Dumbo The Flying Elephant

[Cglrcng]

Originally Posted by Larry Hill

I bought this nicely done engine part and it gave me some flexibility in tuning. I installed it but couldn’t get it to repeat. Even the face runout would not repeat. I checked everything and everything checked good. Long story short, the dowel pin was protruding out far enough to make the hold down bolt washer apply in uneven force to the cam gear causing the runout to be everywhere.
A lot of times the parts are smarter than me.

I would say you found that issue, so you were actually much smarter than the dumb parts. Did you choose to trim the dowel pin to alleviate the runout measurement issue? Maybe report what you found to the parts mfg., so they can at least attempt a workaround on that cam timing gearset? Just saying.

On some of our robots in FIRST, some of the transmission gearsets for our wheelsets we always, take to the mill when new and face the center contact surfaces, and all washers and bolt faces to make sure that both faces on each gear are flat and true so each gear meshes correctly centered on each gear they mesh with throughout the gearset speed ranges. They are rarely machined perfectly to our liking until we trim or face them up. Once we do, they work a ton better. And rarely do we see washers that are truly flat or true until machined flat on both sides as they are usually just standard punched parts. We will often use a stack of thin flat stainless steel shims to replace a cheap steel washer under the head of a centered gear bolt, and it will often make a perfectly faced gear run and mesh more true with less runout. Some of those gearboxes are 3, 4, or 5 speed transmissions where one main gear has to move outward against perpetually smaller, and smaller gears, and if that main is not perfectly square, it will not mesh correctly and quickly when shifting both up and down through the selected range.