Looking for a wire recommendation

[Swissyhawk]

I'm about to install the motor mount in the upper stage of my Double Shot. I have a 3/16" steel brake line that is about 2 feet long. I wanted to install the wire before I glued the motor mount in the body tube. I don't really know much about wire so I ordered some off of Amazon.

https://www.amazon.com/gp/product/B07D3MVRMR/?tag=skimlinks_replacement-20

I thought it would be a good choice because it said it was high temperature resistant. The problem is that it is super flexible. I can't get it to pass through the brake line. The only other wire that I've ever used is from the Dog House Rocketry wiring kits. Those wires are stiffer and I can pass them into the brake line, they just aren't long enough.

I'd appreciate any recommendations on a particular wire to use for this application.

Thanks.

View media item 346406

 

[ttabbal]

That wire is a nice wire to use. I suggest you use a piece of music wire as a fish tape and pull the flexible wire through. You can also tie a small weight to some string or fishing line and use that to pull the wire.

 

[tim cubbedge]

The wire is most 2 stage rockets is really only a single use. Need to thread new wire before each flight. I have been using this stuff from Quick Burst which threads pretty easy.
https://www.quickburst.net/26awg_shoterwire.htm

 

[Swissyhawk]

Ttabbal - I’ll try pulling it through with some fishing line. That sounds like a good idea.

Tim - What makes the wire single use? I bought a quick disconnect from adept rocketry for the break point when the drogue charge goes off and I was thinking of taping the wire to the inside of the body tube where it comes out of the fore end of the brake line. Does the aft end of the wire usually burn up from the motor?

 

[tim cubbedge]

I make break-wire connections at both the altimeter end and at motor end where I connect to igniter. One or the other always breaks but on occasion, the connection at the igniter seems to go first and the whole wire gets pulled out of airframe at apogee. Plus the wire I use is not rated for very high temps. With small enough wire, it is easy to feed thru the 3/16" brake line. I also have the assurance that wire is in good shape before each flight. Yes, the after end wire tends to get burnt up a bit too since I cut my igniters really short and make the connection right at the nozzle.

 

[blackjack2564]

I've been doing 2-stagers quite awhile now, I always fish a new e-match through my 3/16 brake line. Every time, fewer connections to malfunction this way.
Before first use, squirt some WD-40 into the brake line, makes it nice and slippery , to ease in wire. Also keeps interior of conduit from corroding due to nature of motor burn residue getting inside.....which it will!
3/16 has plenty large I.D. for easy insertion of any E-match wire I have ever used.

CJ tip:
Leave the "knob" on one end of brake line & run it to the edge of motor retainer.
That make it close enough to easily insert wire....the knob acts like a guide to help you get wire centered.



After retainer is glued on and ready for final fit....the line is slid into position over retainer mount glued on tube, right to edge where the screw cap seats. This make inserting wire very easy for you, where as the rookies alway place end of line back at CR...where it's impossible to reach with out a wire fish. Leave a 1/4 in. space from end of conduit to cap, for wire to go around cap into nozzle


If you are set on doing it your way.....use e-match wire, it is plenty stiff to fish though the tube.
Cut a 45 angle on end going through...remember a spritz of WD-40..makes this so much easier.
Good luck & have fun!

 

[Swissyhawk]

Jim, thanks for the detailed reply. I don’t have a picture handy, but if I ran my brake line down to the motor retainer, it would interfere with the ISC. I wouldn’t be able to slide the ISC up into the body tube of the 2nd stage. How does it work on that rocket you have shown?

 

[blackjack2564]

The rocket shown above is a 3inch Wildman 2-stage. Flown many, many times, never an issue with the I/S. had 54mm motor mount.

This is the 54mm Airframe with 38mm motor mount from 2-stage Vindicator.
Yes it required careful thought and keeping the conduit right down on MM so the coupler would clear.
If you drilled holes through the CR's in wrong place, yes the coupler would bind or not go in at all. Holes were on low side of center. Some just notch the inner side of Cr.
There is no knob on this conduit as it's a cut off from the original 4 footer.





There are/were no issues with this one & many I have mentored doing, you can see there is room for a coupler by how far from edge of CR the conduit is.



Your sustainer is same as this one 54 airframe & 38 motor, should work just fine.
2-stagers are not twice as hard...they are 10 times harder than single stage!!!!@#@

 

[OverTheTop]

If you are trying to get a flexible wire or string through a conduit you can actually blow it through with compressed air. The faster flow through the center of the tube tends to pull the wire towards the middle of the tubing, thus reducing friction, and pulling the wire along too
https://en.wikipedia.org/wiki/Bernoulli's_principle

 

[Swissyhawk]

where as the rookies always place end of line back at CR...

Yeap, I definitely made the rookie mistake. My brake line end is flush with the CR.

Your sustainer is same as this one 54 airframe & 38 motor, should work just fine.

When I was trying to figure out how this was going to work, I was eyeballing it and I thought there was no way there would be room for the brake line aft of the last CR. So tonight I flipped my fully assembled motor mount assembly around and inserted it into the body tube backwards as a temporary test (so now the "front" of the brake line sticks out the aft end) and then I slid the coupler into the body tube and guess what, it fit just fine. The walls of the coupler aren't actually as thick as I thought were.

2-stagers are not twice as hard...they are 10 times harder than single stage!!!!@#@

I couldn't agree more!

Thanks Jim for posting those pictures.

 

[blackjack2564]

Your welcome.
I take it you have glued in the conduit?
Maybe you can run another one on other side of MM CR & cut the old one flush. Or....
I have removed bad ones by grabbing with lock gripe pliers and giving a sharp quick twisting motion to break it free from glue. After using a dremel to remove as much glue as possible.
Another method is to cut notch around the CR/conduit joint and remove, just replace with new, in same notches. A bit of ingenuity will get you there.
If at all possible fix it now, or drive yourself nutz later!