G-38 Lamp Socket Extenders

Discussion in 'Lighting and Electrics' started by ship, Jun 5, 2019.

  1. ship

    ship Senior Team Emeritus Premium Member

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    G-38 Lamp Socket Extenders

    So anyone ever used a E-26 (medium screw) lamp socket extender before, such as to make a 150w A-21 strip light fixture into a A-19 fixture in using the lower wattage more efficient lamps? This I did a lot back when Osram had a 100w halogen A-19 lamp. Even used them in combination with E-39 (Mog Screw) lamps in making them into A-19 lamp fixtures. Such as a E-39 500w ancient PC fixture, into a 400G-30SP lamped fixture in working correctly.

    Lamp socket extenders for the E-26 size somewhere back when they were invented, were designed so as to adapt and extend the seat height between one lamp to another. I don’t think by chance a A-21 fixture now with a lamp socket extender bench focus’s to A-19.

    So, today came up from a designer, he wants some 10Kw and 5Kw studio fixtures converted to 2KW lamps. 10Kw DTY (LCL of 10"), 5Kw DPY (LCL of 6.1/2"), converted to 2Kw CYX (LCL of 5").

    Last week I had a similar inquary for the first time in a few years about some 5Kw fixtures to be lampped at 2Kw, but they were fine with the lamps out of focus - they were prop lights. Been a few years since I did such a downgrade. Why pay for on-site powering up 5kW Dimmers if only wanting 2Kw of light, and bleed the amber shift? In the past years in doing this, I also had a lot more lead time so as to deconstruct the fixture and jack that lamp base up to it’s new proper seat height. And I did master that G-38 to E-26/A-19 lamp adaptor. (Still in works the P-28s to P-28s socket extender).

    Shorter notice these days in such projects, and more projects to get done.. But on the other and the current shop has metal workers and complete machine shop.

    First did a little research into if it’s been done already. Still waiting on Bulbtronics for reply, but it’s possible I can buy such a thing done. In the mean time I bought some male to female standoffs of appropriate size (in stainless and aluminum - neither would work other than for R&
    D.) Pins for a G-38 lamp are 7/16" Dia... and for the 5Kw upgrade I would need to jack the lamp up by 1.1/2" Thinking brass for a 2Kw lamp end result for the lathe. 10-32 set screw to secure to the CYX lamp pins.

    Unfortunately in checking ceramic spacers for insulators.... nothing like this.... but minds eye tells me there is stuff out there. Questioning if say porcelain knob and tube insulators are still on the marker and what sizes they are... as a for instance. (Have one in the hall of shame collection to pull out, but think too small.) Given that... My old Cotronics ceramic epoxy.... making an insulator mold for creating an insulator around the brass adaptor with set screw pin securing. As long as post-heat the ceramic epoxy after application... should have either for each pin would work. Would like to do a dual pin adaptor, but think that would be too much material short of cutting away and casting the actual ceramic cups to bad CYX/DPY lamps. Just too much epoxy ceramic in use to trust it won’t crack.

    Inspired. What am I not considering? Given fab shop is way too busy to make these adaptors for this project, but I think such adaptors will be useful to fabricate. What am I missing... grade of brass to specify? I know putting a set screw into the pins of a perfectly good CYX lamp (it’s hollow) will have to be done to a torque... perhaps two set screws. Also, stainless steel set screws would probably be best - while they don’t conduct as well... less chance of corrosion within the ceramic epoxy or brass.

    Set screws will be tapped into the brass so going 10-32 say other than pointed or cup point allows for the most pressure to the pin of the lamp without making damage to it. Install the set screws where the G-38 lamp socket has the least effect on it’s clamping for future use of the CYX lamp in a 2Kw fixture.

    Spray the formed brass extensions with electrical contact cleaner w. lubricant or apply Craig Deoxident with (copper). Molds and release will take me back to college, sand blast and blow off the exposed to ceramic epoxy parts I’m glueing to.

    What am I missing?
     
    Last edited: Jun 5, 2019
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  2. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @ship When you typed Craig Deoxident you probably meant Caig Deoxit; Caig, without the 'R'.
    Toodleoo!
    Ron Hebbard
     
  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    End up with something like (at least the spirit of) this?
    [​IMG]
    (Photo from https://www.controlbooth.com/threads/carbon-arc-followspots.32767/page-2#post-288306 .)

    Appropriately sized for the mogul bipost lampbase of course.
    .
     
  4. JonCarter

    JonCarter Well-Known Member

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    I don't know E26 from E39 from XX999, but as I understand it you need to mount a lower wattage mogul bipost lamp in an instrument designed for a higher wattage mogul bipost lamp. If you know the difference in LCL of the two lamps and you have access to a lathe, why not just turn a couple of "post extenders" with the correct male & female bipost dimensions and call it good? I wouldn't worry about insulating them; anybody getting inside an instrument such as this with the power on is a) kinda stupid or b) knows what the H they're doing and where not to put his pinkies.
     
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  5. ship

    ship Senior Team Emeritus Premium Member

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    You got the idea on the project, but not my style not to idiot proof this out of safety. I won't be the only person with access to it, or will even be using it.

    So if you turn a piece, the female socket needs to be a little over sized thus set screws. The set screws given hollow Mogul B-Pin as a type, I'm theorizing on which type and how many would be best to convey current. This for good connection to the lamp - but in a non-damaging way to the CYX lamp, should it want afterwards to go into a normal 2Kw Fresnel lamp socket.

    Anyway, just theorizing on a project... inventing something that I'm in pre-production with. Such an adaptor I'm told does not exist. "We always recommend they just jack up their lamp sockets." As I have done in the past. Problem is each brand and type of G-38 fixture is different in how to and difficulty in doing it. Created an interesting platform for a Stand which won't work on a Altmal or Mole. etc. Did platforms for some of the others also over the last 20 years. I'm tired of taking apart the fixture so as to jack up the lamp socket. I get a lot less notice about this these days in busy. An adaptor which will work no matter the brand.... Something I'm actively inventing. Thought it would be of interest. Just an adaptor, and not something I could retire on in making... but something appairently nobody else had done yet.
     
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  6. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @ship Mr. Shipinski Sir; how would you feel about tubular Teflon sleeves cut from a roll, or a four foot length, then simply slid over the exterior of your machined brass pin extenders? Would this offend your sensibilities too much to permit sleeping soundly?? You could add a little high temp glue to keep the Teflon tubing in place for posterity. For your set screws; possibly three or four around the circumference to grip from enough sides to keep things centered and electrically adequate without applying enough pressure in any one location to elicit deformation; I'm thinking dog or cup point set screws.
    Toodleoo!
    Ron Hebbard
     
  7. ship

    ship Senior Team Emeritus Premium Member

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    Teflon sleeve, interesting, will look into it thanks. Don't call me MR as I believe you are older and don't like that either. Ah' you mock me and have the right, still though I suspect you respect my safety standards.

    Set screw amount, I suspect you are hinting one is sifficient which was initial design. Cup point set screws I would rather not use, but otherwise.

    What high temp glue are you recommending? This if the sleeve which if of temp. would be much easier than casting a sleeve.

    Thanks.
     
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  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @ship Hello Sir! ;) (young 'un.)
    For the Teflon tubing, I'm thinking a 4' length of Alpha (Brand) from an electronic parts supplier such as Mouser would be straight upon receipt.
    Purchasing in 100' rolls would be cheaper per foot if you needed a larger quantity but the Teflon tends to curl a little after having spent time tightly wound on a reel.
    As for high-temp glue, I didn't have any specific glue in mind but was leaning towards a two part epoxy. I suspect you've got your own favorite high-temp glues.
    Set screws: I was suggesting one may be INSUFFICIENT, that possibly three or four would provide greater contact area with any one set screw providing relatively less pressure on the hollow pins of your lamps. If you're against cup point set screws, consider dog point.
    Toodleoo!
    Ron Hebbard
     
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  9. DrewE

    DrewE Active Member

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    What sort of temperatures does the socket see? Maybe some pourable/moldable silicone would be up to the insulating task; there are some versions readily available that can withstand temperatures over 500F (they are commonly used for making molds for casting low melting point metals/alloys).

    Gluing Teflon doesn't really work; it is, after all, very much non-stick. There a few techniques/systems available to chemically alter its surface and enable it to be bonded, but a cursory look-see via Google suggests they generally require quite nasty chemicals and/or specialized equipment that is not exactly commonplace...or maybe I'm just one of the odd few who doesn't happen to have some plasma etch apparatus gathering dust in the basement. Mechanical attachment is probably more practical, perhaps by knurling or ribbing the outside of the extender pins and having a fairly tight fit in the sleeves.
     
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  10. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @ship and @DrewE With the variety of ID's of Teflon tubing available from Alpha Tubing, would it be possible to stretch it just enough to press-fit on and, slippery as it is, have it retained by friction?
    Toodleoo!
    Ron Hebbard
     
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  11. ship

    ship Senior Team Emeritus Premium Member

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    Thanks both, each is much less messy and time consuming than trying to cast ceramic epoxy around the standoff. Good point on Teflon/glue, and in general I don't have a high temp glue I use other than high temp. silicone. Thinking Ron's idea has the best merits so far in not having to say injection mold the silcone around the pin so as to get something that looks professional.

    Theoretically if sized just right / denatured alcohol lubed to slip on, tubing would work & properly sized set screws would retain the tubing as with friction. Granted they would potentially be a touch point of contact for debate. Would have to look into... if say a 5/8" OD pin, or perhaps 3/4" pin, what wall thickness of the Teflon tubing is available in perhaps having the set screw stick up a bit from the brass, but still recessed within the tubing.

    On set screw type/amount... Dog point or cup point, as long as installed parallel to the filament axis, screw placement should not effect later use of the lamp in 2Kw fixture base retention - a concern. Dog point vs. cup point... I think cup point better, but with either I would have to specify a torque inch pounds for doing it properly. Not an electrical engineer... but I think I can safely for a 2Kw lamp figure that.

    Set screw type... brass and zinc/steel set screws I would avoid in too easy to break. Chrome possibly if available, but it leaves black oxide/alloy and say as best 316 Stainless Steel. Neither of the latter are optimum for conducting electricity. Given that, the intent of the set screws would be to push the pin of the lamp in the adaptor towards the inside wall of the opposing side of the adapter brass pin. Black oxide and 18-8 S.Steel rusts easier than 316 stainless steel.

    G-38 lamp pins have about 1" of pin length... trying to do three set screws into one might allow for less damage to the pin, and less torque; but it's a fairly thick pin. I'm thinking two set screws so as to equalize the pressure and point contact on it would have to be sufficient. Not enough material length left on the standoff part of the adaptor to prevent it bending with more holes. Softer material so you can't use 1/2 dia from an edge or double dia of hole to another hole concept.

    So 2x holes, cup point type 316 stainless, and dial in the ID tolerance of the pin socket of the adaptor so the on center alignment of the G-38 pins fitting into the 5 or 10 Kw lamp socket is not thrown off too much. Something to watch perhaps in not wanting to have too little contact surface area for the fixture lamp socket because the set screws forced the pins too close together and it was no longer approximately a 1.1/2" O.C. Distance between pins.

    Next onto an option for above mentioned 5/8 or 3/4" thick socket material. What if I went hex instead of round stock? Hex is initially a bad idea if I'm trying to fit a Teflon sleeve over it... but perhaps not. Toying with the idea in having a 1/2-13 hex prototype standoff to look at. Challenge is some lamp sockets are slightly recessed within the ceramic, but probably a problem with either adapter stock type in having to perhaps key cut a notch towards the pin which would help with alignment.

    Other thoughts.... way to bridge the two pin adaptors, so as to idiot proof the set screws (above key cut notch would probably fix this) going to the outside and parallel to the filament necessity in not damaging the lamp's pins in a way they would no longer work in a 2Kw fixture. As mentioned, such a bridge would be too brittle in easy casting methods. Perhaps a bridge too far in having the concept of a bi-pin adapter, instead of individual pin adapters.

    Thanks for the help and advice.... Interesting nobody has done this before. Bulbtronics checked (they have a lot of sockets/adaptors), nope. They as I was doing like 15 years ago when prop lights lamped down was popular, just said jack up the lamp base also. That was also at the time when beam projectors were re-popular suddenly. Than later large, prop studio Fresnel lights suddenly all wanted a moving light in them or a color changing LED (bench focused of course) in them. That lasted until this past week perhaps when someone again wanted a 5K Fresnel prop light, lamped down to 2Kw. They took the 2Kw lamps in doing out of bench focus condition. Not enough notice 1 day to adapt. Than this week where someone wanted a 5Kw Beam projector, lamped down to 2Kw but also in a rush to get. 5K fixtures got cut, took the 2K Beam Projectors. Possibly a coming trend again... In both ways. I have time so far, but want to get ahead of such a concept, especially if beam projectors are to be lamped down.

    Will see, but none the less... short of jacking up the socket on a 5 or 10Kw Fresnel to make it 2Kw - basically taking apart the fixture to do it, and some engineering of how to do it in properly supporting it. And given experience with Strand/Altman/Mole/B&M, you would need different Lamp Base standoff adapters for each fixture as none of the mounting cradles or lamp bases are similar.

    Plus possibly some re-wiring if not enough slack in the inside fixture cable. Than taking it all back apart after use. Spent hours adapting a Century 8x11 and the Kliegl Dyna Beam to 2Kw CYX so they could go in a VIP tent with antique lights with antique guitars one year. Would take too much time to convert them back to original lamps. Most likely future use of the lights, past sitting in the museum is a similar show where I would not allow the origional antique lamps to burn up hours for a demo or prop light. So they will just stay adapted.

    Such a standoff of the lamp itself, gets you a universal lamp adaptor which will work with any fixture brand. A 20A male stage pin to 60A ffemale Stage pin adaptor which connect to a 20A dimmer is easy to do. This as opposed to needing to take 5Kw dimmers and pay extra to power them up. And amber shift when dimming a 5K lamp would be short of the goal of a prop light in most instances.

    Thanks for the help, well on the way to a great adaptor. Will photo post when done.
     
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  12. JonCarter

    JonCarter Well-Known Member

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    Ship: Beware of set screws on mogul bipins! These are tubular (or at least in my experience used to be) and some goomba over tightening a set screw on the pin could either a) puncture it or b) cause flexing the pin to crack the seal between the glass & pin. How about turning the female 0.001 or so undersize and slitting the sides to grip the pins?
     
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  13. ship

    ship Senior Team Emeritus Premium Member

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    How about turning the female 0.001 or so undersize and slitting the sides to gripthe pins? Interested in your throughts, can you further let us know your thoughts in how to do that gripping the pins? Set screw to retain or other material and concept, or just slit sockets as per stage pin? Might need clamps to best for 2Kw loading - but was inithial thoughts for me.... where are you going in that in this concept for adaptor? Interesting and please refine. Thinking I have that covered but still debating amount of set screws etc. and concepts. Something of an idea you present to expand on in the concept of just slitting them, as per a great study in how to, and challenge.
    Appricieate and others especially as per perhaps the old timer project, in them getting and giving ideas in how they would. Thanks.

    Youngsters of all ages if they can follow the concept.... You Bet ya! pleases get in hear. We all have hope for you. Glad this became a difficult ducussion in how to. Thanks to all.
     
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  14. JonCarter

    JonCarter Well-Known Member

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    All of this is a nice discussion, but it may be a lot easier to just cut and install a block as high as necessary under the socket to raise t he LCL of the 2kW lamp to the proper height.
     
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  15. ship

    ship Senior Team Emeritus Premium Member

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    Yes easy and done lots of times before, Problem is each fixture type has a unique platform for the lamp base, and most have different lamp base socket types. Short notice... Found a Strand lamp socket extender,.. short notice, leaving in a few days - won't fit. Can do the jackup, but as said requires taking apart the fixture, possibly extending the wiring etc. Simpler to just jack up the lamp. This than is not a unique adaptor per fixture and does not require a lead time in converting and changing back after.
     
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  16. eadler

    eadler Active Member

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    I was thinking a bit smaller than that even. How do the original sockets do it?
     
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  17. ship

    ship Senior Team Emeritus Premium Member

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    Good question, but sockets are mostly spring or lever action and widely adjustable to any pin shape. Often on a 2Kw Fresnel, the warning is twist the base to relieve spring tention, but be aware that this lamp is coming out fast when you pull it out. Don't crash the fill pinch into the upper wall. Or relieve the lever and do the same, or loosen the wing screw. All above same notes in not crashing the fill pinch into the upper baffles of the light. Specify that because done a lot, especially if a stuck lamp to base. Over 20 years with 2Kw+ Fresnels.

    Be aware of this in positioning your hand so pulling it will only provide only so much travel. Same with other bases in recommendations.

    There is no defined ID of a socket given spring or wing screw tention.
     
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