This is a project to design and build a Geneva wheel using Sketchup.
This design was recently presented as an instructable by iGreeny (Make Geneva Wheels of Any Size in a Easier Way). It is by far the easiest Geneva Wheel design that I have found.
Unfortunately for me the iGreeny project uses Fusion 360 as the design program and I rely on Sketchup for my design work. I did contact the author for permission to reproduce the design and received a very nice reply giving me permission to reproduce the project using Sketchup.
Although you may not have a specific use for the Geneva wheel, it is a fun wood working project and generates a lot of interest as a wood working project.
The Geneva wheel converts continuous rotary motion into intermittent rotary motion. Although it was originally designed to be used in Swiss watches, it now has a wide range of use in many mechanical applications.
For the hobbyist, it is a great way to get a small gear reduction package. The intermittent rotary motion has a significant dwell time and is locked in place during the dwell time.
This will be a four part process.
1. Design the major parts
2. Add details to all major parts.
3. Assemble the project using Sketchup
4. Make the actual wooden Geneva Wheel
This project will use the free version of Sketchup for the design. I am NOT an expert with Sketchup. I’m 78 years old and if I can make it work, you can certainly have fun with it too. You can download the Sketchup program from Google.com. if you don’t have any experience with Sketchup, there are hundreds of tutorials on youtube. For example, if you need to learn how to draw a circle, go to Youtube and type in “Sketchup circle”. There is also a very active Sketchup “Community” on line to help you with any problems you may have.
The Geneva wheel design eventually begins to get cluttered up with all the lines, angles, circles, etc. . Therefore as we go along, I will temporarily delete as much as I can to better view the immediate topic. I will also color each major part. I would strongly recommend that you also color each major part. It really helps to minimize the confusion and using Sketchup, it will also immediately identify a missing or broken line. Do NOT delete anything on your copy until you receive explicit instructions to do so.
To make sure we are all on the same page, we need to establish some terminology. Each of the main components are identified as shown.To make a Geneva Wheel using this design you need to know three things to begin with.
1. How big do you want the Geneva wheel to be (Radius)?
2. How many slots do you want in the Geneva wheel?
3. What is the diameter of the drive pin?
Let’s get started. I would strongly recommend that you do NOT cut any wood parts until you finish the complete design on screen.
For our example:
1. The Geneva wheel will be 3” (1 ½” radius)
2. It will have four slots
3. The drive pin will be ¼”.
Step 1: We'll Start With a Right Triangle
Draw a Right triangle as shown.
During this design process I will use the color PINK to show the part that I'm currently describing.
Angle “A” is 180°/the number of slots in the Geneva wheel. We have four slots in our example so angle “A” is 180/4 = 45°.
Angle “B” is always a right triangle, which is 90°.
Angle “C” is whatever is left over
The length of the A – B side of the triangle is the radius of the Geneva wheel. In our example it is 1 ½”.
Draw the triangle with the right triangle (angle B) on top as shown.
Step 2: Basic Geneva Wheel Start
Draw a circle for the Geneva Wheel.
Angle “A” will be the center of the circle. Again, in our example the Geneva wheel will have a 1 ½” radius. If you draw it correctly, the circle should just touch the top of the triangle side B – C as shown.
Draw a circle for the axle for the Geneva wheel which would also be centered on angle “A”. For our example we will make the axle circle 3/8" (Radius 3/16").
Note: To find the center of a circle, highlight the outside perimeter, right click, click on "Find Center". It will place a dot in the exact center.
Color the Geneva wheel green.
Step 3: Basic Pin Wheel Start
Draw a circle for the Pin wheel. Angle “C” will be the center of the circle. This circle should just touch the top of the triangle side A - B.
Draw a 3/8" circle in the center for the axle.
Color the Pin wheel yellow.
Step 4: Pin Slot Depth Circle
Now we have to add a temporary circle. The circle also uses angle “A” as the center. This circle should just touch the pin wheel circle. This circle will show the location for the bottom of each slot.
This circle should remain green as the Geneva wheel.
Step 5: Pin Depth Adjustment
We have to be extremely accurate with our wood working to get the pin to fit exactly at the bottom of the slot. Therefore I would recommend that you make the temporary circle about 1/16” smaller. Use the Offset tool to reduce the size of the temporary circle 1/16". That will make the slot 1/16” deeper so the pin doesn’t hit the exact end of the slot.
Refer to Step #24 for more info.
Step 6: Adding the Pin Slot
Now we can draw in the actual slot. The drive pin has to slide up and down easily in the slot. For our project the drive pin will be 1/4". I would recommend that you make the slot 1/16" wider than the drive pin to allow it to slide up and down with ease. For our project we will make the slot 5/16" wide.
Draw a 5/16" circle at angle “B”, and another 5/16" circle where the triangle side A – B intersects with the temporary circle. Then draw lines to connect the circles on both sides.
Color the Pin slot a light tan.
Step 7: Basic Lock Wheel Start
The last wheel to draw is the Lock Wheel. This is the wheel that locks the movement of the Geneva wheel during movement from one slot to the next.
Draw a line from the left side of the top 5/16" slot circle straight down to the triangle side A – C. Draw a circle at angle C which extends out to touch the line you just drew.
Color the Lock wheel blue.
Although the Pin wheel/Lock wheel are in the foreground, note that the Geneva wheel partially overlaps them. We will remove the partial overlap on the next step.
Step 8: Lock Wheel Adjustment
Now we need to get rid of the partial overlap between the Geneva wheel and the Lock wheel. The Geneva wheel has to partially fit inside the Lock wheel dip. The Geneva wheel should fit close to the dip in the Lock wheel but both wheels must be able to turn easily. That means the "dip" in the Lock wheel has to move back a little.
Highlight just the edge of the dip portion of the Lock Wheel and use the Offset tool to back it away from the Geneva Wheel by 1/32”.You will have to add a small piece of a line on each end of the dip to re-connect to the main circle.
Erase the original Lock ring dip. As we start erasing lines no longer needed, pay close attention to the colors used. If you erase the wrong line, the wrong color will bleed into the next one.
Step 9: Clean Up
At this point we can delete some of the lines also to remove some of the clutter. Use the step #9 picture to help guide you as to what can be erased.
Assume that the Pin wheel is partially on top of the Geneva wheel.
1. Erase the line from the top slot circle down to the bottom of the triangle. Note that there are several pieces to this line.
2. Erase the lines inside the slot.
3. Delete the temporary circle inside the Geneva wheel.
4. Erase the surface on both axle surfaces so the circles look like holes in the wheels.
Step 10: Add the Drive Pin
Next we will add the Drive pin. In our example the drive pin is ¼”. Draw a ¼” circle at the intersection of the triangle side A – C and the pin wheel.
Color the Drive pin brown.
Step 11: Adding Pin Wheel Platform
The drive pin is now sitting on the edge of the Pin Wheel. Now that we know the exact location of the drive pin we need to make the Pin wheel a little larger to give us room to actually mount the drive pin.
Draw another Pin Wheel circle centered on angle "C" on the triangle. Extend this circle out 1/4" beyond the edge of the drive pin. Make certain it does not touch the Geneva wheel axle. Delete the original Pin wheel.
If you prefer, you could make the Pin wheel extension a "tear drop" shape.
1. Draw a 3/4" circle around the Drive pin
2. Connect the sides of the 3/4" circle to the sides of the existing Pin wheel.
Step 12: Store Everything You Have
Change the colors so the Geneva wheel is on top of the Pin wheel. Erase the lines on top of the slot to open it up. You should be easily able to tell if you make a mistake because the color will change where it is not supposed to if a necessary line is deleted.
Delete the triangle.
All of the major components are now drawn. Select the entire image and make it a component. Name the component "Big 4" (which represents the Geneva wheel, Pin wheel, Lock wheel, and the Drive pin). Components are always stored in your Sketchup "tray".
Step 13: Complete the Pin Wheel
Now we can finish the details on the Pin wheel.
If your "Big 4" component is not on your screen, reload it from your tray.
Make a copy and delete the original. Explode the copy.
Erase everything except the Pin wheel and Pin.
Delete the surface of the pin on the Pin wheel.
Make the Pin Wheel axle. The axle will be 3/8" diameter and 2" long. Using the circle tool, create a 3/8" circle. Using the push/pull tool, pull or push it out to 2".
Click on the perimeter of the Pin axle. Right click and click "Find Center". That will create a dot in the center of the end of the axle. Using the same technique, find the center of the axle hole in the Pin wheel.
Using the center of the Pin wheel axle hole as a reference point, center the axle on the hole.
Adjust the axle so 3/8" sticks out on one side.
Now we can make the Drive pin. Using the circle tool, draw a 1/4" circle. Using the Push/Pull tool, pull or push it out to 1 3/8".
Using the same technique as used for the axle, find the center of the Drive pin and the hole in the Pin wheel. Move the Drive pin to the Pin wheel hole. The Drive pin should be mounted flush on one side of the Pin wheel. The Drive pin should stick out 1" on the same side of the Pin wheel as the 3/8" end of the axle. Refer to the photo to make sure you get it right.
Select the entire wheel. Make it a component. Name the component "Pin wheel".
Delete the Pin wheel from the screen. It will always be available to reload from your component tray.
Step 14: Complete the Lock Wheel
Recall your "Big 4" image from the component tray.
Make a copy.
Delete the original.
Explode the copy.
Delete everything except the Lock Wheel.
Using the Push/Pull tool, push or pull it out to 3/8".
Make it a component. Name the component "Lock wheel".
Step 15: Isolate the Geneva Wheel
The actual Geneva Wheel gets a little more interesting.
Recall the "Big 4" component from your component tray.
Make a copy.
Explode the copy.
Delete the original.
Delete everything except the Geneva wheel.
Step 16: Make All Four Slots and Dips
Now we need to make the other three slot and dips. Find the center of the axle. This will be used to rotate the slots. Highlight all of the edges of the slot and the dip. Click the rotate tool. Align the protractor on the axle center. Click CTRL and then rotate the edges 90 degrees. That should give you one copy. Now type in *3 to make it 3 copies instead of one copy.
Step 17: Geneva Wheel Final Touches
Delete the circle outside of each dip and the end of each slot. If you have trouble deleting only the desired piece, zoom in and check the lines surrounding the area and make sure they are actually connected. Just a tiny break will cause problems. Makes sure the surface of the axle circle is deleted. Then use the Push/Pull tool to make it 3/8” thick.
Make a 3/8" axle, 1 7/8" long. Insert the axle into the axle hole with one end flush to one side.
Make the finished Geneva wheel a component. Call it "Geneva wheel".
Step 18: Set Up the Base Plate
Let’s make a baseboard to mount the final assembly. Remember that we are still only working on the screen and not cutting any actual wood yet.
Draw a 6” x 4” piece of ¾” stock. Mark the location for the axle holes.
Step 19: Base Plate Shim
The Geneva Wheel has to be 3/8" off the base plate surface so it can overlap on top of the edge of pin wheel. The Pin wheel is 3/8” thick. Glue a small piece of 3/8” wood, approximately 2" x 3/4", next to the axle hole for the Geneva wheel as shown.
Step 20: Base Support
Now we will add a plate to support the base. The support will be made from 3/4" stock. The support is 7" x 3 1/2". If you have the equipment (router, sander, etc) round off the corners and the edges.
Step 21: Attach the Support to the Base
Attach the base to the support approximately in the middle of the support. You can attach it with whatever method works best for you. You could just glue it, attach it with screws, Wood pegs, etc.
Step 22: Crank
Now we'll make a crank to make it happen for demonstration.
Make a rectangle 2" x 3/4".
Add the holes for the crank handle and the axle. Delete the surface of both holes.
Round off all four corners.
Use the Push/Pull to make it 3/8" thick.
Make a crank handle 1/4" Dia and 1 3/8" long.
Insert the crank handle into the crank. One side should be flush with the surface of the crank.
Step 23: Mount the Pin Wheel
Next we will start assembling the components onto the base. We'll start with the Pin wheel.
Insert the axle of the Pin wheel into the axle hole as shown. Spin the Pin wheel to make sure it turns easily. You may find that after you get everything assembled that you may have to enlarge the hole slightly to get it to turn easily.
Step 24: Mount the Geneva Wheel
Insert the Geneva wheel axle into the opposite hole in the base as shown. Using the rotate tool, rotate the Pin wheel until the Drive pin engages the slot as shown. The pin should not touch the bottom of the slot.
Rotate the Geneva wheel 45 degrees. Rotate the Pin wheel 45 degrees. Check to make sure the Drive pin lines up with the slot.
Step 25: Install the Lock Wheel
Rotate the Geneva wheel and Pin wheel until the Drive pin is fully engaged again.
Install the Lock wheel on to the Pin Wheel axle. The Geneva wheel slot should be in the center of the Lock wheel dip.
The Geneva wheel should be very close to but not touching the Lock wheel. Make this fit as close as possible. When you actually build this project, a very tight gap here will make your project more impressive.
Rotate the Pin wheel/Lock wheel 90 degrees. Rotate the Geneva wheel 45 degrees.The lock wheel should be very close but not touching the Geneva Wheel. Again, the closer you make this gap the more impressive your project will be.
Step 26: Mount the Crank
Slide the crank on to the Pin wheel axle on the back side. Make the edge of the crank flush with the Pin wheel axle.
Step 27: Geneva Wheel Retainer
We need something to lock the Geneva wheel in place. So far we just have the axle sticking out of the back of the base.
We'll make a retainer using a piece of 3/4" dowel. Make a piece ~1/2" long.
Make a 3/8" hole in the center ~3/8" deep.
Round off the other end.
Mount the retainer on to the end of the Geneva wheel axle.
Your Geneva wheel assembly design is now complete!
Step 28: Geneva Wheel - the Woodworking Project
Your Sketchup design has all the parts necessary to make the complete wood working project. Now you can simply go through the design phase again but this time actually do it on wood.
Here are some construction tips that may make the project a little easier.
1. Wood dowels
a. They are not perfectly straight
b. They are not always perfectly round
c. Dowels made from Poplar will compress. Each time you squeeze an object onto the shaft, the shaft gets slightly compressed. If you remove the object, the shaft remains compressed.
d. Oak dowels are slightly larger in diameter than Poplar. Oak does not compress easily.
2. The axles for the Pin wheel/Lock wheel assembly and Geneva wheel must rotate without restriction in the base. Both axles are 3/8". Therefore I would start with a 13/32" drill bit for the holes in the base. Increase the size as necessary to insure both axles can turn without restriction.
3. When you first get the Geneva wheel and Pin wheel installed, grab the Pin wheel by the Drive pin and rotate it around several times. Make sure the Drive pin easily engages all four slots.
4. You probably will have to sand the outside rim of the Lock wheel and the dip area of the Geneva wheel to make them fit as desired.
5. Sand the inside of the slots on the Geneva wheel to make sure the pin slides easily in and out.
6. Slightly round the ends of the slots in the Geneva wheel to make it easier for the pin to enter.
7. Do not glue the axles on to the Geneva wheel or the Pin wheel/Lock wheel assembly until you are completely done. The 3/8" axles should be a tight pressure fit into the wheels anyway but will allow you to take them apart while you adjust the parts tolerances.
At this point you should be ready to get into the shop and get it done!