Print PDF
Favorite
Email
My niece Sydney needed help for a 7th grade Science Fair project. I helped another friend's daughter (Kaitlin) build an articulated hand for a project in the past and suggested we resurrect the project. The build is fun for the kids and I wanted to try some enhancements on the original idea.
Remove these ads by
Signing UpStep 1Materials, Tools & Time
Materials:
You can get everything you need at Lowe's or Home Depot.
1 - 3/4" hardwood dowel
1- 4" x 1" Pine plank (I'm calling it '1x4' here)
5 - bags of #216-1/2 small screw eyes (eyelets)
1 - roll of braided nylon string (one color for ligaments. We used yellow)
1 - roll of braided nylon string (another color for tendons. We used pink)
1 - bag of 1/4" wide rubber bands (like the Post Office uses)
1 - cup hook (open eyelet)
1 - can of white spray paint
2 - 3/4" sheet rock screws
Tools:
Various hand tools (you already have them if you are a maker! :)
We used a small drill press, 4" side grinder, jig saw (my Dad taught me this was called a "Saber saw") and a chop saw with a trim blade. These are time savers, but you could do it all with hand tools if you can spend the time.
Time:
Assuming you have the power tools, you should be able to easily build a hand in about 8-10 hours. That includes taking time to teach your young experimenter how to safely use tools.
You can get everything you need at Lowe's or Home Depot.
1 - 3/4" hardwood dowel
1- 4" x 1" Pine plank (I'm calling it '1x4' here)
5 - bags of #216-1/2 small screw eyes (eyelets)
1 - roll of braided nylon string (one color for ligaments. We used yellow)
1 - roll of braided nylon string (another color for tendons. We used pink)
1 - bag of 1/4" wide rubber bands (like the Post Office uses)
1 - cup hook (open eyelet)
1 - can of white spray paint
2 - 3/4" sheet rock screws
Tools:
Various hand tools (you already have them if you are a maker! :)
We used a small drill press, 4" side grinder, jig saw (my Dad taught me this was called a "Saber saw") and a chop saw with a trim blade. These are time savers, but you could do it all with hand tools if you can spend the time.
Time:
Assuming you have the power tools, you should be able to easily build a hand in about 8-10 hours. That includes taking time to teach your young experimenter how to safely use tools.
| « Previous Step | Download PDFView All Steps | Next Step » |
It looks so professional and just amazing!!!!=)
So I'm in seventh grade too and our teacher just assigned this as our next big project. Needless to say, I was pretty nervous; as the way he explained it it seemed very hard. So I went online to look for some ideas and plans, and I found this lovely design. I feel so much better, it doesn't look as hard as I imagined, although I may be underestimating its difficulty. Thank You so much, I intend to use this for the project, and (with any luck) get an A! Although this is a great design, I think I'll put a little spin on it.... do something extra or crazy like I'm always doing =) Anywhooo.... Thanks again. Thank You Thank You Thank You!!! =)
But we didn't make different segment sizes for different fingers. You could do it, but it would be a lot more trouble to get all the right ones in the right places. So in the end we just made all our joint segments the same length - 1 1/4".
Good luck and I hope this helps...
That is fantastic! Thanks so much for letting me know. I'm really glad our ideas helped inspire you. Good luck!
The conduit idea is a good one. I'm not sure if you mean metal or plastic conduit. Since your tools are limited maybe you should consider using that blue plastic conduit (some people call it smurf tubing). It is cheap (at Home Depot) and easy to cut with a hacksaw. If you cut a triangle out of it where where the joints go it might bend like a finger. You would have to cut it almost all the way through leaving a small piece of the plastic at the top/knuckle.
My concern is that the plastic might be too stiff and/or brittle. It might bend a few times then break. You could experiment with the same kind of idea on different types of materials. Try some rubber and plastic hose - also cheap at Home Depot.. An old water hose might even work. It would have to be a soft one though. 1/2" PVC water pipe is easy to work too. It won't bend like a hinge but maybe you can work out a plan for that. Cardboard or even rolled up and glued paper could work too.
If leaving a small bit of plastic or rubber at the knuckle doesn't make a good hinge, you could consider cutting your triangle all the way through and separating the fingers at the knuckles. Then drill/poke a couple of holes maybe 1/4"-3/8" apart where the knuckle would be. You could basically stitch the 2 finger segments together at the knuckle with a couple of pieces of stiff wire (like 12 ga house wire) or even some tywraps. The idea here is to make a hinge that moves easily. You could also try gluing a strip of fabric (blue jean denim?) along the top of the finger segments to make a hinge. Just leave the glue out of the bendy parts.
The next challange is how to run the strings to operate the fingers. The thinge we found is that you must have the strings at the far edges (top and bottom) of the fingers for them to have enough leverage to move the fingers. So the strings need to run along the top of the fingers (back of the hand) and you have to work out a way to keep them from sliding off when the fingers bend. The wooden version allowed us to screw in eyelets. But you can't really do that with a rubber or plastice finger. Maybe you can bend part your finger joint hinge wire to not only act as a hinge, but also stick up a bit and make a loop for the top string to thread through. If you used fabric for the hinge you could stitch (needle and thread) some kind of bead (check the beading store) to the fabric and leave enough room in the hole for the tendon string to fed through and slide easily.
The strings on the palm of the hand also need to be near the skin surface. You could get some small, stiff plastic hose and tywrap it inside each finger segment. Put them where they are against the palm side of the fingers. You could poke 2 holes at each end of the finger segment and thread tywraps through the hole, then around the thin hose and back out the other hole. Do this at each end of each finger segment and you have a path for your palm side strings/tendons. The trick will be to get these small tubes to all line up properly so your string doesn't bind. It might not be a problem if your hinge is loose enough to allow a little wiggle in the joints.
These are just some ideas to get you started. I would like to see someone put a workable hand design together that would be easy to build with hand tools (get it - "hand" tools :) OK, that was lame. Anyway - good luck with your experiments and don't get discouraged. If you come up with something you like please share a picture with us.
- Robert
- instead of rubber bands use surgical tubing
- make a latex hand mold and put it around the hand to make it look more realistic
- make a hand grip so that it follows the movement of your hand
if you actually did some of this it would be pretty cool
Are you thinking about building one? Please share some photos if you do...
yay im doing the hand this years sf it wil be awsome i will let u know if u subscribe
question: how durable is the hand.
Sudgestion: instead of having lines from the tips of the fingers to the rubber bands why not just have the band run from the top of the fingers to back of the hand where your knuckle would be
Re your rubber band suggestion, my final design that wasn't my original idea. But sometimes we have to change on the fly. :) I originally intended to drill the string/ligament holes slightly away from the edge of the finger joint slope (meaning more toward the center of the flat area between each joint. Then I could just put the rubber bands on the ends of the ligament strings and pull them tight to straighten the fingers. I hope that explanation is clear. Sadly it didn’t work out like I expected. Even with my (own) hand pulling the ligament strings tight it would just barely straighten the fingers out. Part of the problem was it is too difficult to get the holes to come out just where you want them. The thin bit drifts as you drill through the length of a finger joint. You start with the hole in the right spot going in, but it often pops out too close to or actually on the sloped surface. So when you pull the ligament tight it doesn’t have enough leverage to pull the fingers straight. The string/lever action is too close to the center of the finger (the fulcrum). So we added the back of the hand tendon strings to move the pull (lever action) further from the fulcrum.