Originally Posted by 2door
I just thought of a way to illustrate solid, as opposed to resilient mounting.
If you have access to any type of vibrating appliance, say like a hand held engraver. Hold it lightly between your fingers or in your hand and turn it on. Feel the vibrations and in some cases you can even see the appliance, or tool move, or vibrate.
Now clamp your hand around that tool tightly, Hold it and you'll hear and feel the vibrations being reduced. This is because you are keeping the tool from moving in your hand as much as it did when it was being held lightly. This is similar in concept to clamping an engine tightly against the frame.
In other words, the more the source of the vibration is allowed to move the longer, or larger the frequency of vibration is allowed to become. If it can't move, the vibes are held to the absolute minimum. If it can move, in the case of rubber mounting, the vibrations increase.
Tom has it right here.
A bicycle engine that is rubber mounted moves a LOT more than a solid mount.
Bolting the engine down solid to the frame allows the frame to dampen the vibrations where rubber simply attempts to control the movement in the rubber, which quickly destroys mount bolts and strips case studs.
This is also the reason I dislike aluminum frames, since they do not damp vibrations as well as steel unless they are of very high quality. They can also work harden and crack from the constant pounding.
A good fitting mount saddle with no gaps and nice tight mount straps is a much better way to reduce vibration than rubber.
Large frames like my Specialized HardRock dampen vibes even more since the bigger frame spreads the load better.
The paint under my mounts is still intact after five or six different motors.
Notice how you never see me posting about stuff falling off or breaking?
Solid is the only way to go unless you have mad machining skills and a degree.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.