SKwiD05

DIY 2x72 motor question

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Hi everyone.  This is my first post, but I have been reading the forums for a while now.  I want to thank the community for such great information up to this point but now I am in need of help with a specific question.  I would like to build myself a 2x72 sander to keep costs low.  I found a pretty good set of plans on fabricating the chassis online so I think I'm good there.  Which brings me to the motor.  I've read here on the forums that I will want between a 1.5-3 HP motor to power the sander.  I found an unopened 3hp spa pump motor that a neighbor has for sale very cheap and was wondering if that would work.  I would assume it would but before I buy it and build a chassis around it I was hoping I could get some feedback from you guys if it will work at all, work well, ECT.  He also has an unused 1.5hp one as well if 3hp is more than a new hobby knifesmith like myself would need.

Here is the 3hp one.

https://www.spadepot.com/3-HP-Spa-Pump-2-inout-Side-Discharge-48-Frame-240V-P9406C690.aspx?zmam=55673001&zmas=1&zmac=1&zmap=BX4110-S2&gclid=CjwKCAiAnabTBRA6EiwAemvBdzkewmUfWHJPYGwSdioTXVL1_UKYyzDPX_TDWwE6NZB9bWg3_vyUVxoCb4YQAvD_BwE

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that motor looks rather open, you need a TEFC motor really as grinding dust will get inside and will damage the windings.

totally enclosed fan cooled

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That makes sense, I didn't even think about that.  Are there some examples of stuff that uses tefc motors between 1.5-3hp that I could find on Craigslist or the like that I could take the motor out of and use?  If possible, if I could find a table saw or something cheap and take the motor out of that to save me a bit on buying a new motor.

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got one for $75 used 1.5 hp at a motor repair shop

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What voltage do you have in your shop and what size breaker do you have running the shop. I ask because of the start up amp draw and overall amp draw could give you a triping breaker nightmare. I built my own 2x72 grinder and went with a Grizzly H5379 Motor 1 HP Single-Phase 1725 RPM TEFC 110V/220V

I wired it up for 110vac and it runns like a champ. 

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I use a 1.5 hp continuous duty agricultural motor from Harbor Freight wired for 110V.  As long as I use a 20a circuit I don't have any problems and it has plenty of power. It was a cheap motor but is still going strong with no problems after a few years of service.

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Agree, harbor freight or tractor supply can hook you up.  If you've only got 110, you can handle up to 1.5 HP.  Get a TEFC motor. 

 

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1 hour ago, Jason Fry said:

.  If you've only got 110, you can handle up to 1.5 HP. 

Where do you get your information?  According to my code book, a 2HP motor only draws 17 amps at 120 volts.

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Sorry I was wondering if the start up draw would blow the breaker.

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OK, I've had systems were we had to go to slow-blow breakers for start up issues.

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My 1.5 Hp motor will pop a 15A 110 circuit occasionally when you really lean on a piece grinding. I'm guessing a 2 hp would do it more. The motor's nameplate should also give a letter code for start up full amps if I remember correctly - some draw way more than you would expect .

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since the 13.2 amp draw of a 1.5 Hp is over 80% of the rating that is not surprising, and yes the 2HP on 20 will pop if you really bog it down too but its hard to bog down a 2HP knife machine.

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I was referring to a standard 15 amp circuit on #12 wire.  The numbers above match what I'd expect, about 12-13 amps for the 1.5 HP. 

That said, I've got a 2 HP 220v motor that I have never been able to stop with grinding pressure.

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Also I have wired in a quite a few 3HP motors for 120 volts, and my code book includes circuits for 10 Hp motors running on 120 volts,  so your other comment about max of 1.5Hp for 120 volts is in general a mistake.

Sorry but we try to stick with facts posted here not guesses

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What's the wire size and amp draw in you're book for a 10hp on 120v ? It has to be huge -lol. Without looking it up I picture a 100a breaker and welding leads -lol. It's smaller than that I'm sure. In my experience in the marine industry (which has to carryover to all I bet) the larger the motor - the more the tendency for higher voltage and 3 phase. Mainly from an economic building choice for the ability to use smaller wiring - thus cheaper building cost. On a side note - one of the first tugboats I worked on was 120V DC and had a 35 hp fire pump motor - and it was HUGE...... it would brown out the boat at startup - even with a 120V battery bank of 8D starting batteries that was connected to the switchboard -- lol. Modern technology has replaced that stuff....

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Me; I used to work with equipment spec'd at over 600 amps at -48 Volts DC; the power cables were bent using hydraulic setups.  Modern tech took it down to 70 amps at -48 VDC...

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19 minutes ago, tdriack said:

What's the wire size and amp draw in you're book for a 10hp on 120v ?

#4 THHN because the motor draws 76 amps

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only 1/5 Hp for a 2x72 ? you sure about that?  I strongly disagree because even a 1 Hp will get bogged down a lot, surely you must have meant 1.5 Hp?

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