I have just got round to designing the front suspension. Needs to be wide track to match the Sierra based De Dion rear so loads on the chassis mounts will be correspondingly higher.

I bought a handful of locost suspension brackets off ebay but haven't used them. They appear to be cut from 12 guage CR sheet and not really up to the job. At the rear I made some of my own from some 5mm HR plate. I would like to find a more substantial chassis mounting for the front suspension too.

I have been planning to use rose joints rather than the usual polyeurathane bushes. The question is ...

Can they be mounted back to front? i.e. the threaded part bolted through chassis mounted plates, and the wishbones fitted to the rose jointed ends. My thoughts are to fabricate the wishbones as triangular frames with a single long stud passing right through the base tube and through both rose joints.

interesting, no reason why not that i can think of

you'd have to make it very precisely to avoid either a nasty side load on the bearings when tightened, or it being loose and needing shimming. But i suppose when done normally they still need shimming well,

If rose joint works one I can't see why it shouldn't work the other way, the loads are the same but in effect are reversed.

Seems like a very complex solution to something that's just not a problem.

*All* the wide-track GTS', Luego's, Locosts (like mine) use 3mm plate wishbone brackets and have been fine for 1000's of miles.

As for the rear... AFAIK *all* IRS cars use 3mm plate brackets and are fine.

It's wishbones generally that fail on these cars... not the brackets!


The other disadvantage of deviating from the norm' is that if you get an IVA inspector who doesn't like/understand/trust your design he may fail it without some engineering evidence that it's safe.


Sorry, I don't mean to be a ludite... I'm just not sure I see the problem when so many other cars are ok.

Cheers,
James

Would have to put crush tubes in chassis at every mount too

Really not ideal it puts a bending load on the rose joint.
Also using 5mm plate for the wishbone bracket is likely to cause cracks either in the tube or the weld, if you weld any stressed mounting on to the chassis if possible it should no more than about 1mm thicker than the chassis tubes.

Was looking at an old F3 car the other day and the suspension brackets were only 1mm with no problems. Little bit of triangular bracing on them but that's all - 5mm is way OTT

I would stay with the exiting tried and tested methods; unless you have engineering knowledge. But in this case as British trident says, don't put rose joint with a bending load, it will lead to tears (well broken rose joints)..

Dan

I accept there is a logic in the 'if it ain't broke don't fix it' ... but sometimes the tried and tested methods do break even on cars with standard length wishbones, and mine will be about 40mm longer.

The weak point usually is the tubular bush housing on the wishbone ends. These are fine normally, but are badly stressed if the chassis brackets are able to bend or flex and they are only welded to the side of 1.6mm box section. That is why I was looking to change the design. On the rear I welded the brackets to a plate which spread the load across the chassis so there is not a significant difference in thickness at the weld interface.

I don't understand why, if the rose joint ends are shimmed to remove any pre-loading and are free to articulate, how they will be subject to bending loads?

However ... As I said I am still at the design stage and all advice is well taken - thanks

You will get bending loads if the shank of the rose joint is attached to the chassis, this is because the joint sticks proud of the chassis. In the normal configured the rose joint end fits inside the U bracket and the shank is loaded only along it's axis.

Dan