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Clamps : Welding/ Weight/Stress & Torque
Published : 10th October 2003
I love the Cardellini clamp and have found that's it's useful in almost every situation. But recently I've seen grips rigging platforms and other such safety-related rigs using these clamps. How much weight, stress and torque can these cast clamps really take?
Also, when building rigging, what do most grips favor fr strength - drilling a hole & bolting through, or welding?
Contact Steve Cardellini at : www.cardelliniclamp.com
He's a very experienced and very conscientious key grip in the San Francisco area. He's always happy to talk to customers about the use of his products.
Motion Picture First Camera Assistant
Mitch Gross wrote :
>I love the Cardellini clamp and have found that's it's useful in almost >every situation. But recently I've seen grips rigging platforms and other >such safety-related rigs using these clamps.
Most of the situations I've been involved in I've all way gone for at least pipe and clamp, or I-Beams for larger rigs. Trussing is good too. Can you be a little more specific about the situations?
I feel that the Cardellini is highly over used and most of time over used. People hanging HOT lights from them and melting the gripper pads resulting in movement. Or over cranking on the handle / knuckles bending the clamp itself.
Key Grip - Toronto
>Also, when building rigging, what do most grips favor fr strength – >drilling a hole & bolting through, or welding?
I don't know what most grips do, but in most of the rigging situations that I encounter, I use rated bolts and holes rather than welding. This has more to do with the sorts of jobs I rig - It is much easier to un-bolt something than to un-weld it when you want to adjust it...and depending very much on the specific application, I feel that I am in a better liability position working with rated hardware of known strength than with un-X-rayed welds of unknown penetration. Again...the answer to this question is much too situational to be answered with a blanket statement.
Re : Cardellini’ s : These are wonderfully designed clamps that do what they do extremely well. If you misapply them in rigging, you can certainly be in for a world of hurt. There are other sorts of devices that might be better used in taking structural loads in platforming...like scaffold clamps, Chessboros, rotolock clamps, etc. and even wood and nails or carriage bolts.
Erstwhile builder of camera rigs
The load rating of the end-jaw Cardellini clamp is, if I recall correctly, listed at either 20 or 40 lbs.
Although I, at over 250 lbs., have done pull-ups from two of them when mounted on permanent building pipes and railings.
There is, one may assume, a difference between the load rating that one may trust for liability and absolute safety at all times and in any given situation - and the load rating that you load on any device with reasonable safety, depending on angle, additional hardware levering the load out farther from the strongest point of contact and whatever supplemental safety chain, cable, rope you wish to apply.
In other words, if it doesn't feel safe, make it so or use something else.
When using rope, sash, chain and various hoists, there is an old practice which recommends never loading up say, 600 lbs. on a 600 lb. line, but no more than 20% of the load rating, so 120 lbs. max. Michael Uva recommends the same in his book "The Grip Book."
Structural and electrical engineers tell me that "50% redundancy" is a common safety practice in their field.
Take it easy, but take it,
Cinematographer (with a long grip/electric history)
I'm glad to see that people are using and talking about Cardellini Clamps.
I would like to share some information about them that relates to comments I have read here recently.
The "official" rating of a standard Cardellini Clamp, as stated in the information sheet that comes with the clamp, is twenty pounds. I'll tell you how I came up with that rating. First, my lawyer told me that for liability purposes I should give the clamp a rating. Second, I found out that getting a product tested and rated is very expensive. So, third, I looked through lamp catalogues and found that the heaviest lamp that was designed to mount on a baby pin weighed twenty pounds. I was certain the clamp could easily hold twenty pounds, so I chose that as the rating. I knew that experienced grips would appraise the clamp when they had it in their hands, and make their own decisions as to what the safe working load was in each particular application.
Concerning the strength of the jaws : The jaws are cast, they are sand castings. I chose an aluminium alloy that is somewhat stronger and less brittle than the standard 6061 with a T-10 heat treatment. Die-cast parts, such as those used on the Matthellini Clamps (for which Matthews does pay me a royalty) are prettier parts but they are more brittle. I have heard of Matthellini Clamps that were dropped on the ground and had jaws brake. I have not heard (knock on wood) of any of my jaws breaking.
In all the cases I've seen and heard of, the shaft bent before the jaws broke. If anyone has had a jaw break on their Cardellini Clamp, I would be very interested in hearing the story, with as much detail as possible.
About the jaw pads : They have always been the weakest feature of the clamp, but I couldn't come up with a better solution. I had to settle for making them easily replaceable. This can be done by buying pre-cut pads from me, or just going to a home improvement store and buying some 3M Safety Walk tape, the kind people use on their stairs for traction. Years ago I looked into having rubber vulcanised onto the jaws, like they do on a motor mount for a car. I found that the sand cast jaws, not being perfectly identical, couldn't meet the tight tolerances required for the moulds used in vulcanising. I could have done it with die-cast parts, but I didn't want to sacrifice the strength. Now, I think I have come up with a solution on the Mini Cardellini Clamps. I'm machining the jaws from an extrusion. These parts have good strength characteristics, and the identical parts fit the vulcanising moulds. The vulcanised jaw pads seem to hold up well.
If they show the longevity I hope for, I will be looking into changing over the regular clamps to this same process sometime in the next year or so.
San Francisco Bay Area