Cable brake questions

[Master Hack]

The reason is not for strength. It's a replica of a 1932 Ford frame, which has a very specific appearance. In other words, it's built like that for looks.

That's cool and there have been other replicas here and all have been works of art. The point was the weight. No way a little mechanical brake is gunna be satisfactory. That 6" brake is for a sub 200# cart (SWAG). So I'm guessing you will be adding a body at some point? More weight...
Save yourself some grief and ditch the mechanical brakes for hydraulic. BTW a drum brake will probably be worse.
The above is just the opinion of a grumpy old man, there may or may not any basis in fact.

 

[Hellion]

That 6" brake is for a sub 200# cart

That's a good point and maybe two brakes would be better. I was reading past DIYGK posts on the topic; the mechanical disc brake seems to have major fans and major detractors. Lots of people use "locking up the axle" as the measure of effectiveness and some (most?) of the guys who said that were in the neighborhood of 150 lbs wet.

I have not thought about disc rotor size in conjunction with karts, probably because these you can't go too big before you're dragging it the disc on the ground. Also, some of these vendor supplied discs often look like they are galvanized or zinc plated (too slick) which does not bode well for effectiveness.

 

[Master Hack]

have not thought about disc rotor size in conjunction with karts, probably because these you can't go too big before you're dragging it on the ground

Size matters! The stuff i've salvaged off these crotch rockets are huge. Slightly differerent applicatioin, you say? Why yes it is. These 3 huge rotors by comparison are 12 inch.
(12 inch is a guestimate from another room.) thats for 500 lbs bike.
Weight is a big factor when compared to brake surface. There ya have the total of my "linear friction vehicle decellerator" engineering knowlegde.
just seems purdy basic to me.
if plan A fails, plan B needs to be bigger and or better.