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Mat, Oil into the redrive is needed mainly for lubrication and also heat transfer. Very little is needed as lubrication needs little with oils these days. It appears that In most cases the redrive actually fills and does not drain readily. Why I do not know. This puts pressure on the seals back and front, which suggests it may be beneficial to hold both seals in with small screws to prevent them getting pushed out. Screws are good insurance as in flight a detached seal could ruin a good day. Neil. From: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Thursday, April 29, 2021 1:23 PM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: PSRU thrust bearing/washer Straight PTFE has a Durometer 50D-65D. I'll go with it. https://www.mcmaster.com/9266K82/
Prop I have is a 74" ground adjustable Sensenich. Pitched to 22degrees. Static full power is 2200 while flying is 2600. With the 3.17 gearing, engine RPM is 8250.
Finn, I'm not sure, the restrictor is part of the fitting. Neil, can you pipe in here? I won't say I know anything like Tracy and them do, but a planetary gear, doesn't it only need a splash of oil for lub?
Does 'glass filled' mean fiberglass? Any abrasive risk if the PTFE does start to wear? Looks like they also have straight PTFE sheet stock, but I didn't look at durometer.
Are you running some monster 8' diameter prop with that ratio?
Charlie
On 4/28/2021 5:46 PM, Matt Boiteau mattboiteau@gmail.com wrote: Squished / deformed is the verbage I used back in 2019 about it. I can't seem to find any pictures on it, but I remember it being deformed up pretty good. I've been battling issues in the past with the vulcanization rubber of Neil's cushion drive was coming apart. I've put on Tracey's Cushion drive in the meanwhile.
Dry fitting everything (no oring and no snubber) with the input shaft sitting all the way down on the prop shaft, I have 0.085" clearance. To get the 5-10thou gap, I would need a snubber 0.075" - 0.080" thick. The closest I can get is 1/16" thick, which is 0.0625. There is a restrictor in the fitting going into the PSRU. I have a temp gauge on the PSRU, and it stays consistent with the oil. I have parts to add a PSI sensor to the back half of the PSRU to see if things are draining okay. The confusing thing to me is how it got hot enough to melt nylon; over 400 degrees F. That seems a lot hotter than than the shaft or bearings should ever get. The end play was good. Metal ruler across and could just see daylight across. Neil's uses a rubber oring, so we test endplay without it. Then adding the oring will add the nessessary clearance in end play. The one Neil supplied was either nylon or Teflon flat washer and it melted, so removed it. So talking with him, switched it out to the oil embedded one. Again, just a flat washer. Anyone have more details what Tracey used? Like a spring washer made out of nylon? Too little or too much end play?
Tracy specifies 0.005 to 0.035"
Note that if you check it without RTV, it may increase when you assemble it.
Finn
On 4/28/2021 1:05 PM, Matt Boiteau mattboiteau@gmail.com wrote: I have one of Neil's 3.17 psru with Tracey's cushion drive. *I also sent Neil an email but it's late in the night in Australia. After my fly off hours, tearing down the plane to inspect everything. The Ultra-Low-Friction Oil-Embedded Thrust Bearing is broken into pieces. https://wwwmcmaster.com/7421K28/
The nylon or teflon washer supplied just melted. I thought I nailed it with a fix using the oil-embedded, but I guess not.
I think in Tracey's documentation, he called it a snubber ? Any ideas what I can use, or why this happens? -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
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