Two D15 grains makes a ???

How exactly did you "join the grains"?

Assuming you're talking about two RMS grains, why wouldn't you just buy an E or F reload for this case, saving money and not putting your RMS case (and your rocket) at risk?

If they burned simultaneously it's an E30

Dale Greene

Actually an E30, since they both burn at the same time. AN E15 would be if you burned one, ThEN burned the second one.

What you made is essentially the grain in the e28 reload kit.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

With tape - the same as you join any other rms grains.

Because there are no E or F reloads left in the country and a D15 is pretty crap (and I have 21 of them).

No risk. How many rms reloads use more than one grain? I don't see any difference (and it flew great).

Cool. Thanks for the info.

What case did you put it in? How did you get a liner to fit? What nozzle did you use? I think that is what everyone is confused about.

Oh, ok. I used a 24/40 RMS.

The motor was assembled like this: I opened a 3 pack of D15-4T motors - I flew one of them stock.

The other two, I took both D15 grains and taped them together like you do with some other reloads (G33?) and put the grains into one of the motor liners. (they are such cute LITTLE grains). It was a standard nozzel out of the pack with a standard delay assembly. Of course I ended up with a number of left over parts.

Clear? No magic, just two D15 grains taped and inserted into the liner of a standard 24/40 RMS.

As I said, I did this because I have way too many D15's and there are ZERO E's or F's left that I can get my hands on.

Result? Best flight my Estes Eliminator has ever had.

Will I do it again? Maybe...the aerotech mustang will do 1100ft on an E30...tempting.

snipped-for-privacy@mail.iinet.net.au (Impakt) wrote in news: snipped-for-privacy@news.iinet.net.au:

Was the nozzle throat diameter the same for the D15 and E28 kits? I do not believe they are.

Did you drill out the nozzle or did you leave it stock?

In what motor do you join grains with tape? The HPR grains just drop inthe case together with NO joining required.

BTW, an E28 (the RMS equivalent of the E30) most certainly uses a different nozzle than the D15. So who knows what you got. It could have overpressurized the casing, especially with the 2 grains instead of 1.

I beg to differ. I saw some on the vendor table yesterday...

And the D15 is a fine motor. MUCH better than a D12 in the same model.

For that casing, NONE. The MR casings were not designed for the multi segment grains. THe only one that currently exists is for the 29/40-120 casing and it is just to get around the 62.5g limit by having 2 40g slugs.

Then there is the minor detail that this motor was not certified, thus not permitted at any NAR or TRA launch, nor in any state that follows NFPA 1122 (just about all of them).

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

Bob, Australia's a little way from the US (Impakt's addy ends .net.au)

- I wasn't aware it had become part of the USA recently.

At least there are some Aerotech motors available over there, the UK's got none commercially available, and hasn't had for some time...

G.

I think this may be an equivalent way to determine what you had. Per the cluster table on the ROL site 2 D15 motors would give you almost 9 pounds of thrust or 100% of an "E" motor.

Three D15 motors would give you almost 13.5 pounds of thrust or 75% of an "F" motor.

Andrew Grippo

Reading all of this, I keep thinking the same thing, especially when you figure that there was twice the surface area burning that the case is designed for.

Keep your countries straight, Bob...

-Kevin

According to my calculations this modification increased the motor chamber pressure to nearly 1,500 PSI, with a peak thrust of over 18 lbs and a burn time of just under 1 second.

Gary

In article cZIme.3269$ snipped-for-privacy@fe03.lga, Andrew Grippo at snipped-for-privacy@charter.net wrote on 5/30/05 12:30 PM:

You're probably a bit lucky the motor didn't over-pressurize, though its possible they use the same nozzle for the single grain E and the D15. If so it's possible it had enough leeway to deal with the extra burn surface of the two grains (i.e. the ends of the grains facing each other, as in a "bates" grain).

Since these are C-slots, the tape would be used to keep the alignment of the slots.

Nice motor for a 24mm casing! Does this mean we can only do this on EX days? I hope so, I need a good excuse to go to Black Rock.

Andrew

Right, not a certified configuration. Plus, it's probably on the ragged edge of blowing off one of the closures at ignition.

See you at BR.

Gary

In article 61Lme.40484$ snipped-for-privacy@fe04.lga, Andrew Grippo at snipped-for-privacy@charter.net wrote on 5/30/05 2:51 PM:

Well, not quite twice, but 2 extra ends where the grains were "joined". As Gary calculated, he's lucky the case didn't blow.

Whoops, just went back to the start of the thread, and noticed the .au

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!