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What size pinion for Tamiya Hotshot with Tamiya Super Stock BZ Motor? .........and should it be Steel or Alloy?

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What size pinion for Tamiya Hotshot with Tamiya Super Stock BZ Motor? .........and should it be Steel or Alloy?

Thank you in advance.

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Where are you running it? I find a silvercan with 15T in my Boomerang gets hot after 20 odd minutes on grass. If you ran on gravel or tarmac it wouldn't be so bad though.

I would expect you'll end up at 13T or 14T but could be wrong

I buy either the coated or hardened aluminium pinions or steel. I avoid the Tamiya aluminium ones as they wear quickly.

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Thanks for the replies.

Will be run on a mixture of grass and tarmac.

The manual states and supplied with 13 or 15 for the GT Tuned.

But options and sold separately a 16 or 17 if wanted. So unsure what would be best for the Super Stock BZ and how the "motor set plates" would work if went larger tooth.

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7 hours ago, Tamiya1973 said:

Thanks for the replies.

Will be run on a mixture of grass and tarmac.

The manual states and supplied with 13 or 15 for the GT Tuned.

But options and sold separately a 16 or 17 if wanted. So unsure what would be best for the Super Stock BZ and how the "motor set plates" would work if went larger tooth.

The plates allow you to fit from 13T to 17T so thats not a problem. What pinions do you have? If I read that right you have 13t and 15T. I would start with 13T, run for a few minutes and then check how hot the motor is. If its cool, switch to the 15T. If its hot, don't go up. I use 15T for a silvercan and 17T for 13.5T brushless, they're the only ones I've got.

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2 hours ago, Jonathon Gillham said:

The plates allow you to fit from 13T to 17T so thats not a problem. What pinions do you have? If I read that right you have 13t and 15T. I would start with 13T, run for a few minutes and then check how hot the motor is. If its cool, switch to the 15T. If its hot, don't go up. I use 15T for a silvercan and 17T for 13.5T brushless, they're the only ones I've got.

Thanks for reply. 👍

 

 

 

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Check your FDR in your manual. I run a TZ (effectively the same motor) at 7.20 with a heatsink no problem. Of course this will also depend on the weather conditions you run yours in. 

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30 minutes ago, alvinlwh said:

Check your FDR in your manual. I run a TZ (effectively the same motor) at 7.20 with a heatsink no problem. Of course this will also depend on the weather conditions you run yours in. 

What is FDR? 7.20 with heatsink? Sorry, not an expert on these things, so confused.

Regards

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6 minutes ago, Tamiya1973 said:

What is FDR? 7.20 with heatsink? Sorry, not an expert on these things, so confused.

Regards

Check the numbers in your instructions, smaller numbers = hotter motor. More teeth pinion = smaller numbers. 

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11 minutes ago, alvinlwh said:

OK I had a quick look online and found your manual. The FDR numbers listed are:

13T - 10.043

14T - not listed? 

15T - 8.704

16T - 8.16

17T - 7.68

My TZ's instructions list a recommended gear ratio of 6.5 - 8.1, and I believe that the BZ and TZ are effectively the same., so you should aim for a FDR within that range, so 17T, or 16T is quite close. 

Note that there is no harm to the motor going smaller on pinion size (bigger FDR number), you will just get more acceleration but less top speed. I actually went smaller as it was impossible to control at 17T for me. 

Really appreciate you looking into this. 😎

 

Was thinking of either going for the 13 or 15 which is supplied in the kit. As you say from your calculations I should go with 16 or 17. I was just concerned about overheating if I went too high.

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18 minutes ago, alvinlwh said:

OK I had a quick look online and found your manual. The FDR numbers listed are:

13T - 10.043

14T - not listed? 

15T - 8.704

16T - 8.16

17T - 7.68

My TZ's instructions list a recommended gear ratio of 6.5 - 8.1, and I believe that the BZ and TZ are effectively the same., so you should aim for a FDR within that range, so 17T, or 16T is quite close. 

Note that there is no harm to the motor going smaller on pinion size (bigger FDR number), you will just get more acceleration but less top speed. I actually went smaller as it was impossible to control at 17T for me. 

The TZ is marketed for onroad isn't it? So those recommended FDR is based on normal touring car sized wheels which are a lot smaller than a buggies wheels. FDR is only the ratio between the motor and the wheel hexes turning, so the size of the wheels affects it (thats why a Lunchbox has an FDR of 18 or something, because of the giant wheels making up for it)

A 17.5T touring car runs an FDR of about 4, but a 17.5T buggy runs about 6 (in 4wd, 2wd would be 5.5ish).

38 minutes ago, Tamiya1973 said:

What is FDR? 7.20 with heatsink? Sorry, not an expert on these things, so confused.

Regards

FDR is the final drive ration. Its calculated by spur / pinion x internal ratio.

Because wheels affect it, some people use rollout (especiakky for foam tyres which wear down and get smaller) which also factors the wheel diameter in.

Internal ratio is fixed and you are usually told this in the manual. In cars like the Hotshot it doesnt really matter as you only have 5 pinion options, in a modern racer (or a TT02 with high-speed gearset and YR motor mount) you have unlimited options as you can chage the spur and pinion to anything you like. 

A smaller FDR is higher geared so less acceleration, more top speed, and bigger FDR is lower geared, so more acceleration less top speed.  

However, it doesn't always work like that, especially with brushed motors. You need them operating at their best efficiency, so if you gear too high it may never reach its peak rpm and actually be slower than if you drop the gearing. Brushless have a lot more torque so a brushless motor will almost always be faster with a bigger pinion, but you can easily overheat it and ruin it.

Generally, less motor turns means higher FDR, and more motor turns lower FDR.

The best way to manage it (as motors are expensive, you don't want to cook too many) is to start conservative and then check the motor temperature every few minutes until you're satisfied it can safely run the whole time without overheating. Also, most recommendations are based on 5 or 6min races, but you can easily run for 20 - 30min with modern batteries, so keep an eye on it for a whole run, not just the first couple of minutes.

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Thanks for reply ⬆️

I won't be running lipo batteries. This should help reduce heat. Just normal 5000 batteries. 

Still in two minds whether to go with the 13 or 15 with the BZ motor.

Thanks

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1 hour ago, Tamiya1973 said:

When you say manual. Do you mean the kit manual?

Thanks again

Page 5, step 5 - Attaching motor has all the numbers except for 14T pinion. @Jonathon Gillham said is right, I managed to find a picture of the BZ box and it is 9 - 11, so 13 or 14T is the right pinion for you. 

 

I do run mine on lipo and FDR of 7.2 but I have a heat sink (that do work) installed. 

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6 minutes ago, alvinlwh said:

Page 5, step 5 - Attaching motor has all the numbers except for 14T pinion. @Jonathon Gillham said is right, I managed to find a picture of the BZ box and it is 9 - 11, so 13 or 14T is the right pinion for you. 

 

I do run mine on lipo and FDR of 7.2 but I have a heat sink (that do work) installed. 

👍

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