This another of my hairbrained schemes!
Both the Voigtländer Heliar and the large F.4 Epis projector series from Leitz have the first triplet design from Cooke (T,T & H). The central -ve lens is quite close to the rear lens in both products. The Heliar differs in that the front and rear lens are cemented doublets, rather than the simple meniscus lens of the "Epis". However, this was considered good enough for Cooke!
The Heliar Universal has the same basic design as the Heliar, but the central lens can be moved forward separately to achieve increasing degrees of "softness".
My thought was to modify the mounting of the Epis so that the focussing device (angled slot) would just move a shortened barrel, with the rather complicated central central lens mount, forward. The front and rear "cells" could be mounted to the sleeve to maintain their original positions.
Most "Epises" have a full length sleeve. A nice clean example can be seen currently, with better than average photos, at E**y 320880872634.
I do not know the seller - pure co-incidence! This is exactly the same Epis (F.4 and 400mm) that I have cut up.
This is basically a hacksaw job on the barrel. First cut off the rear cell complete with a section of barrel, Then do the same with the front cell.
After this, remove enough of the largest piece of the barrel containing the -ve lens to allow it to come right behind the front lens when the focussing slider is moved. The front and rear cells in a section of the cut barrel can be mounted using grub screws. Access for lens cleaning must be kept. The sliding shorter barrel does allow some light to enter from the side but doesn't influence focussing and a piece of dark cloth can be held over the lens. The system certainly works, although I think some kind of liner is nesessary to smoothen up the movement - shorter barrel means more "yawing". A very different image appears as the middle lens shoots forward. I will post some paper images and compare with the real thing as soon as I can. And using front stops as well.
The reason for doing this is because I had an Epis lying around and I know there are others that have one (also unloved and unused) as well (see previous Epis posts) and this might be a good and economical way of approaching the effect achieved in the real article. And at very different price. One good thing is the Epis flange is an integral part of the barrel so they are never lost.