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Thread: tread mill motor
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2nd May 2008, 09:53 PM #1
tread mill motor
I see another motor thread was moved but I dont know where to put this so I will put it here and see what happrns I have a Hare and Forbs Lathe with a 1.5 motor which only stopped once so far and was fixed under warenty. I also have a tread mill motor which some people seem to recomend as a good replacement because it has variable speed.
The specs are
HP 2.5
RPM 4000
Rotation CW
duty treadmill
field DM
volts 180
Could the motor be reversed to reverse the lathe?
What is Field DM?
Would this motor be suitable for this job?
Would I have to use all the electronics to run it or would a pot do the speed controle?
The treadmill has KPH, calory used , auto hills, and other features that are all electronic
Kim
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2nd May 2008, 10:16 PM #2Senior Member
- Join Date
- Jun 2005
- Location
- sydney
- Posts
- 126
Hi
Do you have any diagrams that go with this?
may be able to work it out from them
Doug
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2nd May 2008, 11:58 PM #3
Kim, these are my thoughts on this concept. With the information supplied, it is all that I have come up with.
In a treadmill application, most of the motor output is lost to friction in the transmission system and belt. The system does not/can not drive the user to higher speeds, at best it can only encourage them, and then trip them and grind them if they can't keep up. Therefore the motor does no useful work, and it is difficult to guess what it's particular torque output capability might be at any given speed.
The motor will not operate without some form of drive electronics, similar to or the same as those used for the treadmill. A simple 'pot' would not cut it here, when it's trying to handle 2000Watts of electricity. It may be possible to discard the treadmill user interface and replace that with something simple like a pot to command the motor controller, but I suspect that the controller would expect a digital signal of some sort unless the current system uses a pot to vary speed.
I am assuming that the original lathe motor is a 1440RPM one, as this gives the best torque for lathe applications.
If the motor is rated at 4000RPM to run a treadmill, there would have to be significant reduction gearing attached somewhere.
By my calculations, 4000RPM direct drive with a 100mm roller driving the belt would give a belt speed of about 75Kph. At that sort of speed, I would anticipate that slip between the belt and roller would be very considerable, in which case the normal solution would be to gear down drive to the roller and increase the roller diameter to increase contact area. I would anticipate a max belt speed of no more than 20Kph, so would suspect about 8:1 reduction and maybe a 150mm drive roller as typical.
You are dealing with differing motor technologies here, and I am not sure why, but I am guessing that you want to dable with variable speed, since you mention a pot. The 2.5HP @4000 RPM motor would be producing significantly less torque than a 1.5HP @1440 RPM one would (for a constant torque, power is proportional to RPM). To produce the same torque at 4000RPM as the 1.5HP @1440, the motor would need to be rated at about 4.2 HP.
There would be too many inponderables to guess what the performance of the motor would be like at reduced speeds, but I have a horrible notion that torque would be degraded further.
With a lathe, the normal reason for operating at lower speeds is to control the cutting speed seen by the tool tip. As the speed is reduced, more torque is required and changing the drive reduction ratios with gears or belts accomplishes this well. If you were to opt for a VS motor system, I think you would have to limit the speed range to minimum 0.7/ max 1.4 x nominal speed for the original motor, or thereabouts.
That suggests that you would need to incorperate a reduction drive of about 2:1 beyond the range built into the lathe for the original motor. My suggested variable speed range above would then provide drive speeds equivalent to the original motor operating in the range 1000 to 2000RPM, but with at best maybe 60% of the torque of the original motor.
I suspect that DM indicates that the motor field is Directly Magnetised i.e uses Permanent Magnets and is like a giant slot car/HO train motor. If this were the case, the motor could concievably be reversed by stopping, reversing polarity and restarting.
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3rd May 2008, 07:47 AM #4
Convesrion to DC motor
Hi Kim
The following are Googled cut and pasted URL’s referring to installs of DC motors in lathes. Basically from what I glean is that the reductions are in the order of about 3 to 1 back to 4.5 to 1.Theres also a bit there on the reversal of polarity picked off the field windings.
http://bbs.homeshopmachinist.net/arc...hp/t-4325.html
http://www.bedair.org/Tmotor/Tmotor1.html
http://tool20895.homestead.com/treadmill.html
[ame="http://www.youtube.com/watch?v=lgAf0uIk7iw"]YouTube - Scratch built lathe test 2[/ame]
http://www.cnczone.com/forums/archiv...p/t-11580.html
http://www.stellar-international.com/lathe.html
http://www.janellestudio.com/metal/a...d_switches.txt
Its and interesting read. I am sure there are lots of us here who harbor thoughts of a conversion.It will be interesting to see if there are any existing here in Australia.
If you succeed ,please post it here as at least I am interested in the details
Cheers
Grahame
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4th May 2008, 08:09 PM #5
Thanks for the replys guys
Kim