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Old 06-22-2009, 01:56 PM   #1
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Default Serious Diff Issues in my TC4

Well yesterday was my first race day with my tc4. I picked it up used and set everything up with a mamba 5700 system on normal timing and a 2s LiPo. I test ran it in my driveway and all was fine. About 6 or 7 laps into practice my diffs seem to have loosened up. My gearing on my car is 22-72 and it wasnt too ballisticly fast at all but a good steady pace for me to learn with. The car finally got so bad that I pulled off and it would barely come back to my pit. I tore open the car to find that both diffs where completely destroyed. There was plastic shavings in the gearbox and the diff rings where actually melted to the cups. Now Im mad, run into the LHS, pick up all the parts to rebuild two diffs. Build them, grease them, tighten them up, run and slam them in my car. Everything is meshed up real nice. I tighten the diffs up then back off a quarter turn. Lucky me I made it back in time for my practice lap over the transponder and I line up. Take off, 4 laps in notice the car seems to have loosened up again, and all of a sudden Im dead on the side. Same thing happened, front diff seems to have done the exact same thing, but the rear is ok. I tightened the rear back down and this time added a bit of threadlock. The front however is just as dead as the first batch. Lucky I still had my truck to run in the other race I was signed up for.

Now, I wonder what is going on. Everything seemed fine until I got on the track. Most of the guys there told me to get a spool for the front. Is a one way the same thing? Can anyone here give me a good recomendation on what to do? Thanks all. My losi JRXS Type R is on its way (obviously the racing thing hooked me) and hopefully I wont have these sort of problems with a car as nice as that.
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Old 06-22-2009, 02:56 PM   #2
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Not really answering the question, but isn't there a diff break in that you have to do after rebuilds?
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Old 06-22-2009, 03:12 PM   #3
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The Mamba has too much power for the plastic diffs. You should switch them both out for steel diffs if you are going to continue running that motor with an 8.18 FDR. You could also replace the front with a steel spool. A spool is a solid axle. A one-way allows the front wheels to turn freely and coast when the brakes are applied, effectively eliminating any front braking but giving you better cornering ability. You will need front brakes with that motor unless you are running oval, so a spool would be better.
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Old 06-22-2009, 03:18 PM   #4
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The Mamba has too much power for the plastic diffs. You should switch them both out for steel diffs if you are going to continue running that motor with an 8.18 FDR. You could also replace the front with a steel spool. A spool is a solid axle. A one-way allows the front wheels to turn freely and coast when the brakes are applied, effectively eliminating any front braking but giving you better cornering ability. You will need front brakes with that motor unless you are running oval, so a spool would be better.
So I want to get the steel Outdrives for each side of the rear diff, and then get a front steel spool? Where is the best place I can pick those up at off the internet. My lhs doesnt have those in right now so its just quicker to get them off the net. This setup should be ok with my mamba? And Im not sure exactly what gearing is best but the 8.18fdr was just my first attempt. Like I said for some reason the car seemed slow compared to the other cars out there.
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Old 06-22-2009, 03:26 PM   #5
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http://www3.towerhobbies.com/cgi-bin...?&I=LXJTS2&P=7

Tower hobbies still carries these parts. I don't actually have a TC4, I have a pair of TC3s. The drive train is mostly the same but I'm not certain if the diff halfs are identical. I know that the steel TC3 diffs use a different diff ring than the plastic ones (plastic have a D-ring). You may have been going slow because the diffs were slipping. Your car should have been pretty fast with that setup.
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Old 06-22-2009, 04:17 PM   #6
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Some more thoughts....

When you rebuild the diffs, make sure you replace the screw, nut and spring as well as other parts. Also, I just looked at a chart I made as a guide for starting gear ratios when I was converting from brushed to brushless. The Novak 7.5 is roughly the same RPM as the Mamba 5700 and for that motor I have an FDR of 10.73. A 17 tooth pinion with your 72 tooth spur woud put you in the ball park. This was just a starting point meant to keep the motor cool enough to go up teeth on the pinion if needed for more speed.
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Old 06-22-2009, 05:35 PM   #7
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Quote:
Originally Posted by Ride1226 View Post
Well yesterday was my first race day with my tc4. I picked it up used and set everything up with a mamba 5700 system on normal timing and a 2s LiPo. I test ran it in my driveway and all was fine. About 6 or 7 laps into practice my diffs seem to have loosened up. My gearing on my car is 22-72 and it wasnt too ballisticly fast at all but a good steady pace for me to learn with. The car finally got so bad that I pulled off and it would barely come back to my pit. I tore open the car to find that both diffs where completely destroyed. There was plastic shavings in the gearbox and the diff rings where actually melted to the cups. Now Im mad, run into the LHS, pick up all the parts to rebuild two diffs. Build them, grease them, tighten them up, run and slam them in my car. Everything is meshed up real nice. I tighten the diffs up then back off a quarter turn. Lucky me I made it back in time for my practice lap over the transponder and I line up. Take off, 4 laps in notice the car seems to have loosened up again, and all of a sudden Im dead on the side. Same thing happened, front diff seems to have done the exact same thing, but the rear is ok. I tightened the rear back down and this time added a bit of threadlock. The front however is just as dead as the first batch. Lucky I still had my truck to run in the other race I was signed up for.

Now, I wonder what is going on. Everything seemed fine until I got on the track. Most of the guys there told me to get a spool for the front. Is a one way the same thing? Can anyone here give me a good recomendation on what to do? Thanks all. My losi JRXS Type R is on its way (obviously the racing thing hooked me) and hopefully I wont have these sort of problems with a car as nice as that.
I noticed quick wear and tear if you lube the diff ring gear and diff pinion.
Run them dry. Doesnt make sense but running it dry produces more
"grab" between the diff pinion and ring gear.
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Old 06-22-2009, 11:36 PM   #8
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I have five tc4's (from CO27 TO NOVAK 3.5R), and the best BEST gearing for the 5700kv would be between 6.92fdr and 7.5fdr or 24t-72t to 26t-72t. At the 8.18fdr you were at the car will be very slow and undergeared! I raced another tc4 with a MM5700KV on a medium track and he was using stock gearing (24t-72t) with no heating issues! As far as the diffs, you need a front spool and metal outdrives in the rear(IRS make aluminum diff outdrives). Also I see you are getting a losi TYPE-R, which is very good, and I think uses front LCD (LOSA3344) drives INSTEAD of CVD'S. You will need to fit these lcd drives in the front of the TC4(with some dremeling of the caster blocks) in order to get rid of the CHATTER that comes from using a spool with CVD'S!!! That chatter is so severe that it loosen your steering system, blow your front diff bearings, and destroy your spool's outdrives!!! WAY BACK IRS USE TO MAKE an aluminum spool for the TC4 that was much lighter than the steel ones, and because the losi lcd's were not available then, the aluminum spools would not last that long when used with CVD'S. Now even HPI(HOT BODIES) have copied the losi lcd's for their CYCLONE TC.............................
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Old 06-23-2009, 02:25 AM   #9
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Quote:
Originally Posted by beemerfan View Post
Some more thoughts....

When you rebuild the diffs, make sure you replace the screw, nut and spring as well as other parts. Also, I just looked at a chart I made as a guide for starting gear ratios when I was converting from brushed to brushless. The Novak 7.5 is roughly the same RPM as the Mamba 5700 and for that motor I have an FDR of 10.73. A 17 tooth pinion with your 72 tooth spur woud put you in the ball park. This was just a starting point meant to keep the motor cool enough to go up teeth on the pinion if needed for more speed.
The spring is most likely the culprit. Replace it and the problem should go away.
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Old 06-23-2009, 09:47 AM   #10
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I have five tc4's (from CO27 TO NOVAK 3.5R), and the best BEST gearing for the 5700kv would be between 6.92fdr and 7.5fdr or 24t-72t to 26t-72t. At the 8.18fdr you were at the car will be very slow and undergeared! I raced another tc4 with a MM5700KV on a medium track and he was using stock gearing (24t-72t) with no heating issues! As far as the diffs, you need a front spool and metal outdrives in the rear(IRS make aluminum diff outdrives). Also I see you are getting a losi TYPE-R, which is very good, and I think uses front LCD (LOSA3344) drives INSTEAD of CVD'S. You will need to fit these lcd drives in the front of the TC4(with some dremeling of the caster blocks) in order to get rid of the CHATTER that comes from using a spool with CVD'S!!! That chatter is so severe that it loosen your steering system, blow your front diff bearings, and destroy your spool's outdrives!!! WAY BACK IRS USE TO MAKE an aluminum spool for the TC4 that was much lighter than the steel ones, and because the losi lcd's were not available then, the aluminum spools would not last that long when used with CVD'S. Now even HPI(HOT BODIES) have copied the losi lcd's for their CYCLONE TC.............................


you mean one can use type R shafts instead of the MIP CVD ones from AE ?


But the lentgh of the arms seems quite different ?!!!!
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Old 06-23-2009, 10:24 AM   #11
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There is a rebuild kit that comes with a new screw, locknut, and spring. I would replace all three, I used to run a TC3 with the TC4 composite diffs in mod all the time with no problems. I was running anywhere from a 7t-10t motors with out slippage, if anything my front diff would get tighter/notchier as I ran it.
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Old 06-23-2009, 11:25 AM   #12
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HERETIC, yes you can use them and they are about the exact same length: mip cvds are 76mm and lcds are 75+mm total length with the same size axle!!! Actually the axle being the same makes the whole swap possible; keep in mind that the design of the type-R lcd(losa3344) will make it look a lot shorter, but if you put them next to each other they are only about 1mm apart!!! Remember to use the type-R lcds and not the shorter XXX-S ones!!! With the LCDS YOU will be able to power through the corners without wheels vibrations that cause understeer,and without having to wait for the straits to power up. All you will need to do is to widen the hole in the caster blocks where the dogbones go through. Furthermore you can also use type-R lcds on the nitro tc3 front end without any modifications at all. TC4s and NTC3s with lcds in front will make a tighter turn, and a more stable, predictable turn than with the CVDs....I only have cvds in the rear,and it has been over a year since I have been racing my tc4 NOVAK 3.5R against 1/10 nitros without any visible damage to my front aluminum spool!!!!!!!!!
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Old 06-23-2009, 02:14 PM   #13
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So it seems the general consensus is I need to drop my FDR just a bit, and get a Spool for the front end and rebuild the rear end with some steel outdrives? Seems like I have a little work to do. But, at the same time I may just swap all of the electronics from this TC4 to my new Losi JRXS Type R that is coming in. Will the chassis handle the power better? I know it damn well will be a better performer thats for sure.
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Old 06-23-2009, 06:21 PM   #14
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I would agree that the LOSI TYPE-R will be easier to drive, set-up etc... but the TC4 is more of a continuous building challenge that can be overwhelming in certain cases! The losi is more a out of the box competition vehicle while the TC4 is more a basher with the potential to compete,provided you put in the time to make it work for you!!! I have never owned and will never own a belt car, they lack realism to me(no real race car runs these kinds of belt systems), and I they will slip a lot and eventually wear out when using MOD motors,while the shaft system will surely never slip! I have had many friends who switched from shaft to belt and flet let down a bit because once the belt car was dialed there was not much more left to do as with the shaft car; no more challenge!!! The losi will get you in the podium right out of the box, but the with the TC4 it will be a while. Then again the shaft cars have evolved, and the new shaft design(AWESOMATIX) will kill all belt driven cars period. The AWESOMATIX will be the new revolution, and the only new car I will consider purchasing to get to a podium as fast as possible.You can check it out by searching AWESOMATIX on youtube and you will see how it kills the belt cars.............................................
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