AndyMark shifter Dog Gear screw problem - lower your pressures

[balloons]

Originally Posted by James Tonthat

We found that running about 14 competition level matches breaks the screws. It happened to our practice bot at home, and then again at Lone Star. Our solution so far is to replace the screws (M2.5 x 20, McM# 91290A108) every three competition rounds and running at 45 psi.

Edit: The only thing is the shifters shift a lot more sluggishly at 45 psi.

Are those ones from McMaster sheering too? Those are class 12.9 bolts...Or have you not actually experienced any problems with them and are changing them out for "just in case?"

[artdutra04]

The shifting cylinders on both our practice and competition robots are fed off of a secondary regulator that's set around 10 PSI (as low as the pressure gauge displays). Neither robot has had any problems shifting.

[Raul]

To allow the shifter to work more smoothly and reliably at lower pressures (and just in general):

What I have always found with the AM shifters is that you need to leave the cylinder somewhat loose/floating in the mounting. In other words, do not completely tighten the nut holding the cylinder to the mounting plate. What this does is allow the cylinder to easily adjust to any slight misaligment of the dog shifting shaft and the cylinder and mounting holes.

Use threadlocking lock-tite to hold the nut in place. Tighten the nut all the way and then back off about a 1/4 turn to allow everything to float and align itself how it wants.

To fix the screw breakage problem more reliably (especially if you do not want to reduce the pressure):

Do not just replace the M2.5 screw with another screw. The threads on the screws inherently act as a stress concentrator. Instead, drill out the one side that is threaded with a 3/32 drill (use Anchor Lube to make this easy) and press in a roll pin.

Hope this helps.

[martin417]

We have had no problems with ours, and since we have implemented automatic shifting, we shift a LOT. We are shifting at 60 PSI. We ran many many practices, and ran 16 matches at Peachtree. I want to be sure we don't have troubles at St. Louis. I am not sure if ours is the older version or the newer version (we bought them from another team that had used them in an off season project). Where is the pin/screw in question? Can they be checked / replaced without dis-assembling the transmissions?

[Brant Bowen]

Originally Posted by martin417

Where is the pin/screw in question? Can they be checked / replaced without dis-assembling the transmissions?

Andy is on the road headed towards the Smokey Mountain Regional right now so hopefully I can answer a couple of the questions. The screw that we are talking about is in the dog gear which is between the two gears on the output shaft. This is a picture of the AM Shifter, so ignore sprockets on right. This shows the dog gear with the pin in it (the old way we used to secure the dog gear to the shifter shaft.) Take the black housing off your Super Shifter and you should be able to easily find the dog gear on the output shaft. It sounds like the one you have is older and should probably have the pin, not the screw, but you might want to check it to be safe.

Yes, the screw is a M2.5 x 20 socket head cap screw.

[martin417]

Originally Posted by Brant Bowen

Andy is on the road headed towards the Smokey Mountain Regional right now so hopefully I can answer a couple of the questions. The screw that we are talking about is in the dog gear which is between the two gears on the output shaft. This is a picture of the AM Shifter, so ignore sprockets on right. This shows the dog gear with the pin in it (the old way we used to secure the dog gear to the shifter shaft.) Take the black housing off your Super Shifter and you should be able to easily find the dog gear on the output shaft. It sounds like the one you have is older and should probably have the pin, not the screw, but you might want to check it to be safe.

Yes, the screw is a M2.5 x 20 socket head cap screw.

Thanks! We'll check it when we un-crate the robot in St. Louis.

[Brant Bowen]

If anyone who wants to replace their screw with roll pins needs some roll pins, let us know. We can either snail mail you a couple or bring them to Championships.

[Alan Ing]

Back in 2008 we used the AM SuperShifter with great success and highly recommend the product. We did learn the hard way that 60 psi and autoshifting will make short work of the roll pins as we blew one in Portland and the other just before the final match in Hawaii against 233 and 254 (not that it would have made a difference, we were outgunned ) . As mentioned by others, the best solution is to run a secondary regulator and reduce the pressure.

Having said that, If you are presently at a regional and you have the older style gearbox with a broken roll pin and you don't have access to a new one, do what we did, buy a 3/32" drill bit cut it short to the length of a roll pin and drive it into the gearbox. The drill bit was a perfect light press fit in our situation, but you may have to dab a bit of epoxy to keep yours from coming loose. Those drill bits made it through Championships and IRI and are still working just fine with the transmission auto shifting at 60 psi.

[Chris]

Fixed, yesterday at the Hartford Regional.

Thanks AndyMark for the heads up.