Gas Tank Work

Tank bottom cut out.
Tank mounts laid out, old crappy cap bung visible. Cut lines laid out.
Curved tank bottom, it sucks.

Gas Tank Fill Spout

Here is the finished product. Looks like one tube, just as intended. Kris knocked down the welded on the lathe and left it .040" or so proud of the final surface as I planned on hand finishing it. Trying to grind a round tube, any smaller than 6" in diameter is a nightmare. It is very hard to not make the tube 'notchy' from grinder passes. So I chucked it up in the lathe turned it at 190 rpm's and then used a 2" 120 grit to grind the weld flat to the tube. This trick helped me to get a perfectly round tube, that it completely seamless and no one can tell by sight or feel that it is 2 pieces welded together.
Another view, pre-clean up.
Welded it up over lunch. Tacked it around the diameter by skipping around to prevent over heating the weld seam. Then stitch it together between the tacks. That is why you will see a variation in the heat line, thickness and style of weld.
A perfect fit, it makes the welding a breeze. I don't have to worry about the 2 parts slipping out of alignment as I work the bead around the diameter.
I bought the cap and matching steel bung from The Chassis Shop. A race car chassis parts company based in Silver Lake, MI. They are either partners with or own Pro-Werks as well, the company the cap. Both for aesthetic reasons and function, I wanted the gas cap to be 2-2.5" overall height off the top of the gas tank. So I need a piece of pipe to weld to it that is the same diameter and will look seamless like one piece of tube. I was lucky to find this chunk of old steam or water pipe that was just .100" over the diameter of the pre-made steel bung. Tom 'Tweaky' Peek turned it down for me when he still worked at BAKER. I have had it for 2 years. Kris added a small counterbore to it, as the bung has a .060" tall lip on it. This allowed the 2 pieces to align perfectly to each other before I welded them up.

Tank Mount Models

A section view right through the middle of the mounts to give a better idea of how it all works.
Here are the computer models that I created to make sure everything laid out just right. I use Solidworks for almost all of my designs. It may seem like overkill, but this whole design took me under an hour to calculate and model everything. Make assembly a breeze as a result.

Gas Tank Pockets 2

I forgot to clean off the threaded bungs with lacquer thinner before I machined them and I pretty sure that is why they turned blue. The bluing was only surface deep and I did not put that much heat into the weld. They had oil on them from anti corrosion coating from the mill, as well as an extra concentrated cooling solution in the lathe. The welds will not be visible once I weld the mounts in the tank, all I care about is that they don't break and/or leak.
Double checked that they fit good, and got the welder fired up.

For both cost and ease of machining reasons, I made the gas tank mount out of 2 pieces. It didn't make sense to waste all of that material for machining. I added the .020" deep counterbore to ensure the threaded boss would be center in the threaded hole for alignment ease during assembly. Allows the 5/16-18 bolt to have over .700" of full thread engagement. Plenty for strength and a decent safety factor.

Gas Tank Mount Pockets

Curvature added to the end to match ripe up to the profile of 13 gage tank tunnel that Fab Kevin hooked me up with. It will make sense when it is all mocked up and ready to be welded together.
Inside view, added R0.063 fillets to the interior corners for added strength. These will be welded into the bottom of the gas tank and sharp interior corners are a huge no no as it creates huge stress risers. Added a R0.125 to the top edge for a smooth look when in the gas tanks. Round corners are also less like to pop paint off. Same steel here, 1018, low carbon mild steel.
Gas tank mount pockets. Design these from scratch to match up with the tabs and grommets and tank so that the bottom of the gas tank will be even with the bottom of the top tube on the frame. Gives a smooth line of the frame and bodywork in the end. As a result of this i had to machine some pretty deep pockets. The thru hole and .020" deep pocket are for a threaded bung that i will weld on later. Decided to make them 2 part rather than dropping some coin on 2.5" thick steel just to machine it mostly away.

Gas Tank Mount Tabs

Tank mount tabs done. The large hole is too accomodate a rubber grommett for vibrations dampening. 2 different length tabs becuase the tank is wider at the front and the longer tabs will provided more stability and allow less tank resonance and vibration at speed. Reducing the chance of failure and getting a lap full of gasoline sitting right over a smoking hot air cooled engine.
Profile complete and the width is set. The 'fishmouthed' end of the tab will wrap the top tube of the bike. Commonly the tab is just flat stock, butt welded to the top top tube. Rigid choppers, like I am building, are vibration nightmares which like to break the welds on gas tanks. I wanted to get a wrap too the top tube that will also allow me to spread my weld over a larger area, adding a lot of strength and sending the vibration forces into the thicker radiused corner.
Op 1 complete, flip them over and finish them off. You can see below that i don't have much meat left in the vise to hold onto. I would have like a thicker piece of steel such that i could machine the profile to height, then flip it over and run a face mill to finish the overall width of the tab. Bigger pieces of steel cost more money, so i got a piece the is right to size. Just had to make sure I located it accurately so there is no mismatch when machining the same profile from 2 different sides.

Start to finish gas tank mount tab machining. Off the shelf 1018, low carbon mild steel stock. Cut to length, design set and programs loaded. Let's make some chips.

Front Axle

Entire front axle assembly in place. I need to take approx .050" off the front brake bracket to push the caliper towards the lower leg and this make it centered over the brake rotor. Check this off the list. I now have a full roller, with the spacing and brakes set. Gas tank next.
Spacer in place over newly machined axle, nut torqued down.
Here is how the nut looks on the lower leg. I am happy that it looks like it belongs. The flange of the nut matches up nicely with the boss landing.
So here is the axle I machined. Well actually Kris, the BAKER Machinist did this one. I can't run the CNC lathe like he can and I just wanted to get this part done, rather than taking the time and wasting the material (think money) while trying to learn more. Axle is made from: 4140 alloy steel, 28 rockwell C, pre-heat treated. Yields the strength and stifness that I need. This axle is different than a stock softail as my design has nuts on both ends. The stock H-D softail axle has a knob on side with a hole to place a drill through while torquing the front axle. It is a design befitting a lawnmower at Wal-Mart, not a custom bike.