I know the car doesn't have a throttle, but you know what I mean. I'm talking about the piece of linkage that moves the injector pump rack attached to the accelerator pedal gizmo on my om603
I needed to remove this piece of linkage to get a tool on #3 glow plug that needed replacement. Prying the link off cracked its ball end. 30 years of plastic patiently waiting to do that finally had its chance. It's a gamble each time you pry off linkage ends of this vintage
For reference, this link is 8mm ball joints on each end, and I measured my link to be set at 15.5 cm ball-to-ball (centers).
Luckily I had been designing ball joint linkage for a different purpose using CAD software and a 3D printer I own. So I had a good starting point. I designed a link for the broken one and printed it out. Just fit on my 6" x 6" printer bed when printed on the diagonal of the bed. Two hours later I had a new piece of linkage in my hands! It's a fixed length link whereas the original was an adjustable link, but hadn't been adjusted from its 15.5cm setting for the life of the car as far as I could tell... so nothing missed there. The new link is just one solid piece of plastic with snap clip ball socket ends.
Using PETG plastic filament... this stuff is tough and just flexible enough to make for a strong part that can snap over the balls and come back into shape. This plastic is immune to most common solvents and would remain strong in presence of the fluids found under the hood, even if soaked in diesel. And can withstand the kind of heat found in that area under the hood without softening.
It's a carefully designed ball socket using a diagonally split-cup. The link rod section is stiff enough to act as the pushrod needed to operate the lever it is working on. The forces on this link are always compressional (ball pushing toward the other ball). The springs returning the system to its resting place keeps compression on the rod even when you lift foot off the pedal.
A little bit of lube on each end, and the link is now driving the car. It's good enough to get me up and running again, so I didn't have to scramble ordering a more proper link. And won't any time soon. I think this one will wear just as well as the plastic ends of the original link. We'll check back in another 30 years ! ha !
I'll try to get the link posted up on
https://www.thingiverse.com/ just in case you need to print yourself one.
There's a few different linkages in the area that could also be done this way. Maybe I should design some on spec and print out as spares for next time I'm working in the area if another one breaks an end.