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
Drilling stainless is not a issue with a high speed steel bit. I drill it all the time and have never burned up a bit. You need to drill it at around 200 rpm.
Michael,
I did not intend to put you in the same bracket as the seller (who BTW once again is not answering my emails about filter replacements).
But when I read your web page that states you will solve all points of failure and it will make this compressor the same as the Bauer it upset me for a few reasons.
1) I agree your plate is a great idea and worth the cost, But this doesn’t fix the ring issue so oil will get thru the system. (oil will also pass thru the high side rings after they start to expand and leak by).
2) the filter systems on a Bauer are built to remove water and oil. Your intake filter can only help But that will not remove all the water and none of the oil from the system.
3) with only the small factory desiccant system in use it will remove some water and oil, but it will only hold up for about 10 min of use. then it needs cleaned and replaced. without the upgraded (LOL) paper filter the rest will go right into the tank or gun you are filling. THIS is the number one thing anyone with this compressor must keep in mind, the condition of the out going air.
I respect you are helping others BUT please do not give them a false hope that they can change a few things and then run this system thinking they fixed everything. If you use this (I do all the time) you must clean the filters after every time you fill a small tank and during cool down on a big tank.
Re. Bgray115’s comment: Please put this in perspective. 1) My air consumption use the last three years has been once or twice a year I have my Great White topped off. My Airmax actually does function, so despite lack of rod bearings etc. etc., it takes 9 minutes for me to accomplish my fill. If I do that once or twice a year the compressor should out last me. 2) the parts kit I’ve put together I have sold to 1, yes, 1 person. I have another fellow I’m making one for now which will make 2 omg incredible volume sales. I am not looking to ‘rip’ people off. In fact, I fully expect to make no further ‘sales’ if you can call it that because no one else in their right mind would buy this compressor if you can even call it that. In my mind I’m more at a favor level helping out a couple of the guys that have worked with me for the last few months addressing issues. and 3), the materials cost for what I’m doing in that compressor kit I’ve put together are significant, and it’s a ton of labor. I’m using stainless steel for the reed valve plate and I bought a set of cobalt drill bits which lasted for two plates, and have just bought another set of drill bits to make this next fellow’s plate. The 1/2″ and 9/16″ bits are $20 each, not counting the four I think other sizes. The steel itself is not cheap. I just bought a piece yesterday from McMaster Carr for this next one I’m doing because I broke off the skinny 4mm (!) tap in the remaining piece I had. It might take me two or there tries to get a good one to come out. The 1/2″ aluminum for the head is not cheap. Then there’s the gaskets which I’m paying to have laser cut one at a time at the local trophy shop because I have zero expectation of any kind of ‘bulk’ sales and he’s got a minimum hourly rate.
But above the materials cost and the full day putting the kit together (what do you value your time at?), there was a TON of time drawing the gaskets in Illustrator for the laser cutting and measuring the dimensions of the head and reed valve plate and drawings those parts, all of which I give away for FREE on my web site for people to make their own! (actually I took down the reed valve plate and head I think ’cause I have new improved drawings to put up…but I will).
I’m afraid to figure it down to the dollar, but I’m pretty sure I’m not actually making any money on that kit. So don’t bust my chops and lump me in the same boat with Mrodair who did our community a huge disservice bringing in such a crap product. Oh sure it’ll work for a few of us that have minimal fill needs, but if I could only share with you the empty promises and lack of response to requests for parts I’ve had from Mrodair. I am NOT THAT! What I am is a gunstock carver! Please remember that. I’m not trying to be a machinist ‘ripping people off’ on improved parts for an already garbage product, and by all means I encourage any Airmax owners to hand cut their own gaskets and mill their own larger reed valve plate and head with the drawings I give away for free. It’s not hard for a hobbiest with a milling machine with digital readouts and a rotary table.
Or take Guy’s advice and save your money for a real compressor.
Michael McKeown
http://www.airgunstocks.com
Trying to keep on top of potentially deadly defects is courting a trip to the boneyard.
Use a hand pump until you can get a well-made compressor and keep either in proper working order. I used a Hill for five years before saving enough for a Bauer Jr. While Guy customized his (Bauer), mine was given just a switch and plug. Plus, they’re made in the USA, fairly close to where I live.
DO NOT DO THIS! I am shocked that another would try and rip off guys who got ripped off already! this is not fixing the oil problem and he removed the paper filter!
I can’t even think after reading his web page this is ridiculous !
Looks like there’s a fix for the air max compressor:
http://www.airgunstocks.com/airmax-mods.html
So all u have to do is spend an extra $260 and you’ll have a fully functional compressor.
This invaluable info should be a sticky on every forum this compressor is even mentioned on!
Great job Guy, I don’t own this compressor but definitely informative for others who are in the market for one.
Walkon, if we save some other airgunners from making the same mistake, it was worth me trying it out and reporting here.
Months ago I couldn’t understand why it is so difficult to build a compressor that is good enough for airgun usage, but not the “overkill” of a dive compressor. The cost gap seemed huge and unreasonable. As I learned more, it became clear there really isn’t much difference between what a diver needs and an airgunner needs. Getting a compressor built well enough to reliably supply dry, clean air, naturally converges on the design of a dive compressor. Leave stuff out and things become questionable. This compressor cuts design margins in too many places.
Safety is #1 concern in this hobby.
Thanks for doing all you have done and informing everyone about this.
The rods bottoms look wide enough that there’s the possibility of pressing in roller bearings to expand the lifetime. Just a thought. Did your small engine mechanic offer up any alternative for replacment pistons?
I said something way back in the thread about the lower end. If they couldn’t build the top right, why would they build the bottom end right.
He is going to try peddling another 50 of these things here real soon. I hope people are more in formed now and nobody makes the mistake of buying one.
There is no way everything was fixed in the MKll. He is saying again it’s a 3 cylinder compressor. Just amazing
I’m so sorry to hear that Guy. Thank you so much for the extensive display of work you have shown us!
Took the low pressure cylinder assembly to a local small engine shop today. They were kind enough to spend time examining the piston, rings and cylinder. Let’s start with how you get the low pressure assembly removed.
The crankcase needs to be drained of oil and the crankcase cover & gasket membrane removed. The motor shaft extends into the crankcase a short distance. Onto the motor shaft, the counterweight / journal is clamped. The piston rods hook onto the journal and are secured by a single, left hand threaded bolt. Removing the bolt is easily accomplished by stopping rotation of the counterweight/journal with a small block of wood placed inside the crankcase.
Then remove the cylinder head, valves, and reed valve mounting pins. That leaves just the cylinder, piston, and piston rod. Two bolts attach the cylinder to the crankcase. Once those two bolts are out, the entire cylinder can be freed by sliding the assembly towards the free end of the journal.
Here is the low pressure assembly removed.
While everything was out, it was easier to examine the parts and get better pictures.
There are no hardened bearings protecting the piston rods. The piston rod aluminum itself is the wear surface for both ends of the piston rods. Even with just 80 minutes of run time, wear and pitting is evident inside the piston rod “bearings”
Here is a closer view showing the wear and pitting. I was wondering why the crankcase oil was so black. Blowback carbon from the high pressure cylinder was one thought, but after seeing this, I suspect a fair amount of the darkness is actually worn aluminum. Those scrapes and pits in the below picture are not residual oil. That is what the bare aluminum looks like inside the wear area.
With just the right lighting angle, there are some faint lines that might be fine honing. They are at an extremely shallow angle and are visible at the very top of the cylinder.
The main cylinder walls show the lines from the rings moving up and down.
So, back to the opinion of the master mechanic after he took apart and examined the assembly. He thought the ring gaps were actually OK and not enough to be the reason for the oil consumption problem. Also, he found the cylinder smoothly polished. The degree of honing was also thought not the culprit for my problems. If any honing was done, it would need to be very fine.
Then it came to the rings themselves. “Poor casting quality” He was not at all happy with how the rings looked and especially with their wear pattern being only on one edge. Something is making these rings wear oddly. His ahha moment was when he took the piston itself and checked the piston’s clearance in the cylinder. He declared that to be the most likely issue for the rings not sealing. The piston is too small for the cylinder bore. It likely cants excessively during the cycle and thus the rings keep breaking their seal.
I am very grateful to Gary at PSR Equipment Repair for the time he generously spent examining the assembly. When a 37 year experienced engine mechanic not only tells you what he thinks is wrong but also shows you how he came to his conclusion, I believe him. He had nothing to gain sharing his knowledge with me. I gave him my thanks and felt more at peace knowing I had done as much as I could for this machine.
There is nothing more I can reasonably do to make this poor constructed compressor work safely. With its severe oil consumption problem, it poses risk to my lungs, my tank, and gun seals. If you are fortunate enough to get a unit whose tolerances are better, consider yourself lucky. Once, you are stuck with a bad unit, you’re basically on your own —- and that means scrapping the compressor. Even if you are lucky, the machine isn’t constructed to have an extended life. Bare aluminum as the bearing is yet another finding that shortens my estimate of its lifespan.
My final recommendation is to avoid purchasing an Mrodair Airmax Extreme compressor. I started out optimistic that this would be a good choice. I have documented my findings here so that others can benefit. I took the hit so you don’t have to.
Save your money for a proper, full scale diving compressor or a Shoebox & and Alpha filter. Either of those routes will get you more reliably and safely to a clean air supply for your air gunning.
Guy
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Michael is a victim as well. He’s helping out the unfortunate souls who have this compressor, not promoting the sale of more units.
The website does sound a bit too encouraging, but I’m sure that isn’t the intent. I don’t think the end result is anywhere near comparable to a Bauer now that I have both in the garage.
That ONE person who bought his parts kit….. That was me. Installation of the cylinder cap and air filter, power cord strain relief is documented early in this thread.
Now to figure out the best way to dispose of the Mrodair Airmax. Wife says to put it at the end of the street with a “free” sign and it will be gone within a day. I’m thinking it probably needs more a warning sign.