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.

Homemade Lab Jack (Part 1)

This is a rather ambitious project and by ambitious I mean it might not work. On many occasions I have needed to adjust the height of something, usually a camera, in very fine increments. A tripod works really good for that and I have one... but a lab jack would be much better so I decided to build one. Also a lab jack is a nice thing to have!

      

There are three industry standard approaches to designing a lab jack. One is THIS where there is a scissor lift that has to slide in a track relative to the platforms. One disadvantage is that it becomes less stable as the height grows. Another design is the Dual Pantograph like THIS that is a bit more stable but requires a lot more linkage's. A much more stable design uses three linkage hinge's in THIS type of configuration. With this one there are two opposing linkages and a third to add stability. This last configuration is what I decided to build.

   

Homemade Lab Jack

The above picture shows how much progress I have made at this point. Not much! You can see the opposing hinge systems and the location of where the third will be. The wood that I am using is Baltic Birch plywood, the same wood that I used in my clock. There is a 1/4-20 all thread bolt running through the hinges and that was the tricky part of this project.

Wind Tunnel Smoke Generator

A couple of weeks ago I wrote about the details of my home made wind tunnel and I wanted to add some recent modifications I made to the smoke generator system. The smoke generator that I am using is a Halloween fog generator and I modified it by attaching a hose to the outlet (and rewired it!). There are some details about that in THIS post. I had a problem with that setup because the smoke (or fog if you want to call it that) coming out of the generator was hot and it melted the plastic tubing that I had attached to the generator. Check out the post above that I linked to for details. A second problem was that the smoke was being blasted right through the wind tunnel in bursts. I only had a few seconds to make an observation with smoke! Another problem that I had was the liquid that is used to make the fog was condensing in the tube that I attached to the output and that condensed liquid was filling the tube and creating back pressure. The tube was essentially being blocked by the condensed liquid, getting hot and finally burst. I decided that I wasn't going to run this smoke system any longer without addressing those issues (and cleaning up my garage).

  

Smoke Generator Accumulator Tank

What I came up with is shown in the picture above. I got a 3 gallon plastic paint bucket and attached a couple of barb fittings to the lid. On one of the barb fittings I ran some 3/8" fuel line hose from the smoke generator and on the other fitting the plastic hose feeds the wind tunnel. You can see the wind tunnel in the lower right corner of the above picture.

Electric Bike Design

I wrote a post HERE in September about a electric bike that I designed, the E-Moto Monterey Electric Bike. There were a couple of pictures from the Las Vegas Interbike trade show that looked nice but didn't really highlight the unique features that this bike has. Below are some better shots of the finished product and some comparisons to the original CAD design that I did using SolidWorks.

   

Monterey Electric Bike (real photo!)

 

Monterey Electric Bike (CAD Model)

You can see some differences if you look really close between the CAD model design and the finished product. In case you can't see the differences I have more closeup pictures below!

Wind Tunnel Details

I was sick with the flu this week so I didn't get very much done. I really wanted to do some more experiments with the Plasma Actuator that I wrote about a couple of weeks ago HERE but due to the illness and the cold spell we have had recently I stayed out of the garage. Because of several emails that I have received asking about the wind tunnel, I decided to write a little about the wind tunnel that I built and used for those tests. HERE is the original post that I wrote about building the wind tunnel that has most of the construction details. Below is a picture of the results that I got with the tunnel.

 

Airfoil Plasma Actuator in my Wind Tunnel

In order to see the airflow I added smoke (fog) to the airstream using a Gemmy Fog Machine. HERE is a link to their website for the model that I picked up at WalMart for about $25.00. The Fog Machine heats up and sprays a mist of glycol and water for about 60 seconds into a heating tube and the result is fog. As the mist is sprayed into the heating tube the tube cools down and the machine stops spraying until the tube can heat up again. I didn't like that so I took the Fog Machine apart and modified it so that it produces fog when I press the button and stops when I release the button. It's always fun to take apart brand new stuff!

GD&T: Multiple Datum's Referenced, More Than One Datum?

Datums referenced on a drawing using Geometric Dimensioning and Tolerancing can be really confusing, even on simple parts! When you get right down to it Datums are not that difficult to understand when you consider what they are used for. I have received several questions about Datums, why and how they are used and why use more than one. I'm going to answer those questions using a simple part that has one hole and has three Datums referenced. But before I go into the explanation about multiple Datums I recommend that you read THIS post I wrote about a parts size and how the dimensions tolerances determine what a part can actually look like. For a quick review there are THESE posts that I wrote about Geometric Dimensioning and Tolerancing Basic concepts. This post is a quick overview of the basic concepts of using multiple Datums. There is a lot more to Datums than what I'm writing about here and I'll get into those more complicated concepts later!

     

Lets start with a simple drawing of a part that has one hole in it and the hole is positioned in relation to three Datums.

 

Simple Part with Multiple Datums

The drawing above has a hole in it that is True Position to three Datums in this order: A B C. The reference to Datum A is holding the location and orientation of the center axis of the hole to Datum A (bottom surface). Take a look at THIS picture from an old post if that doesn't make sense. Another way to look at this is Datum A is the surface that someone is going to measure the perpendicularity of the hole to. So Datum A in this case is a place to start taking measurements. We'll start taking measurements with Datum A because it's the first Datum and we will continue measuring the part with the remaining two Datums in order from left to right. The Datums don't have to go in alphabetical order, they are in used in the order that you reference them when you measure the part. The important thing to remember is Datums are used to measure a part.

   

So what are the other two Datums doing? I'll explain the below... ;-)

Plasma Actuator Airfoil Wind Tunnel Testing

This week I built a Plasma Actuator in the shape of a crude airfoil and tested it in my Homemade Wind Tunnel. Plasma Actuators are research devices that use an electric field to change the characteristics of gas flow near a surface. In this experiment I was trying to get the airflow over the top of the airfoil (wing) to adhere to the surface of the airfoil when it normally wouldn't. Separation of the airflow over the top of a wing causes the lift generated by the wing to be reduced resulting in a stall. Before I talk more about what I built let me put a couple of pictures that I took from my experiment to help explain what I'm writing about.

   

Airfoil in Wind Tunnel Plasma Actuator Off

   

Airfoil in Wind Tunnel Plasma Actuator On

   

The above pictures were taken one after the other with the same airflow, the only difference between the two is in the lower picture the Plasma Actuator is turned on. In the lower picture the flow over the top of the wing is much smoother than in the top picture and is adhering to the top of the wing. Read more below for some details about the Plasma Actuator that I built and a video of it running.

Geometric Dimensioning and Tolerancing: Position, Zero Tolerance and Material Condition

I have written a few posts about Geometric Dimensioning and Tolerancing (GD&T) basics and I want to write another one about a topic that is probably the most often question asked of me: Zero Tolerance dimensions. The name Zero Tolerance is confusing to some folks because as we all know "every dimension must have a tolerance" so what is a Zero Tolerance dimension? Does that mean that the part has to be perfect? Why would anyone put a Zero Tolerance on a drawing? I'm going to try and answer those questions in simple steps starting with a quick review of Material Conditions because you can't have a Zero Tolerance on a drawing without specifying a Material Condition. If you haven't read my other posts about Geometric Dimensioning and Tolerancing I suggest that you do by clicking HERE and reading the posts related to GD&T. At a minimum read the posts about Material Condition and True Position. One thing I want to mention is my intent here is to explain the concepts in simple terms and avoid all the esoteric 'advanced concepts' that you will find in other places on the net. I get questions from friends and colleagues who are not familiar with GD&T and I try to answer those questions as simply as I can. Once someone understands the basics the more complex concepts are easier to get. If you are not familiar with a Zero Tolerance here is a drawing that is using it.

Drawing With Zero Tolerance

Before I start talking about Zero Tolerances I want to talk briefly about Material Condition because the concept of material condition is key in understanding Zero Tolerances. I'm going to go fast so if you want a better and more detailed explanation of Material Conditions read THIS post that I did awhile ago. Here we go! The Material Condition concept is a fancy way to think about how big or small a particular Feature of a part is. There are three material conditions and two types of Features. The three Material Conditions are: Maximum Material Condition or MMC, Least Material Condition or LMC and Regardless of Feature Size or RFS. The two types of Features are: Internal (like a hole) and External (like a block). When considering Zero Tolerances the only Material Conditions that are important and MMC and LMC so I'll skip RFS here.

San Francisco Fleet Week

I like airplanes, ships and standing in long lines fun day trips and I got my fill this weekend. So I went to the 2011 San Francisco Fleet Week on Saturday. It was a lot of fun and I took a bunch of pictures, I'm going to put a few of the good ones here. The USS Carl Vinson (CVN-70) and the USS Bonhomme Richard (LHD-6) were two of the most notable ships there as well as the Blue Angles and many other aircraft. There are tons of pictures, news articles and info. about San Francisco Fleet week on line so I'm not going to put a lot of that here. If you want to know more about SF Fleet Week Google it. Because this Blog is about the things that I am doing I'll stick to what I did. BTW: I am still working on the wind tunnel that I wrote about last week but I don't have a lot of progress to write about.

      

To get to San Francisco we took the East Bay Ferry from Oakland to San Francisco. This is the way to go to avoid traffic and standing on BART. We left Oakland and went straight to San Francisco. On the return trip I took the picture below of a crane on the Alameda waterfront. I thought it looked neat with the moon right off the end of the crane boom.

Alameda Pier Crane

Old mechanical stuff like that looks neat and I really like the picture so I put this one first. It's rusted and looks like it's about to fall over but it appears to be in service. The Ferry leaves from the post of Oakland and I have only one interesting picture of the ship that is right next to the ferry.

Homemade Wind Tunnel for Plasma Actuator Testing

I finally got around to putting the wind tunnel together, well actually it's a breeze tunnel. There isn't much of a wind blowing through it! After looking at the performance of the Bladeless Fan I built I decided that it was going to  create a higher airflow than I need for the Plasma Actuator experiments that I want to do, so I decided to slow it down a bit and use a small DC fan. The DC fan is easier to use because I can control the speed of the air with a variable power supply and the airflow from the Bladeless fan just dropped off all together when I lowered the input air. This wind tunnel is only to do some experiments with the Schlieren setup I built and High Voltage and a low velocity and variable airflow is what I need. Before I built this wind tunnel I did a lot of reading on line and found some plans from a NASA wind tunnel site describing a small classroom wind tunnel for students to build as well as a lot of very technical information about "real" wind tunnel design. As I mentioned above my wind tunnel is more of a breeze tunnel so I didn't need a lot of the flow control, settling areas and velocity constrictions. I just need something to provide a smooth flow of air past a viewing area. Below is what I came up with.

Homemade "Suck Down" Wind Tunnel

In the picture above the airflow is right to left, the fan is on the left, the view area is in the middle where the glass windows are and the inlet air goes into the right side. Because the fan is downstream of the test area this is considered to be a "suck down" tunnel. One advantage of a "suck down" tunnel is the turbulence and chopped up air created by the fan isn't blowing over the test area. Smooth air is sucked past the viewing area. Click below to read more!

Interbike 2011 Bike Show and the E-Moto Monterrey Bike that I designed

The Las Vegas Interbike trade show happened on September 14-16 at the Sands Expo and Convention center. One of the (best) electric bikes shown there was the e-Moto Monterey electric bike that I co-designed in SolidWorks with a friend of mine. Although I wasn't able to go to the show I thought that I would write a blog post about the bike since I had a hand in creating it. Have a look at the pictures below of the Interbike show bike and the CAD model that I made to design the bike.

    

e-Moto Monterrey at the Interbike 2011 show
      

SolidWorks CAD model of the e-Moto Monterey bike

Details of the bike and all it's features are below. I did the entire design in SolidWorks 2009. A friend of mine who is familiar with the bike industry and trends was advising and critiquing along the way.

    

Bladeless fan construction

Yes I am building a wind tunnel... and the biggest problem in doing so is getting rid of turbulence from the air source, in this case a fan. So to do that I am building a fan (air source) that should have a limited amount of disturbed air. What I want is a smooth airflow into the test area and a bladeless fan seems to be the obvious choice..

      

I built a fan like this before HERE but didn't provide too many details of the construction. This time I built a slightly bigger fan and have provided all the details in a neat video.

   

Enjoy!

      

        

Email me with questions or leave a comment... There is a lot more to come on this topic so stay tuned...

Latest project, wind tunnel and a plasma actuator

I'm building a wind tunnel in my garage. Doesn't that sound neat? My interest in this is probably obvious because of several posts that I have dome thus far related to Plasma Actuators. The experiments that I was doing with my homemade Schlieren setup and specifically the high voltage experiments HERE and HERE among others.

   

The idea is to build a wind tunnel and place a plasma actuator inside it and watch what happens as the air is passing over the actuator. Comparing it in the 'on' and 'off ' states and various voltages. The wind tunnel has two windows so I can put the Schlieren setup on each side. Additionally I want to use a smoke generator and lasers to visualize the airflow. Check out THIS video to see what I mean about the lasers and smoke.

   

What does all this mean? I ask myself that question frequently, hourly sometimes but the answer is "I don't know!" That is why I am taking the time to build this setup and because it's a rather complicated project I don't have any neat pictures and videos to post yet but stay tuned they are on their way. The wind tunnel by itself is a significant amount of work and of course the plasma actuators are too. A lot of work and the devil is in the details so I'm paying attention to them (more or less).

    

After having read everything that I can about both wind tunnels and plasma actuators I have some specific things that I want to try. I'll detail each of those in the next week or two and post some neat pictures and videos.

    

    

My New Phone a Samsung Replenish

This week has been busy for me and I haven't had a lot of time to play in the garage. One thing that I did manage to do was get a new phone, a Samsung Replenish and mess around with it and the Google App Inventor for Android. My old phone was a Palm and I loved it but it was really old and time to retire it to the box of phones and chargers that I have in the closet. I'm new to the Smart Phone craze and having a phone that is smarter than I am is a new experience for me. Should we really even call these things phones? It's interesting that it is called a phone but when you start to type a phone number it immediately does a web search for the number and not dial the person who you are trying to call. I think this is more like a hand held computer that also makes phone calls.

 

My Samsung Replenish

My first impression of the phone was how tricky the touch screen is to operate. As I mentioned I'm new to this but having to 'flick' my finger on the screen to move around isn't easy. I find myself selecting things rather than moving them especially when the screen is listing a bunch of options. I want to scroll down to see more options but instead I select one of them while trying to move. I'm getting better at it but it isn't intuitive and requires a lot of practice. The good think about the Replenish is there are arrow keys on the keyboard that let you move around without having to touch the screen. I can't imaging having to operate the phone without a keyboard.

Homemade Wood Clock Test Run

This is going to be a short post... well maybe not. As I start to write this it's Sunday, it's late and I am tired! What I wanted to put up was the test video of the clock running. Anyone following my blog knows about the wood clock that I am making and if not you can check out the earlier posts in the Woodworking Label.  Without further adieu here it is - enjoy!

     

     

There are a couple of things that I would like to point out about what is going on in the video. The first thing is again this is a test. The clock motor is running a lot faster than it normally does to keep time. The second thing that I think I should point out it the hour hand. If you look really closely at it you might notice that it is a wood "q-tip" with a pointed cotton end! That is because I didn't have time today to make a hour hand so I stuck that on there in it's place. The more I look at it the more I think I will keep it actually.

More Progress on the Homemade Clock

This was another busy week for me and I didn't get as much done on the clock as I would have liked to but... I did get some things done. In case you are not familiar with what I am doing you can read these posts HERE and HERE and HERE to get an idea. The short description is that I am making a clock that has a stationary hour hand pointing straight up. The face of the clock turns counterclockwise to line the correct and current time up with the hour hand and the minute hand rotates clockwise to indicate the minutes. HERE is a video that I made of the CAD model for this clock running and it shows pretty much how it's going to work. Seems simple enough!

   

What I got done this week is I made the small discs that the numbers will be attached to by cutting slices of 1-1/4" oak dowel. Obviously I made 12 good ones and a bunch of bad ones that were either too thick or too thin. You can see there in the blue tote bin in the picture below. You can also see in the picture that each disc has a Woodruff key glued to it. The idea is the the Woodruff key will add some weight and keep the numbers on the face of the clock upright because the discs will be allowed to spin relative to the clock face.

   

Clock Parts, Oak discs with Woodruff keys glued to them

Also in the above picture right below the blue tote is a gearbox and a motor. It's to the left of the wood gear on the back plate for the clock. That is another Tamiya gearbox that I got and used in another clock that I built some time ago. Check out THIS post for details of the gearbox. I picked up several of these gearboxes at a hobby shop that was going out of business so I got them at half price and figured that I would use them at some point. You can never have enough gearboxes I always say!

Significant and/or Insignificant Part Number Systems?

Part Numbers can be funny and frustrating things when really they should be inconsequential. Over many years of working as an employee or a consultant to various companies in many different industries I have been amazed at the Part Number 'systems' that companies have tried to use. Part Numbers within a company are used to assign a unique 'identity' to different items tracked within the company. HERE is a Wikipedia talking about Part Numbers if you want to know more about what they are generally. The reason that I am bringing this up is because I have seen P/N's become a source of money wasting time and confusion and I want to put my opinion out there with some examples of what I have seen. I am only going to address the topic of Part Numbers in this post and not the Descriptions. Part Descriptions is an entire topic all by itself.

    

Significant vs. Insignificant Part Numbers

The first schism in the Part Number philosophy/religion debate is over how P/N's should be assigned to things. Some folks believe that a Part Number should have some unique significance built into it - or intelligence -  to describe what the thing is that has the Part Number. In other words by looking at the P/N one should be able to have an idea of what the item is. In this case the P/N really becomes the description of the particular part (or assembly) and usually each digit in the Part Number has a particular meaning. On the other side of the battle field is the army of people that say that a Part Number should just be a number, any number, that is just unique to an item and doesn't tell you anything about what the part is. These two approaches are usually referred to as Significant Part Numbers and Insignificant Part Numbers. Part Numbers are assigned to things as unique identifiers for tracking purposes and referencing records etc... The only stipulation when giving something a part number is that it be unique and never reused.

      

Insignificant Part Number Systems

Everything has a name and a number associated with it within a company, even the employees. Have you ever cared what the employee number is of a co-worker? Probably not, you are more likely to care about their name. The same logic follows when talking about part numbers in an Insignificant Part Numbering System. The number a particular part has isn't important in an Insignificant Part numbering system, but the description (or name) is.  That's the thinking with non significant part numbers.

Gear Runout and my Wood Clock

I am still working on the clock movement (or gear train) for my wood clock that I wrote about a couple of weeks ago and the gear runout is a slight problem. This isn't turning out to be one of those projects that I can just "cut and glue" and be finished, it's requiring a lot of adjustments and finesse. Getting the hole in the center of the gear (or runout) has turned out to be a little more trouble than I thought... So I used a dial indicator and a couple of C-Clamps to check and adjust the runout by drilling an undersized hole for the shaft then filing it appropriately until the gears turned without much indicator movement. If you have not read the previous posts about the clock HERE and HERE are the first two. Check them out so you can see what I am trying to build.

Checking Gear Runout on a Clock Gear

In the above picture you can see what I am talking about. On the right hand side of the picture there is a dial indicator sitting on a base that is C-Clamped to the bench. To the left is a piece of scrap wood with a hole in it that the brass tube fits snugly in. So with this setup I can spin the gear and place the dial indicator tip on the gear tooth crests and valleys to see how centered the hole is relative to the gear teeth, that's runout.

     

In order to get the the point where I could check the gear with the 'real' brass tube shaft the I am going to use in the clock I had to get the hole made to the right size and in the right place. To do that I started out by drilling a small hole in what should be the center of the gear and I put a straight finishing nail in it. The scrap wood under the gear in the picture above has a hole in it that the finishing nail fits snugly into and with that I could initially check the runout by spinning the gear on the finishing nail. Out of all the gears I made all except one had the finishing nail hole a bit off center, by about 0.03". To remedy that I drilled another hole again, slightly undersized to the brass tube shaft, and compensated for the runout that I saw with the finishing nail hole. By compensated I mean that I moved the drill off the finishing nail hole just a bit. This hole is also undersized a bit from what the final hole will be and I have a shaft that will fit in this undersized hole just like the finishing nails did. Again I can check the runout of the gear with this slightly smaller hole and a slightly smaller shaft and if my "compensation" drilling isn't quite right I can make up for it by enlarging this hole to the final size with a small rat-tail file.

Another Battery Powered LED Light Tree

I was in a store in Monterrey CA that sells these really nice 'light trees' last year and I thought that it would be fun to try and make one myself. The first one I made one from scratch, buying all the parts at a hobby store along with LED Christmas Lights, and I wrote about it HERE, (an exciting video of how I made it is HERE). Anyway I was asked to make another LED Light Tree because the first one that I made turned out really nice ;-) When I went to the hobby store again to buy the parts I noticed that they are now selling LED Branch Lights pre-made! This is great because the majority of the effort in making the first LED Branch Light was making the branch itself with all the LED Christmas lights added into it. Check out the above link to see how I did it (or watch the video). I didn't have to do that this time but there were some other interesting things that I discovered while making this one with the pre-made LED branch.

 

Homemade LED Branch Light Tree

 

Above is a picture of how this LED Light tree turned out. Looks nice doesn't it? Click on the READ MORE link below to see the parts list and how I built this as well as something interesting I noticed in the battery pack for the LED Branch Light.

  

Homemade Wood Clock Construction

Last week I wrote about a homemade wood clock that I was designing in Solidworks. If you are curious there is a link to that post HERE, there are details about how it is going to work. If you don't want to read that post, the homemade wood clock design is as follows: I decided to make a clock that has an hour hand that stays upright, pointing straight up all the time and the face of the clock moves to tell the hour. Because the face is moving to meet the hour hand (instead of the other way around) the minute hand has to turn at a different ratio than in a 'normal' clock. To get that to work I designed a wood gear clock movement (gearbox) that has a 11:1 ratio with the face of the clock turning counterclockwise and the minute hand turning clockwise. Although I didn't make as much progress on this wood clock project as I wanted, I did manage to get some work done. I got all the gears done, the 'spindle bearing' figured out and the support structure made. Be sure to have a look at that last post I linked to above to see what I am trying to do.

 

Wood, Gears, Glue and Tools for the Clock

There are a few things that I got worked out in the design since last week and a couple of problems solved. One issue: I have never cut gears from wood before so this was a bit of a learning experience for me. To make the gear patterns I used an online Gear Template Generator from a site that I link to in the "Sites I Like" bar in the sidebar of my blog. Cutting the gear teeth started with printing out the gear pattern from the online generator above and gluing the template to Baltic Burch plywood. The Baltic Birch has a tight grain and the layers in the plywood are very thin making is good stable wood to work with. After getting the pattern on the wood I rough cut the gear out with a band saw then finished the teeth with a scroll saw and sanding. Getting the hole right in the middle of the gear was a challenge but I managed to do it. If anyone has any advice about making gears from wood I would like to hear it!

Homemade Wood Clock Design

Awhile ago I was looking at Roman numeral clocks and wondering why there is no standard way of putting the numbers on the face, specifically the number IV being 'upside down' on some clocks and not on others. I wrote about that HERE and since then have been thinking about making my own clock. Well now that I have had some time to think about it I have decided to go ahead and make a wood clock. This post is the first in what I expect to be several detailing how my wood clock design project goes. I have never built a wood clock and have never made gears from wood so this whole project is an experiment and learning experience for me (and my young son). Designing the clock movement and the gears from wood seems like a fun project!

   

Because of the Roman numeral clocks that I have seen with the IV sometimes upside down I thought that it would be neat if all the numbers were right side up. Having all the numbers right side up isn't too interesting but I also was thinking that the hour hand should always be pointing up too. After all the hour is probably the most important thing that you want to know first. So to have the hour hand always pointing up and all the numbers always right side up, would mean that the face of the clock would have to turn and all the numbers would as well. The minute hand of course would be rotating around but because the clock face is rotating too the ratio of the hand to the face would be different that a conventional clock. To get all this to work I decided to do a CAD model in SolidWorks of the clock movement (see 'click here to read more' link below) and do some research on making gears out of wood. While doing some web surfing research I ran across a really neat Woodworking for engineers site that I have linked to in the "sites I like" where I found a neat on line tool for generating gear templates. Below is a picture of a couple of the first gears that I made for my clock using the on line generator. they came out nice and seem to spin pretty well. It didn't take too long to cut them either roughing them out on a band saw and finishing the teeth with the jig saw. 

 

My First Attempt at Wood Gears for My Clock

I have designed several gear trains professionally but never for a clock and never from wood. As it turns out (no pun intended) getting the hands to move at the right speed and in the right direction is an interesting design problem. To figure all this out I did a CAD model in SolidWorks to make sure that the gear ratio was going to be correct, the minute hand and the face were turning at the right gear ratio and in the right direction. I also wanted to see how the whole thing was going to look at different hours of the day. Have a look below at the design and a short video that I made of the clock running.

Conditional Formatting in Excel and Prime Numbers

Numbers are cool and fun to play with in my opinion, especially Prime Numbers. I wrote about this some time ago in a post HERE and I've had some ideas since then. In that post I was using a Excel spread sheet with some Visual Basic code to create a number sequence then I was using another function to check if a number in a particular cell was prime. The function was scanning through a list of prime numbers in the spreadsheet and if it found a match the formatting for the cell that matches was changed to blue using Copy Formats in Excel 2007 instead of the Conditional Formatting idea. To do all that in Visual Basic for Excel was fun but overly complicated as pointed out to me by Codemann8. He commented on that last post and left a formula for Excel that can check to see if a number is prime! It's a cryptic and really cool formula that he didn't take credit for (it's out on the web) but it will check for prime numbers. I finally got around to trying this formula out and I used it to highlight prime numbers in a simple multiplication chart that uses modulo arithmetic. Below is what the Multiplication Modulo Chart looked like but I also want to show how to set this formula up to control Conditional Formatting in Excel 2007 because it took me awhile to get it to work.

   

Excel 2007 Conditional Formatting in Modulo Multiplication Table

   

The above picture shows what the spreadsheet ended up looking like. Along the top and down the left side are the numbers 1-257 (only 1-23 are shown) and in the middle are the products of those numbers - a multiplication chart. In the upper left corner in the highlighted cell is the modulus of multiplication. In other words the numbers in the top and left are being multiplied modulo 23 in this case. The blue cells are the prime numbers being highlighted by the formula below using the Conditional Formatting function. At the end of this post I made a short video that cycles the multiplication chart through various number sequences showing the various patterns the prime numbers make! Really Cool!!!

   

Below is the formula that Codemann8 left in a comment on another post I wrote and it checks to see if a number is prime returning the Excel TRUE condition if it is. If you 'Google' that formula you will get a bunch of pages that talk about it. Whoever came up with this formula had their thinking cap on!

=OR(A1=2,A1=3,ISNA(MATCH(TRUE,A1/ROW(INDIRECT("2:"&INT(SQRT(A1))))=INT(A1/ROW(INDIRECT("2:"&INT(SQRT(A1))))),0)))

Click below to read more about how to set up Conditional Formatting in Excel 2007 to use this formula and to see the boring exciting video I made of the spreadsheet cycling through various number sequences, highlighting the prime numbers as it goes!

    

Water Worries, Sprinkler Debugging and Water Traps

I thought that I would write this week about something that I have seen many times and fixed many times. Sprinkler Valve Wiring. Why is the wiring so complicated and always seems to be messed up? I don't think that this post will answer that question (or any others) but it is a good time to share my experiences with sprinkler valves and maybe something that is only related by virtue of the fact that is involves water (more about that below).

Some people reading this may know that I recently moved into a new home a few miles from where I had been living for several years. This new place is the first for me that in quite some time actually has a lawn and sprinklers to water it. After living here and settling in I decided to see what days the sprinklers were programmed to water and how much water I was paying for to keep the lawn fresh and green. To do this I of course started by checking the programming on the sprinkler controller and placing a low pan on the lawn to catch the water. The pan is to see how many inches of water is being delivered to the lawn per sprinkler cycle.

Bad Sprinkler Valve Wiring

So I turned on the sprinklers and waited for the pan to fill up with water. The lawn only has two 'zones' or valves so I thought this would be quick. The first valve opened and the sprinklers spränkled like they should, all the little droplets of water going everywhere you might expect them to. Then when it came time for zone two to turn on nothing happened. I looked at the valves and the wires a little closer and found what you see in the above picture. The duct tape was a nice touch but to find out what was wrong click on the read more below...

GD&T Basic(s) True Position and Tolerances

This post is a very simple explanation of Position as used in Geometric Dimensioning and Tolerancing. Why am I writing about Position? One of the most frequent questions people ask me regarding Geometric Dimensioning and Tolerancing is "what does that target bulls-eye symbol mean". That bulls-eye symbol is called Position and it seems to be the most confusing and mysterious symbols in GD&T for some people. Before I talk about Position you should go back and read - or read if you haven't read already - THIS post that I wrote about tolerances and size and maybe even THIS post I wrote awhile back. There is nothing really mysterious or even complicated about the concept of Position and how it's used with Basic Dimensions in GD&T. The application can get pretty scary and complicated sometimes but the concept is pretty straight forward. I'm going to try and explain it in a overly simple way and later tie all these Design Related posts together as I write more of them.

 

Square Tolerance Zones

The first thing that is important to point out is that Geometric Dimensioning and Tolerancing is all about the dimensions tolerances so I'm going to compare the 'traditional' method of tolerancing to Position as a starting point. So to start with have a look at a 'traditional' drawing below that uses linear coordinate dimensions. On a 'traditional' drawing that is using linear dimensions the tolerances are put on each of the dimensions either directly as in the picture below or in the title block (or notes) on the drawing. Have a look at the below drawings 2A and 2B that are dimensioned 'traditionally' with the tolerances on the dimensions themselves. I have left the dimensions of the block itself off the drawing for clarity.

Linear Dimensions with a Square Tolerance Zone

  

In the top view of the above picture (2A above) there is a rectangular block and a couple of dimensions to a point near the middle. Imagine that you want to drill a hole 1.5 inches from the left side and 1 inch from the top as the dimensions show. Note that each dimension has a tolerance of +/-.25 inches so to get the hole in the right spot you first measure down from the top of the block 1 inch +/- .25 inches, giving you a total tolerance of .50 inches. Same thing with the other dimension, measure from the left 1.50 inches +/-.25 inches - again giving you a total tolerance of .5 inches. To get the hole in the right spot according to the dimensions (and the tolerances) you would have to drill the hole so that the center of the hole was somewhere inside that .5 inch square tolerance zone. Does that make sense? It seems strange if you think about it that a round hole would be positioned in a square tolerance zone doesn't it? Read more and this will start to make sense...

GD&T: Maximum and Least Material Condition, Size Matters

Geometric Dimensioning and Tolerancing or GD&T is a subject that I get asked about frequently. As I wrote before in THIS post about Levels of Control I thought that I would Blog about the subject because I spend quite a lot of time answering friends a colleagues questions about it. Have a look at that post and read the fist couple of paragraphs if you are curious about what Geometric Dimensioning and Tolerancing is.

  

Size matters and size is what I want to write about in this post. After all having parts that are the right size is what allows them to fit together. What I am going to write about in this post might seem completely theoretical and somewhat pointless in the real world but it isn't. These concepts don't seem practical when you have a drill or a saw in your hand but actually this is all about having parts that you design and build fit together right? Fitting together of course is all about the size of the parts. Geometric Dimensioning and Tolerancing has some basic concepts about size that might seem a bit odd at first but it all makes sense when you think about how small a hole can be and how big a pin that has to fit in the hole might be - and then grab a hammer to force it into the hole.

  

The first point that I want to make is that all dimensions on drawings have to have a tolerance associated with them. All dimensions on drawings have to have some tolerance placed on them because it’s not possible to make something exact in the real world. If you ask someone “cut that thing into three 1 inch long pieces” you won’t get three exactly 1 inch long pieces. They might all be really close to 1 inch, but not all of them will be exactly 1 inch because exactly is a difficult thing to achieve. How do you know if they are all close enough to 1 inch for whatever you need them for? That’s where the tolerance comes in, it sets an upper and lower limit or a range on what is acceptable as a 1 inch piece for a particular application. Sometimes it might have to be really really close to 1"  and the tolerance will be really small, other times it might not matter much and the tolerance can be a lot. That’s the concept anyway and you can apply that to not only dimensions but also other more abstract things like shapes. “Is this thing flat enough?” “is this square piece of metal square enough?” etc.. of course ‘square’ and ‘flat’ will have to have some number associated with them (and a way to measure them) and that number will have a tolerance.

  

A Part Made Exactly To The Drawing

 

The reason that I am mentioning this is because in mechanical drawings the tolerance on the dimensions plays a big part in what the final product looks like and whether or not it’s going to work. The tolerances control what the shape of the part is or can be and they are just as important as the dimensions themselves. In fact it shouldn't be too surprising to read that in Geometric Dimensioning and Tolerancing it’s all about the tolerances! To get an idea of what I am talking about have a look at the picture below of the square thing with the hole in the center. I have left a few dimensions out of the drawing for simplicity and to explain the concept so don’t worry if it looks incomplete.

Homemade Ranque Hilsch Vortex Cooling Tubes: FAQ

One of the most popular things that I have done and blogged about is the Ranque Hilsch Vortex Tubes that I built. I get a lot of emails asking a lot of questions about RHVT’s and how to build them. There are no easy cut-and-dry answers to most of these questions because there are so many variables involved when building one, but there are some generalizations that can be made. Recently I decided to put together a FAQ page and with the help of a colleague and on line collaborator: Théo M. we have tried to answer some of the questions people have asked me. I am not at all an expert on these things and only know what I know by reading information online and from my own experiments. If you are planning on building one of these please look around at all the information the net has to offer and by all means contact me if you have any questions. At the end of this post I have placed some links that I have found useful.

  

As always when working with anything potentially dangerous (like compressed air) always wear appropriate protective gear like safety glasses and know what you are doing. If there are any questions that you may have that are are not in this FAQ or not answered clearly please email me at ottobelden@yahoo.com or leave a comment and I’ll be happy to answer you!

  

Homemade Vortex Tube Instructions from THIS post

   

If I get more questions in emails and comments on my blog I'll answer them below in this post and update the date below. I'll highlight any new info in the post so it will be easy to find.

FAQ UPDATED: 7/21/11

Check back often if you are curious or after you ask me a question. I'll answer you directly and add your question and answer to this post. Continue reading for the FAQ's and links!

Geometric Dimensioning and Tolerancing (GD&T) Introduction

As a mechanical person I get asked a lot of questions about drafting, mechanical drawings and Geometric Dimensioning and Tolerancing or GD&T. I have written emails over the years  to friends and colleagues explaining some of the concepts and recently I have begun to help some folks learn it from scratch. Because of this I have decided to start writing some posts about this topic for some of the following reasons. One reason is this blog is about the things that I am doing and GD&T is one of the things that I do as a mechanical designer. Another reason for writing about this topic is the same reason I had in creating this blog: People ask me what I'm doing and building and it's easier to answer them in a blog post and let them all read about it in one place rather than me emailing a bunch of people over and over again. Also I'm writing about this topic because this is my blog I can do whatever I want

;-)

  

As I write more posts about this topic they are not going to come in any particular order and are not really intended to be a instructional course, they are just answers to questions that I get. As always with anything that I write about if you have any questions you can email me at ottobelden@yahoo.com or leave a comment. I'll be glad to answer any questions that you may have.

  

Geometric Dimensioning and Tolerancing

 

If you are interested in and not sure what Geometric Dimensioning and Tolerancing (GD&T) is check out this link HERE on Wikipedia. There is a general overview of GD&T and a neat interactive chart that is fun to play with. I'll summarize the topic generally by saying that GD&T is a language of mostly symbols used on mechanical engineering drawings that communicates the design intent to a person who is using the drawing to make something. GD&T is a international standard (or several actually) that controls all the physical aspects of what the drawing is describing in a single, concise and unambiguous way. From the drawing you should not only be able to make something but you should also be able to check and measure the thing that has been made to see if it's correct. Specifically Geometric Dimensioning and Tolerancing is a way to use dimensions to describe exactly what you want a thing to look like when it's made and how much that thing can deviate from exactly perfect and still be correct. The reason for this is you can draw something perfectly flat, round, 6 inches long etc...  but when it's actually made it can never be EXACTLY those things. Even machines can't cut or shape something to be exactly perfect, there has to be a tolerance with every dimension. For example, how much out of round is OK? How warped and not flat can a surface be? How much longer or shorter than X inches is OK? How do I read the drawing in a way that lets me check the parts dimensions? How do I know if the thing I am drawing will fit together with something else? Geometric Dimensioning and Tolerancing answers those questions and a lot more.