Anybody have a way to fix or nondestructively remove a loose knob? I replaced mine about 10 years ago, and now it’s loose again. As I recall, I ended up hacksaw blading the old one to get it off. The P/N is S1240-5, and the prices I found online were about $74. Pretty ridiculous.

Thanks

Sounds like a place for an owner produced part.

Alas, the price of a 3D printer isn’t in the budget.

jrc111 wrote:Alas, the price of a 3D printer isn’t in the budget.

I was thinking lathe.

Some public libraries actually have 3-D printers to use free.

My recollection is a bit hazy from 10 years ago, but IIRC, the attachment method is not threaded, but some kind of plasticy press fit. I could in fact probably spin something up in aluminum, but in the absence of threads, I’m at a loss in how to attach it.

jrc111 wrote:My recollection is a bit hazy from 10 years ago, but IIRC, the attachment method is not threaded, but some kind of plasticy press fit. I could in fact probably spin something up in aluminum, but in the absence of threads, I’m at a loss in how to attach it.

Remove old knob keeping the shaft intact. Grind a small flat area 1/8 from the end. Put on new know with socket head cap set screw in the side of it retained on the small flat area.

--Brian

Good idea! If I could get the old knob off without destroying it, I could drill across, tap it both sides, and use two set screws.

“ Some public libraries actually have 3-D printers to use free.”

Kids these days. Probably in the big cities; I suspect the learning curve might be a bit tough on seventy-year olds like myself.

jrc111 wrote:“ Some public libraries actually have 3-D printers to use free.”

Kids these days. Probably in the big cities; I suspect the learning curve might be a bit tough on seventy-year olds like myself.

I’m 52 and have problems with the 3D printer. When I get stuck I call my 21 year old..





—Brian

jrc111 wrote:My recollection is a bit hazy from 10 years ago, but IIRC, the attachment method is not threaded, but some kind of plasticy press fit. I could in fact probably spin something up in aluminum, but in the absence of threads, I’m at a loss in how to attach it.

The re-searched and found the image that got threads into my head, turns out it is a slightly different part number.

I think I’d try making something metal and using small set screws to secure it.

I had a loose primer knob on my Cessna 170. I was able to get a picture of what held the knob on from the 170 association forum (see link to thread below). Unfortunately it was just a ribbed fitting that once the overmolded knob let loose then there was nothing to stop it from rotating.

I ended up putting some thin CA glue in the joint and it is holding for now.

https://forum.cessna170.org/forums/view ... p?p=153806

i ended up buying the high dollar knob. Unlike the replacement knob I put on a decade ago, this one came with the ribbed adapter mated to the knob, and included the threaded portion. To replace it, the locking pin wouldn’t allow the old threaded adapter to be unthreaded, so I had drill out the center of the threaded portion after first cutting the ribbed portion off, Then the pin could be pulled, and the threaded portion unscrewed. I tightened the new threaded adapter into place, using the piston pin hole as a guide, drilled it slightly smaller than the pin, and with super glue added, tapped the pin into place. Unlike the C170 knob, there was no pin in the plastic knob portion. In retrospect, a transverse drill hole to fit a small roll pin in the knob would have probably worked.