Need a steel engineer

[Wayne County Hose]

I am building a hydraulic nut removal tool for my cylinder shop. I will be removing nuts on the bottom of rods that are torqued to 5,000 ft. lbs and maybe more. I have narrowed the design down to a single piece of steel for the frame, with a piece to hold the rod eye from rotating on one end. On the other end, I am building a hydraulic wrench to turn the nut. I am wondering about what steel to use and what size. Would an I beam be good, or would square tube be better? It would have to withstand 5,000 lbs. of rotational force. Any ideas?

 

[yankeerider]

Do I understand that your hydraulic wrench will have a cylinder at one end and a socket or crowfoot-type device at the other? A picture would help. In general, size is more important than shape.

In bending, the depth of the web is far more important than the thickness, although an I-beam of say, 4" depth may be more flexible than a 4" square tube if the wall thickness of the tube is greater than about 1/2 the thickness of the web.

Normally, shape is dictated by other factors, As for type of steel, if you aren't limited by size or weight, a larger piece of a lower grade of steel will likely be cheaper and easier to weld. If you've got some material you want to use, post the sizes and material and we can help with relative strength.

 

[Wayne County Hose]

Jerry, I would purchase the steel new as this is something with a lot of force and I wouldn't want to risk my body parts with possibly fatigued steel.

The best way I can think of to describe what I want is this would look something loke a log splitter. At one end, I would make a jig to go thru the rod eye, to keep the rod from rotating. On the other side, would be my hydraulic wrench. Basically, a wrench powered by a hydraulic cylinder. i would make different "sockets" to fit different nut sizes.

If you go to this website, Machinery Service & Design, a New Generation of Affordable Hydraulic Rebuilding Equipment, look for the "nut buster." This is my hydraulic wrench that I would build.

If you look at the above website, that is in principle what I am trying to build. I am not looking for the rotational force that they have. That is why I think I can build one out of one piece of I beam or square tube. A pretty large piece, but I would like to keep this as simple as possible. Thanks for any help you can give me, Andy.

 

[Farmerford]

Andy:

In terms of resistance to twisting per pound of weight, round tube is best of all, square tube is little less effective, and I-beam or wide flange sections (H-beam) are much less effective.

Just doing very rough calculations in my head, a square tube of A-36 structural steel (36,000 psi tensile strength) 1/2" thick and 4" on each side should handle about 10,000 ft# of torque without exceeding 50% of its tensile strength.

But if that tube is very long (say 6') it will twist quite a bit with that heavy a load. I am not sure what the twist will do to your machine. Perhaps the holding fixture and the wrench head can swivel on an axis perpendicular to the long axis of the tube to keep the ends reasonably lined up when the tube twists.

The twist is calculable, but I don't know the length of your tube and my references are not at hand.

Perhaps a member with newer information than my four decade old engineering texts can give you a better answer. But if you let me know the length I will give it a try over the weekend.

 

[Renze]

If you're making some sort of clamp, it would probably be best to have it CNC torched out of solid steel. This way you dont have to worry about weld strength or fatigue.

but please sketch it out for us, so we know what you're actually talking about..

 

[Mickey_Fx]

IMO you've not provided anywhere near enough information on the "design" for somone to give you specific information on material and the material's geometry.

If I understand your comments, the single piece of steel you mention in your first post, the frame, this needs to be torsionally strong. "I" beams are not the best chioce for this app. Sq or round would be better. Length of the frame and the amount of acceptable twist needs to be known before a particular kind/size of material could be reccomended. Would also need to know how far away from the frame the center line of the cyl is.

Then I may be all wet with my comment.

EDIT:

Looks like while I was composing, farmerford posted his comments. Looks like we are not far away in our thinking.

 

[Wayne County Hose]

Sorry guys, looks like my ignorance on this subject is coming to the surface. I would draw something, or post a pic, but I don't know how. I've asked a few times, everyone tells me to email it to them and they will post it. That doesn't help me learn to post it myself.

Anyhow, I'm thinking 8' max on the length. Distance from the outside edge would be about 8". I will do some more research and post more info later. Thanks for your help, Andy.

 

[RFB]

Wayne County,

check your private msgs.

 

[Shmudda]

Andy,

If you are building this for a business, and you will have employees operating the unit I would HIGHLY suggest to bite the bullett and purchase one!

With the laws of today around "home made" lifting beams, wrenches, and anything else that can break and cause bodily injury it's not worth risking your business.

On the other hand, just remember this too, the drive shafts on vehicles are hollow, which a hollow shaft can take 75% rotational torque of a solid. I could design something like this for you very easily, but I, just the same as most others want to see what you are actually talking about. Then there's always the fear that someone would get injured with it and then everybody and their brother will be sued.

Sad world we live in to say the least.

Craig

 

[Eagleview]

With the different length rods you will be working with it will have to have adjustable headstocks . The steel profiles your thinking of wont stand torsional loads . The steel you choose will have to stay true lengthways not only to resist the torque initially imposed by the spanner but also so that when the nut lets go it wont throw things at you . I would be more inclined to use a thick walled tube with a wall thickness of around 3/4" and maybe 8"-10" in diametre . It would have holes/slots radially cut along its length to accept the pin to hold the ram eye . It would have a 1" Bisalloy 80 flat plate with the center cut out welded to the end in the shape to suit the eye of the spanner ram or rams (remember that you have to have it go both ways so you can re-tighten it later) and provisions to take a hinged safety cage . The unit would be mounted verticaly to the concrete floor . You would lower the ram bar into it with an endless chain , install the eye pin through the side holes , install the spanner on the nut , close the safety cage and push the lever . The tube would be torsionaly strong and also act as a safety shield . Remember that with 5000# of torque applied the ram bar will twist a little and when the nut lets go it will go off with a bang . You may want to think of using a torque multiplier to make the rams job easier .

 

[Wayne County Hose]

I appreciate all your guys input. RFB is working with me on posting a drawing. I'll get something drawn up tonight or tomorrow and hopefully have it posted by Monday. This is exactly the input I'm looking for as you guys sound like you know what you're talking about. If you go to the website posted below, you will see a hydraulic cylinder disassembly table with the nut remover. I am trying to build something similar but on a smaller scale. Rather than a 15' table, I think I can do this on a piece of steel 8' long. Please take a couple minutes to look at the disassembly table on the website and tell me if I can accomplish this on a piece of square tube. Albeit, a large, thick piece, but these tables on the website are made to go to 50,000 lb.ft. and I only want to go to 5,000 lbs. Thanks again for your input, Andy.

Machinery Service & Design, a New Generation of Affordable Hydraulic Rebuilding Equipment

By the way, I have a friend that is a certified welder who will do all the welding. I have no employees, just me. I do work as safely as possible, believe me, but I don't have $20,000 to spend on a piece of equipment which is much larger than I'll ever need.

 

[jmc]

This is exactly the input I'm looking for as you guys sound like you know what you're talking about.

When someone specifies tube properties without regard to wall thickness, watch out.

Interesting project, BTW.

John

 

[Wayne County Hose]

When someone specifies tube properties without regard to wall thickness, watch out.

Interesting project, BTW.

John

I haven't really given enough info for anyone to be specific. I will have info ready by Monday. I did build my own disassembly/assembly/test table. I can disassemble and assemble cylinders then pressure test to 2200 p.s.i. for any amount of time. Usually I cycle the cylinders a few times and run them in all the way and manually close a 7,000 psi valve. Then, I walk away for about 15 minutes. If they hold pressure and don't leak, they are ready for the customer. Now, I need to be able to do this to excavator cylinders which is why I need to build this project.

 

[Darren]

I've always used a torque multiplier to remove large nuts. The 5,000 ft lbs you need is within the torque range of the heavier units. You'll have to anchor the cylinder, which means you can also anchor the torque multiplier. It won't be as slick as the setup you're building, but as long as you can get it on the nut, it will take it off.

If you're doing lots of large diameter cylinders, your idea will be better. If you don't do that many, the multiplier may save you money.

 

[Dirthog]

you will need a whole lot heaver table that you think we have one made by OTC which is 6x6 angle 1/2" thick it is 20ft long even with all the braces in it it is not heavy enough for the longer and larger excavator cyl there is a 40 to one multiplier mounted on the table and you can twist the table like a pretzel if you are not careful. The nuts on any thing much larger that a 120 size machine are way more than 5000 PSI the nuts on a 300 size start at 12000 psi for the bucket and the arm and boom are much more. Also they need to be pressure tested to 5000 Psi we have had more than one that was alright at low pressure but would bypass at working pressure.

 

[Wayne County Hose]

Thanks dirthog, I may have to rethink this. The large commercial ones specify that they be bolted to concrete with 3/4" anchors. This is to help prevent twisting. I'm thinking I may just have to build one of these tables and bolt it to the floor. The more I think about it, the more I come to the conclusion that if this could be done with a single piece of steel like I want to, that it would have been done by now. Now, to price out 2"x4"x.3875" steel. Ouch!

 

[Dirthog]

thats the was ours WAS bolted to the floor but with the twisting it takes it will not stay tight we have moved it several times to keep it bolted down

 

[MrJimi]

Thanks dirthog, I may have to rethink this. The large commercial ones specify that they be bolted to concrete with 3/4" anchors. This is to help prevent twisting. I'm thinking I may just have to build one of these tables and bolt it to the floor. The more I think about it, the more I come to the conclusion that if this could be done with a single piece of steel like I want to, that it would have been done by now. Now, to price out 2"x4"x.3875" steel. Ouch!

Andy, I bought a 4 foot by 8 foot by 3/8 plate for around $240, and they sheared it for me, Just remember, you only buy it once
Sounds like a great project
Jim

 

[mooseye]

I don't think you are going to find a single piece of steel that will withstand the twisting force you will be working with. If you did, it would likely be as big as a bridge truss.
You may, however, be able to construct a table out of multiple members that will handle it. Lots of diagonal bracing and heavy main structure. Fastening it to a concrete floor will be a benefit.
My first thought would be a heavy pipe section that would connect to the same part turning the nut. A heavy pipe with a bolted flange on the end that would go over the cylinder and could have holes at intervals to pin off the eye end, and then a mount on the far end to prevent deflection. All the torque would be transferred to the same end that is doing the turning.
Just a thought.

Okay, just reading back through and I see that I missed Iron horse's post which is basically the same idea I have.