bending 4x4x.250 sqtube

[LD1]

If you are planning on using tubing other than what you got, I'd still go with 4x6x1/4 tubing. Gonna weigh the exact same as 5x5x1/4, but about 50% stronger in the direction you need it. And no trussing would be required.

And if buying, there should be minimal or no cost difference since the weight is the same.

 

[muddstopper]

I thought about the 4x6, but what I am running into is not having enough base metal to make the base mount. Right now as I have it drawn out, the boom mount is in the center on above my hub. The base pin for the cylinder is just inside the outer edge of the 20in wide base. I can slide the side mounts forward and mount the boom off center of the hub, probably wouldnt have to move it more than about a inch, but the more I move it off center, the more side load I place on the hub. Ideally, the boom would be mounted back of center and the cyl mounted forward of center to even out the load, I think?? I could always look for more metal to make the base out of, but used flat plate around here is hard to come by and expensive to buy new. Just going from 4x4 to 5x5 moved my top boom mount up almost 2 inches. I would have thought only 1/2in, the difference between the center of tube to outer edge, but it didnt work out that way. I havent said this yet, but the hub extends 6 inches up and is 8.5 inches wide in between the upright side mounts. Just doesnt give me a lot to play with. I'll take a pic of the setup to show what I mean.

Dont know if you can tell what the first pic is, its where I drew everything out on the garage floor. Piss on Autocad.

 

[crazyal]

Well the engineers at work claim my 4x4 tube will support 3800lb overhung braced in the middle of 8ft. I explained that 8ft is just the root boom and the dipper boom would add 8 more ft to the overhang, right off said then it was going to bend, but he would do the math and get back to me. Well he never got back to me so i still dont know what I need to know.

Looking at the Lemco and where the cylinders are mounted, well thats almost exactly what I had in mine. I feel the plating for the cyl mounts should add some strenght, but dont know how much. I am not opposed to the truss ideal, but would prefer not to use trusses simply because of eye appeal. I would rather it look ugly than fail, so the final build will probably include some sort of truss. The ideal of build it then add weight until it gives, then add a truss if needed, I had considered. Right now the only way I see not to use a truss is One, use bigger tube. Two, add plenty of plate in the middle of the boom for the cyl mounts and let that be the extra strenght. Three, use 2x4 tube and double it along with the extra plating. Right now I think all three methods will work, but will have to see what I can scrounge before actually building anything.

Been kind of following this out of curiosity and it sounds like a fun project. Here's my thoughts, hopefully I help. You may have an extra 8' on the end but will you ever have both arms extended horizontally? That would be the only way that you would have 16 total feet. Secondly have you thought about different sizes for each arm? The boom is going to see more stress that then the dipper stick (sorry I know backhoe terms). I may have missed your posts with the answers to my questions, sorry. What are you planning on using for pins?

I'm assuming that you are kind of doing this more off of pictures and a working version. If so my advice would be to get a couple of 2x4s and make it out of wood and have someone with a tape measure where you think the cylinders are going to go so you can see what open vs closed will do plus you can get a real world feel for just how far it will reach.

I don't know too much about log weights but I was always told that a cord of green wood weight about 5000lbs. Maybe others can chime in if I was told wrong. 2000 lbs of lifting force would be more than a 1/3 of a cord, do you think the logs/ rounds you will be lifting will produce that much firewood? There's a local rental/ repair shop that has one of these sitting in their yard:

If you would like I can try to get some measurements the next time I'm near there.

 

[muddstopper]

I have quite a bit of experience running a small knuckleboom loader, and this size loader is kind of what I am trying to copy. PW TC 407 Kershaw Tie Crane with Push Car and PW TC 315 Not as big as a log loader you would see in a big logging operation, but just a little bigger than the Farmi, Anderson, etc, forwarder loader. Your questions are valid. I would think very rarely would I ever have a reason to try and pick up a large log at full extendsion. Normally at full reach, you would grap one end of a log and as you raise the root boom, you would retract the dipper boom, getting the log close to the loader before actually lifting it all the way off the ground.

I have a couple of reasons for wanting a long boom. One, developers often push out a new road and leave the timber laying just below the road. I need a boom long enough to reach those logs. Another reason is a lot of the loggers around here dont have loaders on their trucks. They load them in the woods, and unload them at the log yard. I need something I can reach the logs on a loaded big truck if I want them to deliver to my yard.

Looking at the loader in your pic, you can see the booms are pretty small material. Short, the one in the pic probably not over 9-10 ft. My trailer bed is 8ft wide, a 9ft boom will only allow me to reach about 5 ft past the trailer, a 16ft boom allows about 11ft reach. Of course any boom I have ever used always seemed to need about 2 more feet added to the end of them, but I have to draw the line somewhere.

As for weight, a red oak log, 24in in dia and 14ft long will weight around 2500lbs . I am building my processor large enough to handle a 27in log. A 27 in dia red oak log 14ft long will weigh 3100lbs. A cord of red oak will weigh around 5700lbs. One 24in log and one 27 inch log and I'm right at a cord. Of course, I dont expect every log to be of these sizes, and I dont expect to load 14ft stuff of that dia with this loader. A 20 in 14ft log, weighs about 1735lbs and I think most of my wood will be under that size, but if I build to handle the weight of a 20in log, then the rest of the stuff I dont have to worry about.

 

[GLyford]

The log trucks I have seen allowed you to pull a lever and unlatch the posts along one side, leaving you with a pile of logs on the ground...getting them down is usually easy. Up and into the truck, on the other hand...

Well, I suppose it makes a difference if you are only buying a couple of logs off the truck, rather than whole load.

 

[muddstopper]

Yea we used to have those kinds of trucks, but any more, the loggers just back up to the loader to get loaded and at the log yard they use a big loader to set the logs off. Very few folks around here even have loaders on their truck. Timber cutting isnt a little guy job now.

 

[jb1390]

I thought about the 4x6, but what I am running into is not having enough base metal to make the base mount. Right now as I have it drawn out, the boom mount is in the center on above my hub. The base pin for the cylinder is just inside the outer edge of the 20in wide base. I can slide the side mounts forward and mount the boom off center of the hub, probably wouldnt have to move it more than about a inch, but the more I move it off center, the more side load I place on the hub. Ideally, the boom would be mounted back of center and the cyl mounted forward of center to even out the load, I think?? I could always look for more metal to make the base out of, but used flat plate around here is hard to come by and expensive to buy new. Just going from 4x4 to 5x5 moved my top boom mount up almost 2 inches. I would have thought only 1/2in, the difference between the center of tube to outer edge, but it didnt work out that way. I havent said this yet, but the hub extends 6 inches up and is 8.5 inches wide in between the upright side mounts. Just doesnt give me a lot to play with. I'll take a pic of the setup to show what I mean.

Dont know if you can tell what the first pic is, its where I drew everything out on the garage floor. Piss on Autocad.

I do not think your hub will be adequate. A wheel on a truck is almost perfectly in line with the bearing assembly. Your design places significant bending load on whatever axle fits in that hub unless you support it on both sides. If you look at a backhoe or anything similar, the pins are set apart vertically a decent distance, so you don't get the bending load. The pins in a backhoe are loaded in shear.

Bringing the pin off center won't really change the moment (bending load) on the hub. Moving it an inch off center will be negligible if you were to do a bending load calculation. This is the type of basic engineering that I feel may be lacking when building this from scratch, and hence why I have concern for your safety.

 

[muddstopper]

I dont know if I am following what your saying. Are you saying the hub off a 48,000lb truck axle, (24,000lbs using just one hub) which has a factory safety factor of about 5x (120,000 lbs) isnt going to support my boom with a 2000lb load at the end of the 16ft boom? There wont be any axle in the hub,http://www.tractorbynet.com/forums/...183419-bending-4x4x-250-sqtube-0509151048-jpg, this is the hub I am using, I will be using the actual axle spindle to mount the hub on. The flat plate laid up on the hub in the pic has a couple of circles with center marks in white chalk. Those chalk marks are where the boom (at the top center), and the cylinder (bottom left side and very close to the hub). The boom pin is 17.5 inches higher and in the center of the hub, and the cylinder pin is 6 inches forward of the center of the hub. With the amount of metal and cylinders I have available, this is about as good as it gets and the only way I can get the 105degrees of swing of the boom. Now I understand the pin locations on a backhoe boom,(I assume you are taking about the root boom and swing pins) and how far apart they are. A 48000lb hub has bearing about 8inches apart front to back. The hub spindle is a lot bigger than any backhoe pin I have seen even tho the spindle is hollow. I am not real sure of the distance apart of backhoe pins, but I will check a few out tomorrow. Backhoes booms are rated for much more than 2000lb and the booms are generally 14ft or longer fully extended.

Just to add, the hub itself is 8.5in in dia. I dont have a measurement on the spindle dia, but did try to put a piece of 2.5in dia shaft thru it. Shaft was to big to fit, but it didnt like much, maybe an 1/8. Didnt try to measure the outside dia, but can when I get back home Friday.

 

[jb1390]

I dont know if I am following what your saying. Are you saying the hub off a 48,000lb truck axle, (24,000lbs using just one hub) which has a factory safety factor of about 5x (120,000 lbs) isnt going to support my boom with a 2000lb load at the end of the 16ft boom? There wont be any axle in the hub,http://www.tractorbynet.com/forums/...183419-bending-4x4x-250-sqtube-0509151048-jpg, this is the hub I am using, I will be using the actual axle spindle to mount the hub on. The flat plate laid up on the hub in the pic has a couple of circles with center marks in white chalk. Those chalk marks are where the boom (at the top center), and the cylinder (bottom left side and very close to the hub). The boom pin is 17.5 inches higher and in the center of the hub, and the cylinder pin is 6 inches forward of the center of the hub. With the amount of metal and cylinders I have available, this is about as good as it gets and the only way I can get the 105degrees of swing of the boom. Now I understand the pin locations on a backhoe boom,(I assume you are taking about the root boom and swing pins) and how far apart they are. A 48000lb hub has bearing about 8inches apart front to back. The hub spindle is a lot bigger than any backhoe pin I have seen even tho the spindle is hollow. I am not real sure of the distance apart of backhoe pins, but I will check a few out tomorrow.

Distance of bearings is of partial importance, but you are not supporting the hub above and below the bearings. This means you are relying completely on that spindle in bending. This isn't how the hub was intended to be used, and you can't guarantee (or even predict via a calculation) that it won't break at the base. The other issue is that the axle stub is probably a harder steel, so it's more prone to a brittle failure vs a bending failure. I.E. a crack that one day completely lets loose unpredictably.

 

[jb1390]

Distance of bearings is of partial importance, but you are not supporting the hub above and below the bearings. This means you are relying completely on that spindle in bending. This isn't how the hub was intended to be used, and you can't guarantee (or even predict via a calculation) that it won't break at the base. The other issue is that the axle stub is probably a harder steel, so it's more prone to a brittle failure vs a bending failure. I.E. a crack that one day completely lets loose unpredictably.

For reference, if your spindle is only restrained on one side, a 3" solid steel center hub would not be sufficient.

2000 lbs * 16 ft = 32000 ft-lbs. Here is an analysis of 32000 lbs applied to the end of a 3" solid steel bar.