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Harry72
20th Oct 2005, 10:48 PM
Engineering types I need your opinion... ya see I got this 2hp motor that I dont have a pulley for, has 24mm output shaft.
So I go's checks out whats available and lo and behold they dont have 24mm bore pulleys only 5/8 or 1/2" so the 1/2" is 1.4mm to big... I have some tin thats .7mm would it be safe to use this as a bushing to give me a 25.4mm/1" shaft?

DavidG
20th Oct 2005, 11:14 PM
Sorry you lost me.
24mm shaft, 1/2" hole is too big??? :confused:
Did you mean 1" hole in pully?

rodm
21st Oct 2005, 12:31 AM
Harry
I'll assume you mean the 1 inch hole in the pulley is 1.4mm to big for the 24mm shaft.
You don't mention keyway so I'll assume it just has allen key grub screws to lock the pulley to the shaft. As long as the pulley is not too expensive then try it and see. I can't see you doing any damage to either the shaft or the pulley so it might be worth a try but make sure you lock the grub screw down tight. Biggest risk you run is the pulley slipping on the shaft but install the guard before running in case it spins off the shaft.
If the shaft does have a keyway it would be a different response.
A lot of the Asian motors hitting Australia now have the 24mm shaft so have you tried Carbatec or H&F, etc for a spare part pulley? Obviously it is better to have a good fit on the pulley.

Mick C.
21st Oct 2005, 01:19 AM
Tis very standard practice to bore out a smaller pully to the size you want, most engineering places that sell them do this regularly. Your idea of a shim will also work fine, i'd make sure it is a very neat fit, as in a slight tap fit on the shaft, should be great.

Harry72
21st Oct 2005, 10:02 PM
Rod, yes the shaft has a keyway. What diff will this make? I'll only be shimming it from one side of the keyway to the other and not over the key way, or will I need to slip a bit of tin under the keyway.

Mick C, they want as much as the price of the pulley to bore it out!($75...$150all up!)
Stenco pulley(14").

rodm
21st Oct 2005, 10:31 PM
Hi Harry
Yes the key will be loose and that is why I mentioned it in my earlier post. I hadn't thought about shimming the keyway and it may be worth a try.
I am a bit uneasy about shimming a 14 inch pulley though.
cheers,
Rod

Harry72
21st Oct 2005, 11:29 PM
Would it be ok if the pulley has a grub screw in the keyway slot?
Does the dia of the pulley make a differance... the longer lever factor?
Motor is only a 1420rpm(4 pole I think)so its not high rpm.

JDarvall
21st Oct 2005, 11:42 PM
I've had this problem a few times before. Love to hear from someone with a cheap solution.

I have got one idea that you'd probably roll your eyes at. A means of moulding your own bush with an inner diameter to fit an unusual sized shaft. But, I've done it and it worked. What I did was got myself some 'steal paste' .....Its a auto product. Like epoxy. You probably know more about it than me. Not putty,,,,its like aruldyt,,,,,it has to be runny, so you can pour it.

Anyway, the pully had a 1" hole and the shaft was 20mm. I greased up the inside of the pully and the shaft. I put a piece of greased up plywood, with a hole in it, over the shaft and clamped it in such a way that none of it would move, so it was perfectly square to the shaft. Bit fiddly, but finally got it. Then placed the pully over the shaft, dead centre,,,,,ie. the shaft was right in the middle of the pullys hole, so there was a 2.7mm gap all sides. Clamped the pully to the ply at this point. Checked everything with squares and calipers.

The just poured the steal paste in after giving it a heavy mix. It set in the gaps between the shaft and the pully hole completely. Cause everything was greased up you could pull it off. Been there ever since.

The stuff can be drilled as well. So, I put in a longer grub screw into the pully and drilled a matching hole in the mould so I could bind it all to the shaft

Admit, it would be preferable to buy a bush. But, if you can't, and all other options are too expensive, it might be an option.

rodm
22nd Oct 2005, 02:08 AM
A grub screw will help a lot so I wouldn't worry about shimming behind the key so long as there is sufficient key in both the shaft and pulley after tightening. If there isn't, then use a shim to move the key.
The larger the diameter the more it will wobble on the outer rim if you don't get it spot on. This introduces vibration which will transmit through whatever you are building or modifying.
Shape your shim first then slighly spring it open so it will fit in the pulley. If it doesn't hug the bore of the pulley all the way around take it out and shape it some more. You will never get it on the shaft unless it fits snug in the bore of the pulley. Worse than that would be to force it on half way and then have it jam so don't be tempted with a big hammer.
Make sure your belt and pulley guards are on before running just in case.
As a fall back if it doesn't work you can always get your machine shop to bore the pulley out to say 30mm and then bush it to your 24mm.

Harry72
22nd Oct 2005, 02:46 AM
Thanks Rod, been very helpful have a greeny!
BTW conjuring up a shed vacuum system for handheld power tools and general vac duties... super heavy duty!
Im unsure if I can get enough rpm's for impeller to create a good vacuum as most normal VC's run around 18-20000rpm.
For a impeller Im thinking one out of a heavy duty garden blower/vac which still need around 18000rpm!(anyone got an old blown up blower/vac they dont want?)
Will need to use a jackshaft... motor will have 14" pulley then on the input of the JS will be a 4", output have 14" then a 4" on the impeller, going by a online calc this should give me around 17300rpm, will everyday bearings handle this kinda speed?(will I need needle roller bearings?)

If it doesnt work out the motor will be the basis of a downdraught sanding table.

rodm
22nd Oct 2005, 03:23 AM
It is only the last set of bearings that will have to handle the highest revs and standard bearings should be able to handle it. I just did a quick search on ebay and a set of conveyor bearings can handle 17,000 rpm and I would expect that these were not designed for speed. See link below
http://cgi.ebay.com.au/20-x-6203-2rs-bearing-for-conveyers_W0QQitemZ7556116230QQcategoryZ105828QQrdZ1QQcmdZViewItem

Roller bearings are made to handle load rather than speed.
Thanks for the greenie.

savage
23rd Oct 2005, 11:41 PM
G'Day Harry,

Just a suggestion and I don't know if it will be of any help, but I have had similar problems on the odd "invention" and used hard drawn copper tube as opposed to a brass bush and it has worked fine (maybe I was just lucky). Now I got a lathe it is no longer a problem, but at the time it worked for me!..:)
savage(Eric):)