OBA -> On Board Air Mega Thread & BS

In the message I quoted you said 70-100. I assumed that’s what you had. So it comes with 130-150 and 70-100 is their option but you found 90-120 elsewhere, right? That makes sense.

 

Does ARB show an expected amps/pressure at 100% duty cycle? That's the number where the lifetime can begin to be impacted by continuous running.

 

100% duty cycle means 100% duty cycle.... No?

I mean you can't run it more than 100% of the time....? Right?

 

When I buy electrical devices for a commercial purpose - they usually have a "duty cycle" stipulated. Small welding machines usually have this prominently shown on their sales docs. Many items are not able to operate at full capacity for a continuous period of time (that is 100%). Compressors like these little DC outfits suffer from over-temperature - insulation failure and so-on will occur if a rest period is not used to control heating. Manufacturers know people will push them and they usually have a self-resetting thermal "off" switch incorporated to save them from ultimate failure. Often these switches are not sufficient to protect the motors from having a reduced future life. The Viair in my truck has a high allowable pressure (150 psi) - but the stipulated duty cycle at that pressure is way less than 100%. The manufacturer rates it at 100% if the pressure is limited to 100 psi at 21 amps. I put a 85-105 pressure switch on my install so that enforcement of the limit is automatic - it never reaches any sort of thermal capacity limit. And 105 is plenty for pressure for my purposes.

 

Both duty cycle and high pressure will diminish lifetime. It’s made with small size as the main priority rather than durability. No way is any oil free compressor going to last a long time.

 

I finally got my OBA Kit installed.


I ordered a Viair 10007 Kit about 2 years ago as an Amazon Warehouse deal and got a killer deal on it ($260).

Originally, I wanted to keep it simple but it quickly evolved into over-engineered/over-built project (as many of my mods do).

Here was my goal:

• Mount the compressor, pressure regulator, relay and wiring inside the bedside cubby.
• Mount the tank under the bed, above the diff. (this changed)
• Mount the switch and pressure gauge on the bedside cubby cover

COMPRESSOR MOUNTING:
I'm cheap and did not want to buy or use the Expedition Essentials BCM. It's expensive and also leaves the cubby too exposed (no sealed/protected) to water and dust intrusion, so I decided to build my own metal cubby using 1/8" scrap steel. I had to make a few adjustments to the box to fit and make sure it won't hit the body, bumper, or bedside.

I also wanted to ensure the welded cubby left both sides open and accessible to make it easy when plumbing and wiring everything before install. This meant I had to make an external plate (on the exterior side, behind the bedside) that would be secured and also sealed to prevent water and other contaminants. This is the first version I built; I had welded little tabs with welded nuts that were inset. I eventually had to change the design to trim a corner that was hitting my bedside and opted to use rivet-nuts rather than welded nuts, just for simplicity and time-saving.

Here is a view of the backside (bedside) when I was figuring out the placement for everything:


Here's a view of the cubby cover after I roughed-in the switch and gauge:



EXTERNAL FILTER MOUNTING:

The Viair Kit came supplied with an external intake filter. I wanted to install that in the middle cubby on the Driver's side so the compressor was always pulling in clean air.

Side-Note: Anyone who's messed with the cubbies above the wheel-well(s) has probably learned how easily the mounting tabs can break. I had broken my tabs about 10 years ago and used some VHB tape to hold it in place, which was a temporary solution and never lasted. I decided to reinforce the cubby and made a thin metal backing-plate to mount behind the plastic bedside and the cubby to be bolted and secured. Of course, I dropped the cubby when I was messing around with it and broke the corner off (black plastic epoxy was a quick/ugly fix). I sealed up all the seams and holes in this cubby as well.

This is the reinforcement backing-plate and the cubby that I modified for the intake filter.


Here's the backing plate installed through the plastic bed. I used rivet-nuts to secure the small cubby to the metal plate itself:


External Filter installed:


TANK CRADLE MOUNT:
For the 2.5 Gal. Tank - I was originally going to just bolt that underneath the bed itself above the diff. as I'd seen done on my other OBA installs. There is definitely enough room there and it would be a fast/easy install, but I felt it was just too exposed and risked getting bashed/damaged when wheeling. I found I had just enough room to mount it directly behind the tow-hitch tubing on my H/C Bumper. This would keep it nestled up higher and more-protected from damage.

I welded up a metal "cradle" for the tank to nest in and provide more protection on the frontside and both sides. The welded cradle would then be bolted directly to the tow-hitch tubing on my H/C Bumper. The cradle itself was a pretty simple design but I had to get creative with mounting and bolting it up, since there's not a lot of room to fit my hands/arms around once the tank was in place.

Here's the beginning of the tank cradle as I was cutting and welding the pieces together:



The OEM tow-hitch tubing is 1/4" thick square tube with some addtl. 1/4" plating welded to (some sections) the surrounding center area of the tube. I planned to drill and tap (vertical) holes for the tank cradle to bolt-up to the underside of the tow-hitch tubing and add a couple (horizontal) holes near the top to run a bolt/lock-nut on the top portion. There was a section on the underside of the two-hitch tube that did not have the addtl. 1/4" plate welded, so I welded more material in those sections to ensure I had at least 1/2" of metal to drill and tap the 3/8-16 thread into.

This was a PAIN IN THE ASS!!! Overhead welding is always easy and fun (insert sarcastic emoji here) and then drilling tapping 1/2" thick welded metal proved to be quite a chore. I broke (3) cobalt step bit just drilling the holes and broke a (cheap) tap handle when it came time to tap the holes - but I got it done and it worked out great in the end.

I also countersunk the underside holes and used flush-mount bolts so there would be little-to-no risk of shearing or damaging the bolt heads when wheeling (dragging on rocks and messing up the heads).

Here's the tank cradle welded, reinforced and painted up:


Everything was coming together and ready for wiring, plumbing and final install!

WIRING & PLUMBING:
For the wiring, I ran a single 12v lead for the main compressor/pressure regulator to my aux. fuse block (w/ relay) using 10AWG THHN. I connected the switch power, pressure gauge illumination lead, and ground(s) to the OEM 7-pin harness behind the bumper and used a waterproof plug to connect them all to the same harness.

Here's a few pics showing how the wiring and plumbing were connected inside the welded cubby box (before bolting the outer plate on for final install). I used grommets and sealed passthroughs for all the tubing and wiring to ensure no water or contaminants could get in.

I will say that I was completely overwhelmed with options when I was searching for weatherstripping and tried a few different options before finding some good ones for the front and back. The weatherstripping is essential for sealing the mating surfaces and also to help reduce noise and vibrations when the compressor is running.

This view is from the interior, behind the cubby cover:



Here is a backside view, which will have the plate bolted/secured before final install:



I also opted to swap the normal halogen bulb for the pressure gauge for a red LED bulb (+10 cool factor )

Here's a view of the backside after securing the back-plate. It's ugly, but works exactly as I intended. Having the removable back-plate definitely over-complicated the build and added some complexity, but it made for a much easier install for all the wiring and air lines to have access front and back.


Underside view showing the wiring harness and airline fittings (one for the compressor-to-tank lead and one for the return to the pressure regulator relay):


Here's the cubby installed and ready to connect wiring and air lines:


I left about 14" extra length for the Power and Ground (for the switch) and air-line for the pressure gauge to be installed on the cubby cover and allow removal of the cover without having to disconnect anything:


Here's the tank mounted on the cradle, ready to bolt-up and connect all the lines:




Underside view showing the compressor mount and the tank:



For the quick-connect fitting, I used a bulkhead fitting from Wit's End and the ARB Q/C coupler mounted on an open/recessed portion of my H/C bumper:


I also got this little Bobby Ross keychain plug (just for fun) to ride along on the trails with us.
"Happy Little Trees"


Finished product:




All in - I spent about $350 (or less) for this install and it works GREAT; wayyyy faster than my trusty 11 year old Viair 88p!

I do have a small air leak somewhere that I need to track down, but that's small potatoes to fix.

 

What's the best thread sealant to use for fittings?


I've always used regular teflon tape, but thought I would get all fancy and use something better for the OBA install.

This is what I used:

$6 Rectorseal 25790 1-3/4-Ounce Tube No.5 Pipe Thread Sealant

https://www.amazon.com/dp/B0009PU9CK?ref=ppx_yo2ov_dt_b_product_details

I've found (3) of my fittings have small pinhole leaks even after curing for 48-hours, so I'm not too impressed with it.

I'm going to try this stuff next and redo all the fittings. It got really good reviews, especially for air compressor fittings with multiple connections/adapters:

$4 Mill-Rose 70885 Blue Monster PTFE Pipe Thread Sealant Tape, 1/2" x 1429"es, Blue

https://www.amazon.com/gp/product/B009YA09D0?ie=UTF8

 

Looks AWESOME and I'm sure labor intensive but the end result is

 

Thanks man!

There's definitely a reason why it took me nearly 2 years to get it installed.

 

The PTFE tape would be the best, make sure everything is clean and you are installing it properly. I work for Swagelok (tube/pipe fitting industry) and we use PTFE tape on all of our threaded end connections.

 

There are different thickness available. Could you please educate us on where they should be used and why?

 

Thank you for the feedback and real-world advice


I'll redo all my fittings with the PTFE tape and should be good to go!

 

Could be per application, but also probably the pressures you’ll be seeing. We only have one thickness that we use, I can’t think of what it is exactly right now

 

Well this is interesting. My ARB twin quit working the other day. Upon investigation, I found that the two power wires had both melted on the battery side of the fuse holders.

Anyone else ever have that happen?

 

A few pages ago

 

Hi there, can I ask a dumb question?

$337 ARB CKMA12 On-Board Air Compressor High Performance 12 Volt for Air Locker Differentials and Tire Inflation

ARB CKMA12, setting up 3-4 quick disconnects.

3/8" nylon tubing with push on connections vs ARB steel braided PTFE hose and JIC-04 connections?

Nylon will be cheaper, but is there a trade off in longevity, reliability or leaks?

Any other suggestions I should consider?

Thanks!

Lyle

 

Sticking a $500-600 compressor in a hot ass, dirty engine bay can't help the melting situation either. Never understood the logic of this, I guess it's an "overland" thing.

 

When you mounted yours where did you put your manifold for the locker solenoids? I put mine under the hood where I can get at them not back in my wheel well.

 

not an overland thing. just a matter of preference. theres multiple locations where people mount them. where is yours?

 

Mines under the passenger seat on a desert does it mount.