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Old 03-27-2009, 01:57 PM   #7246
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Originally Posted by InspGadgt View Post
If you track set it just to the point where it does not slip under hard acceleration from a dead stop then pick it up, hold both wheels in your hand and turn the spur with your fingers you'll find it does still slip, not easily but it does. But since it does not slip on the track this gives you the most free diff possible. This brings up another point that your diff settings may even change depending on motor.
That's exactly what I have found. When set right it is very difficult to turn but will move with effort.
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Old 03-27-2009, 02:40 PM   #7247
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I've got that can or worms picture, but can't find it!! Since it's open anyway...

I'll try again with the diff check. You hold the right wheel and the spur in your right hand so neither can move. Then try to turn the left wheel. It should not slip - at all, ever.

Chris, I have absolutely no doubt that what you are saying about a Centrax clutch is true, but we're dealing with polar opposites here! A decent 8th engine is popping out 1500 watts-ish, we're struggling to find 200 in 12th. An IC engine outputs maximum torque well up it's rev band, and our DC electric motors output maximum torque at zero revs. Add to that you are talking about a clutch, not a diff, and it seems to me to be a completely different application requiring, without any doubt, a different lube compound.

The other thing not yet mentioned is that our 12th tracks are not flat, and the suspension cannot keep up with the little bumps and unevenness in the track (Look for that wafffleboard effect on many main straights, where the additive goes down in strips). Under acceleration and speed, the rear is hopping up and down, and the throttle is open. The shock load on the diff when a wheel touches down again is much greater than the rising, or constant load if the track was absolutely flat. Add to that the slight eccentricity of most wheels, and you have a situation where the balls in the spur gear are constantly slipping and grabbing. Unless the diff is absolutely tight - no slip at all when tested by hand - you will be wearing the balls or the races.

Whether you know what I do for a living or not (thanks, Jason!) I can assure you that if your collective knowledge of mechanics was applied to the products we design and build, I wouldn't travel in the products we make!!

I type all this with a smile and a pleasant demeanour, and no concern at all about your posts. You can believe me or not, you can act on the advice or not - but I'm glad you lot don't design my diffs, and Dave Irrgang does!! The can of worms is firmly shut here - and I hope you will all be as smiley and content as I am, and enjoyed our little conversation.
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Old 03-27-2009, 03:35 PM   #7248
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Honestly I've never tested in that method. I've always been taught to set diff on the track to ensure the most free operation of the diff and over time you can get a good feel on how tight that is by holding the wheels and turning the spur. I still have a couple of weeks until my next race though so I won't be able to test to make sure the 2 corrolate. Seems to me that setting that way would be rather subjective as different people...what feels like no slip to me may well slip when someone stronger than I performs the same test.
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Old 03-27-2009, 08:14 PM   #7249
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Originally Posted by SlowerOne View Post

Chris, I have absolutely no doubt that what you are saying about a Centrax clutch is true, but we're dealing with polar opposites here! A decent 8th engine is popping out 1500 watts-ish, we're struggling to find 200 in 12th. An IC engine outputs maximum torque well up it's rev band, and our DC electric motors output maximum torque at zero revs. Add to that you are talking about a clutch, not a diff, and it seems to me to be a completely different application requiring, without any doubt, a different lube compound.
You confuse me. One minute you say a thrust bearing is a thrust bearing regardless of application, now you admit different applications do require different lubes. So let's see if we can figure this out.

1. Are a diff and a thrust bearing identical or not? How can a diff be EXACTLY the same when we are applying torque to what is essentially the cage of the bearing while a thrust bearing will only see forces applied to it via the races (cage seeing only a small load from inertia)?

2. Is AE silicone the best lube to use on a thrust bearing (leaving diffs out of this equation)? If not, why use something inferior? If yes, why?

I'm not trying to be argumentative here, just trying to understand your reasoning. Plus, when someone questions my intelligence I tend to go on the offensive.
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Old 03-27-2009, 08:16 PM   #7250
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As for the turning one tire method for checking tightness, I have used that method for offroad cars since diff gear access is not so easy. Should work just fine on a pan car too.
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Old 03-27-2009, 09:21 PM   #7251
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To thrust or not to thrust!? Is that the question?? We are still talking about diff's right?

Chris,
Nope, my son's soccer team has a double header saturday morning (8 & 11).
E
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Old 03-28-2009, 01:04 AM   #7252
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You confuse me. One minute you say a thrust bearing is a thrust bearing regardless of application, now you admit different applications do require different lubes. So let's see if we can figure this out.

1. Are a diff and a thrust bearing identical or not? How can a diff be EXACTLY the same when we are applying torque to what is essentially the cage of the bearing while a thrust bearing will only see forces applied to it via the races (cage seeing only a small load from inertia)?

2. Is AE silicone the best lube to use on a thrust bearing (leaving diffs out of this equation)? If not, why use something inferior? If yes, why?

I'm not trying to be argumentative here, just trying to understand your reasoning. Plus, when somuoeone questions my intelligence I tend to go on the offensive.
No problem Chris - it's just that I am not questioning your intelligence, just your knowledge. We should never stop learning...

A thrust race is a thrust race, but don't confuse that with the duty at which a bearing operates, the way it operates, and thus the lubrication it requires. I have rolling element bearings in my BMI that require a light oil, but the rolling element bearings in my road car's gearbox require a heavy oil, and the rolling element bearings in my wheels require a heavy grease. It's not a question of what type the bearing is, it's a question of what duty the bearing is operating under. A thrust race in our 12th cars sees a fraction of the duty that a thrust bearing in a Centax clutch sees.

Yes, your point about the cage is well made, and is another clue to the change of lube. We aren't trying to lubricate metal-to-metal, we're trying to lubricate plastic to metal. In this case, the best lube for plastic to metal is the AE diff grease. Furthermore, we do not want any drag at all from the diff, so yet another reason why we avoid heavy oils and greases, and use the AE diff grease. The lube is to suit the application, not the bearing.

Hope that helps.
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Old 03-28-2009, 03:14 AM   #7253
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Quote:
Originally Posted by SlowerOne View Post
I've got that can or worms picture, but can't find it!! Since it's open anyway...

I'll try again with the diff check. You hold the right wheel and the spur in your right hand so neither can move. Then try to turn the left wheel. It should not slip - at all, ever.

Chris, I have absolutely no doubt that what you are saying about a Centrax clutch is true, but we're dealing with polar opposites here! A decent 8th engine is popping out 1500 watts-ish, we're struggling to find 200 in 12th. An IC engine outputs maximum torque well up it's rev band, and our DC electric motors output maximum torque at zero revs. Add to that you are talking about a clutch, not a diff, and it seems to me to be a completely different application requiring, without any doubt, a different lube compound.

The other thing not yet mentioned is that our 12th tracks are not flat, and the suspension cannot keep up with the little bumps and unevenness in the track (Look for that wafffleboard effect on many main straights, where the additive goes down in strips). Under acceleration and speed, the rear is hopping up and down, and the throttle is open. The shock load on the diff when a wheel touches down again is much greater than the rising, or constant load if the track was absolutely flat. Add to that the slight eccentricity of most wheels, and you have a situation where the balls in the spur gear are constantly slipping and grabbing. Unless the diff is absolutely tight - no slip at all when tested by hand - you will be wearing the balls or the races.

Whether you know what I do for a living or not (thanks, Jason!) I can assure you that if your collective knowledge of mechanics was applied to the products we design and build, I wouldn't travel in the products we make!!

I type all this with a smile and a pleasant demeanour, and no concern at all about your posts. You can believe me or not, you can act on the advice or not - but I'm glad you lot don't design my diffs, and Dave Irrgang does!! The can of worms is firmly shut here - and I hope you will all be as smiley and content as I am, and enjoyed our little conversation.

Dont worry about anything buddy. This is good conversation for everyone. The key is that everyone needs to take it as friendly conversation. I personally dont use nor will i use a actual thrust bearing over the flanged bearing because of the performance loss i saw on the clock. That does not mean that you guys are wrong for wanting to use them. Just my preference. Thats why this is a hobby. I always have an open mind and listen to what all of you have to say and i think it is great that we have some very knowledgable people up here. Honestly, you all make great points. I think that you are all pretty much in agreement with everything except application. Whatever the case, this makes for very good conversation and it is nice to see a good technical conversation going on. You guys are pretty cool.
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Old 03-28-2009, 06:50 AM   #7254
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OK, one last bullet before I drop this. If AE diff lube is the best for thrust bearings, why does AE put their black grease in with their thrust bearing equipped diffs (offroad cars)? It seems to me if AE silicone was so good for it they could save a bit of money by using it on both.
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Old 03-28-2009, 07:15 AM   #7255
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Quote:
Originally Posted by chris moore View Post
Man where's that can-o-worms picture when you need it.
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Take your pick:
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BMI's DB12R-can_of_worms.jpg   BMI's DB12R-cremworm.jpg   BMI's DB12R-cano.jpeg   BMI's DB12R-wormsign.jpeg  
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Old 03-28-2009, 10:30 AM   #7256
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OK, one last bullet before I drop this. If AE diff lube is the best for thrust bearings, why does AE put their black grease in with their thrust bearing equipped diffs (offroad cars)? It seems to me if AE silicone was so good for it they could save a bit of money by using it on both.
I can't access the Associated site at present, so I am going to guess that it is because the cage in the B4 thrust race is metal (so the lubrication is for metal to metal contact, not plastic to metal) or that the race has deep grooves to retain the balls (so again, metal to metal contact as the balls rub on the grooves, due to differential speed of the ball surface against the deep groove) as they do on Schumacher off-road diffs. It might be a plastic cage in deep grooved races, in which case the 'deep groove' rationale applies.

Thanks for the kind words, Protc3. It is, as you say, a hobby, and each to their own. The speed diference was not one I'd noticed, but now you mention it, I feel some more testing coming on!

It's been fun, but this is probably too much of a thread hijack to be worth much more words. Good luck - whatever lubrication you use!

PS - I prefer the can on the left!
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Old 03-28-2009, 03:34 PM   #7257
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I noticed more overall consistant steering with the flanged bearing. I picked up about 4 seconds on a total run over 8 minutes which isnt huge unless its real close or at a big race where 1 second can seperate A and B mains.
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Old 03-28-2009, 07:03 PM   #7258
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Does the RR come with the lowered pod plates?
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Old 03-28-2009, 11:51 PM   #7259
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Does the RR come with the lowered pod plates?
Sure does. The RR pod plates allow you to run to the rim and still get ride height. They are about 2mm lower than most other companies "lowered" pod plates.

Well I finished the indoor season on a positive note. I placed TQ and won the A main Woo Hoo! Finished 2nd in the points series behind the one and only legendary Mike Ivy. Of course if Mike were at the track, he would have had about 4 laps on me. Miss ya Mike! Where ya been?
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Old 03-29-2009, 07:46 AM   #7260
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Sounds good. Thats the only thing I didn't like with the regular R was trying to get ride height in the rear.
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