***1915-1916 Firewall Question***

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VowellArt
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***1915-1916 Firewall Question***

Post by VowellArt » Wed Jun 22, 2022 7:34 am

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.


1915-1916Firewall2.jpg

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.
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George Mills
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Re: ***1915-1916 Firewall Question***

Post by George Mills » Wed Jun 22, 2022 10:28 am

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)

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Mark Nunn
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Re: ***1915-1916 Firewall Question***

Post by Mark Nunn » Wed Jun 22, 2022 1:15 pm

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".

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VowellArt
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Re: ***1915-1916 Firewall Question***

Post by VowellArt » Wed Jun 22, 2022 5:21 pm

Mark, I drew this full size...but the forum won't allow anything over 2.81mb at 150 dpi. My original drawing is 300 dpi at 9.85mb. If you want I can send it to you via your email, but just can't here on the forum....I can also post it on FB, if you think that would be easier to get too.

Steve Jelf has already weighed in on the thickness issue and says it can be 7/8's because it won't fit the Hood Former. So, if the side thickness can't be 7/8's, because the width tolerance (to fit the Hood Former) is .667 to .697....which indicates that ether the Core isn't 5/8's (.625) but somewhere around 1/2" (.500) and the Veneers aren't 1/8" (.125) but somewhere around 3/32's (.094), which gives us .688 which would be within the thickness tolerance limits. But that makes the fraction as 86/125's, since this is the finished thickness, it probably doesn't matter overmuch that the tightest fraction I've seen in this drawing is in 64's. Your guess is as good as mine, I don't have a clue as to what it really was, without the other drawings of the firewall, because to my mind there would've been one other drawing...the one that specifies the thickness and finishing of both the Core boards and the Veneers.
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Allan
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Re: ***1915-1916 Firewall Question***

Post by Allan » Wed Jun 22, 2022 8:08 pm

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

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VowellArt
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Re: ***1915-1916 Firewall Question***

Post by VowellArt » Thu Jun 23, 2022 7:44 am

Allan, both Steve and I came to the same conclusion about the thickness of the core vs the veneers. But the Forum won't allow me to post this drawing here due to it's size (13.98 mb at full size). The other thing I realized was that this drawing is not a construction drawing....it is a machine set up drawing, which is why there are no radii start points nor tolerances given....it is merely to set up a multi-spindle drilling machine, which measures in fractions of an inch, not decimals.

I've offered him the full size drawing, because I think he's probably the only one who will try to make it, but if anybody else wants a copy, I just need your email address or maybe I can post it on Face Book....it took some pretty large files I've posted before, but I'm not sure it'll take this one...but I could try.
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Ray Syverson
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Re: ***1915-1916 Firewall Question***

Post by Ray Syverson » Thu Jun 23, 2022 1:53 pm

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).

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VowellArt
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Re: ***1915-1916 Firewall Question***

Post by VowellArt » Fri Jun 24, 2022 8:36 pm

I was able to post the full size drawing on Face Book and I posted it the groups I usually post to too. Long Beach, Model T Ford Club of FB, Southern Nevada, Southern Utah, Model T Enthusiast, and the MTFCI Face Book group.

I've also found the T factory number and the vendor part number too. And I also found the starting points of those radii dimension lines. But I realized from looking at this drawing that it is a Machine Setup Drawing, not a construction plan. The type of wood used in making the firewall core was whatever incoming packing crates they had on hand (and they had tons of it, cardboard boxes weren't used commercially yet), which isn't really too hard to believe really, my neighbor had floorboards in his touring car that had the Dietz logo on them (and it wasn't a repro either). Ford did use every scrap of wood that came into any of his plants to help build the Model T, mainly because it helped keep the cost down of their manufacture, even though he sold the cars basically at cost and made the profit off replacement parts, still, if you can keep costs down in the first place, your profit margin rises (albeit not much), but over the long term, it a becomes significant company savings. And Henry never looked at short term returns, he was always thinking long term....which is why he thought the Model T was the only car anybody would ever need....thank God for Edsel, who thought outside the box rather than inside it like his father did!
:?
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