Engine Mounting

My chassis is a Stuart Taylor Motorsport Phoenix, original design by Sylva.

STM have a modular engine mounting approach which is quite clever.  Basically all their chassis (Locost and others) have 4 mounts on the top rail that consist of vertical triangular plates with 2 M8 holes in them.

STM also manufacture engine cradles that mount to these plates.  The benefit of this approach is that they can make chassis independent of the final engine, and also things like engine swaps are simple.

They don't build a GSXR1100 engine cradle.  Mine arrived with what I was told was an R1 (Yamaha) engine cradle, but it looks a lot like their Fireblade cradle.  I don't have an R1 so it doesn't matter that it seems to be wrong, as it definitely doesn't fit my GSXR1100.

Various people have build GSXR1100 engine mounting, and different approaches have been used.  Fundamentally the GSXR1100 would mount best from the bottom.  THere are loads of nice solid mounting points, and horizontal rails would both strengthen the chassis and be very easy to bolt to the engine.  As I wanted to use the engine cradle I was mounting from the top!

The next question which seems to come up often is: hard mount, or include some kind of compliant mounting.

Benefits of hardmounting are, simplicity as the engine stays where you left it, so props, exhausts, gearchanges, clutches don't need to have those extra degrees of freedom in them.

Benefits of compliant mountings are, no danger of residual stresses on engine, less vibration from engine (NVH).


I ended up using the 12mm mounting at the bottom of the gearbox, and the two 10mm mountings that are under the manifold (these include rubber bushes), also to stop twisting (front forwards) I am using the two smaller mounts on the top of the gearbox.  Both of the gearbox mounts are big 6 inch bolts.  The top 10mm mounting will have some kind of rubber bushing so that it doesn't really do very much.

I made up some box section (the two vertical drops, and the U shaped section in the foreground), and a couple of plates (3mm mild steel) that bolt to the gearbox, and Phil from the www.locostbuilders.co.uk site welded it all up for me.  I had a minor change of plan when I realised that the engine wouldn't come out, so Phil did a redesign for me so the front (manifold side) mounts actually bolt to the frame.  Phil can weld very nicely so he made up for my slight imperfections.  We welded this up with it bolted to the engine, the obvious jig really.  The final item is very solid and not massively heavy (shown here mid painting).