Long Board - New Project

After a year of walking to class I decided I needed a long board to get to class. In my usual style I figured I should make one instead of buying one. I started by doing some research on the designs and standards for long boards and skate boards. I saw a number of different truck designs that seemed common. It seems that the rubber bushing style of truck is the most popular. In this design the truck is forced to straighten itself out by squished pieces of rubber. These pieces give the boarder more resistance as they attempt to steer the board. My personal favorite design used metal springs instead of the rubber bushings. I like to design things to last. I figured the springs would never deteriorate with time. Unfortunately I couldn't figure out how to make the trucks small and use the springs. Eventually I decided to go with the standard design for long board trucks. The one thing that really bugged me about this truck design was there wasn't a defined mechanism that caused the truck to turn. The pins in the trucks relied on a loose fit in order to actually turn. I started to look for an improvement when I stumbled upon spherical bearings on Mcmaster. These bearings gave freedom in all directions, which was the exact motion I needed. I designed the trucks around these bearings.  The spherical bearings give the trucks fully defined motion.

After deciding on the components I immediately started up SolidWorks and started poking around with different designs. Eventually I settled with this design for the trucks.

This render of the entire board has an older design for the trucks. I spent a few days changing around the design to make it easier for me to machine. The best looking board in my opinion was one made from 1/2" polycarbonate. I figure this board will really stand out when around the regular long boards.

I split the truck into many different pieces to avoid material removal. The biggest limiting factor when I'm machining is removing material. Splitting up pieces meant a large portion of the parts were extruded aluminum with holes drilled in them. Parts like that are really easy to produce with a manual machine. The design also meant that I only needed CNC work for the bearing seats and the side plates for the trucks. I attempted to locate the parts by geometry instead of the bolt holes themselves. The most critical surfaces required parallel edges, which are very easy to produce in one setup on either the manual or CNC mill. The only new thing for me on these trucks was the use of spherical bearings. I hope they perform as well as I imagined them performing.

Powered Desk Chair

This project had a lot of potential, but I kind of let it fail. Maybe I'll finish it one day, but it probably won't be any time in the near future.

I had an Ikea desk chair that didn't roll very well, so I figured I'd modify it into a powered desk chair. It would have "swerve modules" to give it the ability to strafe and turn just like a normal unpowered desk chair. The design was fairly simple stuff that I had basically done in robotics at my high school. The intended final chair would have looked like this, but the electronics required to make it run properly were a bit out of my budget range.

The continuous 40A motor controllers put the electronics out of my budget considering the ones I had used in the past cost around 90 dollars a piece. I made the three swerve modules before I decided to ditch the project.

 As with most of my projects I had to use the arbor press. It took apart that Ikea chair with ease.

Even though I bagged the project I learned a lot from its construction. In order to make the sprockets I wrote a program in python to generate the g-code for my CNC to cut any size sprocket. I also learned what tolerances are needed to make a chain drive without a chain tensioner and I also learned what tolerances work with bevel gears. Did I mention that I also have 3 very cool looking paper weights?

Phone Case Finished

Well I started the case in August... Now its January...

I was a bit of a klutz and in the middle of a bit change from the drill bit for a #2 screw through hole to an 1/8" mill bit I didn't realize that the screw on my CNC's drawbar had backed out. My CNC has a somewhat unique drawbar design that requires a spanner to tighten the collets in place. The collets are really small, only around a 1/2" at their largest dimension. I did some research one time and found out what they were, but I can't remember what they are. I vaguely remember them as ww collets, but I could be completely wrong. In any case my collets use outside threads. When the screw loosened on the drawbar it bottomed out on the collets threads. I didn't realize this and continued to turn the drawbar to tighten the mill bit into the spindle. Sadly the tiny amount of torque I put on the machine was enough to shear the 1/32" pin that slips into the collet's keyway. The collet became stuck in the spindle and the mill bit wouldn't hold in. I had to leave for school, so any machining in the Secret Underwater Base / Machine Shop had to be put off until December.

Surviving a semester of school took its toll on me and left me sleeping a lot over break. Therefore I didn't work on all of the projects I wanted to finish. The phone case turned out to take 3 days. I got lazy again and machined the center ring that surrounds the phone from polycarbonate. In my opinion it looks better than the aluminum anyways.

 This was the cursed part that I broke my spindle while making. Once I had my new spindle (which I got repaired and the bearings replaced for free) the part came out pretty quickly. I did discover that my mill bits were all fairly dull. I'll have to order a few more. Thankfully 1/8" mill bits are pretty cheap.

The case turned out exactly as awesome as I had imagined. It does have a few drawbacks...
-It is really heavy. I don't particularly mind, but I really doubt there are many other people that would want a phone that weighs as much as this one.
-It is really huge. This thing rivals a brick... enough said.
-It is sharp. I had to use cap head screws because the hex set I carry around doesn't have a key small enough to tighten a button head screw. So far I only cut my leg once. I attempted to climb over something and one of the screws dug into my leg. If I get cut again I'll replace the cap head screws with button heads.
-It needs a hex set. I'm screwed (hahaha its a pun) if I ever need to remove the battery and I don't have my hex set with me.

It may have a few drawbacks, but I love the case and will probably leave it on the phone until I replace the phone.

Phone Case - New Project

My phone was a little bit too bland for me, so I decided it needed a cool case. I couldn't find one that I liked for it, so making one in the shop was the next best option. A few years ago I had designed a case for my IPod, but I never got around to machining it because it required me to write too much code for my CNC.

It was made from 2 pieces. The front plate was simple and could all be machined in one setup, but the back piece need to have the center machined out. Aside from the time required to write out the tool paths by hand, the machine time on my CNC would have been too unbearable for me to make the case. This did however serve as the basis for my phone case concept.

I started off designing the phone case by getting the dimensions for my phone. Thankfully it wasn't one of those "ergonomically" shaped phones, so the phone was basically a rectangle with rounded corners. After taking down the dimensions I opened up SolidWorks and started playing around with different concepts. Eventually I came to this design.

The general concept was a ring that surrounded the phone and a plate on the top and bottom that held the phone in place. The ring only requried a slot to be machined around the inside perimeter. This would leave a nice little plug of material in the center that could be used for another project. This case needed #0-80 screws. Since the sides were so thick the case needed button extenders to allow me to actually use the phone. For some reason my first thought was to machine small holes in the side of the case for the buttons to slip into.  This design quickly turned my simple ring idea into a nasty 4 sided machining job. I don't have an edge finder for my CNC, so I was not in the mood to re-zero it multiple times on a single part. With ease of machining in mind I redesigned the case again.

(This render came after making the case. I got lazy and used polycarbonate instead of an aluminum ring as I had originally Intended)

This new design gave me the option to do all of the parts with single sided machining and minimal material removal. Both are things I strongly prefer when producing any part. Hopefully the case will be a quick one day project.

Replacement Transmission

Over the course of the 2009 FIRST robotics competition season, we discovered that the team's robot needed a new set of transmissions. I had driven the robot during the season. I thought the high speed of our robot was a major advantage, but the motors had overheating problems. Having built the robot's transmissions for the previous two years I figured it was a good idea to get the newer team members more involved in the transmissions. I offered advice and "pro tips" to help them along, but they designed the transmissions themselves. Even though I didn't design them, I still made most of the parts so they would get finished in time for an off-season competition.

These transmissions didn't require a lot of machine time. The axles had to be cut to length and the gears had to be bored. The plates were cut by another member of the team. There were some 13 tooth gears that I had to make custom. These were made in the exact same way as the gears in my prototype shifting transmission.

They should prevent the motors from burning up at any future competition or demo.

Prototype Transmission Finished

Aside from cutting the gears the rest of the transmission came out really fast. The gear bore's had to be finished. Some gears got keyed, while others had a pattern milled into them for the shifter. I went with a tripple key because these transmissions are thrashed around from forward to reverse under high loads. Eventually a single key loosens up and falls out. I used 3 keys instead of 2 just because I like the symmetry better. If you've seen a double key before, you know it looks awkward.

 I needed to use snap rings on the output axle of the transmission. Sadly I didn't have a proper grooving tool, so I just used a threading lathe bit. The snap rings seem to hold in place just fine. They'll work for this application but not for high side loads.

With the gears, axles, and plates done I just needed to finish the standoffs. I used tubing so all I had to do was cut them to length with the cutoff tool on the lathe.

With all of the parts finished I just had to assemble the transmission.

 Every project needs the arbor press. The gears had a 0.001" press fit along with the triple keys. I figured this would be pretty much indestructible.

The final product looks pretty clean. I'll test it in the next few weeks. Hopefully it performs the way it looks!

Gear Cutting

I decided to be cheap and make ALL of the transmission's gears myself. I'd machined a few gears in the past, but I figured I had more patience than before so it wouldn't be too bad. I started off by turning a "blank" for the gear. This was just a cylinder of the gear's outside diameter. Then I had to machine the teeth into the blank. This is the nasty part. There are a set of cutters meant for involute spur gears. There are 8 cutters required to cut any number of teeth for a particular tooth size. Each cutter has a range of teeth that it can cut. This is because of the gear's tooth profile. A standard gear has what is called an involute curved tooth. This curve is essentially the path taken by the end of a string that is unwound from a spool of thread. Gear teeth require this shape for their teeth in order to have a smooth and constant rotation rate.
Cutting the teeth requires a rotary table or spin indexer and one of the involute gear cutters.

The gears came out looking pretty nice. I'm a bit concerned for the 13 tooth gear. The involute gear cutters don't cut prefect profiles for all the numbers of teeth. 13 tooth gears have the worst profile. It should work in the transmission, but it will probably sound terrible.