service notes to a 1936 Leko

ship

Senior Team Emeritus
Premium Member
Been working on one of two 1936 Strand Pat. #73 a lot lately - squeek to the rear door like an old stove door amongst many antique details to them. It came with the shell, lens train with lens, horizontal shutters (advertised vertical assembly are missing), clear glass lens in a gobo type holder for a heat sink and it’s slide plate mechanism for mounting base assembly and reflector included. The other one with lens train and lens, horizontal lower shutter assembly and literally nothing else - total gizzard. This one is a even more of a problem in fabricating what it was or could do.

The slide plate mechanism on the primary fixture has a typical 1920's style PC fixture type reflector stud mount stand that was normally optional but theoretically important for this upgrade to Leko, and some well spaced out 1/4-20 holes that theoretically were to mount the lampholder assembly. This fixture is based off the Strand Pat. #43 PC fixture and theoretically uses it’s base parts including as research shows in common, a 1Kw Mog. Screw lamp (with medium screw lamp at less wattage available as another version,) and a 8" reflector. PC fixtures normally use Fresnel type reflectors.

I was missing all the important gizzards, instead someone for resale installed a 1950's style Fresnel slide plate/lamp mount and reflector assembly onto the reflector mounting bracket by way of threaded and cut off 5/16-18 bolt into the stud mount. Looked good for resale even if like 2.3/8" out of bench focus. Even came with some type of 50's Fresnel tubular P-28s lamp I think. Was working on it in a rush for a past show prop and welded a 5/16" stud to the upper part of the 1950's Fresnel lampholder assembly, this got me down to 3/4" higher than bench focus for the lamp. Check out the Strand Archive website, and one can see the zero info I was working with in making it work given before I looked at the 1936 Strand catalogue in the appendix of the Bentham Autobiography “Sixty Years of Light Work” that at least gave info about the gizzards. Dealers for Strand parts listed on the website also never replied to requests by me for info or parts. On my own with figuring out the gizzards for the fixture. Kind of like it that way, though would prefer working with something other than photos of what I have already to work with. Line of sight gets you so far, info about the gizzards gets you what you need.

Bought an older style 8" Altman Fresnel reflector for this fixture given it’s a PC with interesting Leko re-engineering of it. Altman still currently sells the older reflector assembly in addition the upgraded version with sub-reflector. Got a laugh out of my sales rep. over the phone in telling her what it was for - they know me and know I’m often buying parts for antique fixtures of even other brands. Unfortunately, the older style reflector was also upgraded at some point in seemingly not what I wanted. The old style 8" reflector I bought was a bit more shallow in concave than a proper old style reflector, and is mostly a 4.3/4" reflector with 8.1/2" reflector plate about it. Not a very concave 8" Fresnel reflector - this given it couldn’t have been too concave or one couldn’t close the rear door to the fixture.

TBA experiment of if that reflective 1.7/8" shell about the shallow reflector was in part why I couldn’t get a better hard focus. Could have been part of it, but I think not persay. Gaff taped about this ring around the reflector - only a 400w lamp and won’t be on long so as to confirm this observation. I think this weekend’s experiment was a failure in optimizing the fixture mostly due to the shallow refelctor and while it’s shiny shield probably didn’t help, I don’t think it the main cause. Think the new/old Altman reflector was too shallow in reflector. TBA that experiment. The lampholder is reasionably as far spaced from the reflector as possible already giving the 1/4-20 mounting holes for it’s sub plate front mounting.

For some reason I don’t understand, I think Altman is now making more shallow Fresnel reflectors which would require a little more distance between reflector and lampholder to optimize them. Fine with the halogen upgrades to do so in the globe not getting in the way, this as long as the lampholder were also placed further away in also requiring a larger distance, but not cool if attempting to replace an antique reflector with a new one in that the modern reflectors are not optimized for an older base unless you also buy the carriage for it I think. Won’t bench focus well. Saw it this weekend when I got a definate difference between the beam and field rings and could not bring them together. Was a beam and sort of hard edge definition between spot focus and it’s outer ring, but no real blue edge to the beam could be found by way of adjusting all three adjustments. Mounted the base as far away from the reflector as possible and up to the 1/4-20 bolts to mount it to the slide plate, but still could not get it away far enough.

Point of detail, there is the ½" gap between the seat height with even spacers, fiber pad etc, between where a Mog. Screw based lamp should seat at for LCL optically in the fixture, and what this 1/4-20 slide plate mounting for the lampholder provided me. That’s important in that ½" gap between how the real base was mounted and what was in between it and the slide plate could be a number of things and concepts. (There was something there I think.) Could be some form of elevation mechanism, could be a left to right type mechanism - don’t know, there was something there though within that ½" of space and this fixture is very complex already in what I have. I added a ½" plate of aluminum between the base and the lampholder’s various standoffs, insulators and fiber washers added. Functional in doing for the wire getting out of the base better and got me up to a more optically centered in the square opening center for light to get out by way of filament center. Given this fixture was designed about a screw based lamp and with very inaccurate filaments - there might very well have been in that ½" slide plate some additional mechanism so as tfor elevation of the base mechanism, and even a pivot point for adjusting left to right some. Until I find someone with a similar fixture that’s complete.. Don’t know other than by way of what I see.

Also of note, while I have a 1Kw G-48 Mog. Screw lamp, I don’t use it as it’s very old and would be very expensive to replace. Instead I have found that Mog. Screw to Medium Screw adaptors, when used with Medium Screw to Medium Screw socket extensions bring the commonly available and venerable in perhaps the oldest stage and studio lamp on the market - the 400G30/FL lamp right to about the bench focus - or at least within 1/8" of it dependant on how hard you screw it down, and that’s the concept with using any screw based lamps for a Leko anyway. On an old fixture, that’s not bad given a Fresnel reflector also. Something to work with at least. Optically, I adjusted for it also to some extent.

Given the lack of concave shape to the modern 8" Fresnel reflector, tonight I made an adaptor so as to make the 1950's 6" Fresnel reflector that came with the fixture work with the fixture optically on center. Already re-tasked that 5/16" stud that I got welded to the old 6" Fresnel, to mount with re-drilling holes, fit the Altman reflector, just a question of making a spacer plate in making this more concave older fresnel reflector fit to the now bench mark stud mounting bracket. Up by about ½" to center it.

With the deeper 6" / 4.1/4" but more concave reflector, I got a starting of a blue ring to a hard focus. Hard focus it is. Gotta adjust for like 1.5" worth of adjustment the lens train, and also the lampholder assembly for another like 1" worth of adjustment. Than in addition to that, the reflector in relation to the lamp has another like 1.5" in adjustment available by way of T-plate knob style with screw focus of some interesting design.

Still working on the fixture... Gaff taped about the what isn’t reflector part of the Altman 8" Fresnel reflector initially tried. Perhaps it was focused but way too much stray light was getting out of the fixture. It’s only a 400w lamp, and while in the past I have seen blackened frames to a reflector, I want to first try what it will do, before I paint it. Only a 400w lamp so if not on long, gaff tape should be sufficient to see what it’s like without the shell to the reflector.

Otherwise after this test, I believe I need an 8" Fresnel reflector - not a modern one but an ancient one that is more concave. Not so concave I believe in it bottoming out against the rear door of the fixture, but something different otherwise. So far I’m not working with what will have been an 8" reflector I’m told this fixture should have. Given this, I don’t know where the lamp was bench focused other than more to the front than I can get given mounting screws in the way for it going further. There is room up front in the square gate, but not much. Can borrow another from an ancient 8" fixture, but I’m not sure of it’s doing so value short of that missing ½" gap missing mechanism.

Still yet to try is the taped over shell to an older style 8" Fresnel assembly from Altman. This with the lampholder pushed as far as possible on sub-plate away from the reflector. This without spacer plate added in another inch of gap possible for a cut to make similar slide mech. to the same length based on where the reflector was mounted. Also yet to re-try the gaff tape reflector reflector to the proper mounting that wouldn’t with reflector, get me a bench focus edge.

Stuff more to try and working on it. Love re-creating and fabricating how it worked fixture parts. Re-engineering of fixtures is as enjoyable as design itself. Turn on the #73, and it in optimizing between lens train, slide focus and lamp to reflector focus knob, you get some form of blue edge with the deeper concave cone 1950's reflector than the 8" Altman reflector. Still not best or optimum, but getting closer in believing the deeper cone reflector was in use. The further away spaced other option in using a Altman 8" Fresnel lampholder and reflector in mounting the lamp further away also a concepet for this other #73 in re-producing parts. TBA if far enough away from the modern reflector to do any good and if the gaff tape was proper as it probably is in painting the shell of the reflector.

Stuff to try yet... Love these things and concepts of optics. At some point I hope to get to at least somewhat clear field and hard edge as a goal. This both for the gizzards with new stuff added to them I have, and the one for the other fixture I’m inventing from scratch.

White matt bench focus screen 14' away from the front lens of the fixture. Can’t do much better given a darkened room. Lots of stuff to try and experiment with including trying the further away adjusted Mog. screw base on a modern Altman Fresnel carriage. Got like an inch more room to better bench focus it if needed for more spot focus. Also the question of blackened ring to it or any factor at all in seeing.

Design thingie that captures my interest these days. Here I have this 1936 Leko net to me on the table, flip the switch and there is an almost blue ring to the focus after much adjustment to each of it’s three focus mechanisms. A lot of spill and halo, and while I have gotten a flat field at mostly it’s center for the lamp type, that flat field as with the spill doesn’t yet get a flat field. Might be that the 1936 reflector was a bit more concave than I think a 1950 version of it. Or something including this Leko just didn’t get that good of a beam. Instead with this reflector and the one before it, something one could work with. This I don’t know either - it’s a Fresnel reflector and step lens that is a Leko for term early in concept. Might not have been very efficient - though I think it possibly was and I need to try more stuff.

If interested, further experiments and work TBA.
 

derekleffew

Resident Curmudgeon
Senior Team
Premium Member
Well, I have no idea what a Strand Pat. #73 is, or what one looks like (but I might if one would post pictures)...

However, I am absolutely certain it is erroneous to refer to a luminaire, built by Strand Electric in England in 1936, and NOT using an ellipsoidal reflector, as a Leko!
 

ship

Senior Team Emeritus
Premium Member
Well, I have no idea what a Strand Pat. #73 is, or what one looks like (but I might if one would post pictures)...

However, I am absolutely certain it is erroneous to refer to a luminaire, built by Strand Electric in England in 1936, and NOT using an ellipsoidal reflector, as a Leko!

Fair enough and very much a difference in concept of ellipsoidal reflector spotlight, this verses bastardizing a Pat. #43 PC fixture into say a Leko that for all intensive purposes is the same optically or reverse of how one would focus it.

This is perhaps the first Strand Leko. I do have a similar year Kliegl Leko that's missing more parts but overall is much more advanced and with such a reflector. Science took a while to go by boat to other countries back than. This is a Strand Leko - though up for debate perhaps. Acts as a Leko, has similar stuff to a Leko except the reflector, Mirror Spotlight as per page 346 of the Bentham book, perhaps not a real Leko but does the job as best Strand could do perhaps in hearing about it. This is their 1936 Leko I think. Mine have more ocagional gel frame plates than what's shown in later model perhaps.

Still though, even given different reflector and square gate, it's a Leko only one reverse of it in concept in many ways - and lots of knobs to adjust.

Not the same reflector, but otherwise in concept in how it works and what one can do with it... I think it not the first Leko, but Strand UK's first version of a Leko. This given that is a Leko I think even if not ellipsoidal reflector spotlight as valid point.

Photos on the way.
 

josh88

Remarkably Tired.
Fight Leukemia
I'm glad I didn't hold my breath...

I do want to see this beast though

well given that Ship is leaving the site since he's dedicating time to his new child and family and this is more than 2 years old, continue to keep breathing and not holding your breath.
 

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