A little bit more information to avoid the idiot syndrome
Okay, I estimate it takes about 55 - 60 lbs of force to fully engage the clutch brake as compared to how hard it is for me to pickup a 45lb weight. This is with me grabing the end of the clutch arm and pulling up using one hand placed at the end of the clutch arm. The clutch arm is 12" long and travels close to 4" or slightly under to clutch brake engagement. I have a 13" clutch pedal with a maximum of 7" of travel. If I have a slave cylinder with only 1.4" of travel that means it needs to connect on the clutch arm at (12/4)*1.4=3.6". The force required = 55*12/3.6=183 lbs.
The clutch is NOT an "Easy Clutch". The force to move the clutch out increases with distance.
Now, I want a lighter clutch pedal using hydraulics. Can all the experts help me out now or do I need to give more information? I have no room beyond the clutch pedal once it hits 7" of travel. Can I get it down to 15 lbs of clutch pedal effort? Do I need to use standard master/slave setup and supplement with air?
Constructive comments only please
If I didn't provide enough details ask the questions you need to help me, please.
Thanks in advance for any helpful guidance you can provide.
Hi Brian
I going to assume that the Master cylinder will have to be solid mount / what I mean be this is the Master can rotate as the clutch pedal rotates throw it's arc. So a short connecting link will have to be use between the clutch and Master to take out the arc miss alignment
Do you have a 4in stroke slave? and if you do what size is the bore.
So lets use the slave cyl that you have Bore dia of .88 = .60123 sq in x 100 PSI will give you 60lbs force on the clutch lever. But it has to have a 4" stroke right?
So to move the slave cylinder 4 inches you need to move 2.40492 cu in of oil
The Master cylinder is 1.4 Bore = 1.5393 sq in x 1.4 in stroke = 2.15587 cu in of oil ... so thats NOT ok to move the slave 4 inches ..in would move it 3.58 in
The master in rough terms is 2 1/2 time the dia of the slave so the force in the Master cylinder will have to be 40 psi to get 100 psi @ the slave, so with the lever distance on the petal this will be less.
Hope that help now you have to figure out how much top free petal distance you want and then the distance from the fulcrum that will give you 2 inch + travel on the clutch petal.
Ron
OK, with the additional information, here is a different answer (but probably not what you want to hear):
Again, this is basic hydraulics. An unpowered hydraulic system is a "simple" machine which can provide a force advantage at the expense of distance, or vice-versa.
Likewise, a lever, which is basically what both the clutch pedal and the clutch arm are, provides the same sort of mechanical advantage -- force at the expense of distance (travel).
No matter what size bore and stroke you have on either cylinder, or where on the lever-arms you attach them, it still comes down to moving one lever through 7" of travel to cause the other lever to move through 4" of travel. If the lever arms were identical*, the best mechanical advantage you can achieve without the use of some kind of power booster would be roughly 4/7*(60lbs) or about 34 pounds of pedal force.
It doesn't matter whether you connect the two levers with a cable, push-rod, or hydraulic system. Hydraulics alone won't help -- you still are applying a force through a distance.
In order to get the reduction you want, you will need to either increase the angle of travel of the pedal, or lengthen its lever-arm, or both.
Otherwise, you will need to provide an external source of assistance such as air pressure assist or hydraulic power assist.
HTH. Really.
-Sean
http://OurOdyssey.BlogSpot.com
*Since they are not identical, a closer figure is 12/13 of that number, or 31 pounds, without getting into detailed angular force calculations (the applied force is not always tangent to the travel, etc. and the math changes as the angles increase). And somebody probably ought to check my math, because it's very late and I've had a long day.
The clutch pedal travel is 13" at the foot pad, not at the master rod axis, (you can alway drill new hole) & the clutch arm travel(4") is where the slave will be hook. You may need to find cylinder with specific stroke & bore. Are you upgrading to a hydraulic from a mechanical system?
It's amazing at how every one analyze mechanical, that allow to view all possibility. How about designing an adjustable system so it can be adjust according to your feeling : strong& agressive, easy & soft(for when she drive), & then all to american inventor for the winner!! ::) ::)
Brian: When you first broached this subject, I suggested that you use an air system. The hydraulic system only replaces the connection between the pedal and the clutch. With hydraulics, you can't reduce the pedal force required to push it unless you increase the travel of the pedal or add some kind of external power.
Brian,
For your objective, as others have said, you need an air or hydraulic assist. I think GMs had this available.
Ed Roelle
Flint, MI
Brian,wasn't this transmission a option on MCI and Newells if so way not check with them just a thought they may have everthing you need or can help
I was pretty sure the answer would be "no free lunch". So, thanks everyone for confirming what I thought I had calculated out. I'm going to need to provided a boosted setup then in order to accomplish what I want.
I'm wondering if I should go air over hydraulic or if there are other "boosted" options that might work?
I don't think MCI ever offered the autoshift ... did Newell? If so, does anyone have contact information for someone who might be in the "know"?
Brian,
My seat of the pants solution would be air over mechanical. Lots of Eagles had air assist and the parts are probably laying around somewhere. I sold one not long ago for $100. If not, new is about $700.00.
Len
As has been said, to reduce required pedal effort (without replacing the clutch or something of the sort to reduce required force at the transmission end), you will need to add power to the system to supplement the driver's input.
My scenicruiser originally had an air clutch. IIRC, The clutch pedal was attached to a regulator which sent a signal to an aircylinder at the clutch - This was used with the twin 4-71's. There was a fluid coupling connecting both engines to the 2-spd clutch in front of the 3-spd transmission. Needless to say, these kept the mechanics busy.
When they were repowered in the early 60's with the 8V71, they replaced the air clutch with an air assist cable operated system (with a little less other stuff that would make Rube Goldberg proud). In this current system, there is a air valve in the clutch linkage that sends air pressure to an assist device closer to the transmission. This system is still on most scenics that still have the 4-spd transmission.
SO, to make a long story shorter, using air is the way the manufacturers ease the required clutch pedal pressure & has worked reliably for years.
YMMV
Brian Newell uses a ZF transmission but it has a clutch phone #888-363-9355 MCI does offer a type of auto shift in their 4500
Brian: I think you were going to experiment with an air system. Did you try it and what were the results?
Quote from: Stan on June 21, 2007, 07:06:37 AM
Brian: I think you were going to experiment with an air system. Did you try it and what were the results?
Hi Stan,
I got out the brake valve and hooked it up to air and the air cylinder. It applied air, but I didn't have a good setup to get full air application. I also tested full air pressure directly to the cylinder. My little cylinder just couldn't do the job. It was attached to the arm at 8" instead of at the end as well. I wanted to fully investigate all my options before I go buying more "stuff". However, it is looking like I'll need an air assist anyway and may try a larger air cylinder before going to hydraulic. Just trying to see what other ideas are out there as I know I haven't been exposed to all options and ways of doing things.
-Brian
Hi Brian. We now have two thread going on this subject and I am getting a bit confused as to which one I need to reply to. So, Here is a paste of my reply to the other thread:
>>>>>>>>>>
Brian, as Luvrbus pointed out, I have been working on this issue for a while. Indeed, I think you and I talked about this on the phone once or twice.
When I started, I used all Volvo truck parts. I had to modify the clutch pedal leverage a bit to make it all fit under the Eagle dash. It was a b*^$h to push. Also, I could not get the reservoir to fit and made a stab (didn't work) at a remote unit.
So, I started over on the master cylinder side. A member of the Eagle group had developed an air over hydraulic system that seemed to work great. He used a regular car master cylinder and a air brake can to actuate the master cylinder. I have been playing with that concept as well as a mechanical hand lever system (does not work well at the toll booths, duh Angry). The hand system did work well, but was not the answer I was looking for. I have tried to design all kinds of pure hydraulic linkage systems, but there is not much room in the front of the Eagle.
I will be installing the third master cylinder in the next week. I have done all of the calculations, but it still came down to cut and try.
The one thing I did mention in a previous post was to be sure to use a two wire hydraulic hose for the run from the front to the back. You do not need it for the pressure (less than 800 PSI with my present system), but you do need it to minimize the expansion of the long hose and the associated loss of control.
Have fun! Jim
>>>>
Now, with this new thread, comes some new thoughts.
I think mechanical linkeage is probably not worth trying if it was not in the bus to begin with (your case). All the connections are just asking for trouble. Some folks have suggested cable, but there are still things that wear out in that type of system.
We now have two votes that pure air will work. I have heard some strong opinions (off line when I was working on my application) that pure air did not work for them (one had very bad results).
Pure hydraulic can be made to work, but we don't have much space for a good actuation system (pedal linkage, etc).
So, it it would appear that air over hydraulic or air assisted hydraulic may be your best answer. I am going the air over hydraulic route as noted above (using brake treadle valve). From a pedal pressure point of view, it is great. I am still working on the control capability (too touchy).
I have a friend who has developed an air assisted hydraulic system. He has a control switch on the foot pedal that activates an electric air valve that activates an assisting air cylinder on the clutch arm. He sent me pictures, but we have not had a chance to talk about how effective it is.
Just more thoughts to confuse you :D
Jim
Thanks Jim,
I appreciate all your thoughts and details. Yes, I fully remember our conversation about the different setups you've tried. Thanks for the reminder.
I have talked to a friend who used air and hydraulic. His system works great for him and his pictures showed a good setup. My setup is a little bit different and before I went down a complete refabrication I've been exploring all options. I like the idea of a boosted hydraulic setup .... but it appears the parts are not well known as no examples have been forth coming. I thought of a master cylinder from a car, but don't know how to go about providing reliable (and relatively cheap) vacumn to the booster.
FYI: Just use this thread as I've abandoned the prior thread for obvious reasons.
Brian,
If you need reliable and cheap vacuum, why not try a refrigerator compressor? Hooking it to a spare airtank with a regulator and a check valve would supply all the vacuum you would need.
A plus is that if you found a 12v compressor, like a Danfoss, you wouldn't need to run the inverter to operate it.
Just a thought to move the fabrication along a bit.
Dallas
Hey Dallas,
Good idea ... I'm going to ponder that for a bit ....
Thanks
I must be missing something if you are going to use air assisted hydraulic instead of going straight air. If there are control problems with straight air I think they will be amplified with air assisted hydraulic.
A brake treadle valve does have short travel on the actuator pin so suitable linkage has to be used to get good control but there are many bleeder type air pressure regulators that would be easier to control. On some, you screw in the adjustment about 2'" to go from zero to full pressure. On almost any regulator you can change the spring to get the maximum pressure you need for full travel of the slave. This would be easy with a air throttle control without the treadle and using a suitable lever to get longer travel for better control.
If you are only using the clutch for initial start with an autoshift, then it doesn't matter if it goes all the way to the clutch brake so you don't rally need that delicate part way down on the pedal.
Brian,why not get you a hydro boost off a GM car or truck that way you do not have to have two different component's to work your clutch
Quote from: makemineatwostroke on June 21, 2007, 10:38:14 AM
Brian,why not get you a hydro boost off a GM car or truck that way you do not have to have two different component's to work your clutch
What is a hydro boost?
Brian,we converted 5 MCIS for a charter co here in Houston that wanted better fuel mileage the process is simple you can mount the Hydro booster in any position you want mount the reservoir any place and run lines to the booster all you have to do is make sure you can get the pedal rod to it tap your power steering lines flow and return use a good slave Cly with a adjustment on it and you are good to go you can buy rebuilt units from auto parts stores like Napa or buy on from the wrecking yards they were on lots of GM trucks and wagons i called the shop to see if they had any drawings left around if they find some i Will post or email them to you
Brian,
Unless you plan to use aircraft hydraulic fluid I would strongly suggest forgetting the hyd part. Auto hyd fluid attracts water like mad and will cause rust and leaking. This is even worse on a bus that is not used daily. There is nothing to be gained by adding the headaches of hydraulics into the clutch system.
I have a bunch of antique vehicles of all sizes, hyd brakes and stale gasoline are my two worst headaches. The ones with mechanical or air brakes never seem to have any problems.
Brian,the power steering pump runs the system it has brake fluid from the unit to the clutch
Straight air operation, using a treadle valve, is traditionally considered a bad choice for clutch operation because it eliminates almost all feedback, thus preventing the operator from "feeling" the friction point of the clutch, generally considered an important control function. This is why power-assisted mechanical or hydraulic linkages are generally used for this application.
Here is one after-market air-assist system that is a straight bolt-in:
http://www.hbindustries.us/air.htm
If you want to roll-your-own, air assisted clutches are common on heavy duty trucks, and you can probably find all the parts for a complete system at a truck salvage.
FWIW.
-Sean
http://OurOdyssey.BlogSpot.com
Hello.
I am only able to contribute this bit.
I would want to keep the ability to access the clutch brake in an autoshift application.
The computer will only engage the gears within a certain rpm band, and it is very easy to have the bits and pieces spinning above that band.
You will wait and wait to start off, in a situation that you would prefer to go now, if you could only get the internals to slow their spin.
This from a guy who has to teach others how to run a sewer sucker truck with one in it, unionized environment, so you know who gets forced into sucking sewers...
Push the clutch in early coming to a stop, touch the throttle while sitting still, disengage the fast idle, all leave the tranny spinning inside too fast to engage a gear.
happy coaching!
buswarrior
Sean: Do you know what is inside that cylinder, in the clutch rod, in the ad you linked to? I assume the rod from the pedal is connected to a control valve of some sort with a big spring behind it that determines the amount of pedal force required in order to get air to the assist cylinder.
BTW: I installed an air operated clutch using a modified brake valve and drove it about 50k miles without problem.
Hi Brian. I use only the master cylinder and do not use any vacuum chamber. I selected a version that has a screw on top that makes pressure bleeding easier. However, I have not had to do any pressure bleeding since I abandoned the Volvo master cylinder. Something in the system would not allow normal bleeding processes including pulling a vacuum at the slave cylinder.
The vacuum chamber in a car obviously reduces the pedal pressure. That is not an issue with an air brake chamber system. Indeed, I have to be very careful not to apply full pressure as it over-pressures the hydraulic system. I will put a pressure regulator in the system when I get done playing. Right now, I have a large hydraulic pressure gage that I watch when I engage the clutch.
Jim
Quote from: Stan on June 21, 2007, 05:30:27 PM
Sean: Do you know what is inside that cylinder, in the clutch rod, in the ad you linked to? ...
Sorry, I don't. Hey, I have an Allison ;D
That being said, generally, there is a standard process for proportionally adding power boost (whether vacuum or air) to a hydraulic system, whether that's a clutch, a hydraulic brake, or even power steering. Here's a good explanation (from vacuum-assist brakes, but you can see the general idea):
http://auto.howstuffworks.com/power-brake.htm
(Just remember that vacuum assist is applied to one side of the diaphragm, while air assist would be applied to the other side.)
HTH.
-Sean
http://OurOdyssey.BlogSpot.com
Quote from: rv_safetyman on June 21, 2007, 05:36:59 PM
Hi Brian. I use only the master cylinder and do not use any vacuum chamber. I selected a version that has a screw on top that makes pressure bleeding easier. However, I have not had to do any pressure bleeding since I abandoned the Volvo master cylinder. Something in the system would not allow normal bleeding processes including pulling a vacuum at the slave cylinder.
The vacuum chamber in a car obviously reduces the pedal pressure. That is not an issue with an air brake chamber system. Indeed, I have to be very careful not to apply full pressure as it over-pressures the hydraulic system. I will put a pressure regulator in the system when I get done playing. Right now, I have a large hydraulic pressure gage that I watch when I engage the clutch.
Jim
So, you are using a master cylinder, single I assume, without vacumn assist. So, where does your air assist come in to play? I'm having a hard time picturing the system given the information provided.
Hi Brian. It thought I had a picture, but I can't seem to find it.
The master cylinder and the air brake chamber are mounted on a common fixture. Right now I have that fixture on the floor beside the driver seat. The air brake chamber rod center line and the master cylinder center line are the same. I made a rod that threads on the air brake chamber rod (for adjustment) and that rod pushes on the piston of the master cylinder. Pretty simple to fabricate.
Let me know if that makes it clear. If not, I can try to take a picture, but it is pretty crowded in that area.
Jim
Jim, does that mean your clutch pedal pushes on a valve to allow air into the air brake chamber diaphram?
Yes. My clutch pedal is actually a brake treadle valve. It applies air to the air brake chamber. The air brake diaphragm then pushes on the brake rod which pushes directly on the piston of the master cylinder. Pretty simple. Only problem is making it more sensitive to pedal movement (i.e. make it feel and act like a real clutch pedal).
I will be off line for a couple of days to go play in the woods. If there are more questions, I will be back on line Monday.
Jim
This discussion is frying my brain. I just "invented" the concept shown here. I'm sure it's not new but it is to me. Two hydraulic cylindres of different proportions mechanically interlinked to provide assist.
What do you think guys? It looks like it should work but figuring out the numbers or if it is practical is beyond me.
I'm sure you hydraulic engineer types have a common name for this setup.
Len
Quote from: Len Silva on June 22, 2007, 10:11:18 AM
...I just "invented" the concept shown here. I'm sure it's not new but it is to me. Two hydraulic cylindres of different proportions mechanically interlinked to provide assist.
What do you think guys? It looks like it should work but figuring out the numbers or if it is practical is beyond me.
I'm sure you hydraulic engineer types have a common name for this setup.
Umm, I don't think there is a common name because it doesn't exist.
Putting any kind of "black box", whether it consists of hydraulic cylinders, a bunch of gears, or fairy dust, in between two ends of a linkage can't, under any circumstances, alter the force*distance equation, unless that black box is connected to a source of power (such as an external pump, or a source of electricity). That's simple physics -- it's the First Law of Thermodynamics.
I invite you to build such a system, and press on one end to see what happens. I assure you, it won't help Brian with his problem.
Brian put it very well when he said "There is no free lunch" -- a great description of the First Law.
-Sean
http://OurOdyssey.BlogSpot.com
Yeah, I see it now. I need to learn to sit on these things for a while before posting. I do occasionally have ideas that do work. :)
Len
How about a hydroboost master cylinder from a GM truck? I think the biggest issue might be not having any boost without the engine running.
Would this cause any issues with the existing powersteering system?
I forgot who mentioned the hydro boost, but my initial google search makes it sound promising. The only "negative" is having brake fluid in the mix ....
I have a 1 ton Chevy truck with this on it it works off the power steering pump and you can use it 4 time with out the engine running after you stop you still have brake but the pedal is hard to push after the 4 times and you are going to have brake fluid unless you go with a complete air system and then no clutch with out air
The Bendix Hydraboost is far in excess of your needs. It was designed to stop 10,000 pound vehicles. You want an ASSIST, to lessen your pedal effort.
Ed Roelle
Quote from: edroelle on June 23, 2007, 05:55:54 AM
The Bendix Hydraboost is far in excess of your needs. It was designed to stop 10,000 pound vehicles. You want an ASSIST, to lessen your pedal effort.
Ed Roelle
Hi Ed,
Do you have any alternative suggestions?
Would a standard MCI clutch air assist cylinder be any help? Maybe two of them side-by-side would give more assistance? Good luck with it. I'd love to lighten my clutch a bit, too.
David
Brian,
I am not sure of what the answer is, but a brainstorm session with Jim Shepherd, Sean, Jerry, and others would come-up with the best design.
To assist your pedal effort, you need a power source - hydraulic, air, vacuum, or electric. Levers or unpowered cylinders will not do it alone.
Try for simplicity and proven durable componenets.
I have not understood all of the discussions, so this may duplicate Jims or piggyback on some others. (I understood Jim's design to use both air and hydraulic components.)
How about using as components, the very smallest brake can, a brake treadle valve, a proportioning valve (I am familiar with hydraulic prop valves but are there air proportioning valves in the trucking industry?) and possibly other valves. The brake treadle valve would be connected to the clutch pedal with an output air line to the brake can. The brake can would be connected high on the clutch pedal to assisst your pedal effort. (Max brake can stroke to equal or be greater than max clutch pedal movement at the pin connection.) As you press on the clutch pedal, you open the treadle valve to the brake can, to assist in the effort on the pedal. The proportioning and other valves would allow for developing the "feel" of the pedal.
This would take some develpment as Jim is demonstrating. I would suggest building a mock-up of the design to do the development work.
Others inputs are desired.
Ed Roelle
Flint, MI
Ahoy, Brian,
Eagle clutch
Here are a few comments on my experience with clutch actuation on my Eagle-01.
First off, the engine which I installed in my Eagle is an M-11 Cummins 400 hp, and the Clutch is a 14" double disc item. I don't recall the model but even though it is the strongest 14" unit available, it is a bit marginal on capturing the torque of the engine. The transmission is a Roadranger ten speed overdrive RTO1110.
My first clutch try was an air operated unit. Friend Andrew had an air actuated clutch in his classic Cortez Twin Coach with a 505 Cummins, 5 spd trans and a single disc "old" clutch. It worked fine. My installation did NOT. Behaved like a dog clutch!!!! It was so abrupt that my Eagle was not driveable. So, I finally did a little engineering and a few tests. I measured the force (air pressure) for clutch actuation right at the clutch arm. For the cylinder size which I had installed, the air pressure at the first ~~1" of travel was about 61 psi, and for full stroke, about 65 psi. No wonder it did not work. It was behaving like a dog clutch. I suggest that if you have a "modern" double disc clutch, don't even try any actuation method which does not include positional feedback to your clutch pedal. I expect that the older single disc clutches have some reasonable relationship between stroke and actuation force. My modern double disc clutch does not.
I installed a hydraulic clutch actuation system which was comprised of two cylinders of 1" bore and 6" stroke. They use ordinary red mineral hydraulic fluid. There must be a bleed process for the system, and the way I did mine was to use a solenoid valve ported from the high point at the actuator cylinder to the reservoir. . It is normally closed, and opens with a micro switch when the pedal is ~~ ¼" from all the way up. The actuating cyl is mounted so that the pressure end where the solenoid valve is mounted is high. It works just fine. At the clutch, you must have a light spring to keep the actuating cyl extended The nice feature of this setup is that you don't have to play with the position of the cylinders. As long as all the strokes are within cylinder actuating range, you are just fine, with the starting point being established by the bleeder solenoid and micro switch combo. You must devise a pressure pot system to bleed this setup. I use a modified old stainless steel fire bottle. Clean and easy to find.
The hydraulic hose which I used to connect the cylinders was a two wire -4 hose (1/4") about 35' long. It was something that I had on hand. The fluid friction in the long small diameter hose made it too slow to double clutch properly. Easy fix -- Just thin the fluid with mineral spirits – NOT!!! The reduced lubricity caused friction and o-ring wear problems in the cylinders.
Bigger hose – About $175 worth of -8 one wire hydraulic hose (1/2"). Diametral expansion of the hose resulted in insufficient clutch arm travel.
Back to the (CAD) drawing board. I installed stainless steel tubing (½" OD) with short pieces of the -8 hose above to connect to the cylinders. It all works just fine – finally.
I plan to add an assist system to my clutch. Probably just be an air cylinder sized an stroked to reduce some of the force. Actuation will be by a solenoid valve triggered by the micro switch mentioned above. Again, the components must be sized so that the pedal actuation is not slowed.
Enjoy /s/ RHB