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Old 11-19-2016, 05:28 PM   #1
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Default Internal gear ratio

I have a question. I see different cars have different internal drive ratio.

Xray 1:9:1
Tamiya 1:85:1
Awesomatix 2:08:1

etc etc

I run stock 13.5 blinky mode. What is the benefit of low or high internal gear in the cars ? Could someone please explain to me how this works ?
Thanks a lot guys.
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Old 11-19-2016, 06:47 PM   #2
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To me, it's just a different way to get to Final Drive Ratio, which is all that really counts. If you are running 17.5 and aiming for a 4.0 FDR and have an Associated with 2 to 1 internal (ratio of the belt pulleys, by the way), then all you need is 2 to 1 at the motor pinion to spur gear. If you have the Tamiya with the 1.85 internal ratio, then you need to run 2.16 at the motor, which is also very easy. Now, when you get to Mod and you want to run like a 7 to 1, then having the higher internal ratio makes it a little easier to achieve. You don't have to run the huge spur gears. But in all honesty, the difference between 1.85 to 2.08 (Tamiya to Awesomatix) really is in the same ball park and they all work out without too much difficulty.

Now as far as the internal gear ratio, like I said, it's the ratio of the belt pulleys. You are limited to how large of driven pulley (at the axles) you can get into the car without creating issues like center of gravity or rotating inertia. On the smaller driving pulley, you can't get too small because of the limitation of the smallest radius the belt can achieve without creating inefficiency.

Heck, there are probably issues I don't even know about, it would be great if other people chimed in, I find it all very interesting.
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Old 11-20-2016, 02:17 PM   #3
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glenna-thank you for your answer.

In our club we have quite a few different brands driving around our track. And from what we have seen is that a higher IG Awesomatix internal gear ratio gets much easier around our medium/small track then lets say the Tamiya with 1:85 using the same FDR. Its quite the gap between them. One sort of needs a completely different tactics in gearing with the two different cars. This is why i asked the question, i have seen it, but i really do not understand why and how this happening. ( cars tested with the same electronics )

any more insight is highly welcome, and i agree, its very interesting.
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Old 11-20-2016, 02:24 PM   #4
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Quote:
Originally Posted by Totarx View Post
glenna-thank you for your answer.

In our club we have quite a few different brands driving around our track. And from what we have seen is that a higher IG Awesomatix internal gear ratio gets much easier around our medium/small track then lets say the Tamiya with 1:85 using the same FDR. Its quite the gap between them. One sort of needs a completely different tactics in gearing with the two different cars. This is why i asked the question, i have seen it, but i really do not understand why and how this happening. ( cars tested with the same electronics )

any more insight is highly welcome, and i agree, its very interesting.
The Awesomatix has a very low centre of gravity which helps a lot in the corners. That may be what you're noticing rather than the internal ratio.
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Old 11-20-2016, 02:50 PM   #5
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When cars have different internal gear ratios, they will have to run different size gears to achieve the same final drive ratio. Whether this has much of a real world affect between cars has been discussed many times on this and other forums.

In practical terms, there are too many variables to compare between 2 cars whether they are the exact same vehicle or not. Often the reason a particular car is faster is due to setup and/or driver. The best thing to do is use FDR as a baseline when comparing different vehicles. You may need to make some adjustments to gearing or timing of an individual motor to get the best results.

If the original question has to do with one car out accelerating others, it could be any of the following...
Less tire slip due to grippier tires, diff settings.
Better launch due to speed control settings.
Better driver managing speed through the corners (braking/accelerating).
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Old 11-20-2016, 02:51 PM   #6
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That is a very complicated issue. Rotational mass, motor power/torque band versus time, in addition to drivetrain vibration energy loss... The best way to deal with these issues, whether 1.85 or 2.08, is to lose as much rotational mass as possible when racing stock classes....
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