MG Midget and Sprite General Tubular wish bones ... and coil shocks BBS discussion at British-Cars.org

MG Midget and Sprite General - Tubular wish bones ... and coil shocks

Prop, I can tell you that you don't have room for a coil over shock without removing part of the spring socket on the chassis for clearance. You then need a completely new upper A arm as well to replace the original lever shock. Then you'd want to change from the original style trunions to some ball joints for road use. All in all a heck of a lot of work and design. What you'd wind up with would probably look a lot like the Huffaker front suspension using ball joints instead of rod ends. Why try to reinvent the wheel for a road car when there are perfectly good proven upgrades to the suspension that don't involve major surgery. If you want some spring adjustment then have some adjustable spring perches made up, if you want the adjustability of a coil over shock then just get Peter Caldwell to build you a set of his fully adjustable lever actions. Ask David Lieb how well those work, he has them all around on his Sprite. Huffaker front suspension for racing in the photo. Note how the chassis is modified for shock clearance.

B Young

Prop Good to see I’m not the only one who can’t sleep due to ideas floating around my brain. Anyway, I’m going down the tubular wishbone route, or rather I’ve been forced down it, as I’m fitting a K Series Turbo engine in my 63 Sprite and the turbo would otherwise get in the way of the standard lever shocks etc. As with most things I seem to do I wasn’t happy with my first attempt (see photo). I’m now going for something more in tune with the Huffaker front suspension design, albeit not quite so complicated. As soon as I find a good fabricator for the upper wishbones I’ll post some pics. Cheers - Karl

K W Seddon

Prop, all a bell crank is is a device to transfer motion from one axis to another around a fixed rotation axis. In the case of front shocks they are usually actuated by a push rod mounted on the lower control arm and actuating the bell crank to transfer the upwards motion into a downwards motion on the inboard mounted shock. These days most racing cars and Formula 1 cars use a similar arrangement but with the shocks mounted almost horizontally instead of vertically, but in the case of a Spridget I'd think vertical shock mounting would be the simplest and take advantage of the available space.

B Young

Prop, A picture of a bell crank on my old racer attached. Coupled with B Youngs explaination and exquisit technical drawing I think you get the picture, the bell crank is just a triangular thingy that sends the forces round a corner! The pivot for this crank is show in blue and you can see the push rod from the wheel and the spring/shock. It is a good system as you can mount the spring/shock anywhere (within reason) and you can alter the rate at which the pushrod (or pull rod) works the spring/shock by altering the geometry of the triangle (i.e. alther the 'leverage' of the bell crank) Hope this helps. Malcolm

M Le Chevalier

Prop, one of the first inboard shock cars I can remember used a simple lever action off the upper control arm to the inboard shock. It was around the era of the Lotus type 49. Note the aero shaped upper control arms in the photo, those acted directly on the inboard mounted shocks. That system would be easier to adapt to the Spridget chassis I believe than using a tubular upper arm and a bell crank. Basically the upper control arm is the bell crank, changing the verticle up motion of the spindle to a down motion on the shock.

B Young

Here's another look at bellcranks, this time on a Dallara. See pic. Note that this setup incorporates an anti-roll system via forward-facing push/pull rods. For that matter the old Rover 2000s used a bellcrank sort of arrangement to actuate horizontal springs that fed loads back into the passenger cell. I don't remember the details, but it was pretty interesting. -:G:-

Gryf Ketcherside

This thread was discussed between 26/04/2011 and 29/04/2011

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