LVL 1 Failure

Never again will I rely on motor deployment!!
Launched with H128 an motor eject charge fired after nose was buried a foot in the ground.Its highly possible I didn't get igniter in far enough but then again who knows.:confused2:
Going to order the new cone an payload section then try again at Red Glare coming up this Oct. but it will be with my Ebay this time!!

Now for this blue tube material I have to attest that it is very tuff stuff.As seen in pix,payload took pretty heavy damage but lower section only had one small stress crack on a fin.I've seen a few lawn darts that took much worse damage.

Also if you read the review of the GearCam in Sept./Oct. Sport Rocketry ,these things are TUFF!! Here's my vid of launch it popped off I-beam at crash,came apart but yet recorded untill I turned it off.Dunno how to get youtube to work here so here's the link.
https://www.youtube.com/watch?v=cWzRId18F_4

Bummer, sorry to hear that. Good luck at Red Glare!

Fixed the link for ya-

[youtube]cWzRId18F_4[/youtube]

THX Brian seems all I touched today went in the pooper LOL :bangpan:

WillMarchant said:

Bummer, sorry to hear that. Good luck at Red Glare!

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THX Will Cheers!!

That's odd, i guess you got an Aerotech "bonus" delay. How high was the predicted altitude, and what delay time did you use?

Anyways, I don't think that your igniter placement is at fault. Once the motor lights, it should have started the delay anyways, regardless of whether the igniter was touching the delay. (If the delay didn't light, then it's a manufacturing/assembly error and a whole other issue.)

I don't think that motor ejection should be thrown away for ever, it is probably as reliable as a more complicated e-bay setup.

COrocket said:

That's odd, i guess you got an Aerotech "bonus" delay. How high was the predicted altitude, and what delay time did you use?

Anyways, I don't think that your igniter placement is at fault. Once the motor lights, it should have started the delay anyways, regardless of whether the igniter was touching the delay. (If the delay didn't light, then it's a manufacturing/assembly error and a whole other issue.)

I don't think that motor ejection should be thrown away for ever, it is probably as reliable as a more complicated e-bay setup.

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Well I never did a rocksim or anything but it went an estimated 1100-1200 feet,then nosed over....Rocket is 3 lbs without motor an I made sure hands were clean after lube'n up rings & threads.It was a regular delay far as I know.

Sorry to see that happen to you.I was watching your build and to see this happen is truly a bummer !!

Of all the reloads I`ve flown (I use the "other" guys) I have never had a delay /ejection fail yet........BUT never say never

As COrocket said ,motor ejection or electronics ,anything can happen....OR ....not happen.

Good luck with the rebuild.


Paul

Well, from the video, motor burnout was at 2:15, apogee was at 2:20, it hit the ground at 2:25, with ejection a second later. A standard medium Aerotech delay is a 10 second delay, so everything adds up. From motor burnout till ejection was around 11 seconds. (1 second is a normal variance in delay accuracy.)

With such a low altitude and the way it arched over, I would recommend a short delay (6 seconds would have been perfect) and you should be fine.

COrocket said:

Well, from the video, motor burnout was at 2:15, apogee was at 2:20, it hit the ground at 2:25, with ejection a second later. A standard medium Aerotech delay is a 10 second delay, so everything adds up. From motor burnout till ejection was around 11 seconds. (1 second is a normal variance in delay accuracy.)

With such a low altitude and the way it arched over, I would recommend a short delay (6 seconds would have been perfect) and you should be fine.

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Well seems ,acording to this info,I didn't mess up the motor build like I thought I had.If I ever use a H128 in this rocket again(highly doubtful) I'll make sure to use the short delay.

I left the nocecone planted in the ground,maybe next spring a baby rocket will sprout up.

sodmeister said:

Sorry to see that happen to you.I was watching your build and to see this happen is truly a bummer !!

Of all the reloads I`ve flown (I use the "other" guys) I have never had a delay /ejection fail yet........BUT never say never

As COrocket said ,motor ejection or electronics ,anything can happen....OR ....not happen.

Good luck with the rebuild.


Paul

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THX Paul
When I watched that thing arch over an head down was like getting punched in the gutt by Mike Tyson.
Look for my Blue Phenix Sr. build coming soon!! I should have "rebuild" (even though only real damage was payload) and the Sr. launch ready for Red Glare.op:

Ouch, I hate to say it. but I agree this time it looks like you chose a delay that was just to long... BUMMER..

Good news your decals are covered by our crash protection warranty.. I'll hook you up for the rebuild!

See everything didn't tun to poop.

Better luck next time. and it looks fixable to me!

stickershock23 said:

Ouch, I hate to say it. but I agree this time it looks like you chose a delay that was just to long... BUMMER..

Good news your decals are covered by our crash protection warranty.. I'll hook you up for the rebuild!

See everything didn't tun to poop.

Better luck next time. and it looks fixable to me!

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Yea just about 5 seconds to long LOL but fixable the payload isn't but main body seems just fine after a lil sanding.....wait maybe some duct tape that will fix anything right?

I feel your pain. My first L2 flight ended up crashing into the ground and it was an altimeter deployment. I honestly think I had drag seperation at motor burnout on mine, but as for the failure to deploy, that was all my fault. I crashed a beautiful rocket learning that lesson and know exactly that punched in the gut feeling, but that is rocketry. Luckily I had another rocket on hand for mine. Don't worry about it all too much, just live and learn and you will get it next time.

COrocket said:

From motor burnout till ejection was around 11 seconds. (1 second is a normal variance in delay accuracy.)

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The delay is from motor ignition, not motor burnout; the H128 burns for a little over a second. But yes, since delays can vary by +/-20%, this is normal variation.

On my L1 I went with the short delay on an AT H123 and then got a very early ejection (more than 20% early) but I guess I'd rather have early than late.

mikec said:

The delay is from motor ignition, not motor burnout; the H128 burns for a little over a second. But yes, since delays can vary by +/-20%, this is normal variation.

On my L1 I went with the short delay on an AT H123 and then got a very early ejection (more than 20% early) but I guess I'd rather have early than late.

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Oh, I always thought delays were measured from burnout. That's how it stated in on the NAR website https://www.nar.org/NARmotors.html.

The only other example i can think of off the top of my head is CTI has a K160 motor, with a 10 second burn and a 6 second delay. 6 seconds wouldn't make sense, because the motor would still be burning.

CORock is correct.

Delay is measured after burnout. "Coasting" phase is delay.

Delays are measured from burnout. The delay starts burning at motor ignition, and the physical length of the delay element is determined by the rate the delay burns during motor operation and the rate at which the delay burns after motor burnout and how long a delay you want between motor burnout and ejection charge firing.


i.e. a ten second delay burns for 10 s after burnout, but the delay has actually burned for longer than that (during motor operation). The length of the delay that burns during motor operation is dependent on the motor/type of propellant.

Well, I have just the opposite problem as you. I tried (twice) today for my L2, and my altimeter gave my problems. First flight, everything separated as planned at apogee, but my shock cord got wrapped around the tube (5 or 6 times) where my static ports are located, and no main @ 500ft. Second attempt, used a drogue to prevent the tangling/wrapping, but this time it just decided not to deploy the main. The altimeter must have gotten knocked silly on the first attempt. There was virtually no wind today, so I should have just used motor deployment (and used altimeter as a back-up).

This same set-up worked flawlessly on an I on Saturday???

COrocket said:

Oh, I always thought delays were measured from burnout.

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You're right, sorry, brain fart. For an end-burning BP motor the delay doesn't actually start burning until motor burnout, but for an AP motor the delay starts burning at ignition and has to be set up so it finishes burning at the appropriate time. But the specified delay time is after burnout in both cases.

BTW, even if you don't simulate your flight in more detail, you can always get a good idea of the appropriate delay using thrustcurve.org.

It is important to do some kind of simulation to get an idea of the flight characteristics of any new rocket. I like to do a sanity check with anyone that I am assisting in a certification flight. That way I can hopefully prevent some common errors that can occur to all fliers. Wrong delay times, parachute size and packing issues, motor assembly issues, etc can all be prevented with proper preparations. That being said, even with the best planning things can go wrong! Pick up the pieces and fly again.

jdud said:

Well, I have just the opposite problem as you. I tried (twice) today for my L2, and my altimeter gave my problems. First flight, everything separated as planned at apogee, but my shock cord got wrapped around the tube (5 or 6 times) where my static ports are located, and no main @ 500ft. Second attempt, used a drogue to prevent the tangling/wrapping, but this time it just decided not to deploy the main. The altimeter must have gotten knocked silly on the first attempt. There was virtually no wind today, so I should have just used motor deployment (and used altimeter as a back-up).

This same set-up worked flawlessly on an I on Saturday???

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Not to hijack the thread, but...

Did you test your battery before flight? And what altimeter and initiator are you using?

WillMarchant said:

Not to hijack the thread, but...

Did you test your battery before flight? And what altimeter and initiator are you using?

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^^^^^^^^^^ thread terrorist ^^^^^^^^^^
:jaw: LOL Gotta admit how pleased I am that I found this forum!! Everyone is so helpful THX

Hey duct tape can fix most anything...

Sorry it went bad, but sooner or later your gonna crash one.. you got it out of the way.. fix it up and do it better! I am sure you learned a little. so next time will be better.

Please help me with this discussion of AT delays. An AT medium delay will burn for approx. 10 seconds - whether it is in a 2 second burning motor, a 23 second burning motor or if it sitting on a table in your backyard and you stick a lit cigarette in one end - is this not correct? In other words, how is this 10 second burn time "measured" from burnout?

Delays burn more rapidly during motor firing, then slower after burnout. Each delay must be calibrated for each individual motor. This is why there are so many RDKs.
So a longer burn motor needs a longer delay length to achieve the same delay time after burnout.

Here is a handy pdf document with all rdk:s listed.

https://www.aerotech-rocketry.com/customersite/resource_library/Catalogs_Flyers_Data_Sheets/aeroTech_delay_lengths.pdf

Jeff said:

Please help me with this discussion of AT delays. An AT medium delay will burn for approx. 10 seconds - whether it is in a 2 second burning motor, a 23 second burning motor or if it sitting on a table in your backyard and you stick a lit cigarette in one end - is this not correct? In other words, how is this 10 second burn time "measured" from burnout?

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No. That's incorrect.

Delay times are calibrated from motor burn out to the ejection charge fireing, however a delay column begins burning at ignition, and burns throughout the motor burn. The burn rate of any solid propellant is pressure dependent, and the burn rate of the delay compositon is much faster during the propellant burn.

For illlustration, assume the burn rate of a delay column is 4x faster at pressure than after burn out. If the after burn out rate is 1/32" per second, then the hypothetical burn rate while the motor is burning would be 1/8" per second. The burn during a 10 second delay would be 10/32" + the amount consumed during the motor burn. If the motor burned for 1 second, the additional consumption would be 1/8", in a 2 second burn 1/4", in a 3 second burn 3/8" and in a 4 second burn 1/2", the total length required for a 10 second delay could be 7/16". 9/16, 11/16" or 13/16" for our hypothetical motor depending on motor burn time.

Bob

Thank you for that explanation - I incorrectly thought that the delays burn at the same rate before and after burnout, and I thought that all AT delays of a certain class (i.e. "medium") were the same length.

Nope. That's also why you can't just swap delays between different reloads - if you took an H123-M and an H242-M and swapped their delays, you'd end up with an H242-much longer, and an H123-much shorter (you could figure out the exact times if you knew the delay lengths and burnrates, which are available on AT's website).