A triangulated frame that attaches at the PSRU would be better - Prop-Trans-Mount-Frame -

The engine hangs on the other side and provides the power, nothing else.

As long as you run direct-drive the torque will never be more than the engine produces, but as soon as you ad rpm-reduction you introduce more torque coming back into the engine-housing....

 

Am I wrong somewhere...??

 

Thomas J.

The 12As had the motor mount attached to the front case. Build the engine up to 240HP and the front case starts cracking through the mounting stud holes. All of the torque generated must be controlled by that mounting point.

 

Later, 13Bs had the motor mounts attached to the center irons and that worked fine until you build up the engines past 280 HP and it breaks the mounts, and the turbo giant killer drag racers and some street racers and drifters go past 500 HP, and the mounts break and the top dowel hole in the rear iron starts cracking out, and in some cases shear off the end of the dowels.

 

So the FD 93-95 twin turbo engine comes out with the motor mounts on the rear iron and the area around the dowel holes built up to make it stiffer. And when you pump it up over 700 HP it still breaks the mounts and or shears off the dowels and breaks chunks out of the rear iron and or bell housing. So the drifters add over-sized case bolts and precision hone all of the bolt holes to fit the bolt shanks tightly and add a row of alignment dowels along the spark plug side of the engine to help it keep its shape during high output. And it works just fine.  

 

So the idea that the engine should have part of its mounting system in line with the bell housing surface on the rear iron, is a good one. That is where that twisting force must be controlled. Mounts forward of that location (closer to the front pulley) should not resist torsion in the engine, if you are getting close to 500 HP because this will help deform the engine and create problems as above.

 

I have yet to see a normally aspirated installation that I suspected was in danger of going  over 200 HP. So in those cases and in the case of a single rotor at even 100 HP you could almost safety wire the engine to two 4X4s and it would work fine.  The engine is not in danger from being deformed by torque output. 

 

The single rotor at 100 HP at 6000 RPM has 60 foot pounds of torque. Then through the 2.78:1 reduction unit to get 166.80 foot pounds measured at the mounting flange of the reduction unit. And even better, also at the prop flange.

 

The Trans Am cars mount the 600 HP Small Bock Chevrolets between the front and rear 1/4" plates. Never an attempt to use the stock engine mounting pads on the sides of the block. 

 

So if carried into a sandwich plate divide by the distance from the center of the prop shaft to the mounts to get the torsional load on the mount. Same for a plate between the pan and the engine.  Say that is just 12", so you would expect to see 166.80 pounds pushing down on one side and 166.80 pounds pushing up on the other side.

 

So it shouldn't be a problem.

 

Sorry about that picture it got too big to see somehow.

 

Lynn E. Hanover