Motor pinion to support bearing gap?

[stevehof]

I had been just lightly setting the pinion on the support bearing but that approach is not working out. There's enough frame flex or downward torque on the pinion going on that I've ruined two support bearings and two lower motor bearings. The pinon end is just working its way down into the bearing.

I talked to the tech at Aero-model (Hacker Motors) today and he suggested a gap of .015 inch. Seems a bit excessive and I can't  figure out an easy way to set that gap. How much of a gap are you guys using and how do you set it? I have ordered new style main gears and pinons to retrofit my ships. I have been using the metal motor/pinion frame alignment brace since it was made available. I want to get this right when I install those new gears...Thanks!

[BrianE]

I set mine up as specified in the E7SE manual:

"Important!
Pinion should rest on inner race
of lower pinion support. Failure
to configure properly will result
in premature motor bearing wear"

[stevehof]

I set mine up as specified in the E7SE manual:

"Important!
Pinion should rest on inner race
of lower pinion support. Failure
to configure properly will result
in premature motor bearing wear"

Yes, that is the way I've been doing it. However, there seems to be enough frame flex or movement of some sort that the bearing is actually pushing down too hard on the bearing. hard enough to cut the end of the pinion and deposit the resulting aluminum 'dust' into the race of the support bearing. I've had it happen twice. In both cases, there is no sign of the bearing moving down on the shaft. There is a nice round circle impressed into the motor shaft where the set screw was tightened. There is no sign of a downward smear on that indentation.

[stevehof]

OK, just noticed that this particular E7 did NOT have the metal motor/pinon side plates. I have 'more than one' E7... So, maybe the motor shifted down into the pinon support a little bit. However, my 'other' E7 did have the metal motor/pinion side plates and it did the same thing.

Is sitting the pinon down on the bearing still the accepted way to go. Or, is the guy from Hacker motors correct in stating that it needs a gap between pinion and bearing?

[Jean-Luc Bolduc]

I presume you're running the old style pinion and main gear ?

 If yes, run the new E7SE hard coat pinions and main gear 121T, they generate less downward force. I did run the Hacker motor a year ago in one of my E7 and I did not have alu powder or severe galling as you describe.
You could try a thin steel washer between the pinion and support bearing to help out, but  probably easier to run the new gears. And we run the pinions resting on the support bearing.

[flyalan]

I have run the old gear, new gear, Scorpion motors and Hacker motors.  I have never seen or experienced what you are describing.  I am not disputing what you seem to be seeing but to date I am unaware of anyone having this type of problem.  The only pinion/bearing problem we see is when the pinion is NOT resting on the support bearing.

I have seen some galling of the motor shafts on Hacker motors before.  How does the end of the shaft look?  Is it snug in the lower support bearing.  You could use some red loktite on the shaft end where it goes into the support bearing.  Just a little.  This will assure that the shaft is not turning IN the bearing.

Flex is not an issue with this airframe.  Believe me! Besides if flex there was your problem the metal motor plates would have improved that.  Apparently that is not the case.  Are you sure your hacker motor shaft is not actually moving up and down in the motor can itself?

Keep us posted on your troubleshooting.

Cheers
Alan

[stevehof]

I presume you're running the old style pinion and main gear ?

 If yes, run the new E7SE hard coat pinions and main gear 121T, they generate less downward force. I did run the Hacker motor a year ago in one of my E7 and I did not have alu powder or severe galling as you describe.
You could try a thin steel washer between the pinion and support bearing to help out, but  probably easier to run the new gears. And we run the pinions resting on the support bearing.

Thanks, as noted in my initial post in this thread, I have already ordered the new gear sets. I do like the idea of a thin steel washer and will look into that also. Curious that the tech guy at Hacker insists that you need a significant gap between pinion and bearing. Didn't make sense to me and that's why I'm asking here.

BTW, the other motor that was involved in this same type of support bearing clog and failure in my other E7 was a Quantum 4530. That one DID have the metal side plates. Both failures involved the original gear config.

[stevehof]

How does the end of the shaft look?  Is it snug in the lower support bearing.  You could use some red loktite on the shaft end where it goes into the support bearing.  Just a little.  This will assure that the shaft is not turning IN the bearing.

Thanks, the shafts of both motors were badly galled and somewhat reduced in diameter. This is understandable since the bearings were nearly seized. I used red Loctite on the replacement motor that I installed in the first ship that failed in this manner. I could not get a new shaft for the Quantum 4530. However, I haven't had enough flights on that ship yet to see if that is going to make a difference. I plan to use red Loctite when I get the new gear sets, Along with some sort of hard metal washer.

[RichH]

I had a similar experience and talked with Pat at KDE.  He recommended a small amount of green Loctite between the motor shaft and the third bearing inner bearing.  This prevents fretting between those surfaces.  I had gone through a couple of pinions and a motor shaft due to the wear described here.  I haven't had any issues since using the green Loctite.  It does make it a bit of a hassle pulling the motor as you have to pull the third bearing block attached and use heat to separate.  Don't try applying heat while installed.  It's very easy to ignite the main gear.  Don't ask me how I know...

Rich

[Jean-Luc Bolduc]

Also been using Loctite 680 (green) on the support bearing and motor shaft mating.  Helps keep the motor shaft in 100% condition.

[Barry Tilson]

Any photos of this?


Barry

[stevehof]

Any photos of this?
Barry

If you are asking for photos of the damaged pinions, here you go. I installed the new gearing today along with two small 6X9X .15mm bearing shims between the pinion and support bearing. http://www.amainhobbies.com/advanced_search_result.php?keywords=cln+4736&x=8&y=5 . I don't know if these will help but nothing much to loose by trying them. As you can see by the photos the pinion has been pushed down on the bearing hard enough to emboss or 'machine' the inner race into the pinon on one motor and completely into the bearing on the second motor. I know I had set these pinions with no pressure on the bearing after all the screws were tight. The 14t was only run for about 10 flights. Wow, hard to believe you reps haven't seen this before. Oh well, glad to have the redesigned gear train and new metal side plates available to try fix this problem...lol. Did not photograph the bearings. However, they were covered with impacted aluminum particles from the pinion. Either that got into the bearings or the pinion pushed the dust cover of the bearing into the race. Either way, the bearings were toast too.

[stevehof]

delete - double post

[RichH]

You want the pinion resting on the third bearing so it takes the thrust loads created by the slant gears. My pinions looked the same, as did the motor shaft where you can see signs of fretting. I would replace the motor shaft and bearing also and use Loctite per above.


Rich

[stevehof]

You want the pinion resting on the third bearing so it takes the thrust loads created by the slant gears. My pinions looked the same, as did the motor shaft where you can see signs of fretting. I would replace the motor shaft and bearing also and use Loctite per above.
Rich

My pinions were 'resting' on the bearing. I used red Loctite on the 14t seen above but I guess it didn't bind the shaft to the bearing race. I used green Loctite on the latest new motor install with the new gear set. I would have replaced the shaft on the Quantum motor but they aren't available yet. So, I ordered a new motor to get back in the air. Two Hacker 530 editions are back at Aeromodel for repair, since I stripped the shaft set screws  on both. I should have used heat to loosen the factory Loctite. I am going try to repair the Hacker 470KV seen in the photo myself.

This turned out to be a rather expensive 'repair/retrofit'. Three gears sets, one new motor and two in the factory shop for repair. To be fair, I have probably a total of 1500-2000 flights on my ships to date so overall, still my favorite all time heli.

Personally, I think the best fix is the new re-designed gear set. This pinion support design is not made to take much in the way of 'thrust loads'. The bearing is only going to handle radial loads. There was just too much downward pressure on the pinion with the old gears. Why else would Matt have gone to the trouble and expense of redesigning those parts, along with the nice metal motor/pinion alignment plates part number 710-101. Edit: If you are using the old gear set, try putting shims like I linked to two posts up. These might not be the best but it's a start. At the very least a thin shim or two will prolong the time it takes for the aluminum pinion to touch the bearing and begin to self destruct.