Last year, a friend of mine came up with an idea to take 8" Teddy Bears, glue on some skis and snowboards, put them on miniature chairs, and then suspend them overhead to look like they were on a ski lift. They looked great but they didn't move. I thought that a ski lift should move. So this year I decided to take action. And by action I mean hook up a motor and gearset to get these guys moving. Before we get to the instructions on how to make it, take a look at the video of the final product above.
Step 1: Materials
Here is a list of materials you will need to complete the project. Note the dynamic parts are from Actobotics and ordered from Servocity.com...
Materials for building the bears/chairs:
- (8) Bears- I used 8" bears in a sitting position that have custom clothing and ski/snowboard props
- (8) 12" long x 3/4" diameter wooden dowels
- (8) small threaded hooks for attaching to the top of the dowels
- 12' of 3" tall thin molding/paneling to use for the chairs backs/seats
- 3' of .25x.25" square wooden stock for chair armrests
- 16 toothpicks for chair armrests
- Hot glue gun (You can use other adhesive if you would like, glue gun was easiest for me)
Materials for the Pulleys (hyperlinks to servocity.com for Actobotics parts):
- (1) 2'x4'x.5" plywood (I used Oak, but you can use any durable wood or mdf)
- (4) 1/2" Bore Clamping Hub-p/n 545600
- (1) 80tooth, 32P 1/2" bore aluminum gear- p/n 615206 - this is what I used, check gear calcs for your application
- (1) 26RPM, 12VDC, Planetary Gearmotor- p/n 638242 - this is what I used, check gear calcs for your application
- (1) Swivel Clamp Motor Mount- p/n 555140 - Mates with the gearmotor listed above
- (1) 22mm Bore Clamping Swivel Motor Mount- p/n 555148 - Mates with motor mount clamp listed above
- (1) 16 tooth, 32P, 4mm bore Pinion Gear- p/n 615326 - this mates with motor and gear listed above
- (2) 12" long x 1/2" Dia. Aluminum Tubing- p/n 635262
- (1) 24" long Aluminum Channel- p/n 585466 - This channel is awesome due to its many precision drilled holes
- (4) 1/2" Bore Flat bearing mount- p/n 535118 - Matches perfectly with the Al tubing listed above
- (25pack) 6-32 x .3125" long socket head cap screw - p/n 632108
- (25pack) 6-32 x .375" long socket head cap screw- p/n 632110
- (4) fender washers
- (4) "long" 6-32 screws to go through the pulley and clamping hub. I used 2.5" screws.
- (8) hair bands to use for hanging the bears
- (16) 6-32 nuts
- (16) #6 lock washers
- (16) #6 washers
- (1) 50' of paracord to hang the bears
- (1) long steel L-shaped channel for my ceiling mounting, your mounting may differ
- (various) screw/washer/nut setup to connect Aluminum channel to steel channel for mounting
- Total cost for everything is ~$150.
Your mounting may be significantly different than mine so you may need more or less materials to do the mounting. If you are using larger bears, you may need more plywood/molding for the chairs and pulleys. Finally, I used paracord as the hanging medium, you can use other rope or make it longer if wanted.
Step 2: Bears and Chairs
I received the bears from a friend so I am not going to get into the details on how to create them. I can tell you that they are approximately 8" long in a sitting position. You will see in the pictures that each one is clothed differently and they have different sets of skis, ski poles, and snowboards.
The chairs are constructed out of thin molding or paneling. Check the picture for the dimensions and other parts. Based on the size of your bears, your chairs may be adjusted as needed. Note that if the chairs get wider, you will need to adjust the size of your pulleys. Everything is hot glued together. Since this is all wood you may want to use wood glue to make a stronger joint but it will also take longer to dry.
There are 4 chairs with bears and 4 empty chairs. This fits well with the length of my lift which is 18 feet center to center. You can add or subtract depending on your situation. Note that the more bears and chairs the more tension you will need to have on the rope which means more stress on your tubing and mounts. I initially started with 6 chairs with bears but I could not get enough tension in the rope without bending the tubes.
Once the chairs are assembled and the bears are ready, glue the bears to the chairs with the hot glue gun. For my assembly the bears+chairs weigh about 13oz and the empty chairs weigh 4oz. The lighter the assembly the less tension you will need to prevent sagging of the rope.
Step 3: Calculations for Lift Speed
It is important to calculate how fast/slow the skit lift will move. Too fast and the lift will look funny and it may be difficult to keep the bears on the pulleys and they will sway a lot. Too slow and it will look like they are not moving. There are a lot of different ways to solve this problem and there is no single right answer. A lot will depend on what restrictions you have in terms of the following variables:
- Motor RPM
- Gear ratios (pinion gear coming off motor, follower gear on tubing)
- Pulley diameter
- Pulley center to center distance
See above for the calculations that I went through to calculate the speed for my lift. My givens were the diameter of pulleys, the distance between centers, and I wanted a full rotation between 2-3 minutes. Therefore I found a motor and gearset to get meet my constraints.
I initially had concerns about having enough torque to spin the pulleys. Based on my calcs I needed about 30 lbf of tension to hold up the bears/chairs which produced quite a bit of stress on the tubes. However, when I built the unit the bearings from Actobotics were great and torque was never a concern.
Step 4: Pulley Assembly
Creating the pulleys:
- Using a sheet of 2'x4'x.5" oak plywood, draw (2) 12" circles for the inner circles and (4) 14" circles for the outer circles.
- Cut them out using a scroll saw. They will be far from perfect but close enough.
- Drill a small hole through the center and stack up 2 large pieces with a small piece in the center. To align them, stick a screw through the drilled hole.
- Keep them together using wood glue. Don't forget to clamp them while drying. Note that I drilled holes in one pulley to see if it made a difference in the weight. The difference was minimal and made no difference in the final product.
- Once the glue has dried, drill a vertical 1/2" hole that will accommodate the tubing.
Check the pictures for the driver side and the follower side. The parts are listed in the materials section and should be self explanatory along with the pictures. For my assembly I needed to increase the size of the hole on the Al channel where the tubing went through the bearings. This was due to a slight mismatched in the tolerancing of the bearing/mount, the channel hole and the tubing. I increased the hole in the channel to just above 1/2". This is a good thing as you want all the load to be on the bearing and not on the channel where it could score and eventually fail the tubing. If you have a long span and/or a large number of bears, you may want to up the Al tubing to steel tubing for extra strength.
In my design I used a 12VDC motor. To hook it up to an AC outlet, I found an old power adaptor rated at 12VDC output and above the amperage needed to run the motor. I chose a DC motor because I thought I needed a lot of torque. After seeing how smooth the bearings were, next year I will be using an AC motor. AC has lower torque but tend to be quieter than DC motors. My one big failing on this design was a loud motor.
For additional assembly help, check out the video and pause it.
Step 5: Mounting Pulleys and Hanging Bears
Mounting the Pulleys:
If you look at the video, you will see the driver side is mounted underneath an outcropping in my loft and the follower side is mounted across the room on a ledge. I was lucky in that both of these areas are lined with plywood under the stucco. Mounting was a simple task of taking a steel L-shaped channel and using the wood screws to screw into the plywood. I then used one nut/washer/bolt assembly to connect the pulley assembly to the L-Channel. Using one nut/washer/bolt assembly was done on purpose because it allows each side to "float" once the rope is attached and the entire system is under tension. You may not notice in the video, but there is approximately an 18" height difference from one side to the other. This "floating" allows for the tension to hold the rope in the pulley groove.
Attaching the Rope:
If you looked through my calculations, remember the total path was ~40'. I actually used over 42' feet of paracord. to attach the paracord, I used a simple loop knot on one side and a Taut-Line Hitch in the other and adjusted the tension to eliminate any slack. I then ran the assembly for a while to make sure the rope stayed in the pulley groove. Once I was confident the rope would not fall out of the grooves, I move on to hanging the bears/chairs.
Hanging the Bears:
It is important that when hanging the bears you keep each side balanced. If you do not, you run the risk of the weight pulling the rope out of the pulley groove and having a yard sale on your floor. To do this, I divided my total length (470") by the number of bears/chairs (8) coming up with ~59" in between each hanger. I also alternate between bears/chairs and just chairs. Therefore, at any time during rotation I will have 2 bears/chairs and 2 chairs on each side. To hang the bears, I used hair bands tied to the paracord and then hung the chairs on the hair bands. The reason I did this was when I had the chairs mounted directly on the paracord, every once in a while the hook would catch on the pulley causing the rope to come out of the pulley resulting in a yard sale on the floor (this is another reason to use hot glue, when you do have a failure, hot glue dries much faster than other adhesive). The downside of using the hair bands is the chairs tend to rotate and sway. I also tried zip ties. They failed less often than just the hooks, but any failure is catastrophic. The hair bands were successful 100% of the time. I adjusted the tension after hanging 4 items and then adjusted again after the final hangings. I also found that I needed to adjust the tension about once a week, so keep your ladder handy.
There you go! You now have a Teddy Bear Ski Lift!! I hooked my motor up to a remote control so I can activate it from anywhere in the room.
Step 6: Final Thoughts
This project was very satisfying from many perspectives. It turned a good idea into a great idea. Static displays are cool, but dynamic displays are awesome!
For next year, there are a couple of improvements I am looking at:
- The biggest is a switch out of the motor. The DC motor I selected was too loud. As I mentioned the bearing worked great and it does not take much torque to spin them. This means I may need to adjust my gearset. I have already done the calcs once, so it is just a matter of sticking in the RPM of the new motor and getting a new gear reduction number and matching gearset.
- The hair band solution felt like a band aid. I tried several other solutions but only the hair bands gave me 100% success. The problem is that the rope would come out of the groove with the other attachment solutions. The downside of the hair bands are they do not resist rotation. So I need something the conforms to the groove but also resists rotation. I have a year to figure something out.
Thanks for reading and good luck with your project!!!