Conventional Fixtures - C-Clampery

[derekleffew]

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?


More or less standard parts nomenclature:


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.

[gafftapegreenia]

*gasp*

ETC how could you.

[avkid]

That makes no sense, why????????

[techieman33]

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.

[gafftapegreenia]

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.

[willbb123]

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.

[SteveB]

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.

[derekleffew]

SteveB, that was worth at least 5¢.

While I agree (also with no empirical evidence) that the ETC clamp has to be stronger than the Altman, the Mega Clamp remains the only clamp with a SWL stamped on it.

Interested parties may see this thread: http://www.controlbooth.com/forums/l...mps-rated.html for further imformation.

[gafftapegreenia]

I HATE the Altman heavy duty clamp.

[SteveB]

Originally Posted by derekleffew

SteveB, that was worth at least 5¢.

While I agree (also with no empirical evidence) that the ETC clamp has to be stronger than the Altman, the Mega Clamp remains the only clamp with a SWL stamped on it.

Interested parties may see this thread: http://www.controlbooth.com/forums/l...mps-rated.html for further imformation.

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