Re: Bendix Treadle Vac Study- Serioius Business!!
Posted by HH56 On 2010/12/4 18:40:05
Will yield to any better info but believe there will be a stamp on the end of hydraulic cylinder. If that is correct, of course would only be good as long as cylinder was original.
I never found anything readable for the vacuum part on the outside and never looked for it on the piston casting so there may be something there. If not, I think by taking the end plate off and looking at hose side of the piston you can tell. Sleeve type has the actuating rod entering a mostly squared part of the casting surrounding the round cylindrical opening for the rod connection. The poppet valve type has that same area to be more rectangular or oblong with the casting having areas for the poppet valves either side of the rod opening. One side is larger than the other. Also, I believe the early P1 or P2 units had a separate hose connection for the breather vent as well as a connection for the vacuum source. Later ones just had the breather under the rectangular cap. I believe most of the sleeve types were obsolete by early 53 for Packard.
Don't believe Packard ever used the hydraulic reaction type. That one has the familiar ram type cylindrical piston rod but with a shaft in it. A seal and membrane at the fluid end of piston that works the rod and pushes it back into the vacuum piston to modify the vacuum depending on force.
I would also be very interested in hearing what the differences in operation or response are for the various units since they do look virtually the same P3 on. I think Packard only went as high as P5 but won't swear to it. I really can't say that I ever noticed any differences in driving.
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I never found anything readable for the vacuum part on the outside and never looked for it on the piston casting so there may be something there. If not, I think by taking the end plate off and looking at hose side of the piston you can tell. Sleeve type has the actuating rod entering a mostly squared part of the casting surrounding the round cylindrical opening for the rod connection. The poppet valve type has that same area to be more rectangular or oblong with the casting having areas for the poppet valves either side of the rod opening. One side is larger than the other. Also, I believe the early P1 or P2 units had a separate hose connection for the breather vent as well as a connection for the vacuum source. Later ones just had the breather under the rectangular cap. I believe most of the sleeve types were obsolete by early 53 for Packard.
Don't believe Packard ever used the hydraulic reaction type. That one has the familiar ram type cylindrical piston rod but with a shaft in it. A seal and membrane at the fluid end of piston that works the rod and pushes it back into the vacuum piston to modify the vacuum depending on force.
I would also be very interested in hearing what the differences in operation or response are for the various units since they do look virtually the same P3 on. I think Packard only went as high as P5 but won't swear to it. I really can't say that I ever noticed any differences in driving.
Attach file:
(33.33 KB)
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