BMI's DB12R
#7246
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.
#7247
Tech Fanatic
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.
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.
#7248
Tech Champion
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.
#7249
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.
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.
#7250
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.
#7251
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
Chris,
Nope, my son's soccer team has a double header saturday morning (8 & 11).
E
#7252
Tech Fanatic
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.
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.
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.
#7253
Tech Lord
iTrader: (13)
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.
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.
#7254
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.
#7256
Tech Fanatic
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.
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!
#7258
Does the RR come with the lowered pod plates?
#7259
Tech Elite
iTrader: (64)
Join Date: Jun 2008
Location: Conducting aggressive board meetings at my local track
Posts: 3,301
Trader Rating: 64 (100%+)
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?
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?
#7260
Sounds good. Thats the only thing I didn't like with the regular R was trying to get ride height in the rear.