Pistol grip for a laser

The laser is almost done. Like everything I build, it'll be a half-functioning shadow of what I imagined. But it is bright as fuck; you can feel the heat on the palm of your hand a meter away. I got the final focusing from a lens taken out of an old rifle scope.

The final step is putting a grip on it. Once again, I just have to say how much I love 3D printers. You dream that shit up and you can print it...



triggerX = 25;

triggerZ = 21;

triggerRad = 18/2;

module grip()

{

difference()

{

union()

{

rotate([0,10,0])

cylinder(h=115, r1=17, r2=26, center=true);

translate([triggerX,0,triggerZ])

{

translate([0,0,triggerRad+3])

rotate([0,90+15,0])

{

cube([(triggerRad+3)*2, (triggerRad+3)*2,26],center=true);

}

rotate([0,90+15,0])

{

cylinder(h=20,r=triggerRad+3,center=true);

}

}

}

union()

{

translate([0,50+17,0])

cube([100,100,200],center=true);

translate([0,-50-17,0])

cube([100,100,200],center=true);

translate([triggerX,0,triggerZ])

rotate([0,90+15,0])

union()

{

cylinder(h=22,r=triggerRad,center=true);

cylinder(h=100,r=4,center=true);

}

}

}

translate([6,0,-55])

sphere(r=10);

translate([12,0,-35])

sphere(r=10);

translate([18,0,-15])

sphere(r=10);

}

//grip();

module printableGrip()

{

union()

{

translate([5,0,2.5])

{

difference()

{

cube([70,65,5], center=true);

union()

{

translate([25,55/2,0])

cylinder(h=100,r=2.6,center=true);

translate([0,55/2,0])

cylinder(h=100,r=2.6,center=true);

translate([-25,55/2,0])

cylinder(h=100,r=2.6,center=true);

translate([25,-55/2,0])

cylinder(h=100,r=2.6,center=true);

translate([0,-55/2,0])

cylinder(h=100,r=2.6,center=true);

translate([-25,-55/2,0])

cylinder(h=100,r=2.6,center=true);

}

}

}

difference()

{

translate([0,0,39])

rotate([180,0,0])

grip();

translate([0,0,-50])

cube([100,100,100], center=true);

}

}

}

translate([-5,0,0])

printableGrip();

Welding 101: I have no idea what I'm doing

What the fuck is this thing

The Millermatic 211 is a MIG welder. You press the trigger on the gun and it simultaneously feeds wire, vents inert gas, and creates an arc that generates so much heat it melts up to 1/2" thick steel.

The device is actually pretty straightforward to setup: Plug it in. Take the electrical clamp and attach it to whatever you're welding. Put on a helmet and gloves. Turn on the gas. Turn the machine on. Get in position. Press the trigger and try not to be startled.

The wire is fed from a couple pound spool that you put in the side of the machine. It's got a bunch of equipment to auto-feed that spool. Even auto-feeding the first time up into the gun was easy.

The helmet is fairly advanced. It automatically darkens when it detects UV light. Both the sensitivity of the darkening and the opaqueness can be adjusted. It need batteries. One interesting note: Looking at the sun is also enough to set it off. I still get a bit of a sun-spot on my eyes if I stare at the sun through it.

The gas can is 75% argon and 25% CO2. I have no idea why this mixture. The main goal is getting something inert. Why not all CO2? Why not all argon? I forget how much the tank holds but I do know that when I first slapped the regulator on it the dial registered 2200 PSI. Every square inch of the inside of that tank is holding back 1 ton of pressure. It's probably pretty thick. Still, don't drop it. Since the gas and wire didn't come with the welder I picked it up at a local welding supply shop. I get the impression this is mostly what they ever sell. The other gear was notably over-priced.

The welder itself only has two dials. It has some sort of auto-feeding circuit that means you shouldn't even have to touch one of them. That would be the feed-rate. The other dial is the thickness of the material you're welding. I can only crank it up to 3/16" before I'm supposed to be using a 220 outlet.

How hard can it be...

Fumbling my way through it

Step 1: Don't forget the gas. For the first weld, the one that looks cratered, I forgot to turn on the gas. Aside from looking like shit it is actually weaker. I was able to pull the weld apart. The two below it that are smooth and shiny are actually correctly done. I think in both instances here I've got the power turned down too low, however.

I'd previously cut holes in the angle steel and proceeded to weld the bearings into place by putting a piece of angle steel and doing my best to keep them in place. The originally cut holes, however were not perfect fits, nor were the measurements. Combine that with my inability to place the bearings and I got a final product that essentially didn't work.

So I opted to use the power of the milling machine. I made a set of holders out of wood. Milling wood is both simple and fast. This will allow me to hold all the parts exactly in place while I make the welds. Once I've got spot welds on everything I can go back through and re-weld the hell out of all of it.

In the end I worry I didn't give enough tolerance. I noticed after I'd done all that welding that one of the holders was off a bit. I'll have to wait to get more skate bearings to find out.

I've also considered just replacing this whole ridiculous setup with actual manufactured bearings but that immediately jumps the cost up to about $300 for a set (at least when I order from the generally over-priced McMasterCarr). I'd like to see if I can do this for more like $40. I'm willing to take another shot or two at it even after this.

Hacksaws: Fuck em

First time I used a hacksaw I was ecstatic. Before that, it didn't seem possible to cut materials that were stronger than wood. Materials like aluminum or plastic. Since then, I've had to use a hacksaw (without a vice) for jobs as rough as cutting 1/4" thick, 2" wide steel I-beams. That takes forever and it's a workout.

Metal band saws are equally revolutionary. For something that would have taken 15-30 minutes and been shitty, I now do in about 30 seconds and it's perfect. Look at that edge: It's an exact 90 degree angle, single cut, super crisp. You can barely even seethe saw lines. 30 seconds.

Touching a far away world

This is a welding table. It's put together with bolds. I don't know what the bolts are made out of by it's not steel. Perhaps chips of old people's bones.

And it was made by hand. I can tell because the maker stripped out one of those bolts putting it together. A machine would have just fucked it up and given some error. This dude packed nicely, still totally broken, with the bolt but missing the nut he stripped. I didn't even notice it was wrong till I tried to put it together.

I think it's cute in a way that this person is probably just as annoyed with the low quality of the bolts that strip all the time as the customers whose stuff doesn't work the first time. I hope that person doesn't sweat it; we'll find extra bolts and in the end it's the cheap as company cutting those corners.

It makes you wonder a lot about that person. A tiny connection across the global distribution void.

Macroscopic engineering: Apartments come with 240V outlets

Two important points: #1. Apartments usually come with 240V outlets. #2. You probably don't need them.

Washer/dryer and ovens often require higher power and can come in 240V models. As a result, even residential places often come with high-power outlets. My apartment was build about two years ago and it has both a 30A and a 40A circuit in it.

Of course, light industrial machines don't seem to even need that. For instance the Bandsaw I just bought only takes 7A (vs the standard 120V 15A circuit). Similarly, the MIG welder I'm going to use goes up to 20A on 120V but will probably stay below the 15A limit if I keep it turned down (we'll see).



On the subject of light industrial equipment in your apartment, I've also moved the accelerator target to down the hall to make room for all that swanky new shit.

I'd like to also give a shout out to Hazard Factory's founder Rusty. I took their welding class as an intro to heavier metal working. In part I loved it for being very informative and helpful for actually learning welding. In part I loved it because Rusty is like the nicest guy ever. You look him up on facebook and every single picture is of him smiling. I'd like to be such a person.

ME: Paper

Process

Getting into the specifics of the design, paper and imagination was absolutely the fastest way to find basic flaws in construction. It's far faster than CAD or building it even if you're trying to make clean drawings.

Once the design is a bit more final, CAD seems like a solid choice again. This time, not using a bunch of exacting math or trying to model it all but instead just using the values you know you will and trying to get things close. I'll add more to this cad drawing as time goes on.

The problem I was solving

Lets imagine how the grabber will work. There's the threaded rod. On either side of the rod are bearings. On one end there's also a gear that the motor connects with to turn it. Sliding along the rod will be the actual grabber arm and it's electromagnet.

This poses already several questions:

#1. What keeps the grabber arm from just rotating as the rod does? We could give the arm bearings to slid along some flat surface. I think instead it's probably easiest to just connect it to the other arm. They're supposed to move in tangent anyways and the cables to power the electromagnets on either side will have to go to both of them anyways. Also, that's just a lot simpler than bearings, which are either a pain or expensive.

#2. Just how close to the user can the table get? Will the fetcher be able to bring the shelf from all the way stowed to right next to the user? Not really. So how closer? If the bearing is there, that's 1.5" and then the arm will actually have to extend over the gear, another bearing at the other end, and the length of the electromagnet. All that will be 4" at least. Now the table is 6.5" away from the user at a minimum.That's getting to be a bit awkward. We'll have to cut out any connection on the far end of the fetcher arms. Either side will extend out a bit but the center will only connect farther back. This also makes the threaded rods more convenient; we won't have to cut those and they only come in 24" while the plan for the table is to be 18" deep. Of course, given that we decided on having a cross piece in #1, we will have some offset. Probably just the width of the cross piece and the electromagnets themselves. 2" seems tolerable.

Macroscopic engineering: Playing with hardware

How to get it

If you've never bought hardware before, I'd recommend two places: Grainger and McMasterCarr. They sell basic parts. Basic like threaded rods and gears.

Of course, there's also Ebay. But then you have to deal with buying things on Ebay: Anything you buy will take forever to ship, you'll never be able to get another one just like it, you have to shop for it using the Ebay interface which is not at all designed to help you find the right part.

Chains

One of my options for how to raise and lower the fetching shelf is to have threaded rods that can be turned to push it up or down. However, if I put that rod off to one side of the fetching shelf it will torque the shelf as it goes up. I'll need a threaded rod on each side. But I want to make sure they rotate at exactly the same time or else I'll again be torquing the shelf. So my plan is to have a chain that connects them. A single motor will drive the chain.

Originally I was thinking bike chain. It's strong enough. It's universal. There's just one problem: it's only ever used on bikes. You want to buy a bike gear that's 1/2” instead of the really specific hub threading? Well no dice, because that's all anyone ever uses bike chain for.

The rest of industry uses something called 'roller chain'. In fact, #40 roller chain is just a wider, beefier, version of the standard #40 bike chain. And when you go to that, you can get all sorts of random gears and other quipment.

Grabbers

The grabber itself will have to have a way of holding onto a shelf it's grabbing. A claw which hooks around the shelf would get complicated. Perhaps it would be a solenoid with a spring to counteract the electromagnet and it would push a pin through a hole in the shelf to grab it. That's a lot of parts. You also need to find the hole or slot in the shelf to grab on to. And you'll need to put a lot of lateral force on the pin to pull the shelf out.

The alternative is an electromagnet that can latch on to the side of a table. I picked one up that's intended to be used on locking doors and can hold at least 100lbs when powered at 20V. Running it at 14V I saw a 14mA power draw and it was invincibly strong. The only downside I saw was that it would never let go. After turning off the power on it for 2 minutes I was still unable to unstick it from the metal plate it was on unless I used significant force. Running it at 5V was able to get objects off in about 30 seconds. If it's actually too weak to pull the shelf at 5V, I'll just bump it back to a higher voltage and have a counter-acting magnet on each shelf to hold it once the grabber is supposed to have let go, as opposed to relying on friction to separate them when the engine starts pulling the magnet back.