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Old 05-06-2011, 08:02 AM   #1
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Default What is the ideal TC internal ratio?

Hi All

I am modifying a car, and at the moment am looking what pulleys to fit on it.

What is the ideal IR for a brushless TC?

Also does Pulley size matter when achieving a IR? i.e if the IR of 2 was ideal, would you be better to use a 32t diff pulley and a 16t layshaft, or a 40t diff pulley and a 20t layshaft pulley.

Thanks
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Last edited by Qatmix; 05-06-2011 at 08:16 AM. Reason: I meant IR not FDR
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Old 05-06-2011, 08:11 AM   #2
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there is no such thing, its is motor dependent, most brushless motors operate in the 3.0-8.0 fdr range, how the pulleys are split do not make a difference as long as front and rear achieve the same ratio.
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Old 05-06-2011, 08:11 AM   #3
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It's difficult to answer with the information that you've provided. There are so many things that factor into what the proper gearing should be. Motor choice, track surface, track length, track layout, etc. To answer the second part of your question, my preference is to use larger pulleys. With more teeth engaging the belt, there's less stress on the belt, less likelihood to skip, and it's slightly more efficient.
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Old 05-06-2011, 08:23 AM   #4
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I see you updated to IR, still the same argument, xray has this option, I don't know anyone that could prove one was faster, some felt it was "punchier" but that was just to justify the $100 they just spent, lol. I believe the option is more useful to position the motor relative to the spur.
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Old 05-06-2011, 08:23 AM   #5
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ahem I actually meant Internal ratio. (Just been to the pub for lunch)
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Old 05-06-2011, 08:27 AM   #6
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The internal ratio is irelevant, the motor only cares about the overall drive ratio. Manufacturers who put stuff on their website about having the "ideal internal ratio" are talking nonsense.

What does matter is the size of the pulleys. The original cyclone had 16t layshaft pulleys and these would wear out quickly and chew the belts up. My Yokomo BD and TC6 have 20t layshaft pulleys and never have any issues with belts and pulleys.

I think ideally the bigger the pulley the better, but this gives issues with space and diff height, so there is a limit. The 40t diffs on the TC6 already sit in slots in the chassis, so you couldn't go any bigger without raising the diffs and comprimising the handling.

If I was building a car I'd go with 20t layshafts and 40t diffs. The two cars I've had with this setup have been faultless on the transmissions.
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Old 05-06-2011, 12:52 PM   #7
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Touring cars with dynamic ESC timing on carpet tracks (17.5 motor) aim for a 5.5 - 7 FDR... depending on track conditions, traction, etc
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