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-   -   pic: 3992 Drive Train (http://www.chiefdelphi.com/forums/showthread.php?t=112946)

Gregor 06-02-2013 23:32
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229186)
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 06-02-2013 23:34
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229186)
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.

ksafin 06-02-2013 23:44
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by akoscielski3 (Post 1229196)
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.
What do you characterize as not being able to strafe?

Did you not have enough torque to strafe period?

When we tested this on the previous drivetrain, it succesfully strafed, albeit it a slight angle rather than directly perpendicular.

akoscielski3 06-02-2013 23:46
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229203)
What do you characterize as not being able to strafe?

Did you not have enough torque to strafe period?

When we tested this on the previous drivetrain, it succesfully strafed, albeit it a slight angle rather than directly perpendicular.
it would attempt to strafe, and would kinda move, but not really.
There was not enough reduction, usually people would use toughboxes on macanum's we were dumb and didn't
did you have 150lbs on that robot? that's when you need to the torque.

ksafin 06-02-2013 23:55
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by akoscielski3 (Post 1229206)
it would attempt to strafe, and would kinda move, but not really.
There was not enough reduction, usually people would use toughboxes on macanum's we were dumb and didn't
did you have 150lbs on that robot? that's when you need to the torque.
What about putting a Mini-CIM in each gearbox for additional torque? Or RS-775's on CIM-U-Lators?

Gregor 07-02-2013 00:01
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229215)
What about putting a Mini-CIM in each gearbox for additional torque? Or RS-775's on CIM-U-Lators?
Thats not a bad idea, and probably the fastest switch, but switching to Toughbox Mini's would give you the best results.

ksafin 07-02-2013 00:10
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by Gregor (Post 1229220)
Thats not a bad idea, and probably the fastest switch, but switching to Toughbox Mini's would give you the best results.
We'll see what we can do.

We'll test with this and a heavy load on the chassis and see if the results are poor enough to warrant the switch.

If anything, I think we'll switch to toughbox Nanos. The mini has a front plate bigger than our actual plate so it'd be an odd fit.

Gregor 07-02-2013 00:12
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229229)
We'll see what we can do.

We'll test with this and a heavy load on the chassis and see if the results are poor enough to warrant the switch.

If anything, I think we'll switch to toughbox Nanos. The mini has a front plate bigger than our actual plate so it'd be an odd fit.
TB Nanos are also a good choice, I like them.

Lil' Lavery 07-02-2013 09:37
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by ksafin (Post 1229191)
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.

Bstep 07-02-2013 13:19
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by Gregor (Post 1229159)
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 doubt that they will realistically achieve this kind of speed with the losses in the gearbox, lack of friction with the carpet, and other losses. If they do in fact reach speeds comparable to 30 fps then more power to them. This years game has no mid-field obstacle and score will be determined heavily by how fast disks can be ferried from the feeder station to shooting position. A fast drive base could be a game changer.

Gregor 07-02-2013 21:30
Re: pic: 3992 Drive Train
 
Quote:
Originally Posted by Bstep (Post 1229397)
I doubt that they will realistically achieve this kind of speed with the losses in the gearbox, lack of friction with the carpet, and other losses. If they do in fact reach speeds comparable to 30 fps then more power to them. This years game has no mid-field obstacle and score will be determined heavily by how fast disks can be ferried from the feeder station to shooting position. A fast drive base could be a game changer.
This is true, all the more reason to use a greater reduction. Lets say they never surpass 18 ft/s when geared for 30 ft/s (random guess). If they gear for 18 ft/s, you get the same top speed with greater acceleration and torque.


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