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-   -   H-Drive Strafing issues (http://www.chiefdelphi.com/forums/showthread.php?t=154921)

bowmanb 08-02-2017 12:16

Re: H-Drive Strafing issues
 
We also used a pneumatic cylinder as a "spring" on our H-drive setup in 2015. We put the cylinder on its own air circuit and tuned the pressure to the point where we got the max down-force without lifting the "normal" wheels too much. ("too much" being a technical term meaning the point where things don't work correctly :) )

messer5740 08-02-2017 13:16

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by GeeTwo (Post 1642007)
Correct. It didn't matter whether we ran on bare floor or carpeting; we never got a useful strafe with fixed mounting, even when we tried a slot and use cable tension to hold the gearbox/wheel down.

What chassis did you use?

GeeTwo 08-02-2017 13:21

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by messer5740 (Post 1642044)
What chassis did you use?

We've modified and built atop the AM14U2 for three years (2015-2017). Does it matter?

Citabria42 08-02-2017 13:24

Re: H-Drive Strafing issues
 
What we did in 2015 is have 2 pneumatic pistons on either side of axle, to push down when needed with a single trigger pull.

messer5740 08-02-2017 13:27

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by GeeTwo (Post 1642051)
We've modified and built atop the AM14U2 for three years (2015-2017). Does it matter?

I think it might.... we are using Vex, so it may be more reliable (since it is a kit)

Mulcahy 08-02-2017 18:16

Re: H-Drive Strafing issues
 
We used a copy of 148's design in 2015. https://www.youtube.com/watch?v=uL-NnuZzOkU It is the easiest way to accomplish H drive... - no springs, no pneumatics, no extra controls, and it accommodates changes in floor height seamlessly. I wish I had invented it.:)

GeeTwo 08-02-2017 22:40

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by Mulcahy (Post 1642182)
We used a copy of 148's design in 2015. https://www.youtube.com/watch?v=uL-NnuZzOkU It is the easiest way to accomplish H drive... - no springs, no pneumatics, no extra controls, and it accommodates changes in floor height seamlessly. I wish I had invented it.:)

Your link is to a match not a design. What does that design mean, and how does it make H drive easier to accomplish?

Quote:

Originally Posted by messer5740 (Post 1642054)
I think it might.... we are using Vex, so it may be more reliable (since it is a kit)

I don't get your gist. OBTW, the AM14U2/3 is also a kit. Possibly not germane, but our off-season pneumatic strafe had a number of variables really screwed up because we were using what we had vice what was best for the application, but it worked first try. Barring further findings, I cannot and will not recommend anything other than some definite control over the applied force of the strafe wheel to the carpet, whether spring or pneumatics or synthetic muscle or cosmic pressure.

pmattin5459 08-02-2017 22:47

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by messer5740 (Post 1642054)
I think it might.... we are using Vex, so it may be more reliable (since it is a kit)

It doesn't matter. First off, both are kitbots, and both are somewhat reliable chassis. I like Vex better personally, more options for entirely COTs chassis. Anyways, you simply aren't going to get the right amount of compression between the strafing wheel and the ground without actuating it. The best way to do so without mucking about in custom manufacturing is to grab a versadrop module and slap it into the place currently occupied by your strafing wheel. Position it right, and you should be able to drop the strafing wheel by actuating a single piston.

At this point, though, if you want to delay it further, then continue to deliberate. But you've only got a couple weeks left, and if you want this thing driving well by the end of build, you're going to need to either order the parts you need very quickly and get it done, or just switch to a basic 2+2 or 6-wheel tank drive.

messer5740 08-02-2017 22:48

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by GeeTwo (Post 1642302)
Your link is to a match not a design. What does that design mean?



I don't get your gist. OBTW, the AM14U2/3 is also a kit.

Wait are we talking about the same thing here???? I'm talking about this-
https://content.vexrobotics.com/vexp...-top-trans.png
And andymark has a H drive kit??

pmattin5459 09-02-2017 04:41

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by messer5740 (Post 1642307)
Wait are we talking about the same thing here???? I'm talking about this-
https://content.vexrobotics.com/vexp...-top-trans.png
And andymark has a H drive kit??

Oh I thought you guys were using VersaChassis. Vex still sells that old stuff?

Anyways, you'll probably want to use that Robowranglers method of actuating the strafing wheels. Or switch to a tank drive. Given that you have your wheels in the corners, a 2+2 (2 traction in front, 2 omni in back) would probably work alright.

cbale2000 09-02-2017 08:37

Re: H-Drive Strafing issues
 
It is possible to make a ridged mounted H-Drive work, but not work well.

In 2015 we gave H-Drive a try without realizing the need for the center wheel to be articulated, by the time we were done we had offset the center wheel 1/16"-1/8" below all the other wheels on the robot, this resulted in some very odd rocking in the chassis and the strafe only worked about 75% of the time (because the carpet floors are never perfectly flat). It wasn't accurate enough to use during autonomous, but driving it manually it worked ok.

If I had to build an H-Drive again though I would definitely put it on a suspension.

GeeTwo 09-02-2017 09:27

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by messer5740 (Post 1642307)
Wait are we talking about the same thing here???? I'm talking about this-
https://content.vexrobotics.com/vexp...-top-trans.png
And andymark has a H drive kit??

Apparently not; you asked about the chassis, not the strafe mounting.

Getting the strafe wheel at the same height as the other four is NOT what you need. Even when we had about 1/16" of a drop on ours relative to the corners, it did not provide enough traction to move the robot well. By the time we got the drop deep enough to produce consistent strafing, we had problems driving in forward and reverse. There just is no right height for a rigid mount.

Peyton Yeung 09-02-2017 09:37

Re: H-Drive Strafing issues
 
2 Attachment(s)
Quote:

Originally Posted by GeeTwo (Post 1642414)
Apparently not; you asked about the chassis, not the strafe mounting.

Getting the strafe wheel at the same height as the other four is NOT what you need. Even when we had about 1/16" of a drop on ours relative to the corners, it did not provide enough traction to move the robot well. By the time we got the drop deep enough to produce consistent strafing, we had problems driving in forward and reverse. There just is no right height for a rigid mount.

I had moderate success with a fixed mount h drive in the fall of 2014 albeit the entire chassis was made of folded 1/8" polycarbonate. The flex in the PC acted like a suspension for all the wheels.

All in all I would definitely take a look at 148's robots both their 2010 and 2014 strafe wheel assemblies.

cbale2000 09-02-2017 10:07

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by Peyton Yeung (Post 1642422)
...albeit the entire chassis was made of folded 1/8" polycarbonate...

I hate to go off topic, but in all seriousness how did this drive not self-destruct immediately? We've used solid 3/8" polycarbonate plates for our drive system for several years and it barely holds up (it tends to crack a lot). We keep using it because of the weight savings but we have to be very careful with it.

GeeTwo 09-02-2017 10:13

Re: H-Drive Strafing issues
 
Quote:

Originally Posted by Peyton Yeung (Post 1642422)
I had moderate success with a fixed mount h drive in the fall of 2014 albeit the entire chassis was made of folded 1/8" polycarbonate. The flex in the PC acted like a suspension for all the wheels.

polycarb = tough ≠rigid

Quote:

Originally Posted by cbale2000 (Post 1642434)
I hate to go off topic, but in all seriousness how did this drive not self-destruct immediately? We've used solid 3/8" polycarbonate plates for our drive system for several years and it barely holds up (it tends to crack a lot). We keep using it because of the weight savings but we have to be very careful with it.

I suspect you were using acrylic (plexiglass), not polycarbonate (lexan). See my post in the Quotes thread yesterday for a description of the difference.


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