Thanks for the encouragement Bob G. Tanks for the picture tutorial Jens.
Here is a follow up on my post from yesterday.
One of the reasons I went through the work of constructing the tensioning mechanism was to stay reasonably close in construction to an antique setup that I saw in Europe many years ago. The base for the engine and generator is constructed from 6x6 in lumber. It’s held together with four lap joints and the bolts that secure the engine and generator extend through the center of the joints. No glue or other fasteners are used in the structure. The mounting surfaces for the engine and generator are reinforced with 3x3x0.25 in angel iron to avoid gauging the wood.
I may have gone a little over board by applying five layers of clear polyurethane to the base. It ended up looking better than some of the furniture in our living room.
The whole assembly is supported on six dampers. Between the natural dampening characteristics of the wood base and the dampening provided by the six supports there are virtually no vibrations or motions transmitted to the floor. I chose six support pads to help with both the lateral forces from the pistons and valve as well as the torsional (rocking) forces due to the constant acceleration and de-acceleration of the fly wheels and crank. The support dampers are not all the same since they serve different functions.
The casters in picture 5 are only used to facilitate moving the whole assembly around during construction and maintenance. During operation the frame is lowered to the floor and is supported on the dampers.
Cooling is accomplished with a small automobile radiator (a severe break with the antique setup). The radiator is mounted to allow natural thermal siphoning. I use a pair of 120 mm fans that turn on when the coolant reaches 90 deg. Celsius.
If there is interest in more details about the project or the ideas I’ve tried to implement, feel free to comment and question my reasons and maybe my sanity for doing what I have done.
Soren
Pic. 1. Shows the 3x3x15 in arm with two 1 in dia bearing blocks to pivot the arm. The pivot shaft is bolted to the face of the generator. The idler wheel is a 6.75 in dia x 1.75 in thick steel wheel running on two ball bearings. On the left you can see part of the shock absorber and the loading spring. The top part of the shock is mounted to the end of the pivot arm and the bottom of the shock is mounted to movable lever that is used to “tune” the belt tension and also make it easy to unload the belt. The C-clamp on the right is a temporary adjustment point for the tensioning lever.
Without the damping provided by the shock absorber and the force delivered by the spring, it was difficult to get the belt to track reliably.
Pic. 2. Shows the tensioning lever pivot point near the lower left corner of the generator face. The right side of the lever is resting on the temporary C-clamp putting tension on the spring and loading the belt.
Pic. 3. Shows the tensioning lever in the “down” position unloading the belt.
Pic. 4. Full view of shock absorber and belt tension spring.
Pic. 5.
Pic. 6.