Double Rocket

Double Rocket



The first advanced project is a double pressure chamber. This double rocket is a 3-liter pressure chamber. Two 1.5 liter bottles are joined by a small tyre valve rod. I found several versions of these plans online, but the best, and I suppose the original plans should be credited as "The Robinson Coupling". The hardest part of this project is sealing the joint where the couple is located. The air pressure inside the container needs to hold at 60 -100 psi. I still looking the best sealent/glue that can be used to avoid air from coming out from the the joint where the couple is located. So far I have found that Sally glue (can get from GIANT store) is flexible and strong enough to hold the seal. Be patient, the adhesive needs at least 24 hours to cure. Don't pressure test until then. But that glue still cannot hold the pressure up to 100 psi. I still looking the suitable glue to solve this problem.

The coupler can be made one of two ways. Either by joining bottom to bottom, or bottom to top. I will describe the joining bottom to top because it is easy to do it compare the joining bottom to bottom.

PARTS LIST:

(1) Tyre valve

(3) Nuts

(2) rubber Washers (can made from bicycle tube)

(1) 1.5 liter bottle cap

Teflon tape

Building the "Valve Coupler"

Start by carefully drilling a small hole in the bottom of the 2-liter pressure chamber and the bottle cap. The tyre valve should just barely fit into the holes. Be careful not to remove the blue plastic gasket at the bottom of the bottle cap. (It will help seal the joint in the end.) Dry fit all parts to make sure it will work before you go any further.

Wrap the tyre valve with a couple layers of Teflon tape. Thread one of the hex nuts onto the stem of the tyre valve until you get to the half way point. Set aside.

Carefully push the first rubber washer(can made from bicycle tube) into the neck of the main pressure chamber. You will need to use a socket and wrench with one or two socket extensions to reach the bottom of the bottle. Balance a nut and the washer on the head of the socket and place the threaded tyre valve into the hole from the top down. With the skill of a surgeon, drive the nut and washer onto the rod. Tighten with a wrench on the outside surface. (At his point you could add a small dab of Sally glue to seal.

It will be necessary to shave down the second rubber washer to fit inside the bottle cap. The second bottle must be able to screw into the cap all the way down to the gasket. Sometimes the washer sticks out too much. Apply the washer and the nut and test fit the second bottle to make sure it seats well. If the second bottle sits crooked, then it is hitting the washer. Remove assembly and shave the washer again. Once you have the right fit, tighten the entire assembly.