[blucar]

I have been involved with the rebuilding/restoration of the top assemblies on two '39 Plymouth convertible coupes during the past ten plus years.. The '39 & 40 Mopars used vacuum cylinders to raise/lower the top.. The '39 Plym's were the first open car to have a power operated top..
As the need to have the top assemblies rebuilt came closer, I called ever source in the U.S. that I could find, to no avail.. I finally found a man in Colorado that said he could rebuild the vacuum cylinders, $500. per pair.. I finally decided to go with him, boxed them up, addressed them and was ready to send them off.. I called him to let him know the cylinders were going out.. Left a couple of messages which he did not return. After waiting a few days I called again, number was out of service. Sent a letter, returned, addressee unknown..
I finally told myself, self, it looks like you are now a vacuum cylinder rebuilder.
Disassembling the cylinder showed me that the parts were similar to a Columbia OD rear axle vacuum can.. Which is similar to the old time, hand operated, tire pumps.. A leather plunger on a steel shaft, pushed/pulled within a metal tube.
The operating shafts were badly rusted, on one set of cylinders the shafts, etc., were frozen into the canister.. Soaking in oil... Neats Foote leather oil solved that problem..
Addition soaking of the leathers in Neats-Foote oil softened the leathers right up.
I honed the bores of the cylinders with a "bottle brush" type of bore hone..
The upper bushing within the caps were worn, but in good shape. The leather shaft seal was in poor condition.. A visit to a plumbing supply provided good shaft seals.
The shafts were a problem.. They are approximately 1/2" OD, originally chrome plated which I found out is called "Hard Chrome".. i.e. Hard Chrome plating is completely different that chrome trim plating.. Hard chrome is a very costly process, the object being that it is done over size, them turned on a lathe to the required size... Aircraft type of work..$$$$
I searched around for a machine shop that would do small jobs, asking if they could custom make shafts out of stainless steel.. I finally found a shop, took my shafts to them with the instructions to make the new shafts identical to the original ones except slightly over size. I had measured the bronze bushings in the cylinder caps, arrived at an average size which corresponded to the overall shaft size. The bronze bushings were honed to match the shaft size..
My biggest expense was having the shafts made, after all was said and done I ended up with a few hours of labor and an overall cost of about $300. per pair of cylinders.
I found that one of the secretes to making the vacuum cylinders work right is the heavy return springs that was originally incorporated into the system.. These springs attach to one of the arms for the top and into the floor of the car.. They work similar to the old garage door springs to assist the lifting of the door, i.e. lifting of the top.
The majority of owners of the '39-40 convertibles do not know these spring exist. My car had them, where-as the other '39 did not..
After much checking I finally found a company that could make the return springs, I had to have ten (10) sets made.. If anyone is interested they are $120. per pair plus shipping..