# A Non Conventional Repair Of Old Air Compressor



## petcnc

Some 15 years ago a relative of mine gave me a broken air compressor for parts.

It was a small unit (0.5 HP motor) with separate motor and compressor over the air tank unit similar to the following (internet) photo.





I used the air tank right away, as I had an all-in-one model with a small air tank. As at the time my only tools were a drill, a hammer and some spanners, I threw the compressor and the motor in a box put them deep in the basement and forgot it.

Last weekend I was cleaning the basement and planned to throw away stuff  to make some space. When I opened the box and saw the compressor and the motor I thought: I CAN FIX IT!!

Needless to say cleaning stopped instantly!

After a thorough visual inspection & some continuity measurements, I connected the motor to the mains (220V over here) and it worked ok with some bearing noise though.




Next thing the compressor.

The compressors consists of 4 parts:

Body, cylinder, reed valves and head.




The main problem with the compressor was the cylinder.

As the head was bolted on the top part of the cylinder and probably due to air leaks previous user over tighten the head bolts and broke the cylinder top. The cylinder top was full of cracks (red to the following sketch)…




To find a part for a 30+ years old no-name compressor is out of question, so it is time for a quick, easy and long lasting solution…

The problem of the cylinder is on the top part where the piston compresses the air and great forces, heat and tremendous pressure applies to the cylinder…

I was holding the cylinder and squeezing my brain for a solution to the problem for some time.

Can I weld it?

It is cast iron and I’m not sure I can do it.

Can I machine a new one?

Too much trouble for an old compressor. I’d rather clean the basement twice!

I slept on the problem and next morning the solution came while I was finishing my cup of coffee. As I lifted the cup to drink the last drops of coffee I solved it!

 I WILL REVERSE THE CYLINDER!! with the square side to the top and I will add a plate to the bottom.




In the shop in no time. Measuring, looking for parts, bolts and gasket material…

A few details needed sorting out though. As the bottom of the “reversed” cylinder had cracks all around it would be impossible to seal it or to support it properly. It needed to be removed!

Cylinder to the lathe cleaning the broken part and adding an aluminum ring to keep the proper stroke distance.





After a couple of hours the results were very satisfying

I made the Bottom plate for the cylinder that will connect directly with the head using long bolts (you can see the round bolt heads)




I machined the ring that press fits the bottom of the cylinder (you can see the bolts that connect plate and head also)




 The inside-view of the ring below the piston (7.2 mm internal width 13.1 external)




Gaskets below plate (red) and between ring and plate (gray)





At  the top of the cylinder there was a need for a gasket between reed valves and the cylinder top.

The best material I could think of was copper. So I annealed a piece of copper to make it soft and I cut the gasket.




Trying to remedy the initial problem that caused the whole issue (i.e. the possible air leak at the head of the compressor), I used my surface plate and cleaned both surfaces of the reed valves using 600 and 1000 grit sand paper . Sorry, I was too busy and focused to take photos, my reeds are similar to those (internet photo)



Final compressor unit assembly




And ready to be tested with it's 0.5 HP motor!




IT RUNS FLAWLESLY

Thanks for reading

Petros


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## David S

Holy crap Petros.. lots of work.. nice going.

David


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## petcnc

David S said:


> Holy crap Petros.. lots of work.. nice going.
> 
> David



I enjoyed fixing this VERY MUCH!!! 

It was like going back in time.


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## Eddyde

Brillant solution! Awesome presentation!


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## Subwayrocket

petcnc said:


> Some 15 years ago a relative of mine gave me a broken air compressor for parts.
> 
> It was a small unit (0.5 HP motor) with separate motor and compressor over the air tank unit similar to the following (internet) photo.
> 
> The main problem with the compressor was the cylinder.
> 
> Petros


  Just one word of caution. If you dont have a small endoscope , borrow one or cheap one usb one off Amazon. Look up inside the tank, if you plan to use the tank.  I friend of mine had an old compressor burst in his shop. They were hospitalized a few months, both seriously injured and scarred. If it's been sitting a while and/or the last owner didnt drain it often , they rust on the inside from condensation. Be careful with old compressor tanks . Your repair plans look great !


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## dave_r_1

Excellent way to delay cleaning up.  And you must have a very cool anti-gravity device to hold those parts up like that in your 3rd picture.


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## petcnc

dave_r_1 said:


> you must have a very cool anti-gravity device to hold those parts up like that in your 3rd picture.



He he he
I do have such a device! It's called "white paper all around the object" and Photoshop power

Petros


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## petcnc

Subwayrocket said:


> Just one word of caution. If you dont have a small endoscope , borrow one or cheap one usb one off Amazon. Look up inside the tank, if you plan to use the tank.  I friend of mine had an old compressor burst in his shop. They were hospitalized a few months, both seriously injured and scarred. If it's been sitting a while and/or the last owner didnt drain it often , they rust on the inside from condensation. Be careful with old compressor tanks . Your repair plans look great !



Thanks for the advice. I do not have the original tank. I'm thinking to use an old fire extinguisher as a tank. I'm looking to specs for pressure strength of the tank as I don't want it to blow up and make a mess out of me and the shop!

Petros


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## thomas s

Nice job well done.


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## Ulma Doctor

excellent solution to an interesting problem!
well done!!!


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## petcnc

UPDATE

After testing the unit it proved to be:

a. working more silently compared to the monoblock 2HP one I have
b. Smaller and easier maneuverable
c. provide a medium air supply and pressure, adequate for my small shop
I decided to add a pressure switch and some sort of air tank to it to make it more like an air compressor.

Two old 10 lt. fire extinguishers were used as air tanks 




As my first effort to stick weld a 20 lt extinguisher created small holes in each welding spot I decided to clamp the pair instead of welding them to the base.




I used a stainless flexible metal hose to provide some cooling to the pressurized air before it enters the air tanks.




A small expansion chamber that collects humidity (water) that can be drained through a small screw at the bottom was also used.




And I have a silent small air compressor to use for small jobs.




Thanks for reading.

Petros


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## Ulma Doctor

very cool!


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## Eddyde

Nice job, I like the idea of recycling the extinguisher tanks, did you add condensate drain valves on them as well?


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## petcnc

Eddyde said:


> Nice job, I like the idea of recycling the extinguisher tanks, did you add condensate drain valves on them as well?



It is on the "To Do" list.


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## markba633csi

I like your improvised plumbing fittings Petros- Great scrounging! 
Mark


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## petcnc

markba633csi said:


> I like your improvised plumbing fittings Petros- Great scrounging!
> Mark



Mark you know what they say about necessity...


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## markba633csi

Yes I know very well, and I imagine you don't have hardware stores in the abundance we have here
M


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## petcnc

markba633csi said:


> Yes I know very well, and I imagine you don't have hardware stores in the abundance we have here
> M



We do have some big general hardware stores, (thats how I acquire all that funny stuff) but they are not specialized in engineering and as I usually make most of my projects at weekend evenings they are closed!


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## dulltool17

Excellent work!
Ef Haristo!


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