Once the tank was apart, I sat the halves flat on the work bench, then elevated the narrow end 1". I then used a 1 1/2" thick wood block with a silver metal marking pencil laid flat on top, to mark a true line all the way around the tank half. I used a 4 1/2" angle grinder fitted with a cut-off wheel to carefully cut the line out;  I then used my angle die grinder with a rolock disc to clean up the cut and true the edge to fit flat on my work bench.

Picture shows one side cut and the other marked....................   

I thought the tanks had a right and a left profile? If there the same mold I have a friend that was going that o make me some molds to press some metal tanks. I put it off because there was supposedly someone that was building molds already. Let me know if you get a metal tank going as I would like one.

I don't know about all the Simplex tanks over the years, but the one I'm working on is the same stamping for both halves. It always appeared that way to me just looking at a tank, and made economical sense; look at the picture of the halves nested.................   

A better picture of the baffle; edge of hole to edge of plate is 1/4" on the forward 1/2" hole and 1/2" on the 4th.  and 3/4", edge to hole on the 1/8" holes. Plate is 1/8" or so larger than the inside of tank because of the flange. Tank halves and baffle made of terna plate (lead coated steel).

Grinding away the original flange weld to separate the halves...........................

Not having any luck finding a '37 type gas tank for my Simplex board track racer build, I decide to modify a late tank to approximate the '37 configuration. I had a solid dual fill tank that needed cleaning inside but was solid metal, so the project began. 

I am interested in your throttle control experiments. I am working on the same type throttle. I am using bicycle derailleur cable, which is smaller and more flexible than brake cable. My throttle handle will move in and out to pull the cable; the older Simplex used this type control. How did you make the spiral slot in your second experiment? A CNC mill sounds like the best way but I don't have access to one.

Quote from: WillH on May 01, 2015, 06:59:19 AM

Gravely "L" T head engine

What kind of power do they put out?  I don't like the gas tank, as that is one of the best features of a simplex.  I bet you could enlarge the frame about 25% and fit the engine in properly.

I agree with you about the original Simplex tank; it is a beauty; hard to improve on.

A little more on the Gravely "L" engine; 49 cubic inches, 800 cc's and a whopping 7.6 hp. Guessing that it weighed 70 to 80 lbs.

Is anyone running a billet flywheel on a GX or GC Honda? There seems to be several choices, some with fins, some without and some with ignition advanced over stock. Any experience with any of these? Thanks