Solid Motor Mounts

[tcrist]

Originally Posted by ItBites

Terry,

With only 352 HP, I wouldn't worry about breaking solid motor mounts like Scott's... or any other design for that matter.

True, but it is not necessarily the HP that might cause problems with bolts and brackets but torque. Repetitive torque, especially a lot of it, will cause bolts and brackets to have a tendency to break.

JMO of course.

[madmaxx]

I do not have a picture but the "upgraded" spf mounts are second to none. 4 bolts hold the motor mount to the frame, three bolts hold the other half to the engine and massive bolt acts as the pivot. The spf crappy rubber mounts dont break but flex to much allowing the side pipe to hit the opening. The upgraded absorb moutns are wonderfull, as close to solid as you can get but the advantages of a flexible mount.

I would bet 1000 ft-lbs of torque could not deform the mounts.

[ItBites]

Terry,

Torque and HP are the same in practice, only separated by a constant and RPM. The HP/torque at any given RPM produce FORCE at the reaction points (mounts). FORCE reacted in the deflection of materials (the mount) produces STRESS. The effect of repetitive STRESS in materials is called FATIGUE. A material's inherent ability to resist Fatigue is called ENDURANCE. Aluminum materials have no endurance limit and will fatigue to failure under any magnitude of repeated STRESS (even very small stresses, but the number of cycles of load application grow to very large numbers). Steel is not the same. If you keep the stress in a steel load-carrying member to about half of the yield stress (a material property), the member will have an infinite fatigue life (it will never fail). Given your 352 HP; your HP (and therefore torque at any given RPM) is pretty low and maybe half of that available in the race cars those mounts are typically used in. Since they do not consider the mounts wear items in Scott's race car world and since they do not bend/break from the motor torque with any appreciable frequency in that high-HP/torque environment, I conclude you could not put more than about half the FORCE/STRESS into the mounts that the racers do. This further means that your application could not produce more than about half the yield STRESS in the part, and therefore would never break. FYI, this is true for the bolts as well, since they are made from steel. Further, bolts act as springs and not all of the externally applied force is visited upon the bolt, since it is preloaded by installation torque, but that sir is another subject altogether...

I will sum-up: In short, if Scott is not permanently bending those mounts the first time he hammers it, your application cannot fail them in an infinity of drag strip runs. This is not my opinion, but simple Engineering

[tcrist]

Uh---Ok