"breakaway" bulkhead terminal for airstart?

the model rocket show
Onebadhawk
madcow rocketry
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Faroutspacenut

Faroutspacenut

Member
TRF Supporter
Joined
Feb 22, 2017
Messages
191
Reaction score
18
The build on my first 2-stage project is now complete except for the electronics. This is a LOC Sandhawk 2.6" (38mm) on top of a 3" Terrier Booster.

For the sustainer, I'll be running an extra long e-match from the motor through a piece of brass tubing in the centering rings that then attaches directly to the aft bulkplate of the av bay. I would want this wire to "break away" when the apogee separation occurs. Any suggestions? Is a regular screw-type terminal block going to have too much hold? Are there any spring-loaded kinds that are reliable? Any suggestions would be appreciated.
 
I use JST connector, ones that Lipo batteries use.
I cut down the female units cap so it will come apart a bit easier, but remain snug enough not to fail. See pic of reg unit next to cut down.
Small bays, just run wire direct to altimeter and knot wire on back side of Bp for strain relief. Consider these expendable.
Easily cut with X-acto or razor blade/Dremel etc.

Larger bays have terminal blocks and I attach to those. You must solder the match to male side of JST.

DSCN1299.jpg DSCN1300.jpg DSCN1305.jpg DSCN4866.jpg
 
A screw type terminal will not break away. The only method I can think of that would qualify for break away would be twist and tape which still might not allow break away depending on specific setup.
 
Brian H. said:
A screw type terminal will not break away.
Click to expand...
You can get screw-type terminals that are separable.Phoenix Terminals make them, and I have used them on my Nike Smoke:

UpperDepolyment.JPG

The screw terminal side is separable from the other side (which is normally PCB mount). The one you can see on the left disconnects when the NC parts company.
 
Good 'ol wire-wrap works fine. I tin the end of the wires coming out of the bulkhead, and wrap the ematch (or an extension) wires twice around the tinned end (don't twist them!). I cover the bare ends separately with a short piece of 1/8 launch lug, and tape them to the igniter wire. Good contact, and it disconnects readily when the drogue fires.
 
I use JST connectors for this. I just sand the tab off so the two components slide apart relatively easily.
 
timbucktoo said:
I use the method Jim Jarvis describes in this thread:
https://www.rocketryforum.com/threads/quantum-leap.18469/page-2#post-167160
Click to expand...

I have used that breakwire method for years and it works quite well. For an upcoming flight, though, I will have 5 pairs of wires coming from the nose cone with a total of 6 breakwires required. So, I thought I would try something different, such that all of the connections could be made a little more quickly. I got the fittings below. I have to sand the prongs, but by doing that, I get a nice snug fit that pulls apart pretty easily. The bundle below will fly shortly, so we'll see how they work.

Jim

IMG_1941.JPG
 
blackjack2564 said:
I use JST connector, ones that Lipo batteries use.
I cut down the female units cap so it will come apart a bit easier, but remain snug enough not to fail. See pic of reg unit next to cut down.
Small bays, just run wire direct to altimeter and knot wire on back side of Bp for strain relief. Consider these expendable.
Easily cut with X-acto or razor blade/Dremel etc.

Larger bays have terminal blocks and I attach to those. You must solder the match to male side of JST.

View attachment 383663 View attachment 383664 View attachment 383665 View attachment 383666
Click to expand...
Since most of the jst connectors I continue to stupidly rely on to stay together rarely do, I'd say that's a safe route;)
 
Faroutspacenut said:
The build on my first 2-stage project is now complete except for the electronics. This is a LOC Sandhawk 2.6" (38mm) on top of a 3" Terrier Booster.

For the sustainer, I'll be running an extra long e-match from the motor through a piece of brass tubing in the centering rings that then attaches directly to the aft bulkplate of the av bay. I would want this wire to "break away" when the apogee separation occurs. Any suggestions? Is a regular screw-type terminal block going to have too much hold? Are there any spring-loaded kinds that are reliable? Any suggestions would be appreciated.
Click to expand...

Have your flown Terrier-Sandhawk yet? I just bought the same two kits.
 
Cameron Anderson said:
Have your flown Terrier-Sandhawk yet? I just bought the same two kits.
Click to expand...

I was planning on doing my first test flight on the last day of NSL, but the wind got fierce and it was no go for launch. Possibly this Saturday. Keep us posted on your build and flights (maybe we should start a thread on this combo)
 
I'm down for a new threat. Due to shipping mishandling the fin-end if my Terrier airframe was crushed. I emailed Loc and they rushed one out to me (gotta love their customer service). Anyway, I opened it today and noticed the interstage was dramatically different than I anticipated so I'll need to figure out how I'm going to proceed.

Did You solve your break away terminal problem?
 
I'm going to crimp a JST connector on the end of my e-match and have that connect to a wire coming through the bulkhead. At least that's the plan. I have a good crimping tool and the connectors but still haven't quite mastered making a good connection.
 
Hybrid33 said:
Do you know the part # ?
Click to expand...
I don't know my specific part number. Probably purchased it from Element 14 in Australia. If you are really keen you can have a look around www.phoenixcontact.com to find a part.

Digikey have a good range of similar products, but seem to be lacking Phoenix as a supplier:
https://www.digikey.com/products/en/connectors-interconnects/terminal-blocks-headers-plugs-and-sockets/370?k=terminal block pluggable
I am sure the other products would be similarly suitable.

I think mine were 5.08mm pitch, but the smaller pitches would be suitable also.

If you want to keep the terminals a little better protected from ejection gases (BP residue is quite corrosive) you can apply some Electrolube CG53 contact grease to the connectors.
 
Last edited:
Cameron Anderson said:
Did you ever fly your Terrier Sandhawk?
Click to expand...
Going to try this weekend. Relating to the post topic, I've decided to keep it simple with some hookup wire from the altimeter thru the bulkhead (a knot on the inside) of which I've tinned the ends of. Then I'll wrap the e-match around each lead and secure with painters tape. Did an ejection test today and it pulled apart just fine.
 
Brian H. said:
A screw type terminal will not break away. The only method I can think of that would qualify for break away would be twist and tape which still might not allow break away depending on specific setup.
Click to expand...
I use twist & tape. The one time the wire didn't separate at that point, it pulled the ematch out at apogee. No issues (flying a fiberglass 3" Wildman 2 stage, several times the weight of the LOC 3" Terrier booster kits).
 

Similar threads

N
Premature Drogue Chute Deployment Diagnosis
Replies
7
Views
296
cwbullet
cwbullet
S
2-Stage MPR class 1?
Replies
5
Views
728
waltr
W
eJar0k
RIM-2 Terrier 29/38mm
Replies
9
Views
2K
Rocketclar
Rocketclar
S
First Time AV-bay construction Thread
2
Replies
56
Views
4K
Handeman
Handeman
L
Issues with RRC2+ & Easy Mini
Replies
0
Views
644
LogicPenguins
L

Latest posts

Back
Top