Problem: Inner race can be twisted; Solution: Use two bearings
Problem: the shaft can move freely; Solution: Use shaft collar; If the shaft collar touches the outer race use spacers/ shim/ washer/ inner race spacer/ ball bearing shim
Ball bearings have less friction, plain bearings are cheeper
Can have flanches to keep it in place
Use spring to preload the bearing
Otherwise add a lip into the material
Retaining ring just as good as flanched bearings but cheaper
MDF: thick, repeatability, remains very flat 1/4'' in opposite to plywood
slip fit: 2-4 thousands difference in diameter e.g inner race is 0.250'' then shafts needs to be 0.2500'' - 0.002'' (0,0508mm)
Press fit: doesnt come out expect with a lot of force
Slip fit: can move freely
Interferance: In between press and slip
Do not use a hammer
shaft need to have a chamfer
If shaft doesnt fit: skrewdriver, 400 grid sandpaper, wear googles, use water to cool
threoretical pitch circle / diameter (PD): point of contact
pitch is distance between teeth / distance along a curve not a straight distance
Pitch is also called module in metric
Always use gears of the same pitch
Two types of teeth: Involute, cycloidal
Two gears rigidly attached to each other is called compound gear, is used to have more torque
Plastic gear is cheap but they break easiely
Usually you dont build your compound gear yourself, you use a gear head
Idler: changes direction of rotation or span gaps
Spear gears: internal and external
compound gear: two or more spear gears rigidly coupled
Rack and pinion: Rack is a spear gear that is unwrapped, linear motion
Rack and pinion spacing = PD/2
Two spear gears spacing = (PD1 + PD2) / 2
Mate rack and pinion inside fusion 360 with offset plane at top of rack and distance to pinion center = PD / 2 - PH
Worm and wormgear;
Wormgear extremly compact for high gear reduction; a lot of energy loss because of sliding contact; lowest efficiency gear; not backdrivable means you cant use the output to move the input, another term is self locking; have one tooth
backdrivability is good if power is down and you want to move a sushi robot with a knife back
Worm are long and skinny and has a helix; left-handed and right-handed
E = beta_1 + beta_2; E .. angle between the shaft; beta .. helix angles; typically 45°
Example beta_1 = 45°; beta_2 = 45° means you can put the in 90° angle; take a left and right handed: 45° - 45° = 0°; those you can only put planar to each other
Helical gear; can be monted in an angle; at high speed helical gears are less noisy; at low speed no difference
bevel gear; perpendicular axis; doesnt have to be 1:1; doesnt have to be 90°
miter gear; are a subset of bevel gears; special form of bevel; always 1:1 ratio; always 90° to each other
hearing bone gear; also called double helical; gets rid of axial force between two helical gears
If you need high gear ratio in small space use worm gear; if you don't want the output move the input use worm; If you need offset use worm or helical gear otherwise use bevel gear
Spear gearhead; don't make your own buy them; first gear can be plastic to save money
Planetary gearhead; planet gear; sun gear (the one in the middle); epicyclic gearing: axis of the gears are moving; extreme power density; much more expensive because more parts and higher tolerances
Harmonic gearhead; used in asimo robot
Gear Ration N; friction on the input; will be multiplied by N and inertia will be N²; the higher the gear ration the less back driveable
delrin good gears; expensive
acetal bad gears
Mount gear: hub; hub diameter; bore; press-fit; clamp; set-screw (flat and set-screw); keyed;
Set-screw: pain in the ass; use thread locker to prevent set-screw from vibrating free; don't use without a flat
Clamp: are good; dont need shaft preperation; easy to install; don't vibrate free