Used 638 for a year with no issues, was absolutely sold on it too. Cleaned well, applied correctly and cured for 50 odd hours.
Then one day I had a flap and depressed my throttle as I put the board down, that jolt from the wheel touching the ground at speed popped one of the pulleys loose. It made an audible crack as it snapped loose. I cleaned it up, re did it and let it cure.
Then about 2 weeks later I was riding not very fast down a road, leaned in to a corner and heard one of my motors scream. Sure enough the other pulley had come loose, presumably weakened in the same incident but holding on. Long walk home.
Ultimately they failed and so I won’t do it again or suggest it to anyone. Key costs nothing, mechanical failure from that system is much less likely, just makes sense to me.
I have blue loctite around the shaft as well as my grib screws in motor sprockets. I hope this would let me remove them eventually but I tried shifting the position of one slightly after removing the set screw and it wouldn’t budge.
So IMO it will probably hold on it’s own but I don’t trust it to.
I’ve not had good luck with grub screws holding despite whatever loctite. So actually for me the retaining compound gives me more peace of mind vs grub screw. Maybe a socket head screw for pulleys with the extended part might work better.
You need a screw or retaining compound to use a key. So I’m thinking key + retaining compound might be the best combo.
For me the problem isn’t the key. I have keys, but the problem is that I had to replace the shaft with a longer, hardened steel one. So the problem is the missing keyway for the key. Machining it correctly without professional equipment is almost impossible. And having improper, not 100% precise keyways is worse than using loctite IMO, because you will get rattling etc.
Agreed, does your pinion gear have a grub screw? I would maybe try to file a small flat spot in your motor shaft so that the grub screw could have a nice flat and slightly depressed landing spot to securely hold onto your motor shaft. Then a dab of blue or maybe even red loctite…and you should not have a problem.
Yes it does. Would be worth a try if it comes loose someday. Until now it holds strong.
But I did already try to file a flat spot, for the motor can. Didn’t work out well, the shaft barely got scratched (I did use a metal file) that’s why I used loctite there as well.
I allways use loctite 648, plus retaining grub screws, and key way if it´s possible…I can live without the screw or the key, but not without the retaining compound…
Loctite 648 has always been good to me as long as the tolerances are small and the parts properly degreased.
That said the combinations below are the only I am comfortable with:
On the topic of retaining fluid, what would be a good choice for gluing in a loose fitting kingpin to the baseplate? Specifically, I’m thinking about the TB 218 baseplates where the kingpin will just fall out and wiggles a bit in the hole. Seems to be about a sheet of paper thick gap around the kingpin.
that’s why I used loctite there as well.