12 replies to this topic

[nicolae1]

I have a 6 point roll cage allready installed in my Opel speedster turbo but :

for a 300 bhp car wit 205R16 Avon slicks in the front I am afraid that it is not enough.
So I think maybe it's a good ideea to strenghten a little the front part of the roll cage
The car looks like this , right now :



and I wonder if some extra tubes ( red coloured in the picture ) would make a difference



this red tube would be under the dashboard





what do you think ?

[Duncan VXR]

Bugger cannot view pics from work lol Will have a look later DG

[vocky]

I don't think the shock absorber mount is very strong from that direction might be better to go to the chassis frame

[nicolae1]

I ' ve made to new upper brackets but they are conected in the same two screws like the OE ones. I agree with you that these two screws might be to thin for the job. To use chassis frame would be better but things get too complicated . I don't know if it is worth the effort.

[The Batman]

would it make much difference?

[nicolae1]

I expect somebody else has allready made this mod or a similar one ; maybe for a Lotus race car. If nobody made such a mod , maybe there is not need of such a mod ; the car is rigid enough without it. the reason that I am asking is that I am not sure that the car needs its front further strenghtened.

[Exmantaa]

The window frame is hollow, so you could run the beams inside. Only pic I have is from that Lotus Sport Exige prototype:

Edited by Exmantaa, 25 May 2010 - 04:49 PM.

[Exmantaa]

More detailed pic:

Edited by Exmantaa, 25 May 2010 - 09:18 PM.

[Crabash]

I can see the cross beam being beneficial but I would have thought if you are going to brace any suspension into a roll cage it should be the parts that control wheel orientation, i.e. wishbone pickups, McPherson struts do 2 jobs hence why this is normally done in saloon cars. Not sure our cars need it but if were going to add extra bracing that's where I would look. Plus as said is the shock mount really a very strong place to tie into, it's only really there to take loads in 1 direction.

[nicolae1]

@ Exmantaa I will study that picture in more detail to see what I can learn from there. @Crabash My former experience is with cars with McPherson suspension ( Saxo , Impreza ) so I got the habit to use the same thinking that worked in the past. Probably not beneficial with this car. I have to learn new rules. Anyway a good direction was pointed out : wishbone support points. Thanks for that.

[Crabash]

I actually thought a good way to do it would be as above but with the bars continuing down to the front upper wishbone mount, hence tying it all together. But as I said, not sure rigidity is a prob anyway.

[nicolae1]

Looking closely at the picture above I noticed that they welded tubes from inside the cockpit to the shock absorber bracket only that they also welded a tube between the left and right bracket. It means that the front of the car needs to be strenghtened , does it ? ( not to speak about the ARB thickness they used )

[Crabash]

It is possible that they run that particular car on or virtually on the bumpstops, (I know that this method is used on some circuit cars, more usually single seaters) therefore increasing load on the mounts. That bar seems to bridge the open space between the 2 standard crossmembers and would I think change the force on the mount bolts at least partially from shear to tension due to the load being transfered to the other side of the car to some degree. But again for me it would have to be tied down to something as well as the shock mount.