Slasher swing back blades binding up

[greg_g]

You should be able to see from the photo that the bottom plate is now bent, and the dent where the blade has swung back against the end of the shaft.

Yup, a picture is worth a thousand words. Had you posted that photo initially, the issue would have been clear to everyone. Instead of a stump jumper, there's a simple retainer bar. And as you say, it's clearly bent. Should be no problem to remove and straighten in a hydraulic press. What's more important is what caused it to bend in the first place. If you hit something, perhaps it will never happen again. But if the steel is simply too soft, it's a manufacturing/engineering problem - and you can expect recurrence. I think the test will be how easy or hard the steel resists the hydraulic press.

//greg//

 

[gwdixon]

Yup, a picture is worth a thousand words. Had you posted that photo initially, the issue would have been clear to everyone. Instead of a stump jumper, there's a simple retainer bar. And as you say, it's clearly bent. Should be no problem to remove and straighten in a hydraulic press. What's more important is what caused it to bend in the first place. If you hit something, perhaps it will never happen again. But if the steel is simply too soft, it's a manufacturing/engineering problem - and you can expect recurrence. I think the test will be how easy or hard the steel resists the hydraulic press.

//greg//

The OP knows what caused, or is causing, the bend. The blades are swing back and getting stuck in the gap. The blade is acting as a lever.

Obviously, the blades have a bend in them that wedges into the gap (a photo of the blades would be informative).

The malfunction occurs when the PTO is engaged from stop and the blades don't rotate quickly to become extended. Not sure if the tractor has a way to gently engage the PTO and slowly bring it up to speed.

The mower is new and the problem has been observed from the beginning so it is not likely that something else bent the bar.

The solution is to determine how to stop the blade from sticking / entering the gap.

Parakleta can correct this observation if needed.

 

[Parakleta]

You can just make out in the photo the point where the blade is striking the weld, there is a slightly shiny spot about half way along the piece of the blade you can see in the photo. The blade has ever so slightly rounded corners.

The tractor is a MF GC2400 and I couldn't find any way to slowly engage the PTO, it seems to be on or off.

The manufacturer claimed that the bar was likely bent in transit and sent someone out this afternoon to fit a replacement bar. Engaging the PTO about 20 or so times since the new bar has been installed shows no sign of any damage to the new bar.

One specific difference this time from the previous is that I had started to adjust the clutch and so it now slips just a little on engagement and that may be enough to protect the plate from taking the full force of the swingback. I think it's a case of once the plate is damaged a little it's stuffed. The old plate actually had bits chewed out of it where the blade had swung back against it. It may also be the case that the previous one was softer or weaker than the new one.

I still don't like the design, but the problem seems to be fixed at least for now. I am tempted to get some kind of ablative or absorptive material to install between the plates, either timber or high density rubber (like the stuff that protects sledge hammer shafts from mis-strikes), to at least protect the weld at the bottom of the shaft (since this still takes the full force of the startup blow).

The unit is brand new and it's just starting summer so there's a few months of hard work ahead of it, so at least hopefully any problems will present themselves within the warranty period.

Thanks for everyones time.

 

[teg]

To engage my mower, I slow the RPM's to about half, my pto is either on or off but I still push the clutch in when I turn the PTO on, then ever so slowly let out the clutch... once it's up and running at half RPM's, I increase the RPM to reach the mark for 540 rmps.

It should be a slow engagement... and that's not just for the mower. The tractor itself is getting a shock load, too. Is the tractor new also? You mentioned adjusting the clutch... maybe it needs it more...

 

[Parakleta]

I slow the RPM's to about half, which is the lowest setting on the throttle. The tractor's transmission however is entirely hydrostatic and there is no clutch pedal. The PTO engagement lever doesn't seem to have a friction point that I can find, only on or off. The clutch I have been adjusting is the slip clutch on the slasher itself.

Is it possible that the sudden engagement of the PTO is some setting on the tractor that is not properly calibrated?

 

[teg]

Is it possible that the sudden engagement of the PTO is some setting on the tractor that is not properly calibrated?

Have no idea about that tractor so you might have a better chance of getting it answered over in the MF forum in a new thread....

 

[greg_g]

Sounds like you have an electric PTO clutch. I've got one on my John Deere. On those, there's no in-between. It's instant-on/instant off. But I think once you get that lower bar replaced, the problem should revert to how I described earlier; switch PTO on at low RPMs, put up with a little vibration while the two blades balance each other out, increase the RPMs, go to work. But quite honestly, it looks like a design that wasn't thought all the way through. Given that it's almost new, perhaps you could get the dealer to take it back in favor of one that's engineered a bit more sensibly.

//greg//

 

[Jerry/MT]

I've just taken delivery of a new MF GC2400 with a 4in1 FEL and 4' slasher and I'm having some trouble with the slasher.

I was trying to adjust the slip clutch on the slasher but every time I engage the PTO one blade swings back and jams folded up. The vibration at this point is fairly severe and I shut down the tractor. I have to use a 3lb hammer to free the blade. I am engaging the PTO at minimum engine throttle.

The blade assembly is two parallel plates with two blades bolted between them, one at each end, and the top plate has the vertical shaft through it and welded. It appears the blade is riding up the weld and wedging between it and the lower plate. The lower plate is now bent and the weld is damaged. Both blades have done this.

I don't know if there is something misadjusted, or if I am doing something wrong, or if this is just an issue of faulty manufacturing or poor design. Anyone have any suggestions?

You aren't doing anything wrong. That's kind of a strange mounting system-parallel discc with the blades in between the disks! That design is asking for problems. My mower has a single "stump jumper disk with the blade bolted to the rim. The blades have an offset that keeps them away from the stump jumper.
I have an independent pto and when I stop the pto, the brake stops the shaft and the blades "fold" under the stump jumper from their inertia. When I start up, the mower jumps due to the torque reaction as the blades "unfold". Perfectly normal.

I'd take the "slasher" back to the dealer and get a different design. As rough a usage as these devices are exposed to, you need one with a better design.

 

[Glen Watkins]

Another vote to junk that thing! Take it back to the dealer! What brand name is it so others know to steer clear of them?

 

[Hollow]

The bottom plate is bent allowing the blade enough room between the plate and the hub to get wedged in there. You could take the plate off and flip it over to close the gap between it and the hub and that should take care of the problem. But if its new equipment I'd just take it back to the dealer and let them worry with it.