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Author Topic: Outboard Air Compressor  (Read 4166 times)
PCC
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« on: January 27, 2013, 01:50:37 PM »

I have some questions about the concept of having an air compressor, generator or self  powered, in addition to the engine mounted unit.

Does the air have any amount of lubricant in it, or is the compressed air "dry"?
Using the appropriate check valves, I would feed the auxiliary air into the wet tank?
What, on average, would the CFM requirement be, to operate a vehicle if the engine unit failed?

I am floating some ideas, and look forward to learning.

Thank you
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Ralph7
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« Reply #1 on: January 27, 2013, 04:03:59 PM »

     I have a compressor tied into the ping tank, it needed a a motor change, was 240V X 3600RPM went to 120V  and it draws 17A at 90 PSI. I think the tank icut it off of stated 5CFM @ 90PSI, so it would marginal.
   I use it in campgrounds to keep engine run time down.
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bevans6
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« Reply #2 on: January 27, 2013, 04:11:03 PM »

I wrote up a whole thing about how it's illegal to run the air brakes on a non DOT approved compressor, but decided not to post it.

Brian
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robertglines1
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« Reply #3 on: January 27, 2013, 04:18:24 PM »

Brian is correct. Must consider if compressor is broken it might damage your whole gear train then your out big bucks and engine take down. Tow trucks supply air to release brakes thru a port usually in front compartment that is often run thru a on board air filter.  FWIW   Bob
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« Reply #4 on: January 27, 2013, 04:29:53 PM »

looked at you profile. Can't tell by picture. What engine you running? 60 series fuel pump runs on back of air compressor. 2 stroke detroit prob gear drive so if it quit woud put whole gear drive in danger? Unless govner problem.
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wayne
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« Reply #5 on: January 27, 2013, 04:35:08 PM »

If you do use another compressor, even if it is only for campground use I would plumb it through a filter or at least through the air dryer. I plan on plumbing one into mine so I can use air options while parked. I haven't found one quiet enough yet.
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« Reply #6 on: January 27, 2013, 04:49:13 PM »

Wayne;looked in one like dentist used but they are noisey also. Still looking-- have tried box store ones(have now). If you find answer please post.  Bob
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« Reply #7 on: January 27, 2013, 05:20:54 PM »

There are specific quiet compressors but I always shuddered at the cost.  I have insulated my water bay, and if I put the air compressor in there it is acceptable both inside and outside, in that I can't tell it it's on from 20 feet away.  I plumb mine in at the ping tank on my MCI, that is directly downstream of the engine compressor and before the air dryer.  Only thing is you need to adjust it so it doesn't make the governor cycle the air dryer or all the air from the compressor dumps out.  That means all the air goes through the air dryer so you just need to adjust for that.  The only thing I use it for is to keep the suspension up, which takes almost nothing on my bus, and to get air up if I want to do a polite camp exit early in the morning.

Actually they are coming down in price:  http://www.homedepot.ca/product/6310-10-hp-63-gal-ultra-quiet-oil-free-steel-tank-air-compressor/998791

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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Oonrahnjay
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« Reply #8 on: January 27, 2013, 07:09:37 PM »

   I wrote up a whole thing about how it's illegal to run the air brakes on a non DOT approved compressor, but decided not to post it.   
Brian 

     And experience has shown it's not smart.  Can/should you use it to run down the road?  NO!  If you are having air problems at a fuel stop and you want to get enough air to move your bus away from the fuel pumps?  Probably OK.  Do you want to run air tools or adjust air pressures in tires before you start out in the AM?  That's OK.  Do you want to "air up" before you start the engine so you don't sit there at high idle early in the AM in a crowded campground?  Yes, that's OK (but you should move to a remote location and check that your engine-powered system is working correctly.) 
      There are a number of good reasons to have your own independent air system but driving on the road (unless it's a genuine life-and-death situation and you're watching gauges like a hawk) isn't one of them.  (There are also issues of size, weight, and complication but those become issues of how things fit into your own bus and your personal preferences, so that's another aspect.)

      BH  NC   USA

     
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Ed Hackenbruch
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« Reply #9 on: January 27, 2013, 08:28:06 PM »

 I have a Westward model 3JR85D portable air compressor that i bought a Grainger in Phoenix 9 years ago. Fairly quiet, real quiet, when i close the bay door. Grin
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« Reply #10 on: January 29, 2013, 06:36:47 PM »

Thanks to all for the information. I am not replacing/removing the engine unit, just adding an electric compressor to keep suspension functioning, doors and other air functions.

I have a mid engined coach (8V92), but it takes a while to bring up all 7 tanks when I have been using stuff for a week or so or after draining the tanks during a long rest-over.

Again I ask, does the compressor add any lubricant?
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« Reply #11 on: January 29, 2013, 06:57:40 PM »

Does the compressor add lubricant?

Not really.

Any oil that gets by wearing/worn rings in the compressor drops out into the discharge muffler, or the air drier, or the wet tank.

What are you concerned about lubricating?

Busnuts are right to think about air system valve lubrication. We inherit coaches that have been run hard and put away wet, and then we let them sit and sit and sit, what ever lube remains in the air valves has a bad habit of not lubing anymore without he rigors of daily operation keeping those old parts moving.

A schedule of rejuvenation/replacement of the air system valving is a worthy goal.

happy coaching!
buswarrior

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« Reply #12 on: February 01, 2013, 06:45:41 AM »

Thank you !!

My concern was that an outboard compressor adds NO lubricant, therefore dry air, and I was thinking about the lubrication of seals and valves if this is the source I use when I am parked, not that that is very often (and becoming less and less) with the increased number of calls I am receiving to transport disabled persons.
But when I do stop overnight, or while waiting for people at their appointment destination, I do need to be ready to go without delay, so I wondered about adding the compressor to be "always ready".
Can anyone recommend a minimum CFM for such a unit, so I do not "underpower" the system, and it runs too much?
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« Reply #13 on: February 01, 2013, 06:54:04 AM »

     I have a compressor tied into the ping tank, it needed a a motor change, was 240V X 3600RPM went to 120V  and it draws 17A at 90 PSI. I think the tank icut it off of stated 5CFM @ 90PSI, so it would marginal.
   I use it in campgrounds to keep engine run time down.
How about some pictures, Mister Ralph? Thanks in advance!
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« Reply #14 on: February 01, 2013, 08:46:26 AM »

I know that Sean has an on board air compressor to keep air pressure up to at least 90psi since their front door, air suspension leveling system, and toilet work off the air system. It can run off the inverter. Course Sean also has 8 8D AGM batteries (2040amp/hrs). Good Luck, TomC
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