First outing with my son and the Durga ended with two broken diffs

built2scale · #1 07-05-2009

Well, as my title stated, our first bash in a parking didn't end on a good note. Found both front and rear diff pulleys torn apart.

Much like this person's pics,
http://www.oople.com/forums/showthread.php?t=20313

So what should I do now? I've read bits here and there about using a 501x diff but I don't know what parts I would need. Is there a complete set to buy or bits and pieces?

Everything else looks good so if I keep with the Durga instructions, it looks like I just need the two 37T pulleys. What do I need if I want to upgrade to the 501x diff? Just slap in a 501x pulley or is it more complex than that?

jimmy · #2 07-05-2009

I've personally (mentioning no names) rebuilt a diff like this for someone - there was no glue on the diff rings and no grease on the diff balls. I'm of course not saying that you didn't build the diffs as per instructions but blowing 2 diffs simply shouldn't happen.

I'd have thought the diffs slipping would cause this - but the one I rebuilt was down to the rings slipping on the plastic holders from what I could see.

As long as the diff rings and balls are still in good condition then you'll just have to replace the pulleys. If you're using the original stuff then pay close-close attention to the build steps, degrease and glue the rings with some sort of flexible strong glue would be best.

The 501X diff halves work on the metal-metal friction - which should stop the diff rings spinning, and it should only really be needed on the rear as the front won't have enough torque to threaten the Durga diffs if built correctly.

If this was genuinely your first time out with the car then be aware you'll have to keep checking the differentials as they bed in - since they can loosen slightly and begin to slip, which could also have been the cause.

Let us know if you need any help - the Durga is a great car

Spihc · #3 07-05-2009

This confuses me alot.

First I read that (if I use a high power motor) need to replace the rear diff halves to 501x dif halves.

Later I read that the only thing needed to replace is the diff pulley...

It might be that english is'nt my mother tounge but I really get confused with all this.

jimmy · #4 07-05-2009

I was replying regarding fixing these broken diffs - which might not have anything to do with 'powerful motors' at all. If you build them well even the stock diffs should handle most abuse you can throw at them - the 501X diff is definitely a good idea if you're racing.

built2scale · #5 07-05-2009

Thanks Jimmy, it was our first time out with the car. I think I did build the diffs correctly but can't be sure as the Durga is only my 2nd time building a RC car and the 1st time was over 25 years ago!

I will probably get new Durga pulleys then and watch my build more closely. I am running a Novak Havoc BL on this and I remember the last thing before the car was not responsive and it was when it hit a large pothole at a high speed. Maybe that put the jolt and cracked the diffs? I don't know, next time I'll make sure the parking lot is clear of pot holes.

DCM · #6 07-05-2009

the issue with the stock diffs, is having to rely on the glue to hold the plate in place. Once the glue goes, it slips, and no matter how much you tighten the diff, it still slips under load, heats up the diff and eventually melts the pulley. This usually happens on the rear diff, as it takes most load.

built2scale · #7 07-05-2009

Guys, so if I decide to go with changing to the 501x diffs, I just need the halves and the rest of the existing parts of the ball differentials from the Durga fits, correct?

shanks · #8 07-05-2009

Jimmy re-built my rear diff for me - thats why i kept loosing races!! ----- only kidding jimmy it was a great help at the time and appreciated.

To modifly as people are suggesting with 501 diff havles you need

1) 501 diff halves (try davesrcmodels in ireland at least thats where mine came from - other would be goldstarstockists - good for tamiya parts)

2) Origonal cetre pulleys

3) additional reccommendations are to fit tungsten carbide diff balls (generate less heat) fit 10 of them and use 2 standard metal balls opposite each other i.e. 12 and 6 o'clock.

I have done the above to mine and run an LRP 5.5 turn in it and have had no probs so far....

Durga is a top car in my humble opinion - A final coming soon when i can drive the thing properly

shanks · #9 07-05-2009

Quote:

Originally Posted by built2scale

Guys, so if I decide to go with changing to the 501x diffs, I just need the halves and the rest of the existing parts of the ball differentials from the Durga fits, correct?

just to clarify my comments below yes you only need standard parts (option for ceramic balls) and 501 diff halves, bearings and shims as standard

built2scale · #10 07-05-2009

Thanks Shanks, that clarifies quite a bit for us beginners.

bigred5765 · #11 07-05-2009

have seen this done a lot on other cars, usually caused buy wheel spinning or doing dough nuts,

Spihc · #12 07-05-2009

Just laid an order of ceramic diff balls. Will take my rear diff apart tonight to see what kind of damage is done so far.

Next thing will be to order the 501x diff halves, clean my metal plates from glue, and hope everything will be ok in the future.

built2scale · #13 07-05-2009

Looking forward to hear what you find when you take it apart. I'm going to take a pic of my diffs and upload later, err...at least what's left of them.

built2scale · #14 07-05-2009

Here's whats left of both my pulleys.

Spihc · #15 07-05-2009

Will take it apart in a couple of hours, these are the diff balls I ordered.

http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=310139120081, took 12 of them so I can if needed replace all of them. I guess it's the best thing to do.

shanks · #16 08-05-2009

Hi
Best to use 10 ceramic and two steel set opposite each other ie 12 and 6 o clock apparently the steel ones keep the track clean this came from a tamiya pro driver

shanks · #17 08-05-2009

Quote:

Originally Posted by built2scale

Thanks Shanks, that clarifies quite a bit for us beginners.

no worries pal - beginer myself well 4mths into it.

diff look and sound more comllicated than they are - as does lots of this rc stuff - best advice is take things apart and look and work out what the crack is yourselve - usually more simple than first thought - and then next time around dodle...dont bother me whther diff goes or not now cause it only takes 15mins to re-build and sort

Spihc · #18 08-05-2009

Forgott to post after I took my diff apart.

The diff actually looked totally ok, no plastic had changed, the metal plates where still glued to he plastic, the only thing would be that the grease seemed to have almost vaporated, there where very little of it left in there.

Will order the trf501x diff halves just to be shure now that I have ordered ceramic balls (wich where shipped less then 12 hours of ordering).

My only wory now is to get the diff tighten up enough, but not to much, this is a issue I have always had my worries about when building a new car.

built2scale · #19 08-05-2009

I ordered the ceramic balls too and the 501x diff joints as well as new plates since mine are still also glued to the plastic of the Durga diff joints. Also ordered additional pulleys just in case. This car just got a bit more expensive but my son and I are looking forward to getting it back out for the summer.

built2scale · #20 21-05-2009

A brief update; received the TRF501X diffs, ceramic balls, replacement pulleys. Put everything together and this time I paid special attention to the tightening the front and rear diffs. Tightened and backed off 1/4 turn.

I have a question regarding the slipper though. I have the 54018 slipper clutch installed and the instructions state the standard position for the nut is 3mm in. I find at that setting, it is tight with very little slip and I backed off so it's 2.5mm in for now. I'm gunshy after tearing both diffs. Haven't run the car, it is just sitting on the shelf until the weekend. For those using the same slipper, do you follow the instruction sheet and set it 3mm or do you set it by feel?