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How to use free software to design excenter levers for woodworking [not a build video] - Duration: 4:53.
Today we are going to design an excenter lever with free software.
Excenters have many uses in the shop such as for holding down a workpiece in place or
to glue up panels.
In my last video I created these adjustable floating shelves.
As I don't have an engineering background it took me some time to understand how to
best design an excenter lever.
In this video I want to share these learnings.
Let's first have a look at the basics how an excenter works.
If we have a circle and just punch a hole in it the distance between the hole and the
border of the disk will stay constant as the disk turns.
We can move the hole a out of the center which creates a basic excenter.
If we roll this one the distance to the border is increasing till the middle and is decreasing
afterwards.
We only use half of the contour this way to increase the pressure.
To improve the usage and effectiveness we would have to add more material on the second
half of the circle.
This is what's called a spiral excenter.
I tried to design it in CAD but actually didn't succeed.
The solution I ended up with was to use Inkscape.
If you want to follow along and don't have it already installed on your computer go to
Inkscape.org and download the latest version of the software.
In the software we click on the spiral tool and draw a spiral.
In the upper part of the window you can change the size of the spiral - for me that's 100
times 100 millimeter.
We then change the Turns to 1.8 so that the spiral covers only a bit more than 1.5 turns.
This tool here is a measurement tool.
We first click on the center of the spiral and then drag the mouse to the outside at
the narrowest and the widest point of the spiral.The difference between these two values
equals the amount of pressure we can create with the excenter.
Here the width of the spiral ranges from 39 mm at the narrowest to 58,6 mm at the widest
point.
The difference between these two values is 19,6.
If we want to reduce the travel down to 8mm we divide 8 by 19,6 and put the resulting
0,41 in the divergence field of the spiral tool.
We can use the measurement tool to control the two distances.
As soon as we are done with the spiral we click on this icon in order to snap to the
center of the spiral.
We then create a circle.
This will be the center hole so we change it's size to fit our axle and move the center
of the circle to the center of the spiral.
Next draw a rectangle and use the circle icon to give it round corners.
This rectangle is so that we can turn the excenter easier and we position it at the
opening of the spiral.
With the rectangle still selected we hold down shift and select the spiral.
In the Path menu we select Union to combine the two shapes.
Depending on your size there might be some leftover parts from the interior part of the
spiral.
To delete these choose break apart in the Path menu and delete the leftovers.
Lastly we select the circle and the outer form and select Difference from the Path menu
to cut the circle from the center.
You can now either print the shape and cut it on a bandsaw or you import it in a CAD
program.
Besides the floating shelves I mentioned in the beginning excenter levers are pretty helpful
for example as panel clamps.
Do you have other ideas where to use them?
Let me know in the comments.
I will continue to experiment with excenters.
If you are interested in these and many other projects please subscribe.
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OER Bootcamp 3-2: OERs and Open Format, Open Source software - Duration: 5:37.
This video talks about the importance of the source file of your Open Educational Resource.
When you have an Open Educational Resource, it is made available under a Creative Commons
license that allows anyone to revise it and remix it.
The license is just what makes it legal.
For it to really be Open, you also have to make it practically feasible to edit the resource.
As a side note, this means that if you create content in some web tool that does not let
you download what you created, it can't be an Open Educational Resource.
When your Open Educational Resource is a simple document or image, sometimes the file that
is accessed by the user is the same as the file that is edited.
But for more complex media and interactive formats, the finished product is a different
kind of file than the one that is edited.
Or in the case of web sites, the HTML might be readily accessible, but the CSS is running
behind the scenes, and you need to have both to replicate the pages.
So whenever you have an Open Educational Resource, you need to provide the source file as well
as the finished product file.
That way your user can easily revise and remix it.
You shouldn't make them have to go look for it, or ask for it.
Just put the file right there with the finished product on your web site.
Put a link to it in the repository, right alongside the link to the finished product.
If you're in YouTube or another content hosting site, consider putting a link to it in the
item information.
That leads to the next topic: your source file needs to be an open format.
Incidentally, these videos don't follow that rule.
I don't currently have the tools necessary to make screencast videos with open format
source files.
I hope to change that soon.
So what does Open Format mean?
Well to start with, when you use a software application, it creates files to store your
work.
Open format files are not locked down, and the information is out there for anyone to
build an application that will edit them.
Closed format files are locked down and the documentation is not available, so that you
are forced to buy a certain product from a certain company in order to edit the files.
It's a business model thing.
The problem with closed, or proprietary formats is that you have to have that particular software
application.
Otherwise, you can't edit the source file, which means you can't revise or remix an Open
Educational Resource.
No updating, no changing the format, no translating, no making excerpts, nothing.
And there are several reasons why you might not be able to obtain that software.
It might be too expensive.
Or it might not be legally available in your country.
It might not work on the devices or operating systems you have.
The company who made it might have gone out of business.
Or the company who made it might have simply moved on and abandoned the product, and now
it no longer works on modern devices or operating systems.
Common file formats that are open are PDF, MP3, JPG, PNG, GIF, and HTML.
But the full list is way too long to read out loud, and keeps changing anyway.
You can Google "wikipedia" "list of open formats" for a continually updated list.
Next I'm going to talk about Open Source Software, which related to Open File Formats.
Open Source Software is made available under a GNU Public License, which is the software
equivalent of the Creative Commons.
You can get a copy of Open Source software for free, and what's more important is that
programmers can get the source code and documentation so that they can modify and update it.
Open Source software can be freely reverse engineered to run on new platforms and operating
systems, to open new kinds of files, and to work in new ways.
It is not necessary to use Open Source software to create Open Educational Resources.
Open Source Software always produces files that are Open Format, and proprietary software
SOMETIMES does.
And the thing that really matters is that you're using Open Format files.
But it is good to support the Open Source Software movement because of the issue of
longterm access to your content.
Imagine you've created an Open Educational Resource that's so good that even 200 years
from now, people want to use it.
But you created it using Powerpoint and the file is pptx.
Microsoft hasn't existed for a long time, and Powerpoint won't work on any 23rd century
devices or operating systems.
But imagine you instead created your slideshow in the Open Source tool LibreOffice Impress,
and saved it in an open format.
Some 23rd century person could go back and find a copy of LibreOffice Impress source
code and documentation.
They can modify it to run on contemporary computers and operating systems, and that
way they can access and update your 200 year old file.
Open Source software is free to obtain, although sometimes you can pay for tech support.
Some of the tools are very attractive and full-featured, while others are more bare
bones.
Often you will have the option to try out features that are still in testing.
So some of the tools are the best of their class, like Audacity for sound editing.
Others are quite good but not as fancy as the commercial products, like LibreOffice.
Others are incredible tools but kind of hard to learn, like GIMP.
I maintain a list of high quality Open Source tools for you to try out at the OER Authoring
Tools tab of Empire State College's OER Guide.
You can get to it by Googling "empire state college" "oer authoring tools."
Remember, you don't have to use Open Source software as long as you're producing open
file formats.
But they are still valuable tools and they have a sustainability advantage.
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