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Thomas Leveling Compressor

Yahoo Message Number: 83337
Hi,

On our bus the Thomas compressor's air outlet is connected to the leveling system via a plastic insta-tube. Obviously those conceiving of this didn't understand that compressing air creates heat. And at high pressures (the Thomas is a high pressure unit) this heating effect can be significant. Significant enough to melt plastic and blow a pinhole in the tubing. Those parking on ground that might create an "excess slope" condition may have this problem. The compressor can run for up to 20 minutes before the system figures out it can't level. Lots of heat gets generated at the cylinder head in the process. Here's my write-up for those interested:

http://www.muniac.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=146#Post146 It includes what I did to rectify the situation.

Best - Scott

2006 Allure 430 40' #31349

(Bus-Stead Lemon) My Allure Page http://www.muniac.com/Allure%20Page.html

Re: Thomas Leveling Compressor

Reply #1 –
Yahoo Message Number: 83362
Hi Scott,

Always look at your stuff and see what I have, great input. I have looked at my pipe and I have a plastic pipe, but I want to check the connection at the compressor end, it is a rotating elbow, is this the design or is it loose????

Kind regards

Michael Slater
2008 Allure 31683

Re: Thomas Leveling Compressor

Reply #2 –
Yahoo Message Number: 83363
Scott, where did you purchase the copper tubing and fittings? Thanks, John 2003 Allure 30951

Re: Thomas Leveling Compressor

Reply #3 –
Yahoo Message Number: 83364
Michael - Mine was this way too. Some sort of swivel arrangement I gather to allow movement and/or guarantee proper orientation for tubing runs. We were somewhere in W. Virginia in the hot Summer heat and the bus wouldn't level. It happens. Then it wouldn't level in spots that I know it should be able to. An investigation of the compressor feed line revealed the problem I documented in my article. Luckily the hole was close to the cylinder head. I cut that part off and re-inserted the tubing in the connection. This got us leveling again but didn't solve the problem.
In hot weather and when sun beats on the steer bay door and if the compressor runs a long time the hose can melt. This isn't an issue for everyone. There is also a vibration issue to deal with. The copper tubing I made has been in place for about 4 years. No problems so far. There are special high temperature braided SS flex hoses that might be better than my solution. The gist of the article is to draw attention to this situation and suggest "one" solution. Others exist, however, and I hope owner/operators bring them forward for consideration.
As for leveling, there is a sensor board in the HWH control box in that same bay. The mounting of this board is also sketchy. It's designed to provide "calibration" of the level sensor with respect to the frame of the vehicle. The signal from this board is, in effect, what the HWH controller sees to establish a level condition. Mine kept loosening up making for a funky looking bus. It was like walking in one of those fun houses. I'll try to write this one up as well. I wound up putting a rubber grommet in there to tighten the mount and hold registration. I also made a simple level calibrator to help the adjusting process along.
I'm glad you're finding the articles helpful. Isn't networking great! Thanks for the kind words and safe travels.

At 07:55 AM 10/21/2012, you wrote:

Re: Thomas Leveling Compressor

Reply #4 –
Yahoo Message Number: 83365
John - These items are readily available at a local hardware store (or the homo depot). You'll want soft copper tubing (1/4" is fine) and flare fittings that terminate into 1/4" FPTs. If you don't have a flaring tool, you'll need compression fittings. A tubing bender and tubing cutter are also required. You'll need to allow for the compressor's resilient mounts. I handled the copper line run in a unique way. Shown in article photo.

At 08:10 AM 10/21/2012, you wrote:

Re: Thomas Leveling Compressor

Reply #5 –
Yahoo Message Number: 83375
Why not use ARB hose which is designed for on board air compressors which reside under the hood next to a very hot engine. The hose comes with quick connect slip fittings.

Dan 2006 Allure 31348