MTFCA Forum

As I endeavor to continue my blueprinting project of the Model T Transmission, I have had a lot of input for identifying early, mid, and late version parts.

One of the major fact finding missions seems to be coming up with verifiable plan info that shows the parts relationship of the early thrust face clearances vs. the later thrust face clearances. The illustration shown here is derived from Benson archive Ford parts drawings, as well as actual measurements, compared also to service manual statements, and later public domain drawings. I can report that early T-725 "B" 6 hole Clutch drum exist in blueprint form to be compared to Brake Drum shaft, Drums, and Center gear shaft. Using all these references I assembled (in 3D) all the parts and examined them in section for fit.

Once Jim Orr at Benson Archives and I choose the later T-725 B and A Clutch Drum drawings, I can then compare and contrast the early Top-Hat versions against the 3 washers versions and examine set screw differences, as well as clearances and gaps. For now, here is the first investigation.

Will report more as the weeks reveal what else is being investigated.


Jim Key
Accurate Models

Here is an illustration (derived from Ford parts drawings) of why the early clutch drum distance plate was so important.

You can see how there is a gap (blue) of @ .057" to .058" between the front face of the lug and the inner drum wall. Enough room to completely jam up a .040" to .042" thick loose clutch disk that would work its way off the back of the clutch drum (red - .531" gap).

That is why the small disk (13 in early version) were put on 1st, after the distance plate, alternating with the large disk (13 also in early version), which goes on last under the push ring to again trap these disks into not coming off the clutch drum during operation.


Jim Key
Accurate Models

Here is a perhaps simpler presentation of the early Brake Drum to Clutch Drum relationship.


As time goes on, I hope to show more about the later Brake drum to Clutch drum parings.

Jim Key
Accurate Models