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Old 09-08-2008, 11:23 PM   #1
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Default Clutch bell bearings (failure)

I just installed a new V-Spec on a X1 CRT and ever since then I've smoked the cb bearings twice with just over a gallon through the engine.

I was running a new Ofna cb with new bearings last saturday night and only lasted all of 3 warm-laps prior to the main before they failed on me again.

Someone at the track who to me is one of the most knowledgeable people I know when it comes to RC racing suggested it might be the mugen clutch shoes I run are over heating the cb and smoking the bearings. He gave me some Ofna silver clutch sets that he had laying around and suggested that may fix my issue.

So I just thought I'd ask here to see if anyone else has experienced a chronic cb bearing failure and what you found the main cause of the issue was.
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Old 09-09-2008, 12:38 AM   #2
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are you using any kind of bearing oil?
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Old 09-09-2008, 06:34 AM   #3
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Well... several things I've seen:

1) Get some AVID bearings. $1 each online. Great bearings. (There are other good ones too, that's just what I use.)

2) Blow the grease out of them with compressed air (there will be enough left to keep them lubricated) If you leave too much in there, it gets slung out into the clutch bell, causing slipping, and more heat.

3) Make sure your endplay is set right. You should be able to move the clutch bell front to rear slightly... it should spin freely without binding, but not be "sloppy." Maybe .25 mm of play.

4) Make sure your mesh isn't too tight. There should be slight play in the mesh with the spur gear. If run a strip of paper between them and tighten it down so it is tightly meshed, it should be about right when you remove the paper.

And the OFNA clutch bell is slightly different inside diameter than almost all the others... I can't remember if it is slightly larger or smaller... but if you run an OFNA bell, yes, use OFNA shoes. I personally like the Mugen flywheel, either Mugen or Dynamite shoes (the Dynamite ones last a lot longer) Mugen or Kyosho springs, and Mugen or Racer's Edge clutch bells. Team Cobra now has new clutch shoes that come with springs, but I haven't got to try them yet... they look like they'll be good though.
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Old 09-09-2008, 07:16 AM   #4
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^Great advice! As long as you're using some OFNA stuff, try the special clutch bearings too. I leave them in with confidence for 1 gallon, then change them just because.... part #40683
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Old 09-09-2008, 07:29 AM   #5
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A little tip one of the Team Losi guys passed along this weekend. Always adjust mesh with the car sitting on it's rear end or tires so the motor stays parallel with the drive train. When you loosen the bolts to adjust mesh, the motor mount bolts can slide sideways along the slots in the chassis keeping the clutch bell and spur aligned properly. The Losi slots are a little wide and the motor can be angled slightly against the spur gear if the car is resting on the right or left side tires when adjusting mesh.
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Old 09-09-2008, 07:40 AM   #6
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Quote:
Originally Posted by DOMIT View Post
Well... several things I've seen:

1) Get some AVID bearings. $1 each online. Great bearings. (There are other good ones too, that's just what I use.)

2) Blow the grease out of them with compressed air (there will be enough left to keep them lubricated) If you leave too much in there, it gets slung out into the clutch bell, causing slipping, and more heat.

3) Make sure your endplay is set right. You should be able to move the clutch bell front to rear slightly... it should spin freely without binding, but not be "sloppy." Maybe .25 mm of play.

4) Make sure your mesh isn't too tight. There should be slight play in the mesh with the spur gear. If run a strip of paper between them and tighten it down so it is tightly meshed, it should be about right when you remove the paper.

And the OFNA clutch bell is slightly different inside diameter than almost all the others... I can't remember if it is slightly larger or smaller... but if you run an OFNA bell, yes, use OFNA shoes. I personally like the Mugen flywheel, either Mugen or Dynamite shoes (the Dynamite ones last a lot longer) Mugen or Kyosho springs, and Mugen or Racer's Edge clutch bells. Team Cobra now has new clutch shoes that come with springs, but I haven't got to try them yet... they look like they'll be good though.
+1

Don't forget to get your engined squared when you mesh. One of the most overlooked things when meshing. Engine must maintain a straight line front to back in line with the mesh of the CB. An out of line engine will cause overheating and CB bearing wear. Cost me 3 CB bearings unitl I started measuring the distance of the closest screw to the CB (front) on the engine mount from the bottom of the chasis. Then making sure the rear screw was the exact same distance. I measure from the inner wall where the screw sits to the edge of the screw head. For me its the width of a 3/32 allen key. Actually now I just put the allen key inbetween the screw and the wall and tighten. Thats my correct mesh every time with my current set up but it changes if you change CB, or clutch.

Good Luck
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Old 09-09-2008, 07:48 AM   #7
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I agree, gear mesh can always be a bearing killer for sure.

However, i stopped using those dollar bearings...some work great, then you get a couple of bad ones and before you know it, everything goes hay wire.

I started using those TKO "New Special" 5x10x4 clutch bearings...man oh man are they the bomb!!! one set has lasted me 2 gallons so far and there is hardly any play in the bearing and they are still dead smooth! i would go through those dollar bearings every so often, but i have been saving some money going with these, as i am still running the same set.

i probably have a whole box full of AVIDs, amain bearings, just about any dollar bearings i have used...have yet to last as long.

here is the link for the TKO clutch bearings:

http://tkocompetitiondev.com/shop/pr...roducts_id=347
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Old 09-09-2008, 08:08 AM   #8
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When you say blow the bearing out, does that require pulling off one of the covers and then hitting it with air or are you just hitting it with air?
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Old 09-09-2008, 08:08 AM   #9
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Quote:
Originally Posted by vladconnery View Post
+1

Don't forget to get your engined squared when you mesh. One of the most overlooked things when meshing. Engine must maintain a straight line front to back in line with the mesh of the CB. An out of line engine will cause overheating and CB bearing wear. Good Luck
That's what I was trying to get at, but should have said keeping the engine square. If you rest the car on the rear end, loosen the bolts and push the motor towards the rear of the car, the motor will stay squared because the bolts slide against the slots in the chassis keeping the motor inline and parallel to the spur gear. I was trying to make the same point, you just explained it better.
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Old 09-09-2008, 10:13 AM   #10
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Quote:
Originally Posted by hobdog View Post
When you say blow the bearing out, does that require pulling off one of the covers and then hitting it with air or are you just hitting it with air?
Just hitting it with air (from both sides) will do fine. Note that I'm ONLY talking about doing that to clutch bell bearings. I leave the rest of them as is... and I replace the clutch bell bearings every couple of race weekends, and ALWAYS before the main in a big race. (cheap insurance against failure.)
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Old 09-09-2008, 07:09 PM   #11
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Thanks for all the tips. I'll get some new high quality bearings and go back to Ofna clutch shoes.
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Old 09-09-2008, 07:37 PM   #12
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If you don't have a z-brace on your CRT
chassis, get one. The RTR and Pro chassis
are prone to flexing and a z-brace will help
cure most gear mesh and cb bearing problems.
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Old 09-09-2008, 09:01 PM   #13
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Tko's radial thrust bearings are definately the ticket!

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Old 09-09-2008, 09:21 PM   #14
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Gear mesh has to be straight and not tilted, meshing should be done with like 2 fold newspaper anything below the 40 gram mark paper is good.

You should have some end play in your clutch bell, the screw that keeps things down should be tightened down with some play, I keep about 0.25 to 0.5 of end play depending on the weather, what happens in the bearings that you are eating is simple, your clutch bell is heating up from the clutch shoes engaging, that heat travels to your bearings and bearings expand no end play and your going to pop them wide open, with a little end play they expand and contract with the heat, clutch bells u should invest in decent bearings, If your race look at ceramics.

Keep it clean and you will have a long lasting solution....

However does not mean to say they will not chew up with time, the most I ever get out of them is threw half a season, racing condition they get changed out per seasonal race.
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Last edited by shesha; 09-09-2008 at 10:28 PM.
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Old 09-09-2008, 10:21 PM   #15
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Picked up some of the Avid ceramics, not a bad deal at $5 a bearing.
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