I was asked: " what does the spring do by your right foot? "
That spring engages the drive clutch drum on the engine.
When I first got this crawler running, I felt it was kind of awkward trying to operate the steering clutch and the hand clutch on the engine at the same time so I decided to put a foot operated clutch on it.
Here is a closer view of the rear of the crawler.
There is a foot pedal on the left side that operates a jack shaft that is mounted to the underside of the rear cover plate.
The pedal arm had to be formed so it would move up and down in-between the backing plate and the curved bar that runs across the back for the draw bar.
The pedal is angled over so it is close to the left foot pad.
A rod is attached to the right side of the jack shaft and comes up in front of the backing plate.
This attaches to a lever on another jack shaft that is mounted on top of the backing plate.
The drive clutch rod is operated off the left side of this upper jack shaft.
There is a lever on the back of this upper jack shaft with an arm that goes down to an "over center" cam that is bolted to the backing plate and the big spring is mounted to this cam.
When the foot pedal is pushed down, the drive clutch rod is pushed forward to open the clutch and engage the clutch drum brake.
The cam on the backing plate is rotated so the mounting bracket for the big spring is brought up over center.
This takes the spring pressure off the clutch pedal so my foot doesn't get tired while I'm holding the pedal down.
When I release the clutch pedal, the cam rotates off the center point and the big spring pulls on the linkage so the drive clutch is snapped into place to drive the crawler.
The smaller spring mounted to the upper jack shaft lever is just enough tension to pull the cam off center so the bigger spring can pull it down.
I realize this is sort of a complicated looking linkage but I had to design a system that would fit within the limited space that was available on the back of the crawler.
The linkage works very well and once it was all adjusted, I haven't had to change it in the 30+ years that I've been working the crawler.