Bobtach 763 repair

[nobull1]

I was looking at the slack in the tilt cylinder eye and thought I would replace the bushing. Upon closer inspection I found the bosses for the bobtach were worn as well. I had been talking to the machine shop down the road and figured I would take it down when they were slow to get an opinion of what to do. We looked at it and their opinion was they could replace the eye bushing and line bore the bosses and make a couple of step bushings to repair the slack. While we were checking the bosses we also noticed that the lower part of the bobtach was sloppy on one side where it attaches to the arm. When they took it apart it was a mess from previous repair attempts. The hole the bushing went into was beat to death. So we decided to cut off the old bosses and make new step boss/bushing and weld in place. The thought was to make a boss that would take up the side to side slack and be a bushing as well to fix two problems. We purchased the seals that go behind the steel cups and found, after much discussion, that they could just wear and give more lateral slack down the road. The consensus was excavators do not use these seals and work fine. The other thing was there was no recess for the seal to fit in the boss. We decided that we would just leave them out and make a tight fit to the arms then make sure to grease on a regular bases. At present it is tight and works great, time will tell how long it works. The machine shop looks after me and charged me a third of the price of a new bobtach (which would have been needed for the average person)
A few people say there isn't enough material to line bore and install bushings in the bobtach tilt bosses. We bored and installed 1/8" step bushings and appear to be fine. Time will tell how long these repairs last, but they charge reasonable prices to me and we will just fix it if it doesn't last.
Anyone have opinions on this repair....good or bad?

 

[Tazza]

I'm going to do the exact same thing. I have cut the lower pivot points out, machined new bosses and bushings, i'm yet to install them though.
The pivot point for the bobtach ram i'm going to line bore too. I just need to make a jig to do the job. 1/8" bush to take up reduce the size of the hole i see no problems with it.
As for the side to side play, i'm going to make nylon spacers to takeup the the slack, it works well for my 743 that i installed the same spacers in.

 

[nobull1]

I'm going to do the exact same thing. I have cut the lower pivot points out, machined new bosses and bushings, i'm yet to install them though.
The pivot point for the bobtach ram i'm going to line bore too. I just need to make a jig to do the job. 1/8" bush to take up reduce the size of the hole i see no problems with it.
As for the side to side play, i'm going to make nylon spacers to takeup the the slack, it works well for my 743 that i installed the same spacers in.

Why not just make the boss longer to take up the slack?
What do you think about leaving out the seal to avoid future lateral movement?
When we made the bushings for the tilt we counter bored the inside of each boss so the bushing could not work out.
We made the boss and bushing for the lower pins as one and figured "if" it wears, it's almost as easy to cut off the boss and just make a new one instead of just the bushing. The boss is a step bushing and goes into the old hole in the bobtach, then welded in place.

 

[Tazza]

Why not just make the boss longer to take up the slack?
What do you think about leaving out the seal to avoid future lateral movement?
When we made the bushings for the tilt we counter bored the inside of each boss so the bushing could not work out.
We made the boss and bushing for the lower pins as one and figured "if" it wears, it's almost as easy to cut off the boss and just make a new one instead of just the bushing. The boss is a step bushing and goes into the old hole in the bobtach, then welded in place.

The idea was to use nylon so it would wear before the steel did and it allowed me to have a bit of room to play with. I could then take out all the slack rather than an educated guess with a tape measure. Not using the seal i see no problems if you keep the grease up to it, the fresh grease will push out any dirt that gets in to keep it clean, thats my theory anyway.
I honestly don't think the seal would stop any side to side movement anyway, its thin rubber that i can't see it taking any load.
I totally agree that removing the lower boss is simple, if it wears, cut it out and make a new one. I made new 4140 bushings and pins, i need to get them nitrided then it will be super hard. My 743 has the same setup, there is no wear after 3 years of use.

 

[nobull1]

The idea was to use nylon so it would wear before the steel did and it allowed me to have a bit of room to play with. I could then take out all the slack rather than an educated guess with a tape measure. Not using the seal i see no problems if you keep the grease up to it, the fresh grease will push out any dirt that gets in to keep it clean, thats my theory anyway.
I honestly don't think the seal would stop any side to side movement anyway, its thin rubber that i can't see it taking any load.
I totally agree that removing the lower boss is simple, if it wears, cut it out and make a new one. I made new 4140 bushings and pins, i need to get them nitrided then it will be super hard. My 743 has the same setup, there is no wear after 3 years of use.

1045 was the steel of choice for this job with new pins from Bobcat. Time will tell if we should have gone harder. I don't put a lot of hours on in a year (maybe 100) but it is pushing into wood piles and frozen snow/ice.
The seals are about 3/16 of an inch thick on each side. We thought if they wear and break, or whatever, it would allow about 3/8 of lateral play. I would then have to disassemble and install shims. Ask me 6-12 months down the road and I will be able to tell you if 1045 and no seals are a good idea.
If I had my own lathe I might have done what you did. The guy's at the machine shop treat me good and will deal with any issues that might arise, for a reasonable price, if needed. My thoughts now are, it should work for my use for quite awhile. Time will tell. Any pic's of your Bobtach repairs, or have I just missed them?

 

[Tazza]

1045 was the steel of choice for this job with new pins from Bobcat. Time will tell if we should have gone harder. I don't put a lot of hours on in a year (maybe 100) but it is pushing into wood piles and frozen snow/ice.
The seals are about 3/16 of an inch thick on each side. We thought if they wear and break, or whatever, it would allow about 3/8 of lateral play. I would then have to disassemble and install shims. Ask me 6-12 months down the road and I will be able to tell you if 1045 and no seals are a good idea.
If I had my own lathe I might have done what you did. The guy's at the machine shop treat me good and will deal with any issues that might arise, for a reasonable price, if needed. My thoughts now are, it should work for my use for quite awhile. Time will tell. Any pic's of your Bobtach repairs, or have I just missed them?

You don't want to go too hard, i don't know the properties if 1045, I'm sure your machine shop knows what they are doing though. 4140 is pretty good stuff, even when not nitrided. When its treated, it gives it a super hard casing, about .012" thick and tapers off from there.
I haven't put up any pictures yet, i removed the old pivot bosses a few months back, i just haven't gotten around to installing the new ones yet. One of the machines its going in (2 to be done...) is actually dead, and out of reach of the welder. I need to mount the pins, bosses and bobtach in the arms to get them to line up so i can weld them in straight. Its one of those jobs.... It needs to be done, but so much to do before hand.
All i have to show now is 4 new bosses, 6 new pins (2 spare) 8 bushings, 4 to be hardened and 4 to use as a guide to line the boss up in the bobtach. This way the heat will not damage its temper of the final ones that will be used. I just need to work out how to make a jig to line bore the tilt ram pivot point out. I have 2 to do, and i think it would come in handy, no doubt I'll do more over time.

 

[skidsteer.ca]

You don't want to go too hard, i don't know the properties if 1045, I'm sure your machine shop knows what they are doing though. 4140 is pretty good stuff, even when not nitrided. When its treated, it gives it a super hard casing, about .012" thick and tapers off from there.
I haven't put up any pictures yet, i removed the old pivot bosses a few months back, i just haven't gotten around to installing the new ones yet. One of the machines its going in (2 to be done...) is actually dead, and out of reach of the welder. I need to mount the pins, bosses and bobtach in the arms to get them to line up so i can weld them in straight. Its one of those jobs.... It needs to be done, but so much to do before hand.
All i have to show now is 4 new bosses, 6 new pins (2 spare) 8 bushings, 4 to be hardened and 4 to use as a guide to line the boss up in the bobtach. This way the heat will not damage its temper of the final ones that will be used. I just need to work out how to make a jig to line bore the tilt ram pivot point out. I have 2 to do, and i think it would come in handy, no doubt I'll do more over time.

Brian
I think you will be fine without the seals. I never put them back in on my 553 or 853 project. I just bored the centers out of a few flat washers and shimmed the side play out with them. The grease stay inside better then factory imo because the bobtach can only rotate. The side slop allowed dirt to get down on the pin then mix with the grease which I'm sure was worse by far.
The machines with the single tilt cylinder all had problems with eye on the rod end. You likely good for 1000 or more hours again b4 any work will be needed once the slop is gone.
I machined new eyes for mine and welded them to the bobtach. But only used it @ 250 hours when I sold it and it seemed to be holding up fine at that point.
I do think that pin will always wear first on these loaders, heck they wear fist on the loaders with 2 tilt cylinders which have 2 pins the size of yours. It is just a high wear point. I try to grease mine twice a day at that pin if I'm doing alot of gravel spreading or a job that requires fully stroking the tilt cylinders, that pin just rotates too much to last a long time.
Ken