New PT...and first snag

Homebrew · May 3, 2008

Hi everyone,
I picked up my new PT-425, w/ grapple bucket, mini-hoe, and brush-hog yesterday. I've been having a ball all morning moving large rocks so I can brush-hog.

I decided to give the brush-hog a try and when I started...I heard: bong! (expecting this as Terry warned you'd hear this when the blades snapped out. 1 or 2 seconds later...bong...1-2 seconds later...bong....

I stopped it...it wasn't cutting by the way. The disc that the blades are mounted on has four bolts...two holding on the blades and two extras in case you snap one of the bolts you can just move the blades to the other two bolts. Anyway, the blades were lodged up over the two extra bolts. I was able to dislodge them, but the are quite wobbly now and obviously something isn't right. Was I supposed to remove the extra bolts before starting? No-one mentioned it. Any ideas?

KentT · May 3, 2008

Homebrew said:
Hi everyone,
I picked up my new PT-425, w/ grapple bucket, mini-hoe, and brush-hog yesterday. I've been having a ball all morning moving large rocks so I can brush-hog.

I decided to give the brush-hog a try and when I started...I heard: bong! (expecting this as Terry warned you'd hear this when the blades snapped out. 1 or 2 seconds later...bong...1-2 seconds later...bong....

I stopped it...it wasn't cutting by the way. The disc that the blades are mounted on has four bolts...two holding on the blades and two extras in case you snap one of the bolts you can just move the blades to the other two bolts. Anyway, the blades were lodged up over the two extra bolts. I was able to dislodge them, but the are quite wobbly now and obviously something isn't right. Was I supposed to remove the extra bolts before starting? No-one mentioned it. Any ideas?

No, don't remove the extra two bolts. As Terry described this "bong" noise is normal and the only way to minimize it is to turn on the PTO at idle or slightly above (if turning it on at idle kills the engine, which it may). Then, slowly move it up to full throttle and get the blades spinning.

Your experience of the blades "jumping over" the other bolt heads is also a common problem. Those bolt heads serve a useful function -- they serve as a "stop" that keeps the blade from wrapping too far back around and over the "stump jumper" hub. What most of us have done is to put longer bolts into those "spare locations" and either put an extra nut under the bolt head so it sticks down farther, preventing the blade from "jumping over it" or to put some kind of a softer, rubber stop such as a chunk of tire rubber or something underneath those spare bolts...

Bottom line is that if you can keep those spare bolt heads down about 1/2 inch further, the blade won't jump over them and lodge the way it did. If you can add some rubber or something softer it will absorb the metal-to-metal "bong" that you heard. However, I've not had a lot of luck so far finding rubber that will stand up to the abuse of rocks, limbs, etc.

Hope this makes sense -- by the way, make sure that the bolts holding the blades on are tight (use LockTite on them), and that the blades are still straight. The blades mount with a bushing on that bolt so that the bolt can be tightened completely and the blades still pivot and swing.

Homebrew · May 3, 2008

Thanks for the reply. Are those bolts threaded normally...i.e. "righty tighty, lefty loosey"? I may add a washer or two.

What I don't understand is how the blades got on the bolts. Once they sling out, centrifugal force would seem to keep them out. Of course, maybe they never got out and the bong I heard was one of them smacking the bolt and the other one banging on the other blade, rebounding and then banging again.

Also, this this is brand spanking new...why the heck should I have to modify it already?!!! I understand things happen...but this seems like a crappy design.

KentT · May 3, 2008

Homebrew said:
Thanks for the reply. Are those bolts threaded normally...i.e. "righty tighty, lefty loosey"? I may add a washer or two.

What I don't understand is how the blades got on the bolts. Once they sling out, centrifugal force would seem to keep them out. Of course, maybe they never got out and the bong I heard was one of them smacking the bolt and the other one banging on the other blade, rebounding and then banging again.

Also, this this is brand spanking new...why the heck should I have to modify it already?!!! I understand things happen...but this seems like a crappy design.

Yes, they're normal threads.

You could use a stack of washers -- IF the bolt is long enough to still engage sufficient threads to hold it in.

How fast was the engine running when you engaged the PTO?

This happens because the hub spins first, quickly, and pulls the blades in against the hub long before centrifugal force swings the heavy blades back out. As I said, the only way to minimize it is to turn on the PTO at low engine RPM so that this effect is as gentle as possible...

Homebrew · May 3, 2008

KentT said:
Yes, they're normal threads.

You could use a stack of washers -- IF the bolt is long enough to still engage sufficient threads to hold it in.

How fast was the engine running when you engaged the PTO?

This happens because the hub spins first, quickly, and pulls the blades in against the hub long before centrifugal force swings the heavy blades back out. As I said, the only way to minimize it is to turn on the PTO at low engine RPM so that this effect is as gentle as possible...

I had the throttle just under about 50% when I engaged...I may try and tighten up those bolts and start slower and see if this helps.

Hmmmm...sitting here thinking about it. There's one thing that bothers me...it appeared that the bolt on the hub hit the sharp side of the blade. I need to go down and see if I can see the scratches and tell for sure...but if the hub spun into the cutting side of the blade, it would appear the hoses are backwards on the cutter motor, right?

KentT · May 3, 2008

Homebrew said:
I need to go down and see if I can see the scratches and tell for sure...but if the hub spun into the cutting side of the blade, it would appear the hoses are backwards on the cutter motor, right?

Yes, if that is the case...

Homebrew · May 3, 2008

Okay...this brush-hog is awesome. I tried to tighten down the loose blade but I couldn't budge the bolt, so I figured I'd just give it another try as is. I slowed the throttle way down before hitting the PTO and voila...works great.
I can't believe how good this thing cuts through small cherry saplings, brush, even a few sandstones!

KentT · May 3, 2008

Homebrew said:
Okay...this brush-hog is awesome. I tried to tighten down the loose blade but I couldn't budge the bolt, so I figured I'd just give it another try as is. I slowed the throttle way down before hitting the PTO and voila...works great.
I can't believe how good this thing cuts through small cherry saplings, brush, even a few sandstones!

Glad that engaging it with the engine slow solved the problem...

We like these mowers -- especially since they're mounted out front where you can watch what you're mowing and can place it more precisely where you want them to go...

MossRoad · May 3, 2008

Homebrew,
As others have stated and you have now found out, we all have had that happen with our brush hogs and we all have had to learn to start it up at as slow a speed as you can, then increase throttle. Welcome to the PT brotherhood.

The blades have a bolt hole through them. Inside that bolt hole is a bushing that the bolt goes throug. The blade has to swing freely, so don't tighten it too much.

The bolts for the blades and the bolts for the stoppers thread into a lock nut on the backside of the hub. I tore mine down a couple times and took lots of pictures. They are on here somewhere. It shows everything inside the hub.