Service Jeep -- OBA & OBW

a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
Two ongoing/future projects for my rolling shop XJ:

On Board Air (nearly complete)
- Greased Sanden 709.. fairly simple to do, but time will tell how long it lasts. I attempted a oil sump in it but it kept blowing by the rings. So I slapped grease in the bearings and it hasn't blown grease out.. Thinking I may add a inline to lube the piston/cylinders.
- Scavenged check valve, decompression, pressure switch
- Needs switch in cab and air tank

I plan on using the rear bumper which should be 2gal or the old tank 17gal.. but I'm having trouble finding a spot to put a 17gal tank inside my XJ.. Thinking of mounting it out front.. Really I need to test the CFM of the Sanden at 2500 rpm and see if I need that big of a tank.. 3/4" impact would be nice taking nuts off harrows in a field. Read somewhere it is supposed to flow 9cfm/1000RPM but that is not under load.. atmospheric to atmospheric flow.. derating it, I would guess I am looking at probably 4-5CFM at 90 at 1000rpm, or 7-9 CFM at 2500 rpm.

On Board Welder
- Start with 90A stock, then upgrade to 136A Durango/Grand Cher Alternator, conveniently externally regulated -- really surprised no one has used the NipponDenso alternators for weldernators, no internal rectifier like the Delco's.
- Bypass/Control Box CC/CV -- this is where the complex part is. constant current is easy (stick/tig). constant voltage like for MIG/FCAW is a little bit more circuitry, although definitley do-able.
- Spool gun/Stinger/TIG/outlet for grinder

I figure I have a 90A HF FCAW and it does 3/16 OK so I should at least be able to get that kind of performance out of the stock alternator. I've not done a whole lot of stick welding, but all that one needs to do stick is to remove the two field wires off the alternator and drive it with 12v on one side and ground through 1-10 ohm variable resistor, hook the stinger to the power output and you have a constant current source, and control the revs. Not fancy but should do the job. I am researching whether the stock rectifier is an avalanche type(limits the voltage before the magic smoke is released), if the rectifier is upgradeable to non-avalanche, or if I need a custom external rectifier. I mainly would use it out in the field on farm equipment or somewhere where there is no mains power and then I don't need to bring a generator to run my welder. (Side note: 3kw generator will not run my welder at high/top wire speed.. it bogs and doesnt put out enough current to keep the wire hot) I have run the 220 HF WFW off a 8kw genset and that worked nice.. just ask the cows that got loaded with what I built.

Pictures forthcoming. (and I'll throw a couple in of the tool boxes.. everyone that has seen it likes it so far, {junkyards, shops, etc})
 
Used the OBA today, without a tank.. Had a tractor tire to inflate from flat, took about a minute to air up with rev's probably around 2k, never looked at the tach. I intend to use the cruise control servo to control RPM when the pump kicks on, and idle down when the pump is not running. My customer was really interested at it after the tire was inflated.. (of course my pump makes a racket because it was seized and the bearings are worn, but hey, I didnt spend anything except a hour to free it and grease it) I found some air leaks from the wrong size clamps that I need to address.. I wished I had the 17gal tank and a 3/4" gun today.. I'll wager the bolts were around 400-600 ft-lbs. (OBA Link about greasing/overall install http://www.jeepforum.com/forum/f12/sanden-709-oba-write-up-1314564/ ) Total OBA cost.. probably $20 in fittings, hose I had, a junk compressor, and a good afternoon.

OBW Field Controller will probably be copied / based off http://diy-welder.com/simple.shtml
My controller will include a contactor (for stick/FCAW) and rev on the torch/stinger handle.. kind of like the Zena, except mine will change back to charge mode at the flick of a switch. (and for less money, but time is money.. just depends on which you have more of.)
 
I'd be interested in seeing how well the greased sanden holds up. I've had medium luck just squirting pump oil in the inlet before use but they get hot.
 
Oh, compressing air still makes heat. I originally would have preferred to mist oil it but I wasn't going to fork over what they want for oilers and separators. Mine was ~110 F to the touch after filling that tire, but so was about everything mounted to the motor. The discharge air line was noticeably warm and it is 3 foot from the compressor near the hood prop, so the pistons still make heat. I'm going to wager that the piston rings will tear up before the bearings without lube. Probably mist oiling is the way to go because it is closest to the original application where the refrigerant carries the oil and lubes the cylinders and rings, blowing by and lubing the bearings and sucked back through the suction port (at least as I understand the flow).
 
I've got one foot of copper coming off the compressor.. turns out it really does generate quite a lot of heat.. I capped and plumbed in my rear bumper to find out it has air leaks, needing to run the die grinder some, and behold, 10 minutes into grinding and waiting on the pump, my pvc/rubber line blew off the barb on the copper from the compressor (even the rear bumper was getting warm to the touch).. well, I acquired enough 1/2" soft copper to replace all the hose so that should end the blowing lines.
 
Almost a year later, I changed out one of my tool boxes for a new one with more drawers roller slides instead of the cheap crimped-hard-to-pull-with-40lbs-in-the-drawer. (only now, parked on a hill the drawers want to run away after unlocking it). greased sanden still pumps air, has not seized yet (though it was seized when I greased it so it is noisy and will be replaced).. and the air compressed by a greased sanden WILL smell like grease, even after going thru an impact gun. still have not gotten to add idle control or OBW. dime on top of the idle set screw sets idle ~2k, stab the gas and the dime falls out.
 
I was going to add a second alternator for the obw, but instead of using a modded delco, most nippon-denso alts (stock chrysler parts) are externally regulated. (Or use a relay to switch the field from computer to manual and use the stock alternator and throw the spare alt under the backseat)
 
OK so the greased sanden died this past year.. The seals wore out. It was impressive when it got real hot and I tried adding lubrication through the suction port... Think diesel engine. I'm looking for a York now. It would've lasted a long time just airing tires up.. It did not like being ran for an hour at a time.
 
Back
Top