I picked up a couple of surplus marathon 1.5hp inverter duty 1000:1 motors
awhile back like this one:
https://www.regalbeloit.com/Products/Catalog?model=145THTR5328
My plan is to replace the original single phase/single speed 1hp motor on my
PM727 mill and also add belt drive similar to what cnc4xr7 did on youtube and
bypass the original gearbox. I had thought about using a set of comet clutches
and belt as a simple solution (clutch on motor varies speed and clutch on
driven shaft varies torque) for constant speed/torque, but will probably just
make a couple of multigroove pulley sets and move the belt over as needed. I
don't think I will have room for the comet clutch setup.
Any thoughts on pulley ratios? Would be nice to be able to make this work with
one set of pulleys, but from what others have posted it looks like a second set
is necessary to be able to have ample low speed torque. I want to be able to
run small high speed cutters for CNC on aluminum etc at say 4000-6000rpm (maybe
1:1.5 pulleys?) , but also be able to have enough low speed torque for other
operations. Don't know what the biggest flycutter this size machine could
handle, and how much torque is needed so I'm kind of guessing. Maybe 1.5:1?
the specs for Marathon motor show about 22ft/lb of torque at ~100 rpm. The
lowest speed available with original gearbox and motor is 115rpm, but can't
find any torque specs on original motor to use to calculate torque for
comparison.
On Saturday, May 26, 2018 3:44 AM, Gene Heskett <ghesk...@shentel.net>
wrote:
On Saturday 26 May 2018 01:24:36 John Dammeyer wrote:
> Is something like this equivalent to a single phase 220VAC 2HP motor?
>
> https://www.ebay.ca/itm/122137567723
>
> Just thinking of how I'll add variable speed to my mill. Would it
> even need a reduction set of pulleys or is 1:1 adequate? If the
> bearings can handle it a belt ratio of 1:2 to get 6000 RPM?
>
> Thanks
> John
>
Just an observation John. but a setup intended to be run as a servo,
isn't exactly ideal for a spindle, and may overheat if asked to run
continuously. Servo's have time to cool in between moves.
I'm not in that horsepower class, but the 1 hp 3 phase I put under the
Sheldon to replace its OEM 3/4 horse single phase, with a 1.5 hp rated
vfd driving it, cost me less than $200, and will run till the major caps
in the vfd need servicing, about at 10k running hours intervals. I
stumbled over a air compressor that had 2 compressors driven by 1 hp
motors on one tank, had 40 years service time at the local horsepistol
as they were remodeling & replaceing old gear. I offered the guy $50 for
the two motors, and the torch was cutting rusty bolts 2 minutes later.
So I got the motors for 25 bucks each. Bearings in one were noisy, so I
ordered a set and put them in, going on 2 years ago now. So I've $75 in
the two motors. The vfd, some sort of a Chinese fake was about $115 on
ebay then, 80 bucks today. In 2nd gear in the belt system, it drives
that motor from 10Hz to around 150 Hz, and can do it forever at 20Hz and
up.
I don't have very much low speed current boost set, but it has run for
nearly 2 hours straight at 10Hz and I could still lay my hand on the
motor as I've set the boost at the motors nameplate FLA. That slow, the
cooling fan in the motor is not that effective At 150 Hz I get around
1700 at the spindle but its HP is in the toilet because the motor's
inductance is limiting the coil current to about an amp. Thats over 4
grand at the motor, designed for 1750. The lathes spindle s/b held below
1200 according to John Knox on the Sheldon list, its plain bronze
bearings. At 1700, they heat up.
And all without shifting the belt. With an ER40 adapter in the spindle, I
can rigid tap at 170 spindle rpms, with less than a turn of overshoot at
the bottom of the stroke. Mount a chuck and the weight of the chuck
slows the turnaround time though.
Your HP (4 ish) in a vfd can be had from ebay now at $130+ship, a Mesa
Spinx1 to interface to the vfd from lcnc is about a 20 dollar bill. That
would have me scouring the junk yards for a suitable 3 phase motor. You
might have to refresh its bearings but that's no big deal.
--
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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