Shakin' the Rust off

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Gregor

Well-Known Member
Joined
Oct 10, 2012
Messages
169
Reaction score
0
B.A.R. here. New to mid-power. So I dug out my rocket stuff out of storage. I have a built but unflown Super Big Bertha and an Initiator. There were also some econojet g35-4w's and an AT f25-4w. I know these are not on the recommended motors list but was wondering how they might work with the Initiator. For the SBB, I had extended the motor mount so that E engines would fit. I also used a longer, more aerodynamic(pointier) nose cone. For this rocket, I have some d12-3's to test it with. I also have some E9-8's and some E9-4's. Would both types of E engines work with this rocket? My last question is concerning the fact that all of these engines and igniters(copperheads for the AT's) have been in storage for about 3 years. The storage unit WAS climate controlled. Are they likely to still work? I don't have a lot of moola, so if I can go out and have a great launch day with the stuff I have, so much the better! Thanks ahead of time.
 
Welcome to TRF! You'll like it here.

Last night I stumbled across some very old reloads at my LHS. They're old enough that the artwork on the packaging is different than the current stuff and there's some white residue that has formed on the ends of the motor grains. some of the delay grains are in individual plastic bags, most are not.

Still, 3-packs of several different size 24mm loads for $5.95 each. I wasn't about to pass that up.

So far, I've asked two different people if I should worry about them or if they'd be alright and both people said don't worry about it, they'll be fine.

Not exactly the definitive answer you're looking for, but someone else will chime in for sure.
 
Just some issues to be aware of with old motors....I recently came across a large cache of 14 year old motors (composite) in the back of what had been my closet at my parent's house. A nice mix of D21, 18mm E25, F25, E15,
E30, F14 and an F50. The E15 were unusable, as the grain had swelled to the point that there was no longer any slot for the ignitor. The F25's work, but they chuff on the pad a bit before taking off. The same for the F14's. The D21's seem to be fine. Haven't tried the others yet. AN IMPORTANT POINT TO BE AWARE OF....so far all of these motors have exhibited delays longer than those posted on the package (e.g., 4 second delays acting like 6 second, 6 second delay 8 or 9 seconds, etc.) Still, looks like most of them will be usable, you just need to exercise a bit of caution and make sure to use a hot ignitor if you can.
Craig
(Anybody want to buy a dozen "end burning" E15's? ;)
 
If the grain has swelled that much, I doubt they'll burn at all. APCP motors are hydro...... um.... I forget the word, but they absorb moisture, even out of the air. Essentially, key opened composite motors in plastic bags and they'll work fine forever (pretty much). I just pulled out a 6 month old E28 and it worked like a charm because it had been sealed in a plastic bag. Same goes for some 3 or 4 year old AT B6-2 reloads I found at the local hobby shop that no one wanted (I wish AT would make them again, they sound MUCH better than Estes B6's).

So basically, if there are no visual defects and you can get the igniter in :D, you should be fine.
 
They should be fine, just use a really hot igniter to get them moving. The copperhead probably won't get them lit since they've been sitting so long.

Oh - and the F25-4 should be fine in the Initiator...On mine, the F40 flies great, but the 7 second delay is usually too long.
 
Thanks for all of the responses. So it sounds like new igniters are called for. Does anyone sell them for composite motors in anything but 3 packs. What is the most economical way to get them?
 
Thanks Paparoof, I PM'd plasticpaul. Does it require any expertise to put together?
 
Thanks Paparoof, I PM'd plasticpaul. Does it require any expertise to put together?

It's easier than building a rocket. the hardest part is finding a decent scale. I wasted 30 bucks on one at Target cause I didn't wanna wait for shipping from https://www.rightonscales.com/web/7001.htm now I'm gonna spend another 30 bucks there anyway to get a (hopefully) good one.

I use PlasticPaul's formula and basically follow this set of instructions from infocentral for the wiring part.

I bought my nichrome wire from shreadvector on this site and can't think of any reason why I won't order from him again next time I'm in need. It works as expected and it's CHEAP.

For the non-burning part of the ignitor leads, I use standard telecom cross-connect wire - the same stuff thats in standard CAT5 cable, just in a single pair. talk about cheap....

I haven't actually run the numbers but altogether I'd be amazed if each ignitor even costs me a dime.
 
Back to one of my original questions. I've never used flight sim software. Does anyone know what the g35-4w econojets would do to my initiator? Too short of a delay? If it takes it 2000 feet, is that out of sight?
 
I saw an Initiator go up on a G80-7T this past weekend. A G35-4 should work fine, and even if the deployment is slightly early, the Aerotech recovery system should be able to stand up to it. Just make sure it's not too windy (10MPH+) or you'll be walking a LONG way to get it.
 
I would be careful with the 4 second delay....I just ran it through Rocksim and
it shows deployment coming way early, with the rocket moving at 144 ft/s at deployment with altitude (at ejection) coming at 1887'. A G35-7 gives an altitude of 2153' with ejection coming at 37 ft/s (rocket is tilted nose up at ejection). This is assuming the weight of the rocket as 16 ounches (a couple of ounces over what Aerotech claims....you should weigh your rocket just to be sure. I find that mine after painting weigh a bit more than the catalog weight).

A double check with Wrasp shows an altitude of 1730' with the 4 second delay ejecting early at 91 ft/s and the 7 second delay ejecting just about at apogee with the rocket moving down at 10 ft/s. Optimal delay is 6.7 seconds.

So, it looks like the 7 second delay is the one to go with.

Craig
 
Craig, I appreciate the data. Could you run the initiator with a f25-9w? I suspect the delay may be way too long, but that is the only other motor I have besides the g35-4's and one f25-4. Mine seems to weigh right at 1 pound with paint and an f engine in the mount. I downloaded the trial version of rocksim but have no idea what I'm doing yet. Also, the simulation ends at apogee with the trial version.
 
I ran the numbers and the F25-6 is indeed the ideal choice. The 9 second delay might be doable, but a bit of a gamble. The F25-6 has ejection nose up at 1506' with the rocket moving at 29 ft/s. The F25-9 has the rocket hitting an altitude of 1518' with a nose down ejection and the rocket moving at 62 ft/s. I ran these numbers in Rocksim and brought the weight down to 15 ounces based upon the weight you said your rocket is (actually, it is probably closer to 14 ounces since the motors weigh more than an ounce).

Wrasp shows an ideal delay of 6 secons, with the rocket hitting 1387' in altitude and 1.4 ft/s with the 6 second delay and 91 ft/s with the 9 second delay.

For myself, I try to keep deployment speeds under 40 ft/s but if the kit has a strong recovery sytem I shoot for keeping it under 70 ft/s.

Craig
 
I ran the numbers and the F25-6 is indeed the ideal choice. The 9 second delay might be doable, but a bit of a gamble. The F25-6 has ejection nose up at 1506' with the rocket moving at 29 ft/s. The F25-9 has the rocket hitting an altitude of 1518' with a nose down ejection and the rocket moving at 62 ft/s. I ran these numbers in Rocksim and brought the weight down to 15 ounces based upon the weight you said your rocket is (actually, it is probably closer to 14 ounces since the motors weigh more than an ounce).

Wrasp shows an ideal delay of 6 secons, with the rocket hitting 1387' in altitude and 1.4 ft/s with the 6 second delay and 91 ft/s with the 9 second delay.

For myself, I try to keep deployment speeds under 40 ft/s but if the kit has a strong recovery sytem I shoot for keeping it under 70 ft/s.

Craig
 
I didin't see anyone answer regarding your SBB and the Estes E9's. The 4 second delay would be just about perfect (as is the D12-3). I'd stay away from the 8 second delay unless you are chad staging with a D12-0, which the SBB handles with no problem.

kj
 
AN IMPORTANT POINT TO BE AWARE OF....so far all of these motors have exhibited delays longer than those posted on the package (e.g., 4 second delays acting like 6 second, 6 second delay 8 or 9 seconds, etc.)

I've been told you can spot these rancid delay grains by their off-color [going towards greenish?]. I ran into a bit of bad luck with these for a while that resulted in one zipper and one core sample in one day.
 
Back
Top