Originally Posted by 75Chinook
Any suggestions for tracking down that run channel?
Quite likely it is this flexible glass run channel.
You need to measure the inside width and height of the channel it fits into, the height is not as critical as the width. You can measure the thickness of your glass, I believe 3/16" glass was the common size for that era. Various companies sell this felt run but I suspect they are all getting it from the same source. Use the keywords and the dimensions to look for prices from various sources elsewhere such as Ebay. Even if you don't need 100' of it there will be others with older trailers with sliding windows
such as my Trailswest Campster
that use this size of channel. That means you could sell the leftover pieces long enough for their windows
in this forum's classified section. At this point in time all this original material will be rusted out in the 1960's early 1070's trailers that used this in their sliding windows
To remove the rotted felt and put in a new piece I had to take my window out, then remove the rivets holding the frame together. Use a large spreader bar clamp to gently open the frame wide enough to take the glass out. Work carefully on top of a padded table while you take the glass in and out of the frame so you don't break it. Scrape all the old felt run out of the channel and put in the new felt. Reverse the disassembly process using the heads on the bar clamps turned in the other direction to pull the frame back together. Then get the shortest 1/8 stainless rivets you can find and put them in. Pull the new felt out of the way while installing the rivets. Use a Dremel motor to trim the rivet length back to barely protruding (but still holding the pieces together). You don't want it bumping into the glass or overly distorting the felt track too high. Best of luck to you! I did this same process on my sliding windows and it turned out just fine.
One thing to note, on the fixed pane in my windows at the bottom inside the track there were some little plastic channels that elevate the edge of the glass. They do two things, cushion the glass edge and elevate it so that water can run underneath it and on out through the weep holes. Very important, when you put these pieces back in the channel to be sure they are not located in front of the weep holes thereby blocking them. The originals on mine were made of styrene plastic and were in very poor condition so I 3D printed some replacements as I could not find that size of plastic channel anywhere to purchase for cutting to length. The new pieces I 3D printed from ABS plastic are much stronger and have a tiny island of material in the center to help keep the glass from making the channel sag in the middle. I am happy to share the 3D print file with anyone who needs to replace these in their sliding window track.