Mrodair Airmax Compressor Review: Prep, Poor Build Quality, Fixes, Ultimately Unsafe for Use
For those working on their MrodAir Airmax Extreme compressor, this thread is both a resource and report of my own experience. Work on my compressor evolved over time. Initially, the focus was preparing the compressor for a longer life, easier maintenance scheduling, and safer operation. As issues were discovered, this devolved into troubleshooting, fixes, and currently finding my compressor unsafe to use until an oil-in-air problem fix is found at Mrodair.
You can follow my journey beginning in October last year http://www.talonairgun.com/forum/viewtopic.php?f=52&t=33430
This thread is that Guinea Pig thread’s more useful successor.
The first few posts in this thread cover major topics. The major topic posts continually undergo editing to keep information up to date. They do not attempt to preserve chronology. Posts after the major topics are chronologic, just as in any normal thread.
NB. Changes in the major topic posts are not flagged as new by the BBS system.
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Disclaimer: Material presented here may be incomplete or inaccurate.
Work you undertake on a compressor is expressly at your own risk.
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Introduction
I pre-ordered my Airmax compressor from MrodAir after watching their product introduction video and reading the website. My impression was that the compressor would be a mid-priced, mid-performance machine suitable for my limited, single shooter needs. The promise that a US outfit would be going over the units and making sure they worked was reassuring. With its advertised “silicon bronze rings”, “3 cylinders”, and real pistons, this seemed a happy medium between an o-ring based compressor and the “overkill” of a dive compressor.
We were reassured by MrodAir that each unit would be tested and that they had arranged many upgrades. These compressors would be long lasting, “real deal” compressors. As an airgun newbie, I was unfamiliar with MrodAir. There were some negative online reviews, but I also know that online reviews often trend towards the negative – even unfairly. I took a chance, ordered a compressor, and promised to report my experience on this forum.
My desire was a compressor that would let me fill or top up a tank reliably. I was only a single shooter, but the convenience of ready air was enticing. Also, the ability to use high air consuming items, like regulator testers, made a compressor/tank combo a nice step up from hand pumping.
My experience has not been consistent with a ready to go, fully developed product. Others have fared both better and worse than I. There are issues potential buyers should know before purchase.
False Advertising
There were factual inaccuracies in the product advertising at MrodAir. These incorrect details affected my decision to place an order. Had they been accurate, I might not have placed an order.
As described on the product page when I ordered the machine…
No, this is a TWO stage compressor. Only two cylinders do actual compression. Although the 2nd stage piston rides atop a carrier piston, that carrier piston does zero compression work. It is drilled through and lacks air inlet or outlet. It is simply not a compression cylinder. The compressor can still achieve 4500 psi by making the two stages work harder, but the 3 cylinder count is a factual error. I am only counting cylinders that perform compression. Otherwise, one could lash a six-pack of beer to the compressor and dub it a 9 cylinder compressor. Two cylinders means each must do more work than in a three stage machine. There is also less chance for interstage cooling of the compressed air.
Silicon bronze piston rings were prominently mentioned as a feature of the compressor. This gave the impression that rebuild intervals would be consistent with that of metal piston rings. I was surprised to find my 2nd stage piston rings were not metallic. The rings resisting the greatest heat and pressure, are polymer
Several other owners confirmed that the high pressure cylinder rings. I informed MrodAir and the initial reaction was that I was wrong. Their website continued to advertise these compressors as having silicon bronze rings for several days more.
Piston ring description was adjusted as of 4/22/2016. The high pressure rings are now described as silicon bronze suspended in phenolic resin and the low pressure rings as traditional cast iron. The number of cylinders advertised remains three.
Because the 2nd stage rings are now known to be a less durable material than silicon bronze, having replacements is even more important. The high pressure rings look like angle cut wear rings. They are soft and easily indent with a fingernail. Heat, flame and smell testing of one from my compressor makes me think these are actually silicon bronze filled PTFE wear rings. I would like to find a second source. I have yet to find a source for bronze filled phenolic resin rings, but silicon bronze filled PTFE wear rings do exist.
Durability and duty cycle should be scaled back in your mind. Filling a 88 cf tank in one session stresses the compressor to its limit. A reasonable expectation would be to top off a tank once in a while or fill a gun directly. Long term torture testing suggests 20 minute max run times. http://www.gatewaytoairguns.org/GTA/index.php?topic=107945.0
Technically, the compressors are 120 volt units, but they need a 30 amp service outlet to run properly. A 20 amp circuit is insufficient. My own unit draws about 24-27 amps during operation. It is simply too large a current draw to safely run on a 20 amp circuit. Perhaps one could get away with it for filling a gun directly, but topping or filling a tank is asking a lot of a 20 amp circuit.
Electrical Hazard
My unit arrived with two major electrical components (relay and contactor) hanging loose. Each was held in place only by the wires connected to them. A consumer who receives the machine reasonably expects safe and secure wiring. If your unit arrives in the state mine did, disaster will happen in short order.
The compressor is not grounded. Grounding pin of its AC power socket is connected to ….. nothing. This machine has a semi-open, metal frame, uses water for cooling, and is not grounded.
An under capacity 15 amp IEC receptacle connects the AC power cord to the compressor. The IEC connector is only 15 amp rated, well below the actual current draw of the compressor. The IEC power connector can overheat or starve the machine of adequate power.
Electrical wring skills can correct these shortcomings. It is doable, but for a vetted design and build, the average buyer should not need to do electrical rework.
Air Quality with Heavy Oil Contamination, (Critical Go/No Go Safety Item)
My unit, and that of some other owners, continually passes oil from the crankcase into the low pressure cylinder. Oil that gets into the air path oxidizes (maybe even diesels) at the high pressure cylinder, fouling that cylinder’s rings and valves. The remaining oil goes on to the water separator and MUST be filtered out before it reaches a gun or tank. A little oil is not uncommon for a compressor, but it must be removed with a filter before it gets into your tank or gun. My unit splatters oil all about in the low pressure cylinder. Bleeding the separator filled my garage with suspended oil vapor. Not all units have this problem. Mine does and so do some other owner’s. This is distinct from being shipped with oil in the crankcase. It’s actively putting more oil into the cylinder with each stroke.
This oiling issue should be tested before one puts the compressor into use. An affected compressor will still fill a tank. Merely testing whether the compressor will fill a tank is insufficient. You should disconnect the air output of the 1st stage and specifically check for continued oil output before you try a pressurized run. Without my large, Alpha filter, this would have been an oil in the tank disaster. With my Alpha, it is still a problem. A filter can only handle do so much. Filters are meant to deal with the the last traces of oil, not heavy contamination. Oil in your high pressure air system is an explosion hazard and may negatively affect seals in your guns.
Summary
There are indeed MrodAir upgrades like the automatic cutoff gauge and radiator. Those are useful, but one needs to go over these units carefully before use. Expect to do electrical and mechanical work to keep them running. Mine, as delivered, was neither turnkey nor ready to use. Ultimately, mine had such severe oil contamination issues that it was unusable and no fix was forthcoming from Mrodair. On the up side, the compressor is easy to tear down and work upon. If good parts were available, and fixes developed, one could conceivably keep a unit running until one could afford a more robust solution. Just anticipate needing your mechanical and electrical skills.
The compressor does fill fast – perhaps too fast for its own good, Takes about 80-90 minutes to fill a Great White from empty to 4500 that’s with frequent bleeding. It’s just a tad over 1 CFM. You can actually see the pressure gauge of a Great White move as the compressor works. However, there are reliability, longevity, duty cycle, and oil contamination issues that need working through. I never got mine sorted after months of patient work.
My story follows. You will learn about initial inspection, electrical, air leaks, oil in air contamination, and blowouts. There is even a down trodden me “throwing in the towel” and ready to scrap the machine after first discovering heavy oil contamination and suffering another o-ring blowout while filling a tank.
I think one might get this compressor to marginally work directly filling a gun or a small cylinder, but expect very slow to no customer support if you encounter real issues. This is a machine built to the barest margins possible to still run. It has no pressure safety releases and should not be run more than 15 – 20 minutes at a time. You need electrical and mechanical skills to keep things in good order. This is of course, if you get a good unit in the first place. Test thoroughly when it arrives. You are the factory’s last quality control step.
Guy
Main Topic Posts Index
30 amp 120 volt RV service outlet Installation.
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357139
Delivered Components
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357140
Initial Inspection
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357141
inspection of cylinders for oil seepage during shipment
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357142
Opening Crank Case for Complete Oil Change (No, not for routine changes!)
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357143
Electrical Fixes and Upgrades
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357145
High Pressure Valve and Water Separator
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357146
Automatic Pressure Switch Gauge Glycerin
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357147
Water Cooling System
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635#p357148
Piston and Piston Ring Measurements
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635&start=60#p359151
O-ring Sizes
http://www.talonairgun.com/forum/viewtopic.php?f=52&t=34635&start=40#p358769
Latest changes
5/21/2016
No Mrodair fix for the oil in air contamination issues. Lower pressure cylinder consumes oil severely. Small engine shop evaluation suggested piston and cylinder tolerance are too large to ever effect a seal. Without a way to fix that problem, the compressor is unsafe to use. My unit is now going to another victim/owner for use as a parts donor.
If you are contemplating this compressor… my painfully earned advice is to buy from a different dealer and get a Shoebox or save up for a full scale dive compressor. The Mrodair Airmax Extreme compressor is a poor quality product you will most likely regret.
All Replies
I requested spare parts, this is Mrodair’s response. Looks like we will be getting better parts soon.
Brian,
We are putting together a kit with much more than just the rings.
Gaskets, poppet valves, reed valve and other small parts.
These are currently in route to us from the OEM manufacturer.
We will have them listed on the website soon.
They land in the seaport this Friday.
We want to make sure to have plenty of parts and support for these new compressors.
Check back with us late next week and I will get you a set.
Thanks
We Are Mrodair
For 1300$ I would start to reconsider spending some more and getting a used scuba compressor…
Yep. $1300 with the Mrodair upgrade package + shipping + my own upgrade parts + cart + alpha filter —> closer to $2K
All based on believing the base machine would function correctly. 😡 My bad. I should have verified the compressor’s baseline function was OK before adding all the goodies. Then again, I knew the machine had already been checked out in Arkansas.
Add I’m 30+ hours into working on the machine and documenting things here.
BTW, I didn’t notice any obvious crosshatching in my low pressure cylinder. Just linear stuff parallel to the cylinder axis. It has under 2 hours of run time. Would they have already worn away seating in the rings in? I wonder if there was any crosshatching to begin with?
Should have looked specifically for crosshatching at the bottom half of the cylinder when I had it apart.
Marko
I think most got had for closer to $1300…..you know “upgrades”
I’ll have to defer to someone who know about pistons and rings. For an HPA compressor, I’d like to have very little oil blow by.
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Off topic, but re the Alpha filter…..
If you ever want to fill a gun directly from an Alpha filter, be sure to let Joe know you also need a 2nd bleed valve at the top (after output). Without a bleed valve AFTER the alpha, your fill whip won’t bleed down to zero. The bleed valve for the Alpha filter is on the compressor side of the pressure maintaining valve. The PMV won’t let the output bleed backwards all the way down. That’s fine on tanks because the tank end has a bleed. On a gun you don’t have a bleed valve. Hence the need for a 2nd bleed valve with the Alpha. Don’t complain about the PMV, that feature makes the alpha a better filter and makes your water separator more efficient.
This is bullshit, how can twice the ring gap be on the high side of normal?
What happens to flow when you double the surface area, did it go up in square of the area, can’t remember. But it does the same to blow by of oil. And it is not normal to have ring gap that far out of tolerance. And it’s out of his own tolerance that he gave, not my race engine specs…
I agree with you Doug, it’s build badly and advice against buying this, just trying to help people who already have them to make it work.
I know it’s not Bauer nor coltri, but it should work non the less, it’s cheap compared to big boys, but around a grand is not that cheap that it couldn’t work. Just my 2C
Marko
WOW very happy to hear he is doing something on this. I sent a email requesting extra parts Sat. since they are not on his web site. I will make do cleaning my units filters every 1k psi for now. But I am going to order a Alpha filter this week.
Heard from Michael today. He is working on the compressor issues based on the note. With his permission, I copy it here…
Got your high side parts out.
Been working with several compressor manufacturers on this.
So far, seems to be selective problem, but need to address it to avoid problems later on.
I have 3 different types of rings coming.
Chrome plated for two Trowe application.
1mm thick to run two in each groove with offset gap.
Square scarf cut Teflon
Two of the compressor makers seem to think it is more to do with the reed valve being too stiff and creating vacuume for too much of the piston travel on the down stroke and too large transition hole in the reed plate.
I sent a drawing to a laser cutter to make us up some of these in different thickness and making some plates here that have smaller transition.
From what I have seen, this seems the most plausable as vacuume would pull oil into the cylinder.
Your ring gap, is on the high side of normal, but not crazy.
.004 per inch is std and .0065 is high pressure/heat application for cast rings.
The chrome moly rings can be gapped less and scarf cut really have no gap.
Just wanting to cover all the bases.
I’ll let you know when they arrive.
We Are Mrodair
“Stay Tuned”
Michael Esch
Mrodair.com LLC
115 Main St
That’s just what this is, a shop compressor redesigned for something else.
I have started a similar project over a year back, I work on it when there’s nothing better to do. The Chinese cheapo v twin compressors work years on end in hobbyists garages. So using smaller pistons with similar workload on hpa is plausible, but tolerances are much more precise than these mrodair ones.
Marko
I said it awhile ago that this thing was never designed for what is asked of it. Even if the rings are fixed is that going to be the end of problems. Seems like all the o ring grooves to o ring size are out of tolerance.
The way I see it there are 2 options for compressors. Shoebox for someone who doesn’t shoot a lot and a real compressor for those that use more air.
At least I’m helping out fellow air gunners understand how this thing is put together, where the weak points are, and how to address some of them. Unfortunately, that’s not going to make me a popular name or priority in AR.
You should be his new best friend, all this R&D work he is basically getting for FREE if the compressor actually ends up working from your work.
Thanks, Marko. Nice having someone who knows about these things helping to evaluate the situation.
I’ll wait a few more days and see if there is tangible customer support from MrodAir. If not, we will know where potential buyers are headed, and we can all close the chapter on the Airmax Extreme compressor as a viable product.
Like WalkonKing, I want to be safely filling and shooting, not doing compressor R&D and rebuilds.
[EDIT] Hurrah! We’ve got word from Mrodair!
Don’t think the rods or crank will be the problem, same stuff with every cheap shop compressor, just about the same workload on the crank and rods with the 10mm hpa piston as 10bar on 45mm regular piston.
That’s just what this is, a shop compressor redesigned for something else.
I have started a similar project over a year back, I work on it when there’s nothing better to do. The Chinese cheapo v twin compressors work years on end in hobbyists garages. So using smaller pistons with similar workload on hpa is plausible, but tolerances are much more precise than these mrodair ones.
Marko
Oh man I am so sorry you guys have to deal with this on a brand new compressor.
For those who want to fill and not be a compressor mechanic, it might be time to look into Nitrogen gas tank rental with a regualtor to fill your tanks.
Far less expensive and much safer.
I wonder if this is just the beginning? You fix this problem and then what’s next? Rods, crank shaft.
Would be different if they we’re failing 6 months or a year down the road after they have some hours on them. These things are failing straight out of the box.
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Listed on website for sale?
Hopefully all the o ring grooves can be matched with a proper size o rings or failures won’t stop.