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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: PCC on January 27, 2013, 01:50:37 PM



Title: Outboard Air Compressor
Post by: PCC 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


Title: Re: Outboard Air Compressor
Post by: Ralph7 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.


Title: Re: Outboard Air Compressor
Post by: bevans6 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


Title: Re: Outboard Air Compressor
Post by: robertglines1 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


Title: Re: Outboard Air Compressor
Post by: robertglines1 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.


Title: Re: Outboard Air Compressor
Post by: wayne 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.


Title: Re: Outboard Air Compressor
Post by: robertglines1 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


Title: Re: Outboard Air Compressor
Post by: bevans6 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 (http://www.homedepot.ca/product/6310-10-hp-63-gal-ultra-quiet-oil-free-steel-tank-air-compressor/998791)

Brian


Title: Re: Outboard Air Compressor
Post by: Oonrahnjay 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

     


Title: Re: Outboard Air Compressor
Post by: Ed Hackenbruch 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. ;D


Title: Re: Outboard Air Compressor
Post by: PCC 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?


Title: Re: Outboard Air Compressor
Post by: buswarrior 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



Title: Re: Outboard Air Compressor
Post by: PCC 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?


Title: Re: Outboard Air Compressor
Post by: Mex-Busnut 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!


Title: Re: Outboard Air Compressor
Post by: TomC 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


Title: Re: Outboard Air Compressor
Post by: zubzub on February 01, 2013, 09:22:31 AM
depending on how much air you are loosing a very small compressor (even a 12V) may be all you need.  The little 12V emergency" fill your tire" pumps will not drain your batteries, but most of them are noisy.....I have seen better quality somewhat quieter ones, and have used them in different applications.....FWIW if you remove the plastic housings around the compressor head they run cooler and last longer.  Small and inexpensive....must be worth something.


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 02, 2013, 07:07:33 AM
I have a Prevost Liberty that requires lots of air.  When Liberty did the conversion they added a 110/220 volt rotary vein compressor, in addition to the normal bus air compressor, that will wake the dead when in a campground.  To solve the noise issue I modified two refrigerator compressors that I use when I am parked.  They work in parallel and provide plenty of air for the toilet and air bags that the generator sits on.  These two compressors while small (and virtually silent) will lift the bus if you give them time.  They operate in parallel and are in-line with the main bus air system. I use a series of one way valves to isolate them so that they do not effect the main compressor.  If it sounds like something you are interested in I will draw up how I modified the compressors so that they are "dry" and how it is installed. Let me know


Title: Re: Outboard Air Compressor
Post by: garhawk on February 02, 2013, 07:29:01 AM
Thanks for the offer Chuck63 - let's see it!


Title: Re: Outboard Air Compressor
Post by: rv_safetyman on February 02, 2013, 08:59:44 AM
Auxiliary air compressors have been the subject of many thread on the various boards.

Two different requirements that I can see.  1) continuous air supply for toilets/doors/etc  2) part time for inflating tires or airing up to leave a campground.  A good 120V compressor is great for 1).  I suspect there are some OK 12 V units, but generally their volume is pretty low.

For 2), you could consider a York type AC compressor converted to a part time air compressor.  I have talked about that in many threads - perhaps the best of those threads is:

http://www.busconversions.com/bbs/index.php?topic=12589.0 (http://www.busconversions.com/bbs/index.php?topic=12589.0)

As I note in that thread, my goal has been to mount a belt driven hydraulic pump and York compressor on a belt drive from the crank of my generator.  I have quite a bit of experience with the York type compressor on my '56 Chevy for the air suspension - works great.

Because that type of compressor is partly cooled by the returning freon, I don't think you can run it for long periods (say 10 minutes or more).

Jim


Title: Re: Outboard Air Compressor
Post by: rv_safetyman on February 02, 2013, 09:07:36 AM
I thought I had chosen a reference thread that had two great links in it.  Turns out it only has one.

Here is the first link that talks about using a York compressor on a Jeep:

http://www.offroaders.com/info/tech-corner/project-cj7/project-cj7-onboard-air.htm (http://www.offroaders.com/info/tech-corner/project-cj7/project-cj7-onboard-air.htm)

Here is the second link to a company that sells kits/parts for York type compressors for air supplies:

http://www.onboardair.com/compressors.htm (http://www.onboardair.com/compressors.htm)

Jim


Title: Re: Outboard Air Compressor
Post by: wagwar on February 02, 2013, 09:32:48 AM
I purchased one of these:

Makita MAC700 Big Bore 2.0 HP Air Compressor

It fits nicely in the engine compartment of my MC9 where the old A/C compressor sat. It runs off the inverter if needed and airs up the bus in about 10 minutes. It is much quieter than the engine and will suffice for air tools in a pinch.

I never use it while running down the road and air brake test confirm the engine compressor is OK.


Title: Re: Outboard Air Compressor
Post by: Mex-Busnut on February 02, 2013, 09:38:25 AM
I have quite a bit of experience with the York type compressor on my '56 Chevy for the air suspension - works great.
Hmmm, Jim. What kind of air compressors are sold in hotrod shops to raise and lower their rods? 12 volts?


Title: Re: Outboard Air Compressor
Post by: rv_safetyman on February 02, 2013, 10:54:37 AM
Dr Steve, the main supplier to the aftermarket/"Hot Rod" market was known as "Air Ride Technologies".  They used to have a good site.  However, somehow, they became "Ride Tech" (http://www.ridetech.com/ (http://www.ridetech.com/)) and I their site is not all that user friendly.  

I poked around and found that they use Thomas 12V air compressors.  The largest I found is:

http://www.gd-thomas.com/product.aspx?id=12648&tp=p (http://www.gd-thomas.com/product.aspx?id=12648&tp=p)

A common Ride Tech compressor is also a Thomas 327 series, but much less capacity:

http://www.jegs.com/i/Ridetech/029/31920002/10002/-1 (http://www.jegs.com/i/Ridetech/029/31920002/10002/-1)

You can see that the first compressor has a delivery of 1.2 CFM and the Jegs version has a delivery of 0.5 CFM.  This is compared to the typical bus engine air compressor - Bendix Tu-Flo 550 which is rated at 13.2 CFM.

You can see that even the best 12V compressors have low CFM ratings compared to 120V units. engine compressors and the York 210 (a bit over 4 CFM).

Jim


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 02, 2013, 05:22:56 PM
garhawk, you asked for it so here is my best remembrance.

Quiet air  for Bus.  I took two refrigerator air compressors and modified them both as follows:  1. With a cut off tool I cut the “ball” around the weld line.  2.  Lifting the top I carefully  determined the input  from the output air line and cut the out put  air line close to where it exits the ball on the inside.  3.  The unit I was modifying had four small screws holding the compressor motor in place.  I took them out and lifted the motor out.  4.  I took a good degreaser and washed the motor very well as well as the inside of the compressor ball to remove all  shaving caused by cutting the ball in half.   While I had the motor out I cut, pinched shut and soldered the capillary vein that is used to  pickup oil and refrigerant when the compressor is used in a cooling application (I wanted clean, dry air with no oil being added to my system). 5.  I drilled a 3/8 hole in the top half of the “ball and ran the output line out thru the hole.  I put sufficient compressor oil in the compressor so that the “splash blade” on the bottom of the compressor motor is in it and splashes oil around to lube the motor.  6.  After reinstalling the motor I used a spare Prevost windshield gasket to join the top and bottom of the “ball” .  As the compressor is no longer used under pressure inside the ball (originally it was under very high pressure when used in a cooling application), the seal is not critical and only important to keep the oil in as it splashes on the motor to lube it.    I modified two  compressors like this and hooked them in parallel and then connected them to the aux air tank that Liberty had installed during  the  conversion.   

Coming from the two compressors , I first put the air through a water / oil separator to catch any residual oil or moisture, then run the air through a one way valve and  from there thru a “head pressure” relief valve (the output of the head pressure  relief valve feeds back to the line from the compressors just after the water / oil separator.  This allows the compressors to start each time against 0 head pressure).  After that it goes thru an electrical pressure switch that provides power to the compressor anytime the  pressure is less than 90 lbs and shuts off at 130lbs.  From there it is on to  the new 7gallon tank I  installed that operates just the toilet. 
I know this sounds like a lot to doing to have a quiet source of air but it became a challenge (you guys know how that goes). I am sure I could have bought a silent air system cheaper but this really  works great and is low maintenance  (every now and then I  have to check the oil level in the compressors and I change it once a season.). 
 


Title: Re: Outboard Air Compressor
Post by: Scott & Heather on February 03, 2013, 11:01:40 AM
I know a couple of you guys mentioned that you have to set the regulator on the aux air compressor low enough that it still fills your air bags/air system and yet doesn't trip the air dryer right? (did I say that right?). I have this problem everytime I go to fill the coach air with my pancake compressor...it trips the dryer and then all the air leaks out...no more filling. So what exactly is the PSI number? 90?


Title: Re: Outboard Air Compressor
Post by: lostagain on February 03, 2013, 11:19:56 AM
Anything below 120psi, which is where the air dryer purges, (give or take 10psi), will do I think.

Mine is set at 100psi. That will operate anything you need while parked, and you can release your parking brake and move out as soon as you start your engine. Plus 100psi is plenty to air up tires.

JC


Title: Re: Outboard Air Compressor
Post by: Scott & Heather on February 03, 2013, 01:29:21 PM
Isn't there another threshold below that? I understand the purge cycle happens at 120 PSI, but for some reason I thought there was a lower threshold for air releasing...I guess I'm confused.


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 03, 2013, 03:16:21 PM
My air brakes purges at 110lbs and the outboard aux air tank max's at 110lbs. 


Title: Re: Outboard Air Compressor
Post by: bevans6 on February 03, 2013, 03:30:53 PM
Just use your dash gauge to set the pressure - look at where the air dryer is told to purge by the governor, and set it anywhere below that.

Brian


Title: Re: Outboard Air Compressor
Post by: Scott & Heather on February 03, 2013, 03:48:43 PM
K. Got it. Thanks team.


Title: Re: Outboard Air Compressor
Post by: Emcemv on February 04, 2013, 03:23:35 PM
Chuck

Nice write up on the compressor. I just tried my small pancake compressor this last weekend and it was noisy. Your system could easily be built in.  Another project for me!!


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 06, 2013, 06:03:49 AM

Bruce,  if you decide to try it let me know.  I have one that I "experimented" with that you can look at to see what you are getting into.  The write up makes it sound like more of a job than it really is (Peter helped me add condensors to kick start them when running on the inverter). 


Title: Re: Outboard Air Compressor
Post by: rv_safetyman on February 06, 2013, 08:31:34 AM
A few years ago, there was a thread that talked about making sure you bought an compressor with an oil sump rather than oil less.  Supposed to be quieter.  I bought a sears unit that someone recommended and it was terrible.  I think it was this one:

http://www.sears.com/craftsman-3-gallon-horizontal-air-compressor-with-hose/p-00915310000P (http://www.sears.com/craftsman-3-gallon-horizontal-air-compressor-with-hose/p-00915310000P)

Assuming that is the same one I bought (fairly sure) it is rated at 2.4 CFM at 90 PSI.  My guess is that it delivered far less.  Also after little usage I had to rebuild the top end.  It was not all that quiet.  Gave it away on Craigslist.

I contacted Sean to see what he used and his was an  Hitachi -EC119SA.  Here is one source:

http://www.amazon.com/Hitachi-EC119SA-2-5-Horsepower-Twin-Stack-Compressor/dp/B000G6C7XQ (http://www.amazon.com/Hitachi-EC119SA-2-5-Horsepower-Twin-Stack-Compressor/dp/B000G6C7XQ)

That compressor is rated at 4 CFM at 100 PSI.  

I bought a reconditioned unit and am moderately pleased with it.  As was the case with the Sears,  I am not convinced that I am getting 4 CFM.  If you try to run a good 1/2 inch impact off of it, you will get very frustrated quickly.  Then again, I am spoiled by a "REAL" compressor (5 HP Quincey).  The foot print of the Hatachi is quite a bit bigger than the Sears and I had to do some arranging to get it situated in the bay.  The only issue I have with it, is that the motor overload will kick out when the compressor is cold (maybe 30*).

It is louder than I would like, but with the bay door shut, it is acceptable.

In this, and similar threads, folks talk about enclosing the air compressor in a sound box.  If you do, be sure to have some sort of air circulation system.  Those suckers will get pretty warm in an enclosed box.

Jim



Title: Re: Outboard Air Compressor
Post by: Emcemv on February 06, 2013, 09:55:56 AM
This has been a great discussion, really shows the value of this forum!  I connected up my small compressor to the bus last weekend and tried to air it up from zero. It took forever and ran the little compressor to death.  Then I got thinking about unfiltered wet air going in to the bus system and stopped. Our bus holds air about a day and I was looking for something to use while camping just to keep the air up so I think this may work in that situation.  Once the weather improves, I will be under the bus to see if I can find any leaks and that may also improve my situation. I'm going to get a filter and dryer for it and feed into the bus air through a check valve as well. My small compressor is a 6 gallon, 2.5gpm 150 psi unit.

Chuck - does your system feed the whole bus air system or just the 7 gallon tank for the toilet?


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 06, 2013, 05:37:03 PM
Bruce,  I have it setup so that all of the compressors (bus compressor, Aux air installed by Liberty and the two refrigerator compressors I installed ) feed the small tank I installed to operate the toilet.  However when the bus is parked and I don't want to run the motor or the Aux air (very noisy) then I use only  the refrigerator compressors and they feed just the small  toilet air tank.  They are blocked from sending air back to the aux tank or main tanks by the use of a check valve.  By changing a check valve I can allow air to  go  to from the refrigerator compressors to the Aux tank and the main bus tanks but have not had a need to do that. 

When the bus has had the air dumped from the leveling bags or the brake air  is  low from sitting for an extended period of time and I want to get underway I  use the Aux air or run the motor as they are much bigger compressors and build the air up much faster.


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 06, 2013, 05:45:52 PM
Bruce, I see comments  on here about  using compressors that add moisture or oil to the air.  I specifically modified the two refrigerator compressors  to make sure that they did not add moisture or oil and also installed a "dryer / water / oil" separator in the line to insure dry, clean air.   There is no advantage I know of to adding moisture or oil to any air system (other than air conditioning) .  Moisture is naturally added because  of the heat from the compressors and oil can get in if you use a compressor with an oil sump (like the modified refrigeration compressors I used) so you need to design the system to take clean the air up and take out any moisture or  oil.


Title: Re: Outboard Air Compressor
Post by: Lin on February 06, 2013, 05:59:37 PM
We have a small, old Inglo dual tank compressor.  I think it is the type someone would bring to a construction job to run nail guns, etc.  I almost always use it to air up the bus so we are ready to go at the turn of the key.  When camping, I use it to top off the air once a day so the air bags won't deflate and change our level.  I have not timed it to see how long it takes to go from 0-120. I'm sure it's between 5-10 minutes.  Since there is always something else to do, I never notice.  If I was in a rush to get started, I would just use the engine compressor at 1000+rpm.  I really do not think that we use it enough to put any significant amounts of pollutants into the system, and whatever there is gets purged either automatically or when I pulled the valve cable after a run.

It is a great convenience and a nice back up for tires and tools.  Now, my compressor is rather noisey, but not near as much as the airless one we used to have.  Ed H. once showed me his compressor.  It's bigger than mine but much more quiet.


Title: Re: Outboard Air Compressor
Post by: Scott & Heather on February 06, 2013, 06:08:36 PM
So all this talk about keeping your bags inflated...bunch of windbags we are...anyway, we hate sitting on our bags. When we are parked for just a night or two, I don't stick our jacks under there..and she bounces. Someone gets up in the middle of the night to go to the restroom...coach bounces. Someone gets up early to have some breakfast...coach bounces. Ugh. When she's on jacks...she's solid as a real house. Love it! I never rest the coach on its bags...only on jacks all the way around. Level it, and it just is so solid. Even strong strong gusts of wind don't rock it at all... 8)


Title: Re: Outboard Air Compressor
Post by: Chuck Hancock on February 06, 2013, 06:18:42 PM
Lin, you are right.  I am sure the way you described using the compressor will not cause any problems.  My coach requires air to flush the toilet and keep it level and when I am parked for extended periods (I park for as much as three months when I go to calif for the winter) and I designed my system to minimize any contaminants.  

Scott, I would love to have jacks but just have 8 air bags. 


Title: Re: Outboard Air Compressor
Post by: zubzub on February 06, 2013, 11:55:06 PM
A few years ago, there was a thread that talked about making sure you bought an compressor with an oil sump rather than oil less.  Supposed to be quieter.  I bought a sears unit that someone recommended and it was terrible.  I think it was this one:

http://www.sears.com/craftsman-3-gallon-horizontal-air-compressor-with-hose/p-00915310000P ([url]http://http://www.sears.com/craftsman-3-gallon-horizontal-air-compressor-with-hose/p-00915310000P[/url])

Assuming that is the same one I bought (fairly sure) it is rated at 2.4 CFM at 90 PSI.  My guess is that it delivered far less.  Also after little usage I had to rebuild the top end.  It was not all that quiet.  



Jim




I think you got a lemon...or I got the opposite of a lemon.  Bought the same compressor on recommendation of the board ( 6 years ago) and still have it...use it for work sometimes and always for the bus because it kicks in easier than my big Comp and doesn't drag my generator down.  It is pretty quiet (there are quieter ones) but I like the light weight, small footprint and durability.


Title: Re: Outboard Air Compressor
Post by: rv_safetyman on February 08, 2013, 09:33:34 AM
Now that you mention it, I recall that the Sears unit was well recommended.  It sure had a nice footprint and was OK on noise. 

Yes, I probably got a lemon - story of my life ::)

Jim