7 on: 14 May 2022, 11:15:57 am »
Interesting the Pilot is behind the passenger, is that
you can't where you are going to crash!!! Joking  :D

I think this is going to look great, and ironing out
the little kinks is a big part of the fun.

Hilarious arrangement, isn't it! For mine, I shall be the "passenger", mid-car, with a mid-engine and with my legs where the engine was on the original (which unfortunately has to be a bit wider, as a result). Something like the picture but with rear axle further back and with a faked up rear driver

StefanN

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Re: Bédélia
« Reply #8 on: 14 May 2022, 05:32:00 pm »
Stefan has suggested I could lean the central pivot to create caster, which could be an exciting compromise
I’ve been pondering this, not sure caster works on a steering axle, it’s probably more  the jacking effect that will centre the steering - you’ll only want a little.  It’ll lean you out of the corner too.  Definitely one you should test before too much fabrication.

Tinworm

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Re: Bédélia
« Reply #9 on: 14 May 2022, 06:48:41 pm »
more  the jacking effect that will centre the steering - you’ll only want a little.  It’ll lean you out of the corner too.  Definitely one you should test before too much fabrication.

What do you mean by the jacking effect?

I have been thinking that a castered central column would lead to a twisting effect when turning, with one wheel lifting.

Tinworm

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Re: Bédélia
« Reply #10 on: 14 May 2022, 07:15:37 pm »
"Jacking effect is the moving away of the wheel from the centre of the car in the road and this results due to the oversteering and is a major handling defect. Jacking effect is the moving away of the wheel from the centerline of the car in the road surface."

Working on understanding that

Tinworm

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Re: Bédélia
« Reply #11 on: 14 May 2022, 07:48:06 pm »
Spent this afternoon welding. Very unattractive welds, but penetration is sound.

Jimr1999

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Re: Bédélia
« Reply #12 on: 14 May 2022, 08:11:27 pm »
"Jacking effect is the moving away of the wheel from the centre of the car in the road and this results due to the oversteering and is a major handling defect. Jacking effect is the moving away of the wheel from the centerline of the car in the road surface."

Working on understanding that

This is how I read it,and it is something I will watch carefully as it is evident in my Kart, ...
"Positive caster also creates a jacking effect when the wheels are turned. The front inside wheel rises and the front outside wheel falls. This creates a jacking effect putting more mass on the rear outside wheel when cornering. This can create a positive turn in effect as it helps to rotate the car on corner entry. "

If I have too much, and I believe I have 4 degrees, it could prove problematic in a three wheeler. I will be starting slowly
... You can lead a horse to water, but a pencil must be lead.

StefanN

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Re: Bédélia
« Reply #13 on: 14 May 2022, 11:45:27 pm »
Imagine the hypothetical extreme situation where the steering pivot is angled so far back at the top that it’s at 45°.   Now steer right, by pulling the right hand end of the axle towards you and left hand end away.   The right hand end will push into the ground lifting that side, and the left will drop as the wheel is pushed away from the ground.

It’s a different mechanism for normal steering.

Jimr1999

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Re: Bédélia
« Reply #14 on: 15 May 2022, 06:53:21 am »
Imagine the hypothetical extreme situation where the steering pivot is angled so far back at the top that it’s at 45°.   Now steer right, by pulling the right hand end of the axle towards you and left hand end away.   The right hand end will push into the ground lifting that side, and the left will drop as the wheel is pushed away from the ground.

It’s a different mechanism for normal steering.
Absolutely agree Stefan, the effect is a lot smaller in a normal steering set up but still present. Below are the measurements I took of this effect on the three wheeler. I am using a 500mm plumbob and the variation is lock to lock with an average full lock steering angle of 270. Calculated out, full lock throws me 0.750 out of plumb to the outside of a turn with a caster angle of 40 - I hope that this is insignificant with all the other dynamics of the chassis/ front suspension but I intend to proceed with caution. I suspect this will show up less on a four wheel car as the outside rear will resist the twist.
Tinworm's centre pivot steering would exaggerate this effect.
« Last Edit: 15 May 2022, 08:54:37 am by Jimr1999 »
... You can lead a horse to water, but a pencil must be lead.