Rotor-Tiller Repair

[jakeru]

I performed some repairs on an old "merry tiller" rotor-tiller today.
Attachment 1693

The main job was building up the outer tines which were worn down by many years of tilling. I layered on a bunch of 3/32" E70S6 rods using TIG with a good number of passes. The leading edges of the tines were worn into a tapered shape which was especially bad news on the outermost tines, because when they hit rocks on the side of the trench being tilled, the worn tines would thrust sideway on the rock and toss the tiller sideways. The "sharp" tine leading edge shape grabs and flips the rocks out much better. One thing that I figured out that was kind of fun, was using the filler rod and surface tension between it and the molten puddle, to "persuade" the puddle into a certain position (such as, holding it up against gravity) to control its position as it freezes and to control the shape of the solidified material.
Before:
Attachment 1692
After:
Attachment 1690

I also repaired a frayed stainless steel clutch actuating cable. I welded on a solid "loop" of 309L stainless onto it.
Before:
Attachment 1689
After:
Attachment 1688

I just used the torch switch to control heat for this, so I could do the repair easily with the tiller resting on the ground. I think it's pretty good evidence that you can control TIG heat with just a torch mounted on-off switch pretty darned well. I dial in a little bit of downslope (maybe about 2 seconds) which makes the heat react a little more slowly to the switch, then toggle the switch repeatedly on/off while welding to control the heat. It works quite well.
Attachment 1691

Since I was welding outside in light-moderate winds, I used my "big" #8 gas lens cup and didn't stick the tungsten out very much, and about 12 cfh. Worked well for not fighting the wind too badly. I sapped about 150 psi off Argon bottle doing this though.

[DaveO]

I like your description of using the surface tension to shape the bead- I'll have to keep that in mind.

That machine must have eaten a lot of dirt to taper the leading edges like that! Interesting the way you've rebuilt the taper to a square.

[jakeru]

Yep they sure did wear down a lot. They have scraped through a lot of dirt and rocks, I imagine. The shape I built back is basically what the new replacement blades look like. Here is a picture of some new blades:


I tried the "keep filler rod in freezing puddle to manipulate puddle position" technique on an aluminum welding project the other day. It worked for the first few seconds, but then the heat conducted into the aluminum filler rod and made it uncomfortably hot to hold. (And I do use gloves.) "abort abort!"

[wruehl]

Now that you have the base metal built up I wonder how much benifit there would be to using a good "wear surface" arc rod to put a hardened skin on top. Maybe overkill, but you have gone this far. Nice work by the way. What would replacements have cost? Just curious...

[jakeru]

I think the hard facing would be a very nice touch and make the tines much improved over new ones. Something with tungsten carbide particles in it. Wonder where I can get a small quantity for TIG application? (TIG is generally by far my preference over stick by the way.) I've never done hardfacing before, but this would seem be the perfect project to experiment with it.

I got some more background info on this Merry Tiller from my father, the current owner. Its a 1947 model! It came from his "uncle Chess", who passed away before I was even in the picture. Its now on its second engine. The original engine was a 2HP Briggs and Stratton. What is has now is a little bigger 3HP Briggs, which came from a water pump of some sort. The tiller's frame rails were extended forward by my father (by oxy-acetylene welding on some angle iron extensions) to make more room for the bigger engine, and shift the weight forward.

Its actually on its third set of tines already! The original tines were a crude, "bent steel rod" style. The second set was a bent steel strip style (like the current ones, however was a four-piece set, two pieces on each side.) This current set of tines is the newest style, with one piece on each side, two pieces total. I know replacement tine sets are available, even locally at the equipment rental, where they have a fleet of these tiller (more modern versions but share the same basic parts!) but I can't remember how much they cost at the moment. Replacement individual tines (which are riveted or bolted on) may also be available.

And also the frame has cracked recently near the back by the way, which I repaired using my Everlast TIG. In this high stressed area, I also added a reinforcing piece of steel flat bar onto the angle iron, to turn it into a more strong and rigid "C-channel" shape.

[wruehl]

It was my understanding that wear facing rods work as a function of the flux environment created by the arc consuming the flux itself. I could be wrong but I don't think I've ever seen a wear facing TIG rod. However I have a friend that uses a flux core wire that wear faces and they use it to build up worn continuous miner wheels so they can machine them back to spec (Carbide tooling of course). Those wheels are tough as heck when they are done.

[DaveO]

Turns out Merry Tiller is still around, making tillers for rental fleets: http://merrytillers.com/ Maybe you could contact them and get an endorsement deal!

This is a great story because you're at least the third owner, and you got it from your Dad, who welded on it to make improvements, and now you're welding on it to make improvements.

When I saw your before and after pictures the other day, I was wondering: another option might have been to remove the tapered end of the tine and weld a replacement end on... did you square off the taper with multiple TIG beads for any reason? "Because I could" and "Because it's fun" are both fine answers, and I'm not saying either is better or wrong or right, just curious.

[jakeru]

I did the repair as a build up operation partly because I recently put an on/off trigger on my aftermarket TIG torch, and wanted to try it out on an application requiring pretty precise heat control, such as an extreme build-up like this. So this project was kind of a TIG torch trigger test. The footpedal would have been awkward to use sitting on the ground working on these tines. And it was also of course convenient not to have to remove the tines off the tiller before welding them up on a bench, but rather just attack the tiller at ground level, trying out using the torch switch for heat control.

I also wanted to see how well the TIG torch's inert gas shielding could work for me when welding outside, in a light to moderately windy environment. With the tungsten not sticking out very far and with the larger than usual #8 cup (but not much larger than usual 12 cfh gas flow) , it worked quite well for that.

Material costs were actually pretty low. I probably used about $5-$6 of argon and maybe a buck or two of filler rod. So the main cost was my time, and I can easily justify that when its a learning exercise that I am having fun with. I kind of like the result of the build up better anyway. I like how there is absolutely no material wasted, and no grinding, cutting, or any other metal dust that needs to be swept up.

There was also very little preparation necessary doing the build-up. I have it a hose spray/wash off of the major dirt and wiped off the water around the area to be welded, and a quick wire brush of the tine edges. But mostly I kind of enjoy a challenge like doing a severe build-up like this. And I did get my technique a little bit better for doing it.