Attaching a sprocket to a round shaft

[scott_vt]

After drilling the set screw holes and seeing them get ovalled out on a go cart axle

Afternoon Erik,
Im not disagreeing with you but I did feel that what I recommended would suffice remembering that he is spinning a shaft at a constant speed, which is quite slow.

Also remember that on a gocart axle your talking about higher RPM's and torque changes that would work the heck out of a setscrew arrangement at best.

The ideal arrangement would be to broach a keyway in the sprocket hub and mill the shaft to accomodate the key in the proper spot.

 

[Renze]

Afternoon Erik,
Im not disagreeing with you but I did feel that what I recommended would suffice remembering that he is spinning a shaft at a constant speed, which is quite slow.

Also remember that on a gocart axle your talking about higher RPM's and torque changes that would work the heck out of a setscrew arrangement at best.

LOL what do you think the concrete mixer is going to do ?? Usually a concrete mixer has 2 or 3 mixing paddles on the inside of the mixing drum, it will chew like a steam engine and slop out the driveline all day long.

 

[Mith]

Pooh, I've had good luck using a cutting wheel in an angle grinder, and a steady hand to cut keyways. The hardest part is widening the groove to take the key, just takes a bit of patince

 

[scott_vt]

The ideal arrangement would be to broach a keyway in the sprocket hub and mill the shaft to accomodate the key in the proper spot.

Afternoon Renze,
I think my last sentence speaks for itself

When your trying to give advice to someone that doesnt have the proper tools to do the job right, your forced to compromise on methods that may or may not be effective in the long run

 

[BTDT]

I think Northern Tool & supply sells keyed shafts for gocarts, don't know much, but you may be better off buying one of these than trying to rig something else to work. How long do you think your poly drum is going to last mixing concrete? Just curious.

 

[Renze]

Scotty if i understood you right, you said that a go-kart application was more demanding than a concrete mixer, because a concrete mixer runs at the same speed where the go-kart engine varies its rpm all the time.

I did not doubt the solution you carried in

Another solution would be to drill a hole axially, so that it would have a half circle in teh sprocket and the other half of the circle in the shaft, then tap a pin into it, as like a normal square key. Problem is that this only works when the sprocket is on the end of the shaft.

 

[BTDT]

Can you bolt the sprocket to the plate (with a spacer in between) that the drum bolts to? Then if you needed to change bearings you could just loosen setscrews on bearings, unbolt and slide off.

 

[firemanpat2910]

the problem with roll pins, taper pins, and putting a bolt threaded int the shaft is when (not if, when) the pin breaks, the sprocket spins 50 or so degrees and seizes up on the shaft. then you have to diss assemble the whole rig to deal with the center part of the pin that is still in the shaft. two or three dimples in the shaft that self center a pointed bolt or set screw into the shaft are MUCH easier to deal with. Possibly the best method is to have a split sleeve with large clamping bolts to hold onto the shaft and a easily replaceable key or shear bolt between it and the pulley. Or thread the shaft, and the pulley and use double lock nuts on each side of pulley to hold it in place. I have also seen a keyed pulley, on a stepped diameter shaft, largest diameter was a "stop" mid diameter was keyed and same size as pulley, smallest diam was threaded. you slipped the pulley onto the keyed shaft, tightened a nut against the pulley, tightened a jam nut against the nut, then tightened the set screw in the pulley. This held a varible speed motor (1 hp if memory serves) on a large printing press, that had various torque and speeds applied to it constantly.. wow sorry for the long post.

 

[SPYDERLK]

Pooh Bear, # 60 chain is too large for a 3" sprocket. It is far stronger than you need and will wear more quickly than a smaller chain due to higher kink per link. Use a 50 or the next down - ?45?

As for fixing the sprocket in place - if your hub is 1" or more longer you should be able to hold it on the 3/4 shaft with Loctite high strength retaining compound #638. I would opt for 2 flat tipped set screws about 120 degrees apart to assure 3 point shaft contact. Loctite hub to shaft - tighten setscrews [no Loctite] and then wait at least 24hrs to use. This stuff is very strong. It will hold the torque and also prevent any motion that would tend to damage the shaft. To get it off loosen the setscrews and heat to about 300F. Your drive should be able to spin it free then. Do not use a hi temperature Loctite. I find this particular product quite valuable due to its very high strength and significant weakening at hi temp.
Larry

 

[DieselPower]

My advice would be to get a keyway sprocket. Take your shaft and sprocket to a machine shop, hand them a $5 or $10 bill and have them cut you a keyway in the shaft. It will only take them 1 or 2 minutes to cut the keyway on a milling machine with a keyway cutter and it will be done correctly. I highly recomend NOT to cut the keyway yourself with a grinding/cutting wheel.