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dkaustin
07-12-2009, 03:20 PM
I rescued an air compressor that my neighbor set out at the curb (Campbell Hausfeld 11 gal 2HP Cast Iron, 5.5 cfm @ 40 psi, 4.6 cfm @ 90 psi). The lower connecting rod bearing was seized, probably from letting the oil level drop too low.

There is some scoring of the crank pin, a little heavier scoring of the die cast connecting rod bearing halves.

Question: What has to be done to get this compressor running again? I don't need it for heavy or frequent use.

Can I just clean up the high spots on the scored areas? Do I need to bore out and sleeve the bearing? Should I forget about it and set it back out at the curb?

Aside from the obvious problem, the compressor otherwise appears to be in good shape. The other bearings are smooth and have no play, and the motor runs well. If the previous owner neglected the crankcase oil, he probably wasn't religious about draining the condensation from the tank either, but that's another issue.

hawgwrench
07-12-2009, 05:25 PM
DK....small world....I've was just given a somewhat larger compressor with the same prob. Matter of fact I signed in to ask almost the same question as one journal on the crank in this one is bad. Doesnt look like a big job to fix,polish the crank,shave the end cap on the rod and re-bore it. Any ideas on clearance for the big end of the rod to the crank? This ones alloy rods with iron crank. Hope I'm not hi-jacking your thread here,it just seemed we had the same problem,as this could be the solution for your find as well.

kf2qd
07-12-2009, 06:17 PM
What is the throw on the rod journals? Can you build a couple fixtures to mount it between centers and grind it?

If you were to do that then you could bore the rod and make a bronze insert and be back in business.

dkaustin
07-13-2009, 11:51 AM
hawgwrench- Right now, I'm leaning toward the approach of cleaning up the crank pin with successively finer grades of emery paper, shaving the end cap (and maybe the rod end), and re-boring the bearing about .0005 larger than the crank pin diameter.

kf2qd- Your approach strikes me as the RIGHT way to do it, although it might be a stretch for someone with my limited equipment and skills. Let me try it the cheap and easy way first, then when it comes back to bite me I'll do it again the right way:D!

Falcon67
07-13-2009, 11:54 AM
I think .0015 min is a better spec for the rod clearance. .0005 is a free running press fit IMHO. ;)

aboard_epsilon
07-13-2009, 11:59 AM
DK....small world....I've was just given a somewhat larger compressor with the same prob. Matter of fact I signed in to ask almost the same question as one journal on the crank in this one is bad. Doesnt look like a big job to fix,polish the crank,shave the end cap on the rod and re-bore it. Any ideas on clearance for the big end of the rod to the crank? This ones alloy rods with iron crank. Hope I'm not hi-jacking your thread here,it just seemed we had the same problem,as this could be the solution for your find as well.

i cant visualise this ..shave the end cap and re-bore

something says to me

shave the end-cap ..and you get an oval that when re-bored requires bigger crank-pin .

or do you mean that only the very top of the bearing wears away ..and you're just re-boring and taking off what was displaced by the shaving action

all the best.mark

barts
07-13-2009, 12:05 PM
Shave the mating surface of the end cap, bolt back together and rebore w/
a thou or two running clearance. This isn't perfect, as the side of the hole doesn't get cleaned up - but there's very little load there on a compressor - they don't turn very fast - almost all the load is either gas pressure on the top surface or inertia loading on both top and bottom.

This was standard practice on steam and early gas engines for a hundred
years.

- Bart

firbikrhd1
07-13-2009, 01:41 PM
Actually this method is used to rebuild connecting rods for car engines on a regular basis. Both the cap and rod end are "shaved" a few thousandths, bolted back together, torqued and honed to the proper size. The hole ends up nice and round and properly sized. If you think about it, when both parts have some material removed the hole does get oval but the dimension across the area where the rod and cap meet doesn't "shrink" as much as in the other direction. It does "shrink" enough to allow material to be removed in all parts of the circumference to end up with a round hole.

Falcon67
07-13-2009, 04:15 PM
Actually this method is used to rebuild connecting rods for car engines on a regular basis. Both the cap and rod end are "shaved" a few thousandths, bolted back together, torqued and honed to the proper size. The hole ends up nice and round and properly sized. If you think about it, when both parts have some material removed the hole does get oval but the dimension across the area where the rod and cap meet doesn't "shrink" as much as in the other direction. It does "shrink" enough to allow material to be removed in all parts of the circumference to end up with a round hole.

But you have to take care to re-bore the hole so that the rod dimension is not changed - in a car engine, if you lose rod length you pull the piston down the bore and reduce compression. If you shave the rod end, you reduce length. Probably not a big deal in a compressor, big deal in an engine.

firbikrhd1
07-13-2009, 05:17 PM
Falcon 67,
True, the rod will be a tiny bit shorter, but only a few thousandths. It also changes the rod length ratio but again not enough to make a difference. Usually in an engine any compression loss isn't a factor as it is minimal, particularly in a race engine where the pistons will be changed. In that case compression is easily made up. If stock pistons must be retained because of a particular racing class the block can be decked enough to correct for the miniscule rod length change.

hawgwrench
07-14-2009, 06:55 AM
I spent most of the day yesterday working on this,after few phone calls placed to verify clearances. Turns out that a couple thou is just right on the crank pin clearance, with three being the high side. I did have to take quite a bit off of one rod and cap to get the bore cleaned up,but it came out looking pretty good .The cylinders themselves are another story. One was literally half full of water when I tore it down,and being as that I really didn want to go on the hunt for parts for this (good luck finding oversize pistons for an old chicom compressor with no identifying markings:rolleyes: )I just spent a bit more time with the hone. One cyl cleaned up nicely,the other is serviceable but not perfect. Started putting everything back together and broke on of the cast compression rings:eek: ,so had to order another set. Turns out that the o.d. for one of the briggs ring sets was pretty close,I'll have to file to fit tho.So now I'll have 20 bucks in a free compressor,assuming it doesnt blow:rolleyes: ....and if it does,oh well....easy come easy go.I'll update later on,rings should be here this week.

barts
07-14-2009, 08:30 AM
When you start it up for the first time, open the output so it cannot build up any pressure and just let it run for an hour to get the parts "used to" rubbing together.

- Bart

TGTool
07-14-2009, 10:57 AM
Hmm. Kind of a "get acquainted" session - give all the parts little name tags, drinks, snacks, maybe some get acquainted games. A few drops of alcohol here and there should loosen them up nicely, but keep the bedroom door locked.

Falcon67
07-14-2009, 12:52 PM
My new Campbell compressor required a 30 minute no load run time before use. Use non-detergent oil, either compressor oil or 10w-30.

O/T sorta - On the rods - I build performance engines for my race cars and if I take a guy a set of rods and they come back .001 short that shop is going to eat some rods, make 'em right or buy me another set. I don't pay for having rods shortend. If I want the piston top positive of the deck or some spec below the deck, I will control that with the deck cut unless forced to otherwise. The rod center-to-center and the piston pin height better be dead on to the spec - because any replacement better be dead on to the spec for dimension and weight, otherwise that cylinder is off from the others. For a mild performance engine maybe not a big deal, at 7000 RPM plus and 500, 600, 800, etc HP it's a bigger deal. To have the pistons modified to take up that .001 or .002 or whatever, you are looking at $1000 more or less for a set of custom pistons with a custom pin height. They don't make just one. .001 makes a difference when you have $5000 tied up in a mild bracket engine, never mind in a $35,000~50,000 Top Dragster motor from Reher-Morrison or Sunset Racecraft. .001 could be the difference between running at top power and an intake valve kissing a piston. The deck on the engine in the Falcon right now has a deck that is zero with one cylinder -.0005. I pay for precision, I better get it. I can live with 5 tenths. Just my .02$

dkaustin
07-14-2009, 02:55 PM
I did the repair, put it all back together, and let it run for 1/2 hour unloaded, then called for a little pressure. Looks like I've got a compressor:D!