bending 4x4x.250 sqtube

[muddstopper]

Been a little activity while I was a way. Good ideals coming.

Right now I am kind of committed to using what I have. As I said before, My base mount isnt big enough to get the correct boom and cyl mounting points if i go with 4x6 tubing. Its just barely big enough for the 5x5. Going with bigger (taller), tube means having to raise the mounting points for the boom and move the mounting points for the cylinder back toward the center of the hub. And for some reason, it dont work out to just moving 1/2in like I thought it should, Just not enough metal there to make it work without buying/finding more metal.

Sod, your numbers ay be for the 5x5x5/16, I am planning on 5x5x1/4 which is still 2 times stronger than the 4x4x1/4 if I'm reading your charts right.

Jb, I am going out of town again in the morning for a couple of more days. When I get back, I will measure the spindle and post the results. I can see the bearings not being loaded using a boom like they would be mounting tires on them. A boom is going to be pulling at the top of the hub and pushing at the bottom, where as a tire mount would be placeing all the load on one side of the bearing, but loading both bearings evenly. I think your concern that the spindle might break from the axle isnt looking at how the axle actually carries the load. The spindle is welded to the axle tube, but the axle tube is mounted to the truck using springs. These springs are a pretty good way back from where the spindle and axle housing are welded together. Whether one tire or two, the stress at the weld should be the same and its a pretty big stress, especially traveling at speeds and hitting potholes. About the only way I can think of to stiffen up my current arrangement would to install a solid shaft. maybe the actual axle shaft that came out of the housing, but this would also mean somehow making a bottom support for the shaft, inside the axle tube, and the top would bolt to the original place on the outer edge of the hub. I cant see any advantage to doing this.

 

[muddstopper]

I decided to go ahead and get the measurements. Got grease on my shirt, now catching heck from the wife. Oh well. First pic is the spindle. Its 3 1/4in dia at outer bearing and 3 3/4in dia at inner bearing. 4 1/4in between inside edge of bearing and 7in to outside edge of bearing, 13in from end of spindle to where it is welded to the axle tube
Next pic , weld for spindle is 6in to the center of the spring housing and axle tube is 5x4 1/2inches OD. Last pic is 9inches from the base of the hub to the weld of the spindle to the tube.

My current plans are to cut the tube to fit inside a 6x8x1/2 tube to get the height I need for the loader and to provide something to weld to when fastening to the outriggers and trailer. I am also considering using some 12in diaX1/2in piling pipe and adding gussets to keep it upright, and just putting the axle tube in it instead of the 6x8 tube. Either material I choose to use I will be making a plate cut to fit the outside of the axle tube and the inside of the pipe or tube to support it top and bottom.

Well phooey, pics aint in proper position, but measurements are written on each pic

 

[Shield Arc]

muddstopper I'm wondering (thinking out loud here). If it would help to heat shrink the two top heels of the box tube before you add the mounts for the hydraulic cylinders? Just enough to put a long arch in the tube?

 

[muddstopper]

SA,I dont know if that will help. what is the goal , or what would i hope to achieve by bowing the tube. I suspect you are meaning bowing it upward, but how is that going to improve bending capacity? I am thinking that by the time I add the mounts for the cylinders, that the boom will be plenty strong enough for what I plan on lifting. the 2000lbs I am wanting to build for is a worse case senerio. I suspect actual load weight to be half or less, than 1 ton. If I do run into a 1 ton log, its pretty slim chance I would be picking it up at full extensions

 

[Shield Arc]

My thought process is, when you heat steel the molecules in the steel expand, but when it cools, or you use water to cool it the molecules contract tighter, so the steel bows. In my mind I think it would take more force to bow / bend steel that the molecules are tighter. Also the bow in the opposite direction has to help some.:confused3:

 

[LD1]

Not sure if it would help in the situation, as I have never really thought about it.

Usually you see pre-stressed or arched things where there is a solid attachment point at both ends. Like a bridge. Where in order to deflect downward, the bridge would actually have to grow in length. With solid footings, it cant, thus helping limit deflection.

Without solid anchor points at two ends, I dont see it helping. Regardless of arch, once the stresses go above what the steel is rated for, you will have a permanent bend.

 

[Shield Arc]

Not sure if it would help in the situation

Me neither, just throwing out suggestions.

 

[muddstopper]

Well, I think I am going to goahead and get the 5x5x1/4 tube and ust shoot from the hip since I cant determine for certian if anything heavier is really warranted. Once built and with some testing, if it doesnt look like it i going to hold, then I will just build a truss. I really dont think its going to be a problem, but at this point I havent seen enough evidence to suggest that it will or wont work.

With that said, I guess the next issue is what size pins to use at the boom base. I intend to use some 2.5in shaft to make a bushing and drill it out to accept a 1 1/2inch pin, using the same setup for the knuckle for the outer boom. I will be radiusing the outer end of the boom and installing a cap, as well as side plateing the tube to provide extra strength to keep the pin/bushing from pulling out of the 5x5 tube. The 2 1/5in bushing will be welded inside and out before the cap is installed. The shaft material I plan on using I dont know what type of steel it is, but I know it supports a pair of 6in bore cylinders and is a bear to cut in a hacksaw. I have bent some of this shaft before, but it took a heck of a impact of a 64000lb piece of equipment hitting an immovable object running about 25mph. Tore up a several thousand $$$ worth of equipment, but the shaft material just bowed a little bit.

 

[Sodo]

the bow in the opposite direction has to help some.:confused3:

If you had a "need" to manage the displacement (flex) it could be useful. Theres no reference point for a boom.

A bowed structure many have seen is a 53ft flatbed trailer, for example the aluminum ones. They would look flimsy if loaded and curved, so they are biased to be curved up (noticeably) when empty (& straight when loaded). They are a highly engineered structure. Every pound of structure removed from the trailer is "payload" (=$profit) for the trucking company, day in & day out. Not a strength difference, more of an "appearance when loaded" issue (I think) and probably ground clearance too! Aluminum flexes a lot more than steel.
When you re-melt the steel you alter the grain structure that was created by the rolling operation. I'd be interested to hear from a metallurgist type (or the steel mfr) if strength is affected, and it could go either way but my gut is that re-melt would reduce strength, especially if you had a little boo-boo along the way. Certainly you wouldn't use this method on a spring, for an absurd example.

 

[LD1]

Just shooting from the hip as well, I think the main swing pins on my BH boom are 2.5" And have about 18-20" of distance between them. I am good to lift 2k at a full 20' but the boom and bucket are also heavier.

The further apart you can get the pins, the less stress on them