Mrodair Compressor Guinea Pig
Hello, a newbie to PCP’s here.
I put in a pre-order for the upcoming Mrodair “Airmax” compressor
Thus, far just an automated acknowledgment receipt from Yahoo and haven’t heard anything more re ETA.
Yep, guinea pig ordering a new product. Hopefully it works out.
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Cool. We could make it a reference for those working on getting these things prepped.
Guy
Wow,
Thanks for all the hard work.
If you have the desire you could start another thread and copy and paste all your work there and I will make it a sticky so it does not get lost among all the other posts
Yep. Instead of a rebuild, it’s a Pre-build.
Amazing write-up and pics guykuo! Too bad you are having to do all this work on a frickin new compressor! Looking forward to your progress towards getting it running…
Earlier in this thread, I didn’t know about the relay and contactor mounting rail. I fashioned my own bracket. Here is how the relay and contactor should be mounted on the rail. They each snap into position. If properly snapped on, they won’t fall off even if you tug on them. It is possible to partially snap them into position. If you don’t get them all the way snapped in, they CAN and will fall off the rail.
The finding that the units do indeed stay in place despite firm tugs is pretty good evidence that if these were loose at time of delivery, they simply weren’t properly snapped into position or were simply not even snapped into position. They didn’t fall off during shipping.
The normal, central mounting position for the relay and contractor leaves no space for the extra switch and hour meter I want on my compressor.
So, I moved the mounting rail about 2 inches rearward. This leaves plenty of space for my upgrades.
I’m replacing the original, single switch with a pair of switches. Also, my hour meter needs a mounting position. That means cutting new panel holes and enlarging the existing one. I followed McKeown’s advice for cutting the holes.
First drilled holes tangential to the corners. Then cut with a dremel tool with a cut-off wheel.
The finished panel holes.
Of course, one must have nice labels and cover the old rail mounting holes. Color laser printers are pretty handy.
Clear plastic tape secures the label.
Now, the switches and hour meter are mounted and ready for wiring.
Separating the low pressure cylinder cap from the water cooling block takes a chisel and light whack.
Be mindful of the black gasket at the bottom of the cooling block! Don’t damage its tabs by improperly
positioning the assembly before the “diamond cleaving” operation.
Put the chisel right at the seam and light tap with a mallet is all that is needed to part the red RTV
adhesive.
I temporarily removed the o-ring to make removal of all RTV from the cooling block easier.
Once the RTV was gone, the o-ring went back into its groove.
Prepped the new, longer cap screws by transferring the washers from the original bolts. A bit of anti-seize on the threads and it
is ready to go.
Verify the alignment of metal valve flap, intermediate air guide, and water cooling block. When properly positioned, each
detents into places. Once all are aligned, add the new gasket atop the cooling block.
Four bolts and the new cylinder cap is in place. Time to celebrate! Oops, the air filter won’t fit because of mechanical interference.
One metal tab needed to be trimmed. I protected the air inlet with tape during the trimming.
Now the air filter threads right in. Perfect. This is how the “upgraded” compressor should have been.
The IEC connector supplied with the compressor is only rated for 15 amps. Michael McKeown’s kit includes a strain relief so one can completely eliminate that problem and connect a power cord directly to the compressor’s switch. You also have to do this because the red panel that original holds the IEC connector would interfere with the air filter.
I’ll be adding the power cord later. Meanwhile, there are some other electrical upgrades.
Seven more hours of work to get things closer to “plug and play”
First, the materials used…
The new low pressure cylinder head is threaded for the filter. Longer cap screws, gasket and anti-seize help everything fit together.
The strain relief is used for bypassing the 15 amp (under-capacity) IEC connector that comes on the compressor.
Here is how the filter screws onto the new cylinder head. The threads to about 4/5 of the way through the cylinder head. The last 1/5 of the hole is smaller diameter so the filter can’t screw in too far.
Chemlube 501 is a high temperature compressor lubricant. It should suffer less carbonization than the original oil.
The original oil was already breaking down into up some ugly black carbon deposit on the high pressure piston
with just the short to check out the compressor in Arkansas.
Two DPDT switches and a runtime meter will be needed to wire things up the way I wish it was already.
The switches will run in series. The first will energize my cooling system AND supply power to the
2nd switch. That second switch will be able to power up the compressor ONLY if the cooling system
has been activated by the first switch.
The hour meter will help me know when to change oil. The change interval seems to be somewhere between 50 and 100
hours based upon what I have been reading on dive compressors. The hour meter will make things easier to track.
The original on/off switch on my compressor was only rated for 16 amps. It was NOT a 30 amp unit as reported elsewhere.
Actually, I couldn’t find any 30 amp switches at 120v either. The ones I ended up with are also rated 16 amps at 120v.
They are 30 am units only at 12 v. We’ll see how they hold up.
Luckily for me, the original oil drain plug was easy to remove with a light touch of a wrench. It did not disintegrate on me.
The original oil was surprisingly dark. This compressor is new and has ONLY been run at MrodAir.
I have never run it.
Draining the the oil took about five minutes. Had to tilt the compressor to get more out.
Five bolts hold the crank case cover in place.
WARNING FOR LATER: BE VERY CAREFUL WHEN TIGHTENING THEM! It is easy to strip
the holes into which they go. In fact, I had one strip with just hand tension on the socket while putting things
back together. From what I can tell, it was essential, already stripped. Fixed that problem by cutting new threads and
using a larger diameter bolt.
Gently remove the crank case cover to avoid damaging the gasket/membrane that forms the
seal between the cover and the crank case.
This is the gasket/membrane partially removed. It peels off neatly. The membrane partially isolates the cover from the main crank case volume.
Inside the crank case, you can see the connecting rods, splash dipper, and counterweight.
The splash dipper is actually part of the low pressure piston arm.
Cleaned out 99% of the original oil by wiping down the interior with mild solvent.
I was surprised by how black the oil was. Look at this paper towel that
has wiped through the oil. This isn’t soaked through, just a wipe along the bottom.
Washed the gasket/membrane using Dawn and some cotton balls to get it really clean.
Because I plan to change oil fairly frequently, I also modified the hole at the bottom of the membrane to permit more complete drainage
of the crank case.
Putting it back together. The gasket bead fits into the crank case cover’s groove.
AGAIN, be super careful and don’t over-torque the bolts. The threads of the crank case are thin. It’s aluminum. Heck the wall of the crankcase is only 0.1 inches thick. So, be gentle. Just a few inch lbs of torque are needed — just beyond finger tight. You only need to compress the gasket enough to seal against oil leakage. Doesn’t take much. If you use the HANDLE of your wrench, hold it with just two fingers and your thumb right at the socket. Don’t go cranking with the end of the wrench.
GENTLE. Did I remember to mention Gentle?
Once the cover was back in place, the oil drain was reinstalled with just barely more than finger tightness.
I used teflon tape on its threads to create a seal with minimal torque.
I think I finally figured out the wiring on the compressor. Took a while to trace out all the wires and find the pinouts.
When power is applied to the compressor, the contactor coil is energized via a normally closed contact of the relay.
The contactor then engages and supplies power to the motor.
When the pressure gauge hits target pressure, its contacts close and energize the relay’s coil.
This OPEN’s the NC contact that is powering the contactor coil. The contactor releases and cuts off the motor.
Energizing the relay coil also latches the RELAY on via a N.O. contact in the relay. This is in parallel with the pressure gauge.
The compressor will NOT power the motor again until
1. The power is completely turned off
AND
2. The pressure gauge drops below its cutoff setting.
Here are the changes I am planning…
Another power switch upstream from the original one will ensure the water pump is on before the motor can power up.
Add an hour meter to track how long the compressor has been running.
(Now let’s see if this post survives the forum changes)
Thanks for the link guykuo. I kept my Diablo and use it when filling my tanks. I pulled apart and checked after each fill up, no signs of moisture.
It is huge in comparison to the stock water separator and “filter”.
The JB filter needs to be mounted vertically to properly function as both drier and water separator.
It has its own bleed valve (180 degrees opposite its pressure gauge). The filter also pressurizes BEFORE
it will allow air to exit.
Not cheap though. It’s a significant fraction of the Airmax Compressor’s cost.
Mine had an extra business card wrapped in that packing tape at the bottom of the filter 🙄
Because I would like to eventually get this unit capable of filling a Great White tank, I am also going to be adding the JB Air Filter.
It is huge in comparison to the stock water separator and “filter”.
The JB filter needs to be mounted vertically to properly function as both drier and water separator.
It has its own bleed valve (180 degrees opposite its pressure gauge). The filter also pressurizes BEFORE
it will allow air to exit.
Not cheap though. It’s a significant fraction of the Airmax Compressor’s cost.
Michael at airgunstocks.com has created a proper solution for the lack of an air intake filter.
He makes a thicker head cover so it is thick enough to be threaded.
It is a pity that the compressor’s originally promoted air filter was deleted from the actual upgrade package.
He’s also making a better oil drain plug. His original acrylic one broke upon first removal.
He’s also tackled improving the water separator with cooling and a couple other neat things.
http://www.airgunstocks.com/diy/airmax.html
I agree with him that the petroleum based lube that was in the compressor is getting oxidized and
creating that black residue on the high pressure rings. Going to a higher temp stable oil
seems a smart idea.
Nice and new, looks good, sounds good, let us know how you like it, next year.
I have tried several times to get a hold of Mrodair they do not answer my emails ,,,, they do not answer my phone call’s so I have decided to buy a compressor straight from china through AliExpress they have a really good feed back/review’s … and they will answer emails … all the way from china :winkn:
here is the link if you are interested and these do come with spare parts and you can set the shut off pressure on these ///
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Thanks
We are about helping fellow airgunners here, always have been.
Members here are great at picking up the slack when products do not live up to their promises.