Geek1945
Well-Known Member
As an old part-time motorcycle (MC) mechanic wouldn't chain PRSU's be consider for aircraft engines? It seems the big concern is engine power pulses combined with the flywheel effect of the prop. I realize this topic has been previously discussed, yet the addition of damping on drive and driven ends hasn't. Personally I have never thrown a chain since I don't rely on removable connector links preferring riveted ones. Using a chain breaker tool makes remove easy and replacements require sprocket removal in any case.
My experience with MC drive shows there are damping to both ends of the final drive. Those are the multi-plate wet clutch on the drive side. On the driven side the chain is coupled to drive hub via a rubber cushion damper (cush). Finally there is the tire itself which limits maximum torque by slippage. In actual use (by an older conservative rider) the cush handles the engine pulsation and to a lesser degree slack in the chain without complaint. Considering sport bikes can do wheel stands at highway speeds I doubt a prop would be a problem.
As for strength some hi-grade number 530 and 620 chains are rated at 11,000lbs tension if more is needed then additional chains could be added. Considering several 100 plus HP 'sport bikes' weighing 500lbs plus rider (170lbs) are capable of 180 mph, it would appear propeller loading wouldn't be a problem considering torque/HP to reach these speeds.
The pulsation problem could be negated by using cushs on both drive and driven end of a chain PRSU. By absorbing and smoothing power delivery to the prop. Modern O-ring chains are capable for running in the open for 500 miles without any lubrication. If lubrication is need oil dip systems are available or easily fabricated or manually lube. To eliminate oil thrown stains from the chain a chain guard could be built which also help to reduce debris from collecting on the chain. This guard would do much to reduce chain noise too.
Considering the ease of measuring a chain for wear, replacement could calculate with an auto chain tensioner. This method of determining is commonly done of both cam drive and final chain MC tensioning systems. Considering a chain requires far less tension than belts tension on bearing would be reduced. If a concern with the engine PTO an additional pillow block bearing could be added to make a 'half shaft' supported on both ends of the drive sprocket.
As in motorcycles when chain wear indicates replacement, sprockets 'should be replaced too'. Most MC chains will last at least 20,000 miles or more if cared for and excessive sudden torque isn't applied like stunt riding. The MC driven rear wheel also is a heavy flywheel and it can be seen using the center stand. These snaps would equate to sudden throttle change in aircraft and would need to be avoided so engine and prop speed could stabilize equally especially at reduction of speed. Sudden throttle movements 'abuse' don't seem likely in aircraft even during TO.
Considering these drive rubber cush(s) wouldn't a chain be acceptable for a PRSU?
My experience with MC drive shows there are damping to both ends of the final drive. Those are the multi-plate wet clutch on the drive side. On the driven side the chain is coupled to drive hub via a rubber cushion damper (cush). Finally there is the tire itself which limits maximum torque by slippage. In actual use (by an older conservative rider) the cush handles the engine pulsation and to a lesser degree slack in the chain without complaint. Considering sport bikes can do wheel stands at highway speeds I doubt a prop would be a problem.
As for strength some hi-grade number 530 and 620 chains are rated at 11,000lbs tension if more is needed then additional chains could be added. Considering several 100 plus HP 'sport bikes' weighing 500lbs plus rider (170lbs) are capable of 180 mph, it would appear propeller loading wouldn't be a problem considering torque/HP to reach these speeds.
The pulsation problem could be negated by using cushs on both drive and driven end of a chain PRSU. By absorbing and smoothing power delivery to the prop. Modern O-ring chains are capable for running in the open for 500 miles without any lubrication. If lubrication is need oil dip systems are available or easily fabricated or manually lube. To eliminate oil thrown stains from the chain a chain guard could be built which also help to reduce debris from collecting on the chain. This guard would do much to reduce chain noise too.
Considering the ease of measuring a chain for wear, replacement could calculate with an auto chain tensioner. This method of determining is commonly done of both cam drive and final chain MC tensioning systems. Considering a chain requires far less tension than belts tension on bearing would be reduced. If a concern with the engine PTO an additional pillow block bearing could be added to make a 'half shaft' supported on both ends of the drive sprocket.
As in motorcycles when chain wear indicates replacement, sprockets 'should be replaced too'. Most MC chains will last at least 20,000 miles or more if cared for and excessive sudden torque isn't applied like stunt riding. The MC driven rear wheel also is a heavy flywheel and it can be seen using the center stand. These snaps would equate to sudden throttle change in aircraft and would need to be avoided so engine and prop speed could stabilize equally especially at reduction of speed. Sudden throttle movements 'abuse' don't seem likely in aircraft even during TO.
Considering these drive rubber cush(s) wouldn't a chain be acceptable for a PRSU?
