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Pneumatic Log Splitter... Need your guys help!

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Unread postAuthor: D_Hall » Thu Jan 14, 2010 10:23 pm

jrrdw wrote:Yea, it could be done but honestly hydraulic is the way to go.

I'm gonna side with jrrdw on this... Pneumatic could be done, but it's an excellent way to cause serious bodily injury. Difficult to control in all circumstances, blah blah blah. A pneumatic log splitter is something I would be utterly terrified of (and for perspective, I've drilled 12" diameter holes through 40 ton blocks of high explosives....when I say it scares me, remember that I do have some experience with high energy environments).
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Unread postAuthor: Dgealy » Thu Jan 14, 2010 10:33 pm

Please, oh god please don't build a pneumatic log splitter. Once the wedge starts to split the thing, it'll be so weekended, the pressure will just force the ram right through the log ridiculously quickly, possibly destroying the ram and flinging the halves in opposite directions.

They use hydraulic for a reason, because it is controllable. Sure you can split logs, but not practically, and not safely.
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Unread postAuthor: ammosmoke » Thu Jan 14, 2010 10:43 pm

The way I see it, Poland Spud and psycix were on the right track. The piston doesn't neccessarily need to be fast. Basically, it would seem that you could implement a design similar to a hydraulic one, but replace the power source with air. A super fast dump is not necessary or wanted in this situation. Frame pieces could be put in place to catch the logs, and it could be remotely actuated. If done correctly it should be just fine. If it was to be constructed like a piston valved cannon, the wedge would probably fly through the log and into the frame behind it, causing fragments of the wedge to go who knows where.... Unless, the part that held the log was in place was out of reach of the wedge. Just some practicalities to be taken care of... I think you should be very careful in your designing if you are to pull this off.

EDIT:

You would need a blowgun type valve to introduce pressure. You don't want super high flow.
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Unread postAuthor: spudkpi » Thu Jan 14, 2010 10:49 pm

Hmmm.... this is why I put it on here for some brainstorming. I will post the final plans for approval. I have an idea for a slow leak system that will do it. I know hydraulics may be easier... but more fun? I think not :wink:
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Unread postAuthor: POLAND_SPUD » Thu Jan 14, 2010 10:54 pm

@dgealy... it's not something that can't be fixed, for example with a simple flow restricting valve
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Unread postAuthor: D_Hall » Thu Jan 14, 2010 10:57 pm

ammosmoke wrote:The piston doesn't neccessarily need to be fast.


The problem is that unless you're going with a pneumatic/hydraulic hybrid system (easy to do, but only desirable in a very few niche applications) you can't control that piston effectively even with a hypothetically fast closing valve that severs air flow the moment a problem is encountered.

Thought experiment.... Your wedge is slowly being driven through a log. The log has a knot in it that makes it tough to split. The wedge goes halfway down and lodges. The pressure increases...and increases...and increases. Suddenly, the knot gives... And the resistance of the log goes to something only a very small fraction of what it was before. Now you have a piston half full of high pressure air. Even with zero air flow into the piston, you've now got a situation where that piston is going to accelerate like nobody's business.

If this thought doesn't give you pause....
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Unread postAuthor: ammosmoke » Fri Jan 15, 2010 12:59 am

D_Hall wrote:
ammosmoke wrote:The piston doesn't neccessarily need to be fast.


The problem is that unless you're going with a pneumatic/hydraulic hybrid system (easy to do, but only desirable in a very few niche applications) you can't control that piston effectively even with a hypothetically fast closing valve that severs air flow the moment a problem is encountered.

Thought experiment.... Your wedge is slowly being driven through a log. The log has a knot in it that makes it tough to split. The wedge goes halfway down and lodges. The pressure increases...and increases...and increases. Suddenly, the knot gives... And the resistance of the log goes to something only a very small fraction of what it was before. Now you have a piston half full of high pressure air. Even with zero air flow into the piston, you've now got a situation where that piston is going to accelerate like nobody's business.

If this thought doesn't give you pause....



Yeah... Lol... Rubber bumpers? Haha. Yeah... I don't think I'd want to operate this thing either... Unless I was behind lexan or a concrete wall. Both of which are expensive and impractical unless they were pre-existing. I think standing next to this thing would be the equivalent of standing next to the target of a large cannon. You might not get hurt, but... It is still scary. Yeah... I don't feel comfortable about this thing anymore either. As far as making hydralics go fast, it isn't terribly hard to be honest. Ever watched an excavator at work? They don't move too slow. That said, I'm not going to support the pneumatic idea anymore...
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Unread postAuthor: POLAND_SPUD » Fri Jan 15, 2010 1:27 am

@D_hall
I was aware of that problem.. the idea was to use the valve on the other side of the air cylinder... not the one being pressurised

and yes I know it won't eliminate this effect completely...
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 15, 2010 1:45 am

spudkpi wrote:And JSR... what program do you use to draw your cross sections?


As my Eastern European compadre pointed out, simple MS paint. Great tutorial here that will let you make the most of it ;)

Or you could build a launcher that shoots the logs onto a target that is a wedge. Just saying...


Talk about thinking outside the box, I genuinely lolled :D

I agree that it's not the safest option, but with adequate screening I think it's a doable and fun project. If you build to large diameters (say 3" 'barrel' in a 4" chamber) with a fast piston valve you'll have tons of power even at say 50 psi, it will put your average axe-wielding man to shame.

Another avenue to explore that's probably simpler to make would be to have an actual axe fitted to a pneumatically actuated rig, a bit the the "sword robot" that the Mythbusters used a couple of times.
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Unread postAuthor: spudkpi » Fri Jan 15, 2010 4:48 pm

Got pics and a video of what the hydraulic one looks like that my father built... works pretty well. All the clamps and whatnot are temporary just to make sure it works before we do anymore. Eventually it will be adjustable and have a spring foot pedal so its easy to use... kudos to my dad for doubting his idea.... I still think a pneumatic one would be sweet! Think about the speed :twisted:

Here's the video haha:

[youtube]http://www.youtube.com/watch?v=XSpjUXz4hyU[/youtube]

Edited by jrrdw.
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Unread postAuthor: spudkpi » Fri Jan 15, 2010 10:02 pm

D_Hall wrote:
Thought experiment.... Your wedge is slowly being driven through a log. The log has a knot in it that makes it tough to split. The wedge goes halfway down and lodges. The pressure increases...and increases...and increases. Suddenly, the knot gives... And the resistance of the log goes to something only a very small fraction of what it was before. Now you have a piston half full of high pressure air. Even with zero air flow into the piston, you've now got a situation where that piston is going to accelerate like nobody's business.

If this thought doesn't give you pause....



A blowoff valve that will go at say 100 psi so as to prevent something like above from happening? If an irregular growth pattern in the tree jams a log it will popoff at 100 psi and you just toss the log and setup a new. I will use large diameter pvc and pressures around 75 psi. I have a regulated co2 system to run it.
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Unread postAuthor: POLAND_SPUD » Fri Jan 15, 2010 11:25 pm

Think about the speed
uhmm I've never seen a log splitter so tell me is speed really that dangerous or not ?

Is it going ot be used indoors or outdoors ?

now getting back on what D_hall said... I've been thinking about this more...

in vast majority of cases the wedge would lodge at the very beginning of its travel, wouldn't it ? if that's the case then the problem he mentioned isn't as dangerous because only a fraction of cylinder's internal volume will be pressurised (so it won't accelerate that fast)

EDIT
hmmm when you split logs with an axe you rely on speed right ? so it can't be such a big deal... hmm even if it is (as I said earlier I've never seen a log splitter so IDK much about them)

couldn't you just mimic the way a normal axe works and build one that would rely on speed not on tremendous force of a large diam. air cylinder ?
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Unread postAuthor: USGF » Sat Jan 16, 2010 12:07 am

Unless you are splitting really small sticks, a 5 or 10 ton pneumatic cylinder is gonna be large and expensive. You can get multi tier cylinders that will work but they cost a lot. I'd use a hybrid with an oil filled side opposite the air driven side. The oil would go to an oil over section with a flow control valve. Really, if you are gonna go that far, it would be easier to go all hydraulic.

Take a look on Google images all the splitters there. You will likely have to beef up the frame. Commercial ones use I or H beams for a good reason.

Have fun, be safe.

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Unread postAuthor: spudkpi » Sat Jan 16, 2010 10:33 am

This is all coming together into a pretty good idea I feel like. I would have a strong frame and a large diameter low psi piston to split them. With a blowoff valve on the one side so it cannot over-pressurize. And if the frame was cylindrical with an opening for the logs or something like that to make it safer. It will have a remote to activate the pressure for sure.
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Unread postAuthor: psycix » Sat Jan 16, 2010 12:20 pm

Well if you really want to do it fast, the pneumatic way, just fire a wedge into the wood.
Make sure everything is properly shielded and TAKE DISTANCE.
Do not go near the machine when there's pressure on it.
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