You asked for it.
This write up was done about 5 years ago. I now have CO2 but find myself still using this thing because it is small and light.
These days there are quite a few other affordable options out there.
HERE WE GO
First, all this stuff is about a 3 year old Harbor Freight
and a new (Jan 09) Master Flow 1050 Tsunami. The MF1050 has quite a few similar variants. The current HF unit is not worth fooling with.
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 recommend these things for any more than filling up to 33" 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, stock 3min 38 sec, with wire and porting 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, controls, and be done.
On the 1050 I run an 85psi on, 105psi off Viar pressure switch. 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.
Here is the play by play.
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
Ditch 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 the end bell 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 ports. I left a thin web of material to help support a lighter thinner and flatter intake reed valve made from .003 feeler gauge stock. Look how crude the .006" stock reed looks compared to the .003" gauge stock. Looks like it was cut from a tin can with snips. 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 ports on the outer part of the head 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" piping
, 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. I found the plastic brush holder warped due to the thermal cut out switch being jammed underneath. That’s 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 (bent brush holder) 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 thermal cut out switch was ditched in favor of the "feel it and see if it's hot" method.
The 3 year old brushes had scored the commutator so on to the baby lathe for a re-cut, like new.
At this point, a picture is worth a thousand words, what a mess.
At this point the differences between the 1050 and the HF were really adding 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 across 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.
The bore and stroke of both 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 light interference fit with the cylinder sleeve and had 360 degree contact while the 1050 (left) had 4 little bosses only allowing minimal contact. The 1050 heat sink is mostly just there to hold the head up. I used the HF heat sink in the "Frankencompressor".
The final hybrid after proper painting, addition of a check valve and yes, the tips of the fins have been wet sanded to bright metal. Alert the Mall!
The test rig
One final observation. From to about 0-35psi these things really shine for the money. 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 isn’t so. I would respectfully question the accuracy and method of their testing.
One more thing, I promise it's the last one, I ran a 0-30 psi test and it only took 24 seconds.