Concern: Terminal Blocks

[AKVP]

Hello All-

I have wanted to post something that I have discovered. In fact, I wanted to do this a long time ago but just now got up the grit to do it!

I have been building electronics bays for some time and frankly it is one of my favorite parts of a rocket build. I try to make them better, cleaner, modular-for repairs/replacements etc. and serviceable. Above all they must handle the rigors of flight as I consider them one of the most important parts of the rocket as they make the recovery SAFE and reliable. My closet is full of them....of all sizes.

After I got home from LDRS 31 I ran through my usual cleaning/inspection procedures on all my electronics bays. All my high power rockets use dual electronics and thus I have up to 4 terminal blocks per rocket for the deployment charges. I know these items are common and are seen on just about every rocket using dual deploy.

What I found during my inspections was that EVERY terminal block (even after ONE flight) and wire set going into the block (from bulkhead) was badly corroded, I mean BAD. After I removed the terminal block, I found the wires to be likewise corroded. I also found the wire (22g) to be corroded up to 2 inches down after stripping to find good clean wire!

Please also note that after each launch I clean said bulkheads, terminal blocks etc. and even have blown them off with air. But I find the level of corrosion to be alarming.

I say this because this could be a safety issue with deployments. You may get a continuity signal from your altimeter but corrosion could prevent needed current to fire a charge on an old, corroded terminal block and wire. I just see these things as having to many nooks and crannies for BP residue to get into.

I am ONLY posting this to say......just check your terminal blocks and wires...that's all. I have seen bad corrosion even after one flight. I consider this a safety issue and something that we all need to check into.

I have since changed all my bulkhead connections (a project that was truly fun for me) to using "speaker" connector terminals I get from radio shack. They enable you to isolate the wire to your altimeters in the INSIDE of the bulkhead (where the connection is made). After each flight you unscrew the plastic coated nut and wipe clean the connection post. VIOLA! no corroding wires. I have one rocket that still has the terminal block and I change them out and replace the wire now after EVERY flight....(safety is more important than anything to me when lofting a 20lb rocket to over 4000 feet).

I just pass this on as an FYI.

If you want me to post photos of these let me know.

Thanks for your time and I would love to hear what you all have to say. Have a great day everybody and launch safe.

 

[neond7]

I would like to see some pics.... I'm always up for a new/better way of doing things. I do know I can tell the zinc vs stainless hardware after just one flight or ground test. BP residue is nasty stuff.....

 

[G_T]

Black powder residue + moisture = acid. It is corrosive. My terminal blocks are now on the inside of the electronics bay and I pass the ematch wires through a hole in the bulkhead. The hole is sealed with hot melt glue and the wires taped down with masking tape, and routed through those little round wire clips so they can't move around. Since the external wires are single use I don't care about them.

Gerald

 

[cwbullet]

Black powder residue + moisture = acid. It is corrosive. My terminal blocks are now on the inside of the electronics bay and I pass the ematch wires through a hole in the bulkhead. The hole is sealed with hot melt glue and the wires taped down with masking tape, and routed through those little round wire clips so they can't move around. Since the external wires are single use I don't care about them.

Gerald

I also put my altimeter and connections in the av bay now also. I got tired of cleaning terminal blocks.

 

[AKVP]

Okay some photos!

The one you can see the outside of the bulkhead...these black and red "caps" unscrew and you are left with only a post to wipe off. The other photo is from the same electronics bay. note the wires are secured with a ring terminal (and soldered) on the INSIDE of the bay....this keeps the wires away from any blast residue. I cannot say enough about these connectors. I have done the same thing on a 4" bulk plate too. I hope this helps!

Thanks

 

[AKVP]

Those are great ideas as well! I was directing the concern for those with blocks on the outside and for those who may not have thought to keep an eye on them. Just an FYI to the masses!

 

[chadrog]

On my bays that have them, I cover them with aluminum tape preflight after the charges are wired. Sealing them off works wonders.

 

[Salvage-1]

I use the same trick that I do with my black powder firearms. Ballistol! Spray down the terminal blocks, etc, with Ballistol, leave overnight, wipe off. The stuff basically dissolves the BP residue.

 

[o1d_dude]

Okay some photos!

The one you can see the outside of the bulkhead...these black and red "caps" unscrew and you are left with only a post to wipe off. The other photo is from the same electronics bay. note the wires are secured with a ring terminal (and soldered) on the INSIDE of the bay....this keeps the wires away from any blast residue. I cannot say enough about these connectors. I have done the same thing on a 4" bulk plate too. I hope this helps!

ThanksView attachment 129402View attachment 129403

View attachment 129408

 

[jmattingly13]

Do you have pictures of the corrosion? I'm trying to get a better idea of what you're talking about.

 

[BEAR]

Back in August of last year a post was made about homemade terminals that go thru the bulkhead wall and get glued in so there is no corrosion and no gas leakage. You can find it at: Forum
General Discussions
Rocketry Electronics and Software
Home made terminal blocks

I would make one change now. I would paint the terminals on the outside after installation since this will not affect the conductivity. (Maybe red and black) This will keep the brass from getting roughed up with corrosion. I also figured out a way to make them from brass tubing which should save some work. If anybody wants to know, let me know and I will go into details. I hope this is of some value. BEAR

 

[AKVP]

I am sorry I do not have any photos of the corrosion. If you have them....Inspect the wires that come through the bulk head and go into the one side of the terminal block. Or take off the terminal block and inspect the wires. Mine were black and green and in very bad shape.

 

[dixontj93060]

OK, at first I was worried. I hadn't remembered seeing any corrosion on my terminal blocks but I wanted to check. I looked at 5 or 6 rockets and nothing. Shown below is a picture of one of the older ones, about 8 years old. As you can see under where the terminal cinches down on the wire the copper is still fresh and shiny. Compare that to the copper charge holder to the upper right (which is definitely exposed to the charge) and you can see the "green" build up on the entry hole. Not saying it doesn't happen, and you have to be vigilant, but I have to ask, how/where do you store your rockets? Is it humid? Also are your charges always directed away from the bulkhead? (Just wondering what the difference might be).

 

[AKVP]

Great photo! thanks for your reply. I see you use solid wire. I use braided. Maybe the braided wire "wicks" in moisture or corrosion and it goes "down" the wire under the insulation. I store my avionics bays in a dry closet that is kept open most of the time. They actually hang on tiny bungee cords on the coat rod....all in a line. They are cleaned and kept dry. My charges are like yours in the photo directed away from the terminal block. I have even covered the blocks with tape to try and reduce the corrosion....during the flight that is...

I don't know....maybe most others don't have this problem...I guess I just have problems with corrosion for some reason....

I see the shiny part of your wire in your photo is where the screw is in contact with the wire. The act of turning the screw could "scrape it clean" This would happen to a lesser degree with braided wire (I now tin all my exposed wire with solder).

I guess if this post prevents one flight with a bad connection due to corrosion, it was worth it.

Thanks for the reply!

Have a good day.

 

[barstoolmike]

I wrap tape around my blocks after connection the charges, they stay clean every flight.

Mike

 

[dixontj93060]

I guess if this post prevents one flight with a bad connection due to corrosion, it was worth it.

Agree! Doing a pre-flight check of your connections is critical. I do use solid wire and I do so so that when I go around and tug things before flight, I can readily detect a clean break. In the end though, I have found more problems with shock cords, shroud lines, knots, etc., than I have every found with my wiring.

 

[darisd]

I only recently started dual deploy this past year. The main charge for my L2 was deep in a 4 inch tube, and my preliminary tests with hooking up terminal block connections by feel led me to seek another solution. Let's just say explosives in a tube that you are armpit deep into is not something you should trivialize.

I was at work (I do RF stuff) and had to get a BNC termination for a technician to do a mismatch test on a PA, and it hit me that BNC was a perfect fit... as a matter of fact anyone that has seen a BNC DC block can see the potential of replacing the DC block side with a BP charge. By design it is self cleaning, has great positive engagement feedback, is reasonably secure (I won't get in an argument about this, but it is more secure than a speaker jack and less secure than a torqued and staked SMA), and is ubiquitous. Any electronics supplier worth their snuff is going to have every conceivable type of BNC in stock.

On my bulkhead I installed a BNC bulkhead adapter with solder terminals on the back side. The leads are attached to a terminal block on the sled after charge installation. Before charges are installed, you short the leads (safety first).

I am still working on making a fully integrated BNC/BP device that is reloadable, but for now I take my squib and wire it to a rubberized BNC test lead. Then all I do is reach in the tube, snap the BNC on, place the squib in the charge well, and tape the charge down.

It is pretty darn slick.

 

[tstone]

Got pics?

 

[darisd]

Got pics?

Not at the moment. Just got my L2 and it is kind of a mess. This however is a BNC termination.

 

[degreaser]

AKVP - where did you get your terminal blocks?

Molex makes higher quality blocks than you can get at Radio Shack. e.g.

https://www.digikey.com/product-sea...o&lang=en&site=us&keywords=WM15904-ND&x=0&y=0

 

[tstone]

WHOA looks Medieval!

 

[warnerr]

Black Powders corrosiveness is why so few arms exist today in perfect condition- it took thorough cleaning to prevent corrosion. Knowing this I have been using Dielectric Grease - it is conductive (or you can get the non conductive variety)! It is available at HAM stores and is generally sold for coating coaxial cable ends.

 

[degreaser]

Dielectric grease is a great idea. This thread has got me thinking though. Perhaps the wires should be replaced at the beginning of each flying season. A little PM might go a long ways to preventing a deployment failure.

 

[AKVP]

Degreaser-

I got my terminal blocks at Radio Shack. I too was thinking that maybe when I clean the bulk heads and blocks at the field, the moisture from my wet wipes mixe3s with the blast residue and wicks into the block and wires.....exasperating the situation...either way I am glad this thread got some of us thinking and checking wire connections etc..

I would try the dielectric grease but I already have isolated my wires on the internal side of the bulkhead. The posts I showed in my above photos has a hole in it so I can slide my e-match/Q2G2 into it, wrap it around the post and screw down the plastic coated nut....it is not going anywhere at that point. After the flight I simply give the post a quick wipe and I am done.

NOTE: if you go to Radio Shack there are two kinds of posts I am talking about. The one I use are 4 to a pack (I am pretty sure) and the red and black are separate and individual posts. There is another kind that are in the same drawer...they are huge! and come as an attached set. Look at the above photo I posted and you will see what I mean.

Anyway to reduce the possibility of deployment failure is a good thing...

THANKS for the replies!
Have a great day folks
Andrew

 

[awseiger]

I use the "speaker connectors" that you speak of for all my rocket needs. They work wonderfully. Over in EE land we call them "binding posts" or "banana plugs". All the same thing. I get mine at amateur radio festivals in bulk bags. I have about 50, all red, that cost me around 12 bucks. Sure they're a little big but they make a solid connection that I can easily verify. Also, there are no tools required. Gotta love them!

I usually strip off a good 3 inches. I put the bare wire through the hole and wrap it around the post 2 or 3 times before I tighten it down. Never had anything even close to a failure.

Those RadioShack terminal blocks are awful in almost every way. I wouldn't trust them to putting cream in my coffee. This goes for a lot of RadioShack things. The binding posts (speaker connectors) are wonderful though, although definitely in the cheap side.

Real terminal blocks will have some method of ensuring that all of the wire will get pressed on by the screw. Usually they are made of solid brass or copper, and have squared out inserts, etc. they are expensive, but the price you have to pay for making a good connection.

 

[Golfpro62]

I use the same trick that I do with my black powder firearms. Ballistol! Spray down the terminal blocks, etc, with Ballistol, leave overnight, wipe off. The stuff basically dissolves the BP residue.

Ok, so this is very close to the product that I would use to clean my sons Trap Shotgun it sounds like? So then, this product would probably do a excellent job of cleaning the residue left in my motor casings and how about body tubes? Makes sense. Those of you who use this, tell me if this is correct. I always have a heck of a time getting the motor casings clean and if used with a soft cloth it should make that a snap right? Wish I would have known this a long time ago. Always learning something new around here.

 

[degreaser]

Degreaser-
The one I use are 4 to a pack (I am pretty sure) and the red and black are separate and individual posts. There is another kind that are in the same drawer...they are huge! and come as an attached set. Look at the above photo I posted and you will see what I mean.

Mouser has mini binding posts. Heck, they are even gold plated A bit pricey too:

https://www.mouser.com/ProductDetail/Pomona-Electronics/2439-2/?qs=sGAEpiMZZMv8kklI404QlZSqwcK4PrV9

 

[degreaser]

Real terminal blocks will have some method of ensuring that all of the wire will get pressed on by the screw. Usually they are made of solid brass or copper, and have squared out inserts, etc. they are expensive, but the price you have to pay for making a good connection.

Exactly. The molex version of the terminal blocks behave exactly as you have described. The screw presses down on another piece of metal which then presses down on the wire.

 

[degreaser]

Here's an image of the molex version of the terminal block. On the first terminal, I've screwed the screw in a bit. Look closely and you can see the metal plate which compresses the wire. The screw does not make direct contact with the wire.

 

[Issus]

I've switched from using eurostyle barrier blocks to the american style arrier blocks. The eurostyle are almost impossible to clean and dont always support fine wires very well.

With a single layer of 25mm wide masking tape over (not even trying to seal it) they stay clean - even when the plywood around it is scorched.

My current AV Bay design for 4", i tend to change every rocket though