"I don't have gear to develop 70mm film, or usable spools"
I will outline how the inner MacGyver can be unleashed with this story of film fiddling.
I was appalled at the price to buy some c-41 120 film locally a few years ago ($8.95 per roll for Kodak Portra 160NC at a Henry's, which is a big camera chain store around here).
So I got on the *bay and won 100' of 70mm Portra 160NC. The goal was to cut the stuff down, and reload for a much better price (material cost was something lie $2 per 120 rool).
I have been saving spools and backing paper for years, enough to keep an old otherwise empty 250 sheet 8x10 paper box full. The backing paper has been great for creating impromtu darkrooms from time to time. So I guess that is why I keep the stuff around, and the easiest way to save it is on the spool it came on.
Well, it turns out that slitting is quite feasible and rerolling is possible, but I subsequently found a cache of 120 from a commenrcial photogrpaher for less than $2, and so the bulk roll languished in the freezer for a few years.
Then this old Brownie, and an old Polaroid J66 came to me as a gift.
The brownie works on 70mm almost perfectly, and the apertures and shutter work well exposing 100iso film outdoors in the summer.
I made spools up from 35mm cassette spindles that were cut in half and had 'sitting in front of the TV whittling' hardwood dowels fashioned to make the spools extend to suit 70mm wide film.
The end of spools did not suit the drive key. I got the hot glue gun out and loaded it with slow cooling funiture type glue sticks.
I coated the drive key with a dab of vaseline, then loaded the just glued spindle end in alignmnet, and pushed the drive key in, and pulled it out again.
I fixed up any distortions from the key's extraction with my x-acto knife on the still soft glue mass.
I had no 70mm backing paper, so I load the 75 mm rolls only in the darkroom.
I worked out how many turns of the winding key to fully advance the fim by loading the film spools with old 120 backing paper, and mark it up with markers with the back open
For development I have a Paterson two piece reel and single tank centre spinde that I have adapted with rubber bands and self amalgamating tape to end up with a reel that is just far enough apart to suit the film.
I place it uncut on a glassless 4x5 neg acrrier with one edge in the edge of the carrier. I stop down and the thing projects fine, compared to the crappy optical quality of the Brownie lens.
The Polaroid was a more radical mod. I added a take up drive bolt to wind the film. It yields a better image by virtue of it's better lens, and have found instruction on the web of correlating the lightmeter settings to the aperture setting needed to give a balanced exposure witht he automatically adjusting shutter speed doing most of the correct exposure work.
The 70mmx 4" negative from it is a fair bit more crisp than the Brownie, but the Polarod sold for a hunk more money in it's day than the Brwonie was a few decades earlier.