I wanted to run the "Stunt Tank" version of Cox International's new aluminum backplate today, and rather than build up another engine, I chose a faithful old friend that's dragged assorted flying machines around the Hill and S.M.A.L.L's for a long time.

With no changes other than new gaskets and pick-up tube, the old Golden Bee got it's backplate swapped, and was bolted to the stand and cranked up. I'd put several runs on the Babe Bee, but I decided to REALLY run it's golden sibling by doing on-the-run refuels just for the heck of it.

Once settled into it's run, the GB was real steady, and probably would have flown the B.O.T. all the way to Little Rock if it could have lifted the fuel. After 20 minutes or so, I let it run out it's fuel with no needle-fiddling along the way.

One note to any new-comers: While the old hands all know this...it is important to use the fillister style backplate screws to prevent fuel leaks. I just used the GB's originals in the test, with no leakage, but I think Matt and Bernie stock them if you need replacements.

The last photo is the answer to a question that arose, asking if the aluminum backplate has a steel insert to accept the needle valve. The magnet says, "Yes!"


So now, the Q-Tee is on charge, and we may sneak a flight in later today.

https://coxengines.ca/

What’s the advantage of the metal plate ?

After the original metal backplates were sold (the machine that made them was worn out), the manufacturers went to molded plastic versions.
For me, these are much weaker at the mounting lugs and also where the screws hold them to their tank.
I'm really hopeful that these will provide \ the same strength as the originals.

Interesting how the cheap production backplates had metal venturis and the black backplates didn't...
I used to put a strip ot thin plumbers tape to seal the threads but this would put too kich stress on the threads and strip them..

I now put a dab of foamtac on the threads of the needle.. I also remove the spring and use a 4/40 washer and a piece of tubing to seal the assembly..

The plastic warps if overtorqued .. I take the tank and backplate and sand them flat with 400 grit over a piece of glass..