Need Model T transmission "Top-Hat" bearing measurments

[accuratemodelmaker]

Hey, can anyone in the group share the known measurements of the Model T transmission early Brake Drum "Top-Hat" bearing? I see some of them given by Benson Archives parts listing pages, but would prefer to have actual measurements, even if a little worn.

Thanks,

Jim Key
Accurate Models

[RajoRacer]

I have a NOS one - be tomorrow before I get back out to the shop.

[speedytinc]

.111, .111. & .112. all used measured in an area with no wear.

[accuratemodelmaker]

Hmm, that's interesting, given that the call-outs for the flange have been 1 & 39/64" (1.609375"). I took and subtracted the bushing (1.50?) from the flange and got .109375" as a remainder. Reading other threads, I remembered .110", so your measurement of .111", .111", .112" seem to bear out those previous postings. This is important because looking over the Benson archive parts prints, The early Brake Drum shaft is shown to be a total of 4.686" to 4.689". The later shaft is 4.670" to 4.676" - .010" to .019" of an inch shorter. I suspect it has a lot to do with replacing the Top Hat bearing with the 3 thrust washers.

Still need depth (back of flange face to opposite edge (1.50"?)

OD of bushing (1.185"?) ID of bushing (1.002 to 1.004"?)

OD of flange (2.375"?)

Thanks in advance for all assistance. New plans for preview soon, as I've completed quite a bit, as well as 3D.

Jim Key
Accurate Models

[RajoRacer]

Here's what I came up with my digital caliper - this bushing shows no signs of installation nor use.

flange width = 2.381
flange thickness = .109
inside flange face to bushing end = 1.420
body O.D = 1.190
body I.D. = .995

[accuratemodelmaker]

Thank you, Steve. Much appreciated.

Jim Key
Accurate Models

[speedytinc]

What is the date of the brake drum shaft dimension change?

[accuratemodelmaker]

I believe from looking at the drawings, the change in the brake shaft dimension is when the top hat bushing (bearing) is removed (revised). However the first time I actually see the new dimensions is on the 1916-1921 T-750 assembly drawing listing the shaft at 4.670" to 4.676". The top revision date on the print is Dec. 2, 1916, and introduces the 30 degree angled edge along the rivet flange.

The early 1908-1916/17 T-710 (shaft only) print describes the shaft as from 4.686" to 4.689" - without 30 degree angled flange edge.

The 1922-1925 T- 750 assembly print adheres to the same shaft dimensions as the 1916-1921 T-750 assembly print. This one serves as the "R" or replacement parts print - last dated at September 30, 1925.

Jim Key
Accurate Models

[speedytinc]

Then the shaft change applies to the early style drum that requires the distance plate & 26 clutch disks.
That makes sense & has nothing to do with the hat to 3 washer change done in early '20.
What is perplexing is the lack of documented change to the clutch hub, done in early '20, coinciding with the thrust washer change.

[accuratemodelmaker]

At some point along the way of doing these parts schematics (drawings) I want to show the relationship differences between the early drum/shaft/distance plate/clutch drum, vs. the later drum/shaft/washers/clutch drum. This has been a hot topic for many on this forum when trying to rebuild their transmission with different era parts.

Studying the Benson Archives prints has been fun and very revealing. I highly recommend contacting Jim Orr at Benson if you wish to obtain your own collection of prints for private restoration works. Know that they require purchases to be kept private. My goal will be reconstruction and not to simply broadcast these vintage prints.

Jim Key
Accurate Models

[speedytinc]

The answer is in the later version of the clutch hub. It is .015" different to fit the thicker 3 washers.

[speedytinc]

Jim Key:
We know how to identify the early brake drum(pre 16) We know that a distance plate & 26 disks are required. We know what the earliest clutch hub looks like. We know what the later drums look like & 25 disks. We know when the top hat bushing changed to 3 thrust washers. We know how to identify the earliest & latest clutch hubs.

We dont know how to identify the in-between hubs without measuring the set screw location. (working on it)
We dont know original, unworn height/thickness of the small disks & thusly the height of a 25 disk clutch pack with the dished disks.
(working on it)
I am also not sure of the height of the 3 finger clutch disk, if there was a height/thickness difference in different years.
(Preliminary measuring of used parts indicates a possible difference)

These questions I hope you can answer from your Benson research.