Attaching a sprocket to a round shaft

[grunewald]

Something quick and easy, use a file or a grinder to make a flat spot on the shaft for your sprocket set screws to engage. Set screws on the flat shaft cannot turn. Not as strong as a keyed shaft, but maybe worth a try. This is done in the HVAC trade quite often on smaller HP air handlers, maybe not strong enough to turn a cement mixer.

 

[SPYDERLK]

Good thing you didn't run out and buy some QD taperlocks!!! I just looked at one of the spare gearboxes, and it has a keyway in the shaft. So I went and looked, and sure enough, the taperlock on the stumpgrinder has a key in it also! Duhhh, no wonder it hasn't slipped!.
You should have taken Bamatoolmaker up on that generous offer of his. A tool made the right way will outlast one done on the cheap...
David from jax

Taperlocs may slip with impact loading, but assuming they have been retightened as they seat in early in equipment life, they are way more than adequate to handle steady state torque at the max rating of the gearbox without a key. Keys come into play with inadequate tightening and/or impact. The problem with a keyed shaft is that it is much less robust in terms of fatigue resistance. Where the sprocket is not firmly held immobile on the shaft a key introduces very concentrated force at a notch in the shaft - - bad news. Any motion also causes wear,more stress. That is where Taperloc, Loctite, welding address the issues well but differently. Taperloc eliminates the gap almost completely by clamping. Loctite fills it with a high shear strength adhesive. Welding bridges the gap rigidly - very strong but complicates any change and damages an area of the shaft.

Pooh Bear
The Loctite gives you a low overhead trial with high chance of success while maintaining flexibility for future change. #638 is 4000psi shear strength - Im guessing your joint has about 2 sq inches - so 8000lb of shear would break it. I cant imagine you needing even 1/2 of this in your application. A small bottle costs about $9 and has enuff Loctite to do about 10 jobs like this.
Larry

 

[Carld]

For what you are doing two set screws 90deg a part with a dimple in the shaft where they lock down will work. Put the gear where you want it and tighten the set screws. Then remove one screw at a time and with a drill that clears the hole dimple the shaft. When both holes are dimpled move the gear over and drill the dimples a little deeper. Put the gear in place and locktite the set screws in the gear as tight as you can. It will be there for a long time. Many machines are assembled that way.

 

[3RRL]

You're right, welding it sounds better and better all the time. Who cares about replaceable bearings for your application? I'd just do it and start mixing for your project.

 

[Pooh_Bear]

If for some odd reason the inboard bearing did go bad,
I could cut the shaft off the plate, remove the bearing,
redrill the 3/4 hole in the plate to drill out the remaining shaft,
get a new bearing and a new sprocket, about $8 each,
get a new shaft, and weld it back into the plate,
and reassemble it all. These shafts I'm using I paid $2 for
about 10 years ago. They are really big anchor bolts used
for concrete slabs. One end is threaded. The other end
you can bend and place in the wet concrete as an anchor point.
They were each 3 feet long and I bought about 12 of them at the time.
I have used most of them, but if I need 3 feet of 3/4 round stock,
I could buy it for cheap at a lot of places around here.

Right now I'm gonna have a little over $100 in this project.
And that's if the electric motor I have will work for it.
If not I have been pricing motors on ebay. About $70.
A home-made concrete mixer that mixes 4 cf of concrete.
For $300 I could buy an actual mixer that mixes that much.
My home made mixer is huge and monstrous. Probably call it Frankie.
I have no idea how I'm gonna move it from where it now sets.
Probably just jack up each corner till I get it high enough to put
another pallet under it. Then use the tractor to drag it where I want it.
I only plan on using the mixer to pour moulds with. Paving blocks.
Mite make a few other moulds for other stuff. Experiment a little.

And maybe someday I'll buy a real concrete mixer.

Pooh Bear

 

[Pooh_Bear]

An update finally:

Today I took my angle grinder and a cut-off wheel
and cut a perfect keyway in the shaft. Then installed the sprocket.
I spent today putting the whole thing together.
Didn't have any concrete to mix to test it out, but I had a pile of dirt right
there next to it. So I mixed up a batch of mud. Mixes great.

Gonna have to add a cover for the motor and gearbox to keep water away.
The gearbox leaks oil around one of the shafts. Hope it don't leak too bad.

Should mix up a lot of concrete. Will try to get pictures soon.

Now I just need to make some molds for the stuff I wanna make.

Thanks.

Pooh Bear

 

[afish]

Hello, Where are the Pictures?

 

[Pooh_Bear]

The pictures were posted quite some time ago.
When this thread dropped off the first couple of pages
I removed the pictures from the server to save space.
Never expected this subject to come up again.
I might could find the pictures again or might not.
Stuff on my computer has a tendency to get archived
off to data disks and never seen again.

Pooh Bear

 

[rade0041]

As far as taking five or ten dollars into a shop and having a keyway cut, good luck. I wouldn't do it for that, and I don't make my living at it, more of a hobby. I would do it for free before I did it for that price.
Last time I paid someone to cut a keyway was in the early 80's and he wanted more than that then...
David

I just had a keyway cut in a 5/8" shaft for $15 at a local shop.