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.
===========================
Disclaimer: Material presented here may be incomplete or inaccurate.
Work you undertake on a compressor is expressly at your own risk.
===========================
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
Does by chance you have a picture of the wires of the engine under the black hood? I just recieve my chinese compressor and after I plug the cord at a 20 amps 110v to do a test run of the engine , it run for 30sec and the computer conector over heat and melt, so I plug a 12-3 cord directly under the hood and notice that my reset button was not enven plug and how the wire are tiny, this dont help for is power efficiency. Also , how much quart of oil does it take to fill the engine at level?
Thank you
Thanks. It’s a pity these aren’t consistently built to tighter spec. The overall engineering is workable. I still think these can be made usable and kept running, but you face a lot of work to ensure things are up to snuff. You are the last quality control step. If you read through all the problems I have faced, you’ll see most of them are fixable. The blow out problems are largely avoidable by getting the right size and type o-rings into place. Torquing has to be adequate. All doable, but wow. It is a lot of work for a ready to go product that promises years of service life. You don’t know if your particular unit is going to be a good one or a dud. They undergo test run fills, but filling a small tank will not catch all the issues. You can still be stuck, like me, with a problem unit.
I got extra stuck because I foolishly believed mine was fundamentally OK because it was already test run at MrodAir. I focused on adding safety features and preventative work so it would have a long life. I should have focused on functional testing before staring work. By the time I discovered underlying problems, it was too late. I already had my control panel upgraded and was past my 30 day window.
I have a bad low pressure assembly that sucks tons of oil into the air chamber. If I didn’t have that problem, I could soldier on and make this work. With an oiling issue, the fix got beyond what I can reasonably do as an end user. Sure, one could rebore, hone the cylinder, and source & test new o-rings. The experimental cost would quickly make this compressor as expensive as a fully scale dive compressor. When I ran into the oil issue, I was crushed. I didn’t see a practical way forward. You can see it in my note of defeat.
This doesn’t seem to affect all units, but if yours has a bad oiling issue like mine, stop using it! Oil in your high pressure air is just plain bad. I got saved because the Alpha filter can handle a pretty big oil load. The tiny filter that comes with the compressor would not have been enough.
I hope Michael at Mrodair successfully finds a good fix for those of use who have an oiling issue or are destined to develop an oiling issue. He should be receiving alternative o-rings and valves to try within the next week or two (by my estimate). I await word and will report whether we are able to fix it on my unit. Success would be a very good sign regarding customer support and whether this machine really is going to be a viable solution.
Test your unit. If you don’t have the oiling issue, congratulations. Most of the other weakness of the machine can be ameliorated. It’s a shame you have to ameliorate the issues, but you can do it. Learn what you can from this thread. Change out the o-rings to correct size and material. Fix the leaks with teflon tape.
The machine will produce high pressure air at a fast rate. Don’t treat this like a robust dive compressor. It is not. It runs too fast for its own good. Even with the high pressure head steadily below 70C, the internals are under incredible thermal load. Chemlube 501 doesn’t break down until 500F. This machine decomposes it to soot within the high pressure cylinder. It is THAT hot.
Run the compressor for max 15-20 minutes at time. Let it fully cool before restarting it.
Bleed the water separator out frequently. Use a good dryer filter if you want to protect your tanks and guns.
I’m guessing the Mrs has the same philosophy 😉
I don’t have a Mrod to deal with, but I think it pretty cool of you et al to put the effort into trying to make this work, and sharing what you learn.
IMO is the mark of a true craftsman.
Interesting stuff to look through. After this experience, I’m even more leery of materials quality, finish level, and durability of the items shown at that site. Some of the fittings look lower grade than what Mrodair’s has — and that isn’t a hugely high bar. Those unit prices are amazing, but I’m not going to expose my credit card or fight through importation hoops.
One thing I did notice looking through the pictures and suspect is also true on the Airmax is that no bearings are seen for the piston rods. Are these all bare aluminum of the rods running against the piston wrist pin and crankshaft journals? Would have to tear down to verify, but really I don’t see any rod bearings in that array of parts being sold.
New 30 amp, 4 pin, 240 VAC service installed yesterday. Will change the Airmax to a “one legged” 240 plug so it can get 120 VAC from the new outlet. I installed a 4 pin outlet just so the Airmax compressor can continue getting power. Of course, that probably means the Bauer’s power plug will also need to be changed from a 3 pin to 4 pin plug.
Witch air cooled compressor do you talk ?
The new air cooled pump they are selling has a better setup water/oil block before the old water/oil block. and they put a burst outlet. I also see they changed the location of the lines the output air comes from the top of the block and the input in the bottom.
I know you are going to have your Bauer , but maybe this will be good for someone else .After looking at alots of chinese hpa compressors build on a jaguar compressor donor. Some of them have a oil-water separator between the low pressure and high pressure cylinder. Not a bad Idea for a modification!!! Here is a link for a oil-water separator http://www.yoycart.com/Product/525330176734/
The other link is for parts if you want to modify it or just fix it!
http://www.yoycart.com/seller/aa85260482/
the last link is a good option for when your are not home without more air.
She describes each time I go into the garage as….
Yes, I do tend to stubbornly work a problem until it is solved.
It would be nice to get this successfully running for all the other guys who are also guinea pigs.
Every solution we can document is a solution that might help someone else.
Every problem we discover is something to help others avoid that problem.
Bauer is schedule to arrive from California on Monday! :biggrinn:
Will be rewiring my 30 amp 120 VAC RV outlet as a 30 amp 240 VAC service today.
I run mine at most 15 to 20 min. at a time so I can clean the filter(s). I started to get white on my housing also, I am going to clean and polish next time I open it.
Ironic how you keep working on this POS even after your wife said ENOUGH! LOL! I’m sure it’s gonna keep eating at ya until you get it running…properly! Lot’s of good info…good luck buddy!
Yes, it would replace the one around the high pressure reed valve
Michael McKeown has reported his has swollen. He thinks the original ring should not be coated with silicone oil if one does a rebuild. I think the heat is the problem. Buna o-rings can only survive to 250F. Mine blew out at 4100 psi without ever being coated with silicone lube. I think a combination of high temperature, pressure, crankcase oil exposure, and imperfect metal-metal seal mating between cylinder and cylinder head did mine in. It had, after all, just tried to fill a Great White over about 80 minutes near continual run time.
A silicone o-ring should resist the heat and chemical attack. I have also lapped my cylinder body’s top to improve metal-metal mating and increase cooling of the cylinder head via heat transfer compound. Swap in a silicone ring and I think this ring should be less a blow out risk.
On the other hand, maybe we need to have some points of somewhat easy blowout. This compressor lacks any safety burst disks. If you look at better engineered compressors, they have burst disks to prevent more catastrophic damage.
Another interesting tidbit I have run across is that the water separator, even on a super engineered Bauer, has a limited number of safe pressure cycles before they recommend replacement. This is to avoid rupture due to metal fatigue. Bauer recommends something like 1,000 if full cycles from 0 to 4500. Each bleed operation counts as a cycle. Now if a finely built, German machine, with probably better quality aluminum has such a limit, I ponder how we will discover the limits of the one on the MrodAir. Mine starts off with visible white speckles on the interior wall of the water separator.
Guy
NICE This is for the top of high pressure plate right? How many has had this fail? That is one I have not had fail yet.
Found some 3mm x 16 mm silicone, 70 durometer o-rings to try on the high pressure head.
New high pressure rings and replacements for my blown out high pressure head o-ring arrived today from Mrodaair. 😀
All ready to keep the high pressure side up and running, but can’t do anything until oil issue is solved. Otherwise, not safe to proceed with high pressure runs.
- You must be logged in to reply to this topic.
Sorry to hear of your IEC connector melting. They are not meant to carry so much current. Probably was okay with a 230 volt setup, but with a 120 volt setup, the amperage is too high.
I have not opened the plastic junction box atop the motor. All my wiring was directly to components mounted on my top panel. Your configuration may be different.