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TurnipJF

Noisy Thundershot drivetrain?

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As some of you know, I have restomodded a Thundershot recently.

When I first ran it  I found the drivetrain very noisy, however I was expecting it to bed in after a battery or two and quieten down a bit.

This has not happened.

I have opened both gearboxes to double check that I put them together correctly, and everything is as it should be as far as I can see. However the gears that fit on the shafts taking power to and from the prop shaft seem very tight against their mates in the gearbox itself. You know, the ones under the little covers that attach to the sides of the gearboxes? It is this tight mesh that seems to be the source of much of the noise.

Is this just a Thundershot thing, or is there an issue here? If there is an issue, is it a common one and is there a fix for it? I have tried both the stock thrust washers and proper thrust bearings as well as ordinary ball bearings in the thrust washer positions and none of these make any difference.

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i think it really is just a noisy drivetrain (compared to my other rc's anyway). we were actually joking the noise is a good ploy to scare kids out the way.

however i've not really noticed how tight the transfer case mesh is. at least mine seems just fine.. if you do manage to quieten it down, do share....

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Mine is very noisy too, and not very free. Sounds a bit better than yours though. Maybe try loosening the screws on the cover a quarter turn? Try and give the gears a little more space. 

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It’s usually caused by small bits of excess material from the sprue on the bevel gears That drive the centre propshaft

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3 hours ago, TurnipJF said:

I have opened both gearboxes to double check that I put them together correctly, and everything is as it should be as far as I can see. However the gears that fit on the shafts taking power to and from the prop shaft seem very tight against their mates in the gearbox itself. You know, the ones under the little covers that attach to the sides of the gearboxes? It is this tight mesh that seems to be the source of much of the noise.

I dealt with an issue like this about 11 years ago with the Fire Dragon re-re (same chassis). Somewhere there's a thread on it. The bevel gears in the front gearbox immediately after prop shaft were not molded correctly. Neither were the replacements I bought. I studied the gears closely and found a lot of distortion and lumpiness at the roots of the gear teeth. It produced a noticeable tight spot in the rotation. It made weird clicking sound when running. My first attempt at filing the gears didn't work. I went after it again, even trimming some of the lumps out with a hobby knife. Eventually, I got them to quiet down. I was a bit miffed at the time. I recall it being the first Tamiya I bought new that had a defect.

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48751327086_57770f64ce.jpggear1 by Scott Weiland, on Flickr

Here's a picture of one of the gears and what the poor molding looked like. If you pull the prop shaft out and run it and the noise goes away, its likely in the front gearbox.

  • Sad 1

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Wow I've never had a gearset like that!

The gear packs I have left NIP are 2 x original and 1 X rere when I last looked.

Maybe one of the reasons the FD didn't hang around so long if something happened to mold (especially after spending a lot of effort on the rere manual)

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Moulding flash and/or poorly moulded gears were my first thought, and I did find a few dodgy spots that I sorted out during initial assembly. I also found that an older gearset was a little quieter than a new one. However even a well worn-in gearset thoroughly inspected for imperfections still meshes tightly and noisily. 

Glad to know that mine is not the only noisy 'Shot. Maybe after a few hundred battery packs it will quiet down a bit. In the meantime, I'll stop worrying about it. 

Thanks for all the feedback!

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I added a shim to give a bit more space.  

I forgot what size.  0.3mm or 0.4mm, I think. 

That added a tiny bit of clearance, so it's much less quiet.  

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9 hours ago, TurnipJF said:

Moulding flash and/or poorly moulded gears were my first thought, and I did find a few dodgy spots that I sorted out during initial assembly. I also found that an older gearset was a little quieter than a new one. However even a well worn-in gearset thoroughly inspected for imperfections still meshes tightly and noisily. 

Glad to know that mine is not the only noisy 'Shot. Maybe after a few hundred battery packs it will quiet down a bit. In the meantime, I'll stop worrying about it. 

Thanks for all the feedback!

Steel pinion is also a little noisier than aluminium one but that's a price worth paying!

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1 hour ago, taffer said:

Steel pinion is also a little noisier than aluminium one but that's a price worth paying!

 Agreed!

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