the worm gear seems to have become unattached from the motor shaft on a helix humper motor when i used the engine to pull a heavy brass track cleaning car around the layout,now the drive shaft just spins inside the worm gear.what do they use to bond the shaft to the gear?i don’t think acc will have enough shear strength.
Check the Loc-tite web site for a special adheasive they have for shafts. I have some but I don’t remember the exact name/number. Its made for exactly this application, of course its for industrial applications, but it works fine.
I think you need to purchase a new shaft and wormgear…there is too much stress at that point for any type of glue to hold up…you may be able to use a small bit of JB weld to hold the two together but that too will crack eventually and JB weld is hard to apply thin enough to hold yet not foul the bearings …Chuck
I may just as well buy a new helix humper or allied{whatever name they are now}I think they go for $35-$40 or so.Oh well,so much for a quick fix.
I had the same thing happen to me with a helix motor. My motor is in a Bowser Mountain kit. I just pushed it back on the shaft and haven’t had a problem yet. Guess I’ll try the lock tite rout though. I can’t aford another motor on my budget.
ACC will hold it depending on how much clearance you have. If its a sliding fit use a thin ACC. .003-.005" use a thicker variety. If its over '005" then you might want to consider epoxy. The key is the prep. Make sure any old adhesive is removed and both surfaces are oil free. Torque here is measured in oz-inches, not foot pounds.
Pete
ACC will NOT work; it has no shear strength, and the bond will MAYBE hold for 1-2 revolutions.
You can buy Loctite thread locker at any auto parts store. There are different grades of strengths. You want the thread locker, not the sealer. Be sure to degreese the shaft and gear first.
You can try to knurl the shaft by placing the shaft in a vice with teeth and horse it down tight enough to leave marks and burrs on it. Then press the gear back on.
I’d say that a good 2-part epoxy is your best bet. Make sure that you allow it to cure for at least 48 hours. But like others, I’m doubtful that ANY glue will hold.
You are confusing shear strength with bond strength. Shear strength is the resistance of the adhesive to breaking apart. Bond strength is the resistance of the adhesive to separating from the either shaft or worm. You can significantly increase bond strength by removing the polished surface.
ACC compounds have a shear strength ranging from 1500 to 3000 PSI. Assuming a .080" diameter shaft and .375 worm length the contact area would be .002" square. Given an avearge 2000 PSI ACC you would need a force of 4 lbs to break the bond. Can motors sized to fit a typical HO loco generate torques of 1-2 oz/inches. (You can check the NWSL web page) If you assume the OD of the worm is .25" you can at most generate a force of 8 ounces at the circumference. Your bond would have 8 times the required strength.
Pete
Mike’
I use loctite stud and bearing mount #680 (green) to remount loose gears on shafts. Do not let any get in the shaft bearings or other moving parts or they won’t. Just a drop should do. J.R.
Mike–I had the same situation about ten years ago on a brass Balboa SP Mt-4 Mountain. I used 2-part epoxy, let it sit for 48 hours. That was ten years ago, the Mountain’s still running just fine, thank you.
Tom [:D]
