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Log Splitter Wedge Angles

Discussion in 'Firewood, Heating and Wood Burning Equipment' started by Wood Doctor, Oct 21, 2009.

  1. Wood Doctor

    Wood Doctor Edwin

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    Let's design a powered log splitter wedge. There must be an ideal pair of angles for a log splitter wedge that would minimize the force required to split the average log. Below is a schematic diagram showing the top and side views of the wedge:
    [​IMG]

    For the illustration only, the I-Beam is running vertically and to the right of the side view. This beam could be oriented either horizontally of vertically. What do you think that angle A, the wedge angle, and angle B, the slant angle of the sharp edge, should be?

    I imagine the tendancy for the wedge to stick in tough logs should also be considered when setting these angles, in addition to the splitting force. WDYT?
     
    Last edited: Oct 21, 2009
  2. Curlycherry1

    Curlycherry1 Addicted to ArboristSite

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    I ran thousands of cords through a wedge that was about 2" to nothing taper on a 1" thick hunk of steel. So 2" back from the tip the steel was full thickness. A previous box wedge 3" wide at the widest point tore off the I-beam twice before we went with the flat steel. I tore the flat steel in half once, but the weld held.

    The front of the wedge needs to be 90 degrees to the beam. If it tapers down in forces the wood into the beam and leads to undue pressure for the ram to compensate for, and if tapered at an obtuse angle the wood will ride up off the wedge. These are observations I saw with the splitter I lived on for over a decade.
     
  3. LarryTheCableGuy

    LarryTheCableGuy Addicted to ArboristSite

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    Sloped away from the beam (as indicated in the diagram above) allows the wedge to begin to split gradually, instead of all at once. It is a proven design that works very well.


    .
     
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  4. Curlycherry1

    Curlycherry1 Addicted to ArboristSite

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    We tried it for a while and with some really knarly wood it would tend to ride up. I did not like that and so we went with a perfectly vertical wedge face.

    I had a theory that with the tapered edge wedge we got more slivers and trash from splitting. My theory was that as the wood went into the wedge the block would start to split with the wedge and then split along its natural cracks, but then soon the wedge would force a straight split top to bottom through the log. Some of those crooked first splits of the wood would fall off and lead to more small tiny pieces, thus splitter trash. When we went back to the perpendicular wedge a lot of the trash went away. Unfortunately there was no way to back and do a controlled experiment. I mentioned the lack of trash with the vertical face wedge to my dad and he said he noticed it too.
     
  5. Wood Doctor

    Wood Doctor Edwin

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    Good discuussion, men. We've got the ball rolling. My own experience with three splitters is that
    (1) the splitter with a wedge angle that is too small (say 25 degrees) caused lots of stuck logs that are a mess to remove.

    (2) the splitters with 90-degree slants (no angle at all) required the most thrust from the hydraulics. A 75-to 80-degree slant angle seems to reduce the force required to get the split started.
     
  6. Junkfxr

    Junkfxr ArboristSite Operative

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    I have tried all sorts of wedges over the years and still haven't found the "perfect" one yet. The best one so far has been with a face angle of about 15 degrees (or 75 degrees depending on which way you measure it) so that it starts splitting the wood from the outside edge with scollops in the side to keep the wood from riding up off of the wedge like the ones on the left.
    <a href="http://s49.photobucket.com/albums/f255/junkfxr/?action=view&current=P1010014.jpg" target="_blank"><img src="http://i49.photobucket.com/albums/f255/junkfxr/P1010014.jpg" border="0" alt="Photobucket"></a>
     
    Last edited: Oct 21, 2009
  7. turnkey4099

    turnkey4099 Tree Freak

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    I, too, see no advantage to a sloped wedge. If you watch wood split, the only time the knife edge contacts wood is at the start of the split (or when shearing aknot/crotch). the split runs well ahead of the knife. Once started any force causing the wood to ride up (or down) disappears. The point about teh slope causing splinters, etc. sounds right to me but what do I know.

    There is also the unfortunate fact that very few chunks run through have an exact 90 degree cut

    Harry K
     
    Last edited: Oct 21, 2009
  8. Wood Doctor

    Wood Doctor Edwin

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    What About Contact Area?

    Ever notice that when you split wood that has not been cut at 90 degrees, you tend to put the long end toward the base of the wedge or at the top rather than sideways?

    Indirectly, you are setting up a sloped (slanted) angle with the wedge. Thus if the wedge is already at a small angle, when a 90-degree log is placed on the splitter, you reap the harvest that LarryTheCableGuy was talking about in Post #3.

    Then there is another point. Many logs will stall a splitter out if the entire wedge width hits the log at once. If, on the other hand, only half the wedge hits the log on contact, the splitter will handle it because it can exert more pressure on the smaller contact area (psi.). Seems to me that the sloped wedge angle would automatically reduce the initial contact area. Hmmmm...
     
  9. Curlycherry1

    Curlycherry1 Addicted to ArboristSite

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    Sorry but I can't relate. Every splitter I ever used was home-made and built like a tank and every one of them could cut a 12" log off sideways. It was the way we tested them. That old splitter I showed a photo of a while back stopped about maybe 3 times in its entire life. That was one mean son of a gun splitter. :):)
     
  10. 371groundie

    371groundie AboristSite Guru

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    i have an old model 52 John Deere splitter. 5 horse B+S and its hard to stop. the wedge is mabey 1.5 inches thick at 4inches deep. and the TOP of the wedge is tilted mabey 5 degrees TOWARDS the ram. the wood doesnt ride up and you still get the gradual start spoken about above.

    i prefer a narrow wedge that slices rather than prys the wood apart. and i dont have to worry about it getting stuck on the wedge because it gets pushed through by the next peice. knots, crotches, doesnt matter at all. even that little 5 horse motor can push it through. i think the slicing action results in less splintery peices. which is handy since i hardly ever wear gloves.
     
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  11. Wood Doctor

    Wood Doctor Edwin

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    I respect your opinion and I am sure that monster is a powerful splitter. However, what we are looking for is efficiency. Several engineers have told me that proper log splitter wedge design can save lots of horsepower, pump capacity, and cylinder size. I firmly believe that this is true.

    If our forum can address and advise on the wedge angle (nobody thus far has) and the optimal slant (slope) angle, I think that many here could design and build their own splitters that would work much better without using massive engines, pumps, and cylinders. That's the objective of my post.
     
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  12. angelo c

    angelo c Addicted to ArboristSite

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    Dr.

    what about a wedge designed similar to the fiskars splitting axe, with a delayed secondary perpendicular "wedge" or wings. Seems to work well with the maul design...

    I like the real narrow "blade" design of the Super Split(slices) as opposed to the Massive Maul 4" wedge of the TW-6( just scares the wood into shattering)

    I also like the wedge on the rail as opposed to the wedge on the ram
    A
     
  13. Junkfxr

    Junkfxr ArboristSite Operative

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    I have been a card carrying machinist and welder for topside of 20 years and most of my working career has been in manufacturing plants. I have had to deal with mechanical engineers on an almost daily basis. My opinion is that if an engineer hasn't spent at least 10 years in the field or on the shop floor working on or at least with the product that he is specializing in at the time, they really don't have a clue. Most of what they come up with is theory, and reality and theory are usually two seperate entities. My experience has been that there is no ideal wedge design. It all depends on the kind of wood being split. Nice straight grained stuff like red oak pops apart really easy and a wide tapered wedge will work good and really speed up the process but twisted grain and stringy stuff like white oak, gum, elm, etc. needs a thinner wedge with a sharper angle on it to more slice through it. Yes, it takes longer for having to push the wood all of the way across the wedge but that wood doesn't bust apart as easy as straight grained wood does. My thoughts on building a spliiter is to use the biggest cylinder, pump and engine combination that you can afford and use a thin wedge. that way you have the speed of the high flow rate to speed through easy stuff and the power of the large diameter cylinder to slice through the really tough stuff. Now with that said, I have backed up against the wall so let the beatings begin.
     
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  14. Steve NW WI

    Steve NW WI Unwanted Riff Raff.

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    Mine uses a fairly narrow angle, about 45° measured by the original drawing, and the push plate comes nearly flush to it at full extension, with blocks welded to the sides that actually extend past the cutting edge to cure any sticking problems. I couldn't find any pics right now, so I drew up a quick chickenscratch to show what I mean:

    [​IMG]

    I'm sure that an angle on the vertical would lower tonnage, but I'm on the fence on the riding up/binding part. I'd probably have to see it to beleive one way or the other. I plan on angling the wing wedges for easier splitting if I ever make a 4way.
     
  15. wkpoor

    wkpoor Addicted to ArboristSite

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    Boy, now there is another can of worms to open. Move the wood or move the wedge?????
     
  16. SWI Don

    SWI Don AboristSite Guru

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    My wedge is a 12" tall Northern Tool wedge with some angles attached to pop wood apart that will do that.

    The Northern wedge is approx 30° included angle and the compound is at 76° included.

    I am pretty happy with the performance but I have dented the 1/4" thick angles that make the compound splitting very tough wood at 30 tons of force. Is it optimum? I don't know that I would claim that, but it works.

    The other debate is knife wedge vs. compound wedge vs. straight taper wedge (as per Wooddoc's illustrations).

    Don
     
  17. trialanderror

    trialanderror ArboristSite Operative

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    i've done it one way and the other.


    But here's some food for thought....my splitter is setup so i can drop in a 2nd wedge and split from both sides at once. And holy does it make a HUGE difference of what a splitter capable of...gnarly knotty oak, 42" rounds...think again.... :)

    for a while i was keeping progress by welding a sliver of pipe to my ram, which would hold a splitting wedge, so i could split from both sides, worked fantastic, just a little wild, sometimes it'd go sideways. So i did some fabbing and now i can drop in a 2nd wedge, throw in some pins, and wha-bam, double end splitter....pull pins, drop in something else, wha-bam, 80ton press....endless possibilities now.
     
  18. Curlycherry1

    Curlycherry1 Addicted to ArboristSite

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    Firewood processors (Timberwolf, Multitec, CordKing) always move the wood through a fixed wedge. They are designed for production. There, it is settled, done! :)
     
  19. Wood Doctor

    Wood Doctor Edwin

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    Curly, we ain't driving a short bus on this here thread. So far, I have angle A running at 42 degrees or so and angle B (the slant) running at 75 to 115 degees, 90 being no slant at all.

    Here's something interesting, planer irons are sharpened at at 42 degrees. Maybe we can borrow some technology from the woodworkers.

    We also know that well over half the splitters being sold today are made with the wedge moving and the toe plate stationary. That design allows for the easiest swing up from horizontol to vertical in order to accommodate the monster rounds. One has to wonder if that design also changes the optimal wedge angle requirements.

    Forum, any thoughts on this? Remember, the ideal wedge design will help prevent a 2-stage pump from dropping into the second stage, speed the splitting process, save fuel, and reduce equipment wear and tear. That's why were kickin' this thing around. Our own experience may be worth a dozen theories.
     
    Last edited: Oct 22, 2009
  20. Curlycherry1

    Curlycherry1 Addicted to ArboristSite

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    That is an interesting theory and using a quickie CAD program I drew up what my old splitter had for a wedge angle (from my memory) and it came out to 38 degrees. Knowing the welder that made my splitter and the fact that he was a machinist for over 50 years by the time he built my splitter, I bet he was shooting for that angle of 42 degrees. I am willing to bet that is what the angle was and my CAD skills are not good enough to get the angle right.

    That same welder/machinist proposed to us that we make a wedge that was curved on the front much like an axe, but he said it was too much of a PITA for him to make, and as he pointed out we had never stalled our's only about 3 times, so why screw with it.

    Homeowner woodsplitters with the wedge on the ram have the advangtage of being able to be tipped down, but commercial splitters made to handle big wood have a lift. Two different categories of splitters homeowner's vs commercial, apples to oranges. Commercial operators want the split wood to be gone from the splitting area so they pass it through a wedge and it drops off onto a conveyor and is taken away. A commercial splitter with a wedge on the ram would require an operator to handle every piece of wood to get it onto a conveyor. That is wasted energy.
     

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