pic: 3992 Drive Train

[ksafin]

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[rcmolloy]

Out of curiosity, what is the thickness on the side plates. My guess is that it looks like 1/8.

[ksafin]

Originally Posted by rcmolloy

Out of curiosity, what is the thickness on the side plates. My guess is that it looks like 1/8.

Correct.

[dodar]

Just out of curiosity, how come you guys went with belt drive mecanum rather than the normal direct drive?

[sdcantrell56]

Looks very pretty. Seems like you chose to compromise a tremendous amount of strength for appearances though. I hope you are planning on using the bumpers as a structural member

[ksafin]

Originally Posted by sdcantrell56

Looks very pretty. Seems like you chose to compromise a tremendous amount of strength for appearances though. I hope you are planning on using the bumpers as a structural member

From some collision tests and general observation, we don't see too much of a lack of strength. It's more than strong enough all-around - the only primarily weak point is at the "X" cut out on the long side-plates, but even that is fairly strong and will be stabilized further with standoffs yet to come.

Originally Posted by dodar

Just out of curiosity, how come you guys went with belt drive mecanum rather than the normal direct drive?

When you say direct drive, do you mean direct attachment to a gearbox?
There were a few logistical reasons we didn't do that, but overall because we had the resources to make a belt drive right away.

[dodar]

Originally Posted by ksafin

When you say direct drive, do you mean direct attachment to a gearbox?
There were a few logistical reasons we didn't do that, but overall because we had the resources to make a belt drive right away.

Ya thats what I meant. So it wasnt for like CG or spacing for other things? It was just because you could?

[ksafin]

Originally Posted by dodar

Ya thats what I meant. So it wasnt for like CG or spacing for other things? It was just because you could?

CG was one of the points that came up, actually (I forgot about it as I replied to your initial inquiry).

For our climbing mechanism we need as much weight center as possible, so gearboxes at both ends were a barrier.

But otherwise it was less of "we could" than "we could do it given what we have now, or wait to order more parts to perform the same function" so we went with what we had.

[Gregor]

I'm going to quote my post in the other thread you posted with your practice robot.

Originally Posted by Gregor

From what I can tell, you are using CIMple boxes, the kit sprockets (39 and 42 tooth), and 8" mecanums.

This gears you for a very nifty 30 fps. Consider halving that, on even a third of that. That is far too fast for an FRC bot, and will be near uncontrollable for your drivers.

A quick fix would be to switch to Toughbox minis with a 12.75:1 or a 10.71:1 ratio.

Have you actually driven this yet? It is far too fast.

[Brandon_L]

Originally Posted by Gregor

I'm going to quote my post in the other thread you posted with your practice robot.



Have you actually driven this yet? It is far too fast.

I second this, are you planning on having a 30fps drive?

[ksafin]

We had the previous drivetrain (the 80/20 one) driven, and it seemed to be fine.

I'm not particularly sure what the software team did, its possible that they set a cap on the motor output speed (such as setting 75% as a max for the motor controllers).

[ksafin]

But I can say for sure that it was nowhere near 30 fps.

[Lil' Lavery]

Originally Posted by ksafin

But I can say for sure that it was nowhere near 30 fps.

The reason it's nowhere near 30fps is because you're pushing your motors way closer to stall than an average drivetrain. They aren't going to come anywhere near the free speed, yet they'll draw more current than a properly geared drivetrain and will accelerate much slower.

[Gregor]

Originally Posted by ksafin

We had the previous drivetrain (the 80/20 one) driven, and it seemed to be fine.

I'm not particularly sure what the software team did, its possible that they set a cap on the motor output speed (such as setting 75% as a max for the motor controllers).

If so, you are limiting the torque you are getting. This *shouldn't* be bad for mecanums, as I assume you won't be in pushing matches, but it really hurts your acceleration.

[akoscielski3]

Originally Posted by ksafin

We had the previous drivetrain (the 80/20 one) driven, and it seemed to be fine.

I'm not particularly sure what the software team did, its possible that they set a cap on the motor output speed (such as setting 75% as a max for the motor controllers).

The speed you have on your speed controller's will never help you with torque. You WILL NOT have enough torque to turn your wheels, and decreasing the current won't help that. You need to change your gearing. Have you tested your drive train? If not I would HIGHLY suggest it.

My team had direct driven Macanum's (6in from CIMple boxes) in 2011 and we could only drive forward/backwards and turn, we couldn't strafe because we didn't have enough torque to turn the wheel opposite to eachother. PLEASE CHECK YOUR DRIVE NOW!!! Before it's too late and you're a sitting potato on the field.