B7100 - broke both sway linkages

[AOW162435]

I keep my '79 B7100 on some property we own that's about 3-1/2 hours from home. Yesterday I made the drive out in order to do another round of mowing. About an hour into it, I feel the tractor shift as I'm mowing on a pretty good slope. Much to my surprise, I see that both sway control linkages sheared at the inboard attachment points. The factory welds look like they simply failed. One probably went, and then the other in short order.

I'm running a new 59" Caroni rear discharge finish mower that weighs 400+ lbs. The first time I used the setup was a month ago, where I ran it continually for about 5 hours.

I have a nagging suspicion that I am to blame - when I first set the mower up in my garage, I spent some time ensuring it was centered, but I also know that I made the sway linkages fairly snug. Is it true that these will get overly stressed when fully lifting the 3-point hitch (if too tight)?

I had to abandon the mower deck on the property and drive the tractor half a mile back to where I store it. Before leaving to drive home, I removed the entire 3-point hitch assembly and took it with me. If time allows tomorrow, I will prep the failed parts and re-weld.

I've attached a random B-series pic showing where the breaks occurred, as well as a pic of my mower setup.

Andreas

 

[Edke6bnl]

I found mine ready to give way, I removed them and machined new pieces with a better fit. B7800 tractor

 

[jaxs]

There just isn't enough space for cat 1 implements between wheels on tractor showing break points.

 

[AOW162435]

I found mine ready to give way, I removed them and machined new pieces with a better fit. B7800 tractor

Any pics showing your solution?

Andreas

 

[SDT]

Yes. You need to check/adjust at maximum lift.

Also need to avoid swinging mower into obstacles when turning and not exceed recommended weight limitations for implements.

 

[AOW162435]

There just isn't enough space for cat 1 implements between wheels on tractor showing break points.

I don't understand what you wrote.

My father bought a B7100 new in 1980 and ran it with a 5' Kubota rear finish mower for 20 years. We used it for lawn areas around the house, mowing acres of our tree farm, and for keeping acres of woods clean.
Never had a failure like this, so I suspect I adjusted the linkages too snug.

Andreas

 

[NorthwoodsLife]

Linkage should be loose. But not loose enough to hit inside edge of tires.

Reminds me of a motorcycle I sold to a guy. Saw him a few weeks later and he showed me all the stuff he did to the bike. He said, "The chain was way too loose when you sold it to me". (It wasn't, I'm a motorcycle guy.) I checked the chain after he "fixed it", and he had it tight like a rubber band!!! And he was a mechanical engineer! I told him, read about, and fix it. You'll break the chain, the transmission case, or your output shaft. The swing arm moves in an arc. It gets longer when the arc is zero degrees.

On a tractor 3 point, it needs some play, otherwise you'll stress the linkage too often. if it's tight, you'll stress the linkage all the time.

 

[North Idaho Wolfman]

Yea they need to have a little play in them to make up for variation during shifts and lifts.

 

[AOW162435]

Thank you for all the responses. In reviewing the pic I posted (grabbed from Google Images), it appears as if that tractor has wider attachment points (where mine failed). Did Kubota revise these at some point in the production run of the B7100 tractors?

Andreas

 

[hodge]

It may be true. I also had a B7100, but mine was a newer tractor- the stabilizers attached at a common pivot plate underneath the PTO shaft. So, there may be some geometry differences. Anyway, I found that if I adjusted my turnbuckles to the point that there was just a little bit of sway when the implement was on the ground, they would be banjo tight when I raised the implement all the way up. So, at least in that once case, geometry changes, as the arms would rise, created a difference in length between the two points of mount. It could also be as simple as the lift arms rotate some when lift is implied on them. Regardless of why, I've come to the conclusion (from that ownership experience, and having built 4500+ sets of telescoping stabilizers, and seeing many customers who have stretched and broken their factory stabilizers) that stabilizers are intended to stabilizer an implement, not immobilize it. There should be a slight amount of play left in the lift arms, once the stabilizers are adjusted- I typically look for half an inch or so of side to side play, which is more than enough to keep the implement in place, without damaging components.
AOW, in your case, I would guess that years of fatigue was the culprit, versus a one time event. In any case, those ears can be found used, and I build new ones for customers, if needed.

Edit- something else that I didn't think about initially- the more parallel a stabilizer is to the lift arm, the more leverage that is imposed on it. On a B7100 with the two separate ears, the stabilizers are attached closer to the mount ends of the lift arms, versus the common plate under the PTO shaft. In other words, the later version has the stabilizers at more of an angle to the lift arms, versus more parallel. Therefore, on the early version with the ears, there is more leverage imposed on the stabilizers when side loads are applied- therefore they are easier to damage. So, part of the issue is the design.

 

[fried1765]

It may be true. I also had a B7100, but mine was a newer tractor- the stabilizers attached at a common pivot plate underneath the PTO shaft. So, there may be some geometry differences. Anyway, I found that if I adjusted my turnbuckles to the point that there was just a little bit of sway when the implement was on the ground, they would be banjo tight when I raised the implement all the way up. So, at least in that once case, geometry changes, as the arms would rise, created a difference in length between the two points of mount. It could also be as simple as the lift arms rotate some when lift is implied on them. Regardless of why, I've come to the conclusion (from that ownership experience, and having built 4500+ sets of telescoping stabilizers, and seeing many customers who have stretched and broken their factory stabilizers) that stabilizers are intended to stabilizer an implement, not immobilize it. There should be a slight amount of play left in the lift arms, once the stabilizers are adjusted- I typically look for half an inch or so of side to side play, which is more than enough to keep the implement in place, without damaging components.
AOW, in your case, I would guess that years of fatigue was the culprit, versus a one time event. In any case, those ears can be found used, and I build new ones for customers, if needed.

Edit- something else that I didn't think about initially- the more parallel a stabilizer is to the lift arm, the more leverage that is imposed on it. On a B7100 with the two separate ears, the stabilizers are attached closer to the mount ends of the lift arms, versus the common plate under the PTO shaft. In other words, the later version has the stabilizers at more of an angle to the lift arms, versus more parallel. Therefore, on the early version with the ears, there is more leverage imposed on the stabilizers when side loads are applied- therefore they are easier to damage. So, part of the issue is the design.

Nice write up!
Thank you!
I do not have a B7100, but your info is appreciated by ALL of us!

 

[AOW162435]

It may be true. I also had a B7100, but mine was a newer tractor- the stabilizers attached at a common pivot plate underneath the PTO shaft. So, there may be some geometry differences. Anyway, I found that if I adjusted my turnbuckles to the point that there was just a little bit of sway when the implement was on the ground, they would be banjo tight when I raised the implement all the way up. So, at least in that once case, geometry changes, as the arms would rise, created a difference in length between the two points of mount. It could also be as simple as the lift arms rotate some when lift is implied on them. Regardless of why, I've come to the conclusion (from that ownership experience, and having built 4500+ sets of telescoping stabilizers, and seeing many customers who have stretched and broken their factory stabilizers) that stabilizers are intended to stabilizer an implement, not immobilize it. There should be a slight amount of play left in the lift arms, once the stabilizers are adjusted- I typically look for half an inch or so of side to side play, which is more than enough to keep the implement in place, without damaging components.
AOW, in your case, I would guess that years of fatigue was the culprit, versus a one time event. In any case, those ears can be found used, and I build new ones for customers, if needed.

Edit- something else that I didn't think about initially- the more parallel a stabilizer is to the lift arm, the more leverage that is imposed on it. On a B7100 with the two separate ears, the stabilizers are attached closer to the mount ends of the lift arms, versus the common plate under the PTO shaft. In other words, the later version has the stabilizers at more of an angle to the lift arms, versus more parallel. Therefore, on the early version with the ears, there is more leverage imposed on the stabilizers when side loads are applied- therefore they are easier to damage. So, part of the issue is the design.

Hodge,
Thank you so much for the thorough reply. Due to time constraints, I will need to re-weld the broken joints when I get home sometime Friday, and then re-install on Saturday. Hopefully the repairs hold for a few hours of mowing.

That said, I'd be interested in a new set from you and will reach out.


Andreas

 

[hodge]

Hodge,
Thank you so much for the thorough reply. Due to time constraints, I will need to re-weld the broken joints when I get home sometime Friday, and then re-install on Saturday. Hopefully the repairs hold for a few hours of mowing.

That said, I'd be interested in a new set from you and will reach out.


Andreas

Private message me, or email me through my website- www.stabilworks.rocks