Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: Kent Speers on December 28, 2010, 11:25:03 am
Title: Low Air Pressure from Air Hose
Post by: Kent Speers on December 28, 2010, 11:25:03 am
Can anyone tell me how to increase the air pressure through the air hose. My inside air gauges show 110 psi but the air hose only puts out 85 psi. 1993 U300. It prevents me from filling tires to my preferred level.
Is there a way to adjust the compressor to cut off at 120 rather than 110? I have the Detroit 6V92 DDEC.
Is there a Schroeder valve in the air system so I can check my air gauge accuracy?
Title: Re: Low Air Pressure from Air Hose
Post by: Russell on December 28, 2010, 11:39:52 am
Kent:
Perhaps this might help??? Not sure about what you might have on your restored Foretravel, but this is how I do it on mine.
Title: Re: Low Air Pressure from Air Hose
Post by: Bill Chaplin on December 28, 2010, 12:55:33 pm
Check you gauges for accuracy first
Title: Re: Low Air Pressure from Air Hose
Post by: Jerry Whiteaker on December 28, 2010, 02:19:31 pm
Kent,
Does your coach have 3 air tanks? On mine which is a later model there are 3 tanks. The first tank receives air from the dryer and sends it to the other 2 tanks which supply the brakes and that is where the pressure is read. There are check valves between the first tank and the other tanks. I think the air hose is tapped into the first tank so even though the first tank is drained of air or equal to the tire pressure, the gages will still show pressure. You have to have the engine running to keep the pressure up in the first tank when adding air to the tires. If governor cut in is set too low you would have to waste some air to get the compressor to cut in and rebuild the pressure enough to fill the tire. It takes some difference like 10 or 15 lbs between the tire and tank in order to force open the schrader valve in the tire stem.
Title: Re: Low Air Pressure from Air Hose
Post by: J. D. Stevens on December 28, 2010, 04:04:57 pm
I have been able to inflate tires to 100 psi if I fill immediately after "cut-out" as indicated by the dryer venting. I might even be able to get 110 if I am very patient. However, if the compressor is dropping toward "cut-in" value, you probably don't want to have the chuck on the tire.
As others recommended, check your gauges. I have several gauges and I check them against each other to keep them honest.
Title: Re: Low Air Pressure from Air Hose
Post by: Neal Pillsbury on December 28, 2010, 10:09:27 pm
Can anyone tell me how to increase the air pressure through the air hose. My inside air gauges show 110 psi but the air hose only puts out 85 psi. 1993 U300. It prevents me from filling tires to my preferred level.
Is there a way to adjust the compressor to cut off at 120 rather than 110? I have the Detroit 6V92 DDEC.
Is there a Schroeder valve in the air system so I can check my air gauge accuracy?
Kent, The suggestions to verify instrument accuracy are good. Do you have the typical D2 Governor set up? I had a different problem that was easily resolved. It may be of some use to you or others. My U270 (as built, '98) had no air chuck. In looking at the air system design, I felt that adding an air chuck directly to the Bendix D2 governor valve body made the most sense. Reference resource: https://www.foreforums.com/MGalleryItem.php?id=3412 As you can see, the (3) Bendix D2 Governor "reservoir ports" are common within the Governor valve body. On my coach, two ports had 1/8"PT plugs and the third references (is connected to) the first (WET) air system tank. Thus, by removing one of the "reservoir port" plugs and adding a quick disconnect air hose fitting there, I would be tapping into the first air tank (highest) pressure, and if I caused any appreciable air flow pressure drops in airing up my tires, I would be doing it right at the very best place to cause the governor valve to shift, causing the compressor to start sending makeup air to the wet tank. Thus "droop" in the system would be minimal before the governor shifted. And, if the governor didn't shift, all I had to do was manually vent the air chuck for a couple of seconds and the governor would shift as it sensed the lowered pressure. That helps a great deal in that I don't have to keep hopping in and out of the coach to use the braking system to lower air system pressure (or rely upon a helper) to shift the Governor, to get back to the higher pressures in the air system. I keep a rubber plug in the Governor-installed, quick disconnect air fitting , to keep dust and particles out, when not using an air hose. Also, installing a Schroeder valve in the other plugged Bendix D2 "reservoir port", would give you a way to check your WET tank air pressure. Or, as I have done, using the KISS principle (to keep maintenance down and reliability up), just install a Schroeder valve in your air hose. In a static system, air pressure at the far end of your air hose is exactly equal to your WET tank internal pressure.
It has worked great for me for 10(+) years.
Hope this helps you/others. Neal
Title: Re: Low Air Pressure from Air Hose
Post by: ncaabbfan on December 28, 2010, 11:18:13 pm
Kent, The suggestions to verify instrument accuracy are good. Do you have the typical D2 Governor set up? I had a different problem that was easily resolved. It may be of some use to you or others. My U270 (as built, '98) had no air chuck. In looking at the air system design, I felt that adding an air chuck directly to the Bendix D2 governor valve body made the most sense. Reference Barry's resource: Haldex D2 Governor Service Data (http://www.beamalarm.com/Documents/haldex_d2_governor_service_data.htm) As you can see, the (3) Bendix D2 Governor "reservoir ports" are common within the Governor valve body. On my coach, two ports had 1/8"PT plugs and the third references (is connected to) the first (WET) air system tank. Thus, by removing one of the "reservoir port" plugs and adding a quick disconnect air hose fitting there, I would be tapping into the first air tank (highest) pressure, and if I caused any appreciable air flow pressure drops in airing up my tires, I would be doing it right at the very best place to cause the governor valve to shift, causing the compressor to start sending makeup air to the wet tank. Thus "droop" in the system would be minimal before the governor shifted. And, if the governor didn't shift, all I had to do was manually vent the air chuck for a couple of seconds and the governor would shift as it sensed the lowered pressure. That helps a great deal in that I don't have to keep hopping in and out of the coach to use the braking system to lower air system pressure (or rely upon a helper) to shift the Governor, to get back to the higher pressures in the air system. I keep a rubber plug in the Governor-installed, quick disconnect air fitting , to keep dust and particles out, when not using an air hose. Also, installing a Schroeder valve in the other plugged Bendix D2 "reservoir port", would give you a way to check your WET tank air pressure. Or, as I have done, using the KISS principle (to keep maintenance down and reliability up), just install a Schroeder valve in your air hose. In a static system, air pressure at the far end of your air hose is exactly equal to your WET tank internal pressure.
It has worked great for me for 10(+) years.
Hope this helps you/others. Neal
Neal, Can you post some pictures of what you did to connect the air hose and which port you used? Also, what size air hose do you use?
Thank you.
Title: Re: Low Air Pressure from Air Hose
Post by: Neal Pillsbury on December 29, 2010, 12:17:51 am
Neal, Can you post some pictures of what you did to connect the air hose and which port you used? Also, what size air hose do you use? Thank you.
Morris, I'll take a couple pictures tomorrow and post them. The air hose is just inexpensive, industrial grade, air hose — 3/8in. x 40ft., 250 PSI, I think. Any Lowes, Home Depot, Northern Hydraulic, etc. would have it, and usually you can find it for $20 or less. I'll see if there are any markings on it. Neal
Title: Re: Low Air Pressure from Air Hose
Post by: Kent Speers on December 29, 2010, 09:31:47 am
Boy, ask and you shall receive. What great answers.
Russel, thanks for the info. Will the air governor on my Detroit look similar? I have seen a similar part on my old Cummins but don't see it on my Detroit.
Bill, I will check the pressure first but I think Jerry's point about 10 to 15 psi to open Schroeder valve explains why I can't get over 95 psi when the gauge shows 110.
Neal, the idea of pulling the air from the compressor sounds very interesting. I would want a very good quality quick disconnect. Where would you suggest purchasing a top quality part? Wouldn't it be a good idea to install a positive shut off valve between the compressor and the QD to insure it won't leak?
I am not sure if I have a typical Bendix D2 on my Detroit. I unnecessarily replaced one on my 225 so I know what to look for. I will check more closely later today when it warms up outside.
Does anyone know where the air governor is located on a Detroit V692?
Title: Re: Low Air Pressure from Air Hose
Post by: ncaabbfan on December 29, 2010, 10:22:42 am
Morris, I'll take a couple pictures tomorrow and post them. The air hose is just inexpensive, industrial grade, air hose — 3/8in. x 40ft., 250 PSI, I think. Any Lowes, Home Depot, Northern Hydraulic, etc. would have it, and usually you can find it for $20 or less. I'll see if there are any markings on it. Neal
Thank you very much. That will help a lot.
Title: Re: Low Air Pressure from Air Hose
Post by: PatC on December 29, 2010, 03:23:18 pm
You could always add one of these: SMC Pneumatics - Regulator [Booster Regulator] (http://www.smcpneumatics.com/products/regulator/booster-regulator.php) onto the system. Lots smaller and lighter than a extra compressor. But pricer too.
But you should be able to get 120 lbs out of your air system with a time and waiting for the engine compressor to be right up there.
Title: Re: Low Air Pressure from Air Hose
Post by: Neal Pillsbury on December 29, 2010, 03:58:42 pm
.......................Neal, Can you post some pictures of what you did to connect the air hose and which port you used? Also, what size air hose do you use? Thank you.................................
Morris, Here is the link to the Haldex website for my installed Governor. http://tinyurl.com/27y3dh4 Attached are a few pictures of my Haldex KN 18530 "D2" Governor and how I have my quick disconnect air fitting attached to the Governor. Also of my air hose that has been very cost effective (it was a gift).
.......................Neal, the idea of pulling the air from the compressor sounds very interesting. I would want a very good quality quick disconnect. Where would you suggest purchasing a top quality part? Wouldn't it be a good idea to install a positive shut off valve between the compressor and the QD to insure it won't leak?.............................
Kent, Quick disconnect air fittings are pretty reliable and meant to take a lot of EVERYDAY abuse. A quick disconnect fitting seal is designed to avoid damage as you connect and disconnect from it and when disconnected, system air pressure only improves the seating force. I just keep mine covered with a film of Corrosion-X and have had no leaks since installation more than 10 years and 145K(+) miles ago. More costly quick disconnect fittings generally improve the ball detents (or line contact detents) and internal springs with ultimate corrosion resistant materials, but that just aids in helping a connected air hose to stay connected under abusive strain conditions, not in the strength of the fitting itself. Following the KISS principle, I'd keep the complexity down and trust an already rugged and highly reliable quick disconnect fitting, complimented with a little Corrosion-X once in a while. Adding a valve and more fittings, just raises the probability of some other problem occurring. Best Wishes to all, Neal
Title: Re: Low Air Pressure from Air Hose
Post by: ncaabbfan on January 02, 2011, 10:49:14 pm
Neal, Thank you very much for the information. I will check to see what options I have to do something similar.
Title: Re: Low Air Pressure from Air Hose
Post by: Pierce & Gaylie Stewart on January 03, 2011, 07:32:41 pm
Kent,
I got tired waiting forever for pressure to build for those last few pounds so I just bought a nice used contractor's compressor off Craigslist for $50. It is small but comes up to 125 psi very quickly. I can do a cold morning inflate up to my operating 110 psi all the way around in about 5 minutes. I carry a couple of dbl male fittings so I can pressurize the coach if necessary. I also keep a big military aircraft surplus air tank on board for volume and 25' of LDH to operate my 1" impact for emergency tire changes.
Pierce & Gaylie 93' U300/36
Title: Re: Low Air Pressure from Air Hose
Post by: J. D. Stevens on January 03, 2011, 08:11:08 pm
We carry an electric compressor we bought at Home Depot. I use it for the tires. The last time I used it, temperature was about 25F. I wanted to raise "cold" tire pressure to be appropriate for the ambient temperatures that were much colder than at home. I had planned to use the primary air compressor on the coach. We had been parked for more than a day. When I turned the key, the starter said "Ugh." It didn't even say "Ugh, ugh, ugh!" That was my clue that I would have to use the block heater to get started in cold conditions. We had successful starts in ambient temperatures as low at 5F after leaving the block heater on over night.
I also made a male-male fitting to air the coach system. I tested it and indeed it did work. However, I was surprised by the volume of moisture that I saw blow out of the hose when I disconnected it. I will not use the electric compressor on the coach pressure systems unless absolutely necessary due to the possibility of introducing moisture into the coach's systems. I am not as concerned about using the electric compressor to air the tires.
Title: Re: Low Air Pressure from Air Hose
Post by: Kent Speers on January 03, 2011, 09:47:06 pm
I got tired waiting forever for pressure to build for those last few pounds so I just bought a nice used contractor's compressor off Craigslist for $50. It is small but comes up to 125 psi very quickly. I can do a cold morning inflate up to my operating 110 psi all the way around in about 5 minutes. I carry a couple of dbl male fittings so I can pressurize the coach if necessary. I also keep a big military aircraft surplus air tank on board for volume and 25' of LDH to operate my 1" impact for emergency tire changes.
Pierce & Gaylie 93' U300/36
Pierce, I had the same idea. I presume you bought a pancake compressor. I saw one at a pawn shop for around the same price so I will see if it is still available for just the tires. I have no use for the 1" impact hammer as I never intend to change a tire myself. I'm too old and my back is too bad for that kind of work. Remember, I was a cop not a fire fighter.