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Aircompressor Kaput

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Groundhog

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#1
My old, tired, used air compressor has almost quit compressing air. So time for a rebuild. Thought a few pictures along the way might be interesting.
The compressor is an Emglo model DU. Rated somewhere around 18 CFM @ 125 psi. It has only been operating at about 1/4 of that since I bought it 4 years ago, so needing a rebuild isn't a surprise. In fact what is a surprise is that I haven't had to do it before now.
My findings: Out of 4 valves in the valve plates 1 is completely gone, 1 was just floating in space and the spring for one is in 3 pieces. 2 piston rings are frozen and collapsed on the pistons, one cylinder has a pretty good score, and the unloader valve is crusty.
All that and it was still working, abet taking longer and longer to fill the tank to 110 psi!
Since I don't really need the entire capacity that this thing is capable of when in tip-top shape I'm going to cut a few corners to save a few bucks. Where I should replace the bad cylinder and a couple of pistons I'm just going to hone the cylinders and re-establish ring clearance with a jewelers file (they don't make oversized pistons). I was planning on replacing the rod bearings and crank bearings but there aren't any rod bearings! No obvious play in the rod big or little ends. And the crank feels good so I'm going to take a chance and just leave the bottom end alone.
A gasket, ring, valve and air filter kit is available for about $220. I can always take it back apart later if I decide to replace something I'm not doing now.
Pics;
0398.jpg 0404.jpg 0405.jpg 0406.jpg 0411.jpg 0413.jpg 0415.jpg 0416.jpg
 

Ulma Doctor

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#2
just making the repairs will show a significant increase in CFM's to the tank

i worked in a rental yard for a minute when i was just out of high school.
my boss was a tight wad with the funds to maintain the fleet. he wanted the dollar to go further than it should .

but one thing i got good at was swapping air compressor components from unit to the next.
once a cadaver was made by a customer, i'd quickly dissect the carcass and remove any organs fit for transplant into other victims.
i was amazed how long some brands like emglo could take abuse before they quit

if you can get a cylinder hone of the right size or a speed hone even, you'll be able to whip the cylinders into better shape easily
the rod bearing surface looks good to go.

i wish you the very best of luck
i'm looking forward to see how she turns out :grin:
 

Ken from ontario

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#3
That looks like one solid , heavy duty motor once it's rebuilt,best of luck.
 

brino

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#4
@Groundhog,
I definitely support the minimalist approach for a quick rebuild.
I bet you get 90% of the function for 10% of the cost.

That's a nice heavy rig, and looks to be in good hands.

Looking forward to the rest!

eating-popcorn-smiley-emoticon-1.gif
-brino
 

ConValSam

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#5
You will likely pay for the rebuild with the savings in electric usage!

Have fun and thanks for a fun project to follow.
 

kvt

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#6
Those old ones rebuild and keep going. I have an old big Kellogg that could be use the same, but do not use it so it just sits.
 

Scruffy

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#7
Go for it groundhog just a hone new rings and valves working at 75% will probable last a long long time
Thanks ron
 

Groundhog

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#8
Thursdays compressor bumbling . . .

0422.jpg Think I found where some of the missing parts went! Those are steel bits embedded in the aluminum piston.

0423.jpg Part of the ring land smeared over the ring. Ring land is squished in several places compressing the ring. Probably should have bought a new piston or two but the overhaul kit was already on its way by the time I looked this close. I straightened it all out with a jewelers file!

0430.jpg I think in my broke hot rodding days I raced cars with pistons worse than this! This one is ready to go.

1429.jpg Chucked 2 of the pistons up to polish the real bad scratches (high parts anyway) out of the skirts with Scotchbright. Hopefully there won't be enough abrasive transferred to the skirts to hurt anything.

0436.jpg I forgot how much I really hate scraping gaskets. May well be the reason I quit wrenching for a living. It was so bad I drug my little HF compressor from the garage and put up with its .005CFM (ok - maybe it has a little more CFM) running a air grinder with a scotchbright pad.

0433.jpg I knew it probably had a rough life, but how do you break this? Still holds torque on the bolt though.

0440.jpg Jugs need honed yet and it all needs cleaned and flushed one last time, but this much is ready for assembly.
 

RandyM

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#9
Great thread Mike! Keep it coming. :encourage:
 
F

f350ca

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#10
Nice rebuild Mike.
For low pressure high volume like this compressor was meant for a four cylinder single stage makes sense, why are they so uncommon. Any four cylinder I've seen is a two stage.

Greg
 

Groundhog

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#11
Nice rebuild Mike.
For low pressure high volume like this compressor was meant for a four cylinder single stage makes sense, why are they so uncommon. Any four cylinder I've seen is a two stage.

Greg
When I get it back together I'll check the CFM. I've seen several specs, all around 16 to 20 CFM at 125 PSI. According to Jenny (who bought Emglo) the model number breaks down to 3 hp, 175 psi, 30 gallon, vertical tank. If I can get 1/2 to 1/3 of those figures it will easily out perform any needs I have. I only paid $75 and 100 miles for it 4 years ago. It has a new (huge) Lesson 3 hp motor on it and the tank looks perfect. I did have to put new belts on it last summer - I couldn't stand the sequel at start-up any longer!
 
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Groundhog

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#12
I was sure the rebuild kit wouldn't get here until after Christmas so I've just been lazing around reading a book & taking naps. So you know what showed up today. Figured I'd better get back out & do a little anyway.

I finished getting the old gaskets off the valve plates and heads. Head gaskets were almost permanent. I couldn't decide if I should use a hand scraper and wear myself out of use a grinder with a scotchbright pad and eat all the dust. Ended up doing both.

0441.jpg There are quite a few more valve parts in this kit than came out of the compressor. But, all of them will go back in! I think the missing pieces are in the bottom of the tank!

0445.jpg The holes for the in-head unloading valves were pretty rusty and pitted. I used a worn out sanding drum on a rotary tool to clean them up a little. The seal is an o-ring so I should be good here.

0448.jpg This is a very bad picture of the worst cylinder as it came out of the pump. Several of the scores are probably 0.010" to 0.020" deep. I'm going to try honing the other smaller dings out and not worry about the deep ones. They do not offer an oversize piston so the option was to replace the cylinder and piston.

0453.jpg I think I'm done honing this cylinder. I may change my mind when I go back out there later this evening and do a little more. Honing sure is a messy job. I've got dirty oil splatters on the floor (and everything else) for 5' left and right from slinging off the hone.

Still have the other 3 cylinders to hone. They aren't scared up as bad though.
 

Groundhog

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#13
Sunday,
Honed the other 3 cylinders. Would liked to have done a little more but completely wore out a HF 4" hone ($25). Didn't notice when I bought it that it doesn't have replaceable stones. I guess most cheap hones don't anymore. I should have just gone to an auto parts store and rented a good Leslie hone & purchased their stones. Would have been far better stones I'm guessing.

Installed the new rings. That always scares me; stretching brittle little rings without breaking them. Got them all on though. I wedged a small block between the piston skirt and the compressor block that kept the piston steady while spreading the rings.
0460.jpg

Got one cylinder bank on. Too much sweating and cussing trying to get 2 pistons to line up, keep the crank from turning, keep the gasket from getting wadded up and compress the ring with a screwdriver, all while ramming the screwdriver into my palm numerous times to try and install the 2nd cylinder block. I'll wait until Tuesday when I can get a couple of worm drive hose clamps to use as ring compressors.
0462.jpg

You all have a Merry Christmas!
 

Ulma Doctor

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#14
looking good Mike!
Merry Christmas!
 

kvt

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#15
That is looking great. The one side should help hold thing steady while you put on the other one. And now that you know how to do it, it may go better.
Have a Merry Christmas
 

Groundhog

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#16
It works! Finished it up a bit ago.

0465.jpg After that last cylinder block I wasn't about to try to get this one on just using a screwdriver for a ring compressor. I was close to putting tool holes in the walls yesterday. The hose clamps worked great. A regular ring compressor would have been too tall.

0472.jpg Installing the internal unloader valves. I think these are for running with a gas motor that does not shut off but just drops down to an idle when the tank pressure is reached. They bypass the incoming air, not the pressurized air. I honed the holes with a 3/8" rod cut down the center to hold a piece of emery cloth on a drill. (bottom of picture - the unloader valves are in the heads). Above the oil can is a valve block that houses 2 intake and 2 exhaust valves (the valves are a metal disk, a conical spring, a spring retainer and a snap ring).

0476.jpg One of the 8 valve seats. Pitted a bit. This valve (and another just like it) had my blood pressure up near aneurysm pressures. Both ends of the snap ring are broken off. Couldn't get it out of the slot. Tried seal picks, needle nosed pliers, screwdrivers, etc. Finally just got P.O. ed and started wacking it with a hammer and chisel. Finally bent enough to get a seal pick under it.

0475.jpg A HR 1" sanding disc with light pressure in the drill press was just right to "grind" or face the valve seats.

0482.jpg Pretty much together. I didn't replace the end cap gasket or the crank seal as they were not leaking and can be easily changed if/when needed.

0484.jpg Like that little 3 HP Leeson motor? I don't know how old it is but if I ever need to replace it I can just sell the copper in the windings to pay for a new motor! I put new bearings in it last year. The sucker is heavy.

OK, now the important part. How good does it work?

I calculated 14.72 CFM @ 127 PSI. It might even get a little better as the rings seat (and some of the cylinder gouges get filled with crud!!).

I'm pretty happy with that. I sure don't have any air tools that need anywhere near that capacity. But I sure made a mess!
 

Ulma Doctor

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#17
nice work !!!! :grin:

i should have suggested earlier to use modified empty soda or beer cans as a makeshift piston chute.

i was in the field and woefully under equipped- but not without wits, i successfully saved a Briggs and Stratton I/C engine
by putting some new rings and filing a piston back into shape, i used a soda can with the ends cut off and slit up the middle.
 

Groundhog

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#18
nice work !!!! :grin:

i should have suggested earlier to use modified empty soda or beer cans as a makeshift piston chute.

i was in the field and woefully under equipped- but not without wits, i successfully saved a Briggs and Stratton I/C engine
by putting some new rings and filing a piston back into shape, i used a soda can with the ends cut off and slit up the middle.
Good idea. Wish I'd been smart enough to use either method before I tackled the first cylinder block. I'm still a little stressed from that!
 

KBeitz

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#19
When you need bigger pistons and you can't get then you can have your pistons swelled.
They knurl the skirt to make it swell...
 
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