D@mnit! Delta parts

[TDHofstetter]

Oooboy. That DID GET BIT, didn't it?

The helical larger gear is either to make it run quieter (doubtful in this case) or to help drive the gear axially against a thrust bearing in a known position. There's not much angle to the teeth, though, so it MAY be that way just 'cause they could find a supply of gears cheap & they happened to be helical.

It looks a lot like the next gear in the train (the one that brass gear drives) is much narrower than the brass gear, so only a small section of the brass gear was taken out. I'd be tempted, in a case like that, to dig the two gears (plastic & brass) apart and shave enough metal off the bottom of the brass gear to bring good teeth into line with that narrow next gear again, the put a spacer (washer stack?) in the empty space at the top of the brass gear so the lathed-out section won't rise back where it was again.

If we're down to making or finding another brass gear to replace that one (making it fit alongside the plastic one), that's a 9-tooth gear (which is a rarity). I can't tell for sure, but I think that's a 14.5-degree pressure angle. Can we measure the diameter of the shaft it rides on? Fortunately, it rides freely on that axle so we don't have to deal with setscrews or any other locking device.

I'm gonna' say that brass gear runs all the way through the nylon one, serving as the nylon gear's axle. So... if we can find a 9-tooth 14.5pa gear with the same diameter, or even better a piece of bored gear stock (like toothed rod), we can press the brass gear out of the nylon one & press the new gear (or length of stock) into place.

[Joe Lyddon]

Pics are way TOO BIG...

Please resize'em down to 800 x 600... would be a lot easier to see them... ;D

Thank you...

[brburns]

I thought about trying to press the small gear out of the nylon one, but it didn't want to move too easily. I figgured I may break the nylon gear in doing so. Maybe if I heat it up some. I like your idea of moving the small gear down in the nylon one and grinding off some on the bottom. That may at least buy me some time.

Thanks for you help.

Since I got this sander, I almost find it indispencible. i hate having it down like this

[TDHofstetter]

Is the end of the small brass gear clearly visible on the opposite side of the nylon one? If it is... carefully trace around the nylon gear onto a scrap of hardwood (this is just for visual registration).

Find a nail that closely fits down the axle hole, and while you hold th gear inside its traced outline on the scrap, slide the nail down the axle hole & tap it with a mallet or hammer. That gives you a centerpunch mark.

Now remove the nail & gear and drill a hole through the scrap, centered on that centerpunch mark. The hole should be slightly larger in diameter than the brass gear. Now you have a backup platen to protect the nylon gear.

Carefully line up the nylon gear within its traced outline (if you go all "lab", you could even set three dowels around the rim for positive registration) and put the scrap & gears together into a vise with the scrap against the fixed jaw & the brass gear against the moving jaw (you can see what you're doing). Slowly tighten the vise. The vise gives you slow, controllable pressure that won't overshoot.

That pushes the brass gear into the platen hole, through the nylon gear. As soon as it "gives" the first time, stop & take everything out to verify that it's working right, then put it back to press a little more. Watch that stripped-out groove, and when you can see it's out of the way so good teeth will engage that next gear, stop.

All that remains is to remove the stub of brass you pushed out the back side. Something like a Dremel will remove the bulk of it (be CAREFUL not to damage the nylon gear's face, especially near the axle hole!), followed by careful touching up with a file for flatness.

Then... a short stack of small washers added to the top, with their ID closely matched to the axle's OD, will take up the slack where the brass gear used to be.

It won't be perfect - it'll be slightly weaker than the original - but it'll get ya down the road a long way.

I haven't heard nor seen anything from Chip yet...

EDIT: Don't heat that gear! The nylon's good for temperatures above boiling, but if you heat it enough to soften it, it's far too close to a temperature that'll destroy it... and the thermal expansion coefficients of nylon & brass are too similar to get much benefit from their difference in a case like this. Just keep it near room temperature & let the vise do its job.

[brburns]

Chip e-mailed me and said I can have the motor IF he still has it. He isn't sure. If he does this will be the best and simplest solution. Also, as luck would have it, I'm owrking only about an hour away from him next week.

Thanks for your sugestion Tim. This will be my plan B.

[brburns]

Chip has the motor. I'm going to pick it up tomorrow. YEAH!!!!!!!!!!!!!!!!!!

[TDHofstetter]

Excellent!

[brburns]

Wouldn't you know, the motors are slightly different. The gears are almost the same, but the new gears have the shaft hole 0.006" larger. I figgure it will probably work, but may not last.

[TDHofstetter]

Oh, MAN that's close!

Any way to swap armatures?

...OR...

Any way to swap axles? One's likely metric, the other SAE.

...OR...

Wrap a cigarette rolling paper around the axle THREE TIMES EXACTLY (or slightly less), and smear grease on it to keep it in place while you slide the gear on over it (about like threading spaghetti through a cat from front to back).

A cigarette paper is 0.001" thick.

[Leo Voisine]

Dec 15, 2009 10:12:07 GMT -6 brburns said:

Wouldn't you know, the motors are slightly different. The gears are almost the same, but the new gears have the shaft hole 0.006" larger. I figgure it will probably work, but may not last.

I have in the past carefully epoxyed a piece of tin foil to a shaft.

After it sets you can file and hone it so the gear fits.

Normal paper is .003 thick. Wrapped around the shaft that would be .006 - BUT paper is soft and will wear out.

Glad you found a gear set - even if a little modification is needed.

I beleive all that stuff is low RPM?? Is to balance is not really any issue.

[hescores]

I'm not one to mix business with pleasure so I rarely offer this up (and certainly not one to spam the boards), but if all else fails and you do have to look into purchasing the gear let me know. While I'm actually in the IT field, I work for a Bearing and Power Transmission distributor so I can probably get you the part that you need.

[brburns]

Thanks for the help guys. I'm running it loose right now. It's pulling 0.5 amps constantly, and that's max. I think I'll just try to get as much life out of this setup as i can. I'm thinking of taking a different route when this goes bad. I found ones with a higher gear reduction for $125 and that would be usefull. It doesn't take too much to trip the overload.