Re: Getting ready for a Treadle Vac Replacement

Posted by HH56 On 2015/1/24 0:16:23

IIRC, It was discussed some time back but there were some issues and as far as I know it has never been tried.

Vacuum sealing and power piston guide are a couple of problems since the master bolts directly to the vacuum canister and covers openings and provides the mount area for sealing components. Something to take care of that would need to be machined. The hydraulic piston shaft also provides the guide for the power piston which would be essentially unsupported otherwise. Not sure a regular rod on a modern master will be smooth enough for sealing or large enough to support the power piston and keep it from twisting inside the canister.

The bigger issue is the type of hydraulics. The BTV uses displacement where a relatively narrow ram moves a large distance into a closed chamber to squeeze the fluid out. It can get by with the low 1:1 ratio Packard has. A modern master has to push the fluid a short distance ahead of a fairly large piston area and requires more ratio or boost.

It is thought using a narrow piston master might alleviate some of the additional ratio needs and might be able to work with the Packard geometry. It would be interesting to know if that idea works but don't believe anyone has tried one.