Grinder build WIP

R

Ryan J

Joined
Jul 14, 2014
Messages
233
Thought I would post this here to show my build.



This is the motor Ill be using. Yes its from a treadmill. This isn't the best option for use in a grinder. However the treadmill was free and offers all the circuitry needed for variable speed without the expense of a 3 phase motor, which is out of my price range at the moment. The circuitry and motor will need to be protected from metal shavings and dust as the motor is open framed.




Completing some if the circuitry. If you dont have electrical knowledge and experience do not attempt this, this is a 120 volt DC motor. While 120 AC is dangerous enough, DC current is even more so. Improper wiring can kill you in a multitude of ways.

The wiring isn't yet complete in the pictures. As evidenced by the ground to nowhere. I replaced the sliding 10k pot with a rotary type that isn't open to debris.
I used a 6 pole toggle switch inline with the motor to allow the polarity to be reversed so that I can use the top of the belt for convexing and the motor will turn away from me.
I may need to include a cooling fan I dont know yet. When the build is complete I will run it for a bit and check the circuitry. If the control box does need ventilation the holes will have to be filtered. The seams will be sealed with caulking. I painted it with flex seal which made it kind of nice I thought. As well as sealing it. Everything has been tested and is functioning nominally thus far. Again this is isn't the ideal way to go about this. But for a guy like me with more time then money and moderately handy it will be a big step up from nothing. Total build cost tops out at $35 so far. The only things I need to buy that wasnt on the treadmill are idler wheels. I was fortunate in that my treadmill doesn't need the speed sensor that has been the cause for grief with others. It was in no way connected to the motor circuitry, only to the odometer/calorie counter.



All buttoned up. From left to right.
Two position power switch. Down makes the belt spin down. Up makes it spin up.
Potentiometer for speed control.
Up/down toggle. This is the switch for the treadmills incline motor. I'll be using it for powered belt tension.
15 amp circuit breaker. It was in the treadmill so I included it. Also for safety there is a thermal switch in the motor.

Thats all for now. Will update as I make progress if anyone wants. Waiting on idler wheels as of now. The treadmill had enough steel tubing to build two grinders.
 
".....Up/down toggle. This is the switch for the treadmills incline motor. I'll be using it for powered belt tension. ....."

Cool as that sounds, this is a really bad idea. Belt tension is not a powered thing. A spring or gas cylinder is what you want. When setting the tension, you need to "feel" the resistance. Different belts run at different tension, too. Additionally, remember that in grinders, KISS is the best rule.
 
Stacy E. Apelt - Bladesmith said:
".....Up/down toggle. This is the switch for the treadmills incline motor. I'll be using it for powered belt tension. ....."

Cool as that sounds, this is a really bad idea. Belt tension is not a powered thing. A spring or gas cylinder is what you want. When setting the tension, you need to "feel" the resistance. Different belts run at different tension, too. Additionally, remember that in grinders, KISS is the best rule.
Click to expand...

If you have a spring or piston how do account for different belts requiring different tensions? It really is simple. It's just an electric piston. You can feel the tension by putting one hand on the belt. The reason Im doing it like this is because I wont need the platen arm to be adjustable in and out like most grinders. I can use the metal I have instead of finding two tubes that fit inside each other. Its more simple this way. Have you tried it? No way to know of works without trying
 
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Ryan - How many inches of up/down travel will the tensioner wheel have with this electrical positioner? While there is some difference in tension wheel movement for different belts, brand as well as new vs old belts (there is some variation there), the big difference is when you change from a 8" or 10" contact wheel to platen, the arm needs sliding to a different position, OR if you decide to use a small wheel attachment in future.

I understand the hassle of getting two tubes that will slide inside each other for the arm. The easiest, less expensive fix I found was to order 2 pieces of 1-1/2" flat bar and 2 of 2-1/2" flat bar 12" long each (1/2" thick) and a 24" piece of 1.5" aluminum bar - total cost for all is around $40 to $45 shipped. Bolt them together using 1/4" bolts and you've got the "tube" and the bar to slide in 'n out.

Good luck with your grinder -

Ken H>
 
If you have a spring or piston how do account for different belts requiring different tensions?
Click to expand...

Ryan - just realized I missed that question. The position of the 1.5" arm sliding in 'n out will vary the belt tension using springs. I ordered a gas spring piston to use on this last grinder, but after reading the seals didn't last very long, I decided to use a spring instead. It's amazing how much pressure it takes on the belts to make them run true. Sometimes too little belt tension will induce a bit of belt wobble.

Ken H>
 
Ken H> said:
Ryan - How many inches of up/down travel will the tensioner wheel have with this electrical positioner? While there is some difference in tension wheel movement for different belts, brand as well as new vs old belts (there is some variation there), the big difference is when you change from a 8" or 10" contact wheel to platen, the arm needs sliding to a different position, OR if you decide to use a small wheel attachment in future.

I understand the hassle of getting two tubes that will slide inside each other for the arm. The easiest, less expensive fix I found was to order 2 pieces of 1-1/2" flat bar and 2 of 2-1/2" flat bar 12" long each (1/2" thick) and a 24" piece of 1.5" aluminum bar - total cost for all is around $40 to $45 shipped. Bolt them together using 1/4" bolts and you've got the "tube" and the bar to slide in 'n out.

Good luck with your grinder -

Ken H>
Click to expand...

Haven't decided yet. After I mock it up Ill get a better idea how much I need. The cogged shaft that the motor pulls and pushes has about 6 inches of travel. I could add more by positioning the tracking wheel further from the pivot point at the expense of some pulling power. It has a lot of force though. It's geared down so far it moves maybe 1/2 per second with the motor spinning like crazy. This is good because it doesn't push so fast that setting it will be difficult. Ill measure the pulling force and make a mark to stop it at the 35lbs 3m recommends and try it out. At this point its just a concept Im going to try. Might be great might not work. As an aside I have a spring to use if this doesn't work. I was thinking about where I could scavenge one. I put a screen door closer in a vice and pulled on it with a fish scale. Happens that it pulls with 35 lbs of force about 1 inch from fully extended. The last 3 inches are between 30 and 35 lbs so it should work.
If I do end up needing a spring Ill use your idea though. Where did you order the metal?
 
Here's the link to 1/2" flat bar: http://www.industrialmetalsales.com/1-2-Thick_c69.htm You can look on same site for some 1.5" square. I see the 1.5" square is $20 for 24", but $20 for 36" which would give you two arms, one for flat platen and one for contact or small wheel arm. I use my small wheel more than the contact wheel.

Note, I did find a compression spring works better than the extension spring mounted behind tension arm. Seems to track better, and this has been confirmed by a few other folks building grinders. I don't understand why it works better, just seems to.

I'm sure interested in seeing some photos of your electrical tensioning wheel, either on here, or via email.

Ken H>
 
Ken H> said:
Here's the link to 1/2" flat bar: http://www.industrialmetalsales.com/1-2-Thick_c69.htm You can look on same site for some 1.5" square. I see the 1.5" square is $20 for 24", but $20 for 36" which would give you two arms, one for flat platen and one for contact or small wheel arm. I use my small wheel more than the contact wheel.

Note, I did find a compression spring works better than the extension spring mounted behind tension arm. Seems to track better, and this has been confirmed by a few other folks building grinders. I don't understand why it works better, just seems to.

I'm sure interested in seeing some photos of your electrical tensioning wheel, either on here, or via email.

Ken H>
Click to expand...

Thanks for the link and info. Ill post pics when I get it up and going. It'll be a few weeks because I'm to broke to pay attention. Hopefully starting a new job. And its an machine shop with Cnc machines. :) since I have to put pics up now I have to make it pretty lol. The motor is completely exposed so the hard part will be making a sheet metal housing. I have some plans. I was going to mount the setup on the back like an extension spring but after reading your post Ill put it in the front. In my mind it seems like this would add stabilization to the tracking arm as well.
 
Hey, working a machine shop with CNC machines? WOW - just think of all the goodies that can work done during lunch or after hours (well, I know that's not possible at all places of work).

Making it pretty is one of the things I'm not very good at myself when working on my stuff (tools, jigs, etc), but I am trying to get better. BUT, it's sure hard to change 67 yrs of bad habits {G}

Ken
 
Made a little progress so here's an update.
I needed to be able to mount the 3" tall by 2.25" skateboard wheel onto the motors drive shaft. This wheel will give me a belt speed of 4796 fpm which I've been told is plenty. I was going to use a separate axle with pillow blocks to mount my drive wheel on, but a user on here informed me that direct drive is much smoother. Starting out the motor looked like this.



This isn't the motor I used but I neglected to take a before picture. It's similar. The reason I posted this pic is to show the giant flywheel. Certainly can't mount anything to that so it had to go. This wasn't easy. Couldn't get the motors shaft to hold still to spin off the flywheel. One advantage of working on this motor is that to make the parts you can use it like a lathe. I clamped it in a vice, turned it on about a quarter speed, and used a hack saw to cut the smaller threaded portion into three pieces.
This is the hub a skateboard wheel. My wheel will be of a larger diameter but the hubs are a standard size so I used this one to mock everything up.

[img=http://s28.postimg.org/6tzp6rpm1/IMAG0066.jpg]

The shaft on the motor was slightly bigger then the inside of the hub. I considered a few options before deciding to turn the shaft down and leave a lip for the wheel to tighten against. The shaft was relatively soft and this didn't take long. This is how that looked.



Now the wheel fits snuggly with no play and can't slide past the lip I left.



Rather then try to find a left hand thread nut that fits the shaft I decided to use one of the threaded pieces I cut off the flywheel.

[img=http://s27.postimg.org/jm6cqm30v/IMAG0068.jpg]

This would work for this wheel but mine is 1.5 inches wider. So either I need to cut a hole in the wheel for the nut which I decided against because it would weaken the wheel, or turn down the nut. Well better get to it then. This took awhile. That thing laughed at my double cut file. Ended up using a grinding wheel on the Dremel and using them so the turned into each other in opposite directions. I found if I pushed to hard the nut would come out of round so slow and steady until it was done.

[img=http://s27.postimg.org/suzssme33/IMAG0072.jpg]

A perfect fit. To tighten it down I'll drill two small holes and use a spanner. Probably red lock tight as well. I know this isn't a solid billet aluminum wheel with a key way and set screw cnc'd to 1/10000th. But the whole purpose is to use some brain power because I have more of that then money. And because it's fun. My wheels should be here this week. Next step is making a sheet metal housing for the motor with filters and a cooling fan.
Edit: Sorry you have to click the links don't know why the last pics are like that.
 
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Ryan - you da man!! Shows real thinking and dedication with the work you're doing, true thinking "outside the box". Can you use the flange I see left on motor to direct mount? I was one of the folks who said "pulley's are just fine", until I tried the direct mount and realized just how smooth it was. The grinder with direct drive is now smooth enough to balance a nickel on edge while running 4,000 SFPM!

Keep posting updates to project with photos! I'm still looking forward to some photos of the powered tension wheel that doesn't use a sliding arm for belt adjustments.

Ken H>
 
Thanks for the encouragement and for the advice on direct drive. Yep my drive wheel will mount right up when it comes in. Here's a pic of the incline motor I'm going to try out for a tensioner. You can get a pretty good idea how it works by looking at it. The cogged shaft moves up and down. I know I'll have to make a housing for it. Going to enclose it completely in sheet metal. No ventilation since it will only be used every once and a while. It should be rock solid. When it's not in use you can stand on the shaft and it doesn't budge.

 
That's going to make an interesting tensioner - looking forward to seeing how it works. Always a better mouse trap, just a matter of finding it.

Ken H>
 
Okay its been quite some time. Ended up getting the machine shop job and bought a house so I've been busy. As a bonus the house has a 30x24 steel shop. Anyway, I was able to make a little more progress today so here's an update.



All of the metal came from the treadmill frame. Basically today and yesterday I cut out the motor mount and worked out the tensioner/tracking wheel arm. You can see how the incline motor will serve as the tensioner. Again this is just an idea and may or may not work. It will be easy to substitute a spring if the design is inadequate. As of yet nothing is welded together. I am going with a flat platen for grinding. It will br removable in case later on I decide to use (and can afford) a contact wheel. Total investment to this point - $40. Which would of been less if a 4 1/2" x 3/8" bolt wasn't $2.50 here. But that's another discussion.
It looks pretty rough right now. Especially where the tension arm bolts on. But it will all be flattened and squared before final assembly.
 
Here's a link to a short video of the incline motor in action. I'm hoping the advantage it will offer is that it's rock solid. My theory is that it will be like having the correct tension on a solid system if that makes sense. It It doesn't budge no matter how much of my weight I put on it, even with the slight mechanical advantage that pushing on the end of arm. https://vid.me/lHgC I'm not sure if the tension arm twisting will be a problem. If it is i will move the mount to the wheel side or possibly in the center.
 
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Congrats Ryan - sounds like you've got a NICE shop now. Sure is smooth action in the video - thanks for posting link. We'll be following thread.

Ken H>
 
Reading along with interest. A shame you had to remove the flywheel, it's part of the HP rating. I like how you are reusing much of the treadmill including the incline.
 
Wormil said:
Reading along with interest. A shame you had to remove the flywheel, it's part of the HP rating. I like how you are reusing much of the treadmill including the incline.
Click to expand...

Yeah I didnt want to remove the flywheel. I've mounted the motor and an idler to a workbench and put a belt on it for testing. Pretty sure I'm gonna be alright without it. I couldn't bog it down. Threw sparks 4 feet lol. It was awesome. Just couldn't figure out a way to do direct drive with the flywheel attached.
Thanks for us encouragement guys. Motivates me to get back out there and get some more done today on it.
A concern I have is that the hinge point for the tension am won't be strong enough and the tension arm may twist under pressure and throw off the tracking. I don't expect the first assembled test to be flawless however, and I can work out the bugs when they poke their heads out
 
Made a small amount of progress today. Got the tracking arm sorted out I think. It took awhile because the first design had to be scrapped. Plus working on the pavement in the driveway because I need to run power to the shop. Heres what I came up with.
Starting to resemble a grinder.

Heres a top down view. My plan is to put rubber bushings on both bolts between the wheel mount piece and the arm to allow it to move. The bracket beside the wheel mount keeps it square.



Heres a front view. Im going to weld a nut to the bottom piece under the arm so that a bolt can thread through to push the bottom of the tracking wheel mount out for adjustment. Then a plate will be welded over the front to cover the holes. The plate will overlap the wheel mount so that its held square from both sides. Im hoping the belt tension will pull the mount against the bolt tight enough. It looks like its out of whack because just two screws are holding it together. In the end I'll weld ot together, remove all the screws, and plug the holes.



If anyone sees any flaws with my design or theories please let me know before I get any further. But go easy on me lol Im a carpenter not a machinist. Ive never built anything from metal. Im considering scrapping the bolts and rubber bushings for a hinge. Especially since a hinge would keep the mount square as well. My other concern is that the tubing isnt thick enough. Its pretty beat up and out of square. I'll beat it back before final assembly as best I can. I could go buy thicker tubing. But its kinda become a challenge to myself to build the thing from salvaged and scavenged pieces. And Im learning. Have a feeling I'll be building another in the future with thicker tubing and hardware. And Id like a heavy barrel hinge for the tension arm pivot. For now I'm having fun with it though.
 
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