ScrapDaddy
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When it comes to 18mm composites as far as i know there are only 3 the D21, D24, and the D13. Why Is it that there are only 3?
but it goes both ways you can get 18mm reloads at about half the cost of a 24mm reload and you can use adapters
Otherwise there would be alot more of them on the market. The cost return is just not there.
There can also be significant technical challenges in very small composite motors, including efficiency problems and ignition methods.
Use a q2g2 igniter
well actually D12's sell at about $12 dollars and a 3 pack of reloads for a 18/20 is $7.90 at valuerockets.com
...but once I use my 40% off coupon at Micheal's......
Also, the first two online retailers I check sell D12 for less that $10.
I used a friend's 24/40 casing once.....to much of a PITA to use. Way to easy to get grease on the delay element. I can only imagine how much more difficult the 18/20 is to use.
I would bet that 18mm rockets are probably marketed more toward kids. One must be 18 to buy composite motors. https://tinyurl.com/ajh2f Not a good idea to have a product that most users can't even buy.
My philosophy is this....Anything I build that I would want will fly on a D, I would probably want to fly on a E. So I put a 29 MMT in it to keep my options open (F, G, etc).
Alan
NAR & TRA L2
Use a q2g2 igniter
In an 18mm motor, a twin-lead igniter like a Q2G2 can take up a significant portion of the throat area. This not only increases chamber pressure at startup, but also creates a significant pressure drop as the leads are ejected through the throat. Depending on the propellant composition, this pressure drop can trigger combustion instability, or even extinguish the motor.
What I can assert is I get Copperheads to ignite the motor about 70% of the time. With the Q2G2, I am at 100%.
As I said, it depends on propellant composition and motor design. (We're very blessed with HTPB, from a combustion stability standpoint.) For different 18mm composite motors, things may (will) change. You may not even be able to fit an igniter through the throat of an 18mm APCP B motor. Longer 18mm motors become more workable from an igniter standpoint (cf. some of Rocketjunkie's designs, or Kosdon's 18mm G motors :cyclops since the throat diameter grows as well.
edit: Not to say that these challenges aren't insurmountable. They're a fun problem to solve. But a commercial manufacturer may not want to deal with the trouble, when there's money to be made elsewhere.
I was working at AeroTech when the 18mm RMS 'B' & 'C' reloads were cancelled.
As I was reviewing the sales data at that time, the 'B' & 'C' reloads had been ordered exactly ONCE by each of the hobby distributors/dealers. There had been no re-orders in over six months and no indications that there would be any orders.
I then made a presentation to the owners of AeroTech concerning this development and my recommendation was to discontinue these small reloads. My recommendation was accepted and as far as I know, AeroTech never received any flak over discontinuing the 'B' & 'C' reloads.
They just never sold enough to justify keeping them in production.
A-ha! You admit it. It's all your fault!...and my recommendation was to discontinue these small reloads. My recommendation was accepted
YOu did kill the b and c motors!!!
Gary also said that in a thread on one of the forums (either here or at YORF) last year. I'm not sure if the thread was actually about these topic, but I do remember asking about them at one point, and then seeing his response. I was wondering about the same thing as ScrapDaddy.I was working at AeroTech when the 18mm RMS 'B' & 'C' reloads were cancelled.
As I was reviewing the sales data at that time, the 'B' & 'C' reloads had been ordered exactly ONCE by each of the hobby distributors/dealers. There had been no re-orders in over six months and no indications that there would be any orders.
I then made a presentation to the owners of AeroTech concerning this development and my recommendation was to discontinue these small reloads. My recommendation was accepted and as far as I know, AeroTech never received any flak over discontinuing the 'B' & 'C' reloads.
They just never sold enough to justify keeping them in production.
........I was wondering about the same thing as ScrapDaddy.
MarkII
As you look at the selection, you almost inevitably wonder about it at some point. But if Aerotech started making them again, how many B and C reloads do you think you would ever actually buy? (Be honest.) My own take is that rather than fret over the fact that there are only a couple of reload formulations on the market currently for the 18/20 RMS case, instead I appreciate the fact that the 18/20 RMS system even exists at all and that someone makes commercial-grade reloads for it. That's pretty cool when you think about it. If sufficient interest ever built up for 18mm B and C reloads, Aerotech would no doubt consider making them again.Great Minds Think Alike
If you feel so strongly about this I suggest you contact Aerotech and ask them to remake B, C, D loads and use a competetors ignitors :roll:
Ben
I assume retirement was short lived...
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