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Pinion gear help

Old 10-07-2021, 01:49 PM
  #1  
jraynes15
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Default Pinion gear help

Hey ya'll, new to forum and electric RC in general. I am in need of a pinion gear for a BLX 4074 5MM shaft for an electric conversion I am doing to an old 1/8 CEN Matrix TR Arena. The CEN has a 66t spur gear, but I'm not sure of pitch (or if it matters?). For some context, this will be mostly a light off-road basher. ESC is a HW Quicrun 8BL150 and my intention is to run 6S. I don't want heat to be an issue, so gearing down in lieu of some speed is okay. Any thoughts? Thanks in advance!

Last edited by jraynes15; 10-07-2021 at 01:51 PM.
Old 10-07-2021, 05:18 PM
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bill_delong
 
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not familiar with your specific chassis but generally most 1/8 buggies use MOD1 pitch and start out with 16T pinions, if you want to play it safe, maybe try to post your same question on RCTech, there's a wider range of folks with experience with the older cars over there. Another option is to download a copy of the manual which should give you a gearing chart as well.

Good Luck!
Old 10-08-2021, 08:03 AM
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jraynes15
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Originally Posted by bill_delong View Post
not familiar with your specific chassis but generally most 1/8 buggies use MOD1 pitch and start out with 16T pinions, if you want to play it safe, maybe try to post your same question on RCTech, there's a wider range of folks with experience with the older cars over there. Another option is to download a copy of the manual which should give you a gearing chart as well.

Good Luck!
Thank you for your help! The clutch bell from the nitro motor had a 13t pinion but I have no idea what pitch it is. I have a manual but haven't seen the gearing chart yet, I will try that!
Old 10-09-2021, 02:19 AM
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Feelin' FPV
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That's a great project car! 66 tooth spur gear? It's going to be hard to gear that down enough. Since you have to find brushless motor mounts any way have you considered using an off the shelf mount like Arrma or Kyosho that includes the centre diff mount integrated? Then you can use a 50 tooth spur to manage the gearing. Plus spares are easy to source. I'd be changing that whole centre diff and mount out.
Old 10-09-2021, 05:10 AM
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jraynes15
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Originally Posted by Feelin' FPV View Post
That's a great project car! 66 tooth spur gear? It's going to be hard to gear that down enough. Since you have to find brushless motor mounts any way have you considered using an off the shelf mount like Arrma or Kyosho that includes the centre diff mount integrated? Then you can use a 50 tooth spur to manage the gearing. Plus spares are easy to source. I'd be changing that whole centre diff and mount out.
Thank you! I have another fully functional Matrix TR Arena Nitro so it'll be cool to have both! Great point about the 66t spur, it never occurred to me that it might be too large. It's funny you mention those mounts because I ended up going up an Arrma center diff mount yesterday since it is the same bearing size as the diff on my Matrix. But from the sound of it I should go with the 50t spur instead. I just got 11t to 15t pinions too... no way to keep the 66? Or should I have gotten higher T pinions? I am on a bit of a budget, even though $30 for the Arrma dif is really nothing. Just trying not to piss off my wife too bad lol

Last edited by jraynes15; 10-09-2021 at 05:28 AM.
Old 10-09-2021, 06:51 AM
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jraynes15
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Reading up a bit it looks like the pinions I ordered are actually too low and would be undergeared... I should shoot for somewhere around 20t for a safe gear ratio from what I've seen. Opinions welcome!
Old 10-09-2021, 01:17 PM
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Feelin' FPV
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I was just about to suggest a 19 or 20 tooth pinion if you want to keep the 66 tooth spur. That'll give you around final drive ratio of around 15:1 which seems to be a good starting point.
i gotta link that might help with this. No. I'm too new to post links.
search for:
RC gear calculator . radiocontrolledinfo dot com

Old 10-09-2021, 02:16 PM
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jraynes15
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Originally Posted by Feelin' FPV View Post
I was just about to suggest a 19 or 20 tooth pinion if you want to keep the 66 tooth spur. That'll give you around final drive ratio of around 15:1 which seems to be a good starting point.
i gotta link that might help with this. No. I'm too new to post links.
search for:
RC gear calculator . radiocontrolledinfo dot com
Thanks for the feedback! I ordered a 19 and 20t pinion set before your post so I'm glad that you verified what I was thinking!

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