How to fit a Road and Race long jelly mould tank to a 1966 narrowcase frame
Phil has two different types of jelly mould tanks:
Fuel tank, long Elite -
jelly mould
style, fibreglass, with cap
Fuel tank, short 125/175/250 F3 style, fibreglass, includes tankcap
I bought the long Elite tank as I really liked the look of it, I found the F3 style to be too short for my liking. The long Elite tank works well with the short seat that I am using. The tank as shipped had some small problems. The most visible one was the front lugs were not straight or vertical. I was concerned about this but it really wasn't a big problem, as you will read later on. I did have to spend some time with milled glass and resin cleaning up some rough areas of the tank, especially around the fuel outlets but this was really minor. Still of real concern is the gas cap, as can be seen from the picture, the cap is flush and really hard to get a hold of. As you can't really hold it, the cap is difficult to start properly and very easy to cross thread. I have managed to cross thread it a few times already.
I took the tank to work and had the NDI guys look at it. We have a number of NC TTU (Thru Transmission Ultrasonic) machines for big panels but the oddly shaped, small stuff must be done by hand. The NDI guys like doing different, smaller stuff as it increases their knowledge base on how different shapes and materials image. Very simply put, transmit ultrasonic sound through a material and time the returning wave forms. Typically good composites are solid, bad composites have voids. Solid stuff transmits sound well (faster), voids transmit sound poorly (slower). The trace on the hand held scope shows a wavy line with major peaks for the reflections from outer and inner surfaces. Sometimes these peaks are not that pronounced because of surface defects, poor coupling or bad probe technique. The wave form between the peaks defines the "stuff" between the inner and outer skins. This is where experience comes in. Oops, I really digressed... They found one bubble about an inch in dia, left front and some minor bubbles on the top and elsewhere. The good news was that although the front bubble looked big, it was thin (.020") right in the middle of the plies and well away from the the attach lugs. The other bubbles were of no concern.
Since the tank is fiberglass, I had to find a way to mount the tank without any preload and no fibreglass to metal contact. My GT and SCR both had cracked metal tank lugs. I bet that this is a very common problem for single metal tanks.
I decided that a good way to mount the tank to the steering head would be with big rubber grommets and through bolts. Surfing the net found Mr. G's Fasteners. They specialize in hard to get stuff for restoring cars and have a huge assortment of rubber stuff including grommets. The front tank lugs are .250" thick, so I thought that would be a good place to start. I found a bunch of grommets that would fit a .250" thick wall. My next criteria was that the grommet would have to fit in a hole of no bigger than around .850". I figured that removing more than .850" would weaken the tank lugs. I found a grommet from the .250" bunch that had a .8125" groove dia. and a bore dia. of .50" -FA 2736- I liked the .50" bore dia as it was bigger than the 8 mm bolts used to mount the tank. Using the 8 mm tank mount bolt inside a bore of .50" left about .192" to fill. I found some really soft surgical tubing that fit perfectly from McMaster-Carr.
I needed to drill .250" dia holes into the tank lugs for the pilot of my hole saw. I roughly marked out where to drill the pilots and fit the tank onto the bike. First thing was to level the bike, I used the aft upper frame loop as a horizontal plane. I then leveled the tank laterally, there is a flat area just forward of the gas cap. I locked the tank into place and got ready to drill the pilots into the tank lugs. This was really nerve wracking as can be seen from the front view of the tank, the attach lugs are not that straight and or vertical. As it happened the shape of the attach lugs really did not cause any real problems and you can't really see it on the bike in any case.
I burned some incense and sacrificed an old clutch plate and drilled the holes. I then refitted the tank and it was tilted over to the right, grrrr. I filled the left hole with resin and milled glass and tried again. Second time lucky. I then hole sawed the front tank lugs out to .800.
These pictures actually shows the same lug, I think the camera was not parallel to the lug in one picture. The grommet was just installed so it looks out of round, it takes a while to settle in. As well I drilled out the frame mounts and heli coiled them for an 8 mm fastener. I also had to grind down the pads on the steering head as they were too wide for the tank lugs with the grommets. As the mounting pads on the steering head were small and rough looking, I made some thin washers with a id of 8 mm and an od of 1.25" and polished them. This is what the grommet would ride on.
I sanded the holes in the tank lugs to open them up a bit and then sealed the edges of the holes with resin. The lugs and holes were polished with 600 grit wet/dry. I made the lugs and holes as smooth as possible so that the grommet would easily fit and be able to float a bit. Inserting the grommets was still difficult, I have to warm up the grommets and then use water as a lube.
Steering head, big shiny washer, grommet, surgical tubing, washer and then button head 8x25 mm. When everything is fitted and tightened, the tank can be moved in any direction with little effort and definitely no preload!
The back end was much easier. I mounted a stainless ring a little forward of the aft end of the tank so that the O ring would ride the tank. I had to open the stainless ring to get the O ring into the ring and then bent it back. The tank has a 6 mm female insert molded into the aft face. I found a 6x15 mm fairing screw from Indigo and polished off the threads where they contact the O ring. The O ring is 2.5" in dia and .200" thick and is very strong. I pull tested the O ring by attaching a cable to the ceiling and lifting the bike (no engine) about an inch and left it. After a week of bouncing the frame around, I gave up.
I needed some closed cell, fuel proof rubber for underneath the tank, where it rests on the frame tube. I tried some of that foam that is used to insulate hot water piping but didn't like it. I remembered seeing some foam to make gaskets for APU ducts at work and I did some dumpster diving and found some trashed silicone closed cell foam which will be perfect.
I am not going to paint
the fibreglass
this year. I want to
get
the bike on the road and shake it down first. I will be painting
the tank dark blue with silver flames. The seat, front fender and
rear fender will be dark blue as well.
Tank March 31/2005 !
