keep breaking shear bolt

Bubbas Boys · #1 08/23/14, 02:34 PM

I have been runnin our new to us Massey baler this summer. It has broken the shear bolt from PTO shaft to the baler 3 times. Today I started up my new to me old bush hog mower and I broke that one to. Is there something I am doing that would cause this. Should I not have RPM up when I engage the PTO? Should I not be moving when I engage the PTO? I am pulling them with a 1955 Farmall 300. Thanks for any help!

Darren · #2 08/23/14, 02:47 PM

I generally engage at a lower RPM and then increase it. I also always engage the PTO only when stopped. You can always install a slip clutch on the drive line and eliminate the shear pin. You probably already know not to use a higher strength bolt to replace the broken shear pins.

mulemom · #3 08/23/14, 02:51 PM

My dad was always adamant that you started the pto at a low rpm and eased the pto into gear then brought the rpms up. Also that you never stop the baler full of hay-stop the tractor then when it clears shut it off so there's less resistance when you start back up. Rpms on startup were just high enough to not stall the tractor.

unregistered41671 · #4 08/23/14, 02:51 PM

I engage the PTO at a little above idle, then after everything is running, ease up on the throttle till I get the speed I want.

agmantoo · #5 08/23/14, 04:42 PM

Bubbas Boys, are you bringing the PTO speed up to 540 Rpm and keeping it there when baling? The big pulley acts as flywheel and if you are not keeping the PTO speed up when baling that will also shear the bolt. The bolt must also be snug in the mounting holes and with no side play.

jwal10 · #6 08/23/14, 07:19 PM

Many shear pins are in an insert that gets worn, this puts pressure on a new pin, trying to shear it off. Check for a worn insert. Always use the shear pins from manufacturer, they are made just for the equipment. May cost more up front but cheaper in the long run....James

Bubbas Boys · #7 08/23/14, 08:46 PM

Thanks everyone for the advise ( great as always). I figured that when I was stopping the baler too often and starting it back up a full throttle and moving that it was a bad idea. I should know better. I can admit that old school equipment is new to me. haha. When I broke one today on the mower for the first time using it I figured it was me. Thanks a lot!!

idigbeets · #8 08/24/14, 05:43 AM

If its full of hay, of you're going too fast, too much hay coming into the head, or it's mounded funny from a poor rake job all will jam it up and shear a bolt.

Starting at high RPM will do it too. I always start from under 1000rpm on my tach... then throttle up to where I wanna be.