MTFCA Forum

I think I understand all the holes and the horn bracket cutout, but I wonder if anybody can explain the circled part.

If I read the drawing correctly, section BB is part of the dash that was to be cut away to provide clearance for the rear cover of a 1915/16 era magneto horn. The cut was shown in two parts, first as a straight on view, then second as a cross sectional view (BB).

At least that is how I am interpreting that part of the drawing. Others may know more than I.

Respectfully Submitted,

Trent Boggess

Trent is correct. I have the factory drawings for the 1917 firewall which is basically the same as the 1915-16 firewall and I have an original 1917 firewall my the car as well as a spare original firewall.

Section "BB" is the relief along the bottom edge of the firewall for the rear housing of the magneto horn which is to the right of what you circled.

What you circled is the cross-section of "BB" and illustrates the angle of the bottom edge for the horn relief.

Thanks, gentlemen. I may install a pathetic mag horn, but I'll keep my Stewart mechanical.

Trent nailed it, detail of section BB.
Modern drafting standards would not have placed the section BB (circled in red) on the part being drawn, it would be off to the side to avoid the confusion this drawing creates.

I have a couple of questions, is the drawing for right or left hand drive? Are we lookin from the inside out or the outside in, either way leads to more questions. In the day a horn was optional, a magneto horn was available as was a bulb horn and hand operated mechanical ie Klaxton. The hand operated Klaxton mounted on the door with two screws and the Bulb style mounted on the fire wall/dash beside the steering column bracket. On the early 1915 firewall shield there was a recess for the bulb horn air tube to fit through and on the later models the recess was eliminated. The Magneto horn used one of the steering column brackets with an additional 21/64 hole drilled for the second mounting bolt. With the magneto horn mounted in this way the only interference would be the shield, if it was slightly cut away there would be no additional interference from the wood firewall.

Fossil evidence on Canadian firewalls I have seen differs from that shown in the drawings. The relief shown is a simple chamfer, with rounded ends, indicating it was to be formed on a spindle. The reliefs I have seen on Canadian firewalls have a rounded section rather than a flat section to the cut. These would have been created by a ball shaped cutter rather than a simple V cutter used for chamfers. Is this a case of follow the drawing, but use what you have to do it?

Allan from down under.