Climbing Monkeys (3D Printed Vintage-inspired Toys)

Hello everyone and welcome to my third instructable!

I love vintage mechanical toys: they were so clean and neat but yet so inventive in their solutions. No batteries, no electronics, just simple physical principles applied to clever and ingenious objects.

That's why I like to recreate some of them using modern technology like CAD softwares and 3D printing. And it is also a good opportunity to test different types of static or dynamic joints, always useful when you create 3d printed objects.

Step 1: Search for the Originals

Since vintage toys are not simple to find nowdays, I usually search for them on the internet. There are various sites (and a great YouTube channel) that collect information and images of antique toys.

Here I present you two different solutions to the same basic principle: a subject (a monkey, in my case) climbing a string.

From now on I will refer to the two toys by calling them:

One rope climbing monkey
Two ropes climbing monkey

Step 2: Materials and Tools

Materials:

3D printer
2mm string
M2x20 screw
M2 self-locking nut or 2x M2 nuts
Rubber band
Lighter

Tools:

Scissors
4mm allen wrench

Step 3: How Do They Work?

One rope climbing monkey
This monkey is represented sideways with:

one fixed joint - body-shoulders
one adjustable friction joint between hands
one rotation joint - body/legs
three fixed spacers, respectively:

at the knees
at the shin
at the feet

The string passes between the hands (between which adjustable friction is provided by tightening or loosing the M2 screw), behind the shin spacer, then up above the feet spacer and down free again. At the same time, an elastic band is positioned between the neck and the knees spacer and pulls the legs up, until they reach the fixed arms.

Pulling the string, you force the hands up along the cord and the friction should maintain them at the height reached. Then, the elastic band lifts the legs up and the monkey returns in the initial position.

So, by pulling the string multiple times, your monkey will raise up on her rope.

Two ropes climbing monkey
This monkey is represented frontally with four basic rotation joints (plus another optional one):

body-shoulders
body-waist/legs
two elbows
head-body (not essential, could be also fixed)

Special attention must be given to arms and forearms+hands: they must have two little holes (two on the right and two on the left side) in which the string will flow. The holes have to be misaligned so that, in resting position, the sliding through them is blocked.

When you pull one string, you force the two holes to align so that a portion of the cord could slide through them. So, pulling alternately the two strings, your monkey will raise up on her rope.

Step 4: Design First Prototypes

Since designing an object is often a trial and error process, I usually build some first, simple prototypes to evolve them test after test. For this reason, in this phase I don't focus too much on the external look.

The friction between the hands of the "one rope climber" was initially provided by two adhesive felt pads and adjusted by tightening or loosing the screw between them.

For both I designed and printed the essential parts and linked them using screws and nuts.

Step 5: Final Design Solutions: One Rope Climbing Monkey

Once you reach the perfect calibration of all elements in your prototypes, you can focus on making them nicer and cooler.

I love print-in-place objects and snap-fit techniques applied on 3d printing so I tried to implement some of them in my designs.

Print in place solutions take advantage of the capacity of FDM 3D printers to print one layer at a time, making possible to adopt shapes that would not be possible by simply assembling parts.

The correct amount of clereance left between parts is influenced also by various factors such as printer precision, nozzle diameter, plate calibration and more..so, the perfect gap for me may not be as accurate for others.

One rope climbing monkey

Fixed joint (body-shoulders) and fixed spacers

I used some simple snap-fit joints with low clereance, for a tight fit. The body-shoulders one has a square shape with rounded edges to lock firmly through the hole in the main body.

All the other joints have a circular shape externally (to let the string slide well) and a rounded square shape internally (in this case also a circular shape would have been fine but I wanted to test this type of snap fit that prevents unwanted rotations).

Rotation joint (body-legs)

It is another snap fit joint, similar to the others but with a larger diameter, inserted into a hole in the main body maintaining a gap of 0.2mm to guarantee a free rotation.

Adjustable friction joint

I have placed two holes in the hands in which to pass a M2 screw. At first, the friction was provided by two adhesive felt pads but then I decided to remove them because they were difficult to puncture and position. I realized that the perfect amount of friction can be reached by simply pinching the string between plastic hands.

Step 6: Final Design Solutions: Two Ropes Climbing Monkey

Two ropes climbing monkey

Rotation joints

Body-shoulders, body waist+legs and the two elbows joints take advantage of more or less the same design: one cylinder rotating into another thanks to a small gap (the clereance given, in this case 0.3mm) left between one another. For example, in the body shoulders joint, the male cylinder is fixed on the body, the female (let's say the hole) is made inside the shoulders "stick".

Not to allow the stick-shoulders to slip off, I added two flares that prevent any movement on the vertical axis (in reality, a minimum amount of movement is allowed by the gap).

The lower part of the body is designed to work as mechanical endstop for rotation between body/shoulders and body/legs.

The head

The head is printed separately and its design has been challanging because I wanted it to rotate but not along all 360° because, since the pivot is placed on the lower part and the upper one is heavier, a completely free rotation would have led to find the head often upside down.

After various tests, I found that the best solution was to provide the body of a fixed pin and print the rotation system directly in the head. The joint is similar to the others but with the addition of a small "stick" in the male part and an extension of the hole in the upper part of the female. The male part, moreover, has in turn a hole that fits rigidly on the body pin. This solution permits a free rotation of the head until it reaches the "stick" endstop at almost 20°.

The body

Going from the prototypes to the print-in-place version, I initially modified the body from rectangular to diamond shaped, to have smaller "bridges" (parts not supported by underlying material but deposed mid air). It worked very good but the body became smaller and less..simian.

So, I have returned to the prevoius, rectangular shape but, since I don't like supports that are automatically generated by slicer softwares, I provided the print of custom made ones: 4 more cylinders support the edges and should be quite easy to remove because of the gap of 0.4mm (2 layers, in my case) left between the part and the rest of the print.

Print the one you prefer.

Step 7: Print All the Elements

Print all the elements, including the string "spacer" and the two "stoppers" for the two rope version (all the files .stl are attached)

I print them with 0.2 layer height, 2 perimeters, 2 solid layers and 50% infill.

Take extreme care when removing the parts from the print plate because joints and parts in general are very small and could be easily damaged by excessive applied strength.

Consider that a bit of sanding to the pins may be necessary due to little imperfections in the printed parts.

Step 8: After Print Operations and Assembly Instructions

One rope climbing monkey

Assemble the parts:

insert left arm and left leg through their holes on the body
gently fit the pins of right arm and leg in their respective slots

Two ropes climbing monkey

Despite the given gaps, the rotation joints could be stuck when they come off from your printer. To unlock them, gently rotate the elements back and forth a few times.

For the head rotation mechanism, insert the 4mm allen wrench and do the same until unlocked.

If you have chosen the rectangular body version, you have to remove the built-in supports. I suggest you to use a cutter to remove the thinner ones while you can use a pair of pliers to gently force the thicker ones.

Simply snap fit the head on the body.

Step 9: Prepare Them for the Climb

One rope climbing monkey

Cut a piece of cord, burn the ends with the lighter and tie a loop on top of it
Tie the elastic band around the knees spacer and then around the neck
For the following passages of the cord, follow the scheme attached to step 3
Adjust the friction between hands tightening the screw and nut until you reach a perfect climbing. Then, if you don't use a self-locking nut, use a second nut to block the first one in position

To make this monkey work properly, you have to find the perfect balance between the strength of the elastic band and the friction between hands.

Two ropes climbing monkey

Cut a piece of cord, burn the ends with the lighter and fold in two
Pass the two ends through the holes in the spacer and tie a small knot just under it
Pass the two ends through the holes on the hands
Pass the two ends through the holes on the shoulders
Pass the two ends through the holes on the stops and tie a small knot just under them