1941 Antenna Detail

[autoluke]

I am considering replicating my 1941 vacuum antenna , and need to find details for the upper brass connector.  Seems to have a small copper tube encapsulated inside a plastic insulator.     

Any suggestions ?

[Barry M Wheeler #2189]

Which antenna? The 60S cowl one is a lot smaller than the fender one.

[Jeff Maltby 4194]

Rubber cups on pistons...very interesting with 48-9 having leather seals, then rubber seals again in 1950 up.

[Paul Phillips]

Phil
I have my 41 antenna apart now so I can take pictures and semi-precision measurements.  Please refer to Jeff's picture attachments as to the callout reference of part(s) you are interested in.

Paul

[Jeff Maltby 4194]

Paul, does yours have leather piston seals ?

[Paul Phillips]

Jeff - mine has the 1" nominal diameter body and leather seals

Paul

[autoluke]

I have two units on the bench.
1 5/8" OD Tube

1 1/8" OD Tube

Thinking that the larger diameter was used on all 1941 fender mounted units, and the smaller one on the cowl mounted 60S.

Anyone know if there were other designs used on the later 1946 to 1950 cars ?

Also, would appreciate any cross section details for the brass connector fitted  to the top of the tube .

[Jeff Maltby 4194]

Here's a 40-41 ? and a 49 antenna side by side.

[Paul Phillips]

Phil
Are you looking for info on the antenna cable connection (items J - N in the diagram) or the coupler (item O)?

Jeff
That looks to be a fender mount version of the 40-41, based on the top fitment.  I have one reference that also suggests the mast is different on the cowl mount.  Barry is going to try to measure the collapsed height on his cowl antenna, which may add useful data.  Without a shorter mast, there would appear to be be no way to install or remove a cowl antenna, unless something structural is cut away.  This is an open question in another thread.

Thanks
Paul

[autoluke]

Paul

Items O and P....a cross section would be helpful, showing exactly how the antenna cable signal transmits to the mast.  I have the brass top fitting and am considering a replication without deconstructing the part..could do some damage.

[Paul Phillips]

Phil
I will see what is possible to accurately measure.  Item O is a brass piece that is pressed into the bottom of Item P, which is an insulating material and has a very fine pitch thread on the bottom to match the body tube and a coarser thread onthe top for the mounting nut.  There are a fair number of different counterbore diameters, in addition to the external diameter changes.  I am reluctant to try and separate O and P. The basic idea is that the antenna mast is a close fit to the coupler, and the center electrical contact connects to the coupler via the center screw. 

Paul

[autoluke]

Paul
Just learned from Charlie Babcock that the thinner one was used on the '41 models, although the larger one has often been used as a substitute for that year.  As you had concluded, the larger diameter was used throughout the '47 to '49 period.  Solves the mystery regarding the date stamped on the tubes.

[Paul Phillips]

Phil
I have completed the dimension takeoffs for the body and coupler.  Since these are pressed together, there will be a few dimensions you would need to interpolate to replicate the parts.  Please refer to the pictures of the subassembly.  If something doesn't make sense, please ask.  All dimensions are inches.

Body - hard plastic material, specific material unknown.  Must function as a structural part as well as electrically insulate.
2.378 total length
0.914 length of turned-down section inserted in tube
1.009 diameter above tube
0.991 major diameter of threads for cap nut
0.500 length of threads for cap nut
0.903 major diameter for tube thread
0.869 minor diameter for tube thread / diameter of turned down body below threads
0.435 length of turned down section below thread
0.400 length of threads for tube
0.079 length of turned down section above threads
0.614 diameter of top counterbore
1.118 depth of top counterbore
0.675 diameter of counterbore for coupler
0.300 diameter of clearance hole for antenna connector

Coupler - brass, made of a tube and a bushing pressed together
2.468 length projected below body
2.617 length from bottom tip to bushing (bushing sits sub-flush in lower body
0.390 tube OD
0.306 tube ID
0.675 estimated OD of bushing - press fits into body lower counterbore

You would need to decide how deep the lower counterbore should be and adjust the coupler bushing & tube to match.  I would estimate this to be no more than 0.75"
There is a clearance hole between upper and lower counterbores in body to allow the antenna mast to pass thru.  It is likely the tube ID or slightly larger (0.306")

There is also a 0.187 dia. weep hole drilled at bottom of the upper counterbore, complete with an angle relief to assure drainage.

Good luck!

Paul

[Paul Phillips]

More pictures

[Jeff Maltby 4194]

Paul, are these your antennas on the bench and if so, I met David via his reproduction btm cap auction on ebay.

[Jeff Maltby 4194]

Quote
Just learned from Charlie Babcock that the thinner one was used on the '41 models, although the larger one has often been used as a substitute for that year.  As you had concluded, the larger diameter was used throughout the '47 to '49 period.  Solves the mystery regarding the date stamped on the tubes.
[/quote]

The large diameter tube was used into the 50's.

[Paul Phillips]

Jeff
The pix in my post are of my 41 antenna parts, but the photo of the two on the bench were not mine. I do have some later (large body diameter) parts accumulated, as I will be rebuilding my 49's antenna after the 41 project is complete.  Just to confuse things further, I have devised a way to use the body mount bits from a 47-49 series rear antenna to convert my 41 fender antenna to a cowl mount.  Takes some modification to the metal bracket, but angles will work.

Paul

[autoluke]

Paul

Many thanks for the information.   It is now scheduled as a winter project.

Phil