Real world loads

[colinmseries]

I'm having some FE work done to assess the affects of modifying a front upright. Could yourselves give me an idea of the load profile I should be using, I'm thinking that the tyre contact patch average and peak loads in terms of g would be useful?
Thanks, Colin.

 

[GregLocock]

I'm thinking use of the search feature might be useful

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[colinmseries]

Fair point Greg, I was being lazy. However, having searched, the most relevant I can find mentions a 3,2,1 rule. Does this mean 3g bump, 2g long, 1g lateral as suitable for a road car? My FE guy has experience from bus design and used to use 3,0.8,0.5 respectively but wanted me to confirm from those who know better.
If it helps judge my question, the job is to assess the effects of lowering the wishbone/trunnion pivot on a TR6 front upright.

Colin.

 

[GregLocock]

I think it would be wiser to use 5g up 4g longitudinal and 2-3 g laterally.

There are good reasons for those numbers, for a production car, and they are by no means unreasonable. 3 2 1 is commonly used for circuit cars and prototypes, but would run into problems with potholes and kerbs, in particular. We've run an aluminium suspension designed to 321 for 6000 miles or so, on public roads, so it is does not result in a particularly fragile design.

I wouldn't think twice about your proposed mod, the forces in the spindle won't change appreciably, and I'm pretty sure the original part was a belt and braces design. Hmm, messing about with roll centres? Check your roll steer curve.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[colinmseries]

Thanks for that info, it's reasuring.
My concern about things started from looking at what I saw as an increased moment on the lower threaded stub part of the upright that the trunnion screws onto. Here in England, I've tried to track down older Triumph people that might know how the loads were assumed to be taken, by the trunnion part in particular, but without much success. It has a plain bearing area immediately above the thread which I've come to regard as provided to take the lateral components and for the thread to deal with the vertical, at least while the clearances are good anyway.
The lowering proposed includes moving the upper ball joint down too. There's a weld to make at this end but I feel sure I can know it's good by examination.
Thanks, Colin.

 

[GregLocock]

First place I learnt of 321 was in a design office at Solihull in 1979, which had a lot of ex Canley people, so I would not be amazed to learn that 321 was the standard at the time.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rpmag]

good lord...Solihull and 1979...were you involved in the SD1?

 

[GregLocock]

I built a few! No, the SD1 was designed before my time. I worked in Advanced Vehicles, on the ECV series of research cars.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rpmag]

Interesting days then. Interestingly a rally engineer I recently spoke to suggested 8-5-5 for the 'G'. Why I found this interesting was that WRC cars seem to have very good levels of travel...but then they do seem to hit a lot of things in a rally.