How Does a Wheel Mechanically Propel a Car's Chassis?

  • Thread starter Thread starter Curiously interested
  • Start date Start date
  • Tags Tags
    Chassis
Click For Summary

Discussion Overview

The discussion centers around the mechanical principles of how a wheel propels a car's chassis, exploring the interactions between the wheel, axle, suspension, and chassis. Participants examine the mechanics involved in both powered and non-powered scenarios, including comparisons to bicycles and various axle designs.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant explains that a rotating wheel generates torque, and the static friction with the ground propels the tire forward, but questions how the wheel drags the chassis along with it.
  • Another participant suggests visualizing a locomotive wheel to understand the mechanics, stating that the attachment of wheels to the chassis affects motion characteristics.
  • A different viewpoint details the sequence of forces: the wheel pushes the axle, which pushes the bearing, leading to the suspension pushing the chassis.
  • One participant notes that in a non-powered bicycle, the chassis pushes the bearing, which then pushes the axle and wheel, contrasting with powered vehicles.
  • There is a discussion about the nature of CV axles in cars, with one participant proposing a scenario where turning the wheels by hand would still result in the hub/bearing assembly pushing the chassis through the suspension components.
  • Another participant reinforces the previous point, emphasizing that the axle's connection to the wheel and bearing is crucial for understanding the mechanics involved, regardless of axle design.

Areas of Agreement / Disagreement

Participants express various viewpoints on the mechanics of wheel propulsion, with no clear consensus reached. Some participants agree on the sequence of force transmission, while others raise questions about specific mechanics and scenarios.

Contextual Notes

Participants discuss different axle designs, including CV axles and solid axles, and their implications for force transmission. There are also references to how suspension systems affect the mechanics during acceleration and braking, but these aspects remain unresolved.

Curiously interested
Messages
2
Reaction score
0
I understand the basis behind the idea that a rotating wheel driven by an engine will generate torque and the static friction of the ground will push opposite to its direction forcing the tire to go forward. However, I can't seem to understand how the wheel can drag the chassis with it. Does the middle of the tire, which will follow a linear path if the tire rotates and drives along, push the wishbone? Is it the cv axle that push anything?because on a bicycle, when the tire rolls in front, the center of it, which follows a linear path, pushes the bike chassis. How does it work for a FWD car with suspension then?
 
Engineering news on Phys.org
If the wheel did not drag the chassis behind it - what would happen?

It may help your imagination to think about a locomotive wheel - solid steel - so no concerns about tires etc.

You seem to be able to follow what happens with a bicycle - it is exactly the same with a car with suspension except that the suspension springs change length during acceleration and braking. The wheels are attached to the chassis - how they are attached changes the characteristic of the motion.
 
The wheel pushes the axle, the axle pushes the bearing, the bearing pushes the suspension (upright & wishbone), the suspension pushes the chassis.

If there are no suspension, then the bearing pushes the chassis directly.

On your (non-powered) bicycle front wheel example, it's the opposite:

The chassis pushes the bearing, the bearing pushes the axle and the axle pushes the wheel. The tire-road friction causes the front wheel to roll as it moves forward.

On some non-powered wheel designs, the axle is fixed and the bearing is inside the wheel, such that:

The chassis pushes the axle, the axle pushes the bearing and the bearing pushes the wheel.
 
Cars don't have solid straight axles but cv axles (they bend). So my take is, if we take them off and turn the wheels with our hands instead of the engine, the hub/bearing assembly will push the knuckles which will push the wishbones and then the chassis.
Logical?
 
Curiously interested said:
Cars don't have solid straight axles but cv axles (they bend). So my take is, if we take them off and turn the wheels with our hands instead of the engine, the hub/bearing assembly will push the knuckles which will push the wishbones and then the chassis.
Logical?
Not only logical, that is what happen and what I described. The part of the CV axle that goes within the hub/bearing assembly is what I refer as the "axle". No matter the design, there must be a part of the axle that is connected to the wheel (to allow rotation) and another part of the axle that is connected to a bearing (to support the lateral forces); CV joints or solid axle.

Here is a solid live axle:

GM_14_bolt_9.5_diagram.jpg


The axle (23) pushes on the bearing (20), the bearing (20) pushes on the differential casing which is actually part of the suspension.

Here is one for an independent suspension:

Suspension_UprightDriven.png


The axle (green) pushes on the bearings (orange), the bearings (orange) push the upright (yellow) that is part of the suspension.

Here is a more complex one for a front live axle that incorporate steering and a locking/unlocking feature:

60king.jpg

The "rotating" axle (21) goes through the "fixed" axle (60) and connects to the disc brake (67) via the locking/unlocking mechanism (70-76). The disc brake (67) pushes on the bearings (66 & 69) which in turn push on the "fixed" axle (60). The "fixed" axle is solidly linked to the differential casing and steering mechanism.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
Replies
13
Views
4K
  • · Replies 18 ·
Replies
18
Views
8K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
36
Views
12K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 73 ·
3
Replies
73
Views
11K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
4K