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
Bingo!
The Chinese make some of the highest quality products we have ie. Cellphones, TV, computers , but they are not cheap.
Cheap is cheap for a reason
I said it here before , Chinese products will come with a big ? mark on the quality of that product . For them greed is everything
and quality of the product really doesn’t matter . They get paid even if it’s only a few pennies and they get to eat and really do
not give a fuck about anything after the product has been sold . When a dealer sells a Chinese product they buy the product cheap
and then set their own re-selling price generally to get max profit from that item which can be up to a 100% profit on a single unit
sold . The Dealer knows that out of a 100 units that he buys that he will generally have about 5% that will be bad and can live with
that because he already made a bundle from all of his sales totaled . When a Dealer buys a certain amount of a product and 70% of
that product turns out to be fuck-up then it is the customer who in the end is going to get Fucked . There is no way that the Dealer
is going to take that kind of loss . You the buyer are going to eat it in the end , that is why when you think that you are going to get
a quality Chinese product at a bargain price be smart and remember generally you only get the quality that you are willing to pay for .
:3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3: :3:
FROM : THE BIRDMAN
Here is what I meant about buttressing the o-ring. The air filter’s fitting is a prime example of an o-ring channel that is defeated by an over sized o-ring. The o-ring supplied with the filter is monstrously thick. It will never fit completely into the channel. Too large an o-ring means the fitting never attains metal metal closure to buttress the o-ring. This leaves the rubber to resist the force all by itself. Hence, they readily blow out.
The same problem happens with the o-ring supplied on the water separator poppet body. The supplied ring is too large and the fitting is prone to leak. It also destroys the o-ring when you try to fix the leak by torquing tighter. I switched to a smaller ring that fits inside the o-ring channel completely. It is slightly squished to initiate a seal. Metal to metal buttressing reinforces the seal. Torquing does not destroy the o-ring. No more leak. Not likely to blow out.
Given the depth of the channel as 1.8 mm, we add a little extra to get some ring compression. Let’s say a cross section of 2.2
OD is 25 mm.
ID of desired o-ring is 25 mm – (2 x 2.2 mm) = 20.6 mm ID <— not a size available
alternatively 25 mm – (2 x 2.4 mm) = 20.2 mm ID is a size close to an available one.
I would expect one of the following to be allow complete metal metal closure and trap the o-ring totally inside the air filter’s o-ring channel. These ring are a bit bigger CS than the channel depth and should squish enough to initiate a seal. With a buttressed o-ring, the seal gets stronger as air pressure increases. Without buttressing, the seal gets weaker with more air pressure and blows out.
N2.40X019.8
2.4mm X 19.8mm Metric Buna-N 70 O-ring Single (JIS P20)
or
N2.40X020.8
2.4mm X 20.8mm Metric Buna-N 70 O-ring Single (JIS P21)
Blows me away that he hasn’t posted to say that he is going to take care of all every compressor he has sold. Looks like they are all failing. Some faster then others.
All he is doing is trying to pre sell the MK ll version. Funny how the next batch was going to have a price increase and now it’s the all new and improved at same price.
Greed is finally catching up to him peddling Chinese crap.
Yes mine also leaks some oil, I change the filter material every 2nd fill of the small bottle. and just changed the round one tonight (before the color got to the other side of the filter)
I have no problem rebuilding this as needed, I just need access to parts. Has anyone used a caliber on the piston so I can order the ware rings?
when I got mine o ring after o ring was blowing out. I started to use cheap o rings from the hardware and if they are seated they will hold. BUT I ordered and use 10mm dowty rings on my high side. They are worth the cost of shipping $14 for 10 w/ $14 shipping I think it was, the price is up a bit now.
http://www.ebay.com/itm/M10-Metric-Dowty-Washer-Bonded-Seal-2-Pack-/171348552254?hash=item27e52b6a3e
Miksatx
No, haven’t measured the high output pipe temperature yet. That thing was way too hot to touch.
I have two thermistors and a digital temp gauge, but those won’t do any good until a replacement o-ring arrives.
Somehow, I suspect the o-ring store shipment will arrive first.
Until then, can’t fire it up.
Phenolic lives to something like 180C / 356F. Those high pressure rings are not just a “wear item”, but a consumable now we know about their composition.
The closest I have found thus far are “phenolic wear rings”
Anyone have a bunsen burner to flame test a piece of ring and see if you get green flame? That confirm the presence of the copper in the bronze.
bgray115,
Sorry to hear you are having issues as well. That is a pretty fast wear out on the rings. Us users can re-engineer this to run, but although I knew it would require fair maintenance, I didn’t expect to be doing this much work.
I’m interested in your oiling situation. Is yours OK like McKeown’s. If so, I would feel more confident about solving the oiling issue on mine.
BTW any electrical engineers able to explain how this
lowers amperage draw of the MkII?
Mine with the bigger, direct power cord showed only a 3 volt drop at my panel meter at a 26 amp draw. I think that is OK.
Very nice write up ! I also have one of these and after I worked on it to get running and changed a few things the rings and the low side gasket are shot after about 20 fills of a small ninja tank. I replaced the rings with the spares and the new gasket is setting. I will let you know how it works.
Has anyone found a high side ring replacement yet?
Guy have you gotten a temp on the high pressure line running to the moisture separator? Humm inpregnated phenolic, I’d never guessed in a million years.
The rings are no longer described as silicon bronze!
The product page now lists the high pressure rings as “silicon bronze embedded in phenolic” and the low pressure rings as “traditional cast iron.” At least THAT is getting corrected so consumers don’t get an overly optimistic ring lifespan expectation. When I bought mine, the silicon bronze description and four rebuild rings made me think I could get a couple years use out of the supplied rings.
Now, I just want to get the oil issue controlled well enough that the air quality OK for use. As for longevity of the machine, I would settle for getting it running until I can afford a more robust solution.
I’ve ordered the same rings as Michael McKeown to help keep the machine alive.
I don’t see how this guy keeps selling product!! Now he advertising the newer model with improvements at a lower price. Seem’s to me he should stop all sales and take care of the previous costumers that got the shaft! Unbelievable people get away with this and worse yet the customer lets him.
Sounds like this compressor should have marketed as a parts kit rather than a functioning item.
Pretty shitty for everyone that bought one, especially for those without the tools and skills to try and turn this pile of crap into a silk purse.
Maybe some Shinola would help
Lack of proper engineering and design.
These o-ring blowouts are all over the machine. I think part of the reason they happening is how the o-rings are sized.
For instance, the supplied o-ring on the water separator poppet was too large in cross section. That causes the seal to be a section of o-ring resisting huge pressure without metal supporting it against that pressure. Instead, only lateral friction keeps the o-ring seal and that eventually fails. You can improved it a bit by using more torque, but ultimately, it’s just squished rubber between two flat surfaces resisting force parallel to the metal faces.
With a smaller cross section 0-ring, the seal acts more like a dowty washer. The rubber only seals. Metal reinforces the rubber against the force. The smaller o-ring sits inside its channel. Directly metal to metal contact seals in the o-ring and buttresses it fully. The compliance of the rubber lets the pressure push it up agains the now, much smaller gap to form a non-failing seal.
There are multiple places on this compressor where you have this situation and need a dowty washer (if the joint is flat metal to flat metal) or a smaller cross section o-ring (if there is a channel for the o-ring to fit within). An oversized o-ring can make things worse because it could prevent full metal metal contact that forms the reinforced seal. At the very least, you need to be able to torque down far enough to make the sealed gap very small.
[Edited for spelling and grammar]
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I know MRodAir is KNOWN for placing blame on others, but he is even “blaming” GUYKUO for the work he has done to his compressor over on the yellow.
Here is his reply to someone who’s AirMax just crapped out:
(Login Mrodair)
YF12
Give us a call Monday and we can walk thru the systems.
April 23 2016, 9:17 AM
Pretty simple.
Two or three places to check and we have parts on the shelf if any are needed.
By now, you have run it enough to know how well it works.
No need to tear into the unit as some have, as this can not only lead to other problems, but will also make the
diagnosis much more difficult.
We are here to help.
http://www.network54.com/Forum/79537/thread/1461373125/last-1461417478/Expand+Thread