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+--- Thread: Wedge of wood splitting machine (/showthread.php?tid=129)
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Wedge of wood splitting machine - Jan - 07-05-2017
Recently I have spent some time in the Alps and have had opportunity to observe the house lord by splitting fire wood.
[attachment=257]
I was surprised how sharp the splitting wedge was. I did not have my PT50B with me, so I can only guess that it was not to much more than 2000 gf.
The other thing that surprised me was the acute angle of the wedge, some 35°. It is the same edge angle we are sharpening on the majority of our knives.
Narrow edge angle guaranties large mechanical advantage of the wedge, but on other hand friction may bind narrow wedge more easily than a wide one.
[attachment=258]
RE: Wedge of wood splitting machine - Ken S - 07-05-2017
Jan,
You have that curiosity so important to growth. No matter how technological we become, we are always never far from the "simple machines" we studied in elementary school. As a telephone man, I often wished I could have school children use my block and tackle in placing a wire between rural poles 100 meters apart.
Wedges are so useful. (They even work in flat lands. :
) Thanks for sharing your post.Ken
RE: Wedge of wood splitting machine - Jan - 07-05-2017
Ken, I appreciate your response. I think that in psychology our attitude is called "professional deformation", which means that our former professional training resulted in a distortion of the way we view the world.
Jan
RE: Wedge of wood splitting machine - EOU - 07-05-2017
Ken I think possibly that the device you used to tension telephone wires is what we used to stretch barb wire on the farm during the fence building process. The same device also had at least one secondary use. Delivering calves that were reluctant or unable to be born as nature intended. In those days "calling the vet" meant locating your dad and maybe a neighbor or two. Men were men and cows were cows in those days.
RE: Wedge of wood splitting machine - grepper - 07-05-2017
Mr. Jan sayeth, "Narrow edge angle guaranties large mechanical advantage of the wedge, but on other hand friction may bind narrow wedge more easily than a wide one."
Isn't that the whole purpose of a fat wedge?... To get those skinny wedges unstuck?
RE: Wedge of wood splitting machine - Jan - 07-06-2017
Yes, Mr. Grepper. Wedge is a simple machine which converts the force applied to the blunt end into perpendicular forces. Friction a little bit complicates the situation.
In some situations, e.g. when lifting a heavy body, we use long wedge with narrow angle. In this case the friction binds the wedge.
When splitting wood, we are not interested in stacking wedge and therefore we use a shorter wedge with a wider angle. We sacrifice some wedge mechanical advantage in favour of increased splitting efficiency.
RE: Wedge of wood splitting machine - grepper - 07-06-2017
Mr. Jan, I notice you say "2000 gf". Is "gf" gram force? Is that the proper way to represent BESS sharpness readings? Not knowing exactly how to represent it I've just been using "g" for gram like "2000 g". I've been wondering what is the proper way to represent sharpness readings.
RE: Wedge of wood splitting machine - Ken S - 07-06-2017
What fascinates me with simple machines is how adaptable they can be. My telephone block and tackle had double pulleys on each end. That was a good balance for our work. If two more pulleys were added to each side, much more rope would be required for the same amount of movement, however, the amount of weight which can be moved increases incredibly.
We can choose the bevel angle which suits our needs, in both wedges and in knives. That's part of the allure of sharpening over the ages.
Ken
RE: Wedge of wood splitting machine - Jan - 07-07-2017
(07-06-2017, 07:47 PM)grepper Wrote: Mr. Jan, I notice you say "2000 gf". Is "gf" gram force? Is that the proper way to represent BESS sharpness readings? Not knowing exactly how to represent it I've just been using "g" for gram like "2000 g". I've been wondering what is the proper way to represent sharpness readings.
Yes Mr. Grepper! "gf" – gram-force, is a non-standard gravitational unit of force, which does not comply with the SI Metric System used outside the US.
The SI unit of force is newton (N). The conversion factor is following:
1 gf = 0.00981 N.
The figure 9.81 m/s2 is average gravity acceleration on the Earth surface.
So, the BESS sharpness 2000 gf = 19.62 N. Roughly we can say that 2000 gf ≈ 20 N.
In my understanding the gram-force unit is the proper way to represent BESS readings within the US, for the rest of the world the conversion to newton should be stated in brackets.
P.S.: In UK "engineering" systems pound-force unit ("lbf") can be used.
RE: Wedge of wood splitting machine - Jan - 07-07-2017
(07-06-2017, 09:16 PM)Ken S Wrote: What fascinates me with simple machines is how adaptable they can be. My telephone block and tackle had double pulleys on each end. That was a good balance for our work. If two more pulleys were added to each side, much more rope would be required for the same amount of movement, however, the amount of weight which can be moved increases incredibly.
We can choose the bevel angle which suits our needs, in both wedges and in knives. That's part of the allure of sharpening over the ages.
Yes, Ken, you are correct! They are only six classical simple machines which use leverage to multiply force or change its direction.
[attachment=259]
Ignoring friction losses, the work done on the load is equal to the work done by the applied force.