Mowing 48" Finish Mower Blade challenge

[Jiminy]

I purchased my PT used. 422 with about 100 hours on a 25 Horsepower Robin, stronger wheel motors, and a few other "upgrades" including a sweet floating seat. Approximately 7 years old. One of the attachments is a 48" finish mower. The middle of 3 blades keeps coming off while mowing. I have fixed 3 times in 1.5 months. It would seem that it is threaded so that it loosens as it mows my uneven 1 acre. Have others had this problem? The outer blades are perfectly fine. Every other attachment has been rock solid. PT indicates they have different mowing configuration now and this deck is unsupported. Their solution, buy the new mowing heads/cylinders and install. I have replaced front wheels and now have no problems with roll off, but this blade is really (finishing school requires omission of this word) me off. Any suggestions. I am going to raise the float even higher if possible.:confused2:

 

[3238dpw]

How is the mower cutting when it is together. I know it is a stupid question but I am wondering if your hydraulic lines are reversed making the mower run backwards. I have seen mowers with the blades on upside down cut kind of good.:confused3: It masks the problem

 

[Jiminy]

Scott, It seemed to be cutting fine. The hoses are male and female, and it appears to be Power Trac fittings. Good idea though. Thanks...

 

[frischtr]

I assume you are using lock washers under the blades? Not sure what the differences are between your configuration and the newer decks.

 

[BobRip]

Have you tried Locktite on the bolt threads. I would think this would help.

 

[woodlandfarms]

Instead of loctite, which I have done and now regret, might I suggest Calk.

 

[toy]

I purchased my PT used. 422 with about 100 hours on a 25 Horsepower Robin, stronger wheel motors, and a few other "upgrades" including a sweet floating seat. Approximately 7 years old. One of the attachments is a 48" finish mower. The middle of 3 blades keeps coming off while mowing. I have fixed 3 times in 1.5 months. It would seem that it is threaded so that it loosens as it mows my uneven 1 acre. Have others had this problem? The outer blades are perfectly fine. Every other attachment has been rock solid. PT indicates they have different mowing configuration now and this deck is unsupported. Their solution, buy the new mowing heads/cylinders and install. I have replaced front wheels and now have no problems with roll off, but this blade is really (finishing school requires omission of this word) me off. Any suggestions. I am going to raise the float even higher if possible.:confused2:

Could it be that the belt is threaded around that particular pulley wrong? Even though the belt may be tight maybe at some point the belt was replaced with either a shorter one or a longer one than what originally came on it in order to either take up the extra length or give it extra length to make it fit tight. If the motor is attached directly to that spindle then maybe it is turning in the wrong direction.

 

[Jiminy]

Guys, I used a new 3/8" grade 8 bolt with Permatex Threadlocker Blue. Red seems to be nearly permanent (like Loctite), so I thought I would go down one level to Blue to see if that will do the trick. If not I will move up the hold scale. The belts and other suggestions seem to be in order. Thanks for all of the tips and thoughts.

 

[J_J]

Have you applied enough torque, using a large wrench or impact wrench. My blades also have a large flat washer between the blade and bolt head. . The blades should be cutting in a counter clockwise direction,looking at the bolt side of the bld, so a right hand thread bolt should tighten up against the direction of force. If the blade hits something, that should also help tighten the bolt.

 

[J_J]

Torque specs, are based on non lubed fittings. Any thread additive, could allow over tightening. You could go well beyond the correct torque for the application.

The torque value is dependent on the friction produced by the threads and by the fastened material's contact with both the fastener head and the associated nut. Moreover, this friction can be affected by the application of a lubricant or any plating (e.g. cadmium or zinc) applied to the threads, and the fastener's standard defines whether the torque value is for dry or lubricated threading, as lubrication can reduce the torque value by 15% to 25%; lubricating a fastener designed to be torqued dry could over-tighten it, which may damage threading or stretch the fastener beyond its elastic limit, thereby reducing its ability to clamp a joint.

 

[Gravy]

J.J.

What are you thinking? A TORQUE SPEC on a PT? There ain't no such animal!

 

[MossRoad]

Boy, this is a weird one. I thought of all the things you guys did, too, like proper rotation, belt routed incorrectly, etc... The blade should rotate so the bolt gets tighter, so that made me thing if incorrect direction. The center blade is probably connected directly to the hydraulic motor through the spindle and has no slip connections. The outer spindles are powered by the belt which is rotated off of the center spindle and through the tensioner. The only way for the center blade to spin in the wrong direction would be if the hydraulic motor is turning in the wrong direction.

Very weird, indeed.

 

[toy]

Assuming that the bolt hole isn't wallowed out in the center spindle, I believe that I would make sure that the blades were all turned the right way and that none of them was backwards and that they all three were tightening up tight against the blade, and then I would observe the blade rotation [with caution] to make sure they were turning all the same way. They may be something keeping the center blade from tightening up all the way like it should. Maybe the blot is a little too long or there is a flange that the blade needs to slip over and it is not. Is maybe the blade bent or the center blade stopping abruptly and causing it to loosen up, while the two outer blades has a little give before they completely stop.

 

[KMA]

Easy way to verify all blades have the same rotation would be to lift the deck all the way up, turn off the tractor and move an outside blade by hand ensure the others move in the same direction.

 

[KentT]

I've attached a pic of the belt rounting on the 60" mower deck -- I don't know if the 48" is the same. As Moss described, the center arbor is driven by the hydraulic motor.

 

[J_J]

Measure the depth of the hole on the spindle and see if the bolt has enough space to tighten with sufficient torque. If not, grind off the end of the bolt to fit tight. Does your blade have a large washer next to the blade for the bolt to tighten?

 

[Jiminy]

I've attached a pic of the belt rounting on the 60" mower deck -- I don't know if the 48" is the same. As Moss described, the center arbor is driven by the hydraulic motor.

Thanks. I checked the belts and all seems to be normal.

 

[3238dpw]

Do you have a picture of the blade and is the bolt reverse thread or standard?

Seeing the KentT's picture of the mower makes me think about when i don't tighten one of my blades enough. This is on my Exmark mower and when I was very sloppy about tightening it, like I tightened it by hand and forgot to go back and use a wrench. If I don't use it very long and shut it down the blade's mass will make it want to keep spinning and since it wasn't that tight it would spin right off. I wonder if the Blade mounted to the motor is stoping more quickly then the rest due to it being solidly mounted and a small amount of slip in the belts. Then it is slowly turning a small amount every time you shut it off untill it finally comes off. I would try checking it every time after you mow if you are not already. After all it is easy enough to check, just a pull back on the stick and it is easily accessible.

 

[Jiminy]

Measure the depth of the hole on the spindle and see if the bolt has enough space to tighten with sufficient torque. If not, grind off the end of the bolt to fit tight. Does your blade have a large washer next to the blade for the bolt to tighten?

J.J., Thanks. Yes there is a large washer next to the blade for the bolt to tighten. It seems some of the thread may have been stripped in past lives, and it is only catching at the top of the spindle hole. In initial mowing yesterday, it seems to be holding. Thanks...your input along with everyone elses input has been awesome. Jim --

 

[Jiminy]

Do you have a picture of the blade and is the bolt reverse thread or standard?

Seeing the KentT's picture of the mower makes me think about when i don't tighten one of my blades enough. This is on my Exmark mower and when I was very sloppy about tightening it, like I tightened it by hand and forgot to go back and use a wrench. If I don't use it very long and shut it down the blade's mass will make it want to keep spinning and since it wasn't that tight it would spin right off. I wonder if the Blade mounted to the motor is stoping more quickly then the rest due to it being solidly mounted and a small amount of slip in the belts. Then it is slowly turning a small amount every time you shut it off untill it finally comes off. I would try checking it every time after you mow if you are not already. After all it is easy enough to check, just a pull back on the stick and it is easily accessible.

I mowed yesterday and checked it. I am going to start checking before and after. Probably one more step than I need, but it will mean that it always gets checked. Thanks, Jim --