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Gearing question

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Old 06-27-2019, 06:05 AM
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Default Gearing question

I'm looking to set up a TC7.1 to run VTA, I'll be running a TSR 25.5T motor with about 50* of timing, Hobbywing XR10, Blinky mode ESC Looking at getting version 3.0, but currently, have a 1.0. Not The One either. The track is about 90' x 40', a sweeper into a straight and some pretty tight turns. I've read that a 4.0 to 4.2 is the sweet spot for the FDR. My question is, what is the difference if I run a 100t spur and 50 pinion (internal is 2.0) to get to a 4.0 versus a 96t spur and a 48t pinion. Would the smaller spur and pinion be less mass for the motor to spin, equalling better acceleration? Or would 4 teeth less on the spur and 2 on the pinion not matter? Or, is FDR, FDR no matter how you get there.

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Old 06-27-2019, 06:32 AM
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Originally Posted by Red5Ltr View Post
I'm looking to set up a TC7.1 to run VTA, I'll be running a TSR 25.5T motor with about 50* of timing, Hobbywing XR10, Blinky mode ESC Looking at getting version 3.0, but currently, have a 1.0. Not The One either. The track is about 90' x 40', a sweeper into a straight and some pretty tight turns. I've read that a 4.0 to 4.2 is the sweet spot for the FDR. My question is, what is the difference if I run a 100t spur and 50 pinion (internal is 2.0) to get to a 4.0 versus a 96t spur and a 48t pinion. Would the smaller spur and pinion be less mass for the motor to spin, equalling better acceleration? Or would 4 teeth less on the spur and 2 on the pinion not matter? Or, is FDR, FDR no matter how you get there.

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Red5Ltr
FDR is FDR. The only other difference is that the motor will be further forward or backwards, affecting weight distribution.
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Old 06-27-2019, 09:46 AM
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FDR is FDR, but 4.0 for vta? I would say 2.8-3.2
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Old 06-27-2019, 09:59 AM
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Originally Posted by rcguyfpr View Post
FDR is FDR, but 4.0 for vta? I would say 2.8-3.2


When I switched to the Motiv 25.5. I asked them directly. Since they have hosted races at where I was planning to run at. Unfortunately track is no longer in business
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Old 06-27-2019, 10:57 AM
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4.2fd sounds crazy high for a 25.5 motor. It’s going to be crazy slow. Typical 17.5t motors run about a 4.0 final drive. 21.5t motored run 3.5 to 4.0 final drive. I would think a 25.5 turbo motor should run under a 3.5 final drive.
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Old 06-27-2019, 11:10 AM
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Originally Posted by riceball777 View Post
4.2fd sounds crazy high for a 25.5 motor. Itís going to be crazy slow. Typical 17.5t motors run about a 4.0 final drive. 21.5t motored run 3.5 to 4.0 final drive. I would think a 25.5 turbo motor should run under a 3.5 final drive.
My 17.5 is at 4.0. Think track closed before I went above 4.0 on the VTA. I had more then a few that said 4.2 was too much. That way I saved the response.
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Old 06-27-2019, 11:14 AM
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Originally Posted by Red5Ltr View Post
I'm looking to set up a TC7.1 to run VTA, I'll be running a TSR 25.5T motor with about 50* of timing, Hobbywing XR10, Blinky mode ESC Looking at getting version 3.0, but currently, have a 1.0. Not The One either. The track is about 90' x 40', a sweeper into a straight and some pretty tight turns. I've read that a 4.0 to 4.2 is the sweet spot for the FDR. My question is, what is the difference if I run a 100t spur and 50 pinion (internal is 2.0) to get to a 4.0 versus a 96t spur and a 48t pinion. Would the smaller spur and pinion be less mass for the motor to spin, equalling better acceleration? Or would 4 teeth less on the spur and 2 on the pinion not matter? Or, is FDR, FDR no matter how you get there.

Thanks

Red5Ltr
There are many ways to get the same FDR. Check a gearing chart. The one I use has 12 different combinations to get same FDR. And there was a difference. I first started with 48p. But car always seemed to be itís limit. Once I change to 64p it felt different. Like wasnít a rev limit 10 feet into the straight
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Old 06-27-2019, 12:45 PM
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Originally Posted by riceball777 View Post
4.2fd sounds crazy high for a 25.5 motor. Itís going to be crazy slow. Typical 17.5t motors run about a 4.0 final drive. 21.5t motored run 3.5 to 4.0 final drive. I would think a 25.5 turbo motor should run under a 3.5 final drive.
when I briefly raced vta I had my 25.5 revtech geared at a 4.19 and it was fast! I started at 3.6 and the car kept getting faster and faster every time I dropped a tooth on the pinion. I would check lap times and temps to set up the gearing . Go with the gearing that yields true fastest laps not the one that sounds the best .
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Old 06-28-2019, 07:59 AM
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Originally Posted by Red5Ltr View Post
I'm looking to set up a TC7.1 to run VTA, I'll be running a TSR 25.5T motor with about 50* of timing, Hobbywing XR10, Blinky mode ESC Looking at getting version 3.0, but currently, have a 1.0. Not The One either. The track is about 90' x 40', a sweeper into a straight and some pretty tight turns. I've read that a 4.0 to 4.2 is the sweet spot for the FDR. My question is, what is the difference if I run a 100t spur and 50 pinion (internal is 2.0) to get to a 4.0 versus a 96t spur and a 48t pinion. Would the smaller spur and pinion be less mass for the motor to spin, equalling better acceleration? Or would 4 teeth less on the spur and 2 on the pinion not matter? Or, is FDR, FDR no matter how you get there.

Thanks

Red5Ltr
I played with different size spurs in VTA with my Awesomatix shaft car.. 86 worked the best for me. FDR should be FDR.. but when I went larger spur and pinion I was slower.
As for gearing.. With the original TSR 25.5 I ran 46* on the motolyser with a 4.5-4.6 FDR with really big ballooned tires on the same type track.
With the TSR V3 I ran 57* on the motolyser with a 4.99 FDR with the same ballooned tires.
Make sure you have a good fan on it
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Old 06-28-2019, 08:15 AM
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Originally Posted by rcguyfpr View Post
FDR is FDR, but 4.0 for vta? I would say 2.8-3.2
Not everyone races on big tracks like us Edmund. Lol
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