Iron Triangle Progress

Bike so far

complete bike 1

Gas tank is mounted on three points, here are the front two mounts

tank mounts

The exhaust pipes are 1 3/4″ OD, the common header pipe size. The problem with that is the actual exhaust port size on twin cam heads is 1 5/8″. Usually there is an abrupt step where the heads meets the flange. I machined the flanges with the inside tapered to perfectly blend the two sizes. Also, they have a flat, perfectly matching taper on the outside of the flange, so there is no way the gasket material can squeeze into the exhaust flow. This happens often with aftermarket exhausts! These are machined from solid stainless steel on my manual lathe.

exhaust flanges 1

exhaust flanges 2

Here is the underside of the gas tank, with two giant mounts welded in. They are 1.5″ OD flange, milled down where it goes through the tank. This distributes the load over a larger area of the floor of the tank (which is made from 1/8 chrome-moly flat stock).

underside of tank


9 responses to “Iron Triangle Progress

  • Ty

    I agree. Awesome!

  • Ron

    How much does that tank weigh, I’m curious given the material type? Nice. I like how you have the tank sitting further down toward the rider on the backbone, i’m assuming you did this to lower the center of gravity and improve performance.

  • jeff

    Lock, is there any chance you can explain the tank fabbing and forming process, totally understand if your too busy.

    • lockbaker

      tank weight is about 1 and a half sportster tanks Id say. the position is simply because it looks fucked up, but I suppose a lower center of gravity is a bonus.
      The sheetmetal forming process is a hard one to explain, because every tank is so different. I find that really good paper template making for each panel is a huge help, especially if you have a “buck” to take them off of. I tend to make mine out of wood, but Ive seen them made out of foam as well. As for the actual forming, my tools are a sandbag and hammers, several dollies, a plannishing hammer, english wheel, slip roll, and a shrinker. They are all small scale tools, no giant yoder power hammers here (yet).

  • dWrenched George

    Lovin the stance on this beast ! The apes-gas tank area is simply bitchin !

  • Trusty

    Hey Lock!

    Iron Triangle is absolutely killer!

    Came across this and thought you’d dig it man:

    One of my favorite parts in this is when they talk about using burnt bones to harden steel šŸ˜‰


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