Music Box

[NewAgent45]

Hello Bill Z,

I think this is a great design concept. I would design it like a weather vane, windmill, or whirligig which turns the prop into the wind. I would make the drum as light as possible and use bearings for minimum resistance. I have some experience with whirligig's and making my own props.

Something you should consider. The original music box design allows the drum to be rotated backwards and could damage the pins. I redesigned one of the drum end plates with a ratchet design this prevents the drum from turning backwards. I will be posting my completed Music Box when it is complete.

We'll look forward to seeing your wind powered on too.

Have a great day!

... Rod

[Bob]

Something you should consider. The original music box design allows the drum to be rotated backwards and could damage the pins. I redesigned one of the drum end plates with a ratchet design this prevents the drum from turning backwards. I will be posting my completed Music Box when it is complete.

...This is not a problem with this design. Cut the belt long enough so that it slips when when it engages a pin when turned in reverse. That's what I did.
Bob

[NewAgent45]

Bob,

Sure that will work. It meets the "KISS" principle too! <smile.

Given my previous learning on making gears I thought my ratchet design would be simple too Drawing the vector only took me 5 minutes and I used the ratchet vector to cut out the disc instead of the circle. I also used a smaller bit and there is a fillet at the bottom of the tooth. I will uses a simple arm with a spacer on the inside of the box using gravity to engage the arm into the ratchet. It may even add a little click to the beat of the music as I have 64 teeth on the ratchet. I could add a pull down spring to make it louder. Just though of that! <smile>

Pin drum ratchet design

I'm just getting started on this project. No rush as I I'm working on a couple other projects at the same time. I just had some Hard Maple delivered yesterday that I plan to use for this and other projects. We will edge laminate with biscuits for the wider pieces.

Have a great weekend!

... Rod

[Bob]

Rod,
I was planning to add a bumpy wheel instead of a ratchet. A small wheel would ride over the bumps and connect to a rod that would move a little conductor standing at his podium on top of the box...But I got to the point where completing the project as originally planned sounded better.
Your idea sounds like fun.
If you feel like really crankin', be sure to add a bumper bar over the little hammers to keep them from bouncing up against the drum pins and jamming the system.
Bob

[NewAgent45]

Bob,

Thanks for the tip on the bumper bar to prevent mallet over travel. Another change I made is to mount the pivot bar to the Xylophone rack instead of blind holes in the side of the case. I plan on a couple slotted pieces to allow for fine tuning the mechanism I can easily add the bumper bar too. The whole Xylopphone/mallet assembly will drop into the case as one assembly.

Another reason the bumper bar may be needed is my small drive pulley is larger (2” dia. instead of 1 ¼”). I located it a little higher and towards the rear for clearance. The reason I made the small drive pulley bigger is the urethane belt I ordered stated a minimum pulley diameter of 2” in the specifications. Sorry a retired engineer influence here. This means it will be less likely to slip.

I’m still learning the software and machine. I’m just into my third year. I posted for some help on edge cutting toolpaths. No one responded to my post. http://www.cncsharktalk.com/viewtopic.php?f=10&t=4811

I have learned part of the solution from the VCP reference manual. Could you please review my post (s)? I may find I need to write to Vectric tech-support for clarification. This morning I added a 3rd post regarding the use of “form tools”.

Have a great day!
.... Rod

[Bob]

Rod,
Sometimes combining techniques is easier than 100% cnc...
After cnc cutting the pulley wheels, I used my lathe to cut the belt grooves. The disk was held against the lathe faceplate using a 60 degree live center.
Since I wanted the belt to slip if cranked to hard, I used the smaller diameter pulley.
I like your idea of mounting the hammer pivots on the rack.
Bob

[Bob]

But, if I really wanted to cut those grooves using my cnc, I would give a serious look at leads in a profile toolpath:

Bob

[Bob]

The toolpath would look like this:

I think it would work.
Bob
The computer doesn't need to know if you have an edge cutting tool. You set the starting depth below the surface, set the leads long enough to allow your cutter to plunge beyond the edge of your disk, and let the magic happen!
Be sure to cut out the disk first. And, remove the scrap material too.
The depth of cut into the edge (depth of groove) needs to be regulated by consecutive smaller diameter groove circles computed as separate toolpaths... run them in order.
Since you're only going .125" deep, you could probably cut the groove in one pass though.
I should also mention that the 3D preview will not give an accurate picture of the completed toolpath. Similar to previewing a keyhole toolpath.

[NewAgent45]

Bob,

I don't have a lathe or access to one. That would have my first and best choice for these types of tasks.

I have to thank you again for another good tip. It looks like I could move my zero reference back to center. I think that is what your picture shows. I also assume you specified a circular lead and a lead length greater than the bit radius plus some additional clearance. I'll have to make a test run first cutting some air.

As for moving the hammer pivots to the rack, I feel it would be hard to get good alignment to get the mallet heads to bounce just right on the tone bars. I'm going to slot the arms that will support the pivot shaft. This will allow me to adjust the pivot height before installing the rack in the case.

Thanks again for sharing your experience.

... Rod

[rsetina]

Rick,
If you can figure out these directions, programming the pin location will be no problem: http://www.woodworkersjournal.com/wp-co ... Layout.pdf
Bob

Thanks for the link Bob. I liked the box so much, for $10 I subscribed to the magazine just for the plans. LOL