Caveat - I have been out of bussing for a while, so this may be dumb.
How would it work out to use a small DC compressor to keep the bus aired up at all times?
I was thinking one could use a compressor (like the air suspension compressor from a Range Rover) to keep a bus aired up - and ellimate the noise of idle, or a shop side compressor prior to departing a camping location.
Is this silly, do the air systems leak too much for this?
No, it is not silly, many people have backup compressors, but most do it to be able to slip out of a campground spot without smoking the neighbors (too much), or to be able to listen for air leaks without the engine running. Usually these are portable AC electric compressors, not small DC compressors. There is no real need to keep the bus aired up all the time, plus if you could keep up with a small DC compressor, it would run the batteries down unless they were being charged (by an AC charger, usually). ;)
I was thinking if you were on shore power you would have a continuous DC source from the charger/converter (so the batteries should stay up), and if you were not on shore power there may not be anyone else to bother with the noise anyway. Some of the Aux compressors can be rather loud too (diaphragm).
I guess the question would be - what is the normal leakage rate at regulated pressure (cfm)?
Our 4108a will air up in less time than it takes the engine to get wsrmed up enough to get going in the morning. Our 4106 did as well.
Would it be worth looking into the system to see if you can improve the air up time?
When parked, both buses would stay up for weeks, even if the gauge bled down. There's nothing magical about keeping the air in other than perseverance and persistence.
hcvdg,
My plan is to install a small A/C compressor possibly in the front area under the driver. There is another post on this that I woke back up as well. Here is the link:
https://www.busconversionmagazine.com/forum/index.php?topic=267.msg380115#msg380115
Not sure what the space allocation is like on your bus, but mine has space. My bus used to leak down really quick. My luggage bay locks were leaking a ton. Of course this can be stopped via the valve by the driver. Since I have disconnect the bay door locks (I'm converting to electric) my bus stays aired up longer. Still leaks but not as fast. I still have a few leaks with the wipers and with some relief valves in the back. I plan to disconnect and apply some seal tape to see if I can fix those leaks. Its a game of searching for the hiss, then gaining access to it.
I believe the post I mention above mentions the best way to use the compressor to air the bus completely before even starting the bus
All in all, the time it takes your bus to air up and to lose air all depends on how many leaks there are.
I plan to tackle my other leaks then eventually get a compressor as well
Jonathan
I wonder if a small air suspension compressor like on a Range Rover would have enough capacity to do the job. They don't produce much cfm. Might be overcome by leaks. Their rated duty cycle is much shorter than you need.
Oil lubed compressor, small shop type, will give longest, satisfying, service.
I'm a fan of fooling around with free stuff on hand, but if yer going to spend money, spend a bunch once, and be done with it.
You'll burn out lesser units.
It's about CFM and duty cycle.
Happy coaching!
Buswarrior
I have a small 12v refrigerator compressor that I intend to make into an air compressor. Quiet! Just have to find some building tips
My Humvee has a 24 v Oasis compressor it is quite and pumps a bunch of air, no telling what the military pays for one though, it looks expensive
I found this link for modifying a DC fridge compressor. (Geoff)
Might be able to couple he compressor to a small high pressure tank to have some air on tap, as well as keeping the bus air tank topped off (quietly).
https://www.instructables.com/id/How-to-modify-a-fridge-compressor-into-a-silent-ai/
Hard to justify taking the time to build it when you can get this one this cheap. Sure, it isn't as quiet and ratings aren't fantastic, although many are happy with it. There are larger ones also. And extended warranties available.
https://www.harborfreight.com/3-gal-13-HP-100-PSI-Oilless-Hotdog-Air-Compressor-69269.html?ccdenc=eyJjb2RlIjoiNDE4NjQ2MDQiLCJza3UiOiI2OTI2OSIsImlzIjoiNDQuOTkiLCJwcm9kdWN0X2lk%0D%0AIjoiODY2NSJ9%0D%0A
Thanks for the link. I have most of the parts already. BTW, the HF compressor would be very noisy. Oil-less compressor motors are the loudest, I know, I have one.
Huh??? What did you say. They always seem quiet to me.☺
https://express.google.com/u/0/product/8854732696752152839_3329444740726281221_1699011?utm_source=google_shopping&utm_medium=tu_cu&utm_content=eid-lsjeuxoeqt,eid-ptgtgfeotu,eid-ygcnqnyulq,4181969>im=COnYr9262sbX8gEQvpmu3LDylvEjGPCIzFoiA1VTRCiQmdPbBQ&utm_campaign=1699011
used this one in two coaches, quiet, draws about 20 amps when running. You will need a pressure switch.
Quote from: chessie4905 on August 09, 2018, 09:40:35 AM
Huh??? What did you say. They always seem quiet to me.☺
Change your hearing aid batteries :P
The Range Rover compressor is a good unit and can put out a bit over 150psi if it needs to but it doesn't put out anywhere near enough volume for a bus. For a pair of 4" or 4-1/2" airbags, yeah it'll do great if you keep the pressure under 100psi and OK but really kinda slow at 150.
The kinda volume you're talking about though you'd have to have a 100% duty cycle and it's just not built for that.
Keep in mind, you could have a fitting or seal go and dump all your air. Then you're pumping up from zero and it'll take awhile. Best to get the biggest compressor you can, that you can fit into the available space and then run it on AC. Compressors take a lot of juice, that's why the BTUs of A/C units are limited. If you need to run the generator to air up you might as well start the bus engine to do it.
Your choice whether to go with a small compressor rated for constant duty or a bigger one with a lower duty cycle. The newer 3400rpm ones are pretty compact for the air volume, generally louder but don't have to run as long. A converted A/C compressor is quiet but may need an oil trap/separator to return oil to the canister. Very compact though and possibly free. Usually a little oil in the air is not a bad thing, but you might need to add a dipstick. The bigger the better though.
The key to a quiet compressor though is in the intake. That's where all the noise is created. If you can baffle and deaden that without restricting inflow then you can pretty well silence any compressor.
Jim
Good input. I liked the Viair compressor as a ?turn key? solution. I also liked the suggestion of using a 12V fridge compressor (quiet).
The coach I?m considering has a 135 psi Porter-Cable compressor already installed (I don?t know the operating pressure of the tank).
One thought is to use a Viair compressor, or a 12V fridge compressor, to feed the bus air tank. Another thought would be to take advantage of the high pressure capability of a fridge compressor to store air at higher pressure in another tank.
If either the Viair or the fridge compressor were not up to the task of keeping the bus aired up, I would look to reduce the leaks.
Attached is a photo of a Range Rover air tank specs showing 250 psi, and 3 gal. in case anyone is looking for a tank (eBay, or a junk yard).
Thomas makes the little 12v DC compressor that CC used on their coaches .We were talking about this issue on here a while back and someone had one of these for sale for a hundred bucks.Good deal when you consider a new one is three hundred plus .Maybe he will come forward if he still has it. They are called "wobble shaft"compressor.Rated at 100 pounds but best I have ever got out of mine is 85psi
We run an ancient Craftsman that won't quit. 1 hp 110vac 6.9 cfm @ 90 psi. Alum. oiled piston compressor. It safely took us from Atlanta GA to Indianapolis IN as auxilliary air when our engine compressor drive failed. Airs up the bus in 5 min. & sits next to the tool box for the air tools. Used it for a lifetime for gun nailing when we retired we took the wheels off & stuck it in the bottom compartment, tank & all. We love it.
Can't argue with an ancient Craftsman--good goods. As far as present day pumps go I'd pay the extra for a Tomas continuous duty pump. They are bullet proof. I've run through a couple of the Viair continuous duty pumps which got so hot they melted their plastic lines before they quit. Jack
If you want a compressor that will last, you can't do much better than the old cast iron Champion 2 stage but you will need at least 5hp to run it. Used to be able to buy those from gov't surplus. It'll give you 150psi all day every day for decades to come and run any hand tool you have. Still made and sold too last time I looked.
Jim
I have a 150psi Viair 12v compressor rated 100% duty cycle, 100psi pressure cut off switch. It takes about 45min to air up our 4104 from 0psi, is has no problem keeping up with our small leaks. We are fulltimers and have aired up the bus several times a week for almost 5 years with no problem.
Compressor is similar to this one;
https://www.ebay.com/itm/Viair-400C-Silver-Heavyweight-Air-Compressor-for-Trains-Horns-Air-Suspension/222076365904?epid=1629432093&hash=item33b4c86c50%3Ag%3AOp4AAOSwLqFV8z-a&_sacat=0&_nkw=viair+12v+air+suspension+compressor&_from=R40&rt=nc&LH_TitleDesc=0%7C0
Bob
I found Viair junk, I had a 24v heavy duty that ran an additional 5 gal air tank to keep my air lock door operating, unit failed just after warranty ran out took apart and piston ring whore out not compressing air. Viair wanted me to ship and pay $45 to check plus parts and shipping back. It is sitting on shelf went with a Craftsman oil ac compressor. Oil less gets to hot causing piston ring failures.