Question about steel strength??

[jodebg]

Would it be possible to insert a smaller (tight fitting) tube or channel into the 1.5 x 3 tube for maybe the first third of the length?

 

[LD1]

Would it be possible to insert a smaller (tight fitting) tube or channel into the 1.5 x 3 tube for maybe the first third of the length?

Sure. But sounds like too much work to me. And not as much benefit for the weight. The closer you get to the neutral axis (center), the less effect it has.

that is why solid steel is ALOT heavier, for not much stronger than the same dimension of a hollow section member

 

[jodebg]

LD1-I have no prior experience with metal fab or design so I could use your advise.
I posted a drawing of my proposed design yesterday. My tractor is a 30hp with 1650 lb
3ph lift capacity.

I need to lighten my total weight, but keep it strong.

-Can I use 2x2" tubing for the frame. The orig. plans called for 2.5x2.5 tubing and that
was load tested to over 200lbs which I cannot get to.

-What is the best fork material to use?
Looks as if the 3x1.5 is out.
2x2 is what is used in the plans.
Any advantage to using the 2x4's?
Again, I will be adding weight using the 2x4 forks.
But more importantly, will I have anything to gain due to the limited lift capacity?

-Any suggestions on how I can best design to bottom frame/receiver area. Needs
to be strong, but not trying to add any unnecessary weight.

-

Sure. But sounds like too much work to me. And not as much benefit for the weight. The closer you get to the neutral axis (center), the less effect it has.

that is why solid steel is ALOT heavier, for not much stronger than the same dimension of a hollow section member

 

[LD1]

So were the original plans calling for 2.5x2.5 for the forks? or 2x2?

2 main benefits to 2x4 other than strength

1. less likely to bend side by side. like if you are backing under a log or something and arent perfectly square. less likely to fold it sideways

2. Wider. Depending on what you are moving, can make for a more stable load.

The 2x2x1/4 tube is 5.41# per ft. So if each fork is 36" you have 32# of fork
The 2x4x1/4 tube is 8.81# per ft. So the total fork weight is 53#.

So the whole thing will only be 20# heavier.

I like to overbuild things. I want to be sure it isnt gonna fail. What happens in 10 years if you get a bigger tractor? What happens if a buddy with a larger tractor wants to borrow them?

 

[jodebg]

Plans called for 2x2 for the forks.
Never thought of 2.5x2.5 for the forks??

Do you think using 2x2 for the frame (in place of 2.5x2.5 in the plans)
woul be a strength issue?

Any suggestions on the lower frame/receiver design and materials in my drawing?

 

[LD1]

2.5x2.5 is certainly stronger for the frame. but 2x2 would probably work also. I think the welds are gonna be more critical than the steel

 

[jodebg]

Where can I reference the weight of these different materials?

 

[LD1]

Where can I reference the weight of these different materials?

I just do a little googling. usually will find a suppliers website that lists charts.

I like this website Structural Steel Tube, square and rectangular tube, tubing, steel pipe, I-beams, angle channel, wide flange beams

You can click about middle of the page above the charts to list rectangle tube

 

[jodebg]

Thanks. Best place to buy the steel-locally, or an online seller?

 

[Sodo]

If you welded receivers near the outside ends, would you be able to use this with a set of removeable forks?

Not really,,,,,

1) the pic is with the 3-pt at lowest, which is 11 inches above ground. Each tine would need a 10" dogleg to set at ground level.
2) the 2x2x1/8" sq tube would not be strong enough to resist the torsion from a fork tine at the outside ends.

 

[jodebg]

Wasn't thinking about the height off the ground-you're right.
Hope you post photos when you are operational.

I checked the difference in weight on the frame tubing. An additaional 1.3 lbs per foot to use the larger.

Not really,,,,,

1) the pic is with the 3-pt at lowest, which is 11 inches above ground. Each tine would need a 10" dogleg to set at ground level.
2) the 2x2x1/8" sq tube would not be strong enough to resist the torsion from a fork tine at the outside ends.

 

[Sodo]

Would it be possible to insert a smaller (tight fitting) tube or channel into the 1.5 x 3 tube for maybe the first third of the length?

In general there is never a "tight fitting tube" available, for the most part, only disappointment comes from that classic metal-fab desire. If you weld a 1/4" flatbar on the outside (top and bottom) for the first third the tine can rival the strength of 2x2x1/4. With 1/8" Flatbar at top & bottom third it will be 25% stronger than 2x2x 1/4. Agreed square looks funny for a "fork" but choosing rectangular, your sockets all have to be custom-made because there is no ("seems like never") a tube to fit it, but sometimes you cn fit them with shims welded on. The plans use the 2.5" for the 2x2 sq. tine because that combination is one of the few "fitting" sizes. And even then, you may have to fuss with the weld flash (which is not a big deal on a short receiver) or look for the special "2.53" receiver size. Anyway, square is easier.

On forums, despite no pics of (reasonable) attachments actually failing you will find very little support for building that attachment appropriate to its usage, and huge support for overbuilding - it's just the way members interact on forums. Don't wanna start a "Bull Engineers in full mortal combat" over your project but you might keep in mind that the recommended max 3-pt implement weight for a 7800 is 500 lbs. Your initial desire to leave some capacity for cargo has validity. I will take a guess that the 7800 is unable to lift 900 lbs (two 55 gal drums of water) but I bet Kubota doesn't want it traveling with more than 500 lbs. Just IMHO.

To weld 1/4" thick material be sure to bevel the joints otherwise you won't get the additional strength you paid for (and will carry around). Unless you have capacity to weld with 3/16" rod etc. Do you have a welder that can penetrate 1/4" - thats a tall order for a newbie. There are times to overbuild and times not to, and not having an understanding of material strengths, that alone may be a good reason to overbuild.

If built per the drawing ----Sodo---- would use 1/8" material for a compact tractor and don't lend it out. If you prefer overbuilt, 3/16" will be 50% heavier, cost 50% more, and be more than 50% stronger, handle the next size bigger tractor etc seems quite reasonable and prudent. Sizing that for a tractor with 1 ton lift capacity when the tractor you have weighs only 1800 lb only has downsides, (to me).

 

[LD1]

I'd buy steel locally. But I have some good suppliers. Doesnt hurt to check both online and locally.

Fabbing up a receiver shouldnt be hard. Or you can just buy some 5x3x1/2 wall tubing. Its 20# per ft, but you would only need a foot or so. (6" each side)

 

[jodebg]

In general there is never a "tight fitting tube" available, for the most part, only disappointment comes from that classic metal-fab desire. If you weld a 1/4" flatbar on the outside (top and bottom) for the first third the tine can rival the strength of 2x2x1/4. With 1/8" Flatbar at top & bottom third it will be 25% stronger than 2x2x 1/4. Agreed square looks funny for a "fork" but choosing rectangular, your sockets all have to be custom-made because there is no ("seems like never") a tube to fit it, but sometimes you cn fit them with shims welded on. The plans use the 2.5" for the 2x2 sq. tine because that combination is one of the few "fitting" sizes. And even then, you may have to fuss with the weld flash (which is not a big deal on a short receiver) or look for the special "2.53" receiver size. Anyway, square is easier.

**What are the size options for the square 2.53 tubing that I can use as receivers. This seems like a very good option. Is there a 2.53 option for the 3x1 1/2, 2x2, 2x3, or 2x4? The avilabilty may make it easier to decide on fork dimension.

On forums, despite no pics of (reasonable) attachments actually failing you will find very little support for building that attachment appropriate to its usage, and huge support for overbuilding - it's just the way members interact on forums. Don't wanna start a "Bull Engineers in full mortal combat" over your project but you might keep in mind that the recommended max 3-pt implement weight for a 7800 is 500 lbs. Your initial desire to leave some capacity for cargo has validity. I will take a guess that the 7800 is unable to lift 900 lbs (two 55 gal drums of water) but I bet Kubota doesn't want it traveling with more than 500 lbs. Just IMHO.

**Where does the 1650 lb lift capacity come into this? I'm confused. After building this at 160-190lbs, I will only be able to lift approx. 700 lbs, and haul much less? This is not good.

To weld 1/4" thick material be sure to bevel the joints otherwise you won't get the additional strength you paid for (and will carry around). Unless you have capacity to weld with 3/16" rod etc. Do you have a welder that can penetrate 1/4" - thats a tall order for a newbie. There are times to overbuild and times not to, and not having an understanding of material strengths, that alone may be a good reason to overbuild.

*Fortunately I have a neighbor who was has welded for years and has a very large welder. He hires out at very affordable rates and is going to do this fabrication. I would have to ask him the above.

If built per the drawing ----Sodo---- would use 1/8" material for a compact tractor and don't lend it out. If you prefer overbuilt, 3/16" will be 50% heavier, cost 50% more, and be more than 50% stronger, handle the next size bigger tractor etc seems quite reasonable and prudent. Sizing that for a tractor with 1 ton lift capacity when the tractor you have weighs only 1800 lb only has downsides, (to me).

**Sodo would construct the frame with 2 1/2" square tubing @ 1/8" thickness, in place of the 3/16 called for in the plans? Lighter and less costly is good...stength?
I know you had mentioned that the plans were overkill for the B7800. Are there other areas that you would consider scaling down, as well?
Just went to Sagnaw Pipe's site and I don't see an option for the 1/8 thickness?

 

[jodebg]

LD1- Sorry, I am not see how to use the suggested 5x3x 1/2" tubing for the rece

ivers??

I'd buy steel locally. But I have some good suppliers. Doesnt hurt to check both online and locally.

Fabbing up a receiver shouldnt be hard. Or you can just buy some 5x3x1/2 wall tubing. Its 20# per ft, but you would only need a foot or so. (6" each side)

 

[Sodo]

I wonder if the "2.53 receiver size" is the ONLY sq tube internal special size

I'd make my frame from 2 x 2 x 1/8, and the tines too (maybe 3/16 tines). But what I'd do is a little problematic,,,,, because I'd build it, do a little testing and if not strong enough I'd beef it up.

If you have a little time, try to research what is the real lifting capacity of the B7800 at a point about 28 inches behind the hitch, before sizing your materials. The 3-pt is a parallelogram, but I think there is a small multiplier, for example a brush hog lifts up at an angle. This is something I may be able to help with as I now have a receiver socket on mine If can think of some heavy (known) weight and a way to lift on it, I'd try it for you.

 

[jodebg]

Sounds good-thanks.

 

[mike69440]

FYI

My forks made from 3x 1-1/2 Tubing for my L39 Bent a bit in this application. Time to straighten them with my excavator.

 

[LD1]

5x3x1/2 has an ID of 2x4. If you used 2x4 tube for the forks, they could be inserted and removed same as the plans.

 

[Mace Canute]

That is not how a 3PH works.

A 3PH is a parallelogram style linkage. There is no loss of lift force IF it is kept to a true parallel lift. Which is indeed possible on lots of hitches with adjustment of the linkages and toplink.

You do loose a little force the father from parallel the lift is, but it isnt like a simple lever. If you set up the 3PH so that the pallet forks raise in a level manner (heal raises the exact same amount as the tip), the capacity at the tip is the same as at the ball ends. (provided you have enough weight on the front of the tractor to keep it on the ground).

That's not correct. Even if it is a true parallelogram style linkage the farther out from the fulcrum the load is the more effort it takes to lift it. What changes is the hydraulic pressure required to lift it. All three point hitches that I have seen work on the principal of a Third Class lever although there is nothing to prevent them from being designed as First Class levers except possible physical space limitations. This diagram is an example of the typical 3PH.