I'm sure this has been discussed over and over again (a search turned up little however) but what is the square tubing size and wall thickness recommended for building engine cradles. I'd like to keep weight down but don't want to under build it just to redo with bigger stuff later.

I'm using a zx14 motor and building what can best be described as a sub-frame to hold the lump and chain driven diff securely together. That frame gets dropped into and attached to the engine bay of our vintage Saab racer. (I know what your thinking, but someone has to do it!)

All suggestions and experience appreciated.
Jonathan

Jonathan
I'll be interested to hear how this progresses, as I'm looking at doing something similar in the back of the new Furore F1 chassis. I'm using 50 x25mm with 1.5mm wall thickness for the "diff end" of the cradle with the rest done in 25mm sq 1.5mm wall thickness. This is for the ZZR1100 engine - the first cradle is made, but haven't decided on diff yet so that side is unfinished, hoping to try it in the new chassis next week to finalise mountings etc.

The existing car has the engines bolted direct to the chassis on 25 x 25mm extensions, these are 12guage which IIRC is around 2mm wall thickness (no doubt someone will correct me if I'm wrong) - I feel this was overkill, hence why I've gone for 1.5mm this time. The cars done around 800 miles of (sometimes) total hooligan use & the mounts have given no problem whatsoever.
If I can help with any pics etc just u2u me.
Sounds like an interesting project - good luck with it!
Russ

[Edited on 30/11/06 by russbost]

Russ,
Thanks for the info. That’s helpful because 25mm square stock tubing (1 inch over here) was what I've been eyeing at the steel shop. Are you sure 1.5mm isn't sort of thin? I was looking at 1/8 inch wall which converts to over 3mm thick. Is that over kill?

I'm planning on using the Ford 7" LSD diff converted to chain drive by Douglas at Westgarage for this project. Seems like a very well made unit and a very good value. If you haven't seen it you should check it out. http://www.westgarage.co.uk/

Jonathan

Most chassis are 1.5mm, or more likely 1.6 (16 swg), so should be fine for the cradle, as it's only got to react to the engine twist, which isn't much in a bec.

3mm thick is massive overkill & will be heavy, as said above most chassis are 1.5 (1.6) mm & that doesn't seem to provide any problems even with "big" engines like the 'Busa & ZX12

my engine is (was) a little lighter and less powerful (zx9), i held it in place with 1" 16g, and never bothered to weld the bottom of any tubes. It was also untriangulated, and held up just fine over 2 trackdays and lots of road miles. Id say that with the extra weight of the zx14, you will be ok if you weld it well and design it properly.

Thanks all for the advise. 1" 16g it is. I'll let you know how it turns out.
J