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
Almost or more than happy ending on your part getting a Bauer. Not so much if you start adding the cost of all testing and fiddling with this one.
I would be tempted to “rehab” your airmax, if it wasn’t in the other side of the world. But I think I’ll be better off just building my own when I feel like doing it, until that is finished the booster keeps my guns full…
Hope mrodair comes up with a viable solution on all that they have sold, or becomes nimrodair and goes out of business.
Marko
An incidental, albeit currently useless, side project was done for the high pressure cylinder. I wanted to improve the cylinder wall cooling and also keep the cylinder head better sealed and cooled.
I lapped the top of the cylinder housing flat and used heat sink compound (silicone based) to thermal couple the high pressure head to the cooling system.
That o-ring around the reed valve wafer is prone to blowout due to high temperature exposure. I think that should be changed to a more heat resistant material like silicone, but that is for another day.
If you look at the water jacket, the inlet and outlet are near each other and could have a “short circuit” flow pattern. I wanted the cooing water to scrub along more of the cylinder wall. So, I added a piece of aluminum sheet metal at the water inlet. It is crimped into place at the top of the inlet. The shape promotes the water flow to go around the cylinder. Might not make much difference, but easy to try.
There still is a huge adiabatic heating that occurs. The only way to help that is to pre-cool the incoming air. The tube running from 1st to 2nd stage is short and doesn’t allow for much cooling. Ideally, a coiled intercooler would be there. Cost is an issue and I don’t have a source for HPA rated stainless steel coils with ends that would fit this machine. Perhaps cooling fins and a water jacket there (and on the output from the 2nd stage) would be possible.
Well the o-ring and gasket failures, yes. Those can be heat related. That’s why we’re finding the machine only tolerates 15 – 20 minute long runs even with aggressive water cooling.
The more serious issue of oil getting into the air is something not related to length of run. That starts right away if the low pressure cylinder has a seal or valve problem. This is still being investigated by MrodAir and possibly there will be a kit to remedy.
I haven’t decided whether to keep my special 120 volt 30 amp RV outlet to continue occasionally tinkering with this Airmax or just rewire the outlet box for 230 volts to feed the new compressor. Wife votes just rewiring for 230 volts and finding someone who might want to “rehab” my Airmax.
Oh, wait. I can rewire the outlet for 30 amp 240 VAC and change the plug on the Airmax to use one leg. I can still test out any fixes if they are forthcoming.
I wrote Michael at Mrodair….
It is a damned shame the oil issue is happening. Simply can’t have that getting into tanks and guns.
If the amount of oil could be minimized, a big air, oil filter with PMV like the Alpha can bring the air up to snuff
and improve the water separator performance.
The rest of the weakness of the compressor can be more easily overcome. Most are just bad choice of o-ring size.
I think the high pressure cylinder head o-ring would be better off done in silicone, but you’d have to test
that for strength.
The high temp water cooling jacket cooling could be made more efficient pretty easily.
Some clip on cooling fins on the high pressure lines or longer lines with cooling coils would improve things.
In my eye, the overall design isn’t that bad, but your OEM’s have big problems with build quality, tolerances and choice of sealing ring sizes/materials. They have turned what should have been a category defining triumph into disaster product launch.
I was one who pre-ordered and believed you had cracked the nut. Really sorry it has gone south.
Guy
I was looking on alibaba for a hpa compressor , with more reasearch I found that mrodair sale a Identical compressor , but not sure it is made by the same compagny. So I bougth directly from China. The seller tell me the spec are: 60L/min 110v 60hz , 1L botle MAX filling and 4 PEEK high pressure ring. He say that the compressor is not design to run for 1Hour. He can do it but not push high psi for that much time. I belive they produce too much heat and they fail because of that! Do you know the spec of the mrodair? Maybe you push it too much by filling your big tank?
Ford Pinto :whistle:
That will never happen. It’s always “your the only one with this problem”.
Yeah. First email says he getting pieces cut and parts. Now it’s all coming from China.
So either they new they had a problem or it cost more for better parts and he opted for yhe cheapest version.
Funny how they already have a sulution to a “select few” that have a problem.
Considering these are suppose to be a “plug and play” compressor many airgunners will take that for what it is worth and if they are not on the forums and do not realize the real danger of oil entering their gun or cf tank someone is going to get hurt.
With this much problem a RECALL of the compressor may be in order.
Well, I’ve learned a lot about compressors, oil water separators, filters, pistons, ring gaps, PM valves, o-ring sizing, dowty washers, poppet valves, o-ring temperature limits, and more during this journey. I hope sharing my findings and work has helped others. I wish I knew more at the start http://www.talonairgun.com/forum/viewtopic.php?f=52&t=33430
The CFO (wife) has declared she is done letting me spending so much time on the Airmax. After an appropriate scolding for trying to be too cheap, I was given the OK for a replacement compressor. A Bauer Jr now has my name on it. I am very lucky I get to do that. I’ll probably do a little more on this machine. Maybe see if the re-build parts help fellow owners, but my active phase is coming to an end.
At least I got some education and a new avatar 😕
That’s the goal here, to get the oil out, pmv and good filter tower is a must. All comps breath oil, even Bauer. There’s always some oil in the water separator tower when bleeding them, but that’s it’s function, separate water and oil from air. And to work properly a pmv is required.
Oil is bad, hell even wrong thread locking compound can ignite in hpa aplications. The company I work in fabricate gas centrals for hospitals and what not, oxygen, nitrogen, hydrogen, so I personally know what’s what and safety protocols. Ther are of course different people with different educations, safety is a must in all hpa related work. Nobody wants to die for a hobby.
Everyone using a compressor needs to read this PDF
“Prevention of Explosion and Fire in Compressed Air Systems and Vessels”
http://file:///C:/Users/Adam/Downloads/311____0.pdf
:tag:
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
So this will likely be the SAME junk as in the compressors now……….anybody want to bet it will be Halloween before the get into peoples hands? Do you have to pre (pay) order them?
So I guess they are now going into the “parts” business……..makin mo $$$$
MRodAir is a JOKE!
So how much is a lease for N2 tank lease and delivery with a regulator?
I bet a lot less and far better air for your guns.
If you guys get ANY OIL in your HP tanks and guns you are going to have an explosion.
I can not stress that enough.
http://www.tpub.com/engine3/en33-75.htm
COMPRESSED AIR PLANT OPERATION AND MAINTENANCE
As an Engineman, you must be thoroughly aware of the operational and safety procedures you must use when you are operating or main-taining a compressed air system. You must operate any air compressor or air system in strict compliance with approved operating procedures. Compressed air is potentially very dangerous. Keep in mind that cleanliness is of greatest importance in all maintenance that requires the opening of compressed air systems.
SAFETY PRECAUTIONS
There are many hazards associated with pressurized air, particularly air under high pressure. Dangerous explosions have occurred in high-pressure air systems because of DIESEL EFFECT. If a portion of an unpressurized system or component is suddenly and rapidly pressurized with high-pressure air, a large amount of heat is produced. If the heat is excessive, the air may reach the ignition temperature of the impurities present in the air and piping (oil, dust, and so forth). When the ignition temperature is reached, a violent explosion will occur as these impurities ignite. Ignition temperatures may also result from other causes. Some are rapid pressurization of a low-pressure dead end portion of the piping system, malfunctioning of compressor after-coolers, and leaky or dirty valves. Use every precaution to have only clean, dry air at the compressor inlet.
Air compressor accidents have also been caused by improper maintenance procedures. These accidents can happen when you disconnect parts under pressure, replace parts with units designed for lower pressures, and install stop valves or check valves in improper locations. Improper operating procedures have resulted in air compressor accidents with serious injury to personnel and damage to equipment.
You must take every possible step to minimize the hazards inherent in the process of compres-sion and in the use of compressed air. Strictly follow all safety precautions outlined in the NAVSEA technical manuals and in the Naval Ships’ Technical Manual, chapter 551. Some of these hazards and precautions are as follows:
1. Explosions can be caused by dust-laden air or by oil vapor in the compressor or receiver. These explosions are triggered by abnormally high temperatures, which may be caused by leaky or dirty valves, excessive pressurization rates, and faulty cooling systems.
2. NEVER use distillate fuel or gasoline as a degreaser to clean compressor intake filters, cylinders, or air passages. These oils vaporize easily and will form a highly explosive mixture with the air under compression.
3. Secure a compressor immediately if you observe that the temperature of the air being discharged from any stage exceeds the maximum temperature specified.
4. NEVER leave the compressor station after starting the compressor unless you are sure that the control, unloading, and governing devices are operating properly.
5. If the compressor is to remain idle for any length of time or is in an exposed position in freezing weather, thoroughly drain the compressor circulating water system.
6. Before working on a compressor, be sure the compressor is secured and cannot start automatically or accidentally. Completely blow down the compressor, and then secure all valves (including the control or unloading valves) between the compressor and the receiver. Follow the appropriate tag-out procedures for the compressor control valves and the isolation valves. When the gauges are in place, leave the pressure gauge cutout valves open at all times.
7. When cutting air into the whistle, the siren, or a piece of machinery, be sure the supply line to the equipment has been properly drained of moisture. When securing the supply of air to the affected equipment, be sure all drains are left open.
8. Before disconnecting any part of an air system, be sure the part is not under pressure. Always leave the pressure gauge cutout valves open to the sections to which they are attached.
9. Avoid rapid operation of manual valves. The heat of compression caused by a sudden flow of high pressure into an empty line or vessel can cause an explosion if oil or other impurities are present. Slowly crack open the valves until flow is noted, and keep the valves in this position until pressure on both sides has equalized. Keep the rate of pressure rise under 200 psi per second.
SUMMARY
In this chapter, we have covered the various types of air compressors you will be required to operate. We have discussed how the air is compressed and the requirements and methods of producing oil-free air as well as how moisture is removed from the compressed air. We have also discussed some of the safety precautions you must use whenever you are operating or working on a compressed air plant or system. If you are unclear as to any of this information, go back and review this chapter before proceeding to chapter 15.
Yes, the total cost of an intermediate level compressor has to be about $1300-$1500 delivered and functioning. It has to slot in between a Shoebox and a dive compressor. It must be faster than a Shoebox yet slow enough not to destroy itself. 0.5 – 0.8 cfm would be OK if the machine has good lifespan. The air output needs to be clean and dry. The key is the baseline unit must already work well. If it did work and had clean enough air output, the Airmax would be a success. Mine hasn’t.
Once you have problems, the overall COO gets awful close to a dive compressor. Add $400 for an Alpha filter to get actually clean, dry air. you are nearly 2/3 of the way to a Daystate or Airetek. Add the value of time needed to fix it up and you ARE in the realm of a full scale compressor.
My Alpha filter saved me from getting lots of oil into my Great White and Vulcan. I didn’t understand how molecular sieve could scrub out the oil. I opened the filter and now see why it was so effective at keeping the nasty oil at bay. It has a activated carbon segment. I didn’t know it had that. Brancato never mentions that feature, but that saved my Great White. I would call this a must-have if using a compressor that has oil control issues and lacks a substantial size drying media unit and pressure maintaining valve. The Alpha takes care of that, but its cost shifts the total price point.
Hopefully all the o ring grooves can be matched with a proper size o rings or failures won’t stop.
Sounds like a full rebuild kit, with upgraded parts, we shall see.
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Not much more going to happen here until Mrodair finishes testing some other ring designs.
One he mentions is a permaseal type