7-Second Coasting is Not Enough - Need a D12-14 motor...

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DaugerDude

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My multistage LPRs I've custom-designed to use D motors are getting great altitude, like 1830+ feet on a single D12-7 and 2900+ feet on two-stages D12-0,D12-7, measured using a Jolly Logic AltimeterThree. On my next opportunity I'm launching 3 stages. I'm exploring what's possible just with D motors.

A dilemma I've discovered is that the 7-second coast time is not enough. Examining the data out of the AltimeterThree, every time with my design, the ejection charge fires well before apogee. If I'm interpreting the accelerometer data correctly, my rocket is still ascending at 73-86 mph UPWARDS when the ejection charge fires. It is flying higher and faster than OpenRocket originally predicted. So if somehow ejection could be delayed much more than 7 seconds, my rocket's apogee could have been even higher. The parachute is slowing the ascent. Ejection at high speed is corroborated by the torn (repairable or replaceable) parachute.

My ideas so far:

1. Can I buy an Estes D12-14 motor? I can't find that on their motor chart or web site. Can you? But, for real, a D12-7's casing looks pretty full already.

2. The Jolly Logic Chute Release is not really the right solution because then I have a bound-up parachute wagging around on a 80 mph ascent. I'd like the rocket to continue to be aerodynamic until after apogee.

3. Adding an A (somehow?) after the D12-7 doesn't seem to be enough because those delays are only 3 seconds, and how would the A's thrust not damage the rocket?

4. The safest seems to be redesign or adapt the top stage to use a C6-7 to shave Max Speed (perish the thought!) and end up slower at ejection, but I'd guess that lowers the apogee too. I can check OpenRocket. (My rocket is too fast?!?)

5. Is there a Zero0-7 motor? Something with zero impulse, zero thrust, and a 7 second delay? I could tape that on top of the D12-7 maybe?

(5a. Carefully cleave a D12-7 into a D12-0 and a Zero0-7? Any tips?)

6. Is there electronics that fit a BT-50 LPR that will cause this kind of extra delay? But even if I did that would add weight, lowering apogee.

Any other ideas? Thanks in advance.
 
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rharshberger

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#6 is your best option, there is no D12 with a delay longer than 7 seconds in a Black Powder motor. Eggtimer Quark, Bear Altaduino(iirc), and possibly the forthcoming Flight Sketch Deployment altimeter fit in BT50 tubes, then you dont have to worry about a delay length.
 

Nytrunner

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6. Is there electronics that fit a BT-50 LPR that will cause this kind of extra delay? But even if I did that would add weight, lowering apogee.
Look up the Eggtimer quark. electronics and battery will add a tad bit of weight though
 

KennB

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Go with a plugged upper stage and an Eggtimer Quark. It'll deploy at apogee regardless of motor delay. It'll just fit in a BT-50.
The D11P with electronic deployment would be a good solution for your current design or your future 3-stage.

Another challenge would be to design an upper stage that would hit apogee with that seven second delay.
 

heada

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Sometimes added mass will actually increase apogee rather than decrease it. If your rocket is under optimized mass, adding an electronics bay with deployment controller could result in a higher flight.
 

n27sb

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The D11P with electronic deployment would be a good solution for your current design or your future 3-stage.
I agree with this solution. Plus it is a good way to get started in more advanced skills.
The Quark is cheap and easy to build.
 

DaugerDude

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I appreciate the answers about the Eggtimer Quark. That seems like a very compact and effective device. Thanks for that.

I have zero experience with HPR, but it seems like the usual method in HPR for such a device to cause ejection of the nose cone and drogue involves pyro, like loading a measured amount of black powder into something, which is lit by an ematch or starter. When I Google this, the low-weight DIY solutions I see are reusing shell casings and directly handling black powder. I'm in Southern California and I don't know anyone with used casings or guns, and I don't have experience directly handling black powder.

Is there a non-pyro way to fill the gap between the Quark and pushing out the nose cone and drogue? Has the state of this art advanced beyond this 2-year-old discussion about using a solenoid or releasing a spring?:

I think I'm okay with using ematches, such as to melt fishing line to release the spring or free the chute. Thanks again!
 

steveh.jae

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I appreciate the answers about the Eggtimer Quark. That seems like a very compact and effective device. Thanks for that.

I have zero experience with HPR, but it seems like the usual method in HPR for such a device to cause ejection of the nose cone and drogue involves pyro, like loading a measured amount of black powder into something, which is lit by an ematch or starter. When I Google this, the low-weight DIY solutions I see are reusing shell casings and directly handling black powder. I'm in Southern California and I don't know anyone with used casings or guns, and I don't have experience directly handling black powder.

Is there a non-pyro way to fill the gap between the Quark and pushing out the nose cone and drogue? Has the state of this art advanced beyond this 2-year-old discussion about using a solenoid or releasing a spring?:

I think I'm okay with using ematches, such as to melt fishing line to release the spring or free the chute. Thanks again!
Consider centerfuge vials
 

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JohnCoker

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Is there a non-pyro way to fill the gap between the Quark and pushing out the nose cone and drogue?
There has been some FUD spread about "pyro ejection", but that's the same mechanism used by motor delays. Springs and solenoids are likely going to be too bulky or heavy for a small rocket so I think a standard ejection charge is going to be your best bet.

It has become hard to get black powder in California, so your best bet is to ask at a launch. (You don't need anything else related to antique firearms.)
 

jadebox

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Instead of an altimeter you could use a small timer. Not sure, however, if you will find one smaller than the Quark.

And ... just kind of thinking out loud ... To avoid needing an altimeter/timer and having to acquire black powder, you could just add a fourth stage using a smaller motor. :)
 

n27sb

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There has been some FUD spread about "pyro ejection", but that's the same mechanism used by motor delays.
I agree John. If you are going to electronically ignite BP rocket motors you are already in the Party. The same discipline applies.
 

BABAR

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What is your goal?
If it is maximum altitude, you are gonna need to go with electronics. Keep your field size in mind, however, you need to land the sustainer in the launch area and be able to find it. The latter is greatly aided with electronic telemetry.

If the goal is simply to successfully launch and recover a two or three stage rocket, and you DON’T want to go the electronic route, you need to pick the right motors.

easiest is the sustainer. Put in an adapter and go down as low as an A8-5 or B6-6. A three stage low power rocket is likely near limit of visual range anyway by the time sustainer lights (aside from staged saucers, but that’s not what you’re talking so far.)

If you go three stage, consider downing the second booster motor to a c11-0 or even put in an adapter and see how it sims with C6 or B6 or A8.

Toughest is the first stage. I am more cautious about down powering the first stage as it has to get the stack up to speed before it leaves the rail. Multistagers tend to weathercock and be very draggy in full stack position, so you may not be able to down power the lowest booster section.

Staging just for staging is a lot of fun. For the most part, if you are really after maximum ALTITUDE you are better off with a single stage and a bigger motor. For me, for sustainers or three stagers, going anything over the minimum I can get away with on the sustainer and second booster only means a longer walk and possibly a Nonrecoverable rocket. Or worse, since black powder staging (which I love) has no tilt or altitude or velocity lockouts, a non vertical staging event. You NEVER want that to happen, but if it does, I would much rather have a smaller than a larger motor.

Just food for thought. Other options to “slow down” the rocket include draggy fin designs. Apogee’s SloMo is an extreme example.
 

sl98

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When I Google this, the low-weight DIY solutions I see are reusing shell casings and directly handling black powder

In addition to vials, small plastic caps from AT reloads are a low weight solution and will fit in a small body tube. If you don't fly reloads, you can probably pick up a handful off the ground at your next launch. I use these in my 24mm with a Quark. I've also seen people cut off fingertips of disposable nitrile gloves.

With a Quark and small 1s Lipo you won't add too much weight. You should be able to stay under 28g. The new Flightsketch may also be a great option. Here are a couple of threads to explore regarding LPR dual deploy if you decide to go this route. I'm sure there are more.

 

rharshberger

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Instead of an altimeter you could use a small timer. Not sure, however, if you will find one smaller than the Quark.

And ... just kind of thinking out loud ... To avoid needing an altimeter/timer and having to acquire black powder, you could just add a fourth stage using a smaller motor. :)
Even then a Quark needs to be built with a 24mm tube in mind, that means no terminal block option perpendicular to the board (normal position), it would need to be either deleted or something like wire wrap posts used for ematch connection or even a terminal block attached 90° from normal. Space in a BT50 coupler is tight, a Turnigy NanoTech 180mah 2S lipo and Quark leave about a 1/2" "extra" length in a 4" long coupler. 20200628_183953.jpg
 

n27sb

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You would be amazed what you can fit in 24mm. Working on this assembly this morning. Eggfinder GPS Mini and Altos Easy Mini.
Notice the terminals and screw switches. The components will be soldered to the board.

IMG_7766.JPGIMG_7767.JPGIMG_7768.JPGIMG_7769.JPGIMG_7770.JPG
 

lakeroadster

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5. Is there a Zero0-7 motor? Something with zero impulse, zero thrust, and a 7 second delay? I could tape that on top of the D12-7 maybe?

(5a. Carefully cleave a D12-7 into a D12-0 and a Zero0-7? Any tips?)
If you modify a motor.. that's verboten per NAR / tripoli rules...... but.....

How about a 4th motor, pushed up into the body such that the krushnic effect nullifies it's thrust?

Still use your D12-7, put a tiny pinch of gun powder between it and the "coasting motor". The ejection charge will light, the coasting motor will burn, then smoke, then eject the laundry. Pick whichever motor has the combination of burn / delay that combined with your 7 second D12 gives you the overall coasting time your after.
 
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jadebox

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How about a 4th motor, pushed up into the body such that the krushnic effect nullifies it's thrust?
In my previous reply, I suggested adding a fourth stage. I almost put "fourth stage" in quotes because I was considering the idea of having the third stage motor ignite a motor above it without separating the stage. The upper motor will fire through the expended third-stage motor so it won't produce much thrust.
 

Kelly

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Notice the terminals and screw switches.
Steve, the metal standoffs on the frontside of the board that make up part of the screw switch - do you fabricate these yourself, can you describe how?
Also, are you cutting threads into the G10, how durable is that?
 

n27sb

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Steve, the metal standoffs on the frontside of the board that make up part of the screw switch - do you fabricate these yourself, can you describe how?
Also, are you cutting threads into the G10, how durable is that?
Kelly if you go to post #34 on this thread I did a breakdown
.

The trick is to use a flat lead from a transistor that is wider than the hole. If it does not have a point on it then make one with your nippers. That way after you solder it in place pressure from the screw can not push it through the hole.
Slightly bend the leads in and cut off at about a 1/4" long. I use a tiny file to groom the top contact area.
Any time you apply heat from the underside make sure that a screw is in contact or the leads will drop out.
The harder you tighten them the more it will force the leads to the middle of the screw.
BTW I use a4-40 button head screw. You do have to drill a very precise hole in one of the existing holes.

I have never had the threads fail. Use the right size tap drill or 1 number smaller (number size drills).
If you are a Gorilla Grip, put a generous blob of epoxy (not JB metal) underneath after everything is soldered and re-drill and tap.

IMG_7774.JPG IMG_7775.JPG
This is the finished board. Note that the two screw switches can be accessed by withdrawing the nose cone about 3/4" before flight. I have not drilled those access holes yet. finished weight is 39g. The holes on the bulkhead will be filled with epoxy.
 

Kelly

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Kelly if you go to post #34 on this thread I did a breakdown
Thanks! I make mine from double-clad PC board and a soldered-on nut, but yours looks like an interesting variation I may try.
 

DaveW6DPS

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I appreciate the answers about the Eggtimer Quark. That seems like a very compact and effective device. Thanks for that.

...I'm in Southern California and I don't know anyone with used casings or guns, and I don't have experience directly handling black powder...

I think I'm okay with using ematches, such as to melt fishing line to release the spring or free the chute. Thanks again!
If you ever get to a ROC launch (if we ever get to launch again) I can help you out with all of the above. I even have an Eggtimer Quark to demonstrate.
 

lakeroadster

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In my previous reply, I suggested adding a fourth stage. I almost put "fourth stage" in quotes because I was considering the idea of having the third stage motor ignite a motor above it without separating the stage. The upper motor will fire through the expended third-stage motor so it won't produce much thrust.
I tried that once back in high school... about 4 decades ago. The thrust burns a hole through the side of the motor to motor interface, and sends the rocket into a horizontal spin, as well as torching the rocket.

You want the spent casing to separate.
 
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