Fairbanks Morse repairs

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GlennW
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Location: Florida

Fairbanks Morse repairs

Postby GlennW » Sun Oct 31, 2010 10:39 am

I drug my 1924 6hp Fairbanks Morse Z engine (900 lbs) off of the shelf to tinker with and decided to repair a few things.

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First problem was the air valve on the mixer, (carburetor) which was worn out, riddled full of excess holes, and had a few holes plugged and brazed up, so I made a new one.
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Next was the starting fuel needle valve which had been repaired by drilling the old tip, threading it, installing a steel screw, and re-tapering it. So I made a new one.
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Next on the list was a sloppy throttle shaft and worn throttle plate.
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The throttle shaft bore was worn and misaligned as the casting most likely shifted in the last 86 years so I line honed the bore until it was straight and round, which took it from .375” to .385”.
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Next I took some 7/16 brass rod (original shaft is brass) and turned it down to .384” and a short area on the end to .375” to accommodate the throttle arm. Then milled the flat on it for the throttle plate and then drilled and tapped it for the throttle plate screws. It fits in the bore and rotates with silk smoothness.
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Next was to cross drill the new shaft for the pin that secures the arm to the shaft. The hole was apparently not fixture drilled, as it was not through the center of the shaft! This required some simple fixturing, as the arm needs to be indexed to the throttle plate and the hole located to where it lines up with the existing holes in the arm.

First I put the original shaft in a index head and found that the hole was indexed exactly 60° to the throttle plate, so at least I was not working with an arbitrary angle. I also found that the cross hole was perpendicular to the shaft, so that made it a bit easier as well. I set up the old shaft in a V-block in the vise and used a drill blank to locate the hole in relation to the spindle. Then I dug out my “high tech” drafting triangle and set it between the vise jaws and the flat for throttle plate, and it matched up perfectly. At the same time it located the edge of the flat with the side of the V-block. I put the new shaft in the V-block, used the “high tech” plastic triangle to index the shaft, and drilled the hole!
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The pin fits, is perfectly aligned with the holes in the arm, and the whole deal rotates just as smooth as silk. Now I just need to get some brass sheet and make a new throttle plate.
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Next up is the cylinder head. Really badly worn valve guide bores, and to top that off a previous owner poked a reamer through them to oversize them. The intake valve bore wasn’t too bad, but the exhaust bore was a mess, as not only didn’t the bore clean up, but the reamer went in crooked as well, as it was apparently done with a hand drill. The valves are also a mess as they cut off the old stems and welded on larger dia stems, then turned them down a bit to fit the bores. The stems were no longer concentric with the heads as they must have chucked them up using a three jaw with about .007” runout!

Anyway, the exhaust guide bore was repaired by putting it back on location and sleeving it with bronze so that new stock valves can be used. I considered making the valves, but used a bit of sense and ordered them new, as they are available for $38.00 each.

Here the guide has been repaired, and the seat rough machined. It will get touched with the seat grinder after the new valve is properly fitted.
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Now the intake guide bore will get the same treatment.
Running the boring bar through the guide bore to get it straight and round again and ready for a bronze sleeve.
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Hopefully, this thing may actually run pretty well whan it's done! It's throttle governed rather than hit and miss, and runs on Kerosene. It has a small gas reservoir that is used to start it and warm it up prior to switchig to kerosene.

Unfortunately, I need to get back to my real job on Monday...
Last edited by GlennW on Mon Nov 01, 2010 8:47 pm, edited 2 times in total.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Harold_V
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Location: Onalaska, WA USA

Re: Fairbanks Morse repairs

Postby Harold_V » Sun Oct 31, 2010 2:54 pm

Nice, Glenn.
I'm curious about your choice of honing head. Is there a reason you didn't use your large Sunnen to hone the .375" bore? Looks like you were working out of the pan. Must be something I don't know that lead to your decision.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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GlennW
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Location: Florida

Re: Fairbanks Morse repairs

Postby GlennW » Sun Oct 31, 2010 3:17 pm

Hello Harold,

I had the honing machine set up for a different job and didn't want to go through the whole drill ofor one small bore. My machine possibly differs from yours in that the spindlenose is adjustable so you indicate the mandrels in so they run perfectly true so the part does not wobble, therefore achieving greater accuracy. It is actually a very nice feature, but can take a few minutes to center up.

I also have the stand and drip tray off of my old lathe that I use as a honing stand along with a pump system for the oil. I use it for honing the guides on the V-12 cylinder heads. I use the gimbal mount hand held hone in the above pic with a pneumatic drill to do so, and it is a very nice, very accurate, honing setup once you develop a feel for it. I had a leaky hose on that system, so I just used the hand held hone in the tray of the larger machine, as I already had an air hose over there as well.

I usually take the path of least resistance when I'm trying to get something done... :wink:

The people that think flood coolant would be too messy, have obviously never played with proper hones! :D
Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!

Harold_V
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Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Fairbanks Morse repairs

Postby Harold_V » Sun Oct 31, 2010 9:47 pm

Thanks, Glenn.
Yep, my honing experiences (several years) revolve around only one machine, that a 1290-D, which is also the model I have now. They are a limited capability machine in that they are not a stroker, nor can the mandrel be trued for concentricity. They also have only four speeds, unlike later machines. Therefore, I've never had that capability, but I can see, for a heavy work piece, it could prove to be the difference between success and failure. Fortunately, all of the work I did was small, so that was a non-issue. That may not be the case now, so I may come to understand the need to dial in the mandrel.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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GlennW
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Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Fairbanks Morse repairs

Postby GlennW » Sat Dec 04, 2010 5:41 pm

The Carb/mixer throttle bore was a bit rust pitted so I set it up and bored and sleeved it. (No Harold, I did NOT put those nicks in the table, they were in there when I got the machine :( )
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The throttle plate (butterfly) was worn badly as well, so I turned a brass bar to the proper diameter and took a .035" slice off of it for a new one using my cold saw. Now it just needs the two screw holes in it to secure it to the throttle shaft.
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The bracket that holds the magneto, camshaft, driven gear, and governor needed a bit of help as the bore for the canshaft/driven gear was a bit wollowed out.

The setup was interrestingg as I'm finding that hardly anything is square or parallel on this old engine, including this bracket. I needed lots of shims to get the bores perpendicular to the spindle and then bored the camshaft bore .063" over size.
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Made a bronze bushing, then pressed it in and honed it to size.
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It needed a grease dispersement groove in the bushing, so i ground a stand up threading insert to the profile I wanted and then screwed the insert into a boring bar and used the carriage to scrape a groove in the bushing.
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Done with that job.
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Glenn



Operating machines is perfectly safe......until you forget how dangerous it really is!

Russ Hanscom
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Location: Farmington, NM

Re: Fairbanks Morse repairs

Postby Russ Hanscom » Sat Dec 04, 2010 10:53 pm

That is one busy and very productive day.

davec43
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Joined: Thu Dec 17, 2009 6:26 pm
Location: 108 Mile Ranch, BC

Re: Fairbanks Morse repairs

Postby davec43 » Sat Jan 28, 2017 10:44 pm

Hi Glen,
Nice work! Lots of familiar looking parts here. I have a 1931 5hp Z sitting under a tarp in my back yard. It runs well until something gets loose and falls off! Interesting old engines.

Dave
Dave C

Grizzly 12x36 lathe, Gorton 1-22 milling machine


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