Air Throttle install

[Stan]

Maybe I wasn't clear in my explanation on pressure regulators. The main point I was trying to make was that if you have a Williams treadle with a 70 PSI spring in you will get the 35 PSI out of it at the same pedal position, regardless you feed it with 120 PSI or 50 PSI. The only way to change that is to change the spring in the Williams treadle.

Obviously, if you feed the treadle with 120 PSI and then push the pedal past the required 35 PSI point, you will have get a faster response on the governor pot and this is probably what you were encountering.

[skipn]

Stan,

     Thank you for the clarification..... some days I am just slow....


   Skip

[tomhamrick]

I have completed the install of my air throttle and have not taken it for a test drive yet, but have aired up the coach and run some test. First off, mine is a 84 Eagle with a 6V92TA and HT740. I did install the air modulator on the transmission and the air lines to the modulator and the governor control are the same length from a tee in the engine compartment. I also have installed a pressure regulator and have it set at 70#s of max pressure.  My testing of the system consists of my wife slowly pressing the treddle while I watch the governor and comunicate by radio the results. Then we switch places and she watches the governor while I press the treddle. I have adjusted the stop bolt so that the peddle stop is just prior to opening the air valve to remove that wasted motion but I still have to press the treddle  1/3 to 1/2 of the way to full throttle before getting any movement of the governor. Is this normal? I think I understand the concept of the throttle being an air regulator that sends 0 - 70#s of pressure to the governor, so does this mean that it has to send 1/3 - 1/2 of the pressure before getting any reaction? So then you have only 1/2 of the peddle for feathering the speed? I do get full throttle at full peddle.

Thanks a bunch for the responses!
Tom Hamrick

[Todd]

Check your line sizes - needs to be 3/8" OD
Check for leaks... pressure is going somewhere
Check for free movement - if you can't freely move the throttle lever by hand, don't expect the air cylinder to
Where did you install the regulator - needs to be prior to the threadle

[tomhamrick]

Hi Todd,  Thanks for the reply. I have to answer yes to all of your points and none of those are the problem. Could it be that the return spring is too strong? Guess I could take the spring off and see if it responds sooner.  Thanks again.
Tom Hamrick

[Sojourner]

About the size of air line...the bigger the longer time to fill to raise the responding pressure. Having a long air line from treadle pedal to both modulator and piston equal large air displacement. In other words, slower response time.
In the other hand, a size smaller will decrease time lag.

I have a used William system that came off from NJ Transit and they use 1/4" line but not 3/8".

Question to Jack Conrad....What your air line size? How you like it?

FWIW

Sojourn for Christ, Jerry

[Stan]

Jerry: In normal driving or on cruise control, the treadle is only making small changes in pressure (not filling up the whole line from empty) so there is not difference in response time with 3/8" line.

Tom: Definitely too strong a return spring will inhibit governor arm movement. From reading your last post, I am wondering if you had the engine running during the test. The governor is very hard to move with the engine stopped. The treadle valve should have nearly a linear output with a constant (regulated) input pressure, with a similar response at the governor.

[tomhamrick]

Jerry: Very good point about line size and would seem to apply at the initial application at 0 lbs of pressure when the lines are empty. We were making very slow peddle applications so even with delay we should have had some movement.

Stan: You are correct that I did not have the engine running. I was testing for air leaks and that all components were working correctly. And also so we could here each other on the radio.    I will repeat the testing this time with the engine running and see what happens. I also think I will test with the spring off as well.

I am still curious if anyone else with an air throttle had this experience or if you get immediate response with little initial peddle movement.

Thanks again for all the help!
Tom Hamrick

[Stan]

Tom: I never noticed any problem. With an automatic, you just push on the pedal until you get up to the speed you want. At cruising speed, I found the air throttle overly sensitive and very small changes in foot pressure caused a speed change.

[JackConrad]

  I notice a slight lag when accelerating from an idle. I have been told this is normal and why many with a standard transmission do not like an air throttle (difficult to match engine RPM and bus speed when shifting).  Iniatially, our throttle was too sensitive until we installed a pressure regulator (set at 45-50 PSI). The other problem we had was applying too much throttle due to much less back pressure from the throttle pedal. We started watching our mirror for black smoke from our exhaust. Overall, we are very happy with our air throttle. My right leg is very happy after driving all day.  Jack

[tomhamrick]

Stan: The sensitivity is one of my concerns. If the full governor range is controlled by a small movement of the throttle, then I can understand that.

Jack: Since you are limiting to 50 PSI do you get full throttle? I thought it needed 70 PSI to fully activate the governor?  By the way I saw your Nascar picture in the Southeast Busnuts Newsletter. I bet you are still grinning!   

Tom Hamrick

[Todd]

The actuator used on an air throttle is a single acting cylinder. Force is imparted by air to move in one direction (out), and springs (both internal and external) are used to return to the "home" position.
Force = Pressure x Area
Multiplying the area of the bore (square inches) by the pressure (pounds per square inch) gives the output force of the cylinder (pounds).

60 PSI input pressure x 3.14 square inches = 188.4 pounds of force
This is force that is available theoretically only, as you will likely lose about 5% or so of the force that is available from a specific bore size cylinder just to overcome the friction created by the piston, fittings and rod seals inside itself.

6.37 psi to over come the fully retracted piston internal/external springs
20/3.14 = 6.37 psi

Piston Area - 3.14 in. 2 (20 cm2)
Cylinder Stroke - 0.5 in.

Internal Spring Force with piston fully retracted - 10 lbs.
Internal Spring Force with piston fully extended - 100 lbs.

External Spring Force with piston fully retracted - 10 lbs.
External Spring Force with piston fully extended - 72 lbs.

Don't remove springs! "FMVS" (on highway, unless you are installing this in a farm machine) requires the springs. Not just some silly reg, but protects your engine as well.

Jacking up the pressure is not the solution!!!!! An air modulator is rated at 75PSI. You may be blowing bubbles out your transmission vent.

[Stan]

Todd: I hope you don't wait six months to come back and provide some information. I have a couple of questions that I am sure you can answer.
1. What is the force required to move the governor arm full travel on a 6V92TA?
2. What is the spring constant (k) on the governor return spring?

Having these numbers would make it easier to apply your formulae.

[tomhamrick]

Hey Todd, Don't leave that was great information! I think I have done everything set up as it should be and I am probably confusing the issue by doing my testing with out the engine running. I will not be able to get to that until the weekend, so then I will see how it reacts. When I mentioned removing the spring that was for test purposes only and not for running on the road. Thanks again for the info.

Tom Hamrick

[skipn]

  To further muddy the post.....

   The acuator has to over come the throttle spring and the governor.
resistance from the governor changes from no load to full load conditions.


    True or false?

Skip