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Old 10-18-2011, 03:41 PM   #1246
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I'm using 50K. I replaced the composite gears because the slot on the back side of the big gear stripped on my second practice run. My home track has a lot of 180* turns (host track of last year's IFMAR Worlds), which works the diffs pretty hard. The car handles amazingly well when the diff holds up. I need to get this problem fixed. I've gone through three diffs so far. One with composites, two with NT1 gears.

Have you tried putting shoe goo to get rid of the backlash from the Pin and the groove in the back of the gear. I know people do this trick on the pulleys in some electric cars where the pins are fairly small and tend to wear out the groove in the back.
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Old 10-18-2011, 05:45 PM   #1247
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Anything that rotates around an axis needs to have the same amount of centrifugal force pulling on each side of the axis, in order for the system not to destroy itself. When you shim the web gears, you are actually moving the weight of the gear around to get a tighter fit, but might be causing the gear diff to become internally unbalanced. In addition, the gear having moved causes a change in oil flow around the gear, which worsens the imbalance . It's very hard to get it right, specially when some parts come with small defects, and even if you do, it won't last long because the web gear center holes will naturally enlarge due to friction, and consequently pulling the teeths apart, before the diff blows...
WOW! Thats a great theory! I have not had any issues with the composite gears and improper shimmimg will shorten the life of any diff. Compsite diffs are not made to have long life but more performance in the race. If you dont properly shim the diff in an effort to make the diff smoother with lighter action; the life of the diff will be reduced and fail under load. Im not sure where your experience is based from but in my experience with gear diffs and gas cars; there is no vibration in the diffs. The diffs do not spin free and are placed under load by a rubber belts while in the car. You might be correct if the diffs were to free spin at 50-60 thousand RPM..
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Old 10-18-2011, 06:13 PM   #1248
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The vibrations are internal, and can't be seen on the outside because the bearings are holding the whole system. I agree that any diff is really meant for short term use, but if it can be built with excellent symmetry, then it should last longer than a few runs...Ball diffs don't have symmetrical issues, and I think they can be made to work better: stronger diff bolts, better locking mechanism, titanium or steel ring&pinion gears, etc...
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Old 10-18-2011, 06:22 PM   #1249
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!!!
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Old 10-18-2011, 06:24 PM   #1250
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The vibrations are internal, and can't be seen on the outside because the bearings are holding the whole system. I agree that any diff is really meant for short term use, but if it can be built with excellent symmetry, then it should last longer than a few runs...Ball diffs don't have symmetrical issues, and I think they can be made to work better: stronger diff bolts, better locking mechanism, titanium or steel ring&pinion gears, etc...
Serpent 710 at one point had a ball diff with giant balls and rings and the diff would work poorly. The diff would change as the race went on. Heat would make the diff start out tight and slow acting and while it ran would free up and change the handling. The 710 improved its performance the day it got rid of the balls. It has all been done before. Once technology has been replaced it is really rare that organizations will return to old ideas. Thats why the NTC3 is gone. Its diffs came apart and became unreliable. Its handling was good but really fragile and had poor drive train...
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Old 10-18-2011, 06:53 PM   #1251
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Rangulo, although you are right about these designs, I think the Awesomatix sealed,adjustable, and oil filled ball diff design is the answer ! Hopefully it can hold under nitro engine power. Check them out ....
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Old 10-18-2011, 07:37 PM   #1252
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Ok, rarely do I go off on a rant, BUT Bertrand, could you please make a thread for your theories. It's easy to sit back and justify your opinion of what you think might work when you don't make cars. R/C companies spend tens of thousands of dollars to develop a car based on decades of trial and error. I'll put my trust in that. I have a MTX-5, not a Bertrand BS-2010R. I want to share and discuss my findings with others who have the same car, so that maybe we can find a solution. With that being said, thanks, to the guys who are responding with useful input. Now, back to the MTX-5.
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Old 10-18-2011, 07:49 PM   #1253
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Rangulo asked me a question so I am answering ! I am not addressing you T...nny. Stay out of it ,since you have nothing to add in order to find a solution to the problem !
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Old 10-18-2011, 10:07 PM   #1254
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Originally Posted by Thunderbunny View Post
I'm using 50K. I replaced the composite gears because the slot on the back side of the big gear stripped on my second practice run. My home track has a lot of 180* turns (host track of last year's IFMAR Worlds), which works the diffs pretty hard. The car handles amazingly well when the diff holds up. I need to get this problem fixed. I've gone through three diffs so far. One with composites, two with NT1 gears.
I'm still surprised by this, in the end I'd say the real solution is to wait for Mugen or another company to release steel gears made for the 5, though other companies have been releasing plastic gears for their own cars and they seem to be doing ok.

Short term solution could be to up your gear oil (thicker) to lessen the loading on the gears, even though that may not be ideal for your track.


Oh and for those still being bothered by bert, do what I did and add him to the ignore list, though really that would work better if people would stop quoting him.
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Old 10-19-2011, 12:22 AM   #1255
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I wouldn't waste my time asking a person who believes the NTC3 is still competitive nowadays, ball diffs are awesome and has no clue on on-road racing...
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Old 10-19-2011, 07:39 AM   #1256
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Rangulo, although you are right about these designs, I think the Awesomatix sealed,adjustable, and oil filled ball diff design is the answer ! Hopefully it can hold under nitro engine power. Check them out ....
Awesomatix is a company dedicated to electric cars ...

If ball diffs are so "awesome", why are companies switching to gear diffs in electric vehicles such as TC and buggies??

This thread is too funny not to chime in...
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Old 10-19-2011, 09:51 AM   #1257
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Awesomatix is a company dedicated to electric cars ...

If ball diffs are so "awesome", why are companies switching to gear diffs in electric vehicles such as TC and buggies??

This thread is too funny not to chime in...
Ball diffs are good because you can set them when you want.
But definetly the oil gear diffs are better in performance. The only minus is that they are heavy but.... now that plastic gears are much stronger someone like Xray (with the 2012 spec of it's T3 electric chassis) is coming up with gear diffs

Yeah when you have to rebuilt them it's a dirty affair but you do this few time in a year.
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Old 10-19-2011, 12:28 PM   #1258
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Companies are only interested in the bottomline . Gear diffs cost more to run when the web gears keep blowing, compared to a properly set sealed ball diff. Companies don't want to make sealed ball diffs, in order to keep the cash flow coming ! Your cash Rik.....ahah....
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Old 10-19-2011, 01:15 PM   #1259
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Companies are only interested in the bottomline . Gear diffs cost more to run when the web gears keep blowing, compared to a properly set sealed ball diff. Companies don't want to make sealed ball diffs, in order to keep the cash flow coming ! Your cash Rik.....ahah....


My diffs are 2 and a half years old, same gears... I have yet to see a steel geared diff blow up with the exception of the R4 which had a tolerance problem...

Do you think the balls in the ball diffs dont need replacement? And the metal shields?? They last a lifetime??

Thanks for all the comedy you bring to this thread. But I am pretty sure the MTX5 owners want some real solutions they can try, not some "magic ball diffs".
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Old 10-19-2011, 01:42 PM   #1260
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To this date, there are no known sealed, oil filled ball diffs available, except for the Awesomatix one that just came out. So time will tell if their design will hold. By the way, my tc4 ball diffs are still smooth after six years now, while racers are crying about blowing their spec-R diffs, which is being now replaced by countless other manufacturers...
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