Question about steel strength??

[jodebg]

Working on plans to build a set of 3PH forks.

For the tines, the plans call for 2 x 2x 1/4" tubular steel- 43" long.
They have been load tested to over 2000lb lift capacity in this design.

I was considering using 3" x 1.5" x 3/16" inplace of the 2x2 called for in the plans.
This seems to be a better dimension for tines.

The steel guys did not know if the 3 x 1.5" was available in 1/4" thickness?

My question is how strong is the 3 x 1.5" tubular steel compared to the 2 x 2 x 14" sotck?

 

[ishiboo]

Working on plans to build a set of 3PH forks.

For the tines, the plans call for 2 x 2x 1/4" tubular steel- 43" long.
They have been load tested to over 2000lb lift capacity in this design.

I was considering using 3" x 1.5" x 3/16" inplace of the 2x2 called for in the plans.
This seems to be a better dimension for tines.

The steel guys did not know if the 3 x 1.5" was available in 1/4" thickness?

My question is how strong is the 3 x 1.5" tubular steel compared to the 2 x 2 x 14" sotck?

Structurally, the extra 1" width is basically just extra weight.

The 25% loss in height, however, coupled with a 1/16" loss in wall thickness, will be a pretty big structural loss.

If you can, I would go with 3x2x.25" or the original 2x2. Otherwise your plan will be okay, you'll just have weaker forks.

By the time you buy that tube steel though, you could probably find forks alone on Craigslist for the same price... which will be solid steel, tapered, and quite strong.

 

[LD1]

No go on the 3x1.5 (assuming you plan on laying it down so they are only 1.5" high). Just aint gonna be strong enough.

I even have my doubts about the 2x2 @ 43" long. but if thats what the plans call for, I wouldnt go any less.

Your proposed 3x1.5 is only about 1/2 the strength. Even if you could get it in 1/4", it still wouldnt be anywhere near as strong as the 2x2x1/4. Actually, 2x2x1/8 wall tubing would be stronger than your 1.5x3.

For forks though, I like 2x4x1/4 tubing. Nice wide fork. And quite a bit stronger than 2x2x1/4 tube

 

[s219]

Working on plans to build a set of 3PH forks.

For the tines, the plans call for 2 x 2x 1/4" tubular steel- 43" long.
They have been load tested to over 2000lb lift capacity in this design.

I was considering using 3" x 1.5" x 3/16" inplace of the 2x2 called for in the plans.
This seems to be a better dimension for tines.

The steel guys did not know if the 3 x 1.5" was available in 1/4" thickness?

My question is how strong is the 3 x 1.5" tubular steel compared to the 2 x 2 x 14" sotck?

You'd be losing both height and thickness with the 3 x 1.5 x 0.1875, so they won't be as stiff as the 2 x 2 x 0.25". Offhand, you lose about 25% due to thickness (all else equal) and 44% due to height (all else equal). Combined, you'd have to compute the area moment of each cross section, but it will probably be in the 50% range. So yes, quite a bit less strong by the back of my envelope.

 

[LD1]

IF you want to know specifics, use a moment of inertia calculator for rectangle tubing. Plug in the numbers and see what you get. What you get is directly related to strength.

2x2x1/4 tubing is ~.91
3x1.5x3/16 is ~.53

the 2x4x1/4 I mentioned is ~1.68

So, 2x2x1/4 is "almost" twice as strong as the 3x1.5. And 2x4x1/4 is almost twice as strong again

 

[jodebg]

Thanks for all the great information.

I did not expect that the loss of strenght would be that great.

With the limited lift capacity of my 30hp Kubota B7800, I am attempting to
eliminate weight wherever possible. Around 760 lbs. on the FEL and 1650 on the 3PH.

I also like the profile of the 3 x 1.5" steel for the forks.

What if I milled some quality/straight grain lumber and inserted the lumber tightly into
the open cavity in each tine. Straight grain lumber can be good and stiff and add some
addtional strength to the steel? Bad idea?

 

[LD1]

What if I milled some quality/straight grain lumber and inserted the lumber tightly into
the open cavity in each tine. Straight grain lumber can be good and stiff and add some
addtional strength to the steel? Bad idea?

Sounds like more effort than its worth.

Id go with what is proven.

 

[jodebg]

What happened tho this...

".........there is only one way to find out."
"Ok, hold my beer and watch this..

 

[Sodo]

What if I milled some quality/straight grain lumber and inserted the lumber tightly into
the open cavity in each tine. Straight grain lumber can be good and stiff and add some
addtional strength to the steel? Bad idea?

Wood will add very very little because it will do all its initial deflection barely even adding to the strength. Plus it can have no fixation at its ends. For the same weight it would be much stronger to add steel. Add flat bar at the root of the tine (top and bottom). Maybe weld the top one entirely before welding the bottom to pre-tension it in the upward direction (speaking of wood,,,, its like a woodie ).

If you are intent on minimum weight (and enjoy craftsmanship or making your projects take longer) step the thicknesses of your fork tine material. The root being 1/4" thick then 25% out, switch to 3/16", then 1/8" for the final half. I'd do cuts/welds on 45deg. But you will need full confidence in your welds (not to mention thick forum-skin)! Heh heh,,,,,,, Sorry guys dunno why this came to me.



If you like 3x1.5 x 3/16" then adding another 3" x 3/16" plate top and bottom at the root of the fork tine should be stronger than 2x2x1/4. I'd holesaw a few 3/4" holes in the plate center every 4-6 inches and weld up the spots.

Its my opinion that a B7800 will have very much diffuculty bending a 2 x 2 x 1/4". IMHO you can make the 3x1.5 work if you beef up the first 25% or 33%.

 

[Morning Wood]

The wood won't help one little bit

 

[Sodo]

Morningwood you are on it! :laughing::laughing: Note to self, keep on topic, OP wants usable info in his thread...

 

[LD1]

What happened tho this...

".........there is only one way to find out."
"Ok, hold my beer and watch this..

Thats is only for the unknown.

Knowing what you want, its known that if you use 1.5x3 tubing it will fail far before 2x2 would

Wood will add very very little because it will do all its initial deflection barely even adding to the strength. Plus it can have no fixation at its ends. For the same weight it would be much stronger to add steel. Add flat bar at the root of the tine (top and bottom). Maybe weld the top one entirely before welding the bottom to pre-tension it in the upward direction (speaking of wood,,,, its like a woodie ).

If you are intent on minimum weight (and enjoy craftsmanship or making your projects take longer) step the thicknesses of your fork tine material. The root being 1/4" thick then 25% out, switch to 3/16", then 1/8" for the final half. I'd do cuts/welds on 45deg. But you will need full confidence in your welds (not to mention thick forum-skin)! Heh heh,,,,,,, Sorry guys dunno why this came to me.

View attachment 417237

If you like 3x1.5 x 3/16" then adding another 3" x 3/16" plate top and bottom at the root of the fork tine should be stronger than 2x2x1/4. I'd holesaw a few 3/4" holes in the plate center every 4-6 inches and weld up the spots.

Its my opinion that a B7800 will have very much diffuculty bending a 2 x 2 x 1/4". IMHO you can make the 3x1.5 work if you beef up the first 25% or 33%.

Adding a 3/16 plate top and bottom would certainly increase strength ALOT. And would give an overall fork thickness of 1-7/8" thick and 3" wide. So why not just buy a 2x4 or 2x3 tube and save alot of time and effort.

 

[jodebg]

Points well taken. Love your slogan, though!

Would be nice to find a used set of forged forks, but so far I have not found a set.

 

[Sodo]

Knowing what you want, its known that if you use 1.5x3 tubing it will fail far before 2x2 would

Based on the 2x2x1/4" being 1.7 times stronger than 1.5x3x3/16",,,, this is "sort of true". But there is not enough information here to "fail" the 1.5x3 for this application.

The output of the 7800's 3-pt hitch is 1650 lbs at the hitch. This 1650lbs lifting force diminishes rapidly as distance from the hitch increases. I'm going to make a guess that if the 3-pt lift arms are only 10 inches long, that you would have about 825 lbs capacity. Certainly just one tine of the 1.5x3 tines can hold that. At 20 inches long you have 550 lbs capacity at the end. At 40 inches you have 330 lbs capacity.

It's my gut feel that you could use the 1.5x3, and probably 1.5 x 3 x 1/8 if you doubled the first 10 inches. Point being that the forks don't have to be heavy for a SCUT. Solid, forged forklift forks from a 5,000 lb forklift ($200/pair used?) would be overkill but can be free if you know lotsa folks with 'stuff' ,,,,, While they could be 'free' they will require a lot of "fabrication" to "attach", and a lot of effort to move around the yard when NOT on the 3-pt.

Engineering can solve this, by example or theoretical or both. Jode you have options for weight carrying capacity, tare weight of the attachment (which reduces lift capacity as you said), ease of assembly, materials available, these are all considerations. Might be useful to know the thinnest material that can support the output of the 7800, then just double or triple the section.

 

[LD1]

The output of the 7800's 3-pt hitch is 1650 lbs at the hitch. This 1650lbs lifting force diminishes rapidly as distance from the hitch increases. I'm going to make a guess that if the 3-pt lift arms are only 10 inches long, that you would have about 825 lbs capacity. Certainly just one tine of the 1.5x3 tines can hold that. At 20 inches long you have 550 lbs capacity at the end. At 40 inches you have 330 lbs capacity.

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).

 

[Sodo]

oops yeah you're right. :ashamed: :ashamed: :ashamed: If the lift goes up 5 inches at the hitch, if goes up 5 inches at the end of 43 inch fork tine. No multiplier.

However the end of a 43 inch tine is probably same as the 7800's wheelbase. With the tractor weight 1800 lbs, 900 lbs on the end of a 43 inch tine might lift the front wheels up.

 

[2458n]

Forks are available 42 inch forks should cost you 100.00. You have to go to a auction or a place that does tow motor work. A real factory has a schedule for replacing used forks. The place I worked at last had the original 40+ year old forks on stuff.

 

[otlski]

Hey Joe,

Three thoughts...

One, Logan steel in Meriden/Wallingford has a walk-in store. All steel is about a buck a pound which is about the best you will get in Connecticut. Large selection.

Two, there are lots of forklift places on the Berlin Turnpike who have old forks laying around. They don't give them away however.

Three, I have seen them on Craig'sList but you really need to use Search Tempest to find them across several listing areas.

Looks like we are finally able to see bare roads around here. In a few weeks grass may be visible. See ya around.

Dan

 

[PILOON]

What will work better is 2 X 4" (1/4") channel with the flat side up and taper the 2" sides back 6" or so at the 'tips'
That is a reasonable priced material, stocked everywhere.
Your biggest challenge will be at the heels where you need good corner bracing (like triangulation with side plates).
On my CUT I designed them to be clamp on to my FEL bucket and I can lift as much as my FEL can handle.
While you said 48" long 28" will lift a 48" pallet if that pallet is evenly loaded.
48 up front is awkward so consider whatever is the shortest you can get away with.
Also with forks the load being way up front of a FEL C. of G. the capacity is way less, like as much as 50%.

OOPs see that you want 3 point, but basics still the same except heel triangulation is less of a problem as that would be offside and less of a hindrance.

As said, capacity will be lower than the actual lift force capabilities with lots depending on load distance from the rear axle.
If pressed I know how to calculate those C of G loads.

PS, I used to sell fork lift trucks.

 

[jodebg]

Hi Dan-

Small world, again. Talk to you more here, than when you pass by.

Yes, it's good to see the snow and ice going in the right direction-away.

Love to have you take a look at the plans that I am thinking about using.

Thinking about modifying the design to fit both the FEL and 3PH, with
removable forks and being able to use as a log skid, as well.

Thanks for the name of the steel seller. The Pine Meadow store charges around 1.30-1.40/lb.

Any names of the pallet fork places that may have old forks?

John

Hey Joe,

Three thoughts...

One, Logan steel in Meriden/Wallingford has a walk-in store. All steel is about a buck a pound which is about the best you will get in Connecticut. Large selection.

Two, there are lots of forklift places on the Berlin Turnpike who have old forks laying around. They don't give them away however.

Three, I have seen them on Craig'sList but you really need to use Search Tempest to find them across several listing areas.

Looks like we are finally able to see bare roads around here. In a few weeks grass may be visible. See ya around.

Dan