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Author: Subject: Front swing arm upright design
CB11ACD

posted on 24/5/20 at 05:23 PM Reply With Quote
Front swing arm upright design

I am hoping I can pick the brains of members here so I can find a solution to my rather unique problem.

I am starting to design a car based on a 2CV chassis, suspension, engine and gearbox however I have moved the engine and gearbox to the back to make it mid-engined (see awful illustration below).



It has developed a lot since then, but it illustrates the general idea.

The issue is caused by the front brakes on a stock 2CV being attached to the gearbox. The gearbox moving to the rear takes the braking with it. So I am looking for ways to have outboard brakes at the front, without drive and retain the 2CV suspension meaning it will be a front swing arm.

Now Pembleton don't have this problem, but their in-house built V-sport uses a 2CV inspired front suspension setup retaining front wheel drive and the 2CV gearbox therefore not needing outboard brakeing. They have designed their own front upright none-the-less and this is it:



With a normal suspension setup the upper and lower arms are not linked and so using ball joints etc work fine as the upper and lower arms can be parted meaning you can fit the front uprights. A 2CV uses a kingpin (which I want to avoid) and Pembleton seem to use some sort of track rod (actual name escapes me) end that can be removed horrizontally meaning the front uprights can be fitted (picture above describes it better than me).

What I have read on various forums on the topic is to avoid using track rod ends in this orientation, however that is usually in relations to a double wishbone setup.

So considering all of this, my solution (currently) is to use Mini front uprights as they are small with lots of spares availability and performance upgrades as well as using a screw on balljoint top and bottom. I was considering using a solid turned part top and bottom and using a similar track rod end setup similar to the Pembleton attached to a nice bespoke swing arm (modified from stock citroen).

So, given all of that, what is everones thoughts on the topic? anyone have a better sugestion? I am very open to ideas.

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britishtrident

posted on 25/5/20 at 04:30 AM Reply With Quote
The 2CV hasn't got swing arm suspension front or rear , just about the only cars with swing arm front suspension were the Hillman Imp, the Lotus 6 and the werid setup on some Ford US pickups. The 2CV has leading arm at the front and trailing arm at the rear.

However your real problem is going to be the rear suspension --- as on rear engined rear wheel drive car the rear suspension is the critical bit.

[Edited on 25/5/20 by britishtrident]





[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]

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Dingz

posted on 25/5/20 at 11:27 AM Reply With Quote
Interesting but tricky project! Its a long time since I had a 2Cv type car, apart from replacing the king pins they were trouble free. You want to put brakes outboard of the hubs so if you make a leading arm like the pembleton one it will need to be very stiff to cope with the braking reaction forces. I suppose you dont want to keep driveshafts and an empty gearbox so you could keep the original brakes?
The suspension as you will know uses 2 big tubes across the chassis to support the arms, when the engine goes in the back, presumably with another set of front leading (now trailing arms) I don't think there will be much tube left, rear bump steer could be hard to control.
The Vauxhall H type 10 had leading link front suspension probably with king pins if you could find pictures it may give you ideas.
Good luck!





Phoned the local ramblers club today, but the bloke who answered just
went on and on.

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Theshed

posted on 26/5/20 at 09:25 AM Reply With Quote
That Pembleton upright is a nicly thought out design. It looks as if it was simply turned in a lathe - very simple to make.

Nothing much wrong with spherical bearlings/rod ends in that orientation - they are strongest with radial loads. Given the size of those and the weight of the car they are pretty hefty.

Are you using a motor cycle wheel? Could you not use something like the Pembleton design and bolt on a caliper mount and steering arm? You could always use their upright and leading arm and leave in the outer cv joint.


Looks like a fun project - 2CVs are such a hoot to drive.

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sebastiaan

posted on 26/5/20 at 11:39 AM Reply With Quote
a bit of a different opinion maybe, but could you:

a) keeb the box casing & inboard brakes
b) integrate a small emotor in the original box (but stripped down to 1 gear)
c) make it a hybrid!

something like this: https://www.kellycontrollers.eu/hpm5000b-5kw-96v-leghuteses you could overdrive to 8,5kW @ 3000RPM (ish), which could provide a very useable torque-boost. Add a 96V Li-ion pack, controller and rudimentary control and off you go!

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Tigg

posted on 26/5/20 at 12:08 PM Reply With Quote
2cv sahara

Just a thought, Citroen made a 4 wheel drive version, the 2cv sahara, by sticking a second engine and gearbox in the back. Dont know what brakes they used but might be worth a look.
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SJ

posted on 26/5/20 at 02:33 PM Reply With Quote
quote:

Just a thought, Citroen made a 4 wheel drive version, the 2cv sahara, by sticking a second engine and gearbox in the back. Dont know what brakes they used but might be worth a look.



Always assumed they used the same as at the front

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CB11ACD

posted on 26/5/20 at 04:56 PM Reply With Quote
Thank you all for your input.

I have gone through probably every option in my head (this idea has stuck arounf for almost a year so far). I did consider the hybrid route but goes against the "ethos" of what this project is which is low cost, mostly 2CV parts and light weight (sound familiar?)

The sahara is great but from what I have read not that much better off-road than a lightly modified 2CV.

The Pembleton front arms and hub is a great design but is incompatible with a 2CV as they do not use the original cross member and bearings and have instead designed their own.

Ok, I will go with the Mini uprights and turn suitable top and bottom bits and use rod ends. The car will be very light (under 400kg hopefully) and mid engined so no weight upfront.

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Dingz

posted on 26/5/20 at 07:04 PM Reply With Quote
The 4 wheel drive versions were as far I know 2 front ends stuck together, it was to save turning it around in a forest, a bit like a mini train.





Phoned the local ramblers club today, but the bloke who answered just
went on and on.

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britishtrident

posted on 26/5/20 at 08:47 PM Reply With Quote
Graft on VW Beetle suspension





[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]

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britishtrident

posted on 26/5/20 at 08:50 PM Reply With Quote
quote:
Originally posted by CB11ACD
Thank you all for your input.

I have gone through probably every option in my head (this idea has stuck arounf for almost a year so far). I did consider the hybrid route but goes against the "ethos" of what this project is which is low cost, mostly 2CV parts and light weight (sound familiar?)

The sahara is great but from what I have read not that much better off-road than a lightly modified 2CV.

The Pembleton front arms and hub is a great design but is incompatible with a 2CV as they do not use the original cross member and bearings and have instead designed their own.

Ok, I will go with the Mini uprights and turn suitable top and bottom bits and use rod ends. The car will be very light (under 400kg hopefully) and mid engined so no weight upfront.



Mini front end and 2CV rear will result in colossal oversteeer





[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]

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CB11ACD

posted on 27/5/20 at 07:07 AM Reply With Quote
quote:
Originally posted by britishtrident
quote:
Originally posted by CB11ACD
Thank you all for your input.

I have gone through probably every option in my head (this idea has stuck arounf for almost a year so far). I did consider the hybrid route but goes against the "ethos" of what this project is which is low cost, mostly 2CV parts and light weight (sound familiar?)

The sahara is great but from what I have read not that much better off-road than a lightly modified 2CV.

The Pembleton front arms and hub is a great design but is incompatible with a 2CV as they do not use the original cross member and bearings and have instead designed their own.

Ok, I will go with the Mini uprights and turn suitable top and bottom bits and use rod ends. The car will be very light (under 400kg hopefully) and mid engined so no weight upfront.



Mini front end and 2CV rear will result in colossal oversteeer


Mini front uprights, 2CV suspension. tempted to do double wishbone on the rear for packaging reasons but we'll see.

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ettore bugatti

posted on 27/5/20 at 05:20 PM Reply With Quote
Have a look at the French MEP formula cars build in the sixties/seventies, they used a lot of Citroen parts.
https://www.lanemotormuseum.org/collection/cars/item/m-e-p-x27-1968


Looks they use traditional doube wishbones and a upright, so maybe Triumph Spitfire upright could be an option with a custom wheel hub to mount the 2cv wheel on.

Edit: missed the front suspension bit, why not put a stub axle on the king pin? Although the trailing arm might not be strong enough in the first place.

[Edited on 27/5/20 by ettore bugatti]

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