Brain Teaser (or maybe not!)

Bob Metzger · Post by **Bob Metzger** » 25 Feb 2003 4:18 am

Here's one that puzzled me:

I recently decided a change (actually, a lower) that I was making on a knee lever was best made on another knee lever so I switched it. I notated the hole in the puller finger (5 holes per puller finger on my Sho-Bud) that the pull rod went in and the hole in the changer (triple raise, double lower) that the rod went thru. I also measured the amount of knee lever travel and set the new lever to the same. I set it up exactly as it had been, only now on another lever. The change on the previous lever worked perfectly, with only moderate pressure. However, I had to raise the rod to another puller finger hole for more travel and lengthen the knee lever travel at the stop to get this change to work in the new position, but now with now much greater pressure. Why? FYI, the old bellcrank was farther from the changer than the new bellcrank being used, by about 3 inches (adjacent bellcranks). The new lever is a vertical; The old was a left knee mvng right.

Bob M.

Jim Smith · Post by **Jim Smith** » 25 Feb 2003 7:49 am

Sounds like the difference in stroke was caused the different leverage between a direct pull and a reversing knee lever. Also, other pulls on the same lever will affect the stiffness of the pull.

Bob Metzger · Post by **Bob Metzger** » 25 Feb 2003 2:27 pm

How does the changer know if it's a direct pull or a reversing pull? Doesn't it only know the distance the uc rod travels and how much it pulls the changer finger?

No other pulls on either lever.

I'm still stumped!

Bob M.

Gino Iorfida · Post by **Gino Iorfida** » 25 Feb 2003 3:28 pm

Well, at least on the old MSA style changers, a reversing lever has multiple bellcrank holes that you can select with the combination of rods, so a mechanical advantage/disadvantage can be adjusted...