'68 Cat 12F Grader Circle issue

[Onfoot]

Hanna the Grader (my '68 12F grader) is running well and earning her keep with all the snow we've been needing to clear this month. But there is an issue with the circle control in the power control system. Circle turns fine clockwise. But counter clockwise intermittently results in an unhealthy clattering noise. And on Friday, there was the noise and then sheared the shear pin. After 3 more shear pins, I turned the circle clockwise without issue and did a bit of plowing before needing to turn counter clockwise again. But this time it moved counter clockwise with no issue.

I'm very much a newbie in all this and the maintenance manual does not have much to say beyond a general description of the Power Control box. If I had to guess, it would strike me as a gear with a bad tooth that gets caught in the bad spot sometimes...)

Any wisdom out there about something like this? Thanks!

 

[pedrocar]

Take a look at the pinion may irregular wear on the count clock side and wear on the circle teeth ,May have been an operator favored that side to work

 

[cuttin edge]

Not too familliar with Cat, but I ran an old Champion that would jam when the circle needed to be re shimmed. Sometimes it would be a timing issue which would be a totally different situation from your Cat, but to get out of a jam, sometimes a little ground pressure can help unstick it.

 

[56wrench]

check for excessive movement in the input shaft of the small gearbox down on the circle and look up underneath and check the circle pinion for excessive movement and wear. as said above, maybe the circle needs to be re-shimmed

 

[Theweldor]

The teeth on the pinion will wear and the teeth on the circle will wear from running in a small range of motion constantly. Both pinion and circle segments can be had from Cat and the segments replaced. Have done several over the years.
Just something else to check.

 

[Coaldust]

Always nice to hear about Hanna. Appreciate the update.
We probably deserve some pictures.

 

[ovrszd]

The teeth on the pinion will wear and the teeth on the circle will wear from running in a small range of motion constantly. Both pinion and circle segments can be had from Cat and the segments replaced. Have done several over the years.
Just something else to check.

And that wear will be on the "counter clockwise" side of the gears because most of it's life has been spent moving material to the left.

 

[Bluox]

Hanna the Grader (my '68 12F grader) is running well and earning her keep with all the snow we've been needing to clear this month. But there is an issue with the circle control in the power control system. Circle turns fine clockwise. But counter clockwise intermittently results in an unhealthy clattering noise. And on Friday, there was the noise and then sheared the shear pin. After 3 more shear pins, I turned the circle clockwise without issue and did a bit of plowing before needing to turn counter clockwise again. But this time it moved counter clockwise with no issue.

I'm very much a newbie in all this and the maintenance manual does not have much to say beyond a general description of the Power Control box. If I had to guess, it would strike me as a gear with a bad tooth that gets caught in the bad spot sometimes...)

Any wisdom out there about something like this? Thanks!

You been pushing snow over the blade? Maybe there was snow or ice in circle teeth?
Bob

 

[Fat Dan]

You been pushing snow over the blade? Maybe there was snow or ice in circle teeth?
Bob

O' Good thought ..... I'll keep an eye on that too. ... thanks

 

[Onfoot]

There is some excellent wisdom here. Thanks! I am now trying to get my hands on a parts and repair manual for the old girl. S/N 59H498 (Canadian equivalent of USA 73Gxxxx series). We still have a lot of snow on the ground. Once it has dried up a bit I will be doing more sleuthing on the circle issues (along with general maintenance stuff).

Coaldust asked for some pics. One is below. Plus a bit of video (if I figure out how to embed it. Had to link it to my FB page to get the video to maybe show up... )

FB Video

 

[grandpa]

Im glad I told you about the shear pins from the git go!

 

[Coaldust]

Great picture!

 

[Fat Dan]

Went by and took another picture of my new old No.12 8T today

 

[Fat Dan]

I talked to the ol' guy and he said it needed a carb rebuild... I told him I have one newly rebuilt one at the house. He also said it has new tires all around and had less than 8 hours and them, he laughed and added, most of the was idling around the yard.. The guy he got it from couldn't find a S/N tag but said it was a lateish 54. I can't see the tag on the A frame and the engine tag , if still there, is on the other side and it is inaccessible at this time. I also cannot see any casting numbers to help further identify the old beast.
Smilting It's melting .... Things about to get muddy ... everything.