The 98mm forward closure uses the same style pin valve as the 54mm. Unfortunately, it is no longer produced and uses a non-standard 13/16-14 thread. Thankfully, we found a solution with the standard paintball remote tank adapter, which uses G1/2-14 and only required a reprofiling of the threads with a die. If you wish to go with a more original style, you can follow Lelands instructions to rework a paintball tank pin valve here: https://pcarroll2525.com/additional-aerotech-hybrid-projects/ .
The only difference between the 54 and 98mm forward closure tank adapters is the hole size. The 54mm uses a 1/8 NPT, while the 98 uses a 1/4 NPT. This requires drilling out to accommodate the nipple as the hydraulic coupler is larger for the higher flow. Available from here: https://www.amazon.com/Pressure-Hydraulic-Coupler-Replaces-Enerpac/dp/B074DL4QRC?ref_=ast_sto_dp
In keeping with the method to make sure it can be replicated with basic hand tools that most rocketry hobbyists should have available to them. The paintball remote tank adapter was step-drilled from 11/32 to 27/64 and then reamed with a pipe taper reamer in preparation for threading.
One of the things I learned from threading the 54mm adapters was how hard it can be to cut straight threads by hand on small fittings. I scrapped a few of them on the last project. To correct this, I used a hand tapping device that keeps the tap in line to ensure it stays straight. Best results are obtained by using the 13/16 die to hold the adapter while the threads are cut,
This is the final configuration for the tank adapter; it does not add much length over the original while also adding a 3K burst disc. The brass tank adapter was custom made, the burst disc, ag coupler, and nipple are from Amazon, and the paintball tank remote adapter was left over from the 54mm project.
Next: Original style and new 2-liter composite tank
Patrick Carroll 