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Old 07-02-2008, 04:48 AM   #16
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Wonder if the CORR guys have tried IRS and determined they don't handle as well? Or have they always used live rear axles? As pointed out previously, offroad RC has, and went to IRS. So did RC touring cars, and those guys still use live when required by rules, 12th and Pro-10. Just curious, I don't know. I would suspect that some of it is for durability reasons, those CORR, and I believe related Baja guys are tossing a lot of weight around. That is one of the main reasons typically for a live axle setup, in addition to cost and load carrying capacity (maintains geometry under varying loads). And our rock climbing buds, as it essentially eliminates tire scrub. If not, perhaps this is an excellent window for someone to come in with something different and clean up.

Back to the differential issue, don't our Nitro buddies(?) load the diff up with different viscosity fluids to tune the diff action? But in general they don't lock the diffs do they, well at least the rear axle anyway? I've tried the locked diff back in the six gear no slipper days as an emergency repair, it didn't work too well for me. But again that could just be a lack of driving skill....

Last edited by Dave H; 07-02-2008 at 06:35 AM.
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Old 07-02-2008, 06:50 AM   #17
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Not sure what this means in the scheme of you boys' overblown discussion, but it seems to me that if it worked for our purposes which differ so much compared to what they do in CORR or 1:1 racing that I think the factory boys would have done it or tried it long ago. Since that's not the case, in addition to RC cars and trucks working so much better now compared to the early days, it would be my educated guess that it would work like doo-doo.
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Old 07-02-2008, 08:52 AM   #18
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Well Gentlemen,
It seems I'm not the only one with this idea. My racing buddy Jonny Scherer is the one whose T3 we did the mod to. He was (lost his sponsor this season...not due to his driving) a sprint car driver and raced 1/4 midgets before that (National champion 1/4 midget/5th midwest series 2007). That's where the idea came from. With a locked diff the T3 puts huge amounts of power to the ground. So much that we are worried the slipper clutch will melt at the track test tonight. The straight line accelleration in the backyard was awesome. With a 10.5 we could pull wheelies on grass at 3/4 top speed. I'm thinking we may have to run looser rrear tires on the track to keep the front wheels down.
I'll keep everyone updated.
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Old 07-02-2008, 09:08 AM   #19
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fyi you can get a 2.6 gear diff for the GT if you wanted one. its called the kryptonite transmission available from Chris at Bumps and Jumps.. i dont know if the whole case drops in on existing screw holes or not. this wouldn't work in stringcheese's project without modding up a whole new chassis and such but it's cool to see people doing all sorts of things. that's part of what the hobby is about.

String, if its not the slipper, it will be an internal gear or wheel hub. slipper is easier to replace
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Old 07-02-2008, 09:16 AM   #20
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Quote:
Originally Posted by Dave H View Post
You're close, but don't forget my Mustangs! Which are for 2 reasons, cost and drag racing. Well, only cost in my case, I haven't tripped the lights for nearly 30 years myself. And that was usually only with one driven wheel.
Yep I forgot about the Mustang. They are popular in drag racing but then the cars don't turn. In an IRS type setup you get to play with all the allignment settings.

Back to the OP, I don't think that a locked diff will work out that well in a dirt track setup, Get that diff setup just right and things will be happy....just like in a real race car.
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Old 07-02-2008, 09:19 AM   #21
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We're not too concerned about much. We're just experimenting. We have a nice rebuilt diff ready to throw in when our experiment fails.
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Old 07-02-2008, 09:21 AM   #22
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Do you want:
1. the suspension geometry of live axle AND
2. the low unsprung mass advantage of IRS?

Try this!!! http://en.wikipedia.org/wiki/De_Dion_tube
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Old 07-02-2008, 09:48 AM   #23
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^^^^
GOOD READING
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Old 07-02-2008, 11:52 AM   #24
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no comparision between the two. If we could run a IRS in out super late model we would have one in tomorow. That would be sweet...
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Old 07-02-2008, 01:56 PM   #25
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Quote:
Originally Posted by STRINGCHEESE View Post
We're not too concerned about much. We're just experimenting. We have a nice rebuilt diff ready to throw in when our experiment fails.
If you're not too concerned, then why did you bother asking? If your rationale leads you to the conclusion that wheelies is a good thing, then go for it. Otherwise you're backwards-engineering a tranny, and your idea would put you in about a 1981 era RC.
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Old 07-03-2008, 08:17 AM   #26
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Well, here's the results.

Straightline power is crazy.
Truck turned ok at high speed and pushed too much at low speed.
Much more stress on engine.
Much more stress on tranny.
much more stable on launch and out of turns, so much more it's not even comparable. really made a diff look bad in these areas.
Braking was more stable.
Drifting an rc truck in dirt proved to be difficult.
Could a race truck work well with a live axle? IMO no. Would be good in bashers though.

All in all, experiment was fun and an educational tool for my young friend who didn't quite understand why we needed diffs.
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Old 07-03-2008, 08:46 AM   #27
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straight-line power is static and has to be exactly the same unless you were running the diff ridiculously loose
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Old 07-03-2008, 02:24 PM   #28
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Good for you for trying something to understand it better - that's how we learn. The results were pretty much as I would have expected, though...
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Old 07-22-2008, 04:47 PM   #29
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Thought this was interesting, from the Associated tease of their upcoming CORR truck:

Anyone ever run a live axle?-3.4.300.jpg
A crossed-up Ricky in his Pro-2 headed into the sweeper. Pro-2 rules requires a live rear axle making them very tricky to drive.
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Old 07-22-2008, 06:20 PM   #30
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Quote:
Originally Posted by Dave H View Post
A crossed-up Ricky in his Pro-2 headed into the sweeper. Pro-2 rules requires a live rear axle making them very tricky to drive.
...but Pro-4 doesn't require them...and I know that at least one of the top Pro-4 and Pro-lite builders wouldn't run IRS even if he could. Like I said, he was wondering why we don't run a live axle in r/c. It looks like they require a spool in Pro-4, but I couldn't find where they specified a live axle.
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