I meant to ask this long ago after I took apart the tuning mechanism of a 38-7 for cleaning and reassembly. On one of the larger gears in the assembly, there are a few 'slots' cut into the otherwise solid faced gear. In each of the 3 or 4 (don't recall how many) slots, there is a small spring inserted into each. Anyone know the purpose of these and what exactly they are intended to do? Why this popped in my head after all this time I'm not sure
Maybe you can get an idea from the assembly drawings? You may be referring to the Pawl Spring, part No. 23 in drawing?
See the CONE-CENTRIC PAGE on my site:
http://www.philcorepairbench.com/conecentric/index.htm
See the three PDFs on this page for dial assy. Never had one in my hands, so I cannot help from person experience. I think Ron has though....
Chuck
Nope not the pawl spring - it's the larger gear behind the dial assembly that ultimately drives the tuning cap. I don't see the part on the 3 PDF's, but you can see the gears depicted somewhat on the first illustration you reference from the Mallory-Yaxley document. Just looked at vintage-electronics.com and found a similar part shown as "Philco 37-116 Tuning Assembly Part - Vernier drive GEAR". If you search for that part, it should pop up with a picture. On the 38-7, I don't believe the springs contact anything whatsoever and can't imagine that the gear "twists" out of shape requiring them. But then again I'm no mechanical engineer either
I have seen this on more contemporary radios and such. The bigger gear with the springs was actualy a pair of thin, stacked gears. The springs pushed against each half so there would be a snug fit to the smaller gear to eliminate the possiblity of "dial slop" and give a smooth feel while turning. The range of push was only about half a tooth.
Hope this helps.
Dave C.
Ahh! I'll check that later - I assumed it was one gear but didn't check that close. I knew there had to be a reason
Thanks!
That type of "split-spring" gear is called anti-backlash. Keeps the gear teeth tight during meshing. Like was mentioned; takes up the slop.
Those split gears are tricky to seat properly. You have to push the smaller gear that meshes with the split gears in far enough to engage the split gear closest to it, but not the split gear that is further away. Then you have to rotate the farther gear one tooth and slide the smaller gear in further so that it engages both split gears. Kind of a pain, especially in cramped quarters.
Bob