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Old 06-23-2014, 10:31 PM   #1
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Default 21.5t Touring car gearing issues. Help!

Having touring car gearing problems here... help!

I got a set of YR 64p pinions; a 47 - 52 tooth incremental set which would give me a good spread of gearing to achieve around a 3:1 FDR on a 75T spur on my TCXX.

The 75t 64p spur arrived from AMain Hobbies today. I stripped the top deck, installed it, but now the problem is the motor won't slide far enough rearwards for the gears to mesh.

I couldn't fit the same teeth gears in 48p since a) pinions in that range aren't available, and b) even if they were, they would be physically too big as would the spur be so the motor would have the opposite problem - slots not long enough to mount the motor far enough forwards.

Any ideas what sort of teeth spur I should be looking at, and in what pitch?

According to my gearing app, I could try a 65t spur in 48p which would be a fair bit bigger diameter, bit I'd then need a 42t pinion, which in 48p flavour is going to be a whole lot bigger than its 64p counterpart. Would it even fit?

I also have a 75t spur in 48p, which is quite big, but again, finding spurs up to 52t in 48p to play with FDR is impossible.

Any thoughts?

Cheers - Rob
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Old 06-24-2014, 03:09 AM   #2
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Running USGT (21.5) at out local carpet track a 52-96 with a 1.9 drive is a typical gearing combo we use with just about any motor (IE. Team Scream, Shuurspeed, Trackstar..).
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Old 06-24-2014, 03:47 AM   #3
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I have solved similar problems with a TA05 by changing center pulleys and diffs to give another internal ratio. Took a lot of belt checking, but doable.

If this is not an option, you need to break out the callipers and measure some things, such as how much room there is between the motor shaft and spur shaft when the motor is closest to the spur. With that distance in hand, you need to find a spur-pinion pair that will give you the desired ratio.
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Old 06-24-2014, 09:21 AM   #4
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Can't you just use a larger 64p spur gear in the 84-92t range which is more typical for gearing like that? In a Xray T4 a 75t spur would be too small for most gearing in that range not allowing the pinion and spur to mesh just as you have found with your HB car.
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