While we’re on dimensions, I have a question about the effect of width on ‘length’.
The D-type had no jockey wheel or slotted bracket to tension the water pump belt. I instead the pump used a two-part vee belt pulley. The main casting bolted to the pump spindle had only a back flange. The central boss was threaded to accept the separate frontvee flange that screwed on and secured with a grub screw. The closer the flanges the bigger the effective diameter of the vee track and therefore the tighter the belt became.
My D has custom conventional pulleys and the belt is adjusted by moving the dynamo. However, with a tilted engine there is little room to move the dynamo in/out. I have a belt in place but it’s quite narrow and looks wrong with the modern notched circumference. Although narrow (3/8/"?) it sits clear of the base but I want a wider more old-school belt.
Clearly, the wider belt will sit higher in the vee and need to be longer. I could eventually calculate the circumference of the three larger diameter tracks on the existing deep pulley grooves but is there some kind of table or formula that can used to predict how much longer belts have to be for different belt widths on the same pulleys and shaft distances?