Happy New Year (Merry Christmas too)

I have not posted here in a couple of weeks because I have been really busy with the holidays and working. Those two things have prevented me from doing any experiments, projects or writing new posts. This weekend is of course New Years and Last weekend Christmas so I just want to say Happy To You for both those events. I'll have something new next week, so check back then!

Meanwhile you can always read about some of the other things that I have built by clicking HERE. Enjoy!

 - Otto

GD&T Concentricity, Is It Round?

I want to write about several simple Geometric Dimensioning concepts that I have seen misused, misunderstood and misapplied over the years. It all boils down to things that are supposed to be round. Concentricity, Roundness, Cylindricity, Axis as a Datum and the list goes on and on... Is it round? I think that a lot of folks get these concepts wrong because "round" seems so simple on the surface but when you get into the details it's not that straight forward... or is it? Actually it is pretty simple if you slow down and think about it. The first idea is: Where is the axis of something that is round? Take a look at the picture below and let me know if this makes sense.

 

A Right and Wrong way To Establish A Datum
(Click on the image for a bigger view!)

     

In the top of the picture there is Datum A that is placed incorrectly on the axis of the part. I have seen this done so many times and it makes no sense! In the lower picture the datum is placed on a diameter. Why is it wrong to place the Datum on the axis? In the real world there is no ONE center axis of any part with multiple diameters and there is no 'Datum Axis' in this case. Which axis is the datum? In the lower part of the picture above it is clear which axis is the Datum because the Datum is on a round surface. That surface is creating the Datum axis. Because there are several surfaces on this part there is no way to know which axis is the datum in the top picture. Have a look at the picture below to see what I mean.

Eucalyptus Walking Stick With Epoxy

I spent a lot of time this week doing things other than working on my projects so I'm going to write a brief post about a walking stick that I made not too long ago. This is a stick that my son and I found while walking around a creek near our house. There are a lot of eucalyptus trees in the area and also a lot of sticks naturally. This stick is about an inch in diameter (more or less) and about 4 feet long. The end that eventually became the handle was "crackled" and dark as if it had been used as a poker in a fire.

   

My son and I thought that it looked neat and we walked around with it all day. Since there are so many sticks around the creek area there we figured that taking one home wouldn't be a problem. Once we got it home we sanded it smooth and got all the loose bark off of it.

   

Walking Stick With Epoxy Back Fill

Once we got all the loose stuff off with rough sanding and a stiff wire brush we did a bit more smooth sanding with #200 grit sandpaper. There are a lot of neat little crackled features (and a few big cracks) in the stick that made it a bit rough ever after the sanding. To fill those in we mixed up some grey two part epoxy and smeared it all over the wood, working it into the cracks and leaving it as smooth as we could leave it with gloved hands.

    

Click the jump below to read a little bit more and for a close up picture of the handle end of the stick.

     

Homemade Lab Jack (Part 2)

I have almost finished the Lab Jack that I started recently, actually it is done and it works! I wrote a PART 1 post about his project and I recommend that you read it if you are interested in how this got going and why I built it. I decided to build this after I looked around for commercially available products and decided that they were too expensive or not big enough for what I wanted. Besides, if you build it yourself it is exactly what you want! Below is a picture of the completed lab jack extended to over 12 inches in height.

     

My Home Built Lab Jack

Can it go higher than twelve inches? Yes it can but it gets really unstable due to the 'play' in the hinges. I'm going to fix that and I'll write a post about how I fixed it soon. This project worked out better than I expected. It's very easy to raise the height by turning the adjustment knob (detailed below) from the lowest height of 2-1/4" all the way up to where you see it in the picture. The only problem is in the 'slop' in the hinges that I used to make it. Being the first Lab Jack that I have built I have to call this a success.

   

Check out THIS LINK to see some of the other stuff I have built.