Translation of motion

Question 1

What is a constant velocity joint?

Answer 1

This is a way of translating the direction of motion without changing the speed of the motion

Question 2

What are two methods of 90° constant velocity joints?

Answer 2

Helical or worm gears

Question 3

What is a non-constant velocity joint?

Answer 3

This is a way of translating the direction of motion but causes inconsistant motion speed

Question 4

What are some examples of non-constant velocity joints?

Answer 4

Universal joints

> This allows you to slightly change the drive axis angle.

> The velocity in is not equal to the velocity out unless the input and output shafts are absolutely aligned

Double cardan joint

> This also allows you to change the drive axis angle

> The velocity in is not equal to the velocity out unless the input and output shafts are parallel

Question 5

What are some examples of linear to rotary motion?

Answer 5

> Internal combustion engine

> Steam train

Question 6

What are some examples of rotational to linear motion?

Answer 6

> Oil wells

> Tattoo gun

> Industrial presses

Question 7

How is the displacement of the linear part calculated? [Picture15]

Answer 7

θ = sin^-1⁡( h / C )

ϕ = sin^-1⁡( h / R )

ϕ = sin^-1⁡( Csin(θ) / R )

D_C = Ccos(θ)

D_R = Rcos(ϕ)

D_C + D_R = Ccos(θ) + Rcos(ϕ)

Question 8

What is the equation for the maximum displacement for: [Picture15]

Answer 8

D = 2 × C

Question 9

What is the relationship for ϕ and the ratio of R:C? [Picture15]

Answer 9

ϕ becomes smaller as the ratio of R:C increases

Question 10

What is the efficiency calculation in terms of ϕ for the mechanism [Picture16]

Answer 10

% Efficient = F_Useful / (F_Useful + F_Wasted) × 100

% Efficient = FCos(ϕ) / (FCos(ϕ) + FSin(ϕ)) × 100

% Efficient = Cos(ϕ) / (Cos(ϕ) + Sin(ϕ)) × 100

% Efficient = 1 / (1 + Sinϕ / Cosϕ) × 100

% Efficient = 1 / (1 + tan⁡(ϕ)) × 100

Question 11

For the mechanism, when is the efficiency the worst?

Answer 11

When the rod is perpendicular to the crank.

Question 12

How does vibration occur?

Answer 12

> When the centre of mass does not coincide with the axis of rotation.

> When there is eccentricity between the centre of mass and axis of rotation.

Question 13

What is the equation for central fugal force?

Answer 13

F_CF = meω²

> m = mass

> e = eccentricity

> ω = Angular velocity

Question 14

What are the negative effects of vibration?

Answer 14

> Increased bearing wear

> Noise

> Heat

> Material fatigue

> Decreased resolution in precision systems

> Potential physical discomfort

> Passive transmission to other systems

Question 15

What are the positive effects of vibration?

Answer 15

> Informative physical feedback

> Controlled agitation

• Pile drivers
• Physiotherapy

Question 16

How can we have eccentric rotation without vibration?

Answer 16

We can have eccentric motion without vibration. As long as the centre of mass remains around the centre of rotation.

Question 17

What can change the balance in mass?

Answer 17

> Erosion

> Build-up of contaminants

> Poor castings with air pockets

> Bearing wear

> Loss of balancing components