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  #31   Spotlight this post!  
Unread 09-02-2017, 10:22
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Re: H-Drive Strafing issues

Quote:
Originally Posted by Peyton Yeung View Post
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.
So you didnt need to add suspension into the frame? We found ut if you drive forward slowly it strafes well.
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Unread 09-02-2017, 11:53
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Re: H-Drive Strafing issues

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Originally Posted by cbale2000 View Post
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.
It never ran against other robots but it drove well. Each wheel was a single reduction off of a CIM which kept the gear meshes simple. It was incredibly flexible (both a blessing and a curse) which made for constant contact with the carpet. Never had cracking with the 1/8" PC even with the cold bending for the flanges.
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Unread 09-02-2017, 11:55
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Re: H-Drive Strafing issues

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Originally Posted by messer5740 View Post
So you didnt need to add suspension into the frame? We found ut if you drive forward slowly it strafes well.
No but the entire frame acted as a suspension since the polycarbonate is flexble. Probably not ideal for a full contact games such as Steamworks.
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Unread 09-02-2017, 13:44
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Re: H-Drive Strafing issues

Quote:
Originally Posted by Peyton Yeung View Post
No but the entire frame acted as a suspension since the polycarbonate is flexble. Probably not ideal for a full contact games such as Steamworks.
So think we will be good once we put it on the carpet?
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Unread 09-02-2017, 14:14
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Re: H-Drive Strafing issues

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Originally Posted by GeeTwo View Post
I suspect you were using acrylic (plexiglass), not polycarbonate (lexan). See my post in the Quotes thread yesterday for a description of the difference.
I don't think so, unless the supplier screwed up and gave us the wrong stuff. We did waterjet it if that makes any difference.

Quote:
Originally Posted by Peyton Yeung View Post
It never ran against other robots but it drove well. Each wheel was a single reduction off of a CIM which kept the gear meshes simple. It was incredibly flexible (both a blessing and a curse) which made for constant contact with the carpet. Never had cracking with the 1/8" PC even with the cold bending for the flanges.
I'm a bit surprised you were able to keep the gears lined up with the amount of flex I would expect it to have plus the weight of the CIM motors hanging off. Makes sense that it didn't drive in a competition though, I'm not sure even bumpers would save that frame from a game like this year or last.


Quote:
Originally Posted by messer5740 View Post
So think we will be good once we put it on the carpet?
The carpet will definitely help but I STRONGLY recommend not waiting till you get to your first competition to find out. Try to find someone nearby with a practice field or pick up a small section of carpet comparable to what's used on the field from a local carpet store. There are few things worse then going to a competition and finding out your drive system doesn't run like you expect it to.
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Last edited by cbale2000 : 09-02-2017 at 14:18.
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Unread 09-02-2017, 15:40
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Re: H-Drive Strafing issues

A picture of the robot in question would help us out a lot. I have built the exact same H-drive from the Vex Drive in a Day kit. It could barely even drive on linoleum or another hard surface. Driving on carpet was much more successful, but there's a large chance you'll still run into consistency issues. Now, you have a couple options open to you.
  1. Leave it as is. When you get to competition, you might be able to strafe; you might not.
  2. Take out the strafing module entirely. Then you'll just have a four wheel omni.
  3. Take out the strafing module and switch out your back two wheels for traction wheels.
  4. Lower the mounting point for the strafing module. You can do this in a variety of ways, from complex as welding the module to the current drive rails to as simple as getting clever with washer placement. This will mean there is more of the robot's weight on the strafing wheel, allowing you to actually strafe. However, this takes normal force off of your four main drive wheels. This means you'll have less traction when driving forwards, and your chassis may not sit flat on the ground.
  5. You can design and use some sort of actuating module like the VersaDrop or something completely custom to lower the strafing wheel when you need to strafe and raise it when you drive normally.
  6. You can design something like 148's actuating modules that use the the friction of the gearbox to provide downforce on the strafing wheel.

Those options are listed in rough order of difficulty. You and your team will have to decide which option is best for you.
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Unread 09-02-2017, 21:14
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Re: H-Drive Strafing issues

My team ran an H-drive in 2015, and had this issue for a while. Our solution was to use a spring to pull the module down while simultaneously acting as a suspension allowing for the robot to not get completely shaken off-balance upon hitting bumps.
I agree that a picture or model of the drivetrain would be extremely helpful for us to see where a solution could be implemented.
Simply put, if I can't see it, I can't solve it.
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Unread 10-02-2017, 00:29
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Re: H-Drive Strafing issues

Our team is also going with a H drive this year. We have found that it isn't difficult to put a sideways module on a pair of articulated arms. The plates we're using are cnc'd but you can cut them out of an old AM14U if you need to. They just have to have the Toughbox's hole pattern. Here's a picture: https://scontent-syd2-1.xx.fbcdn.net...f5&oe=589F53C9
Hope this helps.
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