electric air compressor tied into air system on bus

[moose]

Hello
i have a 1970 mci 7
i want to install an electric aircompressor in compartment beside engine
does anyone have suggestions how to do this or even a diagram and a list of parts needed
Thank you
trevor

[FloridaCliff]

Just put in in line before the air dryer(if you have one) and on mine it attaches with a female air connection

I have a quarter turn shut off valve between the connection point and the coach air system.

I like to use the connection to attach a 50' hose if I need to air up my tires.

Cliff

[JackConrad]

Trevor,
   We installed our portable air compessor where the OEM AC compressor was. I removed the air line from the the top of the ping tank, installed a tee and re-connect the air line. I then installed a check valve in the over Tee opening and a line to the portable air compressor along with a quick connet fitting to fill the system from shop air as well as for a connection point for an air line supplied from the bus air. This line is connected to the portable air compressor with quick connect fittings. The check valve and quick connect fittings allow the portable compressor to be removed without affecting the bus operation. Air from the portable compressor, as well as air from my shop air system goes through the air dryer on the bus before entering the rest of the bus air system.

[Iceni John]

I did this a few months ago.   I got a Harbor Fright 95498 compressor for only $72 (they're on sale again for $90, and you can also use the 20%-off coupon!), connected it to my accessories tank, and put air couplers on both sides of the luggage bay and in the engine room.   Now I can run air tools and inflate tires without running the engine.   I can also connect the compressor to the wet tank (Crown thoughtfully put an air coupler and ball valve on it) and air up the entire bus in less than five minutes.   I'm using standard industrial-type fittings, but Crown also put an automotive coupler on the end of the wet tank's drain, so I can also easily connect to shop air with either type of coupler.   For the few times I run the electric compressor I can manually drain its tank, so I didn't connect it through the bus's AD-9 dryer.   To finish the job, I got a pressure gauge from Grainger (for only $1.59!!), to let me know how much pressure is in the accessories tank.

This setup works well for me, didn't cost much, and has allowed me to easily grease every nipple underneath with my air grease gun.   Now that's a good feeling!   The 95498 compressor is not bad  -  4 gallon twin-tank, direct-drive, oil-type, usefully compact, and for the occasional use it will get it's just fine.

John

[bevans6]

My Ping tank looks different from the one pictured, it has a drain on the bottom (with "drain daily" sticker), and had a Schrader valve so you could air up the bus through it.  I took the Schrader valve off and installed a female quick connect with a ball valve.  The ball valve is kind of extra insurance since I've known the quick connects to fail open or start leaking.  I use a male - male connector to attach the compressor line.  My compressor lives in my wet bay, isn't permanently connected, since it is way too loud and I am still looking for a small, inexpensive and quiet compressor that has enough airflow to air up the bus from zero in 10 minutes or less.  I also have a similar ball valve and female quick connect on the drain for the accessory tank.  If I need to put air in, i put it in at the ping tank.  If I need to take air out, I take it out of the accessory tank.  

One tip - set your compressor maximum pressure to less  that your governor cut-out pressure.  If you exceed the cut out pressure, the governor will cut out, the air dryer will purge and since your compressor isn't in that loop it just sits there and puts air through the system and gets purged to atmosphere until you notice and turn it off.  I know this how, you ask...??  

Brian

[robertglines1]

I have a lot of air cyl and controls to maintain.so use back up electric compressor..have changed them out several times due to failure..seem to run about 4 to 5 minutes every 24 hrs to maintain 65 plus lbs air pressure where the secondary air system is regulated to release to the brake system..I set kick on at 90 and it kicks off at 110..keeps bus air bags up and door controllers working as they should. plugged in 24 hrs a day 7 days a week 365 days a year like Jack and others pointed out a good ck valve or shut off system will stop any possibility of your bus air being lost thru a failed elect compressor..good luck...Bob

[rwc]

Aren't most of these air compressors too loud to use in a camp ground. I know my 28 gallon compressor in the carport will wake the dead. I don't think I could use that to keep a bus aired up. It has the capacity but just too loud.

[happycamperbrat]

Just a word of caution here... The PO had installed a hose clamped connection on one of the air lines in the engine compartment on my bus, only he failed to tell me about it when I bought it and it was kinda hidden in a spot I did not notice. After about 2500 miles I was at the top of a 7% grade that had steep drop offs and just moments before the last turn out before going down the grade my air pressure suddenly dropped to dangerously low! I pulled over and could here the air hissing. I followed the sound with a stethescope to find it and plug it so I could continue my trip. Please be careful and check your fittings from time to time, losing air on a grade like that is NOT something anyone would want to experience.

[TomC]

Technically- because of the reed valves in compressors, you can just simply T into the outlet side of the bus compressor before the air dryer and be done with it.  Good Luck, TomC

[Merlin-PV]

    Good Idea to have a spare compressor onboard. Last year on our trip south for the winter a connecting rod on the engine mounted compressor broke  completely destroying said compressor, no replacement could be found anywhere for less than 6 weeks out.  I had installed a cheapo Harbor Freight compressor in an up front compartment to keep aired up over night , well believe it or not that cheap $99 compressor got us 1200 mi to our southern destination without fail, and it did take 6 weeks to find a replacement for the main pump F.W.I.W.

[BG6]

Aren't most of these air compressors too loud to use in a camp ground. I know my 28 gallon compressor in the carport will wake the dead. I don't think I could use that to keep a bus aired up. It has the capacity but just too loud.

You can blimp the sound with insulation -- just don't restrict cooling airflow.

However, I agree, the HF units ARE loud.  In my case, I hunted craigslist until I found a higher-quality compressor at a cheap price.  It's significantly quieter, far less noise than the coach engine, so I can air up while I'm doing my walkaround, disconnecting umbilicals, etc, then hop in, light off, and as soon as the turbo has warmed up I can hit the road.

[BG6]

Last year on our trip south for the winter a connecting rod on the engine mounted compressor broke  completely destroying said compressor, no replacement could be found anywhere for less than 6 weeks out.  I had installed a cheapo Harbor Freight compressor in an up front compartment to keep aired up over night , well believe it or not that cheap $99 compressor got us 1200 mi to our southern destination

I consider this right up near the top of the Really, REALLY, REALLY(!!!) Stupid Ideas List.  This is something to try only if there is absolutely no other option. 

You HAD other options. 

If necessary, you could have parked the coach and come back when the part arrived -- though I can't imagine any part in a coach which would take SIX WEEKS to get.  One call to Ted or Luke will get you pretty much anything by Next Day Air or three days by truck freight, and compressors are available new and used in any truck dealer or wrecking yard in the country.

Your air system is the only thing letting you stop FIFTEEN TONS of DEADLY WEAPON.  You ran halfway across the country with a kludged air system, simply for your convenience.

Yes, I am seriously pissed at you.  A friend of mine is in the list of victims in this story from last week:  -- http://www.baguiochronicle.com/2010/08/42-killed-9-injured-in-benguet-bus.html -- and read why FORTY-TWO PEOPLE ARE DEAD: "While traversing Naguilian Road, the bus driven by a certain Romeo Subang Jr. apparently lost its brakes and plummeted into a ravine 35 to 50 meters deep."

Before you attribute it to "third world" maintenance or safety standards, tell me how what you did is any better?

You risked the lives of every other person on 1200 miles of highway, just to fly south for the winter.

You risked the reputation of every busnut in the country, too.  Nobody seeing "Converted bus goes wild" on the TV news will think about your kludged-up air system -- they will just think about the van full of schoolkids that you killed, and condemn the rest of us. 

We have enough trouble being accepted by non-busnuts, without going out of our way to juggle live grenades.

You may be a great guy, you may turn into a buddy, but right now, all I see is you bragging about something you should have never done.  Using a compressor to air up enough to get to the next town, okay, that is legitimate, acceptable risk.  Going the rest of the way across the country, no, that's not.

[bevans6]

this is right up there in the "confessing to a serious crime on a public internet forum" category, because that's what you just did.  It is totally and completely illegal to operate a vehicle with air brakes on any public road for any reason if the engine driven air compressor is not working properly.

I can't believe you did that, and I can't believe you told us you did that.  And I will disagree with BG6, totally and completely, as far the law is concerned, and common sense, and any sense of obligation to your fellow citizens - there is only one way that a bus with no operating air compressor should be moved on a public road for any reason, and that is behind a  tow truck.  Period.  There is no "legitimate, acceptable risk" about it, it is just wrong.

brian

[Barn Owl]

I have seen these used in RVs. They are quiet but expensive. Look for one on Craigslist, Ebay, or an RV salvage site. I let one get away from me last year but at this time but I don't need one because my bus will hold air longer than my vacation. If I where to park and FT then I would be much more interested.

Gast Compressor

[Merlin-PV]

before you guys get your nose out of joint air pressure never got below 100 lbs 6 tank system air bags turned off air was for 100% braking witch if you pay attention to what you are doing you are ok, Luke was one of the many that said 6 weeks. can't spend 6 weeks in a rest area.