Grading BX25 / RCK54P23BX center blade fell off !

[Jeff H]

I had a blade fall off yesterday while mowing.

Normally if getting off the tractor while mowing I would throttle down and then disengage the PTO. Well this time I just got off with the RPM's up and the PTO engaged without thinking to move something out of the way. It was a good test of the safety switch system, it worked as it should and the tractor came to a complete abrupt stop.

No problem, started it up and went on my way. Coming around on the next pass and what do I see? A lawnmower blade laying on the ground. Right next to it is the bolt and washer. Stopped the tractor and turned it off safely this time and looked underneath and sure enough the center blade fell off. My theory is that when everything comes to a complete stop so fast when the safety switch stopped the tractor that centrifugal force caused the blade to spin itself right off.

Well I got out my new Larry's Mower Axles that I haven't used yet, and removed the deck. No damage under the deck, luckily the falling blade didn't interact with the other two blades. But now I realized there is supposed to be a conical sheet metal dust cover over the spindle before the blade goes on. Went to the back yard and hunted that down, unfortunately it was destroyed. One of the blades caught and launched it.

So I did a nice end of the season cleanup of the deck, a few weeks earlier than I was planning on. The Kubota dealership was closed I so couldn't get the dust cover and get it back together.

I was amazed at how overall clean the deck was underneath when I took it off. I bought the tractor new in May this year. I guess the deck might be powdercoated? No other prep was applied under the deck, I took it out of the crate, attached it and cut the grass all summer. I have Fluid Film now, I will coat it with that. The Larry's Axles worked great, I was blasting it with the pressure washer and it didn't move.

So the lesson here is if you mistakenly let the safety switch bring the tractor to a halt, make sure to check the tractor over before restarting it!

 

[Deano]

Glad no one got hurt and that you found all your parts!!

Deano

 

[Jeff H]

Thanks Deano
Yes it could have been allot worse. Here is the damaged dust cover next to one of the other two.

Speaking of these dust covers, I can't say I am thrilled with the design of them. When I took the other two off they were both packed solid with wet grass. Thats not good. They might be protecting the aluminum outer spindles from bumps and bruises but the wet grass is promoting aluminum corrosion. They are steel with a gold anodize finish and they are rusting on the inside. Thay have a drain hole in the bottom to let water out, but I assume the grass is coming in over the top and it is not getting back out.

 

[TripleR]

Had you had your blades off previously and if so, what did you torque them at?

 

[Jeff H]

No I picked up the mower in the crate at the dealer in June, brought it home and mounted it. I only checked the gearbox fluid level (which was low) at the time.

When I took the other two blades off just now they were quite sufficiently tight. I used a 1/2' breaker bar.

 

[TripleR]

That sure is a puzzlement. Even if it was loose, it should have just rotated on the shaft as the nut is separated by the cupped washers and the nut seems too small to have any real inertia.

 

[Jeff H]

That sure is a puzzlement. Even if it was loose, it should have just rotated on the shaft as the nut is separated by the cupped washers and the nut seems too small to have any real inertia.

This deck uses a bolt and a washer, not a nut. I still think the quick stop broke that bolt loose and being a nice clean new thread the downward weight of the rapidly spinning blade just spun it right out.

 

[thavil]

Speaking of these dust covers, I can't say I am thrilled with the design of them. When I took the other two off they were both packed solid with wet grass. Thats not good. They might be protecting the aluminum outer spindles from bumps and bruises but the wet grass is promoting aluminum corrosion. They are steel with a gold anodize finish and they are rusting on the inside. Thay have a drain hole in the bottom to let water out, but I assume the grass is coming in over the top and it is not getting back out.

Jeff - One way to keep the cups from getting packed with grass and rusting on the inside is to pump them full of grease. There have been a few threads on this subject and this is what I do now. It may take 40 or more pumps on each of the three spindle zerks to fill them up. With the deck on the mower stands, pump each zerk until you see some grease come out of the drain hole.

 

[ChuckinNH]

I have had the same thing happen with my Simplicity mmm. It followed hitting a buried piece of log pretty hard. Nothing happened right then, and things sounded OK, but very soon after that a blade fell off. In my case there was a different cause for the sudden blade stoppage, but the results were the same. Mine did no damage to the deck, or other blades either, but it did beat up the bushing the blade is mounted on. Better that than a broken spindle for sure!

 

[Jeff H]

Hmmm, pack them full of grease. I could just hand pack them when I put it back together no need for all of that pumping. I guess its better than full of wet grass.

Has anyone just left them off? What is the downside to that?