My team made this drivetrain for our robot. However, we are still relatively new to gear ratios, and are not sure what the gear ratio is. Can anyone help us identify if? The two 84T gears are being powered.
iirc those small ones are 36T. In that case, your gear ratio is 84:36.
Quick math lesson: all ratios are essentially just fractions, so 84:36 = 84/36 = 42/18 = 21/9 = 7/3 so your simplified gear ratio is 7:3 
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A small gear powering a large one is generally ok. But a large powered a small tends to have VERY high frictional losses. You would be better using (5) 60 tooth gears. You might not even have to change the bearing/axle spacing.
Large gears like that are also going to negatively impact getting over the bar and the gears could scratch up and damage the middle bar if you try to go over.
I would suggest looking for different gear trains that achieve the same of similar wheel rpm with smaller gears and also looking at using a faster gear cartridge as they have much lover friction losses than gears.
The motors start at a high rpm and the slower the gearbox the more they are geared down for torque. This means then gearing them back up for higher speed is inefficient.
Also, the vex gearboxes are metal gears with tighter tolerances, better mounting, lower moments of inertia, and lubricant.
Hope this helps.
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Bro. That gear ratio = 2.3333
If you do 2.3333x 200, that is 466 rpm
I am going to hope that you use 100 Rpm motors (Red cartridges.)
Our drivetrain is similar to yours, instead we use a 60 tooth gear on the omni wheels. It does scratch the barrier a bit (notnas much as our barrier sleds), and it makes getting over longer and more difficult. I do recommend that you change the ratio or at least elevate the 84 tooth gears a bit (the only reason why we used it is because we don’t have enough blue cartridges).
But to answer your question, gear ratios are (driven gear : mechanism gear). So yours would be 84:36 or 7:3. To find the speed, do (motor rpm / 60)*gear ratio.
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Or you could do 84/36*motor rpm
Try not to use motor rpm (rotations per minute). Usually we don’t measure in inches/minute (VEX matches are only 2 minutes long), and the measurements resulting from it would be crazy long. In/sec is much more convenient and provides a more convenient estimation for the drivers.
That’s why I say to divide motor rpm by 60 (to get rotations per second).
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Bro you literally said motor RPM
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Since you use rpm, you’re doing in/min
By dividing rpm by 60, it yields rps (1 minute = 60 seconds).
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Yeah, I think he meant not to use minutes when talking about distance, however, I think it is viable to use rpm and not rps when talking about rotation.
Also (not related to gear ratios) are you planning to add bracing to your drive base?
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