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DIY not-a-Power Tank

Posted: Fri Mar 30, 2018 12:00 am
by Low_Sky
After years of inflating tires with a puny portable Viair 85P, I decided I needed to upgrade after after my in-dash 12V outlet died. The 12V outlet in the center console still works and I'm keeping the 85P as my always-in-the-truck back-up, but I wanted something more reliable to count on using on the trail.

I went back and forth between CO2 and on-board air for a long time before I settled on CO2. I like that it's portable, fast, quiet, reliable (as long as you pay attention to how much is in the tank), and requires no modification or full-time real estate in the truck.

Power Tank is the big name in CO2 tanks for off-road, and holy crap are they proud of them. If their published flow rates are accurate, their regulators are where all that "power" comes from, but I couldn't justify their cost. A whole tank/regulator/hose setup from them is in the $500 ballpark before whatever their astronomical shipping to Alaska would be.

I went the cheap DIY route. I ordered an aluminum 15# CO2 tank from a microbrew supplier online. You can find these all over the internet. I chose my particular vendor because of their this-must-be-a-mistake cheap shipping to Alaska. $90 for the tank, $21 for shipping, can't beat that. Aluminum tanks bigger than the 5# tanks the home brewers use are impossible to find in Alaska, so I had no choice but to order out.

For a regulator, I ordered a Gentec model 227C-150. This is a ~$40 China-made fixed pressure regulator with no gauge. It's sold by a number of off-road shops with no brand, but you can find it more places by googling the model number. The cheapest place for me ended up being Amazon thanks to free shipping.

The regulator has a 1/4" FNPT outlet port, so from there it's a matter of attaching your favorite combination of hose and fittings.

My local welding gas supplier "serviced" and filled my tank for less than $40. It took them 5 days to turn it around because they don't fill on-site, but at least I got my rare-as-hen's-teeth aluminum tank back. I'm going to keep looking for a place that can fill same day for an agreeable price, but if I can't I might get a second tank so I don't get sidelined for a weekend waiting for a re-fill.

Now for the good stuff, fill times. 20 psi to 45 psi in a 35x12.5r17 tire on a 40F day.
My shop air compressor with 150 psi in the 5 gallon tank: 1:52
CO2 w/$40 Chinese regulator: 3:57 (it's comparable to or marginally faster than the published inflation time for a Viair 450)
Viair 85P (I call it "Putt Putt"): 7:45
Just for fun, my Staun HD deflators let that 25 psi out in 3:45.

My endless googling suggests this tank should take me from trail to street pressure five or six times before needing a re-fill. I'll try to keep track and report back with the actual number.

If I'm feeling froggy, I might jump on a knock off PT-style handle and hi-flow regulator set on ebay. If I do that and the regulator is worth keeping, I'll try to perform a "port and polish" surgery on the $40 Gentec and see if I can speed it up any. It's nowhere near Power Tank fast, but for the cost I didn't expect it would be.

I'll try to take and get pictures up tomorrow when it's light outside.

Re: DIY not-a-Power Tank

Posted: Sat Mar 31, 2018 10:03 am
by olyelr
Nice job!

I have considered a Powertank, but for the cost I figure I might as well just go with on-board air. Nowhere near as fast, but I wont have to bother filling up CO2 tanks ever either.

Re: DIY not-a-Power Tank

Posted: Sat Mar 31, 2018 10:19 am
by Low_Sky
Yesterday I tore apart the inflation gun and did surgery on all the flow ports. There was room to open things up quite a bit. I also swapped the closed-flow clip on chuck for an open-flow screw-on chuck. Those two changes cut the inflation time in half.

I did have to return the high-flow quick connects I was using. They felt cheap, and sure enough they leaked unless they were lined up perfectly straight. I haven’t put together the 1/4” industrial quick connects I got, but if they restrict the flow much I may work on them too.

I took apart the regulator and found that the supply side piston seat is very small and doesnt leave much material to open the flow path up. I’d be able to go up one drill size at most, so I probably won’t mess with it. The small gains available don’t seem worth the risk of ruining the regulator.

Re: DIY not-a-Power Tank

Posted: Sun Apr 01, 2018 6:07 pm
by nts007
Sweet!! My onboard air system is nitrogen. I like you're resourcefulness for a tank!

Re: DIY not-a-Power Tank

Posted: Sun Apr 01, 2018 6:31 pm
by TwinStick
Nice job ! :rockon: I have a small 3 gal Craftsman air compressor in my garage & recently added a 7 gal tank to the system. Holy cow, what a difference that made. I have a 5 gal tank for my truck, if i ever get around to the install. I plan to use it with my battery operated portable Ridgid compressor, or my Husky 3 gal, 120v compressor into the inverter. I already made up the male end/male end hose, to go from compressor to tank.

Re: DIY not-a-Power Tank

Posted: Sun Apr 01, 2018 10:58 pm
by Woodscavenger
I went with OBA as well. Just used it this week down near Kanab Ut for Peek-abo trail that kicked my butt last year in a sequoia. This year we just floated. Took pressure down to 22# with deflator (easy and simple) then aired up to about 50# and drove to town to finish off the pressure to 65#. It took me about 10-15 min to inflate. I have stock 33s. Worked awesome. I have a custom bracket to hold my tank to the bed wall under my Flip top tonneau. Last year with the sequoia I was aired down and used 2 little 12v pumps and it took about 45min to get up to 30#.

Re: DIY not-a-Power Tank

Posted: Mon Apr 02, 2018 5:59 pm
by nts007
Low sky what's the full tank pressure after filled

Re: DIY not-a-Power Tank

Posted: Mon Apr 02, 2018 10:37 pm
by Woodscavenger
I think they can fill those to 150psi

Re: DIY not-a-Power Tank

Posted: Tue Apr 03, 2018 2:55 pm
by Low_Sky
nts007 wrote:
Mon Apr 02, 2018 5:59 pm
Low sky what's the full tank pressure after filled
There isn't an easy answer to this one thanks to CO2's physical properties. Below 88*F, there is liquid and gas phase CO2 in the tank, and the pressure will be equal to the vapor pressure of CO2 at the temperature of the tank. As you use the CO2 gas from the top of the tank, the liquid will change phases to gas to keep the pressure constant. Once all the liquid the is gone, the pressure in the tank will decrease with use as you would expect. For example, at 0*F you have 300 psi in a full tank. Warm up that same tank to 80*F, you have about 925 psi. Above 88*F, the CO2 is a supercritical fluid with properties of both gases and liquids, but that's mostly academic and doesn't really impact this application. The master valves on the CO2 tanks come with a safety burst disk that vents the tank if the temperature/pressure get dangerously high, I think most are 2000 psi.

The whole liquid/gas phase thing is why these tanks can be stored in any orientation, but need to be used standing up, so the gas is drawn off the top of the tank.

The best way to determine how much CO2 you have left in the tank is by weight. If you wait until the supply pressure starts dropping, you're out of liquid CO2 and the tank is pretty much done at that point.

Re: DIY not-a-Power Tank

Posted: Wed Apr 04, 2018 11:39 am
by 13BlkPowerWagon
Maybe I'm being too cautious, but I'd want some kind of cage/protection around that stem. No?

Re: DIY not-a-Power Tank

Posted: Wed Apr 04, 2018 12:19 pm
by Low_Sky
13BlkPowerWagon wrote:
Wed Apr 04, 2018 11:39 am
Maybe I'm being too cautious, but I'd want some kind of cage/protection around that stem. No?
You are not wrong, but there are not a lot of options out there for that. The plastic handle/cages that come on most beverage bottles wouldn't fit on my tank even if I could find one for sale by itself (they're retained by a snap ring, my tank does not have the snap ring groove and I think the neck is the wrong OD). PT's handle is cost prohibitive once shipping is factored in. That leaves me with the ebay rip off option or making something myself.

Re: DIY not-a-Power Tank

Posted: Wed Apr 04, 2018 2:07 pm
by adeluca73
Low_Sky wrote:
Sat Mar 31, 2018 10:19 am
Yesterday I tore apart the inflation gun and did surgery on all the flow ports. There was room to open things up quite a bit. I also swapped the closed-flow clip on chuck for an open-flow screw-on chuck. Those two changes cut the inflation time in half.

I did have to return the high-flow quick connects I was using. They felt cheap, and sure enough they leaked unless they were lined up perfectly straight. I haven’t put together the 1/4” industrial quick connects I got, but if they restrict the flow much I may work on them too.

I took apart the regulator and found that the supply side piston seat is very small and doesnt leave much material to open the flow path up. I’d be able to go up one drill size at most, so I probably won’t mess with it. The small gains available don’t seem worth the risk of ruining the regulator.
Sweet DIY!! But at nominal CO2 pressures with vape pressure increase as function of temp, I'd be worried about that tank turning into a missile in the back of the truck. I can't do anything about the one riding around the driver's seat ;) , but I'd probably try to sequester that manifold from unintended jouncing while hittin' it off-road.

Re: DIY not-a-Power Tank

Posted: Wed Apr 04, 2018 2:26 pm
by Low_Sky
adeluca73 wrote:
Wed Apr 04, 2018 2:07 pm
Sweet DIY!! But at nominal CO2 pressures with vape pressure increase as function of temp, I'd be worried about that tank turning into a missile in the back of the truck. I can't do anything about the one riding around the driver's seat ;) , but I'd probably try to sequester that manifold from unintended jouncing while hittin' it off-road.
PT claims that CO2 tanks "don't" turn into missiles, but I'm not about to fact check them on that. The Quick Fist and hardware I made for the RamBox track seems sturdy enough, but if it bounces around too much for my liking I'll spring for a proper fire extinguisher mount. When it goes in the truck, it's up at the front of the bed, boxed in by my RamBox divider and fuel cans, so nowhere to go but straight up if the clamp lets go for some reason. .

Re: DIY not-a-Power Tank

Posted: Wed Apr 04, 2018 5:06 pm
by Bill2014
What goes up - will eventually come back down. :o
Do you happen to have a moon roof???