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  #1  
Old 01-17-2022, 08:15 AM
bob865 bob865 is offline
 
Join Date: Feb 2021
Location: Greenville, SC
Posts: 33
Default Electric Elevator Trim

I've made it to the part of the build where I'm working on my elevator trim. I'm thinking about how do I route the wire for the trim servo. looking at it, I see a few problem I want to solve, and before I re-invent a method, I wanted to see if anyone else had some insight. I did a quick search and didn't find what I was looking for so here I am asking the question.
  • Access to the trim servo in the future for service and or replacement.
  • Potential collisions with the cable and the screw drive.
  • Wire Chaffing concerns.

For the first point, if I leave enough wire to allow for removal and/or service, this wire is 'floating' around inside the elevator. I would also have to cut the wires if I ever want to replace it, or remove it.

For the second point, if any extra wire is left in the elevator, it could potentially move and catch in the screw drive and either chafe the wire rendering the servo inop or binding the servo itself causing potential problems. The screw drive uses the hole for the manual servo cable for clearance with the elevator spar.

For the last point, excess wire that is not secured can also chafe.

I measured the current draw of the servo and it's less than .25 amps. 0.12 to be precise, but that's with no load. So the power draw if very low. I haven't found what I actually want yet, but as an example, I'm thinking maybe something similar to this.

https://multimedia.3m.com/mws/media/...unt-ts2092.pdf

This would let me mount a connector in the spar below the manual trim cable hole that the servo could be plugged in to. This way, I can keep the amount of wire inside the elevator to a minimum, but still easily plug/unplug as necessary. This would also act as the grommet for where the wire passes through the the spar for edge protection.

I still need to do some looking for the connector I would want to use. Ideally I want to use a small molex type that will just 'snap' into the hole in the spare to make it easily removable if needed. I also want a 'snap' lock connector instead of screws. I would be concerned screws might vibrate loose. Snap locks are not likely to vibrate loose.

I did a quick search to see if anyone had done something similar, but I didn't find anything. Does anyone have any ideas before I re-invent the idea?

Thanks!
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Empennage Kit: In work (90%-ish)
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  #2  
Old 01-17-2022, 04:09 PM
bob865 bob865 is offline
 
Join Date: Feb 2021
Location: Greenville, SC
Posts: 33
Default

Did some more looking and found what I want to use. These are molex nano-fit connectors. They are rated for up to 250v and for the 6 pin connectors up to 3.6 amps. I'm thinking the panel mount for the spar. I'll cut a small rectangle hole and it will snap into the hole for the connector to the front of the plane. This will become the grommet for the wires where they pass through the spar.

https://www.digikey.com/en/products/...AsKFjgNhAXQL5A

The other end will be connected directly to the servo. When installing the servo, you'll plug it in and then drop it into place. Removing reverses the procedure.

https://www.digikey.com/en/products/...AOOYEDYQF0BfIA

For the contacts, I selected the thick gold plated contacts for corrosion resistance.
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First Time Builder
RV8A- Status:
Empennage Kit: In work (90%-ish)
Wings Kit: Ordered (Standard Build)

https://eaabuilderslog.org/?s=Adam_RV-8
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  #3  
Old 01-17-2022, 07:07 PM
Scott Hersha Scott Hersha is online now
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 2,198
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Iíve gone through this setup a few times myself. I always want to be able to remove the elevator without cutting wire, so some kind of connector is required. This connector needs to be able to fit through the opening you choose in the elevator forward spar. Iíve done it two ways, and both of them worked fine. The first one involved using a terminal block with #6 ring terminals on each wire, similar to this:

https://www.steinair.com/product/4-p...erminal-block/

The ones Iíve used had 5 positions on the block, which is what you need. The individual ring terminals fit through the openings in the elevator and HS just fine.

The other method Iíve used is D-Sub pins and sockets on each of the 5 wires (no connector). After the pin is inserted in the socket, I use a pair of pliers, or some sort od crimper and put a little squeeze on the connection. Then I heat shrink over each wire connection. As long as the collection of pins and sockets are supported for and aft of the connection, thereís no danger of it coming apart, and with a razor blade to remove the shrink wrap, itís easy to take the connections apart for removal.

For shielding the wires from chafing, use some anti-chafe sheathing or extra heat shrink in that area, or protect the edges of the metal opening with some cat track:

https://www.aircraftspruce.com/catal...lickkey=399844
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RV6/2001 built/sold 2005
RV8 Fastback/2008 built/sold 2015
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  #4  
Old 01-22-2022, 02:18 AM
benjam benjam is offline
 
Join Date: Mar 2019
Location: Brisbane, Australia
Posts: 39
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Hi Bob,

Iíve got some of these digikey connectors. I find that the pins donít locate easily and stay put. Do you find that? Did you get the optional support/ stays for the wires?
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  #5  
Old 01-24-2022, 10:53 AM
bob865 bob865 is offline
 
Join Date: Feb 2021
Location: Greenville, SC
Posts: 33
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Quote:
Originally Posted by benjam View Post
Hi Bob,

I’ve got some of these digikey connectors. I find that the pins don’t locate easily and stay put. Do you find that? Did you get the optional support/ stays for the wires?
I didn't see an option for support/stays. I will have to check. This connector is really pretty small and while I've never used it for exactly this application, I've not had issue with this style of connector before. The connectors came in Friday and the pins come in today. When I give them a try, I'll update the post.

*Edit* I found the retainers you mentioned. I will be adding these if I stick with this. Seems like easy insurance to add redundancy to the connection.
https://www.digikey.com/en/products/...sBmMTEJSAugXyA
__________________
--Adam

First Time Builder
RV8A- Status:
Empennage Kit: In work (90%-ish)
Wings Kit: Ordered (Standard Build)

https://eaabuilderslog.org/?s=Adam_RV-8

Last edited by bob865 : 01-24-2022 at 11:14 AM.
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  #6  
Old 01-25-2022, 08:52 AM
Steve Steve is offline
 
Join Date: Jan 2005
Location: Roy, Utah
Posts: 1,262
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I went with this Stein idea on my -9A.
https://www.youtube.com/watch?v=f8DCvBV2V4M&t=46s

Two local -14 builders also went with this after they had difficulty working with the supplied Molex connector.
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