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cbwho

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With winter approaching, how cold can I fire Q-Jet motors? Hoping to launch from frozen lakes on sunny days
 

Tractionengines

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They will fire, but you will lose some thrust from slightly slower burning. Hopefully Mr Aerotech can give us an idea % reduction in performance at say 0C, -20C, -40C. (-40 is the point °C & °F are equal)

The bigger issue us making sure your recovery system works.
*Nosecone fit changes a lot as the cardboard tubes vs plastic nosecone expand and contract at different rates.
* parachute material doesn't flex as well.
* Landing on a frozen lake is like landing on concrete, keep decent velocities down.

One final note, any breeze that can catch the chute/streamer will drag the rocket across the ice till it gets to the far shore... don't ask how I know...
 

AeroTech

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Here’s an example of a motor tested at three different temperatures.
F553E386-109B-41C3-9E3F-9AFB2A6D1251.png

They will fire, but you will lose some thrust from slightly slower burning. Hopefully Mr Aerotech can give us an idea % reduction in performance at say 0C, -20C, -40C. (-40 is the point °C & °F are equal)

The bigger issue us making sure your recovery system works.
*Nosecone fit changes a lot as the cardboard tubes vs plastic nosecone expand and contract at different rates.
* parachute material doesn't flex as well.
* Landing on a frozen lake is like landing on concrete, keep decent velocities down.

One final note, any breeze that can catch the chute/streamer will drag the rocket across the ice till it gets to the far shore... don't ask how I know...
 

cbwho

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-65F is a lot colder than I'd consider!
So they sound very safe down to 0F. (From the design, I would suspect so.)
I will buy the engines for winter :)

This winter it's predicted to be snowy, so the several feet thick ice will have a softer blanket of snow.

To bolster an Estes launcher, I'm thinking of bringing more batteries. I could easily add more banks. I assume I should add the additional in parallel to keep the same voltage?
Or does Aerotech offer a better launcher?
 

BEC

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....actually, battery voltage falls (as well as current capability) with decreasing temperature, so more voltage (as long as the current the battery can deliver is reasonable) would be what you want to compensate for the cold.

What launch controller do you have? FirstFire Micros that come with Q-Jets don't require a whole bunch of current (a little 9V battery controller, which can't source much current, has no trouble firing them in the spring or summer). Most anything with more capability than a little 9V controller or an Estes Electron Beam (4AAs, so six volts, but from cells that can source MUCH more current) should be good down to zero F.
 

Tractionengines

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Just had an issue today. F42-4T with a VERY SHORT delay. Motor lit and took right off, no chuff, slow light, etc. But from ignition to ejection charge was 3.2 seconds. (Per video analysis.) Needless to say chute deployment at high speed.
Burn time 1.3sec
Coast time 1.9sec
Photo shows motor code. Anyone else see this on this batch? ( 052120 )20201107_215522.jpg
 

AeroTech

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Normal variation on a 4 second delay with the 1% lot sampling is +/- 1.5 seconds, but the 3 sigma variation could be higher.

Just had an issue today. F42-4T with a VERY SHORT delay. Motor lit and took right off, no chuff, slow light, etc. But from ignition to ejection charge was 3.2 seconds. (Per video analysis.) Needless to say chute deployment at high speed.
Burn time 1.3sec
Coast time 1.9sec
Photo shows motor code. Anyone else see this on this batch? ( 052120 )View attachment 437639
 

dshmel

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Since we are on the topic of motor and environmental temperatures (in this case, launch temperature). I would like to know the tolerable temperature range for storing motor reloads and DMS motors.
 

AeroTech

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I think it’s listed in the instructions, something like 32 to 100 deg F.

Since we are on the topic of motor and environmental temperatures (in this case, launch temperature). I would like to know the tolerable temperature range for storing motor reloads and DMS motors.
 

mrwalsh85

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Folks... If you bought the Wildman tailcone closure, and was wondering why the disclaimer was on his website to not use these tailcone closures with Medusa nozzles... Here you go. This was a 75mm 2 grain white lightning load. K540 or something?? Would make a very cool paperweight!


don.jpg
 

Banzai88

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Folks... If you bought the Wildman tailcone closure, and was wondering why the disclaimer was on his website to not use these tailcone closures with Medusa nozzles... Here you go. This was a 75mm 2 grain white lightning load. K540 or something?? Would make a very cool paperweight!


View attachment 437775
That's one seriously spendy paperweight
 

Rob702Martinez

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When will AT replace the medussa nozzle with single throats? Or when will AT advise which single throat and bore we can use from the RCS store on loads with the medussa nozzle?
 

mrwalsh85

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Disclaimer: was not my flight. So I don't know what the flyer will do with the tailcone closure.
 

R3D_R0CKET839

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Can anyone help me design a rocket to 3d print? or do any of you want parts printed i use high quality filament and dont charge too much
 

AeroTech

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May I recommend you start a new thread, you will get a better response.

Can anyone help me design a rocket to 3d print? or do any of you want parts printed i use high quality filament and dont charge too much
 

rharshberger

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And of course, NO ONE would stand downwind of a high power rocket and breathe while the smoke rolls over the flight line, right? :rolleyes:
Nope....of course the flightline should downwind for safety reasons anyways from the spectators😉
 

AeroTech

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The large single throat 54mm nozzle has been used in production for nearly 20 years now. There are no 38mm Medusa nozzles.

0B6DE9C3-727B-4A71-880C-EB81F636226B.png

6CFD78E5-1C77-42FE-8C19-99EE18FB7192.png

Thanks. I saw that prior but was also inquiring about the 54mm motors. I see that is for the 75mm motors. All the 38mm motors are single throat as well, right? I've got a lot of tailcones.
 

Rob702Martinez

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Are there some 54mm relaods that still use the medussa? Or are they all single throat now. Is it possible to swap in a single throat and drill it out on a medussa load? Like the J180T etc.
 

Rocketjunkie

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I use Aerotech nozzles when I make reloads for Aerotech hardware. I calculate the single throat nozzle size (for the Kn I need). If I'm using a Medusa nozzle, then I will determine the throats. (1/2 the area in center for using 4 throats, 1/3 in center if using all 7 throats. If the single throat comes out less then about 7/16", I'll use a small hole closure and a 29 mm nozzle.
 

Rob702Martinez

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I use Aerotech nozzles when I make reloads for Aerotech hardware. I calculate the single throat nozzle size (for the Kn I need). If I'm using a Medusa nozzle, then I will determine the throats. (1/2 the area in center for using 4 throats, 1/3 in center if using all 7 throats. If the single throat comes out less then about 7/16", I'll use a small hole closure and a 29 mm nozzle.
Would you be willing to share some of your combos in PM? Are you using the RCS propellant? I keep gaining and losing interest in EX going the RMS and DMS route.
 

AeroTech

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Yes, but they use a smaller throat than 0.455".

Are there some 54mm relaods that still use the medussa? Or are they all single throat now. Is it possible to swap in a single throat and drill it out on a medussa load? Like the J180T etc.
 

DeltaVee

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Karl got back to me quickly, stating the same as post https://www.rocketryforum.com/threads/aerotech-open-thread.125657/post-2055931. The delays supplied with the motor will be +/- 1s. I appreciate the answer!

Regarding HDKs, he stated they're in compliance with a large percentage of the motors, so are not altered. So it seems YMMV more with HDKs than those supplied with the motor. I used these back before I was comfortable drilling delays, now I just get the longer delay packs and drill them with the 18-38 RMS DDT, or a drill bit with stop adjusted using a 1/32" graduated ruler.

So getting back to this.... just cant let go I guess. So you're saying you'd buy a pack of F24-7s and drill them to get say, 5 seconds. How much do you drill down? My experience with drilling delays has been quite variable. Ive drilled different depths only to have my altimeter 3 say the delay was nearly the SAME. I must be doing something wrong if this sort of thing works for you... but I have no idea what. I put the drilled end toward the propellant as many have advised me. I don't know what else there could be to this.
 

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