Induction motor direct drive–coupler
After I have gotton a new 2hp motor for my CM table saw, the old CM motor, 1 hp , clockwise (or reversible) rotation, becomes idle.
I am building a better table/stand for my jointer. I think that this old CM can be used in the jointer. The rotation of this old motor allows me to use direct drive. Is getting rid of the belt better?
Questions:
I have heard of a coupler for hooking up the shaft of the jointer cutter and the shaft of the motor. I think this is a soft part to compensate for any misalignment. Or is there a better way without soft part if one aligns perfectly. I can see that a metal coupler would work. Is there such a thing? Where can I get one.
Is there real advantage to direct drive. The rpm at the cutter is reduced somewhat, not much, by may be 25%. The cutter now runs at a very high 4800 rpm.
I think getting rid of the belt would give snoother run. Would this be true?
I would use the jointer motor, also 1hp, to drive a blower, which can use either rotation.
Both motors are 3450 rpm.
Replies
Does not sound practical to me. A joiner has a belt for a reason, for one, there is a lot more torque with a vbelt. Two, too much strain on the motor. For a direct drive joiner, you probably would need a very large, industrial motor, that would cost more than the whole machine. You state you will lose 25% of your cutter speed. That is WAY too much. No sense fooling with the mechanics involved. There are adjustments you can make, to get rid of vibration,etc. Try switching to one of those link belts.
http://www.mcmaster.com see page 1077 for spider couplers for one type. Direct drive is typically more efficient and more power. Belt drive usually results in a power decrease if I recall. I would put in a call the the coupler manufacturer to get the facts straight.
You would have to feed your jointer slower to get the same kind of cut you are getting now. Why do you want to change things?
Edited 2/27/2006 8:31 am ET by RickL
Edited 2/27/2006 9:10 am ET by RickL
Reducing the RPM of the cutting head will drastically decrease the quality of the surface. Jointers and planers are spec'd for cuts/min and if you use the same feed rate as usual, it'll look just like you kept the old motor and ran the wood through 25% faster. How would you mount the motor if you used it for direct drive? Why mess with a jointer that works, just so you can have a blower? If you want a blower (I assume it would be for venting fumes), get an old furnace blower- the motor is usually mounted inside and the squirrel cage design is great for something like that. Or, you could make a low speed grinder by mounting the motor low and using pulleys to reduce the RPM.
"I cut this piece four times and it's still too short."
I do agree that modern, 6" joiners, with the motor below the cutterhead, with a long belt is a vibration problem waiting to happen. You just have to take care that everything is aligned and the belt tight. That is why I recommended switching to link belts. Everyone that talks about them, raves about the difference.
I am NOT an engineer or machine tech. I have no idea of how hard it would be to add on to a newer joiner, but my father has an old 6" Walker/Turner joiner. The motor sits out, to the right of the table, in-line with the cutterhead. It uses 3 belts , that are no more than 6" in diameter, probably less. More or less, the same set-up as a cabinet saw. It is one smooth running machine. I doubt if the motor or belts have been touched, since it was built, over fifty years ago.
A vibration free machine will give the best cuts when the knives are properly adjusted. Every belt driven machine has vibration. It can be reduced with a Poly V belt or flat belt.
Direct drive machines give the best cuts due to the flywheel effect and zero belt slap. I own a 12" Oliver jointer which has a 3450 RPM motor and the head is a 5" cutting circle. It gives much better cuts than any machine I have ever owned. It is direct drive and the head and motor are balanced. It produces much less vibration than any belt driven machine I have used.
im new to wood working so my question might sound silly. why do you need 12" jointer? does it work like a planer also? thanks
W.F.3: I believe (not 100% sure) that if you set it up for direct drive and have the rotating parts all balanced togeather at a machine shop it will be the smoothest set up possible. The alinment will also be critical to a smooth running machine, this can be done with a dial gauge and some v-block gizmo to hold the gauge to the shaft. Much of the industrial woodworking equipment offers direct drive as an option on jointers, table saws and some others. Will it be worth all the effort?
Duke
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If you feel that you must change the motor, keep the configuration the same. Raising the motor will shorten the belts and possibly cut vibration if there ever was any.
Putting the motor on the side of the jointer may be possible but creates new problems. The alignment must be right or there can be stresses that will cause bearings/bushings to wear prematurely and the coupler to fail too. The center of gravity of the machine is raised which will make it more prone to falling over if you move it around the shop to store/use. The motor out the back will also increase the size of the footprint of the machine and in a small shop that can be an issue. The loss of cutter speed has been discussed already, but why would you want to spend more time at the jointer?
If the motivation is to match the shaft size to the blower then if the CM motor is of a larger diameter it can be turned down by a machinist. It would be the easiest to get a new motor for the blower especially if you factor the cost of the coupler/and all the work into converting the jointer.
If there is no power gained at the jointer then I don't see any reason to make the change. The choice is yours. Have fun.
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