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Post by joshuamcduffie on Feb 8, 2020 21:52:07 GMT -5
This may be a stupid question but here I go. Let’s say I’m building a home built tumbler, or running a saw, or whatever. I go on Craigslist or FB marketplace and source a used electric motor. What happens if I buy one that’s overpowered, say 1.5 hp instead of 1/3 hp? Am I just wasting money, or is there something else?
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Post by Drummond Island Rocks on Feb 9, 2020 7:27:05 GMT -5
You can find 1725 rpm motors for those applications in 1/4, 1/3, 1/2, 3/4 and 1 hp. The biggest difference will be amp draw and electricity usage. If it were a trim saw I would say using a larger HP motor then necessary would be fine because it is not powered on for long periods. For a tumbler that runs 24-7 I size the motor as small as possible while still making sure it will turn all the barrels when they are full from a stand still.
Chuck
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Post by rockjunquie on Feb 9, 2020 8:49:29 GMT -5
This may be a stupid question but here I go. Let’s say I’m building a home built tumbler, or running a saw, or whatever. I go on Craigslist or FB marketplace and source a used electric motor. What happens if I buy one that’s overpowered, say 1.5 hp instead of 1/3 hp? Am I just wasting money, or is there something else? Rule is: No stupid questions.
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Post by knave on Feb 9, 2020 12:39:04 GMT -5
joshuamcduffie I agree with Tela, if you have the question, someone else likely does also. The HP of a motor can be deceiving, as explained by Foredom here: You get the point. FLA amp rating is what I use to compare motors. If a motor has a .9 service factor (SF) it will overheat and shut off if the amp draw reaches .9 of FLA. (full load amps) Confused yet? Yeah, you and I and most people. A 120v 1 HP motor will use 12 - 15 FLA, as much as most 120v circuits can deliver. That’s why a 1.5 HP will likely be 230v. When you see a 120v shop vac advertised as 5 HP, it’s marketing. For some reason the whole machine weighs less than the 1/3 HP motor on my trim saw. Lol. Cons of oversizing the motor? Start up current is around 7x the running current so the big motors will tend to dim your lights while they start. Higher weight, harder to move or drain the equipment. The energy required to turn itself is higher for a larger motor, so extended use will cost you in the long run. TLDR? Familiarize yourself with the whole motor nameplate, don’t focus too much on HP. Most of this is from memory so please excuse me if some of it is wrong.
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Post by knave on Feb 9, 2020 12:50:02 GMT -5
That 5 HP Shop Vac? It should use 56 AMPS!! A 20A circuit is nowhere near enough to operate a “real” 5 HP motor.
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Post by Starguy on Feb 9, 2020 14:28:46 GMT -5
A capacitor start motor will start quicker under load.
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Post by joshuamcduffie on Feb 9, 2020 20:13:28 GMT -5
Good info, thanks! I keep seeing used motors around here for sale, but most of them are way too big for my electrical service, according to Evan’s chart.
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Post by knave on Feb 9, 2020 20:16:13 GMT -5
What are you looking for?
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Post by joshuamcduffie on Feb 9, 2020 22:02:55 GMT -5
I’m inspired to build my own tumbler, so just looking around.
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Post by knave on Feb 9, 2020 22:45:38 GMT -5
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Post by rmf on Feb 10, 2020 5:19:33 GMT -5
joshuamcduffie Once upon a time I built a rock tumbler and it had a 1hp motor. It was cheap and I was unsure how much power I would need to tumble 80-100 pounds at a time. I tried it once and then I got the electric bill. the big issue is if you over size the motor it still runs and burns power at that rate 24hrs /day 7 days per week after a month you will notice a bump in your power bill. In my case I resized my tumbler and added an upper deck. Needless to say I only use it when I have over 240# of material to tumble.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
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Post by jamesp on Feb 10, 2020 6:37:23 GMT -5
How big a tumbler are you building Joshua ? I use 225/700/925/1125 rpm fan(air over) motors on all my 40 pound or less rotaries Joshua. Theses motors are down in the 1/6 and 1/8 horsepower range. 110vac. Lower rpm makes for smaller main pulley. And lower rpm makes for higher torque. Surpluscenter.com often has them in stock under 'fan motors'. My 1/8hp tumbler at 700 rpm rolls 40 pounds. Recently changed out the bearings because one failed. Ran constant for at least 4 years. Rebuild about 2 months ago www.flickr.com/photos/67205364@N06/sets/72157712119685153My main tumbler has 2 sets of shafts, low and high speed. Easily rolls 100 pounds with a used 1/4 hp clothes dryer motor
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Post by knave on Feb 10, 2020 6:48:09 GMT -5
Must be from a gas dryer
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Post by joshuamcduffie on Feb 10, 2020 8:17:27 GMT -5
Thanks guys, this is all really good info. I was definitely curious about the effect of a larger motor on the electric bill, and on the effect of using a slower (or faster) motor and resizing the pulleys.
I'm still just thinking about building, not sure yet what I want to build. I like some of the builds I've seen on here with multiple sets of rollers, maybe something able to run 4 or 6 barrels at once. Once I start putting something together I'll post a new thread.
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Post by Starguy on Feb 11, 2020 15:02:51 GMT -5
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