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Red_Chili
06-12-2008, 11:48 AM
As some of you know, I run two MV50 compressors hardwired on my truck for an OBA system. I have been pleased with them overall, though there are some caveats:
-the internal relay is weak. It failed on one of the compressors after a year. No worries, I activate them with external relays switching 30A circuits, so they (and the on/off switch) are entirely redundant. I bypassed them.
-they do not use standard 1/4NPT fittings. They tap out easily though, and my system is running 1/4" fittings. Some have cracked the compressor head by forcing the SAE fittings in, so tapping first is advisable.
-the pressure gauge clouds over after a while. No worries, my application has them under the hood. No wonder. The gauge is pretty darn accurate, though it shows a higher pressure when the compressors are running if you keep it in the as-shipped configuration.

Some regard these compressors as junk. I don't based on 2-3 years usage, probably pushing the duty cycle on them. They were cheap at $25 closeout pricing at Checkers, but of course that is history. They are still pretty affordable at about $60.

But lookee what I found:
http://www.amazon.com/gp/product/B000L9AD2U
Same compressor as the MV-50. Really. Part for part.

Take a look at the small print.
2 used & new (http://www.amazon.com/gp/offer-listing/B000L9AD2U/ref=dp_olp_2) available from $5.00I figgered the $5 was for some part, or perhaps a mistake. Clicking the link, no, it is for the whole compressor, new. Must be a mistake, thinks I. So I call the guy.

Nope, that is the price! He did that for some internal Amazon reason to move up to the head of the list. He charged outrageous shipping ($10), but that only brings the total to around $15. Delivered. No kidding. He must have bought a refused shipping lot or something (they seem to sell all kinds of unrelated stuff, some junk, some not), or a bankruptcy purchase, but he is a real vendor selling these at $14 delivered and he makes money doing it.

I ordered two. Part of me thought about buying him out and reselling them to the 4x4 community, but I beat that part of me back into the dark hole from which it came.9356

9357
You're welcome.

Enjoy.9358
Killer deal.

DaveInDenver
06-12-2008, 12:00 PM
Fantastic deal! But he's got a rating of zero based on 2 transactions, both negative feedback. :-/

Red_Chili
06-12-2008, 12:20 PM
Read the reviews. The second guy was clueless. Yet he got a response. The guy is a new vendor, I talked with him at length, decent fellow and he made a point about assuring me it would be shipped immediately (though I did not ask about that) so he takes the feedback seriously - and you are risking $15 covered by Amazon's support.

And I bought it on a credit card. With the attendant safety net.

I am not a betting man, but I took this bet.

DaveInDenver
06-12-2008, 12:41 PM
Seems like a reasonable bet to me, particularly since you talked to him on the phone.

JadeRunner
06-12-2008, 01:06 PM
I just bought one. I got in on the 50$ deal a while back also. It's a fine compressor, 15$ is too hard to pass up.

Hulk
06-12-2008, 01:14 PM
Bill, how long does this take to fill a 35" tire from 15 to 30 PSI?

Crash
06-12-2008, 01:15 PM
Rolling the dice on two of them. For $25 a pair, what the heck? Thanks for the heads up Mr. Chili!

Chris
06-12-2008, 01:23 PM
Jumping on this too, thanks Bill.

Edit: The $5.00 offer isn't available after placing my order, hope I got the last rather thank getting skunked.

Red_Chili
06-12-2008, 01:34 PM
Bill, how long does this take to fill a 35" tire from 15 to 30 PSI?
Not timed them, so I will compare to others using CO2 at the same time.
CO2 is faster of course. It is also more trouble: I kept running out at an inconvenient time, and of course had to haul the bottle around. I got tired of camping in the back of the truck and resting my leg against a COLD bottle in the middle of the night. And got tired of having it take up space.

Anywho, one by itself is leisurely filling up a 35" tire. CO2 does it in about 1/4 of the time. But it will do it. Not a choice for the terminal type A's who just have to get the *&^&& off the trail and go home. Find the Zen, d00d. Breathe in, breathe out, breath in....

Two is a bit different. I went with two because, after all, it is a cheap compressor. Redundancy makes sense especially since they power my lockers too. But aside from the internal relay mentioned, they have been stone reliable. IIRC one of them still has the internal relay. I'll have to bypass it some day.

Regards speed, two will fill a 35" tire a bit slower than a CO2 bottle. Three tires are nearly done when the CO2 guy is putting the valve cap back on his fourth. Or so. I can live with that. Even on my type A days.

Some have gotten compressors that are bad out of the box. You expect that with this kind of thing. Return it and get another.

If you hardwire them, choose your wire gauge generously: they use 30A each. Fuse each circuit, or use a breaker. Make sure your charging system is up to providing 60A auxiliary.

Red_Chili
06-12-2008, 01:38 PM
Jumping on this too, thanks Bill.

Edit: The $5.00 offer isn't available after placing my order, hope I got the last rather thank getting skunked.
Wow. Sho' nuff. Gone. Interesting.

Maybe Amazon figured out the guy was seriously undercutting their own product. He did say the Amazon folks told him they could hardly keep up with the orders.

Well, even at Amazon's price you would have a hard time besting it dollar for dollar.

Red_Chili
06-12-2008, 02:09 PM
If you want to contact the guy, the phone number for DLF Explorers is (314)-791-1273 in St. Louis, Mo.

Maybe he sold out!

Crash
06-12-2008, 06:39 PM
Oh well, it was worth the try....just got a confirmation email from Amazon.com that DLF is unable to fill my air compressor order at this time and therefore cancelled. Thanks for trying Bill!

Chris
06-12-2008, 06:54 PM
Yep, mine too. I hope you get yours Bill!

Red_Chili
06-12-2008, 11:05 PM
I will, I got the confirmation. Geez, now I feel guilty! Do you guys need one? I was just buying spares.

rover67
06-12-2008, 11:52 PM
oh dang, that sucks. I am already looking to get some kind of compressor setup to replace my CO2 tank... this woulda been sweet.

Red_Chili
06-13-2008, 08:39 AM
Still a good deal at under $60 with free shipping though! Very surprising compressor. Don't care for the fittings but they are easy enough to change. Got tap?

RockRunner
06-13-2008, 09:47 AM
I run that same compressor just by itself and to inflate my 37's from 10 to 30 takes about 6-7 minutes. The compressor works great for what it is, my one complaint about it is the heat.:(

After filling 4 tires the hose disconnect gets super super hot. First time I used it I literally burned mu thumb and pointing finger:mad:. Not really bad but bad enough that three days later I still had some pain.

I bought mine at Costco for $49.99, now they are a little more expensive. I think they are the same if you have them shipped or buy local unless you get in on Bill's deal...........I didn't :(

Bill one of these days I am going to install a system similar to yours.... just need another compressor and a small tank.

Red_Chili
06-13-2008, 10:01 AM
Use your bumper tubes. WFLLT.

RockRunner
06-13-2008, 10:16 AM
I have thought about that and may do that. Not to sure right now what way I will go, I want to add a "new" front bumper sometime so that could hold air too. We'll see, right now I'm doing nothing to the truck except for changing the tires to 35"s to save my 37's and some gas ;-)

DaveInDenver
06-13-2008, 11:14 AM
Use your bumper tubes.
Go figure, never been a fan of doing this on bumpers and sliders. Material ratings assume minimal uniformity and wall thickness and rust, dents and gouges compromise that. Seems to me that you need to consider these things. Not to mention how the caps are made and welded on and the shape of the vessel, just too much variance for my comfort. Reactive armor, indeed.

Admittedly, at 150 psi a bumper is really unlikely to explode like a SCUBA tank or gas cylinder at 2000 psi, but the chance for a failure is there. If you think 100 or 150 psi isn't much, consider what happens in a tire blow-out, how much junk is thrown everywhere and that's only 35 psi on a relatively elastic material. That's also why they inflate split rims in cages.

OTOH, I'm not aware of people's bumper-receivers blowing out, so I dunno that it's much of an imminent concern. Suppose it's just one of those things that sketches me out. I also get irrational willies when the dental hygienist starts picking my teeth and I've given myself plenty of dinged fingers and palms inflating road bike tires. I used to think the Marines should think about throwing inflated Continental Gatorskins at the enemy instead of grenades.

Red_Chili
06-13-2008, 01:30 PM
With apologies to RR, "there you go again..." :D

No issues since I've used it. The bumper tubing is not very thin. 100psi max. Some day I will put in a drain though. But it is only active off-road, otherwise depressurized.

Crash
06-13-2008, 01:46 PM
Saw that the Amazon link was posted on MUD back on Sunday or Monday so it is no surprise now that they were sold out by the time we RSers gave it a shot.

DaveInDenver
06-13-2008, 02:16 PM
With apologies to RR, "there you go again..." :D

No issues since I've used it. The bumper tubing is not very thin. 100psi max. Some day I will put in a drain though. But it is only active off-road, otherwise depressurized.
Sure, maybe. So I looked into it.

ASTM A53 schedule 40 carbon thin wall pipe in 2" diameter is rated to 230 psi working pressure (but that's at 400 degrees F with threaded joints). Schedule 40 2" is 0.154" wall thickness. A welded 2.5" Sch. 40 is 553 psi, which would have a wall thickness of 0.203".

So how does a 1.5" DOM 0.120" tube stack up? If you use an ultimate strength of 60 ksi, that seamless 1.5" I think should have a bursting pressure of 8,400 psi. But I dunno the safety factor you'd have to use to find working pressure that allows for rust, dings and scratches. But even allowing a 10x safety factor you're still at 840 psi.

FWIW, the formula I have is:
P = 0.875*{(2Y*t)/D}

P=Burst Pressure in psi
Y=Yield in psi
t=Wall thickness in inches
D=Nominal OD in inches

But HREW is significantly lower, about 35 ksi. That puts HREW with certified welds at a bursting pressure of 4,900 psi and use whatever safety factor you want. So how do you derate for gouges, dents and non-uniformity? I dunno, so maybe Nakman or Bruce can fill me in. Using 25 ksi for carbon steel pipe with 0.203" wall and 2.5" OD, that yields a bursting pressure of 3,550 psi and so using the ASTM table working rating of 553 psi, apparently they use about 6.5x factor of safety. So 1.5", 0.120" HREW would apparently have a working pressure of 750 psi. My fears are probably way off base.

Crash
06-13-2008, 02:28 PM
DID, you ARE the Ultimate Goober. Now if we can get you to do an Ultimate Warrior impression around the campfire in CA we will be ultimately blessed!! :D

Sure, maybe. So I looked into it.

ASTM A53 schedule 40 carbon thin wall pipe in 2" diameter is rated to 230 psi working pressure (but that's at 400 degrees F with threaded joints). Schedule 40 2" is 0.154" wall thickness. A welded 2.5" Sch. 40 is 553 psi, which would have a wall thickness of 0.203".

So how does a 1.5" DOM 0.120" tube stack up? If you use an ultimate strength of 60 ksi, that seamless 1.5" I think should have a bursting pressure of 8,400 psi. But I dunno the safety factor you'd have to use to find working pressure that allows for rust, dings and scratches. But even allowing a 10x safety factor you're still at 840 psi.

FWIW, the formula I have is:
P = 0.875*{(2Y*t)/D}

P=Burst Pressure in psi
Y=Yield in psi
t=Wall thickness in inches
D=Nominal OD in inches

But HREW is significantly lower, about 35 ksi. That puts HREW with certified welds at a bursting pressure of 4,900 psi and use whatever safety factor you want. So how do you derate for gouges, dents and non-uniformity? I dunno, so maybe Nakman or Bruce can fill me in. Using 25 ksi for carbon steel pipe with 0.203" wall and 2.5" OD, that yields a bursting pressure of 3,550 psi and so using the ASTM table working rating of 553 psi, apparently they use about 6.5x factor of safety. So 1.5", 0.120" HREW would apparently have a working pressure of 750 psi. My fears are probably way off base.

DaveInDenver
06-13-2008, 02:34 PM
DID, you ARE the Ultimate Goober. Now if we can get you to do an Ultimate Warrior impression around the campfire in CA we will be ultimately blessed!! :D
Just reading tables, I dunno if it's right. It's something that's always sorta bugged me in the back of my mind anyway, so this thread just got me off my rear and I walked over and flipped through one of the mechanical guy's books.

Red_Chili
06-13-2008, 03:05 PM
Dave, you worry me. Do they have medication for that?
9382

But regards the particulars:
9383

nakman
06-13-2008, 03:13 PM
Are you saying I'm knowledgable in gouges, dents, and non-uniformity? or in Nayspeak, GDnU? :lmao:

I do actually have experience in gouging sliders, and denting things... and I do lack uniformity in most areas. And I'm using one of my sliders as air storage too. But like Red Chili, it's non-pressurized more often than not, and I only "use" it when the OBA system is kicking, just for a little more buffer between tires and a little more storage when I shut it all down.

But to your point about how powerful is 100 psi.. yes it's significant, and a sudden burst from a bumper or slider would make one hell of a noise, and blast whatever was in its path with some fast-moving cold air. It worried me too, but when I posted the question everyone told me just tap the thing and don't worry about it, including the guy who sold me the sliders. So far, that method has proven reliable.

DaveInDenver
06-13-2008, 03:20 PM
Dave, you worry me. Do they have medication for that?

Oh yeah they do.

http://blogs.menupages.com/sanfrancisco/simpson-duff-beer-internet-homer.jpg

And for no particularly relevant reason other than I came across it.

http://earthfirst.com/wp-content/uploads/2008/04/beer.jpg

Uncle Ben
06-13-2008, 03:38 PM
Are you saying I'm knowledgable in gouges, dents, and non-uniformity? or in Nayspeak, GDnU? :lmao:

I do actually have experience in gouging sliders, and denting things... and I do lack uniformity in most areas. And I'm using one of my sliders as air storage too. But like Red Chili, it's non-pressurized more often than not, and I only "use" it when the OBA system is kicking, just for a little more buffer between tires and a little more storage when I shut it all down.

But to your point about how powerful is 100 psi.. yes it's significant, and a sudden burst from a bumper or slider would make one hell of a noise, and blast whatever was in its path with some fast-moving cold air. It worried me too, but when I posted the question everyone told me just tap the thing and don't worry about it, including the guy who sold me the sliders. So far, that method has proven reliable.

I had both sliders on Long Grain tapped and pressurized to 100#+. Never an issue! I thought ahead and put ball valves on each tank at the air manifold so I could isolate either or both tanks in case something happened. I actually used the valve to shut off the passenger side slider when I hit the slider hard enough to bend the frame support. It simply pulled a small bit of weld and created a Pssssssss. For a steel tank to rupture bad enough to cause a explosion would take enough of an impact that the boom will be the last of your concerns! Of course a factor that has to be considered would be crappy welds on the caps!

Seldom Seen
06-13-2008, 05:04 PM
Just reading tables, I dunno if it's right. It's something that's always sorta bugged me in the back of my mind anyway, so this thread just got me off my rear and I walked over and flipped through one of the mechanical guy's books.


OMG, that reminded me of an old joke that few can appreciate.

A mathematician, physicist and engineer are asked to find the volume of a red rubber ball.

The mathematician measures the dia of the ball and sets to cyphering
4/3πr.........

The physicist drops the ball in a graduated cylinder and measures the displacement....

The engineer pulls out his table of little red rubber balls :lmao::lmao::lmao:

Red_Chili
06-14-2008, 09:26 AM
Well, I ain't getting my compressors after all. Late to the ball. Just getting a refund.

The post on Mud probably killed it.

DaveInDenver
06-14-2008, 09:38 AM
Man that stinks, you even talked directly to the dude.

Red_Chili
06-14-2008, 10:04 AM
Yeah, but he didn't know the pipeline of orders he was about to get deluged with. I was just at the end of the line. Such is the web.