White's Pulley

This is called a White's Pulley. This particular design uses 2 3-stepped pulleys. Said by Quackenbos in 1859 "This pulley was invented to reduce the friction of each block to a single wheel.” I personally wanted to create one because I have yet to find a record of one actually being physically built before mine.

It is comprised of the following parts

• 1 backboard

• 2 supports

• 1 or 2 (preferably 2) axles

• 1 overhang (this will be defined later, but it is the red part of the machine in the image above)

• 2 stepped sheaves

• 1 string

• Optionally, 1 weight

• (Strong) tape

You will need these machines:

• 3D Printer - This is for the overhang

• Lathe - This is for the axle(s)

• CNC Router - This is for the backboard and supports

You will need these materials:

• Plywood - This is for the backboard and supports

• 3D printer filament - This is for the overhang

• Metal bar - This is for the axle(s) (I chose an aluminum bar)

• Stepped sheaves (mine were zinc)

• String (I chose nylon)

Note: Everything listed in bold is a purchased part, and thus, this guide will not describe their manufacture.

To begin the design process of the product, I built a rough prototype, and rough it indeed was. It was nonfunctional. The original sheaves were 3D printed, and thus, where supports were broken off, it would catch on whatever string I attempted to use. On top of this, the sheaves were far too light for any string to hold properly. If I attempted to use it, it would fall apart as soon as it snagged on itself, which was always instantly. In the end, I converted the prototype into a model of what the final product would look like, though at the time, I did not have the proper materials to build it.

The amount of time between the construction of this prototype and the final product was, unfortunately, quite high. I came to the conclusion after a few tests that the sheaves simply could not function as light 3D prints; I came to the conclusion that suitable string with the right amount of friction was simply not available in the classroom as well. In addition, since I was planning to upscale the final product, and thus, I could not lathe the sheaves, as the desired size was simply too big for a lathe and the materials I had access to. I opted to order both of these parts, but the school put off ordering it by multiple months, so I got them last-minute.

The design itself has generally been the same since conception, as one can observe here.

Also, notably, the original design for the White's Pulley had the lower sheave be smaller than the upper one, but finding stepped sheaves in a proportion ideal for the original design was next to impossible for me. I opted to go for two identical sheaves in the end, which worked out fine.

I am going to assume you have access to all parts described earlier and state that I recommend first and foremost that you order the parts you need as soon as possible for this project, specifically the sheaves. In my experience, it took the school multiple months to follow through, though if you are not in my situation, it may be quicker! I got my zinc sheaves and nylon string from McMaster-Carr, but you can choose whatever retailer you wish. The sheaves are ideally metal and heavy, and the string ideally can grip the metal somewhat to be a proper belt for the sheaves.

Take note of the size of the sheaves you ordered, and model the rest of the pulley system around their dimensions (the axles should fit the hole in the middle of the sheaves, the overhang should leave enough room for them, et cetera). The reason you will want to prioritize customizing everything around the sheaves you purchase is because they are not a common part. These are called "stepped sheaves." They are also called "adjustable size sheaves," which is a function we will not be using them for. Finding stepped sheaves for sale in your ideal size is extremely difficult, as they are an extremely uncommon part, and thus available in only a few sizes. It is far easier to look at the options you can find, pick one to order two of, and measure out everything to accommodate them. It would be tragic if you were halfway through building and designing, but found no stepped sheaves that fit what you had already made. Side note: there are stepped sheaves for sale where the size of the grooves don't have a consistent descending size; these are not recommended.

Manufacturing method: CNC router

Material: Plywood

A board of plywood is cut into three pieces: two identical triangular supports and a backboard to hold up the pulley system and overhang. The supports only stick out from the front, as the entirety of the weight of the device is located in the front. The very first design had the supports extend both forward and backward, making them symmetrical, but I found that extending out the back was unnecessary, and it took up more space than it needed. The top of the backboard should be able to fit into the bottom of the overhang, and two slits on the bottom attach it to the supports.

I modeled mine in Fusion360 and set it up to be cut on a CNC router. I recommend choosing a thick plywood that doesn't easily bend or break. Once cut, smooth the edges with sandpaper.

Manufacturing method: 3D printer

Material: Plastic 3D printer filament

"The overhang" is what I call the part that holds the upper sheave. It plugs into the backboard and contains two holes, fitting an axle. The sheave should be able to be held by this axle, and the overhang should reach high enough to contain it. On my device, this part is bright red. The design has changed very little from conception to final. The first 3D model was significantly wider, but it was concluded that that was a waste of plastic. Other than that, the design remained fairly consistent with the first sketches. Once printed, remove the supports. I recommend pliers.

Manufacturing method: Lathe

Material: Aluminum

These need to be just thin enough to fit in the overhang holes and through the sheaves, but thick enough that they don't jangle around, otherwise, they will roll out of the device. The first (mandatory) axle holds the upper sheave in the overhang. The lower sheave can optionally also have an axle for the purposes of attaching a weight.

If the bar you find fits perfectly, great! Just cut it to an appropriate size (being able to stick out from both ends on the overhang, but not too far) so that it doesn't come loose. However, it is very likely that it will be too thick, so you will want to shave it down with a lathe until it is the right size. After shaving and cutting, the edges at the ends of the axles will be sharp; please file them down for the purposes of safety.

Note about weights:

I fashioned a rudimentary weight out of pipe cleaners and a brass bolt, which increased performance, and I am sure that this device can hold greater weights than depicted here. I encourage you to find your own method of attaching a weight, as there are surely far heavier weights this pulley system can hold, and far better designs that are anything but rudimentary like mine, but that duty lies on you. My first weight design was a small bottle that could hold metal balls and was attached to a 3D printed device that held onto the bottom axle, which I dubbed the "underhang." I ran out of time before I could properly measure out and manufacture it, though. Perhaps your design can contain something similar!

Once all parts are purchased, manufactured, and then fixed up to be proper (such as sanding and filing), simply follow this step-by-step guide:

1. Stand up the backboard and plug both supports into the bottom holes so that they are both facing forward.
2. Plug the operhang into the top.
3. Slide one stepped sheave into the middle of the overhang and feed an axle through the holes to lock it into place. It should be able to spin easily. The overhang should face the same direction of the supports.
4. This is the hardest stage. Hold up the other sheave below the overhang and put the pulley system together. This entails putting the string over the back groove of the top sheave, then under the back groove of the lower sheave, then over the top's middle groove, then under the bottom's middle groove, then over the top's front groove, then under the bottom's front groove, and then taping the string, which should be pointing up, to the front of the overhang. If that sounded confusing, I drew something to help you visualize it (look in the image of a paper in the next step). If your chosen sheaves have more than three grooves, you can still do this pattern with however many they do have. Now, when you pull on the other end of the string, the sheave on the bottom should spin and raise, and when you release, it should lower. You are done!
5. You might want to add a weight to the pulley system, as this is the purpose of a pulley. I'll leave this step in your hands, but I personally made a net out of pipe cleaners, though I had a much more sophisticated design that I never was able to manufacture. Ideally, it is attached to an axle on the bottom so as not to be interfered with by the sheave spinning. Be creative!

I altered the design from the original so as to improve it and manufacture it easier; the sheaves originally had to be a specific proportion to each other,* but finding two of this proportion was nigh-impossible, and it functioned fine when they were the same size in the end. Still, mathematically, the original size proportion is superior and theoretically less likely to malfunction. The original designs, which are from the 1800s, also had the whole device suspended by a hook, which I believed to make the device likelier to fail, so I opted for a design that locked the top sheave in place. Though I used multiple drawings from multiple sources for reference, I found the concept in a book titled 507 Movements; it is movement #15.

While still a White's Pulley, this design is unique, and thus, I want the reader to feel free to alter what they see fit. This is but one possibility for what this device can look like, but there are plenty of other ways it can be gone about! Have fun with it!

*The proportion is described in the 507 Movements page I linked, but I describe it as this: the lower sheave's diameter would be the larger sheave's diameter minus the distance between the outer ridge and the one smaller than it. That may sound confusing; I find it difficult to word.