ot: unicorn or rotary log splitters?
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  1. #1
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    Default ot: unicorn or rotary log splitters?

    I have a request to make a screw type log splitter. When the guy asked, I thought he was crazy, but they are all over Youtube. Anyone have experience/advice on these things?
    thanks
    i_r_machinist

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    when you say he 'asked', do you mean:
    he's a customer that's willing to pay? who cares if they work or not, ask him for a print and charge accordingly.
    he's some deadbeat who saw something on youtube and thinks welding and machining are free? who cares if they work or not, send him down the road.
    he's a buddy asking for a favor? if you have some spare time and feel like screwing around with it....

    I can't say that I've got any experience with the rotary screw-type log splitter that you're asking about, but I'd hazard a guess that since considering all the successful commercially available log splitters are hydraulic ram types, and I routinely see screw-driven electric log splitters for sale cheeeep and 'used once' on craigslist, I'm betting it's a gimmick.
    Almost like those 'monster mauls' that are equilateral triangles and require a huge amount of effort to actually split something (and are seen almost as often as electric logsplitters on the used market and with the same degree of 'use').....

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    Farmer's sleeve getting caught in a pto shaft comes to mind. Hope he don't sue you.

    Bark Buster Log Splitter | Gather

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    The unicorn type is OSHA preferred compared to this thing:

    YouTube - Redneck Log Splitter

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    These were popular back in the 1970's.

    Any logsplitter is sitting idle at least 80% of the time,
    a hydraulic logsplitter can be used as a bending brake,
    pipe bender, and even a can crusher.

    That splitter design can't doo anything else.

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    He's a friend that is the go-between for a paying customer. So yes, I do get paid. He brought me a homemade cone that someone had hand ground some-what of a spiral on. It looks like it could be left over from the '70s.There is no way in hell I would build the complete machine.
    i_r_

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    I have one that runs off the PTO on my 1953 Ford Jubilee. It is scary fast. This particular one was built by my father. It takes 2 people to operate: One to feed it the wood and one to be ready to push in the clutch on the tractor. Since I have both, this one and a ram type one, I can honestly say the screw type is at least 5 times faster but about 300 times more dangerous. Although it is still the one I use the most.

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    I also have a unicorn type splitter, brand forgotten. It was set up on a roller stand, so that you could power it off the rear wheel of a car or truck with the other wheel on the ground. It did actually work, but it was mighty scary. There was a kill switch you were supposed to keep very handy, because if the log jammed, the vehicle could simply drive off the stand and be down the road. I've seen other versions with a flange that bolts directly to the wheel, and others that use a tractor PTO.

    The splitting itself was fast and very powerful for knotty wood, but messy and splintery, making the wood rather unpleasant to handle.

    I was given this rig back in the 1970's by someone who found it unfriendly to use, and quickly concurred. The remains of the thing have been languishing in my barn for many years. If i-r machinist would like to shorten the product cycle a little, let me know. the screw/cone is detached, and could be attached to some other shaft or flange. I imagine it's got a good bit of surface rust by now, but last I saw it was nice and sharp, and a pretty hefty piece of material.

    But really, I'd not recommend this unless you have a supply of gnarly, knotty elm or something that nothing else can get through. It's dangerous and ergonomically unpleasant to use.

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    Opinions on this design:

    YouTube - Holzspalter - Kegelspalter (Eigenbau)

    Seems if you used a VFD and had a convient kill switch, it might actually be safe for a qualified operator.

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    Default Screw type wood splitter

    When I taught machine shop at a tech college, we had a student who made one. We had a lot of 3 15/16 diameter 6061 aluminum. He made the cone out of that, and it had a replaceable point that he made of 1 1/4 inch diameter stressproof steel. We had an old LeBlond lathe with a taper attachment that could be set to cut a steep taper, and the quick change gear box could cut a one inch TPI thread. I don't recollect what happened to it after it left the shop.

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    Yup, I had one on a 1970 International Scout 800...........Worked fantastic. At 1500 rpm, in second gear it would split wood as fast as you could line em up.

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    Back in the '80's, I had one like Bruto describes with the roller stand. I'd power it with an F250 running in bulldog. We'd always scotch the front wheels with large chunks! I don't remember anything it wouldn't split, knots, crotches, etc. It was easy to use and the more wood you threw in the bed, the more power was transmitted to the splitter.
    Never had an accident, but always imagined getting a glove, shoelace or pantleg caught on that screw........Used it for several years until the sprockets finally wore out and moved to a hydraulic splitter. The only type of splitter I can imagine being more dangerous is the big waterwheel type with the wedge welded to the circumference!
    I recently watched a pto driven unicorn unit sell at auction for $35. I barely resisted the urge to bid!
    Barron

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    If I just make the wedge, am I still liable if someone gets tangled up? I'm not worried about my buddy, he's a machinist too, but I have no idea who the end user is.
    i_r_

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    i_r_, your liablity is as great as your pocketbook is deep and it doesn't matter if you are at fault or not. Lawyers know they can't get blood out of a turnip so if you have few assets you are probably ok.

    Forget about the liablity aspect for a moment and ask yourself a question. If the fellow using this splitter gets tangled up in it and gets all torn up, will I lose a nights sleep?

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    I have seen those around here and they do work really well.

    Give me a shout i_r_machinist I live near you.

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    Porchefix
    pm sent.

    gbent,
    I wouldn't lose sleep. I believe in personal accountability.
    i_r_

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    I've got one for a Gravely two-wheel tractor.

    They are fast, powerful, and once they are running that's it. No need to throw a lever every cycle. I wouldn't use it with long sleeves, but it won't crush or amputate as a hydraulic splitter will.

    Make sure you allow for a replaceable point, which is the key to easily starting a log on the cone.

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    John,
    What pitch is it? I was thinking about an 8 tpi with the insert turned to produce a buttres thread.
    i_r_

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    Quote Originally Posted by i_r_machinist View Post
    John,
    What pitch is it? I was thinking about an 8 tpi with the insert turned to produce a buttres thread.
    i_r_
    Cone, including tip, is 12" long, 4" at large end. It is a 2 tpi thread.

    The thread form is nothing standard - it appears to be a 1/4" half round groove, 1/4" deep. Flats on tops of the threads are 1/4" wide. That form continues right to the point, which makes the tip of the point look like a corkscrew.

    Buttress thread sounds fine, although at 8 tpi it may be too slow. I'm guessing that my cone runs in the 200 - 400 rpm range. PTO speed IIRC is in the 1,600 rpm range, and the cone is driven by that through a rotary plow gearbox. Horsepower of the tractor is 7.6.

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    YouTube - Unicorn Log Splitter

    Innovative design, free of runout


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