Paul TIKI Posted January 1, 2021 Share Posted January 1, 2021 I have the motor out of a scrapped treadmill. it's a 2.5 hp 3500 RPM, I think single phase motor that should run a treat on 120v normal house electricity. I have a 120 v speed controller somewhere around here that can be used to control the speed f the thing. I'm debating wheter to use it as a bench or a belt grinder. First off, I know debris can get in and destroy the motor pretty quick so I plan on housing it in a sheet metal shell and using vacuum cleaner filters to block the worst of the particulates while still allowing airflow. The motor itself has a balanced flywheel on one side and a belt pulley for the treadmill on the other. What I was thinking the easiest thing would be to just mount an 8 inch grinding wheel on the side opposite the flywheel and call it good. That can get me operational at the lowest cost while I take the time to figure out how to do a no-weld setup for a belt grinder powered by the same motor. Am I gambling badly with my fingers with that kind of contraption? Should I just get a home depot kind of bench grinder or 1x42 belt sander and wait until I can gather the parts for a 2x72 grinder? Quote Link to comment Share on other sites More sharing options...
George N. M. Posted January 1, 2021 Share Posted January 1, 2021 Paul: That is a pretty large motor for a grinder but is available and the price is right. Most bench grinders I have seen are 1 hp or less. The biggest safety feature which you should not ignore is a guard around the wheel and a work rest in front. A wheel spinning by itself can be pretty dangerous with the possibilities of it flinging things at high velocity or sucking things into it. The latter is the main risk of a larger motor, it takes a lot more to bog it down and stop it if it grabs something (like you). I think that you are OK using it but be careful and think of worst case scenarios. "By hammer and hand all arts do stand." Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 1, 2021 Author Share Posted January 1, 2021 That makes sense. I hadn't thought about building a guard to protect me, just one to protect the motor from debris and metal shaving. So if I were to do this I would need to build a motor housing plus a strong enough guard for the wheel plus a work shelf. That's starting to push me more into "Just buy one from home depot" territory. I really want to make something cool from that monster motor because I love to up cycle and recycle stuff in interesting ways. I may just get it wired up to power something and just shelve it until I can plan out a 2x72 belt grinder build that won't break the bank. Any other things I could use it for? Maybe a small electrically driven power hammer (I think they are called tyre type hammers) or a garden gnome flinging device? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 2, 2021 Share Posted January 2, 2021 Paul asking a "Should I" question without all the details is something you shouldn't. Do you need a belt grinder? What kind of stuff do you plan to be grinding? Can you work towards buying one of the less expensive belt grinders, doubly less expensive if you can get it without the motor? Would trading it for something you need right now be an option? A speed control motor is handy for a belt grinder, less handy for a bench grinder. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 2, 2021 Author Share Posted January 2, 2021 A grinder, be it a belt or a bench type is something I foresee a future need for. I will be needing it to sharpen lawn mower blades this coming spring and it will be handy for other things. I suppose an angle grinder can serve in the meantime. I want to eventually begin bladesmithing, but I got a lot to learn before i need something like a bigger belt grinder. I posed the question because I can do certain kinds of builds inside when the weather is nasty and lighting the forge is not an option. I just don't want to waste time and effort on something silly or, worse, dangerous. You're right of course that a "should i" question without full info usually means you should not. I'm just looking for the things I might be missing. For example, George pointed out the guard for the wheel itself, something I didn't even think of. So the bench grinder built with that motor is out. I think that motor might be a good candidate for a 2x72 belt grinder in the future, or a band saw maybe. Those two things are much farther out in the future. In the near future I will probably just buy a bench grinder or small inexpensive belt grinder to get things done while planning for the longer term I'm also wondering if it might be a power source for a small power hammer. That's a topic for a lot more research though. How much power do tire hammers need? Can they be run electrically at all? I dunno. Might be an interesting application for a strong treadmill motor, especially if I can do it safely and cheaply. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted January 2, 2021 Share Posted January 2, 2021 Most tire power hammers are driven by an electric motor, quite successfully I might add. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 2, 2021 Author Share Posted January 2, 2021 I know so little about power hammers. I saw that there are a bunch of pneumatic ones, and those seem to be the most prominent, or at least most marketed. I haven't seen any electric ones, though given power hammer prices I haven't looked very hard. Might be worth a lot more research. Quote Link to comment Share on other sites More sharing options...
twigg Posted January 2, 2021 Share Posted January 2, 2021 I'm gonna guess it's not totally enclosed since it came off an indoor appliance. Not ideal for a belt grinder. As far as a power hammer, I think you'd need a very large gear reduction to get the beats-per-minute to a reasonable level from 3500 RPM (to get it to 2 beats per second you'd need a reduction of 1:29). One of the people here who actually use/build power hammers should correct me if I'm wrong. I'm guessing that for power hammers most people would opt for a motor with more poles / lower speed. If I recall correctly, induction motors' torque drops off at low speed, so the speed controller you salvaged won't help you for a power hammer. That being said, maybe this motor is such overkill at 2.5 hp that you could find a happy middle ground with some electrical speed reduction and some mechanical speed reduction. I dunno! I was in your shoes a week ago or so with a motor I got from the scrapyard. After a week of sifting through belt grinder and power hammer build designs, it's still sitting on my shelf taking up space for the same two reasons: not enclosed and too fast. I like the bandsaw idea! With the variable speed control, if you built the frame stiff, you could cut wood or metal. Still not ideal because it's not enclosed from dust, but there's no way around that. I like the garden gnome artillery too. You just need a big flywheel and a dog clutch... Like a flywheel punch press but for sending gnomes at escape velocity! Edit: out of curiosity, how many input amps is the motor rated for? Just curious because my 1 HP, 3450 RPM motor is rated for 17.8A, which will (eventually) throw a 15A household breaker. Mine could just have a crudtastic power factor. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 2, 2021 Author Share Posted January 2, 2021 The motor is not enclosed. I figure building an enclosure should not be too hard. A vacuum filter on an opening in a shell. Seal the shell otherwise. A bushing over the shaft to seal against crap gettin on the bearing. Quote Link to comment Share on other sites More sharing options...
pnut Posted January 2, 2021 Share Posted January 2, 2021 A DaVinci cam power hammer would be pretty simple to build using that motor and a spring assist for the down stroke on the hammer. Pnut Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 2, 2021 Share Posted January 2, 2021 Almost all power hammers I have seen were powered by an electric motor *somewhere*, even the pneumatic ones. The exceptions were the helve hammers and pneumatic hammers run by water wheels and the lineshaft powered shops using a gas engine for primary power. The little Giant website has specs for those hammers with a 25# LG using a 1 hp motor at 1725 rpm and 50# LG using a 2hp motor at 1725 rpm; I have heard suggested that using a *slightly* larger hp motor will make it a bit more lively. I scrounged a 1.75 hp TEFC motor in great shape for my 25# LG rebuild. Ran me US$10 at the scrapyard when they redid a building on campus and scrapped all the HVAC stuff... Quote Link to comment Share on other sites More sharing options...
Welshj Posted January 3, 2021 Share Posted January 3, 2021 I am not an expert by any means... but from my understanding- "most" treadmills are DC powered making it easier to set different speeds for the belt. I would probably Google the specs on the motor, model number etc... are you sure its 120v AC motor? If it is a DC motor, 120v ac will probably kill it quick? Just asking because a DC treadmill motor is a project I've had in mind for awhile for a sander set up. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 3, 2021 Author Share Posted January 3, 2021 IIRC it says 150vac on the motor placard. It's in extra innings at this point, so if it dies while I am bench testing it, I'm not worried. The treadmill itself spent some time outside in all weather, so it may not work at all. The control board died for certain so I tore it all down to harvest the steel from it. the motor was a bonus, as were the rollers, though I don't know exactly know what I will use them for right now. the speed control will come from an AC variable speed control I got from dad ages ago. all I need to do is attach a grounded plug to the motor. the speed control has an ac outlet and a simple dial. So, a little bench testing first, then start designing whatever it is I will be building with it, if anything at all. been reading, and projects may be on hold for a long while. I need to build a shop of some sort, sheltered for everything, before I can do a whole lot. I spent some time trying to list out wants and needs and a big belt sander or power hammer are way down the list. Quote Link to comment Share on other sites More sharing options...
pnut Posted January 3, 2021 Share Posted January 3, 2021 I've never seen a DC powered treadmill. They've all ran from AC current from a wall socket. Pnut Quote Link to comment Share on other sites More sharing options...
twigg Posted January 3, 2021 Share Posted January 3, 2021 I feel like a bit of a dope that I didn't think of building a motor enclosure. Good idea Paul! I'd love to see what you come up with. I think in your case the stars are aligning towards a belt grinder or band saw. One other thing to check is whether or not that speed controller can handle 2.5hp of oomph. I don't think I've ever seen one that big for 120V-to-120V controllers. Quote Link to comment Share on other sites More sharing options...
Welshj Posted January 3, 2021 Share Posted January 3, 2021 Theres a couple descriptions and you tube videos of grinder build here with various motors. I dont believe its a commercial site? https://www.homemadetools.net/homemade-belt-sander Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 4, 2021 Author Share Posted January 4, 2021 Twigg, the motor enclosure will just be a wood box big enough to cover the motor and flywheel with a hole bored on one side with a bearing or bushing to create a seal of sorts so that the motors bearings don't get fouled. The box will then have a fairly good sized series of slot holes that can be covered with a filter so that air can actually get to the motor to keep it cool. the goal is to keep metal particulates from getting in there and causing problems. My first thought was to use sheet metal for the motor enclosure, but I don't think that sheet metal would really add anything to it. The whole idea is just to keep particulates out while allowing enough airflow for cooling. When I get around to bench testing I may decide it also needs a fan in the enclosure to move enough air. My speed controller is an old sears branded thing dad got a long time ago. If it works, great. If not, I'll have to figure something else out. After reading everything here, including the associated rabbit holes, I think what I will do is simply bench test it, see what kind of hoops I can make the motor jump through, and possibly build a mount and enclosure for it then set it aside for a while with associated notes. In the meantime, for grinding and sanding I will probably just save for a simple belt sander and perhaps a bench grinder from Menards of Harbor Freight, or even craigslist. That will let me do the things that need doing while I work on creating or adapting a space for the finish work on various things and eventually blades. Depending on the shop I build for myself, I may even turn that motor into a power hammer. I'm not in a rush. I still need to be able to reliably turn out a leaf, so I can wait on the big stuff Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 4, 2021 Share Posted January 4, 2021 I'd definitely add a fan(s) if you will be filtering for fine particulates. As I recall summer does get hot in Kansas! (I married a Kansas Lady around 36.5 years ago and her tales of summers pre-air conditioning come to mind...) Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 4, 2021 Author Share Posted January 4, 2021 We do hit triple digits. It's not horrible humidity wise, but not as dry as your neck of the woods. The heat lingers even after the sun goes down. Makes me miss Albuquerque. My 100 year old house out here does have central AC, but the second floor is a penance without room air conditioners. I think the guy who designed the HVAC didn't really have much of a clue. when he put the duct work in who knows how many years ago. It would be great if I could get a balanced fan to afix directly to the shaft of the motor itself. that would keep things simple from an electronics standpoint. the downside is that there would be no cooling without actually running it. I could also use a microwave fan (of course being very careful to extract it safely and making sure the capacitors are discharged first), or maybe even a disused vacuum fan. If it could run steadily and draw enough air through the filter that would be perfect. Come to think of it, just have the whole thing plug into a switched power strip and use two plugs, one for fan, one for motor. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted January 4, 2021 Share Posted January 4, 2021 On 1/3/2021 at 1:16 AM, Paul TIKI said: IIRC it says 150vac on the motor placard. had my electrical license over 35 years, and never saw 150 VAC provided in the USA or anywhere maybe I need to get out more Quote Link to comment Share on other sites More sharing options...
Deimos Posted January 4, 2021 Share Posted January 4, 2021 Maybe it was the motor starting capacitor? Those come in 150 VAC. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 4, 2021 Author Share Posted January 4, 2021 I remember the 150 clearly because it was odd. I need to get a picture of the placard and share it. The VAC part may be one of those Mandela effects where you are sure you saw it, but maybe didn't (like for several years a lot of people were certain that Nelson Mandela was dead but he wasn't). It's a brushless motor, very simply connected to the control board. The control board was toast though. could have been a reference to the capacitor. Could also be a Max voltage sort of thing. "This motor will run up to 150 volts at 3600 rpm...." I had a job doing the final assembly on a variety of electric motors, mostly DC brushed motors, but occasionally some AC and I'm now trying to remember how the difference was listed on the placards there. It was more than 10 years ago though. I really do need to test the thing and look at the placard again. Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 5, 2021 Author Share Posted January 5, 2021 Aha! I looked at the motor an discovered something important: I am an Idiot! Ok, the placard is fairly large. When looking for things like volts an amps and horsepower I found them in an easy to read section towards the bottom of the placard. Hp 2.5. RPM 3750 Amps 16 and Volts 150. Here is where I found out the old neurons weren't working together. The top of the placard had, in large letters, VARIABLE SPEE <SMUDGE> MOTOR. I then scraped off the smudge and found DC. So it is not a variable speed ac motor. It does not indicate 150VAC. It does, however, indicate that I am too silly to clear off a smudge of dirt that would have saved much confusion. Sorry about that guys. Still, it would make a good motor for a number of applications just as soon as I undo my cranio-rectal inversion. I just have to figure out how to make a proper DC speed controller Quote Link to comment Share on other sites More sharing options...
twigg Posted January 5, 2021 Share Posted January 5, 2021 I was in the midst of writing a response when I saw your post and now it's all out the window I got very confused seeing the 3750 RPMs until I read the DC part Dang, I would have loved to see the rest of the electronics in that treadmill. It seems to a dummy like me like the manufacturers did everything the hardest possible way! Rectification losses and speed control? Yikes. Power company's best friends. They must've had some monster MOSFETs in there somewhere for a honkin' boost converter! Just doing some maths here, there's no way that runs on a 120V / 15A household circuit. 150V at 16A? That *might* work on a dedicated 120V / 20A breaker. By my math, 150V * 16A = 20A * 120V, so it'd be real tight. Is that placard for just the motor or the whole treadmill? Cause if it's for just the motor, I'm even more confused, because when you add in the power lost in rectification and the power consumed by the speed controller, it goes over a 20A circuit breaker. I guess if you're hardcore and run too fast, you trip the breaker?? Lol talk about making the customer feel like a champ. Outrunning the power grid! Quote Link to comment Share on other sites More sharing options...
Paul TIKI Posted January 5, 2021 Author Share Posted January 5, 2021 I don't know about the maths on that. I do know that to guess by the belts from the motor to the tread there wasn't much in the way of gear reduction, I have a feeling that those numbers are maximums. If you provide the motor 150v and 16 amps you get 3750 rpm at 2.5 hp. Less current, less output. Which would make sense. We ran that thing for a while before we moved and it never tripped the breaker, even at "top" speed. I don't think it was ever meant to run flat out on that much current. It's just that it can if you put the spurs to it. Though it would be fun if the marketing material told people to outrun the grid Quote Link to comment Share on other sites More sharing options...
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