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Anyone have experience using 18mm Aerotech Single-Use or RMS AP Motors?

  • Daniel Tyszka
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2 months 4 weeks ago - 2 months 4 weeks ago #8669 by Daniel Tyszka
One of my current projects is to figure-out a way to get one my older and heavier model rockets to “fly better.”

The rocket in question is an Estes Photon Disruptor, which I built a few years back per the original kit instructions to fly on 18mm black powder Estes motors, and then finished meticulously. Unfortunately, after finishing, the model turned-out heavy…Much heavier than the weight advertised on the kit packaging. Simulations after the build predicted that the model could only be flown on only a few of the highest impulse, shortest delay black powder (BP) motors in the Estes line without risking a crash. Flights with the rocket have confirmed the sim’s predictions…To date, I’ve only been able to fly it successfully on an Estes C6-3…And all of those flights have been very low, slow, arcing flights. This rocket also has a tendency to weathercock, resulting in even lower flights featuring “exciting” last-minute deployments. At the recent CMASS/RIMRA joint launch in June, I made the mistake of trying to fly this marginally powered, heavy rocket on a Quest C6-3 on a windy day. Despite what the simulations said, the flight didn’t go well, and the rocket weather-cocked, arced-over, and crashed before deployment. (Kenn: You were right to warn me about the overhyped / underpowered Quest C6 motors…I should have listened to you, despite what my simulation with the NAR-tested thrust curves said…D’oh!) The rocket suffered heavy damage to the nosecone and upper body tube, but I was able to successfully repair it. And after making a few mods to take some weight out (truncated the nosecone shoulder a bit, swapped-out the heavy ¼” elastic shock cord with 90# Kevlar cord) the rocket is ready to fly again.

Poking-around on TRF and the web, I was surprised to learn of the existence of 18mm Aerotech AP motors which would fit my Photon Distruptor. Looking at the manufacturer data sheets and thrust curves on the NAR website, and running some quick sims, it seems that these AP motors would give this rocket a better kick off the pad, and result in higher altitude flights (vs. Estes C6-3 motors). I’m looking at the Aerotech Single Use D10-3W and D21-4T as good candidates for this rocket. I was also surprised to learn of the existence of Reloadable Motor System (RMS 18/20) motors which might also work…D13-4W and D24-4T among them.

But before I take the plunge to try to fly my newly rebuilt Photon Disruptor on 18mm Aerotech motors, I wanted to ask-around a bit from folks like you who might have some experience with these motors.

Questions which come to mind include:

> Are the thrust curves published on the NAR website for these motors representative of current production stock? Looks like these motors were last tested back in the 1990’s. Wondering if the thrust curves have changed since then. And is the initial thrust build-up with these motors really as quick as the curves suggest, or do they take awhile to come up to full thrust?

> Data on the NAR test sheets indicates longer than advertised delay times…I’ve heard this is typical of Aerotech motors. Is the situation still like this?

> Anyone know if the 18/20 casing and 18mm RMS reloads are still in production? he Single Use (SU) D10 & D21 motors seem to be readily available from several sources online. But the RMS D13 & D24 motors seem to be harder to get. I’d probably go with the SU motors, but trying to decide if I’d find enough places to use a RMS 18/20 casing to pay for the upfront investment.

> Do the 18mm SU casings fit well in motor mounts and motor hooks originally built for 18mm BP motors? (Almost, but not quite?)

> Any comments on reliability (or Unreliability) of these 18mm Aerotech AP motors would also be appreciated.

I see there are also Aerotech SU & RMS AP motors in the 24mm size range as substitutes for C11 and D12 BP motors.

> Any differences in reliability when you go 1 size-up?

Dan Tyszka
CMASS Member; NAR #95916
Last Edit: 2 months 4 weeks ago by Daniel Tyszka. Reason: Added content

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2 months 3 weeks ago #8671 by Brenton DeBoef
I've only flown the single use D10 motors, but I really like them. I haven't put an altimeter in any of our flights with them, so I can't tell you if they match the simulated values, but they fit great in a standard 18 mm Estes motor mount and they fly great. The delays don't seem too long to me, but, again, I don't have any data to back that up.

My daughter's Estes Mercury Redstone is really underpowered on a C6-3. Low flights and scary slow take-offs. But it flies great on the D10-5.

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2 months 3 weeks ago - 2 months 3 weeks ago #8672 by Michael Lehmann
I too like the AT 18mm SU D motors. I've used the D 10's quite often in models like my Estes Dark Silver and Nike Smoke. I have only used D21's a few times in my Dark Silver as well, very fast off the pad and a lot of fun too. They fit good and the motor hook holds them just fine, but I usually add a wrap of tape around the aft end of the motor and hook "just in case".
I also have a set of the 18mm RMS cases, but as of yet, i haven't used them. I do know that with the RMS case the forward end of the motor hook needs to be filed down to allow the ejection cap to pass by, This is easier to do during the build than afterwards.

The 24mm RMS D's are nice too I've used the D 9's a few times and have a pack of the D 15's I have yet to try.

As far as reliability, this is Areotech we are talking about, so I'd stock up on some extra igniters. Other than that, once they light all is good.
Last Edit: 2 months 3 weeks ago by Michael Lehmann.

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  • Daniel Tyszka
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2 months 2 weeks ago #8674 by Daniel Tyszka
Brenton & Michael...Thanks for the insights.

I'll probably attempt a flight with an SU D10 at an upcoming CMASS launch. If that goes well, I may give a try with an SU D21.

Michael: I had read somewhere about the front-end interference issues on earlier model 18mm RMS 18/20 casings. When you had to file down your motor hook front end bend after the build, how far did you need to take it down? Did the cardboard engine block in the motor mount also interfere with the casing or ejection cap?

Also, do you know if the current production SU D10 & D21 motors come with a single igniter, or do those need to be purchased separately? Firstfire Mini's, right? I've had good luck with first time light-off of Aerotech SU F50 and G10s with Firstfire Jr igniters. Is light-off of the SU 18mm motors with Firstfire Mini's more problematic?

Regarding the "insurance" wrap of tape around the motor hook for that's great advice. I'm starting to do that even with BP motors as sometimes the rounded contour Estes-style hooks have a tendency to spring outward and allow kicked-out motors every now and then.

If any others have experience with these 18mm and 24mm SU or RMS Aerotech motors, would still like to hear your thoughts. Especially interested to know if the 1990's NAR thrust curves are still representative for these motors, if these Aerotech motors have longer-than-advertised delays, and if the 18mm RMS casings & reloads are still in production (due to very limited availability on the internet)

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2 months 2 weeks ago #8675 by Michael Lehmann
Daniel, the hook only needs to be filed down so that it doesn't overhang the cardboard thrust ring. The ejection cap will fit through the ring but can be a bit tight sometimes. I usually take a couple of layers out of the inside of the thrust ring for a smoother fit.
When I purchase the SU 18mm motors I usually buy the three pack. The three pack comes with three igniters. I believe they are the First Fire Minis. I need to look into getting some extra igniters myself as i have had a couple of failures do to "pop outs" where the initial pressurization of the igniter when it fired off has pushed it out of the motor before it lit the propellant I think in the past I have used Quest Q2G2 igniters as a replacement, but those are getting hard to find.

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  • John P. Petrakis
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2 months 2 weeks ago #8676 by John P. Petrakis
I flew the Estes ARF kit "Bandit" on a D21 some time ago... expecting a fire-and-forget scenario... I even got it back but it was a fun flight to be sure. I think for any extra heavy item that the 21mm ap motors will do a fine job. My Estes Phoenix comes in at 13 oz fully loaded and although I've never tried the D21 in that I'm sure it'd work far better than a D12.

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