Tonight's project.....Stunt Babe Bee

ZACATTACK wrote:Hey that looks like the one out of my 71' Bug!!

You don't mind do you?

Been looking for a 5cc Stunt tank for a while...... You find all the good stuff!

Looks good.

Jason_WI wrote:Been looking for a 5cc Stunt tank for a while...... You find all the good stuff!

Looks good.

It was as easy as calling Cox International. They have them on the website

Oh, I thought you had the old original version.

Bernie has them, I asked, he delivered.

They have the narrow venturi passage so drilling them out is needed (Well, a good idea if you want the power), but quite easy to do. Take a 2mm or 5/64 drill and run it through using a pin vise or wrap some tape on the shank. The aluminum is pretty soft so this only takes a few dozen turns to go all the way through.

I have one built that is quite similar, I don't remember the cylinder I put on, but it sings a sweet song. I don't know what it is going onto though, probably my Sig Skyray.

I used the same narrow case too!

Phil

Phil,

How long does yours run? I am getting less than a minute. Not good.

I was going to drill out the venturi, but with the fuel economy as it is, it will only make it worse.

I need enough time to at least run out to the lines. BTW do your fill/vent tubes leak?

Ron

If your fill/vent tubes leak then you have a problem. If this is a glued together tank from Bernie then it shouldn't leak from the glued joints, however airflow over the tops of the tubes may cause siphoning. This siphoning is usually minimal.

If siphoning from airflow is excessive, file the tube ends to have a slight angle facing forward to catch the air then the siphoning should stop. The ends should not look angled without close inspection.

I didn't time it but it felt like about 3 minutes. I whipped up a test stand to try measuring thrust, and the engine was powerful enough to take the test stand walkabout so I had to drop everything and hold on to it. I wasn't able to tach. The needle was also self adjusting on me (easy fix with fuel line over the needle in place of the spring) I think I need to restrain my stand better or go back to using a 2x4.

On all the new tanks I have (as opposed to vintage tanks) I have been having problems getting the tank to back plate to seal at the rim. If the tank is leaking at the seam or the venturi then real short run time is expected. I have been using anaerobic sealant on the rim of the tank. I fill the groove, then clean the inside of the tank carefully, assemble and then clean the outside of the tank.

Make sure the sealant is aluminum safe, or at least non-corrosive. I have seen significant damage to aluminum car and boat engine parts from the wrong sealant being used. I can imagine the damage on these tiny engines.

Phil

Don't forget Ron the higher the nitro, the greater the n/v setting, the quicker
the fuel gets guzzled.

John Goddard wrote:Don't forget Ron the higher the nitro, the greater the n/v setting, the quicker
the fuel gets guzzled.

Good point. I am running 15% nitro.

Phil

I will mess with it more this weekend. I have a leak somewhere. I used a dental floss gasket on the backplate. Dart shaft o-ring on the venturi. New crank gasket on a lapped case and tubing over the NV. I can still hear a hiss when I pressurize the tank. Perhaps the screws? That one is usually not a problem for me.

25% Sig JB....... About 40 degrees out when tested.

Ron