Real World Solutions, Inc
Home of RA Classic Apex Seals and RA Super Seals
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RD-1 Gear Reduction Drive 100-Hour Inspection Report Spring, 2000: Last week, at just under 100 hours, I removed my new reduction drive (I've named it RD-1. Catchy name, no?) to determine if anything was going astray. The Ford C6 gears themselves are pretty well proven, so the main things I wanted to check were the pressure lubricated plain bearings that are fed from the engine oil system. By the way, this is the main reason that I use synthetic (Mobil 1) oil in the engine. It has better resistance to viscosity breakdown due to heat and the high pressure shearing loads imposed by helical gears. Not much of a story to tell here. The bearings showed no signs of oil starvation and had no measurable wear. I was very careful to give all the plain bearings a width-to-length ratio of well over 0.4, which is the minimum guideline recommended for bearings of this type. Failure to observe this guideline was said to be the cause of several bearing failures in the original Powersport gear drive. I think the new guys at Powersport have corrected this. The other item of interest was the rubber isolators in the damper. Several people urged me not to use rubber for the damper, but the only concrete reasons any of them could offer were statements like, "Anything made of oil will, sooner or later, return to oil." I call this "engineering by cliché," and I try never to do it. Hell, the pilot is 98% water, and I know for a fact that he or she will definitely return to that form, but is that a reason not to fly?" In any case, the rubber isolators looked just like they did when installed. In the event that they should evaporate into thin air, the redrive would still function due to the fact that they are totally captured, on all sides, by the damper. The only consequence would be a bit of a clatter when the engine was shut down. The gears themselves looked fine. One hundred hours is not long enough to make any prediction of life for them, but in a planetary drive, life is highly dependant on adequate lubrication. I took considerable pains to insure that lots of oil got to the gear set by squirting it out of the small hole between two teeth in the sun gear. This was not an original idea on my part; this is how Ford does it in their transmissions. I'm very pleased with the performance at this point and have judged it good enough to build for others. There were only two changes made during development. The first was the addition of a second oil return line from the area just in front of the rear main bearing. I originally tried to return the oil here, via a drilled passage in the gear housing, to the main return point below the gear set, but it built up too much pressure and caused the front seal to leak. The other change was to go from a needle thrust bearing on the input shaft to a pure ball bearing (the three piece kind with separate races on either side of the ball cage). This was done for TBO (ed. Time Between Overhaul) reasons. The needle bearing looked like it would have a maximum life of about 300 hours (mainly due to rpm limitations). The ball bearing has a much higher speed rating and should go well over 2,000 hours. |
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