So I built an air compressor

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I did it, but man what a time it was.
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A couple years ago I got my shop done, 30x40 metal frame on concrete slab, metal siding and spray insulation. After getting things moved in, I had a strong hankering for a new bigger air compressor. My then current 20gal oil less was bought about '95. My desire was a 60 gallon or larger and plumbing it through the shop.

I started looking, hoping to find a good deal or a good used unit. I found several that needed repair of some sort mostly motors. Also found a couple that the motor worked but wouldn't build pressure. That started me looking for replacement parts and figuring costs.

That lead me to a website with factory replacement parts. They were pricey, and it made the overall costs not worth it. But I found one listing for an 80 gallon tank with the mounting shelf for the motor and compressor for $135. And the website offered free shipping with a purchase over $100. I called to make sure price was correct, they said yes and I ordered it.
I had already looked at horrible freight pumps, and read lots of mixed reviews. But I had started with the intention of "trying to save money". I bought a 5hp compressor pump.
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5hp, 15.2cfm@90psi, 17.3cfm@40psi. I take those ratings with a large grain of salt.

So now I have a tank and pump and in in this for about $300 total. Looking for a motor led me to a used Baldor 5hp farm duty for $20. Turned out to be shorted. I took it to a friend who has a motor shop and he basically traded my shorted Baldor 187 frame motor for a WEG 5hp 187frame that was "new". It was brand new with a bad capacitor. Yes he's a good friend.
Of course I had to buy all the fittings and such. Compressor Source online was awesome. I added a mag switch, large pressure dial, and hour meter. I wanted to be able to say how long this compressor was actually running when people ask me about horror freight.
I extended the intakes to help with noise. I also decided to add a moisture reducer/cooler. I decided to make the (in)famous "Franzinator".

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I had read that a single Franzinator was about right for about 1-2hp compressor. Since I had the material I made a bank of 3. Each one is per the instructions I could find from Franz himself on other forums from years ago. Mine are all welded from sprinkler pipe and capped with half-round fence post caps.

After building I hooked each one up to a hydrostatic tester and tested them to 250psi. They passed holding 100psi more than the compressor is capable of.
Hardest part was plumbing. The fitting on the HF pump isn't standard. I found a video online that said it was British Straight Pipe thread. I ordered a 3/4" BST to 3/4" NPT and everything is great.
The air is plumbed from the pump cylinders to a manifold where it flows through the 3 Franzinators in parallel. Air then exits into another manifold which then feeds into the 80 gallon tank. I put the one-way check valve just before the manifold going into the Franzinators. When the motor cuts off pressure is drained off the cylinders and a short section of pipe.

The tank was black from the factory, as was the pump and motor. I added the logo and color.

All total I'm into this for about $700.

Now, I said when I started I wouldn't advise anyone to do this. That's not because I'm not happy with what I have. Rather it's because it has taken me over a year to get this done. Chasing parts, finding motors, getting repairs made.....looking back I think that spending the money upfront and getting a working unit new would have been much faster and easier.

By all accounts I've seen the HF compressor pumps either don't work from the start, or if they do work they seem to work well and for a long time. This one works, so I'm cautiously optimistic.

Hope some find it interesting. If you are a glutton for punishment or have way more time than money building might be for you.
 
Looks spiffy- does extending the intake filters really reduce the noise? I'm wondering if one big filter would be
better than two smaller ones?
 
Looks spiffy- does extending the intake filters really reduce the noise? I'm wondering if one big filter would be
better than two smaller ones?
yes!
When I got it assembled and was 'running it in' for 30 minutes with no connections at first I had nothing screwed in to the intake port. I noticed very fast how incredibly loud it was. I quickly screwed in the filters and that helped a bit but it was still loud. I had heard that these larger oil-lubed compressors were quieter than my oiless but I'm not sure this one was much quieter. Then I added the extensions. As I understand it making 90* turns helps most. This helped quite a bit. It was very noticeable.
 
Looks great.

What was the website for the tank? I already have everything but the tank. My 40+ year old compressor actually does not have a lot of hours but the tank being 40+ years old and always has a lot of rust in the drain water is quickly losing my trust. The tank I have now is a 20 gallon but I would put the same mechanics on a 40 to 60 gallon.
 
Looks great.

What was the website for the tank? I already have everything but the tank. My 40+ year old compressor actually does not have a lot of hours but the tank being 40+ years old and always has a lot of rust in the drain water is quickly losing my trust. The tank I have now is a 20 gallon but I would put the same mechanics on a 40 to 60 gallon.
They changed the price, I was gonna buy another after I received this one but they fixed it. The tank I bought for $130 ish is now $400 or more.

 
yes!
When I got it assembled and was 'running it in' for 30 minutes with no connections at first I had nothing screwed in to the intake port. I noticed very fast how incredibly loud it was. I quickly screwed in the filters and that helped a bit but it was still loud. I had heard that these larger oil-lubed compressors were quieter than my oiless but I'm not sure this one was much quieter. Then I added the extensions. As I understand it making 90* turns helps most. This helped quite a bit. It was very noticeable.
The largest noise source on that compressor is (as you've found) the intake ports. If it is still too noisy for your taste with the the filters installed, you can try this. I found it to be further improvement over just the filters.

I attached reinforced rubber vacuum hoses to the intakes, ran the hoses into the lid of a 5 gallon bucket. The bucket also has two holes for the filters. 4 holes total.

My pseudoscientific explanation for why this helps is two-fold.
#1 is similar to how scavenging works on a 2-stroke exhaust (or maybe inverse of how that works). Pressure waves from the two cylinders sharing one intake chamber somewhat cancel each other out.
#2 is that those pressure waves which are not cancelled out, are somewhat contained and absorbed by the plastic bucket and rubber plumbing. They act as "shock absorbers" for pressure waves that arrest them before they become sound waves in my shop.

It's not silent, but it's way better.
 
Adding a small automotive muffler to the intake also helps a lot with noise.
 
I used the air cleaner off I believe a 350 Chevy. World of difference.

Greg
 
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