In-wheel Suspension: A New Look

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In summary, this suspension within a wheel looks really nice, but there are some issues with the weight and geometry. It would seem that this design has potential, but more research needs to be done before it can be implemented into a real bike.
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This suspension within a wheel looks really nice (source):
 
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  • #2
There was a thread recently where another poster was trying to figure something like this out. I'll see if I can find it.

Obvious issue with this design is the penalty in unsprung weight, it would seem...?
 
  • #3
Oops, that thread was about putting the whole motor inside the wheels...
some bloke said:
Summary: a central motor, inside the wheel, fixed to the frame. the wheel goes around the outside, but can also move up and down for suspension purposes. how best to transfer the drive?

I'm brainstorming how to make an electric motorbike, making as much use of the available space as possible to allow for as many batteries to be fitted as possible.

Batteries aren't relevant right now; my focus is on the final drive at the back of the bike.

To maximise space, I want to fit the motor inside the rear wheel - this seemed the sensible place for it, it's already round and it's where the drive needs to go. it also means one less chain / transmission to worry about, and can help make the overall look of the bike a lot cleaner.
 
  • #4
berkeman said:
Obvious issue with this design is the penalty in unsprung weight, it would seem...?
And maybe the main issue would be the increased wheel weight and MOI, as opposed to unsprung weight. Accelerating that puppy is going to take some extra work!
 
  • #5
I agree that it looks nice. But it is hard to believe that it hasn't been tried before. Maybe you could find earlier attempts or even patent applications.
 
  • #6
berkeman said:
And maybe the main issue would be the increased wheel weight and MOI, as opposed to unsprung weight. Accelerating that puppy is going to take some extra work!
That may not be a big deal for all users. Lots of us like to ride slowly. In developed areas, the bumps at curb cuts and sidewalk seams are an annoyance.
 
  • #7
berkeman said:
Obvious issue with this design is the penalty in unsprung weight, it would seem...?
berkeman said:
And maybe the main issue would be the increased wheel weight and MOI, as opposed to unsprung weight. Accelerating that puppy is going to take some extra work!
As for the unsprung weight it's quite the opposite, it's at its minimal value (the rim and tire).

But I didn't think about the MOI and that is certainly a negative factor.

What I find also interesting is that the suspension geometry affects only the vertical motion, which is what it is supposed to do (no toe, camber, caster change or tire scrub as it moves up & down). But it might also become problematic to handle lateral forces in extreme cases.
 
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  • #8
Also, the suspension components are cycling constantly due to vehicle weight, even when rolling on a flat surface. Sounds like a lot of extra wear and tear.
 
  • #9
sandy stone said:
Also, the suspension components are cycling constantly due to vehicle weight, even when rolling on a flat surface. Sounds like a lot of extra wear and tear.
Now that's an interesting point. If they cycle and dissipate heat constantly, then it becomes more like an exercise bike.

Nevertheless, I still think that a class of users including wheelchair users and old folks who ride slow but who worry about curb cuts and broken sidewalks, that might value shock absorption more than bicycle efficiency or acceleration. For example, the wheel moving to absorb a 4cm bump with little or no vertical motion in the bike's frame.

It is a niche market, so the value of the idea should be judged in that context.
 
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  • #10
Typical, it looks like there's a solution to my problem and I can't view it because it links through faceache! I'll have to have a look when I get home from work...
 
  • #11
jack action said:
As for the unsprung weight it's quite the opposite, it's at its minimal value (the rim and tire).

But I didn't think about the MOI and that is certainly a negative factor.

What I find also interesting is that the suspension geometry affects only the vertical motion, which is what it is supposed to do (no toe, camber, caster change or tire scrub as it moves up & down). But it might also become problematic to handle lateral forces in extreme cases.

I think that it does change caster. When the suspension compresses, the effective radius of the wheel is reduced (assuming compression due to a bump at 6:00). The center of rotation (hub) and the center of curvature (wheel) aren't the same (until the suspension recovers).
 
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1. What is in-wheel suspension?

In-wheel suspension is a type of suspension system that is integrated into the wheels of a vehicle. This means that the shock absorbers, springs, and other components are located inside the wheel itself, rather than being attached to the chassis of the vehicle.

2. What are the benefits of in-wheel suspension?

In-wheel suspension offers several benefits, including improved handling and stability, reduced weight and unsprung mass, and increased interior space in the vehicle. It also allows for more precise control of each wheel, resulting in better traction and overall performance.

3. How does in-wheel suspension work?

In-wheel suspension typically uses a combination of springs and shock absorbers to absorb the impact of bumps and uneven surfaces. The springs compress and expand as the wheel moves up and down, while the shock absorbers dampen the movement to provide a smoother ride.

4. Is in-wheel suspension a new concept?

In-wheel suspension has been around for several decades, but it has recently gained more attention as electric vehicles become more popular. In-wheel suspension is often used in electric vehicles because it allows for more space for batteries and other components.

5. Are there any drawbacks to in-wheel suspension?

While in-wheel suspension offers many benefits, there are also some potential drawbacks. It can be more complex and expensive to design and maintain, and it may not be suitable for all types of vehicles or terrains. Additionally, the added weight of the suspension components in the wheels can affect fuel efficiency.

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