Rear Blade Bent pins

Tvanharp · Mar 11, 2012

I have a 72" Tarter blade on my Kubota L4330. Currently the large pivot pin, about 1 1/2" dia, is bent and I've gone through 3 ,3/4" adjustment pins. Also the adjustment holes have been elongated due to the bending of the adjustment pins. I've ordered a new assembly to replace the damaged parts ($200). I keep catching rocks or a hidden stump in one case that is causing this damage. With the new parts on their way I need to come up with a way to prevent this. Any ideas? Thanks.

2458n · Mar 11, 2012

Slow down.

Tvanharp · Mar 11, 2012

Oh thanks, never thought of that.

BelarusBulldog · Mar 11, 2012

Not familiar with your brand of BB, but could it be that it is too slight for your tractor? You never mentioned what grade it was, so I wonder if that maybe your trouble. For the main 1 1/2" pin to buckle and the holes to be worn oblong, the blade is being pushed over its' limit, somehow!

Tvanharp · Mar 11, 2012

Not sure the grade, it was called heavy duty. Was included with the tractor. The time that it bent the big pin the leading edge (running at an angle) caught a stump sticking up about 2 inches (was under the snow) running at a very low speed but by the time I felt it, it was too late damage was done. Was thinking more along the lines of a sheer pin or some type of release mechanism, springs, something like that....

BelarusBulldog · Mar 11, 2012

If it's classified as HD, then I wonder if there's not a problem with the steel used? It takes a lot of force to bend a 1 1/2" pin and with the blade set at an angle, one would think that it would just move the whole unit (tractor and blade) sideways! Have you complained to the dealer or manufacturer, what do they say?

greg_g · Mar 11, 2012

Here's a photo of a 72" Tartar. Pretty sure I know what you mean by pivot pin, that's what I call the one in the middle that lets the blade index right and left. But what is an "adjustment pin"? Is that what holds the blade at a specific angle? If not, can you point it out on the photo? And are you pushing or pulling when you've bent these pins?

//greg//

Tvanharp · Mar 11, 2012

Yep that's the blade. The pivot pin is the big one with the nut. The adjustment pin is the one used to change the angle.
Was pulling when it happened. Right now I can't swing the blade around because the adjustment plate hits the main support arm as it rotates. You can how the plate is at an angle to the main support this is because that big bolt is bent. The big bolt and adjustment plate is all one welded unit. That is what I'm replacing.

BelarusBulldog · Mar 11, 2012

Wow, that doesn't look good! If you are replacing everything that is bent with new, then this is what I would do to make everything stronger. Everything in blue is your blade now, what I would do to make everything stronger is in yellow and would need to be welded on. Hope this helps. :thumbsup:

rambler · Mar 11, 2012

Really the 2 options are a heavier duty blade built better, or drive slower.

Don't know of any spring/release setups for a back blade.

Something has to give. Either your wheels spin, or something bends. The blade needs to be built heavy enough to handle the shock loads of the speed you are moving.

If it busts up, you are moving too fast for that blade.

--->Paul

Tvanharp · Mar 11, 2012

BelarusBulldog said:
Wow, that doesn't look good! If you are replacing everything that is bent with new, then this is what I would do to make everything stronger. Everything in blue is your blade now, what I would do to make everything stronger is in yellow and would need to be welded on. Hope this helps. :thumbsup:

I'm confused did you intend to include a photo or did I miss something?

Tvanharp · Mar 11, 2012

rambler said:
Really the 2 options are a heavier duty blade built better, or drive slower.

Don't know of any spring/release setups for a back blade.

Something has to give. Either your wheels spin, or something bends. The blade needs to be built heavy enough to handle the shock loads of the speed you are moving.

If it busts up, you are moving too fast for that blade.

--->Paul

Was going pretty slow, probably walking speed or less. But was going down a steep incline. Damage occurred before I could get the clutch in. Brought my L4330 to a pretty sudden stop.
Also the stump I caught was right at the very end of the blade could not have been a worse combination.

Mike476 · Mar 11, 2012

BelarusBulldog said:
Wow, that doesn't look good! If you are replacing everything that is bent with new, then this is what I would do to make everything stronger. Everything in blue is your blade now, what I would do to make everything stronger is in yellow and would need to be welded on. Hope this helps. :thumbsup:

Looking at the photos the lower portion of your blade it is identical to my 72'' MF HD BB. The difference is mine is supported as per the attached drawing, both front and back, and the center pin provides some strength but is there primarily as a pivot to rotate the blade angle. Hard as I try not to I've hit several small stumps around he manure pile with it, sure rattles the teeth but has stood up for the past 10 or so years.

greg_g · Mar 11, 2012

Tvanharp said:
Yep that's the blade. The pivot pin is the big one with the nut. The adjustment pin is the one used to change the angle

Not positive, but it looks like the bolt you're using for a pivot pin is of insufficient diameter. If/when it's permitted to flop around in the pivot hole, it's given extra room to bend. I'm going to guess that it originally came with a hardened pivot pin. Nor can I see if there's elongation of the pivot holes. If yes, it's problematic. You'll just continue to have this problem. If no, you should go back to using a proper hardened pivot pin.

As far as the "adjustment bolts", same thing. They're called index pins, at least I'm guessing that it originally came with pins instead of bolts. Same problem: undersized soft steel bolts move around in the hole, (a) bending the bolt AND (b) tearing the hole. But going back to hardened index pins won't help the tearing problem. Until that's fixed, pins will continue to wear at the holes.

//greg//

Thomas · Mar 11, 2012

Your headed for trouble if you don't get a feel for the work your doing..feel,watch blade also tractor.

SPYDERLK · Mar 11, 2012

Tvanharp said:
Yep that's the blade. The pivot pin is the big one with the nut. The adjustment pin is the one used to change the angle.
Was pulling when it happened. Right now I can't swing the blade around because the adjustment plate hits the main support arm as it rotates. You can how the plate is at an angle to the main support this is because that big bolt is bent. The big bolt and adjustment plate is all one welded unit. That is what I'm replacing.

View attachment 255375

When you fix it, include a big outside diameter steel spacer between the swivel plate and the box section so the spacer will take the load as soon as the pivot flexes. This should make it considerably harder to bend the pivot.
larry

BelarusBulldog · Mar 11, 2012

Tvanharp said:
I'm confused did you intend to include a photo or did I miss something?

If you go back to that post and click on where it says Plow fix.bmp, a picture should open up for you.

Baby Grand · Mar 11, 2012

Wow - you did seem to get the perfect combination of immovable object at the worst possible contact location. I have an almost identiucal 7' BB from King Kutter. It's actually a medium duty blade. Their 7' HD weighs considerably more. I tweeked the lower 3pt pins on mine plowing snow, last Winter. "Oh, that's where the rock is!" I hit it square in the center of the blde, going backwards. Looks like you are using a cot off tire iron for an index pin, or is that what came with the blade?