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I'm trying to keep it smallish because I don't have a very large work area. In the pic, the blue line is the belt. Green is attached to the motor and yellow are rollers.

(The two rendered pics are before I added the fifth roller). As it sits the belt path is 71.2 inches. Total length is 25". Height is 19".

 

Belt tracking adjustment isn't in the pics by the way.

 

Go easy. I'm not a mechanical designer. :)

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Edited by Daniel Sheets
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Three things jumped out at me.  The first was that your fifth roller is going to get chewed up pretty fast as the grit side of your belt will be making contact with it.  The second is that you would have to wire your motor backwards in order to get it to run the proper direction.  Lastly, while I was confirming the direction thing in my head, I noticed that it's going to be a royal pain in the butt to get your belts on and off with the motor sitting on that side of the grinder. 

 

I would highly recommend flipping the motor over to the other side of the unit.  It would solve the last two problems.   Also, if space is a concern, consider downsizing to something like a 2x48 instead of a 2x72.  Belt availability is the same (except for maybe some of the highly specialized belts) and it can be made much smaller.  You may lose a bit of versatility depending on what tooling you put in, but it would still be a highly effective machine.

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Well I'm teaching myself to weld in the process but it's coming along. It ain't pretty but it'll look better once it's sanded and painted. I took your advice Alex and went with 2x48.

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What are you using to weld with?

Somethings wrong... 

 

Show me a closer shot of your weld joint, tell me what you're using- gas, or flux core, wire size, welder etc.

 

See if we can give you tips.

 

Just judging from what I can see- your  amperage/voltage is too low. Your gas flow is too low not enough shielding... something.

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Posted (edited)

It's a forney 140 flux core. Wire is .03.  I literally just started yesterday (having only used arc welders in high school shop class almost 30 years ago). I practiced on a few pieces but I'm not the most patient person. I don't much care how it looks as long as it holds together. I threw it on the floor a few times and nothing fell off. Haha

Edited by Daniel Sheets
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Well, I've owned a wire welder for twenty years. Worked as a fabricator/mechanic, autobody, and now - sign shop fabrication. Just to give you an idea.

 

You're not burning in and penetrating the metal enough.

 

The head of your welding end- or "stinger" as I call it... should be no more than 3/8" to 1/2" off the welding surface at all times. Tilt to the side so you can see the wire hit the metal.

 

If you're having problems keeping it there- like it bounces off... slow down your wire feed speed til you can keep it steady.

 

If the wire burns up too fast, (glows and just burns off) turn it up a bit. You want a happy medium tween the two.

 

You should have a constant buzzing sound when welding a strip. It shouldn't chatter.

Just like arc welding.

 

It sounds dumb... but make sure you have enough light around you to see. The welder flashes brightly- but you want to be able to see the seam you're welding too.

 

Focus on the bright spot. Your helmet, if adjustable auto darkening- should be dark enough to comfortably see the welding, but light enough to see whats around it too.

 

You want to watch the "puddle" of steel as it burns & melts. How you move the stinger, and how fast you're feeding wire- will let you control that puddle. It should be relatively slow going, smooth movement, to keep that puddle going.

Again, like arc welding.

 

You learn to "know" where you're going, welding to- while focusing on the puddle. You should be moving slightly from side to side- across the seam you're welding, moving that puddle across it to meld the steels together. The wider that bead, the stronger your weld between it.

 

You should have smooth overlapping arcs in your bead from where you slowly move the molten puddle and add to it.

 

Its all about the practice man... the more you do, the better you'll get.

 

Don't adjust more than one setting at a time.

Weld, adjust amperage or feed. Weld, then adjust the other, bit by bit til you find the sweet spot.

Edited by Welsh joel
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Posted (edited)

Thanks for the tips.

 

The helmet I have now is borrowed. It's not auto darkening. I'm not sure what the shade number is but all I can see is the arc. I can't see the puddle behind it so I'm thinking it's too dark for this.

 

I'm working on consistent speed, the ideal distance of the nozzle from the steel, and tweaking the voltage and feed speed.

Edited by Daniel Sheets
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After lots of trial and error this is the final design for the 2x48 I think. I've started the second build based on this design, with proper square tubing, and it's better and more orthogonal. This one has two receivers. One for the tool and one for the work table. Thoughts?

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Looks okay from here. Being right handed I would personally prefer it in mirror image as I often use the ‘slack’ portion of belt at the top and not sure I would like reaching over the machine to do so. 

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Its bit flimsy. My old professor for combustion engines theory always said : "You cannot substitute volume for anything."  With machines like this one its the weight.  If you go to the lenghts of building one, I would go with burned plate design and big axial mounted motor. That will also center the axis on one plane for all the wheels and pulleys.  With todays prices for laser or water cutting this could be done affordably and also with minimum welding, if you are not apt at it. I have 3 HP Engine on mine and it weights 160 pounds without the table on which it stands  and that one is probably another 80# . You can bet there is no vibrations.

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This design seems to follow the way many of the grinders in the market are designed, though my KMG is all built out of .5" slabs of steel rather than tubes.

The one thing that concerns me is the motor.  Pretty much every design I have seen has the motor on the left and all of the wheels on the right (as you stand in front of the machine.)  Perhaps this has to do with motor rotation?  If your motor is reversible, then you don't have an issue, but if you have a standard motor, your design has the belt running away from you, which I think would make for some awkward grinding.  Perhaps I'm missing something.

 

There was a grinder I saw that was built with the wheels all sandwiched between 2 flat plates.

Geoff 

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That's a non-standard motor for a grinder (likely a DC speed controlled motor taken off a treadmill)?  While it appears to be rotating in the correct direction for you you will likely have a different issue with steel dust from the grinder getting into the motor's innards and frying the unit.  I strongly recommend a filtered enclosure of some kind, or at least sourcing a backup for when it breaks down.

 

The other immediate issue I have with your design has to do with the unsupported bolts that are being used to carry the platten wheels.  I'm not sure how much actual grinding you have done on the unit, but the side forces on these wheels can be substantial once you start tensioning the belt to keep it from slipping when youpress hard to grind steel.  The unsupported length of your bolts worries me as a slight  change in alignment can really screw up your tracking.

 

Kudos for getting your own unit working though.  My first one was built up from a partial kit and still gets use in my shop (though the used TW-90 that I lucked into gets lots more...).

 

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Yeah I've thought about dust getting into the motor. And yeah...it's from a treadmill. It's what I had on hand. I plan on getting a fully enclosed AC motor at some point.

 

I've also thought about the wheel bolts. I'm not yet sure how I'm going to address that.

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One option would be to use a hardened shoulder bolt for your wheel axles.   That would help to eliminate flex in the shaft.  Depending on what gauge tubing you are using, you may have to beef it up where the bolt connects to help eliminate flex/vibration around to connection point.

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On 4/30/2021 at 10:22 AM, Daniel Sheets said:

I'm not sure what you mean by reaching over the machine. I'm right handed too and I don't seem to have any issues with this design.

Fair enough, glad it’s not an issue.

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