Bobtack on 853

[farmboy55]

Broke the ram rod on my tilt cylinder (853C) No problem there, getting a new one made. My question is??? I have around 1/2 " play on my bobtack, side to side, between my lift arms. Is this correct or should I put shims on the pins? dennis

 

[WebbCo]

That is excessive play in your bob tach, the tappered pins are probably too loose. The pins and bushings are pretty inexpensive but, continued use with that much play will do costly damage. Take the bob tach off and clean out everything, inspect the pins and bushings and replace as needed. When going back together tighten up tappered pin bolts to 200 plus lbs. Inspect the play and shim only if you have to. After everything is back together grease the zerks. Lock tite on the threads is a good idea too.

 

[skidsteer.ca]

I'd shim all but 1/8 of a inch out. all that movement is just wearing your pins and bushing out sliding back and forth as you work and sprinkling grit onto the pins. It's also hard on your tilt cylinder and pins, as it likely does not have 1/2 of side to side travel to "follow" the bobtach from side to side.
Ken

 

[Tazza]

I'd shim all but 1/8 of a inch out. all that movement is just wearing your pins and bushing out sliding back and forth as you work and sprinkling grit onto the pins. It's also hard on your tilt cylinder and pins, as it likely does not have 1/2 of side to side travel to "follow" the bobtach from side to side.
Ken

As Ken said, when you have side to side movement it gives dirt a point of entry to cause wear. I made nylon shims for mine and there is no side to side movement. This goes for where the tilt ram attaches tot he bobtach, you want a snug fit here to. As its a part that is going to always get exposed to dirt when you fill the bucket and it over flows.

 

[perry]

As Ken said, when you have side to side movement it gives dirt a point of entry to cause wear. I made nylon shims for mine and there is no side to side movement. This goes for where the tilt ram attaches tot he bobtach, you want a snug fit here to. As its a part that is going to always get exposed to dirt when you fill the bucket and it over flows.

Make sure you remove the two grease fittings where the arms connect to the attachment plate, the tapered pins will not slide in far enought in to remove the attachment plate with the grease fittings installed. Pick up a 8" bolt to pull the pins into the arms after you install new bushings.

 

[farmboy55]

Make sure you remove the two grease fittings where the arms connect to the attachment plate, the tapered pins will not slide in far enought in to remove the attachment plate with the grease fittings installed. Pick up a 8" bolt to pull the pins into the arms after you install new bushings.

Thanks for the info guys, I have it apart and picking up new bushing's for it in the morn. dennis

 

[Tazza]

Thanks for the info guys, I have it apart and picking up new bushing's for it in the morn. dennis

If you replace the pivot bushings you really should do the pins too.

 

[perry]

If you replace the pivot bushings you really should do the pins too.

Tazza, should the pins be replaced if there is no play after installing new bushings?.

 

[skidsteer.ca]

Tazza, should the pins be replaced if there is no play after installing new bushings?.

My pins were worn .018" undersize, I re used them.
I ground the center bigger on a couple flat washers and shimmed all the side to side slop out though, I hate it when this is over .125" it wears the pins/bushing needlessly.
Ken

 

[Tazza]

My pins were worn .018" undersize, I re used them.
I ground the center bigger on a couple flat washers and shimmed all the side to side slop out though, I hate it when this is over .125" it wears the pins/bushing needlessly.
Ken

If it was my machine i would replace them, but i'm fussy and made my own pins and bushings.
If they feel good, i see no reason why you can't re-use them. I'd replace them of they felt sloppy. The more clearance the more dirt can enter wearing out the new bushings.
As ken said, his were worn .018" thats fine. A machinest buddy of mine likes to have clearance of at least .020 on all pins and bushings on earth moving gear. I made all mine .005" and figured they would wear in over time.
It would be a good idea to bush between the arms and bobtach. I made nylon shims for mine, i have no play from side to side.

 

[farmboy55]

If it was my machine i would replace them, but i'm fussy and made my own pins and bushings.
If they feel good, i see no reason why you can't re-use them. I'd replace them of they felt sloppy. The more clearance the more dirt can enter wearing out the new bushings.
As ken said, his were worn .018" thats fine. A machinest buddy of mine likes to have clearance of at least .020 on all pins and bushings on earth moving gear. I made all mine .005" and figured they would wear in over time.
It would be a good idea to bush between the arms and bobtach. I made nylon shims for mine, i have no play from side to side.

I used a couple of pin shims for a John Deere Skidder, that's all taken car of. Now a diff. day diff. repair / problem. I'll put that on a new post. dennis