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Post by arghvark on Jan 27, 2018 11:21:18 GMT -5
So I have this old but pretty nicely refurbished Highland Park Combo unit: 8" saw with vise, 2 grinding wheels (one diamond, one SiC), and a polishing disk.
Knew the washing machine motor mounted to it was old, and for the price I paid, wasn't too upset when it gave up while doing something that probably shouldn't be done on an 8" saw. (Just for giggles went and looked up the model number- the only direct reference I quickly found was a newspaper article from 1963.)
Anyway, like a chump I bought a single phase motor cause cheap and available at my local Ace. Spins up fine at 2:3 pulley ratio (so only 1150 rpm) but won't get up to speed at 1:1. I'm sure the mass of the two grinding wheels is a hindrance here.
DON'T DO WHAT I DID!
Anyway, I'm thinking split phase should be ok as it seems double starting torque should be enough based on what I see at 2:3 and 1:1.
Oh yeah, we're talking 1/3 hp here.
Thoughts?
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Post by Rockoonz on Jan 27, 2018 19:27:33 GMT -5
Split phase is just a type of single phase motor, the only thing that would increase starting torque would be a capacitor start motor. 1/3hp seems like more than enough to spin up a small combo, are the bearings ok? 8" grinding wheels? Is the diamond wheel solid steel or plastic center? I had one of the solid steel wheels on a unit and it started up pretty slowly.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,352
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Post by quartz on Jan 27, 2018 23:00:54 GMT -5
I've got a Covington and a Star Diamond multi-wheel machines, both work fine with 1/3 hp motors. I'd be thinking some thing is wrong with the bearings. How freely does the shaft spin by hand?
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Post by arghvark on Jan 28, 2018 1:25:56 GMT -5
Thanks for setting me straight guys - feeling even more foolisher here. Don't know doodly about motors, had done a quick search, completely misunderstood what I read. Learned a bit more today. At any rate, bearings are new, shaft turns smoothly and easily. Diamond wheel is steel core. At 2:3 ratio, the unit spins right up. At 1:1, it gets to (I'm guessing here) 1/3 or even 1/4 speed within a second or two, and doesn't accelerate more. The only conclusions I can come to are dud motor or simply too much mass to spin up for that motor. Any other thoughts appreciated.
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Post by arghvark on Jan 28, 2018 1:30:52 GMT -5
But this (to me) begs the question: what starting method is used on a cheepo swamp cooler motor that is simply labelled "single phase"? Just by comparing size/shape, it appears to be split phase start?
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Post by Rockoonz on Jan 28, 2018 17:52:34 GMT -5
Just for jollies maybe give a wheel a good spin and, with your hands clear of moving parts turn it on and see if it goes to speed. If it does then your starting windings won't get your load to the speed needed for the centrifugal switch to engage. You should hear an audible click when the switch engages. Wondering if your motor maybe has issues. Split phase is also called induction and is the only type of non capacitor motor you will see over like 1/8 hp. Capacitor start and start/run motors also have 2 sets of windings like split phase, with capacitors to provide extra starting torque, and to improve the power factor with start/run motors. If anything is missing from my description feel free to correct, I've been away from industrial maintenance for years.
If possible, a pic of your unit may be helpful
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Post by johnjsgems on Jan 29, 2018 10:02:27 GMT -5
I would find a 1/2 hp capacitor start motor. Save the 1/3 hp for a trim saw, 2 station arbor, tumbler, etc. Metal wheels and drums if so equipped can be a lot of mass to turn. I would try the spin by hand too and see for sure.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Jan 29, 2018 11:57:37 GMT -5
Jeannie Genie clone is run with 1/3 HP cap start. Fires right up and can't make it bog down while shaping hard stones.
I would encourage our OP to make a short YouTube video of how it runs. I:m guessing it's running normally from what I read.
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Post by johnjsgems on Jan 30, 2018 18:47:42 GMT -5
He said it only starts on slow speed pulley.
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Post by arghvark on Feb 5, 2018 11:34:53 GMT -5
Thanks for the discussion guys; much appreciated. I'll try the hand spin, but I doubt I can get more than a few tens of rpm " "start boost" that way. I thought split phase yes, has two sets of windings, but both of which are engaged at startup and that the centrifugal switch disengages the higher resistance, "offset" start windings when the motor gets to around 3/4 of nominal? Is this incorrect? Turns out my dad has a 1/2 horse (don't know anything more about it right now) motor from an old hot tub lying around. Price is right so I'll grab that and try it when I'm up mid-March. In the meantime I'll saw small pieces only at low (~1150 rpm) with this unit and focus on getting an old 10" Franton up and running. Thanks again!
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Post by pauls on Feb 5, 2018 14:27:27 GMT -5
I have a very old but good motor that does that. The original centrifugal switch wore out and was not replaceable so the motor repair shop replaced the switch with a little timer module. Simple little thing it has the start winding in circuit for a couple of seconds at start then switches it off. Usually enough time for the motor to get up to speed. If I have a couple of really big lap disks on it the motor just doesn't have time to get up to speed before the start winding switches out. Simple solution, I have the motor on a hinge to tension the belt, just loosen the tension by hand till the motor is up to speed. Rough but it saves a good motor.
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Post by woodman on Feb 5, 2018 14:39:20 GMT -5
What was the RPM of the old motor? What RPM should the arbor turn at?
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Post by arghvark on Feb 11, 2018 17:07:54 GMT -5
What was the RPM of the old motor? What RPM should the arbor turn at? Both old and new motors are 1725 (or 1750, I forget) rpm. Recommended speed for the saw blade is 2000 rpm. Haven't yet looked for info on the grinding wheels or disk.
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Post by arghvark on Feb 11, 2018 17:09:15 GMT -5
I have a very old but good motor that does that. The original centrifugal switch wore out and was not replaceable so the motor repair shop replaced the switch with a little timer module. Simple little thing it has the start winding in circuit for a couple of seconds at start then switches it off. Usually enough time for the motor to get up to speed. If I have a couple of really big lap disks on it the motor just doesn't have time to get up to speed before the start winding switches out. Simple solution, I have the motor on a hinge to tension the belt, just loosen the tension by hand till the motor is up to speed. Rough but it saves a good motor. Not sure why I never saw this! Simple and efficient. I put my motor on a hingeD base as well. I'll try this.
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