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Airstarts - how do you wire yours?

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75Grandville

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I've got two cluster rockets in the works - one's a LOC Ultimate, and one is a LOC Cruiser clone using their new 54mm + 8 x 29mm cluster rings.

I want to be able to perform airstarts. I am not worried about the electronics side of things. What I am trying to figure out is the best way to wire these up - that is to get the wires from the electronics (RRC3's) to motors to actually ignite them.

Do people generally
  • Build a lower electronics compartment to house airstart altimeters, with a hatch?
  • Have some clever way of running wires from the AVbay down to the motors that won't interfere with the ejection process?
  • Just attach the AV bay to the sustainer, run wires down to the motors, and use a cable cutter?

Or something I've not thought about. I know there are folks out there who do this successfully on a regular basis - would prefer to learn from their experience rather than my own mistakes.:)

Pictures would be greatly appreciated!
 
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FredA

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MARSA-NET....no wires needed....especially if doing HEI.
 

soopirV

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I've seen some great ideas involving lamp rod (hollow threaded rod). Run that down through your CRs and you can fish your ematch through AND retain some motors at the same time! There's a picture here somewhere...can't quite recall who did it first, but I filed that away for if/when I get into HPR clusters.
 

new2hpr

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Lamp rod is heavy. Go to a kite store and get some fiberglass or carbon tubing.
I prefer the hatch method for the airstart timer. I just made that compartment between the 2nd CR (top of fins) and 3rd CR (top of MM). Plumb the conduit from the 1st CR to 2nd CR and you can fish the ematch leads through very easily. A single conduit can carry multiple airstart ematches, and is easier to fish them through to the timer.

I've got more photos in my bucket:
-KenP1050539.jpg
 

soopirV

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Lamp rod is heavy. Go to a kite store and get some fiberglass or carbon tubing.
I prefer the hatch method for the airstart timer. I just made that compartment between the 2nd CR (top of fins) and 3rd CR (top of MM). Plumb the conduit from the 1st CR to 2nd CR and you can fish the ematch leads through very easily. A single conduit can carry multiple airstart ematches, and is easier to fish them through to the timer.

I've got more photos in my bucket:
-KenView attachment 310221
very clean looking, like how you built the multiple match adapter...filing that (and the carbon rod idea) away too!
 

BDB

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I've been thinking of this same thing lately for HPR 2-stage. Assuming I don't opt for a hatch or HEI, is there a way to run a wire from the avionics bay to the igniter and then have it beak at deployment? Or will the dangling igniter just shred and make this a moot point?
 
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75Grandville

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I've been thinking of this same thing lately for HPR 2-stage. Assuming I don't opt for a hatch or HEI, is there a way ti run a wire from the avionics bay to the igniter and then have it beak at deployment? Or will the dangling igniter just shred and make this a moot point?
That's some of what I was asking about. I had visions of the igniter wire hanging, and the drogue not deploying properly
 

75Grandville

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Lamp rod is heavy. Go to a kite store and get some fiberglass or carbon tubing.
I prefer the hatch method for the airstart timer. I just made that compartment between the 2nd CR (top of fins) and 3rd CR (top of MM). Plumb the conduit from the 1st CR to 2nd CR and you can fish the ematch leads through very easily. A single conduit can carry multiple airstart ematches, and is easier to fish them through to the timer.

I've got more photos in my bucket:
-KenView attachment 310221
This is exactly what I was thinking/wondering about. Thank you! Where can I find your bucket? Do you have a build thread detailing how you created that cool hatch?
 

FredA

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I've crossed the drogue bay two ways when using wires:
1 - used a "Deans" connector that gets pulled apart upon deployment.
2 - used 30-gauge wire-wrap wire to cross the bay then used an "amplifier" with it's own power source to take the "light now" signal provided over the thin wire and "amplify" it to provide the power to light multiple motors. "Amplifier" in this case is a representative term to give you an idea of functionality....really just a self-designed high power switch with an opto-isolator input to provide isolated and polarity-agnostic input. The thin wires break upon deployment.
 
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BDB

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Are Dean connectors preferred for this? I've never used them, and I have a bunch of JST and XT60 connectors.
 

FredA

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"Dean" connectors are good connectors for transferring a few amps of current, pull apart pretty easily, and are available at most hobby shops. So they are basically convenient, quality connectors that do well under vibration yet pull apart fairly easily.

You can use almost anything that comes apart easily.
Current carrying isn't that important - although current is in the 4A ballpark, the duration is really short
 

patelldp

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I am in the process of building my LOC Ultimate's altimeter bay and will soon have pictures to share. For mine, I installed a phenolic conduit the entire length of the motor mounts to allow me to pass wires from the drogue bay to the rear of the rocket. I will use standard single strand copper wire, about 22ga for this run, one pair per channel. At the tail of the rocket, the 22ga wire will be twisted together with my igniters (e-matches, in this case) and then taped or have heat shrink tubing applied to make a robust connection.

At the altimeter bay side there will be a set of small pigtails attached to my terminal blocks. These will be twisted together with their associated wires that run to the back of the rocket. I only twist these 2-3 turns so they are a positive contact but not strong. A light application of electrical tape is applied to prevent shorting. At deployment, this is the connection that breaks.

I have had a lot of success with this method on my two stage rocket. It's a 29mm to 29mm rocket based on LOC 54mm tubing so there isn't a lot of room. There has been zero tangling thus far, and if you're interested I'd be happy to share some pictures this evening or this weekend to show how I do it.

Here's the back end of my Ultimate. The three holes in the G10 retainer allow me to route air-start wires under the plate to protect them from the motor exhaust.

 

Steve Shannon

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I am in the process of building my LOC Ultimate's altimeter bay and will soon have pictures to share. For mine, I installed a phenolic conduit the entire length of the motor mounts to allow me to pass wires from the drogue bay to the rear of the rocket. I will use standard single strand copper wire, about 22ga for this run, one pair per channel. At the tail of the rocket, the 22ga wire will be twisted together with my igniters (e-matches, in this case) and then taped or have heat shrink tubing applied to make a robust connection.

At the altimeter bay side there will be a set of small pigtails attached to my terminal blocks. These will be twisted together with their associated wires that run to the back of the rocket. I only twist these 2-3 turns so they are a positive contact but not strong. A light application of electrical tape is applied to prevent shorting. At deployment, this is the connection that breaks.

I have had a lot of success with this method on my two stage rocket. It's a 29mm to 29mm rocket based on LOC 54mm tubing so there isn't a lot of room. There has been zero tangling thus far, and if you're interested I'd be happy to share some pictures this evening or this weekend to show how I do it.

Here's the back end of my Ultimate. The three holes in the G10 retainer allow me to route air-start wires under the plate to protect them from the motor exhaust.

When you say "single strand" I assume you mean solid wire for your run along the motor mount. Unless you intend to replace that run every flight I would recommend running stranded wire. Solid copper wire fails easily as it work hardens and then breaks due to vibration.
If single strand means a single run of stranded wire, then I retract my suggestion.


Steve Shannon
 

patelldp

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When you say "single strand" I assume you mean solid wire for your run along the motor mount. Unless you intend to replace that run every flight I would recommend running stranded wire. Solid copper wire fails easily as it work hardens and then breaks due to vibration.
If single strand means a single run of stranded wire, then I retract my suggestion.


Steve Shannon
Solid wire, replaced every flight.
 

FredA

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Note - I'm not kidding about MARSA-NET and HEI.
This become SUPER EASY.
You just put a MrfPyro and battery at the top of the motor and YOU ARE DONE.

No worries about how to cross the drogue bay and not tangle a chute.
And with HEI, no Conduit and no Wires down in the flames (yes, I've lost and airstart because the central motor baked the wire)
 

new2hpr

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This is exactly what I was thinking/wondering about. Thank you! Where can I find your bucket? Do you have a build thread detailing how you created that cool hatch?
https://s424.photobucket.com/user/new2hpr/library/Rocketry/Excess%20In%20Moderation?sort=6&page=1

Sorry, not much build-thread-wise. Since it is LOC cardboard airframe, I drew the rectangle for the hatch and carefully (many passes) cut it out with an xacto knife, with slightly radiused corners. Save the removed piece. Next, I epoxied a section of coupler tubing, just an arc, not the full circle, into the airframe, backing the hole just cut. Mark a smaller rectangle inside the original cut by maybe 1/4" or so, and leave extra material in corners and long edges for rivet holes. Cut out the smaller rectangle from the coupler section. Now you have a hatch hole with retainer ledge for the hatch. I just epoxied the sled to the motor mount tube, making sure I had room for the timer to fit within the airframe. Put the removed hatch section over the hole and match drill for rivets (or screws or whatever). Solidify all parts with a good CA soaking and it has held up quite well.

The multi-ematch breakout board was just a bunch of terminal blocks shorted together on the back of some perfboard. One row does the + side, the other -, and then just 2 wires up to timer. Fitting multiple wires into a single screw terminal is just asking for trouble.

-Ken
 

James Donald

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The end of my Minfluous video on YouTube shows my interstage coupler and head end ignition technique. I am now using a pyrodex pellet wrapped with one layer of packing tape instead of a pyrogen dipped igniter.

[video=youtube;1eIChi3Bbgo]https://www.youtube.com/watch?v=1eIChi3Bbgo[/video]

This is the same configuration I used for the third launch that went to 110K. Except I used a TeleMega with 20deg lockout instead of the Raven to light the second stage.

James Donald
 
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BDB

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The end of my Minfluous video on YouTube shows my interstage coupler and head end ignition technique. I am now using a pyrodex pellet wrapped with one layer of packing tape instead of a pyrogen dipped igniter.

[video=youtube;1eIChi3Bbgo]https://www.youtube.com/watch?v=1eIChi3Bbgo[/video]

This is the same configuration I used for the third launch that went to 110K. Except I used a TeleMega with 20deg lockout instead of the Raven to light the second stage.

James Donald
That was an incredible flight! More inspiration for me to pursue HPR 2-staging this year.
 

AHansom

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I feed the wires from the AV bay through a piece of carbon fiber arrow that exits under the aluminum plate that holds the motors in. The plate also helps protect the air start wires form getting burnt

avbay3.JPG


avbay2.jpg


avbay1.JPG


Thumper.jpg


thumper1.JPG
 
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75Grandville

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Wanted to thank those that provided their input.

Here's my AVBay, in process

IMG_3227.jpg

I used four carbon fiber tubes to route wiring down to the base. C channel to hold the sled(s). Going to hold a pair of RRC3's.
 

Viperfixr

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I wonder when the Aerotech Head-End Ignition will come out?
 

NateLowrie

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Fred,

I am assuming your doing HEI on EX motors? Care to share the forward bulkhead design?
 

FredA

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I am assuming your doing HEI on EX motors? Care to share the forward bulkhead design?

Yes and my design is super simple and has never failed - have used on motors from 38->75mm and up to 1.2kPSI with burn times up to 14 seconds.

What I do is this:
- Drill and tap a 1/4-20 hole though the center of the forward closure.
- Using a lathe - I drill a hole down the center of a 1/4-20 hex-head 3/4-inch long bolt. Diameter of the hole just large enough to pass the wire for the ematch.
- Swap out the drill bit for a slightly larger bit and drill about 1/8th-inch deep in to the head side hole enlarging it.
- Thread one or two pyrodex pellets onto a match and thread the match though the 1/4-20 bolt. Match head on the bolt-head side leaving sufficient length on the match-head side to position the pyrodex in the center of the top grain..
- Using JB-Weld epoxy the e-match into the bolt head stuffing the holes full and let cure.
- Thread the above bolt/match assembly into the forward closure using a little grease - the bolt head fitting into the top of the motor core.

I usually use a solid top grain, but can't when I do this.
I have made variations on this that do allow a solid top grain or smoke grain, but it becomes more of a PITA to assemble.

I have also done this off center and with 10-32HW although that gets pretty thin-walled when drilling for standard shooters wire to pass.

And yes, the motor is "Hot" from assembly time on. If this is a concern, leave the forward closure off as long as possible.
Twist the leads on the e-match in a drill prior to insertion so that the leads are a twisted pair.
Strip and short the match until it is wired into the rocket.
Use Double-Throw (DT) switch(es) in the rocket to disconnect and shunt the e-match in the motor.

I've also done this with the bolt head on the forward side of the closure with larger bolts and a slipping the e-match head though a larger hole in the forward closures - this allows for late arming, but does not allow you to use any augmentation on the e-match head.
 
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NateLowrie

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I am assuming your doing HEI on EX motors? Care to share the forward bulkhead design?

Yes and my design is super simple and has never failed - have used on motors from 38->75mm and up to 1.2kPSI with burn times up to 14 seconds.

What I do is this:
- Drill and tap a 1/4-20 hole though the center of the forward closure.
- Using a lathe - I drill a hole down the center of a 1/4-20 hex-head 3/4-inch long bolt. Diameter of the hole just large enough to pass the wire for the ematch.
- Swap out the drill bit for a slightly larger bit and drill about 1/8th-inch deep in to the head side hole enlarging it.
- Thread one or two pyrodex pellets onto a match and thread the match though the 1/4-20 bolt. Match head on the bolt-head side leaving sufficient length on the match-head side to position the pyrodex in the center of the top grain..
- Using JB-Weld epoxy the e-match into the bolt head stuffing the holes full and let cure.
- Thread the above bolt/match assembly into the forward closure using a little grease - the bolt head fitting into the top of the motor core.

I usually use a solid top grain, but can't when I do this.
I have made variations on this that do allow a solid top grain or smoke grain, but it becomes more of a PITA to assemble.

I have also done this off center and with 10-32HW although that gets pretty thin-walled when drilling for standard shooters wire to pass.

And yes, the motor is "Hot" from assembly time on. If this is a concern, leave the forward closure off as long as possible.
Twist the leads on the e-match in a drill prior to insertion so that the leads are a twisted pair.
Strip and short the match until it is wired into the rocket.
Use Double-Throw (DT) switch(es) in the rocket to disconnect and shunt the e-match in the motor.

I've also done this with the bolt head on the forward side of the closure with larger bolts and a slipping the e-match head though a larger hole in the forward closures - this allows for late arming, but does not allow you to use any augmentation on the e-match head.
Thanks Fred. That is dead simple. I am filing this away for later.
 
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