The cable winding pulley was the most complicated part of the machine due to it’s multiple set screws, flat surfaces, precise bore, and threading. One set screw holds the pulley on the shaft. The other set screw holds the cable firmly attached to the pulley.
Here is a picture of the pulley mounted to the DMM Tech Servo Motor. In the background you can see the cable go up through the top of the machine, over the free pulley, and back down to hold the main slider mechanism.
In the Stain Dipper Machine, we have a top pulley which is mounted on a 10mm shaft that is seated in 10x26x8mm bearings. In the last post on this topic, I showed the pulley holder assembly. In this post I’ll show the pulley and the final assembly.
Here is the finished pulley, made from a 1″ long by 1.5″ diameter piece of brass.
Here is the pulley mounted on the top of the machine. This is a satisfying point in the project because of all the ways this could have been solved, we chose an elegant, smooth, and accurate one. You can’t buy this specific part anywhere in the world – we designed and made it just for this purpose.
Here is a picture of tapping the pulley for a M5 set screw.
This is a picture after the first operation was complete. Now we need to turn it around in the lathe, recenter it, and finish the other side.
Here is a picture of the part in the lathe. Notice the difference in surface finish? The shiny area is freshly cut. The dull area was original surface. The semi-dull area was shiny just an hour before, but oxidization got to it that quickly.
A view of the spinning 4-jaw chuck and quick change tool post.
A friend of mine needed a bushing assembly for his street bike to be reduced in width by about 0.230″. Having a 1930’s South Bend Lathe in my shop, I naturally said “come on over”.
My respect for machinists just went up a few notches (it was already high). I’m also glad I got a 4 jaw chuck for the lathe instead of a 3 jaw.
4-jaw chucks allow you to hold irregular work and precisely center it. The process for doing so can be tedious, but it’s a good feeling when your indicator reads in at less than 0.001″ variance from side to side.
This little project was fun for a few reasons. The assembly comes apart into several pieces. The little ring has multiple inner diameters used for different things, so it needed to be machined carefully on both sides. Holding small and irregular parts is a challenge. But seeing it all come together was great.
Gord over at Gord’s Garage has been busy with home-based anodizing. It’s some amazing stuff he is doing. I sent him one of the rubber band gun assemblies, and he did an amazing job on it.
In an incredible amount of detail, Gord has written up and photographed the whole process:
http://gordsgarage.wordpress.com/2011/11/21/the-full-monty-part-1/
http://gordsgarage.wordpress.com/2011/11/22/the-full-monty-part-2/
In summary, it went from this mill finish:
To this polished finish:
To this anodized finish:
Amazing!
A few photographs of our assembly of M6-002 to M6-005…
It all started by laying out all of the pieces for each assembly. Quite a few when you add them all up. Pictured below are the parts for 4 assemblies. Receiver, Pins, Actuator, Hammer, Trigger, Washers, Springs, Bolts, and Nuts, along with some tape to hold the loose pins in (temporarily).
Refer to https://blog.gahooa.com/2010/09/23/rubber-band-gun-6-four-pieces-explained/ for more information on each piece.
Here is the receiver. Note, the two small holes beside each other. This is to allow for an adjustment to spring tension if needed.
These springs are tough little guys. ~ 9 pounds per inch, with a max travel of just over 1/2 ” (if I recall correctly). They also cost $1.29 each in quantities of 100+.
In order to use them, I needed to snip the closed loop open on one end.
Following this, the springs were hooked onto the actuators.
Using dowel pins, we placed the actuators and springs into the receiver…
… separated by red, hard fiber washers. These washers have a very tight thickness tolerance, which is needed in this application.
Once the actuator was in place and the springs fully connected, we inserted the hammers.
The hammers had more room for spring stretch, so we opted for a cheaper, longer stretch spring (about $0.50 each in small qty).
The most interesting, and hardest to machine piece in the assembly is the trigger. Due to an error in machining, the trigger hole was drilled to just 0.250 inches, instead of the 0.1875 the drawing called for. I purchased a 0.2503″ reamer (accurate to +/- 0.0001″ (yes, a ten thousandth of an inch). This made the trigger fit perfectly on the dowel pins (but only after blowing the dust out!).
Another view of the trigger. Notice the step in the aluminum… This is what causes one hammer to release before the other.
I chose stainless steel screws to hold the mechanism into the wooden stock, although other methods could be employed. Plus, I just like close up photographs, so I included this one.
Here are the four assemblies finished. The tape is placed over any loose pins to keep them from falling out. The wooden stock will retain them firmly, similar to the design of a Ruger 10/22.
A close up shot of the receiver.
And the excellent helpers…
Now we just need to make several more stocks!
After a long wait, we have finally finished the first of a limited production run of Rubber Band Gun #6… It works great!
The Gahooa Perspective 