just thought i would pick some brains and try and learn somthing! so-

what are the important factors when trying to design a trailing arm setup for a middy? can you incorparate any roll camber change? is a shorter arm better or is a long arm better? whats a easy cv set up if making your own? whats a good material spec? whats the best and most simple design? is there anything i can rape of a production car in the yards?

alot of questions i know but any ideas would be welcomed

The Maguire had simple trailing arms along the lines of those on a mini really but fabricated.......Try Milestone motorsport has I'm sure Ken was doing a mid engined version of the Ultimini

www.milestonemotorsport.co.uk

Go semi trailing with the rotational axis not quite at right angles to the car centre line for camber change on roll, like the sierra rear-end but mount just below wheel centre height.

Might be worth looking at what the grasstrack boys use.

Found some pictures of a fabricated trailing arm on a class 4 mini pickup though that one is still FWD:
http://www.jdmotorsport.freeuk.com/photo_class4/index.html

Mini style trailing arms are no good for a middy, minimum that will work is semi-trailling arms.
Most successful was the type used on Imps and Davrians, Davrian used it in thier tranverse mid engined cars as well as the Imp based ones -- after Imp parts supply dried up Davrian started making thier own using box section.

Istr the pivots were angled in horizontal plane at 22 degrees to the axle axis.

However you may want to copy another set up such as that used on the MGTF whih is a form of double wishbone geomtery.

cheers people, i was wanting to go trailing arm route because it helps me loads with freeing up room to mount the engine- similar to z cars, which is a grasstrack way of doing things! thinking bout it any one know a good grasstrack site or forum?

any pictures of an imp set up anyone? whats peoples veiws of the latest gtm twin trailing arm set up?

Try pinging NSDev since he's a big grasstracker (his photo archive also has some pictures of his green grasser with trailing arms.)

britishtrident: why do you say fully trailing arms can't work? Z-cars and plenty of grasstrackers seem to have made them work pretty well. The web seems woefully understocked with information about their design (compared to wishbones anyway).

Semi trailing arms do allow for camber change to be dialed out (reducing understeer) - which is very important for big heavy cars (BMW/Sierra) which roll into corners, but probably less so for a stripped out mini BEC or a grasstracker.

As for GTMs latest design - IIRC it's like a double wishbone turned around (link)
I'd imagine it's quite tweakable for handling.

I'd suggest-

Double trailing links as on the GTM Libra or Renault Sport Spyder.

Or

Single trailing arm supporting the hub with two lateral links as on the BMW Z axle, Lotus Esprit or Ford Focus.

Here I am!!!

Trailing arms are not the best system in the world, but then no system is perfect and they do work just fine.

this pic prob shows the arms best on the grasser.



Grasser rebuild, race in 1 wk!

They are mounted at 6.5 degrees from perpendicular to the car centreline, to give a small amount of camber change in roll, but not too much, as I want the wheels to stay upright in squat for traction.

Yep, the arm system gives bags of space and feeds loads into a part of the car that can be very strong.

All the stress on the grasser is fed into the main rollhoop and diagonals, the rear engine steady mount is the only stressed point not mounted to the roll hoop or further forward (well, except the antiroll bar i suppose!)Main engine mounts are off the roll hoop as well.

you can see the engine mount in this pic and just see the trailing arm at the very bottom of the pic too.



new grasser exhaust manifold!

thanks for pics ns dev, that is pretty much spot on what im aiming for and your pic shows how i intend 'hanging' the engine from the main hoop - which is the easyist way of mounting it but then means indepentant or conventional douuble wishbone becomes a big job due to the extra framework needed arround the engine which has to be stiff.

i think im going to have to commit to a single trailing arm and work with whatever problems it brings up.

i really like the gtm twin trailing arm set up becase it solves things like roll camber, anti squat/dive and makes cv/brake choice a simple issue. but..... i am a straight forward type of fella and i can see that set up being increadably hard to design, set up and get right. i think there are too many vairables for an amuture builder like myself. doh