pneumatic wide belt sander mechanism troubleshooting

[al ladd]

I just replaced the cast iron fork that holds the belt-interrupted air supply and the air supply nozzle itself on my Bridgewood 16" open end wide belt sander. This machine is similar to the Sunhill and Powermatic and probably several others. I used a Powermatic replacement part for the fork that's similar but not quite identical to the unavailable Bridgewood part. The air supply nozzle I jerry-rigged from an off the shelf fitting using the same very small nylon pipe for the actual air delivery. I'm now unable to get any belt oscillation, and I don't understand how it's supposed to work well enough to figure out what to try next. I've always assumed the belt blocks the air flow across the fork and either the blocking or unblocking of the flow of air (which, or both?) precipitates a rocking action in the upper drum that causes the oscillation. Should I be able to see this rock happen in the drum even without a belt in place? Might the air flow not be straight enough.....Any suggestions on how to diagnose this? Thanks!

[Jonathan Jung]

My WBS had pneumatic tracking and I paid a local industrial electrician around $600 to upgrade it to electronic eye tracking. So glad I did. Less air consumption, less noise, and easy to adjust.

[al ladd]

I should say the system was working fine until I carelessly started the machine with the belt outside the fork, which sheared the fitting that receives the air stream. This is easy to do on this machine, and I always test before starting, but was stressed, lazy and in a hurry this time. Trying to dislodge the remains of that fitting, I broke (the already fragile, apparently from years of the belt going too far), fork.

So I expected to be up and running when I replaced the broken parts. Nope!

[Bobby Robbinett]

The belt triggers the pneumatic cylinder to activate when the belt touches the little flimsy tracking eyes on each end of the machine.

[Chuck Saunders]

Make sure the air linr on the receiving line is not blocked with debris from the break. you should be able to blow air into the diaphragm to signal the top roller shift. If it doesn't get air the path is blocked.
Hope this helps
Chuck

[al ladd]

Solved my problem with the help of the discontinued Grizzly clone manual (they still make a 16 " open wide belt, but it's quite different inside). Turns out, I don't know why, I just needed more supply air. So anyone out there with an old Bridgewood, or SunHill, know that the G9983 is the same machine, with a great manual online, and a few parts still available at reasonable prices.

[Bob Andre]

Check all your air lines for leaks. Insufficient air supply to the"eye" combination will interfere with tracking. My Bridgewood is about 15 yrs old and the air lines were brittle and cracked. Got 10 meters of 6x4mm line off Amazon and all improved. I also replaced the gasket material in the tracking cylinder with material from Grainger. With the two repairs all works well. I expect I will need to replace all the air lines eventually but that's not a big deal. You can block the flow in the eye combination with your finger or whatever to mimic sandpaper to observe tracking.
Bob