Introduction: The Design of "Cylinder Notes MHALL.stl".

About: Our grandkids keep me busy!

Instructables Member brmarcum asked if I could provide design details for the "Cylinder Notes MHALL.stl" part used in "Four Whistles Version 2" ( This cylinder activates the cylinder arms which in turn activate the valve arms and valves via 2.5mm tall "bumps" located on/around the cylinder surface. So to brmarcum, here it is, an Instructable that details the steps I performed in designing the cylinder and all of its bumps.

As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make mistakes in plenty.

Designed using Autodesk Fusion 360, sliced using Cura 2.3.1, and printed in PLA on an Ultimaker 2+ Extended and an Ultimaker 3 Extended.

As mentioned in the Four Whistles Version 2 Instructable, I designed the entire model using Autodesk Fusion360, and I have included the file "Cylinder Notes MHALL v2.f3d" which is the exported version of the actual design for the cylinder. Load this file into Autodesk Fusion360 to view each step I performed in designing the cylinder.

The song I chose for the first Four Whistles Version 2 is "Mary Had A Little Lamb". The song used the notes C, D, E and G, and in my rendition required 30 valve activations, and at what I estimated would be a reasonable cranking speed, the song would play in about 10 seconds. With this information, and considering the printing tolerances of most 3D printers, I determined that a cylinder surface diameter of 40mm would accommodate the number of notes required and the time to play the song.

Step 1: Notes Spreadsheet.

I started the design process by creating a spreadsheet of the notes required for the song. I've attached a PDF of this spreadsheet.

The spreadsheet contains four columns, one each for the notes C, D, E and F.

The spreadsheet also contains 36 rows, 30 for each possible valve activation, and 6 left over for silence at the end of the song.

The spreadsheet is populated with "X"s, red and yellow boxes. Each X represents a valve activation. When an X appears in a red box, it represents a single valve activation (short or "standard" note). When an X appears in a yellow box, it indicates an extended valve activation (long or "extended" note).

Step 2: Cylinder Notes Pattern.

With the notes spreadsheet completed, I next designed an Autodesk Fusion360 "component" to use as a notes pattern template for each of the C, D, E and G notes used in the song. This template would then be copied and pasted into the C, D, E and G "components" to create the cylinder bumps.

With the spreadsheet containing 36 possible individual valve activations, and a circle being 360 degrees of arc, dividing 360 by 36 results in each note spanning 10 degrees of the cylinder surface. As you can see in the cylinder notes pattern image, there are 36 "incomplete bumps" surrounding a 40mm diameter outer circle and a 37.60mm inner circle. Each of these "incomplete bumps" become "notes" when they are completed as described below.

The 40mm outer circle will become the outside surface of the cylinder. The 37.6mm inner circle will become the inner surface of the cylinder. These two circles will provide the cylinder with a wall thickness of 1.2mm (the cylinder is hollow to reduce the amount of plastic required to print it).

The incomplete bumps consist of a slanted solid line, an arc segment, and a dotted line, all connected to the 40mm outer circle. The slanted solid line is the trailing edge of the bump and is used to reduce the hammer effect of the cylinder arms on the cylinder as a note is completed and the valve is closed. The arc segment is the top of the "bump", at 2.5mm above the cylinder surface and spanning 5 degrees of arc. The dotted line represents what will be the leading edge of the bump and is used as a guide line when completing a bump to create the note.

The top most incomplete bump is located at 0 degrees, the bottom most incomplete bump is at 180 degrees, the left most incomplete bump is at 270 degrees, and the right most incomplete bump is at 90 degrees. The degrees correspond to the left most column in the notes spreadsheet labeled 0 through 350. If a note is required at the 0 degree position (the first note of the song is E for example) then I draw a line to complete the bump, and thus creating a note, using the sketch line tool and the dotted line as the guide. As each note is properly created, Autodesk Fusion360 will color the inside of the note indicating that it is a completely enclosed surface.

Step 3: Cylinder Notes Pattern C, D, E and G.

With the cylinder notes pattern complete, the next step was to create a new Autodesk Fusion360 component, and label it "Notes C".

After activating this component, I create a new sketch for it, then copy and paste the cylinder notes pattern into the new sketch. Using spreadsheet column "C" as a guide, I simply draw a sketch line, using the dotted line as a guide, between the bump arc segment and 40mm diameter cylinder surface circle, at each degree position around the pattern wherever an X appears on the spread sheet. This creates a note and as previously mentioned, Autodesk Fusion360 will color the inside of the note when this line is correctly added. For long ("extended") notes, I use the sketch extend function to extend the notes arc segment to the next notes arc segment.

Once all the lines have been drawn, I stop the sketch, extrude each bump to 3.6mm (1.8mm symmetrical), and extrude the surface between the 40mm and 37.6mm cylinder lines to 8.6mm (4.3mm symmetrical) using the modify, press pull tool. When properly extruded, all the bumps will be centered between the edges of the cylinder surface. To complete Notes C, I place 2.5mm chamfers at each end of the note bumps to facilitate 3D printing.

With Notes C completed, I repeated the same process with Notes D, Notes E and Notes G.

Step 4: Completing the Cylinder.

The final Autodesk Fusion360 component is the cylinder body. To create the body, I created two sketches, one for each end, at 52mm (the length of the cylinder body) apart. Next, I extruded the cylinder body into the shape shown, then extruded the axle 9.75mm and the bushing 3mm, as shown. On the drive end of the cylinder body (the end opposite the axle end), I extruded the drive hexagonal hole surrounding surface 8mm as shown.

With the cylinder body completed, the final step is to align the individual notes patterns with the cylinder, then combine them all.

First, I positioned each notes pattern 14mm apart (center to center). In the image shown, the right most notes pattern is C, then proceed to D, E and finally G from right to left. Once positioned, I aligned the notes patterns such that Notes Pattern C is .7mm from the axle end of the cylinder body. When all are properly positioned and aligned, Notes Pattern C will be .7mm from the axle end of the cylinder body, Notes Pattern G will be .7mm from the driven end of the cylinder body, and there will be a 5.40mm (edge surface to edge surface) gap between each notes pattern.

Finally, using the modify / combine function, I combined each notes pattern with the cylinder body, using the cylinder body as the target, and each note pattern as the tools. I also elected to keep the tools since there was more than likely a need to modify them at some point.

That is how I made the "Cylinder Notes MHALL.stl" part used in Four Whistles Version 2 ( If you have any questions, please feel free to comment and I will do my best to respond.