Something like AT F24w-4. This is a really light rocket so it might tolerate up to 4 sec of delay.What size/type of motors are you looking at? You will have to choose your motor carefully for the smallest possible delay. CTI has a much wider of ranges to choose from than AT in this regard.
This makes me realize that if you dished the chamber side and domed the chargewell side, you could probably go a tiny bit smaller on the delay for quite a bit of effort.It *might* be possible to drill a delay grain down to 2 seconds by using a much smaller drill bit, say 3/32". I don't know the tensile strength of a delay grain, but for example, the end of a 3/32" hole at 700 psi would see a force of 4.8 lb (area of hole in in^2 times pressure in lb/in^2). The question remains: would that area (0.0069 in^2) withstand a force of 5 lb? If so, it'd be okay.
It would probably be necessary to face the flat, un-drilled side of the grain to the combustion chamber. If the drilled side faced the chamber, the hole would increase in area during the burn, increasing the force. Unfortunately, facing the flat side to the combustion chamber means that on burn-through, there would still be a lot of the delay grain left to burn, and the flame would come out both ends of the delay. Possible damage to the part of the booster that is ahead of the delay grain.
I've never done this and don't know if it would work in practice.
Best -- Terry
PS: I don't know the size of the bit used to drill delays, but as an example, if the drill (and its hole) is 3/16" in diameter, the force on that part of the grain would be almost 20 lb.
Domed the chamber side and dished the charge well side, maybe? Seems more reasonable. Though after three fermented malt beverages, I don't know what is and isn't reasonable...This makes me realize that if you dished the chamber side and domed the chargewell side, you could probably go a tiny bit smaller on the delay for quite a bit of effort.
I don't see many pressure vessels shaped that way -- that would an interesting set of experiments though, most pressure vessels aren't flying cash-to-smoke schemes, either.Domed the chamber side and dished the charge well side, maybe? Seems more reasonable. Though after three fermented malt beverages, I don't know what is and isn't reasonable...
Ok, I can picture doming (I think), but I'm having trouble picturing dishing/
Maybe a pictorial?
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