Analysis on log splitter built

   / Analysis on log splitter built #1  

polemidis

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Winthrop Maine
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LS XG3140
I would never guessed, but look what a HUGE difference the Finite Element Analysis results to these models.
I applied 35000Newtons to the cutting edges, with the cylinder base pin location as the constraint (the red round marks at the right of the pictures)
Screenshot from 2018-03-01 17-36-47.pngScreenshot from 2018-03-01 17-36-16.png

The one at the left shows a distortion to the Z axis of 0.4mm, while the one on the right 5.5mm! In Von Mises streses the left gets 158MPa of pressure, the right one 370MPa. With yield strength of steel of 250MPa that means that the right one will deform in that extreme case.

What is the difference? The left one has the has the cylinder mount 2in inside the I-Beam, while the right one has it flush to the end.
 
   / Analysis on log splitter built #2  
What about an extention of the beam on both ends? How much extension before the stress reduction is disapated before beam ends.
 
   / Analysis on log splitter built
  • Thread Starter
#3  
What about an extention of the beam on both ends? How much extension before the stress reduction is disapated before beam ends.
I tested only one end. I think 2" in ok. For the other end I may add 1 inch, since there is grate mounted that reinforces the beam more.
That splitter is part of a firewood processor.

FYI guys the beam tested was W flange, 6.5sides with 8" web. The actual one that I will install is 8" flanges with almost 7.5"web and 1/2" thickness, skrutzed from craiglist. I thick I cannot go wrong with that :) I
 
   / Analysis on log splitter built #4  
There's more forces involved in a splinter than that. That's failed to account for what happens when a piece of wood is cut crooked or a knot hits one side of the 4 way beams. I'd overbuild the beam by a good margin.
 
   / Analysis on log splitter built #5  
I would never guessed, but look what a HUGE difference the Finite Element Analysis results to these models.
I applied 35000Newtons to the cutting edges, with the cylinder base pin location as the constraint (the red round marks at the right of the pictures)
View attachment 542116View attachment 542117

The one at the left shows a distortion to the Z axis of 0.4mm, while the one on the right 5.5mm! In Von Mises streses the left gets 158MPa of pressure, the right one 370MPa. With yield strength of steel of 250MPa that means that the right one will deform in that extreme case.

What is the difference? The left one has the has the cylinder mount 2in inside the I-Beam, while the right one has it flush to the end.

When I sanity check those two cases, it doesn't pass my eyeball tests. Either something else changed that you're unaware of, or the boundary conditions are wrong, or even the color scales aren't consistent between the two. I would not expect that much difference just by moving the cylinder mount like that.
 
   / Analysis on log splitter built
  • Thread Starter
#6  
There's more forces involved in a splinter than that. That's failed to account for what happens when a piece of wood is cut crooked or a knot hits one side of the 4 way beams. I'd overbuild the beam by a good margin.
Absolutely. The analysis is done to one step at a time :) I just posted it because I found it interested. Not as a complete analysis.

The beam I am using I think is "overbuilt" no? W8x40 for W-Beam is pretty descent imho. I may not even bother to brace the ends
 
   / Analysis on log splitter built
  • Thread Starter
#7  
When I sanity check those two cases, it doesn't pass my eyeball tests. Either something else changed that you're unaware of, or the boundary conditions are wrong, or even the color scales aren't consistent between the two. I would not expect that much difference just by moving the cylinder mount like that.

I was surprised too, thats why I bothered to post it. Nothing else changed. The only think that I would suspect, is to the creation of the mesh?? Anyway, I would never know. I have updated the model to my real size beam (W8-40) that I bought, which is bigger than the one I had modeled above. I would run a test again to see what shows now.
Can you run an analysis? I can sent you the .step file, I was wondering if the results vary a lot
 
   / Analysis on log splitter built #8  
I cannot begin to count the number of times I have seen a home-built spitter rip the wedge or cylinder anchor off the beam because it was only "surface welded" to the flange of the beam.

Huskee store bought splitters, which are some of the cheaper (but still good) ones out there dont even do that.

Cut a pocket and insert the anchor block and wedge.....see what that does for your numbers;)

splitter 1.jpg
splitter 2.jpg
 
   / Analysis on log splitter built
  • Thread Starter
#9  
I cannot begin to count the number of times I have seen a home-built spitter rip the wedge or cylinder anchor off the beam because it was only "surface welded" to the flange of the beam.

Huskee store bought splitters, which are some of the cheaper (but still good) ones out there dont even do that.

Cut a pocket and insert the anchor block and wedge.....see what that does for your numbers;)
View attachment 542171
View attachment 542172
HA! I got you! I have already done that! Its at the other side not visible from this view. Actually to say the truth and nothing but the truth, I cut the pocket mainly because of the need to adjust the 4way with hydraulics below the beam, and then realized that it helps A LOT. But I never thought of doing that to the cylinder mount!!!!! Even though its half the pressure (since it is 2 "ears") its cheap insurance. (And an excuse to put the plasma to work)!!!!

So this where I am right now. Wtf, I have so many designs now. But no money to built any of them!!!!:confused3: Even though I figured out the cutting system, I removed it for now, since the spring is almost here, and I have to start cutting. The the more risk-free way is to mount my spare chainsaw and do it manually. Anyways it saves me huuuge time and effort of making firewood. Screenshot from 2018-03-02 07-44-01.png
 
   / Analysis on log splitter built #10  
Agreed. At a minimum your color scale changed. I can't believe that moving the cylinder mount left 2 inches on the beam would have any affect at all on the left edge of the 4 way, and yet it turned from blue to red. Something isn't adding up.

Edit: this was meant to be a reply to s219
 

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