| Torque as it is applied to the mill is determined by how much resistance is taking place in the mill compared to how much force is applied to the input shaft of the mill. Therefore, as the mill needs to turn to work, torque to the input shaft of the mill is determined only by what is being ground and the setting of the mill burs. How that turning force is generated prior to reaching the input shaft of the mill does not matter. You could have an army of hamsters turning a wheel or a 5000+ horse power diesel engine and the torque on the mill would be the same. I think the manufacturer's/vendor's concern regarding the adaptation of modified drive mechanisms has to do with the reduction in human fatigue. As the mill will last many years if it is only used to the degree someone is willing to crank it by hand. If the mill is motorized or connected to a bicycle or something similar, the mill will probably wear our earlier. Lateral force applied to the input shaft may also result in premature wearing of the bearing on one side if too much tension is applied to the belt. Of if there is a lack of lubrication. The speed reduction can also be accomplished with a bicycle chain/sprockets or gears. On my mill, which is a Diamant, I'm using an electric motor. The mill is turning at the manufacturers recommended speed. By using a small enough pulley mounted on the motor, the belt speed is reduced to the point where the mill is turning at the correct speed. I also disassembled the mill, drilled, taped and mounted oil cups to allow the oiling of the bearing surfaces of the mill. Small diameter holes alone would also work. I have an oil can filled with vegetable oil and I oil the mill every time I use it. As the bearing contact surfaces are riding on this film of oil, the mill will last many years, even though it is motorized. The bearings on this mill are pressed-in sleeve bearings, they can easily be replaced, however I doubt if this will ever have to be done. So, because I exceeded the design specifications of the bearings by motorizing the mill which applies a lateral load on the bearings, I compensated for this by providing a method of lubrication to the critical wear points. As for speed, this needs to match what the mill is designed for. To calculate, first divide the diameter of the driven pully (mounted on the mill) into the diameter of the drive pully (mounted on the hand crank). This will tell you the ratio. Draw a sketch, it will help. Example: a 6 inch diameter drive pully (at the hand crank) turning a 12 inch diameter driven pully (at the mill) will reduce the speed of the driven pully (at the mill) in half. 6 inch divided by 12 inch equals 0.5 So, if the input speed at the mill needs to be 80 rpm, the hand crank pully would need to turn 160 rpm (revelutions per minute) double the speed. 160 rpm divided by 60 seconds per minute equals 2.6 turns per second. The benefit to all of this is that your torque at the input side (where you are cranking) will be cut in half from that needed at the mill, however your rpms (revelations per minute) will be double. Of course there is a little added torque due to the friction inherent in your belt and pully setup. This configuration is generally referred to as a "jack-shaft". Something to think about would be to have your crank arm adjustable. The distance,(radius) from the center of the shaft to the center of the crank handle. Ergonomically, this will allow for the adjustability of the crank location and will be a great benefit to you. As grinding our own grain is a step toward personal empowerment, I will help whomever asks. You can email me at Paulemorneault@yahoo.com and I will do what I can to assist. |