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Fun With Metal! Welding is Fundemental!

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Metalworking project updates [Jul. 6th, 2014|06:54 pm]
Fun With Metal! Welding is Fundemental!


[Current Music |Dirty White Boy - Foreigner]

Ok, so here it is after a bit longer of a delay than I had anticipated, but I have finally made enough progress on my base metalworking project that I can start work, and soliciting feedback, on all the daughter projects. Last fall I built this:

No, not the tractor, the pointy bits attached to the front of it. That, dear readers, is a Concord grape pre-pruner. The business end is a repurposed hay sickle, made to run off a salvaged hydraulic motor with a homemade crankshaft/gearbox to make the blades reciprocate. It's attached to the front frame of my Kubota with a 3-axis (X, Y, Tilt) tool carrier I also built as my first-time welding/fabrication project. I used it this spring to prune 50 acres of Concord grapes on my family farm in a fraction of the time it used to take doing it by hand. There were quite a few bugs I had to deal with along the way, making it slower-going than it would have been error-free, but either way it's a major improvement from the previous prototype:

As far as the pruner head itself goes, my main problem is with the crankshaft; it's made from a mild steel disk with a splined shaft coupler welded to the motor side, and a bolt welded to the other as the crank pin. It's crude, precise to maybe 0.1", soft as hell and terribly prone to wear. Also, it will hopefully be obsolete by the time I get version 3.0 working, but it's still good to have it as a backup. Either way, those projects are for another post, so back to the base...

The tool carrier is just that: a platform for carrying tools. A different tool bought another tool the previous season to do the pruning, and that whole thing was an absolute disaster. It was massive, being both far too wide to fit down the lanes between the vinrows, and too heavy to mount/unmount from the tractor without also purchasing a forklift or fabbing a jack and stand system that would have been far more complex than my current build, and at the end of the day it's still only a single-purpose tool. Also, it would likely kill you in at least 3 different ways if you looked at if funny.

Learning from all this massive fail, I decided from the start to make my design as modular as possible. Where the Blue Blade of Death had a dedicated hydraulic control box that required loose high-pressure hose lines to be installed IN THE CAB (major no-no) and secure the "on" position with a bungee chord, I paid $5k for the dealership to install a hydraulic manifold in the back with three hold-open toggle switches mounted conveniently on the control panel next to the front-loader lever. Yes, it cost 10x as much as the alternative, but it won't cut you to the bone if it springs a leak at 3000psi, and now I have 5 quick-change hydraulic circuits that can run a whole number of implements that were previously impossible or impractical. Do it right, do it once.

Next, I made each of the 4 articulating joints (including the tool head itself) quick-connect as well. Not only does this modularity make it possible to do an install AND tear down drill in under 20 minutes using only hand tools and zero hoists, but it also allows me to modify each component, refine it and add functionality as I use it and learn from my own mistakes. Which finally brings me to "now" now, just then.

The two main problems with the horizontal arm are 1), it's too wide, and 2), too tight. Even though the pruning head actually sits a few inches narrower than its connecting point, we have fairly random lane widths between our vine rows, and the position of the horizontal hydraulic piston made the opposite side too wide in places, while oddly enough actually limiting the range of travel on the working (right) side of the tractor. I figured out a better geometry for the whole thing, but that ran into an old problem I discovered (and failed to correct) at the start of the build: the receiving square tube that the arm fits into didn't have enough clearance, particularly factoring in the weld seam down the inside of the tube. My original "fix" was to grind a slight groove into the outside of the inner (moving) tube, since I couldn't figure out a way to smooth out the inside of the outer (stationary) tube.

This is what I started trying to repair back in March. But I didn't have a proper workspace, so I went ahead and built a nice big work table in the garage with a long assembly area, easy-access storage for tools and stock, and a much sturdier drilling and milling bench than 'Ol Shakey (which I managed to salvage as a mobile welding table, yay!). Then I tried repeatedly to make a broach from scrap parts to deal with the weld. Fail. Then I managed to fit the neck of my angle grinder far enough into the mount to grind the weld down, but that still didn't help with the weld warping from the outer brackets. Kinda fail. Finally, I got the thing all back together and realized the new geometry required I re-do the horizontal mount anyways, and since I didn't have enough stock left over from before, I got some new tubing with a 3/16 wall instead of 1/4, giving me an extra 1/16 clearance all around. Do that. Always do that from now on.

So, now the horizontal piston pushes right (the working side) instead of left (the slack side I only look at maybe 10-15% of the time wile I'm using the tool), the horizontal arm actually travels more on the working side, making my post hole auger possible (coming post), the vertical piston is positioned to the inside, freeing up about 4" of width as well as vertical travel for lower-positioned tools (like my auger, coming post!), and all the hose connectors face rearward so there's far less chance of snagging them on a vine. I finished this up yesterday. I love my new bandsaw. And my new shop fan.

So, this wraps up my base post on my base post. In the (hopefully nearer) future, I will be updating and asking for advise on the following tool builds and their associated problems:

1) Repairing my v2.0 pruner, specifically help on machining and hardening a much more durable crank. I've been refining my machining skills and setup, and I think I'm going to go with using a 4-jaw independent chuck in a 5c square collet block as a turntable to simply mill out the two eccentrics (a drive pin and a boss for the coupler and just drill out holes for the 9T spline) on either side of a 1" length of rod. I will be purchasing the blank from some online source since my local yard only has mild steel at 5-foot lengths, so I will need some advise on choosing appropriate alloy for heat hardening and easy machinability.

2) Building a hydraulic earth auger for replacing broken trellis posts, because I can't use a shovel anymore with my ankle and my dad is going to work himself to death fixing these damn things if we don't find a more automated option. Mom and I bought him a gas powered auger for Father's Day and it's made his life so much easier, but it's still quite labor intensive to use, so I'd like to have a tractor-mounted auger that uses the same bits. I've already got a low-rpm hydraulic motor from another scrapped project that I'd like to use, but I need to make a custom shaft coupler that has some shock absorption to it as well. I'm going to try my hand at casting it in high-strength urethane rubber (the kind of stuff that mold automotive suspension and motor mount bushings out of), so if anybody has any experience with pattern making and any of those kinds of two-part urethane mixes, I could certainly use some help.

3) Upgrading the pruning head to v3.0. The head needs to be more compact AND provide enough suction to collect the clippings in a bulk bag carried on the rear hitch on the tractor. Common practice is to mulch in-field, but all that woody matter requires a lot of soil nitrogen to break down. A study I found of a vineyard in Australia or wherever removed prunings to compost crates outside of the field and raised from the ground, utilizing free atmospheric nitrogen instead to break it down, and they found their nitrogen fertilizing requirements significantly reduced, while also producing organic compost as a side-product. We found the same drop in nitrogen additives by raking up larger canes when we hand-pruned the first two years, but not only does that not work for the smaller cuttings made by the mechanical pruner, post-removal storage and management is a serious challenge. By directly bagging it as I prune, the wood never touches ground, is stored in water-impermeable standardized containers to aid in composting, storage, and transportation, and if I can demonstrate its benefits I can offer similar machinery to other viticulturists. The design I plan to use is a pair of counter-rotating circular saw blade stacks, probably with narrow impeller vanes laminated between the blades. The head will be about 1/4 the height of the sickle deck while also contouring better to the canopy crown, while providing suction and better particle uniformity at a reduction in mechanical complexity (purely rotational instead of rotational->reciprocal). I'm not going to weld/machine this one, I'm gonna cast it out of aluminum cans. I haven't done this before, so I'm sure I'll make plenty of practice/mistake runs and need some help with that as well. Not sure yet if I'm going to go with greensand or lost-foam, but I'll let you know as I learn.

That's it for now, but I'm sure I'll have plenty more new gadgetry thought up by the time I get through these already-hot irons in the fire. Thanks for reading all the way through, and thanks in advance for any help!