How do you lock the 2x4 into up or down position?
Discussion
There's a lag screw that sticks out of the bottom bar of the tractor frame, and a small metal plate attached to the 2x4 wheel arm. The metal plate has a notch cut into it so that it locks under the bolt. Hard to explain, but I'll take a photo of the mechanism tomorrow and post it.
Here are the photos of the wheel locking mechanism on my chicken tractor, as promised. To make the locking plates, I just drilled a large hole in a scrap piece of 1/8" thick steel, then cut it in half right through the center of the hole to end up with two pieces each with a semicircle cutout that locks into the shank of the lag bolt perfectly. You could also notch it out with a grinder or dremel tool. The plate is just screwed to the back of the 2x4 wheel arm.
Ah, that makes sense now, and thank you for posting this.
Why the need for the metal plate?
I recognize the use for the pivot bolt and positioning of the wheel.
But to achieve the locked down position, could you not also drill a hole through the 2x4 arm as well as the frame and put a bolt through to lock them in sync?
We use the bolt method for our milking stanchion and I am wondering if we can improve with the metal plate.
Yes, putting a bolt or pin through would lock it just as well (more securely, actually - every once in a while one of the arms will bump something or get caught on a rough bit of ground and pop out of the catch). A bolt was going to be my first design, actually, but then I thought of doing it this way. The primary advantage of this is I don't have to bend down to put a pin in. I can just step on the arm, which lifts the tractor, and push the catch plate over just a bit to latch it under the lag bolt. Move the tractor, and use your foot the same way to unlatch it and set it back down. That's why there's an extra chunk of wood attached to the front of the arm, to give more area to step on.
In case the geometry isn't clear, here's an overall shot of the wheel assembly. It pivots on the bolt at the back, so when the front is pushed down and locked, the wheel contacts the ground and the frame of the coop lifts up about an inch or so. The wheel is attached to the pivoting arm with a carriage bolt.
From this picture I think I am realizing the answer to my other question.
The metal allows the bolt to stay in a set location and the wheel has enough play side to side to pop onto the bolt head when the tractor is lifted.