#008
Hobson's Joint
Definition
This model shows a Hobson's Joint, otherwise known as a gearless transmission, which transfers rotation over a 90 degree angle. It demonstrates an ingenious simple design with a hypnotic motion. A variation has a flexible joint on each of the rods that can can bend while in motion. It is not widely used today because of improved bevel gear manufacturing. Sadly there is little historical record of the inventor. The main flaws of the design are too much binding friction and wear, but it is easier to construct and makes a fun project.
View in 3D
Display
This model demonstrates a Hobson's joint composed of 6 aluminum rods
Videos
Images
3D Printing
Mechanism in Legos
Reconstructing the Library Display
The library display is composed of
- (1) Custom cut 1/2" plywood panel (400mm x 400mm)
- (6) 6.5mm 6061 Aluminum rod, 300mm long, bent using bending jig around 1.5" guide
- (4) Custom laser cut 1/4" acrylic slotted wheels
- (4) 6mm flange coupling connectors
- (2) 6mm x 200mm stainless steel D-shaft rod
- (1) 12v DC gear motor with 6mm D-shaft output, 30RPM
- (1) 3D printed motor mount
- (4) 6mm Bore 1-Side, 2-Post Pillow Block (24mm Height)
- (4) 2920 Series Steel Set-Screw Collar (6mm Bore) - 2 Pack
- (1) 2302 Series Aluminum, MOD 0.8, Hub Mount Gear (14mm Bore, 100 Tooth)
- (1) 2302 Series Aluminum, MOD 0.8, Hub Mount Gear (14mm Bore, 60 Tooth)
- (2) 1309 Series Sonic Hub (6mm Bore)
- Various M4 screws
Research
- Hobson's Joint
- Elbow Engine
- "You Can Make This Incredible Elbow Engine" Popular Mechanics July 1965 p.166
- Ten Cylinder "Elbow Engine"
- 1989 NASA Engineering Study of the Rotary-Vee Engine Concept
- History of Bricklin-Turner Rotary Vee Engine
- US Patent US5601055A Rotary vee engine with supply piston induction