Alternative Steering Column?

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Alternative Steering Column?

Post by philhoward » Tue Jan 29, 2019 12:21 pm

I suspect the castor angle would have played a major part in your case, Roger but even so there is extra resistance even if it was a PAS rack with manual trunnions and wishbone configuration.


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Alternative Steering Column?

Post by Roger Pennington » Tue Jan 29, 2019 12:54 pm

Yes, I'm sure it would


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Alternative Steering Column?

Post by spegru » Tue Jan 29, 2019 3:07 pm

While Tracking is of course a function of steering arm length, any change would easily be compensated for by track rod end adjustment or even shortening or lengthening the track rods themselves.

I was thinking about the steering arm thing further last night and realised that steering arm length could have a massive effect on steering effort and turning circle - with the ultimate limitations being the wheel catching on bodywork or suspension and the strength of the arm itself. Although there is also that Ackerman & Bump steer question that might ruin the idea.



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Alternative Steering Column?

Post by efi_sprintgte » Tue Jan 29, 2019 3:15 pm

efi_sprintgte wrote:
Tue Jan 29, 2019 8:43 am
Our ex Jerry Ree sprint car had a DIY quick rack using a PAS rack with no pump. It was too heavy for road use imho.
PAS rack on manual geometry


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Alternative Steering Column?

Post by Coupe Racing » Tue Jan 29, 2019 4:38 pm

Makes sense and you beat me to it


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Alternative Steering Column?

Post by scimjim » Tue Jan 29, 2019 4:53 pm

Ah, you mean the steering arm on the hubs, I was thinking of the track rods and couldn’t understand why you’d want to shorten them :D


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Alternative Steering Column?

Post by spegru » Tue Jan 29, 2019 6:16 pm

The suspension geometry element defined by the mounting of the lower arms is Caster, which is top to bottom hub axis inclination as viewed from the side basically and is about self centring. The PAS setups have more caster in order to avoid feeeling too light and floaty.
Turns lock to lock is defined by the rack itself unless there are additional stops as the non PAS cars seem to have.
However quick turn in with reduced steering lock is defined by a)the gearing inside the rack and b) the length of the steering arms on the hub(s)
For a given rack offset (due to the steering wheel being turned), shorter arms would provide more steering angle at the road wheel hence making the steering even 'quicker' and also, when the rack runs out of travel, a larger steering angle at the road wheel hence also decreasing turning circle

In order to change the steering arm length they would probably have to be remade from scratch although that might actually be quite easy these days with CNC machines
Unless the main rack mounting is also moved It would also have the effect of increasing the angle at the rack track rods as it would be relatively further forward than before - which might cause bump steer
Ackerman (which enables the inner wheel to turn more than the outer when cornering) on the other hand is usually determined by having steering arms that are 'bent' inwards - and that might be possible if one were having new arms made



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Alternative Steering Column?

Post by scimjim » Tue Jan 29, 2019 7:14 pm

Caster can be top or bottom arms.

I suspect you’ll be physically limited by the suspension or bodywork before you can reduce the turning circle by any great amount?

Have you done the trig to see how much shorter arms will affect angles? Of course you need to consider it in bump and rebound too - what does the camber on a GTE go through as standard?


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Alternative Steering Column?

Post by spegru » Tue Jan 29, 2019 7:22 pm

Yes that's true. To properly know all the details will take lots of measuring and testing and that will take a while.
But I can't help suspecting that the geometry isn't that perfect anyway, even in standard form since as I understand it it was 'borrowed' from another car(s) (TR5/6) that was narrower and shorter and was itself designed in the 50s



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Alternative Steering Column?

Post by scimjim » Tue Jan 29, 2019 7:36 pm

It’s heavily based on the Alford & Alder system (designed in the 30s) used extensively on Triumphs (because they bought the company :D ) but just because it was the first IFS that doesn’t mean it’s poor. They were fitted by dozens of manufacturers including Triumph and Lotus as well as several racing cars up to and including F1 & Indy. The trunnion is far more reliable and longer lasting than a modern balljoint.

I read a lot of drivel on Facebook and other retro forums about scimitars handling poorly and it’s almost always down to cr@p tyres and/or coilovers.


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Alternative Steering Column?

Post by spegru » Tue Jan 29, 2019 8:58 pm

I did mean the fine details like Ackerman which isn't really about handling anyway, more that it might be possible to find fine improvements along the lines of camber caster, bump, and turning circle

Yes even though I've yet to drive mine I see no reason these should not handle. 5 link rear and and double wishbones at the front is a good recipe with good tyres etc



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Alternative Steering Column?

Post by 1969SE5 » Mon Jul 08, 2019 12:17 pm

anyone managed this and kept the EPAS as variable assistance ? if so what control unit did you use ? many thanks


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