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
Yesterday I bled my Great White down to 3500 and filled it back up again to 4500 with the Airmax compressor (I didn’t go down to 3K in case I had a failure I’d still have some air…it is turkey season after all ). It took 9 minutes and the head temperature reached 180 degrees f. (I’m using the small reservoir it came with). I bled several times getting slightly oily water each time. Very very little oil. The water on my hand would dry in short order and not really leave any oil behind, just the slightly sweet smell of the Chemlube 501. I do not have the auto-cut off gauge and I accidentally allowed the pressure to climb dead headed for a minute or two while I was looking at something and the pressure hit 8,000psi! I think I want one of those shut off gauges!
I carefully measured and calculated and made a list of what I think are the o-ring sizes used on the Airmax. After I get my order from theoringstore.com I’ll report back as to how they all fit and any changes, but it’s a cheap enough order if anyone wants to mirror the experiment:
water jacket x2 N2.50X053
water jacket: x2 N2.00X005
2nd stage head: N3.00X016
separator inlet fitting: N1.50X011 (Guy used) I think it should be N1.80X011.2 I ordered both.
Poppet: N2.40X009.6
media holder: N3.00X17
Michael McKeown
Michael at MrodAir says I now have the ring clocking correct and he is getting the items out to me.
He also mentions something about the gap clearance.
Once parts arrive, I’ll put this back together and see if the oiling problem is improved.
We still have the non-metallic high pressure ring issue, but one step at a time is still better than nada at this point.
I agree they should have gone thru WAY MORE inspection then they did. Heck they “advertised” (and are STILL advertising) the rings as being “Silicon Bronze”……..and they even had a spare set with each compressor………now how did they NOT know the rings weren’t even metallic? Come on, they didn’t even have to do anything to get to them, they were spares!
No way they can pull the “we didn’t know” routine here…….they should be PAYING Guykuo for all his R&D done after the fact……..of course these compressors are old news, they now have the MK II’s that just left the manufacturer on April 14.
http://mrodair.com/airmax_extreme_4500_psi_110_volt_high_speed_hpa_compressor_in_stock_now
Guy , You are more likely the Ernest of compressors . Even Mrodair didn’t go through their product as well as you have done .
Shame on them for trying to make a fast buck by selling Chinese garbage to the masses without being totally 100 % knowiedge-
able about the product that they are selling . Seems like they only know halve-ass of what the compressor is . They should have
taken one apart totally completely to inspect all of its’ parts to make sure that their product was in proper working order and it
had all of the correct components to make it function properly . Looks like that never happened and now besides yourself how many
others who purchased this compressor is going to get burned and have to take a loss ? Mrodair knew from the get go that they were
dealing with a Chinese product and most items made in China as far as quality goes generally will come with a big ? Mark . They will
not be able to give each buyer a refund if their compressor turns out to be a total lost . Sad but true you get what you pay for . I
know because I got burned on Two Chinese Scopes that everyone said was a good scope and both came brand new and both were a
broken piece of shit . Sometimes it is hard to have to learn the hard way . :3: :3: :3:
FROM : THE BIRDMAN
While I await reply from MrodAir regarding my three requests, I examined the low pressure cylinder to see what has happened.
The amount of oil in the low pressure cylinder is as much as when it originally arrived. I had assumed all that was due to it being shipped with oil in its crank case. My pre-cleanup effort was in vain. Plenty of new oil has gotten into the cylinder during my Great White filling attempt.
This time I pulled the cylinder off to look at the rings and piston. There are three metallic rings. The top and middle are simple rectangular profile. The oiling ring has drainage holes around its center. The bottom (towards crank) edge of the oiling ring has a sharper edge. The upper edge is beveled. The sharp edge down towards the crank seems correct direction to me.
Clocking of the ring gaps was the only thing questionable. The oiling ring and middle ring were at 6 and 5 o’clock respectively (nearly aligned). The top ring was at 12. Ideally, none of the gaps should line up. On the other hand, I don’t know how much these rings spin during run time.
Inspection of the rings and cylinder wall didn’t show any obvious defects.
Cleaned things back up and then reassembled with oil, middle and top rings at 12, 6 , 12 clocking to make each successive ring gap 180 degrees apart.
Recompressing the rings was pretty easy. The cylinder end has a taper that can do the last half of the compression. I just held the cylinder with both hands, fingers extending beyond bottom of cylinder. They I could curly my fingers around and compress each ring before it engaged the cylinder.
So, the gapping wasn’t ideal. I’ve improved that as much as possible. Don’t know if the gapping with change during run time. Also the ring gaps are simple straight butts. They are neither tapered or stepped. At least these rings are metallic.
No word as yet from MrodAir. I still need some replacement parts before I can fire this up again to see if the oiling issue is improved.
Can’t really tell from here what exactly to believe, but the guinea pig will try. Nothing to lose now.
I have written and asked for three things.
Let’s see what happens and if this machine can get improved.
Dude, he should offer you more than just moral support on all the hard work you’ve done for him on HIS product!
Good luck!!
Can’t really tell from here what exactly to believe, but the guinea pig will try. Nothing to lose now.
I have written and asked for three things.
Based on your detailed write up all over the Internet – I think I would go with the Squeaky Wheel theory at this point. There are probably 45 or so others out there who we have not heard of with similar problems who are NOT getting any replies and/or support.
Good Luck
I will continue to give the benefit of the doubt. At least, Michael is responding to me and has offered some support.
Can’t really tell from here what exactly to believe, but the guinea pig will try. Nothing to lose now.
I have written and asked for three things.
Let’s see what happens and if this machine can get improved.
—— snip
Michael,
I’m recovered a bit from the trauma of this weekend’s failure and more ready to move forward.
Let’s hold off on replacing entire assemblies. Instead, let’s do the simplest steps first.
There are a couple things that we can probably rule out as being problems based on
the fill rate and fact that I did get up to 4100 PSI.
The reed valves and poppets are probably functioning in both cylinders. Otherwise, I would
not have gotten to 4100 PSI in a Great White tank.
Also, I am definitely intimidated with working on the crank shaft and
possibly leaving the rods improperly secured. Last thing I want is
a rod coming loose during a run.
Given the above, let’s focus on the following
three issues to move towards success
Guy.
1. Oiling problem in low pressure cylinder
Way more oil is getting into my low pressure cylinder than for some other owners.
Charles McKeown’s machine does not make his shop smell like oil and he says
he isn’t getting the oil staining that I am seeing with each bleed of the separator.
Plan: Examine the rings on the low pressure side.
Action:I remove the low pressure cylinder from the crank case and check
the rings and their clocking. If that looks OK, I replace those o-rings with
new ones. That won’t rule out the cylinder, but rings are easier than
an entire assembly
Need from Mrodair: I will need a set of low pressure o-rings and info
regarding the correct orientation and order of rings
2. O-Ring blowout at high pressure cylinder
My large o-ring that surrounds high pressure reed valve disc has blown
out. It really shouldn’t have failed at 4100 PSI, but perhaps detonations
of oil were subjecting it to higher local pressures. If we solve the oil
issue this would be less of a problem.
Plan: Replace blown out o-ring with new one. Also find out if higher
grade o-ring is possible.
Action: I obtain a new o-ring and dimensions/durometer of ring for future
Need from Mrodair: Replacement o-ring & size/durometer of the ring
3. High Pressure Rings are Polymer, Not Silicon Bronze
This is verified by at least two other owners that their rings are
not metallic. This means the high pressure rings will be a source
of more rapid failure than advertised silicon bronze rings.
Plan: Ultimately replace high pressure rings with silicon bronze rings.
Convinced dealership this is an issue for machine longevity.
Meanwhile, use the polymer rings currently available
Action: Replace existing rings using new spares to ensure full seal
despite prior fouling. Also, obtain more rings for expected early
failure of high pressure rings.
Need from Mrodair: More polymer, high pressure cylinder rings
Mrodair should investigate availability of the silicon bronze rings
that were specified. Once metal rings available, replace polymer
rings with more durable metal rings.
Just check the spare ones that came with the machine. MrodAir really does believe they are silicon bronze.
I doubt this is outright misleading on the part of MrodAir, but more likely they got duped by the
OEM. They even have them colored to look like bronze.
I wouldn’t bet on this……..He reportedly “tested” a bunch of them, and “knew” the material used by the competitor….but then wants us to believe he doesn’t KNOW the material of the one he decided on after all this research?
Come on – he’s a SALESMAN
There are no less than 6 manufacturers of this pump in china alone not to mention in Taiwan.
Davey and ingersol compressor contractors are two of the makers we tested and both work well up to scuba size tanks.
After seeing the sales figures from Europe, many small shops in china started making this “type” of compressor and went to price war.
You will know which when you price them.
Our compressor, I don’t mind telling you where they sell them, as the cost for just one unit is over 1150 bucks from china direct.
We purchased the base model for those who want to save cost and offer the add ons for convenience.
We added the option of radiator cooling, to combat the heat buildup when filling the larger tanks if needed and they do the scuba size tanks in well under 30 min.
Using a larger cooling reservoir (5gallon bucket) works well too, ours just looks better and makes the unit much more portable.
The upgrades we sell, were designed by Mrodair and submitted to the manufacturer, so they could be manufactured as a plug and play upgrade to be easily added on later if you find the need.
Our shop tank is an SCBA and 118cu@4500 psi and we fill it with no problem.
The model we sell also has a digital temp meter, so you can keep an eye on the heat when pushing the limits of volume.
Of course, instead of buying our upgrades, simply filling in two sessions with a brief cooling in the middle will do the job as well when filling larger tanks.
The cheaper models, well we tested those too and they build heat much too quickly do to the material used in the rings and poppet valve in the high pressure cylinder.
Some, didn’t even make the 3000 psi mark.
We order ours in very large qty, to save our customers money and support our pcp product line.
This also gets us ALOT of input into how they are made.
We also test every one, every time to fill a 4500 psi tank before they get shipped without exception and keep spare parts in stock right here in the USA.
The compressor posted about above, was not the model we sell.
This is not an advertizment guys, Just a heads up.
You do not have to order from us, but know what you are getting.
We Are Mrodair
My spares the same as yours Guy, non conductive.
Can anyone else who has this compressor check their high pressure rings to see if they are also polymer?
Just check the spare ones that came with the machine. MrodAir really does believe they are silicon bronze.
I doubt this is outright misleading on the part of MrodAir, but more likely they got duped by the
OEM. They even have them colored to look like bronze.
No matter the reason, this is going to impact longevity of the high pressure ring if I get
the machine’s oiling issue solved.
Please just see if they conduct with an ohmmeter. Silicon bronze will conduct electricity.
Mine are completely non-conductive, and not cold to the touch like metal should be.
It is some sort of polymer.
[EDIT: Michael McKeown confirms that his replacement rings are not metallic]
Oh I bet it is not.
This is probably just the tip of the tidal wave that is to come in the up coming months.
Maybe Harbor Freight will start carrying a HP compressor, then at least you can spend a few bucks for full replacement warranty :3: :whistle:
Michael has been in touch and we are considering replacing the entire low pressure assembly. There is support from MrodAir.
I really would love to have this work.
The adventure might not be over.
Thanks. At least the forum gets some info that would otherwise be difficult to obtain.
Michael thinks the low pressure rings in my compressor are amiss, out of order, upside down, or gaps aligned. I have never taken down the machine far enough to see those rings. Only saw the top of the piston from the cylinder head removal. When I get a chance, I’ll try to get those examined. On the other hand, there really shouldn’t be a need for me to correct them (if they are indeed awry).
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So I was filling my 90ci tank when the upgrade filter blew the o ring at 3500psi. Scared the crap out of me and the dog.
sure glad there was a replacement with the other filters.replaced and finished up filling.