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Shifter Fix

Qbranch

By: Qbranch
New: 02-05-2008 10:17 PM
Updated: 02-05-2008 10:17 PM
Views: 2598 times


Shifter Fix

Our Supershifters had too much runout in the encoder shafts, so we had to make a replacement. Now, we have a ball bearing fully enclosed encoder with a Helical coupling between the transmisson and the encoder. Should be great.

Also, we found servo shifting to be slow (and occasionally non existent in some cases) so we heeded Andy's warning and switched to pneumatic shifting.

-q

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02-06-2008 07:06 AM

Tytus Gerrish


Unread Re: pic: Shifter Fix

the sound Pnumatic shifting makes happy



02-06-2008 11:22 AM

Tom Line


Unread Re: pic: Shifter Fix

I'll second the servo issue.

Simply: servo shifting super shifters stinks.

I couldn't resist all those S's. The servos cannot shift under any type of load. The sometimes can't pull it out of gear when your robot isn't moving, and often will not go into gear at all.

We just installed a pneumatic system on the bot last night so we can shift.



02-06-2008 01:11 PM

Guy Davidson


Unread Re: pic: Shifter Fix

Q,

would you be willing to list the part numbers you used to couple and mount the encoder? We've also been having some reliability problems with the encoders and are looking into alternatives now.

Thanks.



02-06-2008 02:10 PM

Qbranch


Unread Re: pic: Shifter Fix

Quote:
Originally Posted by sumadin View Post
would you be willing to list the part numbers you used to couple and mount the encoder? We've also been having some reliability problems with the encoders and are looking into alternatives now.
Unfortunately, the bracket that actually mounts the encoder we burned out on our PlasmaCAM table (yes, it's true, something from the back of a popular science magazing that works most the time). The bolts, nuts, washers I assume are self explanatory beyond their being #10-32. Honestly I don't know exactly how long the bolts are, I dug for them in the "Box of No Return" in the shop, same with the nuts and washers.

The encoder carries the same electrical specifications as the one that andy mark put on from the factory, minus being open frame and suceptible to any shocks/misalignments/runouts in the main drive shaft of the transmission.

The part number of this US Digital encoder is S4-250-B. That is, an S4 fully assembled encoder, 250 counts/rev, Ball bearing shaft.

The specific coupler is from McMaster (since we needed it quick) but could be obtained for less money from Helical (about $6 from them, $22 from mcmaster) is a 9861T609 coupling. This is a flexure coupling that goes from a 3/8" to 3/8" bore, 1" in length. If you want even more isolation from vibration/runout/whatever in the transmission, get a larger coupler with the same bores. The longer the coupler, the more isolated, however, the more weight/size.

Let me know (in this thread) if you have any problems or further questions.

-q



02-06-2008 03:32 PM

lukevanoort


Unread Re: pic: Shifter Fix

Quote:
Originally Posted by Tom Line View Post
I'll second the servo issue.

Simply: servo shifting super shifters stinks.

I couldn't resist all those S's. The servos cannot shift under any type of load. The sometimes can't pull it out of gear when your robot isn't moving, and often will not go into gear at all.

We just installed a pneumatic system on the bot last night so we can shift.
We aren't running Super Shifters, but we are using AM Gen2 Servo Shifters, which have a very similar shifting action. We had the symptoms you describe when we tried to shift before we added some oil (I think we actually used thread cutting oil) to the dog and the shaft it slides on. After that and a little tweaking of the points the servo shifts to, the transmissions shift reliably and pretty quickly. Under heavy load, they take about one second to shift, but they do shift reliably (the only times we've missed shifts were when the servo was going to the wrong point); under light loads, the time drops well under a second. We haven't had a chance to try it out yet, but we have added some code to cut motor power for about a tenth of a second (we'll probably change that to a quarter or half a second of reduced power instead of a tenth of none), which should make shifting a bit faster.



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