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George Lendich wrote:
Ernest,
This is something I'm familiar with, but can you tell me who makes this
particular PSRU and how is the sun gear attacked to drive shaft.
This is a one-off design done at Lakeridge (8NC8) by Joe Hunt a few years ago. The sun gear apears to be a integral part of the input drive shaft. The propeller shaft is driven from inside splines on the planet gear carrier.
**** Firstly plain ball bearings DO take some thrust. Tracy does use one in
the front ( of his PSRU) I believe.
I can't say how much thrust it will take but it appears to be quite large -
take the size to your local bearing supplier and they will identify it and
give you a thrust rating.
I know there's a 1,000 ft/lbs of thrust there, but how much is carried
rearward I'm not sure.
I have a bearing supplier that I've worked with in the past. I will get them in the loop.
The sun gear is a tight slip fit into and rides on the inside of the ball bearing housing, which is 3/4" high. The balls are 1/2" diameter as close as I can measure, but I'm unable to get the calipers down into the housing for a really accurate measurement.
I was thinking about this last night when I should've been sleeping, but I would think that the reaction forces would be a simple vector based on the helix angle of the gears and the input torque. Assuming a 3" sun gear with a 30degree helix and 150ft/lb of torque, the reaction force would be:
150ftlb*12in/ft / 1.5in = 1200lb of force across the helix teeth
The part absorbed by the rear thrust bearing would be:
sin(30) * 1200 = 600
I didn't take the time to measure the helix angle this morning like I meant to, but if the angle is 20degrees, the force at the rear bearing will drop to around 410, and 10 degrees will take it down to 208.
Question - is the rear teeth of the sun gear turned down before being
pressed into the bearing - I'm assuming it is.
George ( down under)
I took a picture last night, but didn't get around to uploading it to the computer. The rear of the sun gear is turn down to be a tight slip fit into the ball bearings inner race.
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