A-frame rear suspension diagram

[streaky]

I have in my possession (as part of the package of papers I recently acquired - see www.pistonheads.com/gassing/topic.asp?t=102969 and www.pistonheads.com/gassing/topic.asp?t=102967) a drawing of the A-frame rear suspension.



This differs from that shown in the Bible (p159). When it stops raining, I'll pop out and check whether mine looks like this drawing or that in the Bible.

[shpub]

That is the diagram for the prototype first A frames that used the trailing arm diff carrier. It was quickly substituted by the version in the bible.

[350matt]

One presumes that the trailing diff carrier wasn't any good then?

[streaky]

Interesting! I've just checked and mine has it as the Bible diagram. Now, since that is how Chris Schirle built it, the plot thickens. I'll try to raise CS on the "dog-n-bone" and see if he can shed light - Streaky

[shpub]

Errrr except that the whole rear suspension is bolted onto the main chassis and can be taken off and replaced so quite possible that your car had it done in the past.

[Boosted LS1]

Why do they call it "A" frame rear suspension? I'd have called it rear wishbone or maybe irs?

[streaky]

shpub said:

Errrr except that the whole rear suspension is bolted onto the main chassis and can be taken off and replaced so quite possible that your car had it done in the past.

Steve - the past owners (including the factory) have all said that the rear suspension hasn't been changed since CH rebuilt it in '85 - Streaky

[shpub]

To be honest I have never seen a car that matches with that drawing so it could be like many other TVR things, something they intended to do but changed at the last minute.

[streaky]

shpub said:

To be honest I have never seen a car that matches with that drawing so it could be like many other TVR things, something they intended to do but changed at the last minute.

Well, it's interesting that the suspension on mine is Chris Schirle's "as-built" design. Perhaps he modified it later to further aid production, but then they went the original route. If I can get hold of CS I'll get chapter and verse - S

[shpub]

There were some other factors in the equation in that the diff mounts/carrier was changed as well with the bigger V8 engines as again the extra torque caused problems. TVR then modified them again and went to a all steel carrier because the original ally ones were cracking. My car has an ally one and surprisingly has not cracked which considering the abuse ahem spririted driving it gets is amazing.

I have quite a few piccies of things that TVR planned but either stopped or never actually implemented.

[ian8542]

I've just recently had my Taz converted to 'A' frame using the parts ordered from TVR.
Essentially what you get is a tubular steel diff carrier which bolts to the chassis at the front and back of the frame.
(The diff bolts to two bushes via bent steel brackets.)
The 'A' frames or wishbones, which bolt to the diff carrier and the hub/bearing carrier.
And two trailing links which bolt between the bearing carrier/hub and the chassis.
The place that did the conversion for me reckons that the trailing links do not do anything so have been left out of the equation.
I would be particularly interested in whether somebody else with chassis design knowledge would agree.

[wedg1e]

ian8542 said:

The place that did the conversion for me reckons that the trailing links do not do anything so have been left out of the equation. I would be particularly interested in whether somebody else with chassis design knowledge would agree.

I think the 'trailing links' as you call them were intended to be torque reaction arms, to resist the twisting of the A-frame. I seem to remember this was discussed here a year or more back, and the feeling was that the hub locating point for the link is not sufficiently far out from the axis of the driveshaft for it to have much effect (posibly as your convertors say). The other issue is the arc that the link has to follow as the suspension moves, leading it to need a huge rubber bush at the chassis end, rather countering the rigidity it's supposed to add....
It'll be interesting to see how your car handles without it, either way.

Ian

[Boosted LS1]

The trailing links will help to provide anti-tramp. Down side is they could give wheel hop under hard braking because they don't decouple.

[Graham]

MMM so am i correct in thinking that provided i didnt use the trailing link i could simply fabricate a diff carrier and a frames, locate a pair of hub carriers and bolt the a-frame in place to compair it to the modified trailing arms i've got at the moment ?


Ian have you got any detailed drawings of the carrier and wishbones so i could er evaluate making some heavey duty versions

G

p.s. Whens yer motor going to be ready!!!!

[ian8542]

Pulling my hair out Graham at the moment due to numerous delays (3 weeks for the bits from TVR) and now the chassis will be delayed at the powder coaters.
I had intended building the rolling chassis with engine and gearbox etc in to take to JP's on Friday for the zorst before going on holiday.
(booked around the Tas race meets and Zolder).
Now i won't be able to do it until next weekend giving me no time between exhaust fit and car rebuild.
How's my front spoiler coming on ?

IanG

[ian8542]

Graham.
You won't want a diagram of what TVR sent me as it looks like the diff carrier and 'A' frames were fabricated on the workshop floor, a bumpy one at that.
You should see my front wishbones though, Merc sphericals and Manta balljoints.

[19560]

ian8542 said:

You won't want a diagram of what TVR sent me as it looks like the diff carrier and 'A' frames were fabricated on the workshop floor, a bumpy one at that.

Fabricated in a barn? Do you have the hay frame set up?

[jchase]

Hi Ian,

Do you recall the cost of the components for the A frame conversion?

Just took my alloy hub carrier off, to find that it was previously wleded up, which makes me nervous, so I am going to have to pay out for a new trailing arm anyway. ( I have one old style alloy hub carrier and one new style traling arm - all the bushes are shot, and so are the bearings, So I thought I would investigate the "A" frame option.

-Jim