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Engineering-Bikes > Frames > Flashcards

Frames Flashcards

1
Q

What is the frame ?

A

The main body of a bicycle that is the framework onto which all other components are attached

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2
Q

How is a frame typically composed ?

A

Multiple hollow tubes that are joined together to form s “double-triangle” or “diamond” shape

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3
Q

What are innovators trying to advance most on a bike frame ?

A

The material from which the frame is constructed, even though it is only one of many factors that influences the strength, weight and durability

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4
Q

What are the four primary factors that affect frame materials ?

A
  1. Stiffness
  2. Strength
  3. Fatigue strength
  4. Weight
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5
Q

What is “stiffness” ?

A

The elastic property of the material. Under the same weight a stiff material will bend less than an elastic

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6
Q

How does the “stiffness” of a material affect the ride ?

A

Elastic frames cushion bumps, stiff frames transmit more force of a bump to the rider.

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7
Q

How does the “stiffness” of a material affect the efficiency ?

A

Elastic frames absorb some of the energy generated to move the bike. Cyclists interested in maximizing performance often use stiffer frames because more of the energy is used to move the bike and is therefore more efficient.

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8
Q

Even though different materials affect the “stiffness”, what is the main factor that affects it ?

A

The frames geometry - different diameters and lengths

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9
Q

What is “strength” ?

A

The amount of force required to crack, break or permanently deform a material

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10
Q

What is the “yield strength” ?

A

The point at which the material permanently deforms

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11
Q

What is the “breaking strength” ?

A

The point at which the material breaks

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12
Q

What does the strength influence ?

A

It doesn’t influence the performance or ride but it does determine the “crash worthiness” of the frame - which is how well it can withstand a crash

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13
Q

What is “fatigue strength” ?

A

Over a long time, small stresses from cycling can cause cracks to develop. A materials resistance to this is its “fatigue strength”

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14
Q

When should “fatigue strength” be considered ?

A
  1. If you want to keep the bicycle for a very long time
  2. If the rider is heavier than usual
  3. If you ride your bike hard
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15
Q

What is “weight” ?

A

Weight or more accurately density, is the measure of how much mass the material has per unit volume

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16
Q

When do you notice a difference in weight ?

A

When you do a lot of climbing or need to lift and carry the bike often.

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17
Q

How do designers make the best frames out of different materials ?

A

They make use of each material, tweaking parameters to strike the right balance.

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18
Q

Why are steel frames durable ?

A
  1. Dents or bends in the frame can be hammered out

2. A broken frame can be welded and ridden again

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19
Q

Which metals rust ?

A

Ferrous Metals

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20
Q

Steel is a ferrous metal, what is done to it so that it doesn’t rust on a bike ?

A

They are usually painted or treated which makes them corrosive resistant

21
Q

Would steel frames develop microscopic cracks over time ?

A

No, they are virtually immune to failure from “fatigue strength”

22
Q

How “stiff” are steel frames ?

A

They are relatively elastic compared to aluminium

23
Q

How does steel’s “weight” compare to other materials that are used on bike frames ?

A

They are heavier than most materials, but techniques are used that can reduce it

24
Q

What is a technique used to reduce the weight of a steel frame ?

A

Butting

25
Q

What is “Butting” ?

A

Steel frames can be built with extremely thin walls, but they are then too thin to weld together. Butting is when the frames are thick on the ends so that there is enough material to weld and thin in the middle to reduce weight

26
Q

How does “Butting” reduce weight ?

A

They reduce the amount of material used.

27
Q

What is steel ?

A

An alloy of iron and other elements to designed to improve pure iron.

28
Q

What two types of steel are mainly used in bike frames ?

A
  1. High-Tensile Steel or Carbon Steel

2. ChroMoly Steel

29
Q

Why is carbon steel often used in low range bikes ?

A

It is common and inexpensive

30
Q

What is carbon steel comprised of ?

A

Iron mixed with 0.2% to 2% carbon

31
Q

What is ChroMoly ?

A

A steel alloy composed of many other elements such as Chromium, molybdenum, carbon, silicon, manganese and sulfur.

32
Q

Even though ChroMoly contains chromium, used to make stainless steel, it can still be corroded. Why is this ?

A

There isn’t enough chromium in the alloy. There is only around 1% in ChroMoly but there is 10% in stainless steel

33
Q

Why are ChroMoly frames often lighter than High-Tensile frames ?

A

ChroMoly is usually butted, where as carbon steel frames rarely use the butting technique and instead have thick walls.

34
Q

Why are aluminium frames sometimes considered a better option than steel ?

A
  1. They are less expensive

2. They have a much higher strength-to-weight ratio.

35
Q

What reputation does Aluminium have ? Does it live up to the reputation ?

A

They have a reputation of being significantly lighter than steel. In reality, there is little difference and at the mid-high prices, steel bike frames are often lighter.

36
Q

What type of bike does aluminium suit ?

A

Bikes that are for sprinting or climbing - such as road bikes. Aluminium is “stiff” and can therefore improve handling and acceleration. It wouldn’t be the best choice for mountain bikes because the “stiffness” provides a harsh and rough ride when going over bumps.

37
Q

Are “butted” aluminium frames common ?

A

They can be found, but most are not butted.

38
Q

Although aluminium is corrosion resistant, what can happen to the frame over time ?

A

They are susceptible to “fatigue stress” over time. They are also harder to fix

39
Q

How do aluminium alloys compare to pure aluminium ?

A

They have the same weight and stiffness but the strength varies slightly.

40
Q

What is one of the newest and most exotic materials used for bike frames ?

A

Carbon Fibre

41
Q

What is carbon fibre ?

A

A composite of strands of carbon pressed together in layers with epoxy glue

42
Q

How can carbon fibre improve the aesthetics and performance of the bike frame ?

A

It can be shaped into interesting and aerodynamic shapes

43
Q

What is the most common way carbon fibre is used as a bike frame ?

A

They are composed of teardrop, flat or wing shaped tubes rather than the perfect cylinders

44
Q

How are carbon fibre frames connected ?

A

They are sometimes built as a single piece or induvidual tubes joined together

45
Q

Why is carbon fibre considered the best material for bike frames ?

A

It is very lightweight and can have different amounts of stiffness in different directions. This means it can be stiff for sprinting and springy when going over bumps

46
Q

What is a downside of carbon fibre ?

A

They are by far the most expensive bike frames

47
Q

Is carbon fibre corrosion resistant ?

A

Yes, it isn’t a metal so wont rust. However, they do require more care.

48
Q

What can a deep scratch or hard bump do to a carbon fibre frame ?

A

compromise the structural integrity, making it prone to catastrophic failure.

Engineering-Bikes (6 decks)

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