Jamie

Jamie

Well Known Member
Guys:

I'm tidying up my electrical stuff on my -7A. I have both aileron and elevator electric trim on both sticks and am consequently using relays. I'm using the RAC grips 207 and 205 grips.

Anyway...I'm curious how people deal with d-subs and those tiny trim wires. Here are my options:

1) Throw out the d-sub connectors and just connect the pins together and heatshrink over them. I've done this in some other places but I wanted to make it easier to remove the relays when (not if) they fail.

2) 'Lectric Bob's shoe goo connector deal, which I presume he does for vibration insulation purposes.

3) Use solder d-subs instead of the crimp style, then heatshink each wire over the solder connection for vibration insulation.

I guess my main concern is that those wires are VERY fragile. I've already crimped a couple of pins that easily fell off when I did a pull test. I don't want to be chasing trim wires in the future. Also, I feel that there exists a safety of flight issue here. If the elevator trim runs away it's going to make for an interesting landing. :)

Thanks,
Jamie (sort of wishing I would have just done manual trim)
 
Jamie said:
Guys:

I'm tidying up my electrical stuff on my -7A. I have both aileron and elevator electric trim on both sticks and am consequently using relays. I'm using the RAC grips 207 and 205 grips.

Anyway...I'm curious how people deal with d-subs and those tiny trim wires. Here are my options:

1) Throw out the d-sub connectors and just connect the pins together and heatshrink over them. I've done this in some other places but I wanted to make it easier to remove the relays when (not if) they fail.

2) 'Lectric Bob's shoe goo connector deal, which I presume he does for vibration insulation purposes.

3) Use solder d-subs instead of the crimp style, then heatshink each wire over the solder connection for vibration insulation.

I guess my main concern is that those wires are VERY fragile. I've already crimped a couple of pins that easily fell off when I did a pull test. I don't want to be chasing trim wires in the future. Also, I feel that there exists a safety of flight issue here. If the elevator trim runs away it's going to make for an interesting landing. :)

Thanks,
Jamie (sort of wishing I would have just done manual trim)
Click to expand...
Got a buddy that likes the crimp style. I soldered all mine. Just have to make sure you have a hot iron, clean connections and a good bond. (Knock on wood) have had only one bad connection in almost 900 hrs. Was in a transponder encoder connector back around 40-50 hrs. IMO, it's easier for me to tell that I have a good joint when soldering.

I just converted from hardwired Infinity stick grip to that having a d-sub connector. PITB soldering all those little wires - but not as much as much as having to deal with all those leads hard-wired into the plane.

I have 4 or 5 others soldered d-subs in various locations in the plane with no problems. Will have to check out the Shoe Goo thing. I guess this is where you'd glue the leads at the connector to prevent vibration damage?
 
Hey Brian,
FWIW, I always doubled the tiny (24&26ga) wires back on themselves before crimping the pins. Be careful not to trim off too much insulation or you'll end up with a mechanically weak connection. I used itsy bitsy heat shrink (not too far forward on the pin or you'll be unable to seat the pins in the d-sub) on the back of the pins. I then used another (larger) piece of heat shrink around the wires as they go into the back of the d-sub.

Inside the stick and in other places where I wanted a splice, I simply used the male/female pins as connectors, and then used heat shrink over them. If you find the right fit on the heat shrink, these make a great connection. On some cables, you need to sequence your splices so you don't end up with a big bundle of splices in one spot.

I assume you are not planning on using d-subs INSIDE the stick tubes...that seems a little tight to me.
 
Right crimper

how are you crimping the joints?? Regular automotive crimper's wont work well on such tiny pins.

Check out the crimper just for d-subs here http://www.steinair.com/tools.htm

Part sat 004.

While using solder is an alternative, the solder tends to wick up the wire, and stiffen it, ends up causing a place for the wire to weaken/break. Be sure to use shrink tubing or some other method as shoo goo to support the wires out to past the solder.

Mike
 
As Bob said

Stip back a little extra and then double back to make a better connect with the crimper.

Kent
 
I forgot to mention that I'm using Stein's 4-day indent crimper.

On my pax stick I have a Molex inside of the stick to make it removeable but that's it. The rest of the stuff is just for make the relays and the servos easily serviceable.

Oh yeah...one neat thing that I did was pull a separate ground run to the pax stick to a switch on the instrument panel. Flipping the switch enables pax trim. That way I don't have to worry about white-knuckled pilots in the right seat hitting the hair trigger trim buttons on top of the grip.
 
Micro-Molex

I don't have the link handy, but Digikey has a micro-Molex connector that may work well. I bought a bunch of the 6-pin connectors/ pins but haven't given them a try yet.

Jim
 
JimP said:
I don't have the link handy, but Digikey has a micro-Molex connector that may work well. I bought a bunch of the 6-pin connectors/ pins but haven't given them a try yet.

Jim
Click to expand...

Jim, do you have an online source for those??
 
These ones?

RudiGreyling said:
Jim, do you have an online source for those??
Click to expand...

Rudi,

DigiKey has a good on-line web store.

I believe these are the connectors referred to above...

http://dkc3.digikey.com/PDF/T071/0157-0159.pdf

They don't mind small orders...Small fee added if order is under $25...

Handling Charge
A $5.00 handling charge applies to all orders less than $25.00. This fee will be waived on orders of $25.00 or more.
A $6.00 processing fee will be applied to all International orders, excluding Canada.

gil in Tucson
 
Last edited:
Pile-On...

The part number I have is A25660-ND (Mini Univi Mate 2). Again, I haven't tried these yet but they are the right size and look like they will do the job. You'll need to order the associated pins with these as well.

As Gil mentioned, Digikey has a nice on-line catalog, but with so much stuff, it's sometimes hard to figure out what you want/ need. I find their service is some of the best. I normally get an order in 2-3 days max and order size isn't an issue. Again, weeding through the catalog or even the hard copy takes a little doing.

Jim
 
Last edited:
This page..

JimP said:
The part number I have is A25660-ND (Mini Univi Mate 2). Again, I haven't tried these yet but they are the right size and look like they will do the job. You'll need to order the associated pins with these as well.

As Gil mentioned, Digikey has a nice on-line catalog, but with so much stuff, it's sometimes hard to figure out what you want/ need. I find their service is some of the best. I normally get an order in 2-3 days max and order size isn't an issue. Again, weeding through the catalog or even the hard copy takes a little doing.

Jim
Click to expand...

Then this is the catalog page needed... :)

http://dkc3.digikey.com/PDF/T071/P0179.pdf

gil in Tucson
 
Why crimp pins at all?

Being an Electrical Engineer and using D-subs of all sizes for many many years, I have learned a few things. The first thing I learned is to not use the connectors that have the loose pins. Unless you have the exact right gauge wire and some pretty expensive tooling, you cannot get a really good reliable crimp by crimping alone. You just simply have to solder them. This involves getting just the right amoung of solder into the crimped connection so as to make it solid without wicking solder up into the wires-- creating a hard point that can break easily. Here are my recommendations.

1. Go to Digikey or Newark or some other electrical supply house and buy the proper sized connector that has solder cup pins molded right into the connector. The only ones I will buy are the gold plated ones. The tin ones work fine for a few years, but after that, can corrode and cause intermittent connection.
2. Get some small clear heat shrink tubing and put it over each wire you are going to solder into the connector. Hold the connector with a small portable vise so you don't need 4 hands.
3. strip the wire just long enough so it will go into the solder cup and just leave a very little bit of bare wire sticking out. Take a small bit of solder and tin the end of the wire-- being sure not to put so much on it wicks up under the insulation much. Make sure, also, that it will still fit inside the solder cup.
4. Insert the wire into the solder cup, and with the iron applied to the outside of the cup, heat it up, and touch a little bit of solder to the top of the cup. It should suck right down into the cup-- filling it.
5. let it cool and then slide the heat shrink down over the wire and the solder cup. Heat it to shrink it down.
6. Once all of the wires are soldered, make sure you use a back shell that will hold the wires. Take some lacing wire, and tie the wires very tightly together right at the back of the shell, as close as you can to the solder cups. This will make them move and vibrate as a unit. You can put shoe-goo or something else in, but it is not necessary, if this is done right.
7. Install the back shell cover on the wires. Make sure that the grip on the backshell cover actually clamps onto the wires. In most cases, take some larger heat shrink tubing,(do it before soldering) and slip it over all of the wires. This will create a cushion for the wires when they are clamped by the back shell cover.
8. The idea here is that a back shell must be used. With aircraft vibration and by soldering, you are creating a hard point where the solder in the stranded wires ends. Therefore, this point must be kept immobilized. The back shell and the large heat shrink tubing creates the flex point for the vibration-- a long ways away from the hard point that must not vibrate.

If you just use pins, I suggest you go to a different connector, like the Molex units someone else suggested. These are larger, and don't work with really small wires well.

One other thing I did with my Mac trim servos. For years I have tried to get them to put larger and longer wires on their products--to no avail. I took their servos apart, removed their wires, and installed a military circular 5 pin connector right in the side of their little black box. Now, I can, reliably, wire the darn things up. ----Let's not talk about their switches and other controls with micro gauge wires being 0.03" long. Just about unusable without splicing, splicing, splicing. This is just stupid. I wish they would get the message. What are they saving? 50 cents worth of wire? My ramblings.

Roger.
 
You must log in or register to reply here.