A while ago there was a thread about helping out your neighbors. I couldn't find the thread, but here's my contribution.
My one and only neighbor came by early this week with this thing:
It's called a "wobble arm" and mounts in a mower conditioner, a machine that mows hay and looks something like this:
Inside the two upper bores of the wobble arm an eccentric bearing turns, imparting reciprocating motion to the end of the arm. The reciprocating motion is transferred to the sickle bar, which cuts the hay.
Unfortunately, all that reciprocating motion takes it's toll on bearings and the arm itself. This one had a previous weld repair, a few fatigue cracks in the arm and a bearing bore that looked like this from a seized bearing hammering around:
As you can see, it has been repaired once before. This particular part is not available on short lead time from the manufacturer. It costs an arm and a leg. So, I was asked if I could fix it.
The original arm was obviously shot and the metal fatigued beyond use. However, the wobble box (U-shaped bracket) looked OK, so I decided to re-use it. A trip down to the steel supply netted a few feet of 3/4" by 3" flat.
I transferred the critical dimensions to a cut-to-length section, then drilled and tapped the bearing cap mounting holes.
Then, I chucked the section into the lathe to bore the hole, as my mill is currently out of service.
With the center section of the arm done, I cut the wobble box off the old arm. To keep the bored holes in alignment, I welded some 1/8" flat onto both sides of the U-shaped section to prevent it springing out when I cut the welds:
Part way there:
Next, I removed the hardened bushing from the old arm. I didn't have a piece of tool steel the appropriate size to make a new one. Heat was required to remove it:
With the bushing out, I was able to mock up the offset arm. I originally wanted to hot bend the entire piece, but my neighbor was certain it had to be welded to obtain the necessary offset. Apparently, there is a bracket to clear.
I found the center of the bushing bore with the tailstock, as location needs to be "close", but not precise:
I drilled the hole and bored it to size to fit the old bushing:
To align the wobble box to the pivot bearing bore I used a couple of washers and the bearing cap bolt holes. I set the outside of the washers to the inner width of the U bracket -.005", -bearing bore / 2 to center the U bracket on the bearing bore.
Finally, I welded everything up:
So far, so good. He's happy with the repair and back in the field.
My one and only neighbor came by early this week with this thing:
It's called a "wobble arm" and mounts in a mower conditioner, a machine that mows hay and looks something like this:
Inside the two upper bores of the wobble arm an eccentric bearing turns, imparting reciprocating motion to the end of the arm. The reciprocating motion is transferred to the sickle bar, which cuts the hay.
Unfortunately, all that reciprocating motion takes it's toll on bearings and the arm itself. This one had a previous weld repair, a few fatigue cracks in the arm and a bearing bore that looked like this from a seized bearing hammering around:
As you can see, it has been repaired once before. This particular part is not available on short lead time from the manufacturer. It costs an arm and a leg. So, I was asked if I could fix it.
The original arm was obviously shot and the metal fatigued beyond use. However, the wobble box (U-shaped bracket) looked OK, so I decided to re-use it. A trip down to the steel supply netted a few feet of 3/4" by 3" flat.
I transferred the critical dimensions to a cut-to-length section, then drilled and tapped the bearing cap mounting holes.
Then, I chucked the section into the lathe to bore the hole, as my mill is currently out of service.
With the center section of the arm done, I cut the wobble box off the old arm. To keep the bored holes in alignment, I welded some 1/8" flat onto both sides of the U-shaped section to prevent it springing out when I cut the welds:
Part way there:
Next, I removed the hardened bushing from the old arm. I didn't have a piece of tool steel the appropriate size to make a new one. Heat was required to remove it:
With the bushing out, I was able to mock up the offset arm. I originally wanted to hot bend the entire piece, but my neighbor was certain it had to be welded to obtain the necessary offset. Apparently, there is a bracket to clear.
I found the center of the bushing bore with the tailstock, as location needs to be "close", but not precise:
I drilled the hole and bored it to size to fit the old bushing:
To align the wobble box to the pivot bearing bore I used a couple of washers and the bearing cap bolt holes. I set the outside of the washers to the inner width of the U bracket -.005", -bearing bore / 2 to center the U bracket on the bearing bore.
Finally, I welded everything up:
So far, so good. He's happy with the repair and back in the field.
