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Gabranth

Gearing Question

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I'm still unable to wrap my head around gear ratio so a question regarding to my current TD2 build. So the kit came with 70T spur gear and 17T pinion gear, instead of calculating it (since I don't know how) I look at official site and it list Gear Ratio = 10.71:1.

Now I'm using TBLM-02S 15.5T which in its product page says "Ideal for Buggies, Touring Cars with 6.0 - 8.3 gear ratios". Looking at chart online (from Yokomo not Tamiya but I hope it's the same) for 48P 70T spur gear to be at least getting to 8.3 I need 22T pinion.

So basic question is, what will I gain from following motor's recommended gear ratio and what will I lose from sticking to current default setup??

I haven't even test the car on ground, I don't need super top speed but I don't want to waste the power of that motor either. But more importantly, I don't want a wrong setup that can potentially damaged the motor and ESC.

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The lower the gear ratio, the higher the top speed, at the sacrifice of acceleration.

Not sure the internal ratio of the TD2, but with a 15.5T I'd think going to a 22T pinion wouldn't sacrifice too much acceleration, but will give you a higher top speed.

Bigger pinion/smaller spur = higher top speed

Smaller pinion/bigger spur = more acceleration

Depending on the motor, going too big on the pinion or too small on the spur can cause the motor to heat up, But I'd wait on other TD2 owners to chime in on what combos would cause that. Though I don't think 22T pinion and 70T spur would run hot on a 15.5T.

-RC Perspective

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Tamiya usually include a gear chart in the manual that tells you what gear ratios will fit, so use that.

Also the 6.0 recommendation will be for a touring car with smaller wheels, so aim for the 8.3 ratio.

You're more likely to damage the motor by gearing it too high (i.e. towards the 6), but if you gear it too low it will reach maximum revs too soon and you won't be able to enjoy the performance.

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Thanks guys, I understand more now. I found the chart in the manual (should have search there first). It listed 8.27:1 ratio when using 22T pinion, I think I'll go with that.

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Not quite answering your question but...

This is the app I use to do my gearing speed calculation. 

https://play.google.com/store/apps/details?id=redscrew.gearcalc

I worked out the reverse calculation to find out the IR, SI/P = FDR. S is spur, P is pinion and I is internal ratio. So in your case, 70I/17 = 10.71. Your I is 2.6. (which can be found online if you cannot be bothered with maths) 

Input that and all other info like tyre size, etc in and the app will tell you the top speed. 

For FDR, I work off this chart as a guide while picking my gears. 

JvVMFST.jpeg

15.5T is a rare (Tamiya only?) thing so it is not listed but for 17.5T and 13.5T, it recommend a FDR of 4.6 to 6.0. BUT that is for touring wheels, so you need to work out the % increase of your wheels over a touring car and increase the FDR accordingly. 

OR just ignore all the boring maths and go with what sosidge said, 8.3ish which is around what is correct. 😁

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11 minutes ago, alvinlwh said:

Not quite answering your question but...

This is the app I use to do my gearing speed calculation. 

https://play.google.com/store/apps/details?id=redscrew.gearcalc

I worked out the reverse calculation to find out the IR, SI/P = FDR. S is spur, P is pinion and I is internal ratio. So in your case, 70I/17 = 10.71. Your I is 2.6. (which can be found online if you cannot be bothered with maths) 

Input that and all other info like tyre size, etc in and the app will tell you the top speed. 

For FDR, I work off this chart as a guide while picking my gears. 

JvVMFST.jpeg

15.5T is a rare (Tamiya only?) thing so it is not listed but for 17.5T and 13.5T, it recommend a FDR of 4.6 to 6.0. BUT that is for touring wheels, so you need to work out the % increase of your wheels over a touring car and increase the FDR accordingly. 

This is why I keep giving up on gearing 😬

11 minutes ago, alvinlwh said:

OR just ignore all the boring maths and go with what sosidge said, 8.3ish which is around what is correct. 😁

now you’re talking my language 😂

  • Haha 2

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1 minute ago, GeeWings said:

This is why I keep giving up on gearing 😬

Hey, I am that boring maths geek! :rolleyes:

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7 minutes ago, alvinlwh said:

Hey, I am that boring maths geek! :rolleyes:

Nothing wrong with that. I think I’m just a boring geek who doesn’t get maths!

  • Haha 1

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So I've fitted 22T pinion just now. I'm still struggling with setting proper gear meshing but last time with 17T I found sweet spot where the rotation sounded smooth enough. But this time with 22T using similar tolerance I heard really bad high-pitch noise, like really unpleasant one that just get louder in full throttle. I went back and forth and in the end settled with looser setting that while in very slow speed sounding kinda rough but half throttle or more it turned into smoother one. I have no experience on what proper sound should be but that high-pitch noise really scares me. I will test how it feels on the ground later since my tire inserts still haven't arrived yet.

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This is what I ended up with. Sounds okay except at very low speed where it's kinda rough. This is my first brushless setup so I don't even know how they should properly sound. Any tighter than this and it will ended up with that aforementioned scary high-pitched noise.

20220730_195322.jpg

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It does look a little loose but will probably be OK. You want a small amount of backlash between the spur and pinion.

Where did you get the pinion? The tooth profile looks a little different to the spur. Are they both 48dp?

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36 minutes ago, Gabranth said:

The pinion is from Tamiya 54217 set and yes they're both 48p.

EDIT: the pinion is definitely 48p, but somehow the manual doesn't say anything about the included spur gear, just 70T. It has product code 51215 but annoyingly it doesn't say anything more

https://www.tamiya.com/english/products/51215/index.htm

It's a 0.6mod spur. Tamiya recommend their AV (0.6mod) pinions for use with the stock TD4 spur.

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So checking TD4 catalog 50357 does listed there but so does 54217 in TD2 catalog but maybe that's to be paired with 54219 spur that's also listed there. I found 50357 locally so I'll try my luck with that one.

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Reviving this thread because I have another problem, this time different type of car and situation. I put Super Stock RZ in a TT-01E with HW 1060 ESC and 2S Lipo. I replace the stock 19T pinion with 21T and well I got everything overheated in one run, ESC, battery connector, and the motor (with heat sink). I've heard that if both ESC and motor overheat, I'm overgearing it but is 21T really that much?

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4 hours ago, Gabranth said:

Reviving this thread because I have another problem, this time different type of car and situation. I put Super Stock RZ in a TT-01E with HW 1060 ESC and 2S Lipo. I replace the stock 19T pinion with 21T and well I got everything overheated in one run, ESC, battery connector, and the motor (with heat sink). I've heard that if both ESC and motor overheat, I'm overgearing it but is 21T really that much?

Funny you should say this as I have a TT01E truck that I took for it’s first race last night and I used the stock torque tuned motor, Tamiya esc with a 2s Lipo and 21t pinion and it got really hot too! Still did my 3 races with no drop in performance but the motor felt really hot to the point you couldn’t touch it!?! Would of thought they would be fine with a 21t pinion too. 

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If it's getting hot in continuous operation like a race but still working should be normal I guess.

In my case the ESC's overheat protection kicked off, so I can't do anything other than waiting for it to cool down. But it took so long to cool both ESC and motor. Was afraid of something like a short or binding causing it but I couldn't find any. I'm pretty sure a 1060 can handle a 2S powered Super Stock RZ, or at least I thought so.

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12 hours ago, Gabranth said:

If it's getting hot in continuous operation like a race but still working should be normal I guess.

In my case the ESC's overheat protection kicked off, so I can't do anything other than waiting for it to cool down. But it took so long to cool both ESC and motor. Was afraid of something like a short or binding causing it but I couldn't find any. I'm pretty sure a 1060 can handle a 2S powered Super Stock RZ, or at least I thought so.

My truck didn’t cut out and the esc didn’t feel too hot so it must be ok. I’ve got a hobbywing 1060 in my TT02 I also race with a 21 turn core rc motor and 2s Lipo with a 24t pinion and that doesn’t get too hot probably cooler than my truck. Is your 1060 genuine? I unknowingly bought a fake for my TT02 that caught fire in its first race!

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I believe so, it came in the usual box with the extra goods and everything. Also used in other car before, bashed around for quite a while without getting cut, although only ever use silvercan and Torque Tuned at most.

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If your motor is getting hot and you know your drivetrain isn't binding and running the correct pinion gear pitch, then I would just run the smallest pinion you have, drive 3-5 min, touch the motor housing for heat, it it doesn't get hot, keep running it for another 5 min, touch it again.

If still only warm to the touch, go 2 teeth larger on the pinion and try again.  If your motor gets hot enough you can't hold your finger on it for more than 3 sec, then your pinion is too big.  That is the 3 second rule, very rudamentry, but probably the best way to gear your brushed motor car.  

Recommended gear ratio is only a reference, how you drive and where you drive will GREATLY affect the proper gearing for your motor and car.  GL!!

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Yeah I ran the car again on Sunday with 19T pinion, the motor did get quite hot but in reasonable way. ESC is perfectly fine, even when it get warmer after continuous use in full throttle it cooled down easily. Last time the thing was still burning hot even after I arrived back at home with everything disconnected. It's a miracle that ESC is still alive.

However there are still many factors to this case, the surface back then were dirtier than the one I tested on Sunday. I had a hard time keeping the car straight. Probably the wheel slipped a lot and that contributed to excessive heat.

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Does the recommended gear ratio stated in the manual takes into consideration internal ratio?

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reading this thread I wonder.

for a new tt02b out of the box with 17T pinion and 70T spur. should I start playing to achieve lots of speed and lots of tourqe? for example, use a 20T pinion with 68T spur  for speed and a lightly tuned motor to compensate on the tourque department (its 3x the sliver can tourque)

what do you guys think? anyone doing the same?

thanks!

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On 1/16/2023 at 3:00 PM, gkatz said:

for example, use a 20T pinion with 68T spur  for speed and a lightly tuned motor to compensate on the tourque

It had been tested somewhere that RPM beats torque, probably a video somewhere, I cannot remember. So using a smaller pinion with a faster motor is actually better for top speed. Download the app I linked and work out a few numbers to seen how it goes, in paper first at least.

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