12V Air Compressor mods

[corax]

A more in-depth look at cheap 12V air compressor quality and modifications - Cross Posted with permission from "terryj5" from another forum

First, all this stuff is about a 3 year old Harbor Freight and a new (Jan) Master Flow 1050 Tsunami. The MF1050 has quite a few similar variants. The HF unit seems to have undergone some slight changes thru the years. It's just little stuff so the following mods should still apply, maybe with a tad of adjustment.

Long story short, the best mods, (if you have any kind of other life) is to re-wire the thing and open up the ports. Everything else I did had minimal performance gains other than longevity.
I would not recomend these things for any more than filling tires as performance drops off rapidly over 40psi. They will go to 150 and beyond but at great cost in time and risk of melting the Polar Icecap.

Testing was done as follows: 4900' elevation, room temp (68 deg or so), powered from running truck/Optima, filling a 3.5 gal tank from 0-105psi and the most useful 0-40psi.
3 stages of development were tested in this manner, stock, with wiring and porting, and finally with "the works".

Results: 0-40psi Stock 56 seconds, with wire and porting 42 sec, all mods 37 sec.
Results: 0-105psi Stk 3min 38 sec, W+P 3min 21 sec, all mods 3 min 15 sec.

This shows that most of the gains were in the "tire inflation" zone. If you want to keep a decent size tank filled and use air tools, these things are not the answer. Get a $200 Puma, divorce the tank, pump, and controls, and be done.
On the 1050 I run an 85psi on, 105psi off Viar pressure switch #90101. This allows the use of a 10' power cable and a coiled hose/standard fittings without having to manually turn the thing on and off all the time while I check the tire pressure. Just pull off the tire chuck, the compressor pressurizes the hose to 105psi (in about 2 sec) and shuts off.

So in a crude play by play, here it goes:
Steps may not be in chronological order.

14g stock wire and 12g "Low Voltage Underground Landscape Lighting Wire" sold by the foot here at Lowes @ $0.56/foot


Lose the fuse holder and replace with a quality one or better yet a $4 30a ckt breaker. Check all connections and re-solder any thing that looks weak. I was able to cram it all inside including the breaker. The relay will want to short against the end cap of the motor. I arranged the wires to lay between the two.


The surfaced head showing the opened up intake and exhaust. I left a thin web of material on the intake to help support the reed because later I intended to make a lighter thinner and flatter one from feeler gauge stock. The exhaust seals against an o-ring and sealed pretty good. Look how crude the .006" stock reed looks compared to the .003" one. Red loctite on the reed screws is good. The intake provided by far the biggest gain of the two.


Head with beautiful new reed.


Intake and exhaust drilled and tapped to accept 1/4" NPT manifolding and fittings, "color matched" of course. Drill out any pipe fittings used on the intake side to the id of the 1/4" pipe, makes a difference.


This is a HF unit with the head jacked up showing the piston with its dual (riveted in place) intake reeds. I'm working on porting that baby now


After testing the thing worked great but the 1050 motor would not restart against a head of any more than 30psi. It just buzzed and made the cables get real hot. Apart came the motor. The plastic brush holder was warped due to the thermal cut out switch being jammed underneath. Thats how they built it. That put the brushes at an angle to the commutator, not good. I put the 1050 motor away for now and planned to swap in the HF motor.


The HF motor suffered from the same thing and the armature was different leaving 2/3 of the brush hanging out over the end of the commutator. The solution was to install 5/16" stand offs under the holder and add two more mounting bolts to draw the holder parallel to the motor end plate.


The 3 year old brushes had scorred the commutator so on to the baby lathe to make it like new.


At this point, well, a picture is worth a thousand words. What a mess.


About half way done now but CSI is on, so I will finish this up tomorrow.

[corax]

A more in-depth look at cheap 12V air compressor quality and modifications - Cross Posted with permission from "terryj5" from another forum

At this point the differences between the 1050 and the HF really started to add up. Although from a distance things like the castings look identical, they are not. The HF motor makes the 1050 look like a toy. It has stronger magnets, better ball bearings, the armature had nice tight windings, there were the proper high dielectric insulators on the armature polls, a .1uf capacitor accross the motor leads (cuts down arcing of the brushes) and the can was some kind of seamless tube that had been finished up on a lathe.
I really think that both units are attempts to "use up" not to spec electric motor parts purchased at pennies on the $.
The bore and stroke are the same and the pistons are interchangeable.
In both units the crank throw was not inline with the cylinder. This caused a good bit of binding of the piston/cylinder on the 1050. It took 5/32" spacers between the motor (HF) and crankcase (1050) to get it right.
Finally, the HF heat sink was a sung interference fit with the cylinder sleeve while the 1050 had 4 little bosses only allowing minimal contact. The 1050 heat sink is mostly to hold the head up. I used the HF heat sink in the "Frankencompressor". After proper painting and yes, the tips of the fins have been wet sanded to bright metal. Alert the Mall!


The final hybrid


And another


The test rig


One final observation. From to about 0-35psi these things really shine. Above that they just don't have the displacement to be of much good. I have read posts that claim 2.5 cfm @90psi, it just ain't so. I would respectfully question the accuracy and method of their testing.
One more thing, I promise it's the last one, I just ran a 0-30 test and it only took 24 seconds.

[corax]

A more in-depth look at cheap 12V air compressor quality and modifications - Cross Posted with permission from "terryj5" from another forum

- Both reeds on the 1050, the one I used, are fastened with about a #4 sheetmetal screw, a very short one. I was careful not to strip it but if it happened the hole could easily be tapped for a 4-40 or so machine screw. In any case use red Loctite.

- I simply enlarged the ports and dressed off any sharp edges. I just surfaced the inside of the head so it was as flat as possible. The exh port can only go so big as you must leave some "meat" to retain the o-ring. It will be obvious (1/4" or so). The intake, the real money maker, is just a freeform mini rat tail file job leaving about 3/32" or so around the edge for the reed to seat on. I think I roughly increased the the area by half. I must repeat, the stock intake reed was bent and very crudely cut. It could not have sealed very well.

- On mine, I tapped/plugged the front hole in the crank case and drilled a new one on the side simply for compactness. I started with 1/8" fittings and noticed that if I unscrewed the fitting while it was running the thing picked up several notes in rpm. Once drilled out to 1/4"npt there is no difference when the fitting is removed, indicating all restriction was gone. If you use 1/4" stuff make sure to look inside the fittings. They typicly have a much smaller id than the plain old pipe. Just drill out the fittings to the id of 1/4" npt pipe.

- The "touch it with finger" test suggests good results. Lose the square shield around the motor. It is there for those folks that like to pour hot McDonalds coffee in their laps and then sue. The thermal cut off switch was marked 75 deg C. I tossed it out. If the motor (not the comp or fittings) is to hot to touch, turn it off.

Grab yourself a 4mm Allen wrench and pop off the head and see whats going on in yours.

[troyboy162]

awesome post! very good info in there. thank you very much

[CJM]

FWIW I got noticeable performance from just removing the crappy metric connector and put a standard one on. Blows my tires up really well, but the downside is I dont regulate it at all, thus you gotta pay carefull attn to using it so you dont blow it.

So long as its filling its fine, once you take it off the pressures shoot to insane amts (I had it up to about 180psi). Due tot he extreme pressures I JB welded on the fittings after one of them blew off the one compressor.

FWIW these things are super cheap and work well for what they are, if I wanted to get a real compressor I would buy a puma 12v and be done with it. They run about 200 bucks and put out way more power than anyone might need. The downside is size and they have an airtank. Also they draw more juice so good wiring is a must, we have ones made by puma in all of our work trucks, you can air up from 0-about 50psi in under a minute.

[Erich_870]

First thing, very cool write up!

Second, that bably lathe is AWESOME!

The 3 year old brushes had scorred the commutator so on to the baby lathe to make it like new.

Third, if you think your work shop is messy, please swing by my place and give me a hand. Your set up makes me

At this point, well, a picture is worth a thousand words. What a mess.

Erich

[corax]

First thing, very cool write up!

Second, that bably lathe is AWESOME!

Third, if you think your work shop is messy, please swing by my place and give me a hand. Your set up makes me

Erich

That's what I said about the baby lathe, unfotunately none of it is mine - all pics and the write-up are from terryj5

[Erich_870]

That's what I said about the baby lathe, unfotunately none of it is mine - all pics and the write-up are from terryj5

Oh, hahaha, foot-in-mouth

Erich

[Seanz0rz]

im going to go ahead and bump this thread, even though its kind of old, as it pertains to a few questions i have.

has anyone here done this? i have mine disassembled on the table, but im wearly of hacking away at metal where the oring is