Modifying Vexpro Ball Shifter transmissions

[Lil' Lavery]

I don't think 1676 would argue that it's not possible to avoid leaks. I don't think they're planning on allowing the leaks to continue with this robot and most likely will do everything in their power to avoid them in the future.

However, in the event a leak does occur, I think they want a fail safe so they don't also lose their ability to drive when they lose pressure.

[DonRotolo]

Precisely Sean.

Originally Posted by Sarakiro

beyond that, has anyone come up with a way to modify the transmission without compromising the structural integrity of the transmission case?

Modify them to do what? That might help us help you.

Originally Posted by T^2

(Personally, I see the default neutral as a feature, not a bug, and I wonder if 1678 might be able to take advantage of it in the future...)

Between my team and yours, we'd have to ask FRC 1677...

We lost air because of a failure. That failure mode has since been eliminated, but no doubt there are others.

I was thinking that a plain rubber band would do the trick.

[T^2]

Originally Posted by DonRotolo

I was thinking that a plain rubber band would do the trick.

I would advise against it. Our team missed a potential division win in 2011 because of rubber bands. Springs are your friends.

[MrBasse]

Originally Posted by T^2

I would advise against it. Our team missed a potential division win in 2011 because of rubber bands. Springs are your friends.

I would assume (I don't know the situation you were in) that rubber bands had nothing to do with missing out on a win, rather how you used them caused your problems. Rubber bands are great tools when used wisely. They are cheap, plentiful, and easy to work with. At your next competition try walking around the pits to find a direct replacement for that critical spring that you used, then try finding a rubber band... Springs are not quite as friendly going around objects, you can't tie a spring to something without using another material or drilling a hole, and if a spring breaks or deforms you have to have a replacement that is the same size and strength. We never plan to use them, but rubber bands have been necessary additions to our robots all three years and have performed near flawlessly when taken care of.

[Kernaghan]

I wonder if there is a way of modifying the ball shifter to avoid pneumatic shifting all together, even something like using window motors(servo might not be powerful enough to shift on the fly).

[DonRotolo]

Originally Posted by Kernaghan

I wonder if there is a way of modifying the ball shifter to avoid pneumatic shifting all together, even something like using window motors(servo might not be powerful enough to shift on the fly).

Absolutely there is, but for most, pneumatics are far more reliable, simpler, and lighter. These can easily be shifted with a servo, it that servo used, say, a Chap-Stick "extender" mechanism to do the actual pushing.

[cmrnpizzo14]

Originally Posted by Kernaghan

I wonder if there is a way of modifying the ball shifter to avoid pneumatic shifting all together, even something like using window motors(servo might not be powerful enough to shift on the fly).

Can't ball shifters be purchased with a servo instead of pneumatics anyways?

EDIT: 254th post goes out to the cheesy poofs. I love those guys.

[T^2]

Originally Posted by cmrnpizzo14

Can't ball shifters be purchased with a servo instead of pneumatics anyways?

No.

[Billfred]

Originally Posted by cmrnpizzo14

Can't ball shifters be purchased with a servo instead of pneumatics anyways?

You're thinking of AndyMark's shifters (though given past rules on servos, every year we've used AM shifters we've used pneumatics).

The VexPro line is pneumatics-only.

[cmrnpizzo14]

Originally Posted by Billfred

You're thinking of AndyMark's shifters (though given past rules on servos, every year we've used AM shifters we've used pneumatics).

The VexPro line is pneumatics-only.

Yes thank you. I knew there were servo operated shifters somewhere!

[Sarakiro]

Absolutely, leaks in general can be fixed. The only issue is that the solution to the problem is active, such that it can be applied in the event of a leak. As everyone knows, pneumatic systems pop; It is inevitable. I have thought about the spring/elastic solution but the one drawback is that regardless of what is modified, it is subject to the conditions within the gearbox. I am thinking that the fix (if internal, which I currently favor) should be subjected to a long term test. Perhaps a pre-Prototype phase.

I did see that the transmissions came with a servo option (has anyone used it?) - I just find that I am not quite in love with servo functionality in general. And is anyone considering other transmission options?

Pardon the "loose" earlier.

I would like to hear a bit more about neutral being a feature. I can only imagine it being used in one paradigm.

[magnets]

Originally Posted by Sarakiro

I did see that the transmissions came with a servo option (has anyone used it?) - I just find that I am not quite in love with servo functionality in general. And is anyone considering other transmission options?

Where did you see this? I can't find it on the vex pro page.

I'm not sure, but I think that team 67 might have used a motor to shift a ball shifter this year, but just ended up using a zip tie to lock it in high gear because it didn't work well, so you might want to ask them about that.

[EricH]

I don't know for sure if this will be an option next year, but did anybody try using an electric solenoid this last year, particularly for shifting? They were legal.

Thinking that might be a smidge easier than modding the transmission for a spring.

[ErvinI]

This thread will answer a few questions:

http://www.chiefdelphi.com/forums/sh...t=window+motor

Specifically, regarding 67's shifting this year:

Originally Posted by Adam Freeman

We were unable to package our typical window motor shifter with the smaller chassis size. We then designed a VEX-393 motor shiter setup that ended up stalling out and frying a digital side car (or two...). After that, we tried to design a typical servo shifting system. We ran out of time before the season started to install the servo shifter, but after looking at it more closely I don't think it would have worked very well. We were trying to emulate the AM-Super-shifter servo setup, but had a hard time getting the rotation of the shift arm transferred into axial movement of the shaft that shifts the gear box. There seemed to be a lot of play in that shaft. Probably just needed some additional constraints that we didn't have time to design in.

I also looked into trying to find a suitable electric solenoid to shift with, but was unable to find one that seemed like it met all the rules and had enough power to shift.

In the end, we just zip tied the ball shifters in high gear and attempted to avoid pushing matches.

Maybe the guys at VEXpro can design one for us teams that can't seem to make room for a pneumatic system.

Regarding electronic solenoids (Adam touched upon it in the above quote, also):

Originally Posted by AllenGregoryIV

We also looked at the possibility of electronic solenoids to shift or be brakes and couldn't find any that had enough power or worked in a way that we though would be reliable or adaptable for that application.

In conclusion, window motor shifters are very large, VEX motor shifters fry up a lot, VEXpro doesn't make servo shifters (and 67 had issues making a replacement), and electronic solenoids aren't strong enough.

[Sarakiro]

Originally Posted by magnets

Where did you see this? I can't find it on the vex pro page.

I'm not sure, but I think that team 67 might have used a motor to shift a ball shifter this year, but just ended up using a zip tie to lock it in high gear because it didn't work well, so you might want to ask them about that.

I might not have been there, but I did see them somewhere. Regardless, I would stick to pneumatic shifters, personally.

Thanks. We will likely try modifying the transmission to see if there exists a desirable outcome.