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Conventional Fixtures C-Clampery

Discussion in 'Lighting and Electrics' started by derekleffew, Dec 24, 2008.

  1. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    What better time than during the dark days of winter to take a look at refurbishing all of one of one's hardest-working pieces of hardware?
    [​IMG]

    More or less standard parts nomenclature:
    [​IMG]

    Pipe Bolt: 1/2-13 x 3" Cup Point Square Head Set Screw, ~$1.22/each.
    Pan Screw: 5/16-18 x 5/8" Cup Point Square Head Set Screw, ~$0.14/each.
    Yoke Bolt: 1/2"-13 x 1" A307A Low Carbon Plain Finish Hex Bolt, ~$0.39/each.
    Washer: 1/2" Flat Washer
    Lock Washer: 1/2" Split Lock Washer
    An alternative to the two items above:
    Belleville Washer:
    1/2" Belleville, .512 X 1 X .039, 1050/1070 Plain Finish, ~$0.76/each.
    I highly recommend the Belleville washer instead of the flat and lock washers. I first learned of this due to the Mega-Clamp, which does not have a Pan Screw.


    For those wondering what prompted this...I refused to believe the stagecraft mailing list when it was said that 1/2" I.D. Schedule 40 steel (sidearm) pipe would not fit in an ETC C-Clamp and thus Altmans-only must be used. I had to see for myself, and yes Virginia, it's true. [edit: ship said it here on 11/01/07, but the wheat must have gotten lost in the chaff.] I love sidearms, and am very disgruntled at ETC right now, especially since they've kept this a secret from me for sixteen years. I suggest everyone purchasing new fixtures to try to get his/her dealer to substitute a Mega-Clamp at no extra charge.
     
    Last edited: Dec 28, 2008
  2. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    *gasp*

    ETC how could you.
     
  3. avkid

    avkid Not a New User Fight Leukemia

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    That makes no sense, why????????
     
  4. techieman33

    techieman33 Well-Known Member

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    We replaced all of the pan bolts with altman t-handles so we don't need wrenchs to focus, it makes like a lot easier.
     
  5. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Even if you do replace the Pan Screw (what a nice PC name for that part) with a T handle you still need a wrench because invariably the yoke bolt always comes loose.
     
  6. willbb123

    willbb123 Active Member

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    I love my mega-combo wrench. But there is always one instrument that the pan bolt is a different size, so I always keep a C-wrench in the lift.
     
  7. SteveB

    SteveB Well-Known Member

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    Some late thoughts on this.

    The traditional C-Clamp has been in my mind, an engineering and practical weak point in the entire "package" that makes up a lighting fixture. I prefer the ETC version as I believe (with no actual proof done thru testing) that it's stronger then the traditional Altman-Century copy. The ETC has an added ridge on the back side that I believe resists breakage of the cast iron. I have had this problem on (rare) occasion with the Altman-Century versions, a result of zealous technicians over tightening the pipe bolt, and is why I dislike using these clamps on side arms that support anything other then a single lighting fixture.

    The newer Altman heavy duty clamp is a POS, and I have had issues with less experienced technicians failing to assure that the clamp is properly seated on 1-1/2" OD pipe prior to tighting the pipe bolt, with the result that the clamp is often hung loose. When used with 1-1/2" OD pipe, with the Altman HD clamp properly seated, the pipe bolt is not perpendicular to the pipe, causing torquing of the clamp. Not a good design.

    I like the Mega Clamp design as well as the concept behind the Bellville washer, but would not go thru the added expense of spec'ing Mega Clamps in place of whatever comes from the factory, as the factory ships the regular clamp anyway, it's free and works OK. Plus I have a building full of older style Altman-Century c-clamps, the result of replacing older Altman and Strand eqpt. with ETC, while keeping the older c-clamps. Thus I never have issues with the ETC clamp not accepting a 1" steel pipe to be used as a side-arm. All my ETC clamps went on fixtures and with a ton of Altman clamps, can build up whatever I need.

    If I were ordering side arms as new, I would buy the Mega Baby instead of the Altman as it's the same price and is a better built unit.

    My $.02

    Steve B.
     
  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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  9. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    I HATE the Altman heavy duty clamp.
     
  10. SteveB

    SteveB Well-Known Member

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    And I think that ETC should get out of the c-clamp market and simply provide a Mega-Clamp with every fixture. One problem though is the Mega-Clamp will not accept a 1" OD steel pipe either (referring to Dereks OP), so while you get a good c-clamp, as well as NO F _ _ K ME NUT to deal with, you still end up making your own STSA's with Altman clamps, or buying them new.

    SB
     
  11. ship

    ship Senior Team Emeritus Premium Member

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    Remember that I also specify Sch.80 pipe for a side arm.

    Altman Heavy duty clamp, some version between the normal and the HD, or the ETC.... all a question of use. On clamps, I don’t think one should have the need to require a specific clamp - when in question, one is using the wrong clamp or side arm if using it where a question of one being too weak as a side load over others that are also more vertical hang designed. Say using a cheseborough pipe instead of clamp that’s no matter the type not so much designed for out rigger in concept. Got this Major sort of like cheseborough studio clamp ½" Sch. 40 side arm from years ago which while it failed says in the past there was also another concept in doing these things years ago and the normal side arm is more easy solution than design thing.. Also have another which has a bracket around the C-Clamp to reinforce it.

    Just because you can, don’t mean any are designed for this sort of side loading under torque including the Mega Clamp. Use Mega clamps for hanging vertical lighting ladders - a sort of truss like thing, other than that, nope no side arm.

    Heavy duty Altman clamp... Which would better hold more weight, the ETC or heavy duty Altman... did you test either in deciding which is better? IN hanging on 2" Sch. 40 pipe as at times found the Altman HD clamp is much more useful at least.

    For an 8" fixture or larger, at least as it seems ETC going more heavy duty or the HD Altman is only what I would use. ETC in not going Sch. 40 common size most others are for a side arm extension I would say is more a safety thing and good idea for them. Why have the liability of bent or failed clamps used for something they are really not designed to be best for in extension clamp? Altman simply follows the former standard of what size for a hole in what was done in the past but in a world of Darwin in not persay the norm in safe. Once had someone hang a nine light PAR 36 audience blinder off somewhere like a nine foot 1.1/2" Sch. 40 extension from a truss. The pipe bent in time shortly after load in and the I.A. and house wouldn’t allow another side arm for the use before an engineer signed off on the loading. Safe enough for them and also something I agreed with in the pipe bending and not something I would agree with doing. Who on a ½" Sch. 40 pipe can say what weight to hang off it before the pipe bends or the clamp fails, this especially as I normally did years and years ago in climbing the boom, climb by way of clamp to the boom so as to focus.

    Side arms’ Most recommend instead a cheseborough type outrigger to hang the fixture vertically from and I agree in most instances. Where simple and quick, only a side arm with Sch. 80 pipe in it and short say 30" extension I also agree with. Clamp failure... don’t matter a brand, none are side load design in the end for a side arm, only a proper side arm for cheseborough and pipe for this purpose where at all possible.
     
  12. ship

    ship Senior Team Emeritus Premium Member

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    In servicing clamps, first it’s re-tapping the threaded holes. If especially that ½" hole has it’s set screw mushroomed out, I’ll cut it off before I’ll have that strip its way thru the clamp. Screw threads are very important. Bit of WD-40 on the clamp and threads, a bit of re-tapping, bit of wire wheel on the bright work parts of the clamp, and tap/die the rest and it is normally fine. This within reason and all fail or bend and need to be removed from the inventory after a point.

    After that, I’m a big fan of washers and fiber washer plus removing and replacing even the ETC bolts. I prefer a main bolt that’s 1.1/2" thru 2" in 1/2-13 hex over something that’s 3/4" thru 1" long often provided with a clamp. Rusted bolts and set screws get often replaced assuming condition, grade five on all bolts mostly used. For the question of washer verses lock washer used between spud / yoke and head of bolt I often don’t care about. Between the yoke and the spud on the other hand, I do add a hard fiber washer in this place. This acts as if a ball bearing in tightening as you will, the fiber washer will still allow you to rotate the fixture sufficient to not need to adjust the pan screw in most instances.

    Belleville washer... Don’t see a need for one in you are not locking down some focus that will never need to be adjusted again or in needing a big 10" Crescent Wrench to tighten down fully to locked down position.

    Simple normal spring lock washer often over normal washer tightened 1/4 turn past hand tight with the fiber washer and that’s good enough.

    On servicing, again, I’ll brighten the bright work by way of WD-40 and wire wheel, than rub it into any rusted cast surface. Than on pipe bolt, dependant on condition, replace or re-tap it’s hole and bolt and the same with yoke bolt except often just replace it’s bolt. Pan Screw, tap and as neededed replace or run it thru a die also. All with thread cutting oil.

    Where stripped, it’s trash.
     
  13. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Seems like if all pan bolts were replaced with T-handles, and this

    [​IMG]
    Premier Lighting-Clamps added to all pipe bolts, wrenches could ALMOST never be needed.

    Has anyone ever used the above pictured device? Worth $2 per clamp?

    [Edit: the same, or a different?, version:
    [​IMG]
    http://www.productionadvantageonline.com/Clamps-Safeties/MUT HANDLE.aspx (MUT Enterprises is best known as the manufacturer of the PinSplitter II.)
     
    Last edited: Jun 18, 2009
  14. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Another pipe bolt handle, this time from The Light Source, is the Mega Handle

    [​IMG]

    It is intended to slip over the bolt and stay with the fixture.

    It is similar, but quite different in application, from the Mega Combo

    [​IMG]
     
  15. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Older, and possibly, wiser.
    I suspect it stems from this:
    Load Rating for Source Four C-Clamps.
     
  16. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Anybody got a good source for replacing the beloved pan bolts (a.k.a. "f-nut") with T-handles?

    I would love to replace 200 of them RIGHT now.
     
  17. avkid

    avkid Not a New User Fight Leukemia

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    Buy some garbage Altman fixtures and use the knobs off those.
     
  18. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Last edited: Jun 18, 2009
  19. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Yikes $6 x 160 insturments= OUCH!

    Grainger's got some great options for about $2 but the handles are 2" wide and I doubt there's enough room to turn a handle that wide.
     
    Last edited: Jun 18, 2009
  20. SteveB

    SteveB Well-Known Member

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    In olden tymes, Colortran used to supply it's fixtures with a c-clamp that had a T handle instead of a FM nut. As the shaft was made of steel, and the T nut threaded section was also steel, it *mostly* avoided the problem common to Century and Altman clamps with aluminum shafts, namely scoring of the shaft from indents of the steel nut.

    So I got the smarts one day and prior to discovering (remembering something I'd forgotten might be a better description) the aluminum scoring issue, decided to retro a bunch of my Altman clamps with T nuts, of which I had a bunch, and place these clamps on fixtures at my Box Boom positions, where access to the FM nut was an issue. In short order, the steel T nut scored the aluminum shaft and prevented the fixture from being tightened sufficiently in it's pan motion. Worse still, occasionally the nut would find a recessed groove that it liked better then the position I desired ( and that the LD was asking for) and would settle in to a new focus.

    This brainstorm was changed back to FM nuts the following season and I simply tighten the holy hell out of them, hoping people will leave the FM alone.

    Steve B.
     

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