Acrylic on acrylic hinge - friction?

I'm building an articulated 'puppet' using 3mm acrylic sheet for the 'skeleton'

My hinges will be simple sandwiches of two outer and one inner piece, held together with a snap-together nylon rivet. The flat contact area is about half a square inch (see attached image). The 'puppet' will be controlled by tendons attached to gloves, so will only have the force of single fingers to move them. I need to know how smooth a joint this will be, before I start ordering nylon washers.

Anyone got experience of this sort of join? Will it be ok dry, or will a small amount of  lubrication help? (petroleum jelly? liquid silcone?). Or do I need to commit to washers. Needs to be as frictionless as possible!

Picture of Acrylic on acrylic hinge - friction?
sort by: active | newest | oldest
NachoMahma6 years ago
. Graphite
kelseymh6 years ago
As Kiteman said, acrylic on acrylic will be rather stiff, and will also squeak from the sliding. You should be able to get nylon, or even better PTFE (teflon) washers in any size you need.

My favorite vendor is McMaster-Carr Industrial Supply, but a good hardware store should have them in their aisle of small plastic trays. Here are a couple of suggestions:

http://www.mcmaster.com/#sleeve-bearings/=ajmvui
http://www.mcmaster.com/#washers/=ajmwjj

The sleeve bearings are thicker, and probably more than you need for this application.
Crispy75 (author)  kelseymh6 years ago
Yeah sleeve bearings would be overkill. I think there's some sticky-back PTFE tape in the workshop, I'll have to check next time I'm there.
Crispy75 (author) 6 years ago
Quick thought - I haven't actually ordered materials yet - would a different plastic be more suitable? Polyethylene for example?
Crispy75 (author) 6 years ago
The load should be almost entirely in-plane and the individual segments are 4 inches long max. This skeleton will be surrounded with wadding and then wrapped in a stretch-fit skin, so it'll have lateral support. Thanks for your input, and maybe I'll pop back when I've got some pieces fabricated :)
ynze6 years ago
I think the nylon rivet will do the job for the joint working smooth, as long as the acrylic pieces aren't squeezed together too hard. Don't make the acrylic pieces too narrow. If the load / force on them works in the same direction as the rivet, the acrylic pieces will snap easily.
I have no idea but I can make a guess. From the sounds of it you shouldn't need any lube, as long as the joint has some very little play. If you must use a lube I would suggest useing graphite, but even that may be overkill.
+1

Without a little "play", the joint will not only be stiff, but squeaky.

Crispy75 (author) 6 years ago
Cheers - I suspected as much. I couldn't find a set of washers and rivets that matched in terms of dimensions anyway!