Rotary Cutter, No Shear Protection.....

[Stef]

Lidger, could you take a picture of the other end of the shaft? IMHO, the end you pictured go on the tractor side.

 

[Fjord]

Isn't the shaft that comes out of the gearbox of the cutter supposed to be smooth? My buddies shaft is smooth with a hole for the shear pin. Doesn't the splines defeat the purpose of the shear pin feature?

Mine has a smooth input shaft as well.If you look in that catalogue that MrJimi posted under Agricultural Supplies & Equipment you will see that the gearboxes listed with the Kingcutter rotary mowers can be ordered with either smooth or splined input shaft(even though all the pictures show the same splined one).That picture of the red gearbox that was posted looks like it was for a rear finishing mower where the gearbox drives multiple blades via some belts. Maybe in that case they don't bother with shearpins because the belts can slip or break if jammed. Back to your original question I'm pretty sure you will want some kind of shear pin protection to avoid breaking something more expensive.You can probably get a PTO shaft with shearpin like the one I described on my snowblower but it would be an experiment to find out what the correct size and grade of bolt would be.Hopefully somebody else will chime in with a more definite answer for you .Good Luck & Have Fun

 

[Lidger]

Thanks for everyones help thus far. I will do some more work as soon as it stops snowing. I picked up this rotary cutter right before it started snowing badly.
But yes, my input shaft on my gearbox is splined like the one pictured. That is my concern. If an input shaft is splined on a rotary cutter, then how is a shear pin going to do anything, unless of course a hard impact breaks every tooth on the spline as well as the bolt.
I will dig into this deeper and update all of you as soon as I can.

Thanks again everybody!!

Lidge

 

[pdowling1]

If this you have a RFM with multiple belt driven spindles, rest easy, the belts will give you all the protection you need. Look at any MMM, there is no shearpin on them! The shearpin is needed only if the mower has a spindle driven directly by the gearbox, as most single spindle 3PH mowers are.

 

[jimainiac]

Maybe you need a "slip clutch". We have a 5' rotary cutter that has a smooth input shaft on the gearbox and a shear pin. We also have a heavier duty 6' cutter with a slip clutch. That one's gear box input shaft is splined. The shear pin and the slip clutch serve the same purpose, but with the slip clutch you don't have the downtime of replacing the shear pin in the middle of mowing.

 

[JerryG]

What has happened is that the previous owner has removed the slip clutch. You can buy them with either a 6 spline or a smooth bore. What you need to do is go buy a slip clutch and install it. You may have to cut the PTO shaft unless it is the original shaft.

 

[Podunkadunk]

Lidger,
My bushhog (rotary cutter) has the same identical hookup to the PTO shaft as yours (as your first picture). It is on correctly.


Podunk

ps. around these parts, we call all "rotary cutters" bushhogs.

 

[Lidger]

Hi all!!

Thanks for all of your input! I realize now I guess this is the way it is supposed to be. I am really worried about damaging my tractor though. It was mentioned that I should try a "slip clutch".
I went to my local TSC store and found them ($99). I also saw somthing called an "over run" clutch. the "over run" clutch was $39. I was told that these two things are similar. Would an "over run" clutch provide some protection to my tractor and bush hog gearbox?
What is the difference between the two?

P.S. This forum has been so helpfull I cannot even begin to explain. Everyone has been so kind with all of the suggestions.
and again, thanks in advance for your help!

Lidge

 

[pdowling1]

An overrunning clutch is a whole different critter! It allows the blades to continue spinning when you disengage the clutch, without turning the PTO shaft. What can happen without it, on older tractors without live PTO, is that the energy from the spinning blades, acting as a flywheel, can drive the tractor forward, even after you depress the clutch pedal. This is a VERY BAD thing, as you can imagine.
The overrunning clutch does NOT protect your drive line from shock damage if you hit something with the blades. A slip clutch would give that type of protection, as it can slip under excess load. The problem is that they tend to rust up and not slip when you need them to!

 

[Lidger]

So if I can get a new 40hp gearbox with a smooth input shaft with shear pin protection for $140. Should I just wait until my current gearbox without shearpin protection goes kaput? A slip clutch is $100 and not really "guaranteed " to work.
Is there a chance that my tractor will be damaged before the bush hog gearbox? This is what I am most concerned about.

BTW: my tractor is an '01 Kubota L3010 HST

Lidge