I had a few tasks to take care just before Balls. Unfortunately I did not get a chance to do a proper test firing due to the 50+ days of 100° and higher temps and the burn ban in my area. This post will update the final configuration for the tank connector and which grains I am bringing.
Previous posts addressed rethreading a paintball valve to 13/16 x 14 from the 1/2G x 14. This was quite adequate but my lack of a lathe led to me other options. This led me to look at another hybrid that is also out of production. The owner of Alpha Hybrids reached out to me when I started this project and donated some of his original hardware. His design also uses off the shelf hardware. After checking out his motor I chose to utilize a combination of both the Aerotech and Alpha design. I modified a paintball bulk tank connector and an agriculture style hydraulic connector, both available from Amazon.
Original Alpha Hybrids motor above, this design was certified by Tripoli.
Although I did find a seller on E-bay offering a 10 pack of the same paintball adapter for 25 plus free shipping, so I took advantage of that to have spares in case of failures of the rethreading process. After removing the QD nipple and reprofiling the threads to fit the Aerotech forward closure, I added an stainless adapter to attach the hydraulic coupler to.
I found this to be about the safest option while not having to worry about the nipple on the injector engaging the pin valve on the the tank. It also ensures a safe coupling and disconnect to prevent launching a a flight tank inadvertently after filling and replaces the earlier ball valve option which could have been dangerous if procedures were not followed.
On top of the final tank configuration I finally got some high temp synthetic paraffin. After repeated attempts to procure some Shell Sarawax 70 without much luck, I was able to find an independent wax manufacturer in Germany. After telling them what I was using it for they sent me samples of 4 different types to try out. The one that blended best with the sorbital mixture was T19 from Deurex AG.
The important part is the melting point, it is very close to the melting point of sorbitol, although the density is lower, constant stirring and pouring when it begins to solidify on the side of the pan gave the best results to keep it suspended in solution. the synthetic paraffin also stops the hydroscopic nature of sorbitol.
I also received three other samples, one T49, was a high temp wax but did not cast too well with the sorbitol but has promise as a paraffin grain combined with AL and possibly KN.
The following grains were cast for Balls with a Delrin rod in both 5/8 and 1″ to shape the core. To assist removal they had to be cold soaked in the deep freezer for a few hours then the core tapped out.
I have noticed that Sorbitol has a pretty significant shrinkage along the vertical axis after casting the hot liquid so it is best to pour the grain longer than you need and then trim.
I hope this series has been beneficial, I will post results when I get back from Balls.
Patrick Carroll 