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3/25 Update

Busy few days. Workin hard and playing harder.

In the past couple of days, I made a ton of progress.

I fixed the 2 bushing holes that I messed up, one from a bad freeze-fit, and one from a stupid measurement error. The solution was to weld up the hole and re-bore it. A very time consuming fix. Don’t make that mistake!

I also had to torch away parts of the lower arm to get proper clearance for the cylinder and linkage.

The cylinder space wasn’t accurate because I couldn’t find the spec’s for the cylinders overall diameter, so I assumed it would be 5.5″. Turned out it was 6″. Not a big deal to fix- Just had to torch away the excess. I found where to torch by making an aluminum “mock-up” of the cylinder and using that to guide where to torch.

Torching 3″ is very difficult. Unlike 2″, it requires you to pre-heat the metal from the bottom, or the oxy will have a really hard time making a straight cut. I made the mistake of not pre-heating when I torched the holes in the linkage, and that’s why they came out so badly.

Once I torched away the cylinder space, I could weld the cylinder mount. Should’ve taken video of the process, but it was pretty simple. Basically, I flipped the arm vertically, so the attachment wouldn’t fall, and held it perfectly centered using magnets. After I tacked it, I double checked it’s squareness, and gave a solid 1/4″ fillet all the way around. After that, I ground away any weld material that would block the cylinder. See the photo in the gallery below.

For some reason, the lower arm was interfering with the linkage. I’m still not sure why the linkage space wasn’t right. In the design, I left 1/4″ clearance for it, because I knew there would likely be small measurement errors, and that the lower-arm torching wouldn’t be perfectly accurate. I need to go back and double check all my measurements on the linkage, and the CAD file I sent for torching the lower arm. It could have been as simple as the fact that the torching is only guaranteed by 1/4″ by the metal supplier.

Either way, I torched away the excess, and now it will work.

I also freeze fit the remaining bushings for the hole’s I’ve bored. I will need to do one more batch of freeze fitting when I’ve completed the upper arm. Here’s a vid explaining the pre-heating; you want to get the steel hot enough so it starts changing colors. Didn’t get any shots of putting the bushing in cause my camera ran out of juice.

The final freeze fit got stuck midway thru. I was going to take it to the press to push it in, but the guys volunteered to help me. My little girl muscles weren’t enough to hammer it further in, but Mike’s most certainly were! That’s one heavy hammer.

After the freeze fits, I had to grind down whatever parts of the bushing were sticking out of the material; some of the material was thinner than specified, so the bushings were sticking out. This could cause a problem because when the pins are in, they will need to be clamping down on the entire piece, not just the bushing. If it’s just clamping on the bushing, the metal could end up slipping out further on the bushing, causing the arms to get out of parallel. This would destroy clearance accuracy with the blades, and result in either sloppier cuts, or broken blades.


2/23 Update

Freeze fit bushings in vertical linkages. Still need to finish the second pair. I am slow and frustrated with my slowness and clumsiness.

The first freeze fit

2/21 Update

This durned finger is taking more and more time away from fabrication. I went to the doctor again this morning because it looked infected and it was. They suggested I take time away from working. I worked the rest of today anyways and it felt fine, but now it hurts worse than ever. I’m only working a half day tomorrow. This needs to heal.

Didn’t get much done today, but I’ve figured out how to solve some of the fabrication issues I was facing.

For cutting the main linkage down, I’m going to use uncle’s portable cold cut saw and saw most of the area away. This would probably also be doable with a vertical bandsaw, but ours isn’t in operation. I’ll machine the rest away after sawing. He volunteered to do it for me, and I’ll probably have him do it, because thats one scary looking saw!

The hole I'll torch tomorrow. Inner circle is what I'm torching, outer is approximately the final diameter after boring. I still need to drill a small hole for the torch to start in.

For making the big holes, I’m going to try torching them. We have a motorized circle cutter that can be used with a torch (video to come). This will torch the holes for me and they will be pretty exact. I had considered it before, but shyed away from torching, because we will need to bore to size, and the torching will harden the steel, making it more difficult to machine and more likely to damage bits. My uncle said I don’t need to worry about that, but I’m still going to do a sample with one of the holes to see.

Another option is renting a slugger bit of 2.75″ diameter for this, but I couldn’t find anywhere that rents these out. I’m calling one more place tommorow that a friend recommended. Buying one would be too expensive (~$500) .This would be much easier than torching, as there’s no cleanup involved, and it won’t harden the steel.

Attempting to drill the big holes

I was originally planning on drilling these holes, and had machined our bit for this. After attempting to drill, it was clear that this was not going to be possible. Even though I’d ground flat spots on the bit for the chuck, the chuck kept opening up and losing grip on the bit. I couldn’t get it tight enough to actually drill much. Also, the lowest setting on our drill press is still much too high for using a bit that size. Torching will be much easier.

The other thing I did was drill the center hole and drill and tap the grease holes on the vertical linkages. This is pretty straightforward and easy, a nice change from the way things have been going.

The vertical linkages