Captured Loop Key - Design, Development, and Documentation

[sleepless]

Alright ladies and germs, here we go. I think this project is far enough along to push it out into the wild.

In action:

Captured Loop Key V5

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The Goal

is a new loop key design that is:

• easily 3D printable
• captured / self-contained / no losing keys or carrying another fob
• compact & small footprint
• secure mounting
• locks out when powered down
• slick looking
• reliable

To that end, I present the Captured Loop Key V5.

Inspiration

Big shoutout to @glyphiks and @janpom for their fantastic designs I was heavily inspired by. Go check those out if you want another/different option - Jan’s Riser Pad Loop Key, Al’s Enclosure Mount Loop Key

Thanks

Big thanks to @Venom121212 , @glyphiks , and @janpom for providing feedback on the V4 version. Really appreciate the comments! The sliding action should be much easier now.

Specs

• Ring Handle version: 78mm L x 33mm W x 17mm H
• T-Handle version: 52mm L x 44mm W x 17mm H
• Mounting Hardware: requires qty 2 x M3 hex nuts, qty 2 x 8 or 10 mm long M3 fasteners (depending on enclosure wall thickness)
• Epoxy strongly recommended to lock the XT90 connectors into their housings. But DON’T COVER THE NUTS!

Files

to Print your own: listing on Printables.com with all files including fusion/step

• Mount (for XT90 Male) - Captured Loopkey - Mount V5E.3mf (184.3 KB)
• Slider w/ Ring Handle (for XT90 Female) - Captured Loopkey - O-Slider V5E.3mf (348.5 KB)
• Slider w/ T-Handle (for XT90 Female) -
  Captured Loopkey - Short T-hook V4.3mf (286.8 KB)
• Easy diagram for drilling mounting holes: Captured Loopkey Drawing v3.pdf (176.4 KB) → PRINT THIS ON 8.5"x11" AT 100% SCALE AND TAPE TO ENCLOSURE

Recommended Print Settings

• 0.20 layer height
• 4 perimeter walls, 4 top/bottom - # of walls is important to get max strength in the slider arms
• ~20% infill (i prefer Gyroid pattern for strength and speed)
• “Mount” set vertically (opening down), “Slider” set horizontally - this is important, see below
• Brim on “Mount” to ensure 1st layer adhesion, as necessary
• I print without, but support on the “mount” may be required to get a good fit for the female XT90, depending on how good your printer is at bridges.
• Print time: should come in around 3 hrs for a set
  (PrusaSlicer settings:)
• Avoid crossing perimeters ON (to avoid stringing inside the cavity)
• Seam - Nearest (for nicer surface finish / avoid zits)
• External Perimeters First - this allows for better dimensional accuracy on the “Mount”, which enables better fit between parts
• Thick Bridges - this may help the bridging on the “Slider” if you don’t use support
• Enable Ironing (topmost surface only) - if you want a very nice, smooth top layer

Print in this orientation:

Technical Design Features

Development

V1 and V2: 3D printables for esk8 - #1039 by sleepless
V3: NESE modular jumper - 🐉 Dragon MTB build - #114 by sleepless
V4: NESE modular jumper - 🐉 Dragon MTB build - #117 by sleepless

Instructions

Photo Guide

Notes:

• The Ring Handle version can take any normal loopkey. It’s get extra depth to account for an off the self (unmodified) XT90 with a section of 12awg connecting the pins.
• The T-Handle version is designed to be as short and compact as possible. You have 4mm total height for the pins and wire on the end of the XT90 female. This means the pins need to be dremeled down.

Gather your materials. The T-Handle version requires the super low clearance loop key.

Don’t use this much epoxy. If you do, it squirts out through the actual pins of the XT90 and then you have to clean it out with q-tips. You don’t need much.

Press connector into hole, with some force. It will snap in solidly.

Build the other half

Make sure you don’t use too much heat shrink or it’ll be tough to feed and bend the wires

Final assembly

MAS IMPORTANTE: press the nuts in with a small pair of pliers before inserting the connector

Wires first. Add a small amount of epoxy here to the outside of the connector.

Push the slider onto the mount and it should snap satisfyingly into place

Print the diagram, cut out the 1:1 scale view, and tape to your chosen location.

Drill your holes (9mm or 3/8" bit is good for 2x 12awg wires)

Install fasteners. Don’t forget the blue loctite.

Mount

Close

Silicone the hole if you don’t like water

Done!
Enjoy the satisfying snap.

Notes / Feedback / Next Up

• More handle styles - shorter o-ring slider, pinch slider
• The lock-out (holding power off) detent is too weak. I had my board vertical and the loopkey slide partially closed. Very confusing behavior until I figured it out. Hopefully this didn’t/won’t cause any damage, but something I’m going to resolve asap.
• The 2 screw offset mounting design is surprisingly strong. I was a bit worried it would rip out eventually, but it’s solid as a rock. Confidence inspiring. Could easily move to 3 screws and/or bump up to M4 screws if necessary.

[Tanuki]

Oh no

Just kidding, awesome post and project!

[sleepless]

This is allll a fever dream

I’ll fill in more details later. Group ride starts in 20, gotta go skate!

[DeadLightning]

Looks awesome! Just printed out the ring design and need to figure out the best place to put it on my enclosure.

[zero_ads]

Damn this is detailed, very nice work.

[Venom121212]

Super clean work. The template is a really nice touch too

[janpom]

This is so neat! Also the level of detail on your write up is astonishing.

[DeadLightning]

Are you planning on releasing .step files files for this as well? Was thinking about possibly trying to make a couple different handle versions.

[sleepless]

Sure, absolutely. I can even post the fusion files although i wouldn’t encourage anyone to wade through that timeline

[Linesflag]

@sleepless

timeline

That’s the sole reason nobody gets to see my Fusion files.

[sleepless]

Just posted this to Printables with fusion and step files. I’ll keep that up to date with only the latest versions for one clean place to download.

Let me know if there are any issues, or you have questions, etc. There’s a lot of small gaps, angles, and chamfers that really had to be dialed in. If you want to change any functional features, I’m happy to help walk you through it.

@Archer
@Tennisball555

[DeadLightning]

Currently working on a “select-a-battery” slidable loopkey. Think I need to fix the interference for the middle position but it’s looking good so far.

Thanks for doing basically all the heavy lifting on this one @sleepless, love the design!

[sleepless]

Oh! Super interesting. So you had to extend the slider arms to get enough travel for all 3 positions. What sort of feature are you using to indicate the neutral position? Are the 2x mounts physically connected?
Nice work!

[DeadLightning]

The neutral position is currently indicated by a second nub on the side of each mount that is the same as the one near the hook on the end. I basically copy pasted it over about 3mm. It slots into the grooves on the end of the sliders. Right now the interference isn’t quite enough, it slots into neutral but it’s really easy to move it out. The mounts are not currently connected because I didn’t want to add thickness and printing it would be harder. May add a connector if it is hard to mount.

I’ll take some pics when I get home.

[DeadLightning]

Here are some pics of the nubs:

Definitely need some more interference when not assisted by the hooks.

Trying to figure out if it’s possible to save some space in the center by making a double loopkey, but I’m not how I would even go about soldering that, or if it would cause any weird issues.

[glyphiks]

This is really cool! Nice work!

[DeadLightning]

I still need to work on the interferences but I made a V2 of my double design. I really didn’t like how the original had 3 parts so I reduced this one to 2.

Middle section bows out a little bit but at the moment it is actually causing it to click really nicely