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Author Topic: Air Throttle install  (Read 3319 times)
tomhamrick
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« on: March 11, 2008, 06:58:06 AM »

About to install an air throttle on a 6V92 TA. Anyone have pictures of their install so I can see how it looks? Also where did you get the governor mounting plate and lever assembly?
Thanks,
Tom Hamrick
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Tom Hamrick
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« Reply #1 on: March 11, 2008, 07:27:06 AM »

Hey Tom
I just did the same on my 6v92 and needed the same parts. if you go to the williams air throttle site and go to the catalogs there is a page that shows all the parts and the part numbers. after that call
Brake Systems Inc. in portland oregon at 800-452-5734. they buyout all the old stock and over stock from williams and have or can get anything. following are the part numbers and prices of the parts I just got
WM775B-  modulator for HT740 trans     $56.11
119050 mounting bracket                     $22.59
117404  return spring                          $9.17
117908  lever assymbly-long                 $11.86
shipping                                            $11.86
total                                                 $139.62
if I get a chance I will get a photo of mine if it helps. I modified the original plate to mount the shut down solinoid and the one that locks out the throttle on high idle. havent had the chance to start it up yet so hopefully it all works right.
Steve Schmidt
'81 Eagle model 10
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luvrbus
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« Reply #2 on: March 11, 2008, 07:35:20 AM »

Tom, mine came from a DD dealer  if you look on Tom Halls site Coach Conversion Central you will see the one I have made for a Detroit also if you need mounting instructions look at    www.utxchange.com   and they will parts also  good luck
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Stan
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« Reply #3 on: March 11, 2008, 07:40:00 AM »

When ordering from Williams you have to be very specific on what model engine and if automatic whether you are using an air or cable modulator. I installed one on an Eagle with 692 and 740 with cable modulator but the owner hadn't specified that when he ordered it. It wouldn't come up to full speed and wouldn't shift properly. The cable modulator presents some mechanical load that has to be compensated for with more air pressure. Williams sent me a new spring and shims and instructions on how to set up the treadle valve.  Everything else came with the kit.
On my own 8V71 with a cable modulator I bought a used unit and just made a bracket out of 10 gage plate so that the air pot pushed on the governor lever the same as the original foot pedal rod. In my case, the treadle valve was too much pressure so I put a stronger return spring on the governor lever to make the foot pedal less sensitive.
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luvrbus
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« Reply #4 on: March 11, 2008, 07:52:29 AM »

Tom, Stan made my point about the air modulator it is the best way to go 60 bucks is not worth the hassel to me     good luck
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tomhamrick
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« Reply #5 on: March 11, 2008, 08:29:36 AM »

You guys are great!!!! Thanks for all the information.
Tom Hamrick
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Tom Hamrick
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« Reply #6 on: March 11, 2008, 08:45:12 AM »

Steve,
A picture would be great if you can get one. My email is tomhamrick at yahoo dot com.

All,
Did any of you use the pressure regulator? If so what type and what pressure?
Thanks Again!
Tom Hamrick
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Tom Hamrick
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« Reply #7 on: March 11, 2008, 09:15:57 AM »

Tom,
   We used an adjustable pressure regulator from Northern Tool.  We set ours at 50 PSI.  We found this to be the best setting for us. A lower setting gave us a very "mushy" throttle. A higher setting made the throttle too sensitive (a slight movement of throttle pedal= large increase in engine RPM). We played with our settings for a few short trips to find what was comfortable for us. YMMV  Jack
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« Reply #8 on: March 11, 2008, 10:32:12 AM »

As Jack pointed out, you are aiming for full stroke of the pedal to give full stroke on the governor. That is Williams reason for different springs and shims in the treadle valve (which is just a bleeder type adjustable pressure regulator). You cannot obtain full stroke on the pedal if you reduce the inlet pressure below the maximum pressure of the treadle valve so you have to adjust it to whatever you are comfortable with. I think varying the return spring tension does more for pedal control than changing the input pressure. At full pedal travel, you can adjust the return spring tension to just allow full governor travel.
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skipn
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« Reply #9 on: March 11, 2008, 11:43:47 AM »


   FWIW,

   I tried the spring thing.....wasn't real happy with the results mostly due to 2 things.
     when I was working on the engine it was hard to move the lever to high idle (spring was too stiff for
     my liking)

   With the heavier spring I had to wait longer to press the foot peddle to high RPM. (wait for air pressure to build)
     Being I have a transplant engine it doesn't have a high idle switch.

   I have my regulator set at 55psi seems to work fine and I now have some throttle control at 40 psi at air up time.

  Skip
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« Reply #10 on: March 11, 2008, 02:13:00 PM »

    Here is a photo of the air throttle actuator on the governor and the pressure regulator.  The pressure switch in the air line on the governor is part of the Jake Brake switching circuit.  Jack
« Last Edit: March 11, 2008, 02:14:37 PM by JackConrad » Logged

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« Reply #11 on: March 11, 2008, 05:51:12 PM »

skipn: Do you have the regulator feeding the air pot on the engine end? Since I used the original return spring and just used a piece of all thread to make a way to adjust the tension, I am thinking that the output pressure from your treadle must be away higher than required.

To make for easy calculation, if your treadle valve has a maximum output of 110 PSI and you are using a 55 PSI regulator (at either end) then you would only be using one half of the pedal stroke.
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skipn
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« Reply #12 on: March 11, 2008, 08:18:01 PM »


 The regulator is inline to the feed of the treddle. Before the treddle would go from 0 to 120# with
 just the slightest movement of the peddle. With 55# max to the treddle and then  55# to the diaphram max
 I can  now feather the throttle. It goes to the high limit without any problems.

   Not saying what I did is the best way but it seems to work ok.


   Thanks
 SKip
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Stan
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« Reply #13 on: March 12, 2008, 06:31:47 AM »

skipn: It sounds like your treadle valve is acting like an orifice control instead of a regulator. Consider an ordinary valve that you  open 10%, the pressure will rise to the supply pressure, just at a slower rate than if fully open. When you open a regulator 10%, the pressure will only rise to 10% of the maximum for that particular regulator. If the spring in the regulator sets the maximum at 50 PSI then opening the regulator 10% will give you a maximum of 5 PSI out. One type is a flow control and the other type is a pressure control.

I have worked with two different types of air throttles and they both used a bleeder type pressure regulator for the treadle valve. I have been assuming that all throttle treadle valves worked that way but apparently not. Sorry for creating any confusion but I just don't understand how an orifice type valve could be used to maintain a steady speed. According to this catalog page, a Williams treadle valve is a pressure regulating valve with a maximum output of 70 PSI and as I said in a previous post, Williams can supply springs to provide whatever max pressure you want.
http://bepco.biz/AirBrakeCat/148.pdf
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skipn
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« Reply #14 on: March 12, 2008, 06:52:58 AM »


  Very true in what you write. The thing that I might inject here is that the treddle goes from 0-70# but depending on
 the air throttle cylinder being used it may only require 0-35# as in the link you provided. So at half peddle travel of 70#
  input you get 35# at the throttle cylinder (full throttle). I am not real sure which throttle cylinder I am using but the one thing
  that drove me to irritation was in a 700 mile trip not being able to feather the throttle thus I was either accelarating
  or coasting the whole time. I rode in a bus for 12 hrs once with the driver doing that by the end of the trip I was
  really really cranky (pick a speed and hold it there) He probably had a tired right leg too Smiley.

  Springs are probably the correct method but for me I do the best I can with what I know. I will have to research this
  more. Thanks

  Have a wonderful day
  Skip
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Stan
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« Reply #15 on: March 12, 2008, 08:04:27 AM »

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.
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skipn
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« Reply #16 on: March 12, 2008, 08:27:55 AM »


 Stan,

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


   Skip
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tomhamrick
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« Reply #17 on: April 29, 2008, 07:21:43 AM »

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
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Tom Hamrick
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« Reply #18 on: April 29, 2008, 08:14:55 AM »

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
« Last Edit: April 29, 2008, 08:21:50 AM by Todd » Logged
tomhamrick
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« Reply #19 on: April 29, 2008, 09:51:50 AM »

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
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Tom Hamrick
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« Reply #20 on: April 29, 2008, 11:20:40 AM »

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
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« Reply #21 on: April 29, 2008, 11:39:28 AM »

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.
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tomhamrick
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« Reply #22 on: April 30, 2008, 02:42:55 AM »

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.  Grin  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
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« Reply #23 on: April 30, 2008, 05:09:24 AM »

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.
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« Reply #24 on: April 30, 2008, 05:40:11 AM »

  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
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« Reply #25 on: April 30, 2008, 10:06:07 AM »

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!   Grin

Tom Hamrick
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« Reply #26 on: April 30, 2008, 11:18:11 AM »

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.
« Last Edit: April 30, 2008, 09:57:02 PM by Todd » Logged
Stan
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« Reply #27 on: April 30, 2008, 11:37:31 AM »

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.
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tomhamrick
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« Reply #28 on: April 30, 2008, 12:33:18 PM »

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
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Tom Hamrick
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« Reply #29 on: April 30, 2008, 01:15:18 PM »


  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
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« Reply #30 on: April 30, 2008, 01:44:37 PM »

I moved an obnoxious (at least in my opinion) post to the Moderators board for review.

Richard
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« Reply #31 on: April 30, 2008, 02:18:14 PM »

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!   Grin

Tom Hamrick

YES I AM!  WOW WHAT RIDE!!!
    We get full throttle according to our tach.  Jack

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