Is it better to use the engine as a stressed member reinforcing the chassis or keep it on engine rubber mounts?

Rubber mounts.

Most engine blocks are not designed to be stressed members. I have a buggy with solid trans/engine mounts, but there are no other loads fed into the block..i.e. the engine is not part of the stucture

I think the new Ferrari f1 engine is solidly fastened to the rear suspension

Most F1 engine/gearboxes are stressed...suspension hung right on the gearboxes in most cases......but they are designed to take the loads..

I've been wondering this for a while. In the locost what do people think the effect of tying the bottom and top chassis rails to the engine mounting point (plus tirangulating fore and aft) really would be?

The crossflow block seems to be a faily substancial lump of cast iron. If we where talking about the K-series I could understand the concern.

Mike I agree the block is quite substantial...but the consequences of just say a couple of thou' of cylinder distortion means a siezed engine...that, I think is the usual concern....

But, hey if someone wants to try it...

My concern was mostly vibration.

Oh yeah you'll get vibration..I do in my buggy....but it's not too bad

don't most modern sports bikes use the engines as stressed members?

Steve.

Good question Steve...not one I can answer though...

I'll bet if they are though that I was designed that way.

Bike engines are usually stressed members. However they are never likely to see the same sort of loads or deflections loaded into them in a bike frame as they would in a car chassis.

Any possible gains of using the engine as a stressed member would soon be negated by the vibration fed into things like the instruments. A big problem with bikes is vibration and trying to read the clocks. Well it was in my day!

Vibration play havoc with things like bulbs!

By mounting engines onto rubber you are also damping out some of the torque loads when changing gear or dropping the clutch.

Terry

I cant see any reason one couldn't use solid mounts and use the engine block as a structural member, as long as it wasn't directly taking the load. if you were using it for additional chassis stiffening it should be fine, eliminating flex can only be a good thing might as well use what you have rather than adding additional weight.

If anyone is interested as an example the (mid engined) race car I mechanic on uses the vx xe as a stressed member and hangs suspension of the gearbox casing.



Ned.

mmmm...

that looks nice...

My opinion is that it's a bad idea unless the drivetrain was designed for it. Were the engines we use designed for this stress? No. Do we, as amateur builders really know what stress levels it'll see? No. Do we know the long-term effects of running the drivetrain that way? No.

Too many unknowns for me.

Ned for christ sake stop posting pics of that thing, the drool an slebber is clogging up my keyboard now ughhhhh
Shug.
Next time ur going to croft with it let me know

Hugh,

We're at croft 15th/16th May according to my provisional calendar Hope the bodywork aerdynamic mods are finished for the start of the season in april.

see you then?

Ned.