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Hornet88

2016 Kyosho Optima gear ratio questions...

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Hello All,

First time posting, so apologies if I err in some way. My question is about calculating the final drive ratio on a 2016 Kyosho Optima. They list the stock FDR as 9.24:1. The spur gear is 61t; pinion is 25t. They also sell an optional spur gear for brushless setups that is 51t, and they then recommend using either 30, 31, 32t pinion gear, which puts the final drive ratio at 6.24:1 (if using the 31t pinion). Now that just seems like a massive drop in the gear ratio, and wonder if anybody has ever done anything similar on this or other similar vehicles. 

Another thing that had me scratching my head is- how is their FDR calculated? I spent a badword of a lot of time on line reading different methods of calculating. I have tried running the numbers with the internal belt-drive pulley, diff gear, final pinion (internal), counter gear, and of course the outboard spur and pinion. No matter what I do, I can not replicate their claimed ratio specs. 

If anybody could kindly offer some advice, I’d be grateful. 

Many thanks,

Ryan 

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Solved it, I think...

diff/final pinion (53/32) * counter/counter pinion (48/21) * spur/pinion (61/25). So that comes out to 9.237. Call it 9.24. I didn’t realize that I needed to divide the counter pinion into the counter gear and then multiply that in to the equation. 

Cant wait for some warm weather to take this sweet ride out and watch my four year old son smash the front end up 😏

 

 

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I run a 4300kv in my re re optima with the option spur gear. I did originally use the recommended 30t pinion but to be honest it was just to much power. Pulled wheelies and was a rocket ship. I went back to either 26-27t pinion which is much better for the past 2 years. Still fast and no wheelies, it may pop the front end at times a little

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Thanks for the info! I picked up a few of those polypro hybrid pinions and I’m going to try a few out and see what works. Take it easy! 

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Most of my buggies are equipped with sensored brushless motors in the range of 8.5t to 10.5t. To keep motor temperatur low, I use ratios about 9:1. Speed and torque are high, but not exaggerated. I'm not familiar with 15.5t sensored brushless. Which ratio would you recommend? Would it work with the 51t spur and a 30t pinion?

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Looking at the tech data from brushless le mans 240s 15.5t and 19.5t, respectively, I am confused with respect to rpm...why have these two variants nearly similar rpm values?

IMG_20190226_184346.png

IMG_20190226_184244.png

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Because the kv rating is so close also despite being 15t and 19t. The le mans 240s brushless is more for nostalgia. I had a brushed one when i was a kid i used to throw in different cars i had and it was my second fasted motor at the time. 

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I installed the castle SW4 with senseless 1410 series 3800kv motor. Very affordable, ridiculously fast, so far very positive customer support too! 

I was reading up on the strange numbers that kyosho lists for their 15.5t & 19.5t motors. A lot of folks out there seem to think it could also just be a typo. It is very cool looking though... 

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If the Kyosho 240S 19.5T numbers are to be trusted, but the 15.5T ones are not, then how about this:

19.5T:  Max Power=280W  Efficiency=89%  KV=2580

If we take 280W and multiply it by the efficiency, we get 280 x 0.89 = 249.2 W actual working power.  (the rest is heat)

2580 KV divided by 249.2 W = 10.35 KV / Watt

If we can trust the 15.5T ratings for Max Power and Efficiency, but distrust the KV rating and Max RPM, then:

15.5T:  Max Power=320W  Efficiency=90%   KV=?

If we take 320W and multiply it by the efficiency, we get 320 x 0.90 = 288 W actual working power.  (the rest is heat)

If we assume that the 15.5T motor has the same KV per Watts value as the 19.5T, then:

288 W multiplied by 10.35 KV / W = 2981 KV which yields 22059 RPM at 7.4V

Is that more in line with expectations for a 15.5T brushless sensored motor?

Note:  I'm making a huge assumption that the 15.5T has the same KV/W value as the 19.5T which may not actually be true.  But considering both motors are made by the same company with similar efficiencies, it shouldn't be too far off from reality.  Unless....the numbers are actually correct, but the 15.5T has way different timing for increased torque compared to the 19.5T.  Beats me, I've never used them.

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Thanks for posting those equations! Very useful info indeed. 

I think I’d take a trust, but verify, when it comes to brushless motor stats. I don’t have an analyzer unit, but they seem like a good investment, given the amount of money one might spend on a brushless motor. 

I was talking with one of the tech support people at Castle Creations who said that they typically don’t post their power outputs, because most other companies are dishonest about their own stats. That said, the 1410 series 3800kv motor has a continuous output of 400-450 watts. Having driven the motor a bit, I tend to believe him. 

Maybe one day I’ll pick up one of those analyzers...

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