Geared 4 motor drivetrain

I know that this has been said before, but one of the easiest ways you could reduce probably quite a lot of friction is to connect your drive channels better. Right now, the only things that are holding your outer drive channels in place are 2 standoffs. While this is better than nothing, it’s not great because standoffs are very notorious for caving in the metal around the holes they are attached to when under high stress.
I see a gap where you have no gears around under where the standoffs are attached. you could probably put a 3 or 5-wide there, which should make it much more stable. In addition, you could also also place other standoffs in between the channels, preferably close to the ends.

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it’s impossible to say for sure from the photo, but your drive channels might not be running perfectly parallel to each other. if you can’t tell that they aren’t from close visual inspection, then they’re probably good enough. Try disconnecting your motor from the shaft it’s connected to (but leave the shaft in, just not plugged into the motor) and give the wheels a good spin with your hand. It should be able to free spin for at least a second (ideally more, but let’s start small here) after letting go of the wheel. If it can’t, then there is some significant friction from something.

The most common culprit of drive friction in my experience are that you’re overpacking the spacing on some shaft, there should be some wiggle room in your spacing so that the spacers aren’t literally clamping the sides of the wheels, preventing them from turning freely. And the second most common is from the shaft not being aligned in the holes properly, either because the holes aren’t lined up (could be from the channels not being parallel, the bearings being mounted off of their proper seating) or because the shaft itself is bent. you can test this by taking the spacing out of the shaft in question, and then just running an empty shaft through both holes and giving it a manual spin, it should be very smooth and low in friction.

this seems like the potential cause of holes being misaligned, if that is indeed the cause of your friction. You definitely want to try and hold those channels together with more than a few standoffs in the middle of the drive, otherwise the channels will put pressure on the shafts and cause massive friction.

agreed on this point as well, hs shafts will just make a drive worse rather than better, since they’re often much more difficult to reduce friction on.


5/7 gear ratio would probably be the best, in combination with high traction wheels in the front and Omni in the back

High traction as in the big boys? Or normal sized. Because if it is normal sized, we already are doing exactly what you are saying.

Ok. Thank you very much.

There are four main types of wheels(that I know of), Mecanum, Omni, Vex standard, and high traction. On a 4 motor tank drive, the best way I have found to get a good combination of speed, maneuverability, and grip is with high traction or some other form of tractions wheels in front and Omni in back, but based on driver preference All Omni might be better for your team. I do recommend switching out your current traction wheels as they don’t do as well when compared to other types of traction wheels. However it is completely up to you and your team to get the robot to fit your what you need and want out of it.


These so called “high traction” wheels actually have terrible traction. 2.75" and 4" Omni wheels both have the highest traction of any wheel, according to testing shown in this post, and traction wheels counterintuitively have the worst traction of any of the tested wheels when on the foam tiles, and near the bottom of the list on polycarbonate. While these 4" rubber wheels you’re showing did not get tested, one can infer from the obvious hardness of the rubber, and the perfectly smooth nature of the tread that they’re likely even worse than traction wheels. In fact, they likely would only be better than a wheel with no tire at all.

They also do not have superior maneuverability. All omni wheels has the best maneuverability of any tank-type drive (non-holonomic) because a good driver can make use of the drifting nature as well as the perfectly smooth turning to execute fast and precise motions. However, this might not be desirable for every driver, and both for control and defensive reasons you might not want to be able to drift. The best thing to do in that case would be to have a 6 wheel drive with omnis on the front and back, and some form of traction in the middle (locked omnis are better than actual traction wheels because they will match the other omnis in diameter perfectly, and because they have more traction). But it’s understandable that someone might not want a 6 wheel drive for a variety of reasons, so the next best thing is to have omnis in the rear and some kind of traction on the front (or whichever side you prefer the robot to turn about). This still gives decent maneuverability, but I’d choose all omnis to this purely on my driver preference. All traction is terrible because that forces the wheels to scrub against the tiles whenever you turn, which will tire out the motors and make turning unreliable and unpleasant to control.

attempting to help is appreciated, but try to do some research before making these sorts of claims, you might inadvertently mislead someone.


Thank you for the help! I have a league night tomorrow, so I will try to change the spacing a bit, and use a channel to support the outer wheel cover. I might have time to change the motor too. I will change the axle’s to normal sized on monday, so Thank you for all the help.

You’re completely right, it is very much dependent on the drivers preference, and the game. The set up I recommended is my personal preference as the Main driver for my team, but depending on what you need or want out of the robot, the maneuverability of all Omni may be better. I definitely agree that you should never go will all traction as it will cause a lot more friction and put more force on the motors. What I should have done is gone more in depth with my response and give the possibilities and the benefits of each instead of just saying my preference. I do apologize for that error on my part.

I have edited my post a bit so that it’s not as confusing. What I originally had meant to say is that from my testing I had found that, at least for my style of driving, the best way to get a combination of speed and maneuverability was with some form of traction and Omni and that we were currently using the high traction wheels. I had worded that very poorly in my original post and I am sorry if it lead someone astray.


if u want more torque, u should considering doing 6 motor base. many teams are going 6 motor base this year. there was a team that did the same gear ratio as wut u currently have and they didn’t do well because it was too slow compared to all the other robots at that comp

Ok. I will talk with my team

This gear ratio is not working for me. Would 6/7 as a ratio, or the closest vex ratio possible be ok? It is really slow.

Otherwise would 1:1 with gears add any strength?

Is it too slow or not strong enough?

Too slow. It takes too long for auto too.

Then you should really just go 1:1 with 200 on 4" wheels, or 3.25 if you really need the extra torque.

Ok. Thank you
20 char

I know I’m saying this too late, but if it helps, we use a 36:84 with 600rpm motors, and we can climb the platform with three goals.

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with 4" omnis, sorry.

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