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Old 06-17-2011, 12:34 PM   #46
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i put the spec r gear diff in my top photon at the xray challenge at west coast and realy dug it! felt like more punch outa the corner! ran it for the first time at camarillo last weekend and im sold on the gear diff!
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Old 06-19-2011, 08:19 AM   #47
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Hi Rick,
Just out of interest, have you tried running 500k oil in the front diff? Or just run the putty?
Just looking for your opinion on a comparison really, been running a front gear with kyosho 500k recently, and whilst I've run putty in a my ff03 FWD gear diff before, last time I tried it in the tc I damaged the gears on closing the casing, so never ran it!

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I have only used the putty up to this point. But testing thiiner/different fluids is definitely on my to do list.
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Old 06-19-2011, 08:29 AM   #48
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I have only used the putty up to this point. But testing thiiner/different fluids is definitely on my to do list.
Hi

Have tried the 500K but that was not as good as FG locking grease for their stock largescale diff. Next on my list is putty
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Old 06-19-2011, 12:27 PM   #49
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Is it possible that some of the increase in performance is due to this setup being kinder to the front tires? Spool = more scrubbing = increased heat and wear.
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Old 06-19-2011, 08:00 PM   #50
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I was thinking of trying that myself. But as I understand it, cranking down the ball diff and trying to run it hard that way will reduce the life you get out of it. Not sure just where, but at some point you reach a point of diminishing return when your replacing parts too often.
It took me a long time (years, actually) before I got the hang of tuning a ball diff by feel.

The main thing to feel for is as you're cranking down the diff screw is to know when the diff spring has bottomed out. Once that has happened, you can't tighten any further. Keep going and you'll break the diff screw. Ask me how I know.

Assuming the diff is assembled and working properly, tighten the diff screw slowly and you should feel a very linear resistance as you turn the screw and the diff spring compresses. Once you feel the resistance ramp up suddenly, Stop! That's the spring fully compressed. Now back up the diff screw 1/4 turn. That leaves a tiny bit of slack in the diff spring to cope with shocks and other stresses that pass through the diff.

Note that as 99% of diff screws tighten into a nylon locknut, the ramping up of resistance to be felt as the spring hits full compression can be disguised by the resistance required to turn the screw into the locknut. Only experience can guide you here.

You can run the ball diff at maximum tightness with the diff spring absolutely, fully, compressed, but there is the risk of drivetrain shocks breaking the diff screw and causing your diff to come apart mid race. Again, ask me how I know. That's why I advocate releasing the spring tension by 1/4 turn from maximum. That's the absolute maximum safe limit of tightness on a ball diff.

Ultimately, a really tight ball diff needs to be built up using extremely thick, gummy, goopy grease to provide the tightness. Tamiya Anti-wear grease does the trick for me. It is very resistant to being flung off. I pack the trust bearings full of it, and also the main diff balls and rings too. yes Anti-wear grease does work on the diff rings. The thick grease also offers better wear protection for the trust bearings/washers and diff balls because you are squeezing them so tight. Weak, runny grease will not protect from wear when the components are under so much compression stress. From my experience, on a tight diff, the trust bearing washers are even more prone to wear than the actual diff rings.

Furthermore, Anti-wear grease seems to have a funky property that works well in a tight front ball diff application. In suspension damping terms, it seems to have soft slow bump damping but hard fast bump damping. Even though the diff is very tight, rotating it slowly will still allow reasonable diff action. But if you try to apply a quick shock load to the diff (i.e., rotate it very quickly and suddenly), the grease seems to 'bind/pack up' and become more resistant to movement.

That means when cornering off throttle, the front diff works reasonably well as the left and right wheels are allowed some degree of difference in rotation. But once you apply throttle, the diff binds up. Not hard enough to lock up like a spool, but just tight enough.

I haven't had any experience with other types thick grease, but if you do, I would like to hear of your experience.

This is how I do it, and it works. No sense in getting back to geared diffs. That feels like tech from the early days of RC, fit for the Tamiya Racing Master 1/12 on road cars. Remember how in the late 1980s ball diff were all the rage and if you had a geared diff (sealed or otherwise) in your RC car you were a dinosaur? Why are we going the dinosaur route again?
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Old 06-20-2011, 12:00 AM   #51
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is there any thing more commonly available thats like the putty ?
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Old 06-20-2011, 01:04 AM   #52
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is there any thing more commonly available thats like the putty ?
try blu tack but mix a little silicone oil with it to keep it moist.
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Old 06-20-2011, 01:48 AM   #53
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try blu tack but mix a little silicone oil with it to keep it moist.
cool thanks, i wondered if blue tack was similar
does the putty lock the diff or just make it hard to turn ?
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Old 06-20-2011, 03:04 AM   #54
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Remember how in the late 1980s ball diff were all the rage and if you had a geared diff (sealed or otherwise) in your RC car you were a dinosaur? Why are we going the dinosaur route again?
Because other technology has moved further forward, and a ball diff is no longer up to the task of providing the best possible performance. Pretty much all big events these days are being run and won with gear diffs. I think that speaks volumes about what is best.
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Old 06-20-2011, 06:52 AM   #55
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Anyone used Silly Putty as an alternative? It is sold everywhere and usually for under $2 bucks.

http://en.wikipedia.org/wiki/Silly_Putty
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Old 06-20-2011, 08:33 AM   #56
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Because other technology has moved further forward, and a ball diff is no longer up to the task of providing the best possible performance. Pretty much all big events these days are being run and won with gear diffs. I think that speaks volumes about what is best.
They say the same thing about 40-50-and 65c rating batteries, but there are still big races won with the "slower" 25C batteries, thus providing evidence the main rule is...there are no certain rules.

I'm going to build the stiff version ball diff. I am good at building ball diffs, get a reliable 40-50 runs per build, and have plenty of parts for prob. 2 seasons. I assume using the ceramic balls is not a great idea for building the tight version front diff as well.

And BTW my last time out, TQ and A main winner was running a tight ball diff, against a pretty strong field.
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Last edited by Verndog; 06-20-2011 at 08:46 AM.
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Old 06-20-2011, 08:43 AM   #57
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mite be ball diffs were good when brushed motors and nimh were used,but know we have a lot more power,the reliability and less maintenance of a gear diff is probably better than a slight gain in efficiency and weight saving of a ball diff.
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Old 06-20-2011, 08:58 AM   #58
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Thus providing evidence the main rule is...there are no certain rules.
Quoted for truth!

Interesting how RC manufacturers market their stuff. What's old is new again.

I hated ball diffs in 1987. They were fiddly, hard to tune, and a general pain in the behind. But every magazine was trumpeting how great they were and how they have made geared diff obsolete. RC car Action made it very clear that if you didn't use a ball diff, you're out of fashion, out of step and a no-hoper on track.

Took me years to learn how to 'feel' the tune of a ball diff.

Now we're back a full circle.
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Old 06-20-2011, 09:03 AM   #59
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Quote:
Originally Posted by Verndog View Post
They say the same thing about 40-50-and 65c rating batteries, but there are still big races won with the "slower" 25C batteries, thus providing evidence the main rule is...there are no certain rules.

I'm going to build the stiff version ball diff. I am good at building ball diffs, get a reliable 40-50 runs per build, and have plenty of parts for prob. 2 seasons. I assume using the ceramic balls is not a great idea for building the tight version front diff as well.

And BTW my last time out, TQ and A main winner was running a tight ball diff, against a pretty strong field.
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If you use high quality ceramic diff balls then this should not be a problem, but I can tell you that you probably won't like the ball diff up front. I was doing some testing and tried it the other day. It helped very little a corner entry and was much slower coming out. I would rather the car plow a little coming in and pull coming out. I have tried 500K up front and like the way it felt, but all of this as on carpet. I have never tried Putty, and making the spec r gear diff fit in the TC6 is no easy task with simply a dremel. I know you have access to the right equipment so it will be easier for you. I am really happy with the spool/Ball diff on carpet and will run that until the AE version of the gear diff get released.
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Old 06-20-2011, 09:04 AM   #60
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And BTW my last time out, TQ and A main winner was running a tight ball diff, against a pretty strong field.[/QUOTE]

Really
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