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Rocketeer Gator
5th September 2010, 08:01 PM
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.
http://www.youtube.com/watch?v=cWzRId18F_4

WillMarchant
5th September 2010, 08:05 PM
Bummer, sorry to hear that. :( Good luck at Red Glare!

brianc
5th September 2010, 08:10 PM
Fixed the link for ya-

cWzRId18F_4

Rocketeer Gator
5th September 2010, 08:17 PM
THX Brian seems all I touched today went in the pooper LOL :bangpan:

Rocketeer Gator
5th September 2010, 08:18 PM
Bummer, sorry to hear that. :( Good luck at Red Glare!
THX Will Cheers!! :cheers:

COrocket
5th September 2010, 08:20 PM
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.

Rocketeer Gator
5th September 2010, 08:34 PM
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.

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.

sodmeister
5th September 2010, 08:39 PM
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

COrocket
5th September 2010, 08:53 PM
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.

Rocketeer Gator
6th September 2010, 12:09 AM
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.

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. :o

Rocketeer Gator
6th September 2010, 12:21 AM
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
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.:pop:

stickershock23
6th September 2010, 01:30 AM
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. :D

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

Rocketeer Gator
6th September 2010, 02:26 AM
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. :D

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

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?:eek:

DM1975
6th September 2010, 02:54 AM
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.

mikec
6th September 2010, 03:53 AM
From motor burnout till ejection was around 11 seconds. (1 second is a normal variance in delay accuracy.)

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.

COrocket
6th September 2010, 04:23 AM
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.

Oh, I always thought delays were measured from burnout. That's how it stated in on the NAR website http://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.

bandman444
6th September 2010, 04:43 AM
CORock is correct.

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

MarkM
6th September 2010, 04:57 AM
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.

jdud
6th September 2010, 05:41 AM
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???

mikec
6th September 2010, 05:59 AM
Oh, I always thought delays were measured from burnout.
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.

terryg
6th September 2010, 08:43 AM
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.

WillMarchant
6th September 2010, 02:58 PM
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???

Not to hijack the thread, but... :D

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

Rocketeer Gator
6th September 2010, 03:10 PM
Not to hijack the thread, but... :D

Did you test your battery before flight? And what altimeter and initiator are you using?
^^^^^^^^^^ thread terrorist ^^^^^^^^^^
:jaw: LOL :D Gotta admit how pleased I am that I found this forum!! Everyone is so helpful THX

stickershock23
6th September 2010, 09:30 PM
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.

Jeff
7th September 2010, 05:27 PM
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?

COrocket
7th September 2010, 06:20 PM
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.

rockie
7th September 2010, 06:54 PM
Here is a handy pdf document with all rdk:s listed.

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

bobkrech
7th September 2010, 07:34 PM
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?
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

Jeff
7th September 2010, 10:26 PM
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.

cjl
8th September 2010, 12:42 AM
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).

rockie
8th September 2010, 06:12 AM
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).


Thats when a list of the rdk:s comes to use.
I swapped my G67R-M delay into my G61W-M to make it an S.

One thing to note is that delays dont have markings so dont mix them !
I got mine mixed up at one point but they are different lenghts so i could mesure them.

bobkrech
8th September 2010, 03:19 PM
Thats when a list of the rdk:s comes to use.
I swapped my G67R-M delay into my G61W-M to make it an S.

One thing to note is that delays dont have markings so dont mix them !
I got mine mixed up at one point but they are different lenghts so i could mesure them.
The delay cavity in AT forward closures has a fixed depth, so the combined length of the delay column grain and delay space is fixed. You can not simply change the delay column grain (length) to change the delay, you also have to have the proper length (color coded) delay spacer as well. If you don't use the proper parts, the forward pressure seal is compromised and you are likely to igniter the ejection charge at or near motor ignition.

Below is the AT delay documentation.

http://www.aerotech-rocketry.com/uploads/2648cc1c-803d-4e65-8293-e4063a7fcff9_29mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/uploads/932ae6bf-0920-4dca-be63-e28c28885b55_38mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/customersite/resource_library/Instructions/RDK_Instructions/54mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/customersite/resource_library/Instructions/RDK_Instructions/rms_delay_mod_inst.pdf

http://www.aerotech-rocketry.com/uploads/02a31b31-ee1a-4d91-b134-39d6a6911463_dda_instructions.pdf

A good non AT explanation of the AT delay behavior is fould here http://www.rocstock.org/wizards.html where you will find information on delay grain sizes vs delay for various propellants in the motor info section. Make sure you read the caveats before you use this data.

Bob

rockie
8th September 2010, 05:10 PM
The delay cavity in AT forward closures has a fixed depth, so the combined length of the delay column grain and delay space is fixed. You can not simply change the delay column grain (length) to change the delay, you also have to have the proper length (color coded) delay spacer as well. If you don't use the proper parts, the forward pressure seal is compromised and you are likely to igniter the ejection charge at or near motor ignition.

Below is the AT delay documentation.

http://www.aerotech-rocketry.com/uploads/2648cc1c-803d-4e65-8293-e4063a7fcff9_29mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/uploads/932ae6bf-0920-4dca-be63-e28c28885b55_38mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/customersite/resource_library/Instructions/RDK_Instructions/54mm_rmsp_rdk_instr.pdf

http://www.aerotech-rocketry.com/customersite/resource_library/Instructions/RDK_Instructions/rms_delay_mod_inst.pdf

http://www.aerotech-rocketry.com/uploads/02a31b31-ee1a-4d91-b134-39d6a6911463_dda_instructions.pdf

A good non AT explanation of the AT delay behavior is fould here http://www.rocstock.org/wizards.html where you will find information on delay grain sizes vs delay for various propellants in the motor info section. Make sure you read the caveats before you use this data.

Bob

Yes forgot to mention that, i didnt have the right spacer it was a bit longer but i cut it flush with an exactoknife. I guess its harder if its the other way around.

The delays are quite expensive for us in sweden. they cost like 6$ for a single one (not including shipping). So better use what one has already :)

Sorry if it got a little of topic. :P

bobkrech
8th September 2010, 10:47 PM
Yes forgot to mention that, i didnt have the right spacer it was a bit longer but i cut it flush with an exactoknife. I guess its harder if its the other way around.

The delays are quite expensive for us in sweden. they cost like 6$ for a single one (not including shipping). So better use what one has already :)

Sorry if it got a little of topic. :P
AT has been supplying M delays on many motors. You can shorten a dealy by drilling it out with a 3/16" drill bit as detailed in reference 4 of my previous post. That way you don't have to cut the delay nor do you have to change the delay spacer length.:)

I personally recommend that the drilled out side face the propellant grain rather than the ejection charge.

Bob

RoyAtl
8th September 2010, 11:57 PM
I personally recommend that the drilled out side face the propellant grain rather than the ejection charge.

Bob

I know that's the current recommendation from AT as well, but years and years and years ago, I was taught to drill the ejection side. Had no problems with many I211-m to s conversions and various H motor conversions.

Is there some operational effect (other than hibachi delay burning after ejection!)?

bobkrech
9th September 2010, 12:09 AM
I know that's the current recommendation from AT as well, but years and years and years ago, I was taught to drill the ejection side. Had no problems with many I211-m to s conversions and various H motor conversions.

Is there some operational effect (other than hibachi delay burning after ejection!)?
Probably not, but the hibachi effect will increase the probability of a recovery failure cause by burning of the recovery hardware.

Bob

cjl
9th September 2010, 01:56 AM
If you drill a large hole on the side facing the black powder, you could have BP fall down into the hole, reducing the amount in the ejection well and weakening your charge.

Pantherjon
9th September 2010, 02:51 PM
If you drill a large hole on the side facing the black powder, you could have BP fall down into the hole, reducing the amount in the ejection well and weakening your charge.

I don't think it would reduce it in any real noticeable manner..After all you would still have the same quantity/volume of BP just in a different configuration..Now, I could see that if the hole is large enough and enough BP did go into it that it may reduce the pressure some as the BP isn't as tightly packed. But, I don't think it would reduce it significantly to result in a deployment failure..:2:

sunward
9th September 2010, 03:18 PM
....Its highly possible I didn't get igniter in far enough but then again who knows...
A good trick and a habit to measure how far the igniter needs to be inserted is to place it on the outside of the motor case. No guessing. You do this before mounting the motor in the rocket.

As mentioned, delays are +/- 20%.

And read the directions on the motor. The delay times are set different for each company and may not correspond with the setting on any drill tool.

cjl
9th September 2010, 06:56 PM
I don't think it would reduce it in any real noticeable manner..After all you would still have the same quantity/volume of BP just in a different configuration..Now, I could see that if the hole is large enough and enough BP did go into it that it may reduce the pressure some as the BP isn't as tightly packed. But, I don't think it would reduce it significantly to result in a deployment failure..:2:

In general, I agree with you. It will be a small effect, but if you already have a very marginal ejection charge, it could possibly push it just over the edge. If your ejection charge is that marginal though, I would say that it needs a bit more BP anyways, drilled or otherwise.

Pantherjon
10th September 2010, 05:34 AM
One other possibility would be when the rocket arcs over at apogee and the BP moving away from the front of the delay grain..If the drilled part is towards the foreward end then small possibilty the delay won't ignite the BP...

cjl
10th September 2010, 06:00 AM
That doesn't even require the rocket to arc over. From the instant the motor burns out, the BP will be forced to the front of the container it is in.

Sailorbill
16th September 2010, 12:22 PM
Thats when a list of the rdk:s comes to use.
I swapped my G67R-M delay into my G61W-M to make it an S.

One thing to note is that delays dont have markings so dont mix them !
I got mine mixed up at one point but they are different lenghts so i could mesure them.

It might be to your advantage to purchase all of your motors with medium or long delays and a RMS™ Delay Drilling Tool (http://www.aerotech-rocketry.com/news.aspx?y=2010#n127). That way you can always adjust down to the desired delay. :2:

G2Rockets
16th September 2010, 01:51 PM
It might be to your advantage to purchase all of your motors with medium or long delays and a RMS™ Delay Drilling Tool (http://www.aerotech-rocketry.com/news.aspx?y=2010#n127). That way you can always adjust down to the desired delay. :2:

I agree Bill, I buy the longer delays and reduce them. However, I use the folowing as a guidline to do it without the drilling tool.

http://www.rocketreviews.com/featured/tip_featured22.shtml
JOhn