Conventional Fixtures Lobsterscope !

JD

Well-Known Member
OK, I have to object! (said with a smile) I am in the process of putting one of these together. The application is to produce an "old movie" effect for a musical number done in a show. For fun, I looked it up in the CB Wiki and found this: "Archaic method of creating a strobe effect without using an actual strobe unit." Cut the poor Lobster a break! The look is far more mellow and comical. As archaic as it may be, the look is far more fitting due to it's very shortcomings. A strobe has a much harsher look. The poor Lobster needs to at least be dignified as being a device in it's own right, not just something thrown to the warehouse shelf and replaced by xenon strobes ;)

Come on, old-timers, give me some backup here ! :lol:
 

derekleffew

Resident Curmudgeon
Senior Team
Premium Member
...a device in it's own right, not just something thrown to the warehouse shelf and replaced by xenon strobes ...
Ah, but that's exactly what happened, in the mid-70s when electronic strobes became widely available, thanks to Diversitronics. It seems everyone except Limelight found the shelf space more valuable.

Okay, JD, here's a deal: I'll remove the word "archaic" if you can satisfactorily explain why one slot must be elliptical and the other S-shaped.

proxy.php

Lobsterscope: What is it?
 
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JD

Well-Known Member
I had one of these for my old Trouper. I remember asking that question to one of the guys from the old Aladdin Lighting. His answer, which made sense to me at the time, was that the two flashes were designed to be different durations but not of a different brightness. An old friend at McManus had a different take. The deviation was designed to add a vertical modulation to the flicker. (A trick on the eye to simulate old projections.)

I have always accepted these answers, but as to inventor's real intention.... :confused:
 

gafftapegreenia

CBMod
CB Mods
Well I learned something today. Thanks CB.
 

JD

Well-Known Member
Wow, I was just doing a bit of googling and came across the most amazing site!

A History of Light and Lighting

"A History of Light and Lighting" It has every source from striking a match to the introduction of the Varilite ! It even covers Salt Water Dimmers !
 

gafftapegreenia

CBMod
CB Mods

Jen

Member
Lobsterscope....

Hey guys! I am trying to make a lobsterscope, I have researched the project but I only vaguely have an idea of how to make one. I would like make one out of wood and be able move it manually. To make one out of metal would be too expensive and we do not have all the material resources (plasma cutter etc.). I also do not know if there are any specific dimensions for it. Please help, it would be much appreciated.

Best,
Jen
 

MPowers

Well-Known Member
Re: Lobsterscope....

PLASMA CUTTER???!!! What for? 22ga sheet metal and a pair of hand snips will do the cutting. When they made lobster scopes for limelight spots in the 19th century, I guarantee there were no plasma cutters to make the discs! Believe me you have all the tools you need.

Just a question, why are you trying to make a lobersterscope? Class project, historical investigation, etc. etc.??

One of the biggest problems is creating your cut-out disc in an exact mirror image pattern so it is evenly balanced and doesn't try to wobble, shake and tear itself apart. Lay out your pattern in any cad program, this will let you create an evenly balanced layout. Spray adhesive the full scale pattern to the sheet metal and proceed to cut. If you use hand snips, drill, hole saw etc to open up the center of the openings and make a series of cuts to within about 3/8" of the finish line, then snip to the corners and then make the final cuts. Note hand snips come in left and right hand styles with the blades over lapped in the opposite direction and they make curved cuts in one direction better than the other, you should have a pair of each.

A couple of quick metal cutting bits of info.

Armour Archive -- Essays: Sheetmetal Cutting Tools by Sasha

How to Cut Sheet Metal | eHow.com

Other ways to cut sheet metal is with a Scroll Saw, sabre/jig saw and band saws, using the appropriate metal cutting blades of course. Scroll saws and sabre saws can cut inside holes, a band saw can cut only out side holes or you have to make a cut through the edge to the inner cutout and patch the cut later. with thin sheet metal the best way to make the cut is with a blade that has the finest tooth available and then adhere the sheet metal to a piece of 1/4" masonite or other very smooth wood or hard board. Best way to adhere is with wax. Plain old ordinary wax. Heat the wax to a liquid and pour a very thin layer on the wood lay the metal over it and then using a heat gun or plug in a fresnel and aim it at the metal from about 3' away, soften the wax and now the two are adhered. The point of the wood is to prevent the saw blade from grabbing and ripping or tearing the thin metal during the cutting process. The point of the wax is when the cutting is done, a little hot water bath or a heat gun UN-GLUES the wood and metal cleanly with no residue and you don't risk bending the thin metal while peeling it up. Note: drill your center hole for the axle rod while it is still attached.

Next, balance the disc. put it on a rod you can chuck into a drill and spin very slowly. check for wobble and play. The heavy side will tend to swing a little wider than the light side. Use a grease pencil and as the disc wobbles, bring the pencil up until it just touches the edge of the disc. Mark the start and stop point of the pencil mark. Now drill an 1/8" hole near the edge of the disc on the center point between start/stop points, or alternatively put a 1" strip of gaff tape on the light side directly opposite the pencil marks. Work in small increments until the disc can spin without wobble.

A couple versions of a scroll saw are:

Delta 40-690 20-Inch Variable Speed Scroll Saw

Rockwell RK7315 16" Scroll Saw, 16" Scroll Saw

Buying Guide: Scroll Saws

There are so many ways of connecting your disc to a drive motor, so many suitable AC and DC motors available, I can't begin to describe them all. You'll have to do a bit of design and engineering yourself. Some small motors have a shaft with a threaded hole in the end and you can attach the disc directly to the motor. You can use very small V belts and pulleys, lots of choices.

Now, Note most of the directions will also work with wood except for the hand snips. If you use a wood product I strongly suggest 1/8" or 1/4" hardboard (masonite) rather than wood or plywood. The composite material is more uniform in weight from point to point and will be far easier to balance and sanding down the edge is a balancing option. For hand cranking, think belt drive. You'll need some small pillow blocks to support the drive shaft for the disc and the same for the shaft attached to the crank handle. Small belts and pulleys look at McMaster, Grainger, Tractor Supply and of course the big box stores. I would try to shoot for about 4:1 ratio with your pulleys, i.e. one turn of the crank makes about 4 turns of the disc. So a 1" pulley on the disc would be a 4" pulley on the crank handle.

Good luck!! Hope this helps a bit.
 
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derekleffew

Resident Curmudgeon
Senior Team
Premium Member
Re: Lobsterscope....

[The two posts above have been moved here from another location.]

Click on the wiki entry lobsterscope and follow the links. Regardless of the material used, the most difficult part will be the size, shape, and locations of the two openings (see posts2&3 above). Jen, if your research leads to any mathematical calculations or explanations of the why and how of these shapes, we'd love to see it.

lobster_scope_front_sm2.jpg
 
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JD

Well-Known Member
Wow! The Lobster-thread is back from the dead!

I made one tracing a real one (off the trouper) and have to say the balancing act is a real challenge. Even at about 5rpc (300 rpm) it's a real wobble problem. Forget the old movie frame rate, think it was 15fps, which actually requires 7.5 rpc (two openings.) Ran mine at about 5 for best effect.

The old "Times Square" used to make something called a "color strobe" which was basically a bulb in a metal box with a rotating color wheel behind a port hole in the box. You could take out the gels and block off two of the holes and put the templates in the other two. (Think I used cat food can lids to make the templates.) Stuck a BEP photoflood in there. Worked ok.
 

MPowers

Well-Known Member
I have seen them with both slots being the same shape, usually the "S" shaped form. I can see no reason for them to be different other than "design look" .

I made one when I was an under grad, early '60's, no such thing as electronic strobes then. Mine had two identical "S" slots, the rented one had the different slots, couldn't tell any difference in use.
 

JD

Well-Known Member
I have seen them with both slots being the same shape, usually the "S" shaped form. I can see no reason for them to be different other than "design look" .

I made one when I was an under grad, early '60's, no such thing as electronic strobes then. Mine had two identical "S" slots, the rented one had the different slots, couldn't tell any difference in use.

See post number 3. For now, I continue to believe that, at least until a better explanation comes along. Possibly time to research the inventor, maybe able to get some more info on it.
 

MPowers

Well-Known Member
-I too heard the same explanations over the years. But as I said, using the commercial model, different holes, and the shop built model, identical holes, side by side, on the same stage at the same time, we could not find or see any discernible difference in the effect.

I too would be interested in any empirical evidence in either direction.
 

ScottT

Lighting Programmer
I'm in the process of building one right now that just might work. But if it doesn't does anyone know where I can buy/rent one?
 

Lightguy5

Member
And another resurrection to this thread.
I'm researching "On The Town," and the CD liner notes talked about "lobster box" lighting for the chase scenes. Of course Google and YouTube had nothing so I came here.
Not only do I find out what it is, I also find out what that strange wheel contraption that I have kicking around my shop is!! Yes, I have a Lobsterscope!! And it has the different shaped holes.
Now, What fixture to use....?
Suggestions?
 

MPowers

Well-Known Member
.......I'm researching "On The Town," and the CD liner notes talked about "lobster box" lighting for the chase scenes. .........
Not only do I find out what it is, I also find out what that strange wheel contraption that I have kicking around my shop is!! Yes, I have a Lobsterscope!! And it has the different shaped holes.
Now, What fixture to use....?

What instrument to use??? Depends on whether or not the audience will see the unit in action. If not, then any variable speed strobe unit will do, as you have found out by now, a lobster scope is simply a mechanical strobe light. The effect was often used with carbon arc followspots.

If the effect is to be in view, then any unit that predates die cast LeKos will be period enough. The main thing is any ERS would be the stove pipe type, not axial. Fresnels have been fresnels since the early '30's so you can't go wrong there as long as you stay away from die cast or punch press shaping. So, mainly go with sheet metal housings, square corners, and NO ETC logos.
 

JD

Well-Known Member
Three years later and I still defend the mighty Lobster!
Yes, strobes work fine and are easier to implement, but there is a vertical motion flicker on the lobsterscope that gives it a different look to the eye. It has it's nitch place, although most often it ends up on the shelf.

The strobe lights the whole area on each flash, the lobsterscope sweeps the field of view on each "flash."
 

Brandofhawk

Active Member
This thing is pretty cool. As a young designer, I'm just gunna take the knowledge that its out there, fold it up and stick it in my pocket for later use. I <3 CB.
 

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