DIY arm model

Make your own functional hand model!

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • 2 plas­tic bot­tles;
  • 2 rulers;
  • 2 bal­loons;
  • bolt;
  • nut;
  • drill;
  • card­board;
  • thread;
  • pa­per straws.

Step-by-step in­struc­tions

Trace your hand and cut the draw­ing out. Use hot glue to at­tach some threads (ten­dons) to the fin­ger­tips and some pieces of straws (bones) to the hand. Pull the “ten­dons” – the hand con­tracts! Make a mus­cle: bore a hole in a bot­tle cap, in­sert a sil­i­cone tube, and tape a bal­loon to the short end of the tube. Make sev­er­al long ver­ti­cal cuts in the plas­tic bot­tle. In­sert the bal­loon into the bot­tle and screw the cap on – the mus­cle is ready! Make a sec­ond one the same way.

Hold two rulers to­geth­er and drill a hole in them. Pull a thread through the ten­don’s lig­a­ment and glue the “hand” to one of the rulers. Make an­oth­er hole in the ruler and pull the thread through it. Fas­ten the rulers with a bolt and nut, and fix the mus­cles to the rulers us­ing zip ties. Con­nect the tubes on the mus­cles with a split­ter and pass the thread from the hand through the bot­tom of the first bot­tle and tie a knot. At­tach the bi­cep to the sec­ond ruler the same way. Blow into the tube, in­flat­ing the bal­loons – the arm bends!

Process de­scrip­tion

As they in­flate, the bal­loons force the bot­tles to widen, which caus­es them to short­en. The “ten­don” at­tached to the bot­tom of the bot­tle pulls the “fore­arm” along! Let the bal­loons de­flate – the arm will un­bend. Hu­man bi­ceps work sim­i­lar­ly: the mus­cle short­ens as it con­tracts, and the ten­don thus pulls the fore­arm up­ward, bend­ing the arm.

More ex­cit­ing ex­per­i­ments are wait­ing for you in the MEL Kids sub­scrip­tion!