Gentlemen,
One way of cutting venturi tube O-Rings from silicone tubing: Use a piece of appropriate size music wire & run it through your ~ 1" piece of silicone tubing. This music wire will now become your mandrel with which to hold the tubing with.
Place this assembly into the freezer until frozen. Remove from freezer and chuck music wire into the lathe. Now, with a sharp Exacto mounted to your tool post holder, you can now
feed the blade onto the silicone. If you lock the tool post, then you can precisely cut off ( in thousandths) whatever thickness of tubing you like. Cut off different thickness's & try to see what works best for you.
I'm now trying O-Rings (made for darts) bought at any shop that sells darts. A bit thicker than the Cox originals but worth trying I think, & can be locally bought cheap.
As far a sealing the backplate, since the tiniest piece of silicone glue coming adrift can totally mess up your tank, I don't do that. I have seen some metal backplates warp a tiny bit & just won't seal no matter how tight your screws are. Short of replacing parts my "good enough" solution is to dab (RTV) silicone glue on the entire outside (well cleaned) joint periphery & let dry.
(while I'm at it I do the tank to crankcase joint as well). Another "almost good enough" solution is to wrap the (well cleaned) joint on the outside with Scotch Decorate & repair tape (CLEAR blends with all colors). This is a wonderful product that really sticks to many surfaces really well, plus can be done right on the field if need be.
These are just some suggestions that have worked for me & are proven on the mouse racing circle to have worked well enough. Experience has proven that the black nylon backplates tend to leak less (at the backplate tank joint) than do the metal ones. (Although I have seen both types
leak!)
I hope the above has been some help. Cheers,
Paul Gibeault (
aka "Mr. Mouse")
A good venturi gasket is important. I have tried making these at times when I didn't have a real one. Never could slice off a uniform and appropriately sized piece. If someone has a trick for that, I'd like to know how.... You can definitely still buy these and that works for me.
I have used RTV on the v-groove joint before. Kind of a pain and you must not get any into the tank or it will float around in there and cause more grief a the worst possible moment.
The Divot