Proof testing cable clamps

[Harold_V]

Hey, all!
I've been working on converting one of my induction furnaces to hydraulic tilt. I was trying to use my jib crane, but the time lost in transferring the crane from the furnace to the ladle was cooling the poured metal excessively, so that's just not working out as I hoped.

Modern furnaces tilt with hydraulic cylinders, but this one is intended to be tilted with a jib crane or other external means. As a result of its design and the way it's mounted, using cylinders is out of the question, but I've come up with a design which is mostly built, using a hydraulic motor and cable. Now the problem.

I don't want to risk the clamps I made not having the ability to carry the weight intended. If they failed while lifting or lowering the furnace it would most likely destroy the furnace and mount and could prove deadly if it was filled with molten metal. I'd like to proof test them to about 1,000 pounds and have an idea how I may be able to do so. Using dead weight would be very good, but I really don't have a viable way to add that many bags of sand (I have 100 pound bags of sand) in a meaningful way. What I'd like to do is hold the cable clamp in my mill, then using a 1 ton engine hoist and a portable scale of some description (that I do not have), tension the cable which is mounted in the clamp, to, maybe, 1,000 pounds and see how well it holds. I calculate the furnace weight to be about 700 pounds at the most. I have a clamp that prevents the cylinder of the engine hoist from lowering, so once I establish the intended weight, it should be capable of holding for a prescribed period of time. If it maintains the same weight for, say, an hour, that would ensure that the cable isn't creeping in the clamp.

Any comments on the concept? Suggestions of a better way to test?

H

[liveaboard]

Your target weight is 700; for a safety critical load like this, a safety factor of around 5 is more appropriate.
Rigging is something I've only done for myself, others here will likely know better.

But I would test to at least 3x the known load.
Also, will these clamps get hot during use?
No need to elaborate.

How to test; there are electronic pull scales for hoists, not too expensive these days, $300 on ebay. they do tonnage.
I made one from a little puck cylinder and a pressure gauge.
Maybe tool rental shop has something?

Or; you know the max load of your engine crane. put your load closer to the pivot point so your target tension is at the hoist specification, then use the PRV in the hoist pump to determine the tension.

It's a lot of bother any way you do it, but you're lifting molten metal!

[Inspector]

Could you use a big eyebolt and torque the nut to pull the force you need? Not being an engineer I can't say what the torque should be.

Perhaps among the calculators here. https://www.engineersedge.com/fastener_ ... menu.shtml

This one from them might do it. https://www.engineersedge.com/calculato ... e_calc.htm
If I read it right a 1" bolt of steel to pull 1000 pounds is 200 inch pounds torque.

No doubt the better educated here can step in with the correct information.

Pete

I'll add that I would be tempted to use swageless cable fittings for marine mast rigging. Biggest downside is the cost in bigger cable sizes. There are other brands that may be cheaper.
https://www.marineoutfitters.ca/index.c ... ocation=US

[Inspector]

Oh no! I was thinking again. Any reason to not use chains? Either lifting/tow or drive types? Then you could rely on bolts, shackles, sprockets etc.

Pete

[liveaboard]

I was thinking the same; chain is SO much safer than cable. You can roll it over pulleys and all too.

[rrnut-2]

Chains get very hot around induction furnaces. We used fairly fast cable hoists to tilt the furnaces.

Jim B

[Bill Shields]

ever thought about using cable wedges...or (as said)...is heat a problem?

[Russ Hanscom]

For a simple load measurement, use a small hydraulic cylinder. Fill one with oil, connect a pressure guage to the appropriate end for compression or tension loading, and calculate the applied load from the net area of the cylinder, if you are using the rod end. I used a similar rig for load testing engine hoists.

[STRR]

Harold,

Tell me the size and type of cable you plan on using and I will tell you how many, what type, and how to install cable clips If installed properly, the weak link is the cable.

There are two types of cable clips: U-bolt and twin base. The twin base are not directional. The U-bolt clips ARE directional. With a U-bolt clip you have three things: U-bolt, saddle, and two nuts. REMEMBER: NEVER Saddle a Dead Horse. The end of the cable is called the "dead end". Thus the U-bolt straddles the dead end and the saddle is placed on the live end cable. It is HIGHLY recommended to use a thimble in the eye you make with your cable clips. Doing so, will protect the cable strands and more evenly distribute the loads in the eye.

Cable clips have an efficiency rating of about 80% when installed correctly. Thus, it is important to know what you're planning on using to ensure great enough safety factor. You are welcome to load test the set up once it is built. We never have but we do make sure we never load the cable clips anywhere near 80%. We always shoot for 50% giving us an appropriate safety factor.

Yes, I am a crane operator so I know what I'm talking about.

Terry

[Rich_Carlstedt]

Terry, Great comments about saddles on a Dead Horse --Thanks

Harold , I don't understand the part about using the mill ? Is it just have a anchor at one end ?
Did you want to check the entire length of cable ..is that it ?
There are many suggestions, but they take equipment you may not have like force gauges or hydraulics
Keep it simple - example
Take a 8 foot 2 x 4 ( or steel beam) anchor one end with a fulcrum.
Drill a hole 8 inches from that end and mount a link for your cable which is hanging above the 2 x 4 .
Then place a 100 pound weight on the far levered end and you have your 1,000 pound test setup

Rich

[Wolfgang]

In many jurisdictions the labour law specifies a factor of safety of 5 for material hoists; a factor of safety of 3 for material lifts (think lift truck); and a factor of safety of 10 for personnel hoists.
Underhook appliances such as spreader and lift beams, magnetic and vacuum attachments for lifting, etc. can have a factor of safety from a minimum of 2 for vacuum chucks, to a maximum that you can decide.
When I designed and certified stuff like this for a living, I used a factor of 3 for lifting beams used in an industrial plant with well-trained hoist operators.
For areas with operators of dubious qualifications I used a factor of 5.
Only once did I design a lifting device with a factor of safety of 2, because any greater factor would have made that device too heavy for its application. There are strict design rules published by the ASME at that time, and these I followed to the letter. After all, it was my name and stamp on the fabrication drawings.

In conclusion, if it is for your own personal use, you are free to use your sound judgment and devise a safe feature. If others are nearby, best to stick to the labour laws requirements.

[Wolfgang]

Terry, Great comments about saddles on a Dead Horse --Thanks

Harold , I don't understand the part about using the mill ? Is it just have a anchor at one end ?
Did you want to check the entire length of cable ..is that it ?
There are many suggestions, but they take equipment you may not have like force gauges or hydraulics
Keep it simple - example
Take a 8 foot 2 x 4 ( or steel beam) anchor one end with a fulcrum.
Drill a hole 8 inches from that end and mount a link for your cable which is hanging above the 2 x 4 .
Then place a 100 pound weight on the far levered end and you have your 1,000 pound test setup

Obvious once you know how, right? Very clever, and this is the method I would advocate. Bear in mind that for lifting 700 lbs, you need to test for 5 x 700 = 3500 lbs.
You could arrange a 20 to 1 ratio lever, and use a 175 lb test load. Use your bathroom scale to weigh out appropriate rocks, gravel, sand, or work shop raw stock.

Rich