Scale trailer coupling.
A couple of guys have asked for a tutorial for this coupling so although photos are sparse, I'll try and be as specific as I can.
I started with a off-cut of 10mm solid square bar, 33mm long. (I was just lucky it was the right length)
Then I drilled the hole for the towball (5x 9mm) which came from a Highlift. You have to elongate the hole towards the back of the coupling for the locking pin to fit. Drill a 2mm hole on an angle so that it exits the recess where the towball goes (pic #1). Then drill the hole again with a 3/16 bit but only drill about 3mm into the original hole. DON'T GO ALL THE WAY THROUGH!!!!!! This provides a bed for the brass tube.
From there I just shaped the steel to make it look like a real coupling. All I had was a 5' angle grinder, a file and a steel dremel bit in a drill press so I did the best I could. The angle on the back bone and the rounded nose was done with the grinder and file and the recess for the bolt holes was done with the dremel bit in the drill press. Just take your time until you're happy with the shape (pic #2 & 3). I drilled the 3mm mounting holes before shaping the steel to get them straight. And thats pretty much it for the coupling itself, the locking mechanism was a bit trickier...
Here I used a threaded servo rod, 2mm nut, a piece of 3/16 brass tube (about 8-10mm long), a cut down spring from a ball point pen and a 4mm ball connector.
Screw the nut all the way onto the servo rod as tight as you can (or just use threadlock). Then you need to round off the nut so that it slides easily (but not loosely) into the brass tube. One end of the brass tube needs to be capped off to prevent the spring from coming out. I just heated the end and tapped it with a hammer. Just make sure you leave a hole for the rod to pass through.
When you slide the rod into the brass tube, the nut should be flush with the bottom while you should have about 3mm of thread poking through the capped end. The length of the spring is determined by the distance between the nut and the capped end. Screw the ball connector on and you have your spring loaded handle. (pic #4 & 5)
The end of the locking pin that actually touches the towball needs to be recessed as well to lock around the towball. I just put the rod on the corner of the bench grinder wheel (pic #6). When it's all together, the locking pin should be about level with the bottom of the coupling (pic #7).
Then slide the handle mechanism into the coupling. If the hole is drilled right, it should be a tight fit (pic #8.
Well that was probably as clear as mud so if anybody needs more details, feel free to email me. Thanks again.
Comments
Wyoming
Very nice work, I'll have to give it a try when i build meself a trailer, thanks
Drjack
Thanks, mate. It was really very simple to do, it kinda just fell together.
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