This is a completely revised Knuckle coupling for G scale garden Railways.
Video is here: https://youtu.be/kimp_JnspIU
I was not satisfied with the performance of my previous designs, and so have completely revised this version. Operation should be clear in the video.
There is also a "fixed" version of the knuckle that is for carriages etc and is a simple one piece part with integral plastic springing. These connect easily to each other and to the servo operated version.
Coupling TO a train can have the moving coupling either open or closed. With it closed, more force (speed) is needed to connect. With it "open", coupling can be done at very low speed, but the alignment of the two couplings is more critical.
I used my RC controlled Tram for the videos.
The "cutout" versions of the housing and internal body will be needed for some locos, unless you want to cut the loco body to fit the "standard" fully enclosed version.
The iges files can be found at https://grabcad.com/library/servo-operated-knuckle-coupling-1
1 Oct 17, made a very small tolerance change to the disconnect lever servo holes, to make it easier to fit the servo horn, plus I have moved the "connection axis" of the coupling 1.2mm to make for better coupling on the track. This revised the Main Hook and the Fixed Knuckle "FIXED_KNUCKLE_7DEG.st" part.
FYI, the 7 degrees refers to how "open" the fixed knuckle is. With a o degree open part, the knuckles lock so tightly they cannot be easily parted. 7 degrees was a nice compromise. Locks well, but also allows for release when required.
To fit the Fixed knuckle to your trucks and coaches you will need to print (one of) the LGB housings. these are here: https://www.thingiverse.com/thing:1989545
Chose the housing that works best for your truck/coach etc.
Kossel XL with Magnetic couplings
0.4mm nozzle, 0.2mm layers
Assembly and notes:
The only part than needs to be realigned for printing is the moving knuckle, which should be printed 180 degrees rotated, so the "large" part is on the bed, and the "small" part is printed above it.
Supports are essential for the main body, and need careful removal once printed.
The "top link" is not strictly needed, but ensures that the 0.6mm staple used to hold the knuckle to the main hook is the correct size. I Marked a pair of long nosed pliers with a mark to get this dimension right. If the staple is not the right size, the moving knuckle will not work correctly.
One end of the knuckle can be bent to secure it, but the other must be filed down or it will interfere with the disconnect lever movement later.
The lock wire is made from 0.9mm paperclips. This must be very free to move when assembled. The best assembly process is to bend the main locking feature first and assemble it to the hook, checking it operates freely before bending the counterbalance end and soldering on an M3 nut. Check that everything works before proceeding!
The two "internal bodies" need to be glued (acetone or cyanoacrylate) to the main body.
The Disconnect Lever has a cut out for a 3mm dia by 2mm magnet that helps keep the locking wire in the "lock" position. The magnet is held in place with cyanoacryate.
The slots for the servo horn will need to be opened a bit with a screwdriver to fit the srvo horn, which will need to be cut down so it does not interfere with the main body or the screw that holds the main body to the loco.
Push fit the Hook assembly into the main body. then fit the small lock body above it. This will mainly engage with the loco coupling pin, but keeps the hook assembly in the correct position.
Fit the disconnect arm to the servo and cut down the servo horn, then test fit the servo on the main body, and check the servo operation. It may be necessary at this stage to cut or bend the lock wire to get smooth operation.
Remove the servo and disconnect lever and fit the main body to the loco.
Replace the servo, re check for operation and put the wiring in the groove on the outside of the internal body.
Fit the main housing and secure with two 1.7mm *10mm screws.
All the parts
Wiring fitted outside the "internal body", well away from the servo and the disconnect lever
Add a mark to your long nose pliers to get the "staple" dimension right. It is very important that this part is the correct dimension.
a correctly made staple fits the top link exactly.
First fit of the lock wire, it should move easily. You can fit the knuckle at this point and check movement.
Counterbalance weight (an M3 nut) fitted before soldering and removing excess wire.(note, a large blob of solder works also works well as a counterweight, and can be easier than trying to solder stainless steel nuts.
Main body screwed to loco. Moving knuckle fitted and staple wires cut short so they do not hit the servo actuator arm
Servo and actuator arm fitted for testing.
Close up of the wiring positioning (on another model) before the housing is fitted. You should find that you can gently move the servo by moving the disconnect lever. Fit the housing and screw it just tight enough so that the servo is held gently.
This was designed using Fusion 360 (thank you Autodesk !)
This is a fully revised version of my earlier designs. It was much easier to design using F360, as I could make copies of the interconnecting knuckles and check their interfaces, and if I needed to change a feature on one part, the copy was changed as well.
This shows two couplings nicely connected, but also that the servo horn needs to be cut down!!...