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pgf

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Anyone have a nice way of fixing a worn pitman?  The wear I'm referring to is in the pivot holes at the ends. The holes in the two ends of my Davis pitman have worn to oblong, and together cause an appreciable "clunk" while treadling.  The proper way would be to bore the holes out to a larger diameter, and install a (brass?) sleeve.  I have a good drill press, but I'd need a stubby bit of just the right diameter, and I'd need just the right sleeves, etc.  And it would involve a cutting operation on a 140 year old piece of wood.  Not thrilled.

I'm thinking more along the lines of shimming with a piece or two of brass or copper or aluminum foil, at the "top" and "bottom" of each hole.  Thoughts?

Some pitman arms have what appears to be an oil hole on the end of the rod.  But since one of those holes points at the floor, it doesn't seem all that useful.  Others were made with a facility for compensating for wear:  the holes in my 29-4 pitman have a slider block that can be adjusted with a screw, to tighten the fit against shaft, over time.  (Those screws are stuck, and I've never adjusted them, but still...  they're there!)

The Davis pitman has neither the oil hole, nor the adjuster.


davis_pitman.jpg


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David

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Reply with quote  #2 
Drill out the hole and put in a brass bushing.  I did that once. Using a new piece of wood for the pitman, keeping the old one in case I decided it was needed for some reason.  I think the treadleon files has a mod where someone used a threaded rod bolted wood at each end so its length could be fine tuned.
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jplowrey

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Reply with quote  #3 
Quote:
Originally Posted by pgf

I'm thinking more along the lines of shimming with a piece or two of brass or copper or aluminum foil, at the "top" and "bottom" of each hole.  Thoughts?




davis_pitman.jpg


I like your idea of shimming with a piece of aluminum foil - it’s malleable, and if packed in tightly enough, would give some wear resistance. The foil would seem to be a no-regrets decision. If it doesn’t work out, or you don’t like the result, you should be able to remove with no damage to the original wood. Other materials to consider are copper foil or copper flashing (maybe harder to compress).

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pgf

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Reply with quote  #4 
David --  Without a stubby bit, I don't think I could keep the new hole from being off-center, due to wandering to meet the current hole's outline.  And while I realize the hole doesn't actually have to be centered, I think I would die a little inside if it wasn't.  :-)  (And I want to keep the machine as original as possible, so I don't want to make a whole new pitman.)

John --  Good point.  Shimming with foil is clearly "no regrets".  It's the obvious first choice.  Thanks.  I have both copper and aluminum foil on hand.

paul

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Rodney

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Reply with quote  #5 
I'd drill it and go with a brass bushing.  It'll last pretty much forever and if the bushing actually wears out it can be easily replaced.  To me it's the way it should have been made but there would have been higher costs to the maker. The repair will be invisible for all practical purposes. You said you have a drill press.  Buy a Forstner bit to drill the hole.  They're flat bottomed and won't follow the worn hole or wander once they're started but they do need a drill press for what you're doing. They're hard to start accurately by hand. 

Another choice would be to drill it out larger, put in a wood plug and re-drill the hole in the fresh wood.  The problem is the repair will be subject to the same wear as the original wood and will most likely show a little bit.
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pgf

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Reply with quote  #6 
Hmm.  Hadn't thought of a Forstner.  I have a set, though I haven't used them much.  I'll practice on some scrap and see how it goes.  They do have a tip, to keep them centered when starting, but I see that once the outer edge gets going, it won't want to move.  Thanks Rodney!

paul

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Farmer John

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Reply with quote  #7 
Pgf, there is no right or wrong way to take up the pitman slop, it just depends upon your resources.  If shimming, consider the use of strips cut from an aluminum pop can, which is about .005" thick.  Perhaps one or more full circles, with narrow strips placed behind the full circles of shim to take up the oblong of the hole.  Use some household glue to hold the shims in place.  The cans cut easily with regular scissors.  Aluminum  foil is only around .001" thick.
John
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pgf

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Reply with quote  #8 
Thanks John -- We have a winner!

I might have gotten to the aluminum can eventually (you know, just like Robert Pirsig, if you're a Zen and the Art of Motorcycle Maintenance alum), but maybe not.

I took some time while my shellac was softening to chop up a can.  One wrap, with a bit of overlap at the top of the oblong, and my pitman is fixed.  Fixed enough, anyway.

Good suggestion!

paul

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Farmer John

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Reply with quote  #9 
Paul, I was gifted a copy of "Zen and the Art of Motorcycle Maintenance" about 40 years ago.  Apparently, someone else thought that it was appropriate for me.

Great that you got the octane knock out of your pitman !
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Jim/Steelsewing

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Reply with quote  #10 
Quote:
Originally Posted by pgf
I took some time while my shellac was softening to chop up a can.  One wrap, with a bit of overlap at the top of the oblong, and my pitman is fixed.  Fixed enough, anyway.


Now that's quality even Pirsig could appreciate. [wink]

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