Question about steel strength??

[Sodo]

go sit on LD1's 1100 lb bush hog that'll clear it up! :laughing::laughing::laughing:

 

[LD1]

I may have to change my opinion! I think I will do a little more work on it first before I do so, just to be absolutely sure. (I'm stubborn!) Either way, I'll be back to either gloat or eat crow.

At least you are thinking about it again.

I know there have been many threads on the topic, and many people just a stubborn. If I may ask, what was said that finally convinced you to think about this again? I know there have been many different examples and wording of basically the same thing.

 

[jodebg]

LD1...A battle almost won! Almost had to take this one outside.

Working on final design/material list and have a couple of questions.

For the forks, how do the strenght comparrison numbers differ between a
3x2 x 1/4 wall.... and a.... 3x2 x 3/16" wall?

Receivers: What dimension can be used for the receivers for the 3x2" forks?
I see a 3.5x2.5 x 3/16" tube which will leave an 1/8" gap...gap too large?
3/16" thickness may not be strong enough for the receivers?

Or, I could build receivers out of two 4.5" steel plates with welded 1/4" dividers.
Would the weld joints along the dividers get in the way when sliding the
forks in and out of the receivers?

1/4" thick plates strong enough for the receivers?

Thanks

 

[Xfaxman]

John, since you are building your own, consider this design.

It would be lighter than all the extra receivers. You can still make the forks from tubing.

 

[Sodo]

think about how a forklift mast works. shifting the load farther out on the forks doesnt increase the downward force on the hydraulic cylinder. But does increase the forces on the rollers.

This is a good example. If the input distance is the same as the output distance, the leverage, and thus the forces, are the same. (incremental!)

In reality the 3-pt actuator mechanism produces a position-dependent output, and the unequal lengths of the //ogram produce another position-dependent output too, but the basic premise of the forklift mast-vs-//ogram is a good comparison.

========================

As said before 3x1.5x3/16,,,,, the i4=.466 and 2x2x1/8 was .456, these sections have the same bending strength. 3x1.5x1/4, the i4 is .541, strength increase of 18% ( but weight is double the 2x2x1/8 ) You can compare strengths in a basic way with the i4. (as in i4 = .541 is 18% more than .466)

I will guess that Mike69440's yellow forks are 3x1.5x1/4" (post #78 on page 8 ) and you can see what load it takes to bend i4=.541 Now try to imagine what load it takes to bend i4=.91,,,,, or 1.00 :shocked:

The rect tubes have a generous outside radius. I do not see the welds touching the rounded corners of the rect tubes. Making the sockets from 1/4" is strong. There is no "structural need" for 1/4" anywhere but the attachment points ought to be thicker (3/8) or braced 1/4", because they can get knocked around in the yard especially if the attachment is "heavy".

It can get difficult to weld inside those receiver pockets.

You can use tubing with slop. It actually works better in the end. You weld "beads" on your fork tines at the four (or 6) contact points. Grind it flat to the proper thickness. This too is dependent on the craftsmanship of your neighbor, but it's very easy to do and takes a fraction of the time to construct the sockets, which will NOT be adjustable.

 

[jodebg]

Sodo-What I was looking for is the numbers for the 3x2 x3/16" wall and 3x2x 1/4" wall dimensions
to fill in the list that LD1 posted for comparrison.

Looking at the chart, I did not see a rectangular tube dimension that the 3x 1.5 would fit into?

Here's what he posted:

Using the moment of inertia calculators isnt exact for tubing, cause it assumes squared corners (more material than rounded). So lets use actual numbers.

3 x 1.5 x 3/16 tubing I= 0.488

2x2x1/4 ..................I= 0.77

2x4x1/4...................I=1.54

I would also assume the max load on 1 fork, to represent a real world worst case scenario. Never know when you are gonna be lifting a log or something to the max, and 1 fork may slip off, putting all the load on the other.

So......here we go.

3x1.5 fork 48" long @ 1000# will deflect 2.6"
................28" fork..............................0.5"

2x2x1/4........48" long...........................1.65"
...................28"............................ ........0.33"

2x4x1/4.........48"..................................0.82"
.....................28".......................... .......0.16"

 

[LD1]

3x2x1/4 is 1.15 and weighs 7.11# per ft
3x2x3/16 is .977 and weighs 5.59# per ft

 

[BukitCase]

Joe, sorry I'm just now getting back - tax time, etc...

That 2.53 stuff you've been drooling over, AFAIK is ONLY available in SQUARE tube because that's what standard hitch receivers use.

My suggestion is something I've used a couple times with good results - build your OWN custom sized receivers, as many as you need, and weld them into your frame. This way you get the amount of clearance YOU need AND a receiver that isn't the weak link AND a PITA.

Here's how I do it - and if you're not experienced enough to know where, when and how much to weld and you're gonna have an experienced weldor do it, that's fine - I don't know what you're capable of, so take this sketch for whatever it's worth to you... Steve

 

[jodebg]

Working on the final details. Just measured the 3ph lower arms in the lowest
position. To the center of the pins it measures 11 1/8" off the ground.

In locating the mounting brackets on this set of forks, how much should
I add to this dimensions?

I was thinking of adding 2" (13 1/8") in order to
gain an additional 2" of reach if the tractor was not on level ground.

Is an additional 2" correct?

And, which of the 2 holes in the lower arm mounting bracket should I use for this
measurement? I'm thinking the lower holes for the lower arm bracket?

Which hole should I use in the upper link mounting bracket at the parallel position?

 

[LD1]

2" sould be plenty. But I dont know how un-even your terrain is.

The lower link hole for measurements...whichever one you use most frequently

Top link, I would go for parallel in the top hole. Then using a lower hole will cause the fork tips to pitch up more. I cannot think of a time where you would ever want the fork tips to pitch down when raising.