Bush Hog BH25 yokes breaking

[Boatman62]

Just some more info to quell any speculation of the top flex link issues.

After installation I backed the cutter up an embankment and it rose up to about a 35-40° angle with the tractor. No problem with the link doing what it should do and it could probably go another 15° before the linkage would start to bind.

What I did notice was the difference in bends between the new and old arms. The old arms have been straightened out. This leads me to believe tension is the factor here. In raising the 3 point if you just pull the lever up it's a pretty violent action and the cutter actually bounces a couple times. He agreed that he needs to be smoother in raising it.

Soooo... he also changed his mind about going to chains. If we have to replace another, it will be chains.

 

[wirlybird]

Good info.
I'd say a combination of the weight of this BH and the jerky lifting and the bends being more towards the middle of the yoke straps I could pretty easily see how there is a lot of force on those bends and the weight trying to straighten them eventually causing them to fail. It's a really weak point the way those are.
Even though the part number appears to be ok I'd be willing to bet something is up with those parts. Either they are an aftermarket part or it's a bad redesign. Maybe they are from a more light weight series and they are a substitute part for his series?

Anyway, sounds like you may be onto something.

 

[Boatman62]

Good info.
I'd say a combination of the weight of this BH and the jerky lifting and the bends being more towards the middle of the yoke straps I could pretty easily see how there is a lot of force on those bends and the weight trying to straighten them eventually causing them to fail. It's a really weak point the way those are.
Even though the part number appears to be ok I'd be willing to bet something is up with those parts. Either they are an aftermarket part or it's a bad redesign. Maybe they are from a more light weight series and they are a substitute part for his series?

Anyway, sounds like you may be onto something.

The bars were shipped directly from Bush Hog so not an aftermarket part. I suspect they decided to go with a running change and this part with a little modification fits some modern machine also. Less part numbers and warehouse space needed.

 

[wirlybird]

The bars were shipped directly from Bush Hog so not an aftermarket part. I suspect they decided to go with a running change and this part with a little modification fits some modern machine also. Less part numbers and warehouse space needed.

Very well could be.
You might try to find a machine shop and see the cost to make a set more like the originals.
Might be worth a try if not too costly!

 

[ptsg]

It's very surprising to me to see that the manufacturers still go with the bars instead of just a piece of chain, considering they're always looking for the cheapest way of doing something possible. The chains would fit pretty much any mower, is cheap for the manufacturer and for the end user and they wouldn't even need to redesign that part of the mower on new units or change to a new part number.

Is there really any point for the bars to still being used? Am I missing something really obvious?

 

[LD1]

Sounds like you got it fixed....and a good solution (chains) if these bars fail again.

Im not there....But I too would swear that the flex link was torch cut. Water under the bridge now though

 

[RickB]

It's very surprising to me to see that the manufacturers still go with the bars instead of just a piece of chain, considering they're always looking for the cheapest way of doing something possible. The chains would fit pretty much any mower, is cheap for the manufacturer and for the end user and they wouldn't even need to redesign that part of the mower on new units or change to a new part number.

Is there really any point for the bars to still being used? Am I missing something really obvious?

Many moons ago I bought a well used BH Squealer 72, the old square back design. It used a single chain between the hitch A frame and tailwheel beam mount. Used the darn thing for a decade and sold it for $200 more than I paid. Never broke the chain, either.
I'd have had those bars and flex link from that BH25 in the scrap pile long before now.
Then again I've had pilots for customers too.

 

[wirlybird]

I think one thing to keep in mind now that you may have a cause for the breaks … possibly operator assisted! Let's assume this is the main cause for the sake of argument.
Don't try to "beef" up the yokes to better handle the rough treatment and reduce them breaking.
Doing so would likely just lead to a break or bending somewhere else that may have a worse or more dangerous result on the overall unit.
Don't modify the implement but modify the operation of the implement.

I still think the yokes are a weak link due to the placement of the bend.

Anyway just my thoughts. Hope things improve with it!

 

[LD1]

I think one thing to keep in mind now that you may have a cause for the breaks … possibly operator assisted! Let's assume this is the main cause for the sake of argument.
Don't try to "beef" up the yokes to better handle the rough treatment and reduce them breaking.
Doing so would likely just lead to a break or bending somewhere else that may have a worse or more dangerous result on the overall unit.
Don't modify the implement but modify the operation of the implement.

I still think the yokes are a weak link due to the placement of the bend.

Anyway just my thoughts. Hope things improve with it!

Its obvious the yokes are the weak link. But the fact that they are bent should NOT effect its operation.

Look at all the other bent metal on that cutter. The flex link, the A-frame, etc. Those havent broke.

IMO, it looks like he is operating it as it should, and I wouldnt suggest modifying operation. Rather I'd modify the material used. I think this is an engineering oversight. They spec'd the material size.....and all was well. Then somewhere along the line some purchaser got a better deal on cold rolled steel but didnt run it by engineering. And the people working in a production shop, which are NOT fabricators or have an understanding of metals....rather they are machine operators and button pushers....just did what they always did.

Bending cold rolled steel bars without heat is a guaranteed crack. Take a bar 2" x 1/4" bar and give it a nice radius for the bend....try and bend it 90 degrees and I bet you wont get to 45 before you have two pieces of metal. Cold rolled steel is work hardened by the forming process and had very little ductility.

Go to chains or hot rolled bars and never worry about it again

 

[JWR]

Here is something to possibly look at. See the wear spot indicated by the arrow.
Could it be that the leading edge of the black bars are moving forward in the slot on the red part and binding at the front were the arrow points and not allowing the red part to pivot up?
I think I would get the tractor and cutter on to solid level ground with the 3-point lowered all the way as if cutting and then place a jack under the tail wheel boom and start to jack it up and see how the whole assembly works and pivots. See how far the rear wheel will go up before it runs out of travel and see if the bars start to bend outward.

Great idea wirlybird. Tests are 100x better than speculation and eyeballing. I still wager it will show that the "hard compression" (lack of buckling upward of the flex link) does not happen. By the way, the thing missing from such a test is forward force on the bush hog (as would occur if you back into a tree.) The combo of that force plus raising the back of the hog is the real worst case.