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Mrodair Airmax Compressor Review: Prep, Poor Build Quality, Fixes, Ultimately Unsafe for Use

Home Forums General Compressors, tanks and pumps Mrodair Airmax Compressor Review: Prep, Poor Build Quality, Fixes, Ultimately Unsafe for Use

Viewing 15 posts - 16 through 30 (of 268 total)
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    Did first pressurized runs done today after new water pump arrived. I’ll post more details about minor, easily fixed issues later, but first I have a question for the forum members.

    Should I use this just to fill my ONE Vulcan directly or use it to fill my Great White?

    The compressor used in combination with my Joe Brancato air dryer very quickly fills my Vulcan. Without any doubt, it can do that job easily and without much strain on the machine. I didn’t do formal timing, but topping my Vulcan from 130 to 250 bar (3600 psi) was so fast that I worried about overshooting the Vulcan’s max pressure. It’s that quick. For filling an air rifle directly, the air volume, run time, and demands for air drying are easily met. I’m shooting, maybe two fills/week tops.

    At that low volume and limited max pressure, this compressor is barely stressed and less likely to break down.

    BUT…. I also have a brand new Great White tank that I originally purchased to go with this compressor. I could fill the tank and gain the convenience of not going to the garage for a fill. Wow… a whole 50 feet of walking saved. A tank indoors is nice and quiet. On the other hand, this means stressing the compressor with 4500 psi pressure and extended run times. I’ve gone through the machine to address weaknesses. It will probably be okay, but a tank multiplies the moisture removal problem.

    I don’t know a good way to check whether or not moisture got into a Great White.
    I am admittedly a little scared about a 4500 psi tank corroding and being a death trap.

    Right now, my Great White is pristine, having never been filled. It could easily move on to a new home if I decide against using it. Once I fill it, it’s no longer “as new”.

    What would you guys do?

    1. Just use it to fill directly (good)

    2. Fill the Great White (better)


    People want to fill tanks so they can travel and hunt

    So fill that tanks up!


    The great white is carbon fiber,so no corrosion . Put the tank in water ,less heat build up.


    Talked to Joe Brancato about the Great White tank’s construction. The tank has an inner aluminum liner surrounded by a carbon fiber overwrap. The aluminum liner forms the seal. The carbon fiber withstands the pressure. He also verified that venting the tank “upside down” (valve down) would bleed out fluid in the tank.

    So, yes, a Great White could corrode if water were inside the tank.

    BTW, if you fill a gun directly from Joe’s air dryer, you also need a bleed valve AFTER the dryer. The pressure maintaining valve won’t let the hose completely bleed down. This isn’t an issue when filling a tank (with their own bleed valve), but it is a problem if you are filling just a gun. He can source an additional bleed valve for post the dryer. I’m getting an extra bleeder to give me full flexibility.

    I have decided to go ahead and fill my tank. It will only be fed air that has gone through Brancato’s air dryer and I will recheck by venting the tank after a cooling period.

    Next step is devising a water jacket to cool the compressor’s air outlet pipe. That gets super hot with the near adiabatic compression. If I can draw off more heat before the compressed air hits the water separator, more water will condense out. The separator will do a better job. The compressor has a water cooling system anyways. May as well take advantage of it.


    [EDIT: I was really badly discouraged by oil contamination and a blown out o-ring when I wrote the below. Some more time later, I’m resuming work on the machine and there may yet be hope for getting the oil problem under control. I’m leaving the below largely intact because it conveys how I felt it after so much work. With repositioned piston rings and “under filling” the crank case, the oiling issue might be soluble. There are mixed reports regarding degree of oil contaminating the air. Hopefully, I can get this unit to become one that isn’t such a bad oiling unit.

    I’m pronouncing the machine. While I can get it and running (again), I don’t think I’m putting in any more effort on this compressor.

    The Great White filling trial uncovered enough issues that I won’t be using the compressor for filling a gun let alone a tank.

    Far too much oil gets pushed through the air. While the water separator followed by JB’s air filter clears it out, it’s simply too much for me to tolerate. I had to vent the garage because each venting cycle was filing the air with suspended oil. There is nothing II can do to the machine to stop this from happening.
    Speed was great. Took about 80 minutes to reach 4100 in the Great White. That is with bleeding the separator and JB filter every 4-5 minutes at beginning. Every three or so near end.

    Had dramatic filling of air into water cooling system when 4100 psi was reached. The o-ring separating the high pressure cylinder from the water jacket had blown out. That ring is right around the high pressure inlet wafer valve. Mechanically, I don’t like that type of seal in such a high temperature and pressure location. It’s going to be prone to repeated failure even if I replace the o-ring.

    Lot of carbon buildup on the high pressure rings even with just 80 minutes of run time.

    Air in tank post the JB filter is without odor of oil and no water vapor release with venting in inverted position. The JB dryer goes its job!

    I started this experiment knowing it might not work out. I’m lucky that I can scrap the machine and move on.
    I did the experiment, so you don’t have to.

    Yes, I still think it can fill just a gun, but I would not be relying on this for repeated filling of big tanks.
    Filtering works for improving its final air quality, but you have to vent during filling to bleed out moisture. That aerosolizes a lot of oil with each bleed. I can get the compressor running, but like I said, I can’t stop it from putting out all that oil mist.
    Because of this issue, I’m not going to get it up and running again for just filling my Vulcan.
    I want to be able to breath the air in my garage and I doubt the suspended oil vapor is good for my health.


    Edit: Again, I am resuming work on the compressor. I never thought that a pre-checked out unit would have an oiling issue. MrodAir had me open the low pressure cylinder and check the ring clocking, order and orientation. Two of the rings were nearly gap aligned. I have corrected the clocking, but then again I thought rings spin during run time anyways. These are not pinned in place like a 2 stroke engine. I never removed the low pressure cylinder to check the low pressure rings when I did my initial check of the machine. But then, why would one expect to check them?


    Great review and great job upgrading Guy. have you made arrangements with Michael to return the unit for one shipped without oil?


    I’m not one to expect to return or swap out a unit after I have worked on it. If it turns out, I’m actually calling it quits on this machine, it will simply be a loss.

    So, I didn’t write Michael asking for a swap out or return. I merely wrote….


    I’m really badly discouraged after my first pressurized runs yesterday.
    Speed seems normal — about 80 minutes to take a Great White from empty to 4100 psi.
    Temperatures stayed well below 70 c. Power usage actually fell somewhat as pressures went up.

    Problems that really scare me
    1. Large o-ring in high pressure side blew out at 4100. It’s the larger one that surrounds the mounting area of the high pressure inlet valve wafer.
    It seals high pressure air from reaching water. So, Got to 4100 psi and it failed. Suddenly lots of air in cooling system instead of water. Of course, I don’t have a suitable replacement in my stock.

    2. Lots of oil is getting through to the final output. I didn’t notice until about 30 minutes into the filling session. I bled every 4-5 minutes to keep moisture down. It smelled like oil on my hands. Then I noticed that I couldn’t see across my garage as clearly. The air was filled with aerosolized oil. Looked like I had a fire in the garage it was so thick. The oil issue is probably the most serious. I absolutely don’t want to be breathing this during fills and it’s not something I want on my cars.
    Fill of oil was to center of sight port dot. Would underselling solve this or is it simply sucking oil into the cylinders during air intake phase of stroke?

    3. Went ahead and inspected the high pressure rings since I had to take the high pressure side apart to find the blowout. Despite 1.1 hours total run time, there was already a LOT of carbon built up on and between all the rings. Does this portend poorly for time between rebuilds?

    So depressed and on cusp of giving up after all this work.



    Sorry for your loss. I’m glad I didn’t buy one. Mrod needs to man up and and make good to the buyers of this piece of shit.


    I’d like to try one more last ditch effort if I get the o-ring suitably replaced. Final trial will be with less oil in in crank case. I’ll see if filing only to bottom of sighting hole improves the oil pass through situation. If it does reduce the oil issue a good deal, then I’ll keep working to see if I can get this working for me. If the oil situation isn’t improved, it really is time to call it quits. Won’t know until I can source the right o-ring.

    Meanwhile, may as well show some info from the Great White filling attempt.

    Here is the setup nicely on a rolling cart. My submersible pump is in the bucket and moving plenty of water.
    You an see the JB Alpha filter vertically mounted on a stand I added to the cart.

    The short fill whip between the JB Alpha filter and water separator was stolen from my Hill pump. Had to do that because the fill whip included with the compressor has a brass colored quick connect that refuses to hook onto most of my male QC’s. Pushing all the way metal to metal still won’t achieve locking. On the other hand, the female QC’s on my Hill pump whip, and all the hoses from Joe Brancato are stainless steel and easily lock onto all my male fittings. The female QC included with Airmax compressor is so out of spec that I can barely latch it onto my Vulcan fill probe. It won’t latch at all onto the Brancato stainless steel male fittings.

    My power meter, switches and cooling system worked great. Here is some data I gathered during filling the Great White starting from empty. I initially bled every 4-5 minutes and increase the frequency as pressure rose. No need to turn off the compressor during bleeding. Just crack the valve a little and let blow out until no more water sprayed out. My sequence was to bleed the compressor’s water separator first. Then I would bleed the Brancato dryer. I knew I was bleeding on frequently enough because the JB bleed was a LOT less visible water vapor than the compressor’s. Bleeding only required small volumes and the compressor quickly re-pressurized the separator and Alpha filter in a few seconds.

    The filling speed was about that reported by others. I could see the needle slowly moving on the Great White’s gauge during the fill. It was also slow enough the tank only reached about body temperature to the touch. I did take a couple pause of a few minutes to inspect things. You can see those pauses in my data as a temperature drop.

    By about 30 minutes I had a garage full of oil mist and had to ventilate the garage. It looked like smoke was coming out of my garage.

    Then 4100 psi was reached and the high pressure head o-ring blew out. That ended things abruptly. Because I saw air suddenly going into the cooling system, I knew where the blowout was. I opened the high pressure cylinder head expecting to see a destroyed o-ring, but I couldn’t understand what all the thin, black stuff was. It looked like plastic from a shopping bag – super thin. Then I noticed that the o-ring was eroded.

    The o-ring damage is more visible once removed from its seating channel.

    What material, durometer, and dimensions would create the most reliable seal there? I don’t know. It’s subject to both high pressure and temperature. I also think the relatively hard, small water seal o-rings make it harder for the cylinder head to mate metal to metal.


    Even though you did all this work it still failed.

    I wonder what lurks inside the compressors of those who have not checked them?


    While doing more post mortem examination today, I found another surprise. Those “silicon bronze” piston rings aren’t actually metallic. Well most of it isn’t anyways. There is a thin, inner spring steel spring under each high pressure ring. The high pressure rings themselves are some sort of polymer. Real pistons and silicon bronze rings were another reason I thought this compressor would have a longer life span. The sealing/wear element of the high pressure rings are NOT metallic. They are colored to look like bronze, but GEEZ plastic isn’t going to last like the touted metallic rings.
    The ring material even dents with a fingernail.

    EDIT: just to clarify. I checked with a magnet to determine if the steel ring was somehow embedded as part of the new rings. Bronze is not magnetic, but it definitely should conduct electricity. None of my rings conduct electricity per my ohmmeter and some very sharp needle probes. They are polymer.


    Unbelievable !!

    Where has Micheal been? Has he chimed in on any compressor thread lately? I see on the yellow he’s trying to push guns with a buy one get one sale to pay his taxes


    Thanks for all your work on this thread. It is really appreciated and what makes this forum a great resource is the willingness to share.

    As for your compressor, sorry that it ended up the way it did especially after you put so much into it.

    You gave it every chance and went far beyond what you should have to do.


    Thanks. At least the forum gets some info that would otherwise be difficult to obtain.

    Michael thinks the low pressure rings in my compressor are amiss, out of order, upside down, or gaps aligned. I have never taken down the machine far enough to see those rings. Only saw the top of the piston from the cylinder head removal. When I get a chance, I’ll try to get those examined. On the other hand, there really shouldn’t be a need for me to correct them (if they are indeed awry).


    Michael has been in touch and we are considering replacing the entire low pressure assembly. There is support from MrodAir.
    I really would love to have this work.

    The adventure might not be over.

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