more boring clutch boost ideas... :)

[bevans6]

So I have been continuing to think about this.  I've found that vacuum boosting the clutch is actually quite common, a lot of cars and trucks have vacuum boosted clutches stock.  They are all hydraulic, and set up in exactly the same way as the far more common vacuum boosted brake systems.  So I said to myself, maybe this is a good idea after all.  An 8" diaphragm with 23" of vacuum can develop up to 500 pounds of push, that would reduce my clutch pedal pressure to less than half what it is now.  Then I thought "Why go to all the trouble of converting the mechanical push to hydraulic and then back to mechanical?  Maybe you can do this with a fully mechanical system..."  My MCI clutch pedal operates through a series of bell cranks and push rods.  The basic pedal ratio to the first bell crank is 6:1, so a 6" travel on the pedal converts to a 1" motion at the bell crank attachment.  If I put a pedal in with a 6:1 ratio that can push directly on that bell crank, and put a booster on the push rod, I will get the same boost as I would with a hydraulic system but directly into the stock mechanical setup.  How easy would that be, and it would work just like stock (IE way too high a pedal pressure but usable) if the vacuum boost system failed.

So that is my thinking at this point on a cold but sunny Saturday morning...  This idea has the benefit of retaining just about all of the stock system, it's just a small change at the pedal end and you can convert back to fully stock in about an hour.  The major downside is that it retains just about all of the stock system, which is a great thundering long and complicated bunch of levers and arms and joints...  A dilemma indeed...   

Brian

[lostagain]

An important consideration would be to retain smooth clutch feel. You don't want to end up with an easy push with an abrupt engagement. Think about starting from a stop. Up a hill. In stop and go traffic... "Drivability" is essential. I guess you could build something and try it. Good luck.

I love the automatic in my bus. After 40 years of shifting all kinds of manuals.

JC 

[TomC]

Instead trying to experiment-maybe several different ways ($$$), just convert to an Allison automatic. I drove 13spd truck for 21 years and 1.3 million miles-and can say without a shadow of a doubt I LOVE my Allison Automatic (V730) in my bus.
So much so, I took out the 13spd in my truck and had an Allison HT740 installed for my truck conversion. Once you change to an automatic, you won't believe the difference in driveability, acceleration, and just having a big smile on your face everytime you drive. Instead now of frowning and dreading each time you shift. Good Luck, TomC

[bevans6]

Advice on how great an automatic is, is wasted - ain't going to happen.  I could care less how great they are when the cost is more than the bus is worth, and when I don't have the money in the first place.  A clutch booster, now that I know such a thing is possible and actually works, will cost be about $100.  That I can afford...

Brian

[chessie4905]

   Our 4104 had an air assist clutch and it worked excellent. The pressure regulator could be adjusted to have little pedal effort. I think HB industries used to sell them and I read somewhere they were used on some otr coaches. Maybe someone here or on the other board can find you one at a reasonable price. I would consider calling Luke about it also. The clutch release rod that connects to the clutch arm at trans bell housing, has a 4" piece removed and movement sensor is welded/attached in place. Air line goes from pressure regulator to this sensor. line comes out of other end of sensor and goes to air cylinder that is attached to clutch release lever, parallel to clutch rod. The sensor is 4 inches long by 2 or 21/2 inches in diameter. Once the pressure regulator was adjusted to suit, it never needed any service or adjustments. Pedal pressure like a car and no engagement or release issues.