MTFCA Forum

Ok, got a question on this drawing....you'll note that the radius 16 7/64" has no dimension from the datum plain to the distance from the center-line...also there is no dimension for the start point of 5 51/64" Radius, now if you continue that line it does intersect with the dimension line for the 11 63/64"R line. But without a start point, you're never likely to find where the radius changes....this is a compound radius. Now there is a start point up from the distance dimension over from the center-line for the, but where the hell it is located from that point I couldn't tell you.

The other thing different is that I didn't include that 3/4" DRILL 5/8" DEEP bore that is on the front (engine side) on the firewall drawing....nobody could tell me what it was for nor ever seen it on any of the 1915 or 1916 cars, so I omitted it....if you happen to know what it IS for, let me know and I'll add it with a notation as to its specific purpose and what year (if any) it appears.


I've left a space open for the 16 7/64" up from the datum line to the start point of the radius...if anybody knows what this is, please let me know.
Also, down in the left corner is a circle that is divided into 3rds....the middle would be the Factory Part Number, the space above that probably the originating engineer, the space below the FPN, I think is another number....it isn't the date, the date is in the upper right hand corner just above the "Revisions" change block. The 3 initials at the bottom on the right side are most likely the drawing checkers. So, does anybody know what the Factory Part Number for this drawing is? If anybody has a clear picture of that ball at the bottom left I'd like to see it.

Now the notation at the bottom that tells you what this drawing is, specifies "#3 PLY WOOD"...this indicates how many ply's this drawing represents...in other words it is the finish machine drawing, the 3 ply's are 1/8" VENEER, 5/8" CORE and another 1/8" VENEER. Making the total thickness dimension in the side view of 7/8". Also there probably is some drawing somewhere that has the exact thickness of the CORE and how many slats it is made up of, but the grain is Vertical, whereas both of the Veneers are horizontal....the other clue that this is the finish machining drawing is the notation of the 3/32" R and 5/32" R at the top of the side view, these most likely accommodate the bends in the Hood Former....there would be no reason to make those radii unless it was on the finished product.

The other problem is, I drew this drawing Full Size, seemed only logical, given that it is the finish machine drawing...I had to shrink it quite a bit to get it to fit the Forum's size parameter requirements.

Martyn,

Can't help you with the geometry and where are the anchor points, but I have always been fairly convinced that FORD ran from process cards and not from actual blueprints. (I apparently hold that view as a Lone Ranger...and that's OK). IF FORD ran from process cards...and everyone else did in the era more likely for security reasons (Viz...steps 13-21 just might be on their own card)...then the cards were apparently lost in the fire as they apparently don't exist on any microfilm to be accessed. My guess is that the first guy who came along and scratched his head invented the start point datums...and wrote it in the margin of a PROCESS CARD for others to follow in the future without an Engineering Change Request.

However, coming at it from the opposite direction, I have found that sometimes the Record of Change Cards for a part number are a bit detailed on the 'whys' changes were undertaken...and sometimes they are fairly silent. Maybe you could pick up sponsors to help pay the fees to have the cards copied for you? (For those with engineering department background, these Record of Change Cards were the same as what our generation called Engineering Change Orders)

I can't read the dimensions on your drawing at that resolution. I think it would be logical to find the blank dimension by subtracting 16 7/64" from the height shown on the left. That height looks like 20 XX/64".

Steve is correct about the thickness. It should finish just shy of 3/4". When fitting the hood former these days, it is usual to have to reduce the thickness of 3/4" plywood just a tad at the rear to allow the short return on the metal to fit over the ply.
In my experience, the two veneers either side of the core are not 1/8" thick. Together, they would be close 1/8", so the core could be close to your 5/8".

I don't know if this affects your excellent drawing.

Allan from down under

I looked closely at the 1916 firewall I have, and using a micrometer measured the outer plys and core. The core measured .55 in. and the outer plys were both .077. That adds up to .704 inches, which of course would be too thick, so I assume the parts I measured are slightly swelled.However, this gives you an idea of the approximate original thicknesses. Ideally the firewall thickness should be 11/16 in. or .687. I think the nicest material to make them with these days is the "baltic birch" plywood. Not sure about now, but it used to be available in 60x60 in. sheets, and the "3/4" size actually was closer to .700,and I found some at .690 thick.( I brought my micrometer along when picking the sheets).