Suspension types in detail (split from: Inmotion V14 16" suspension)

[techyiam]

IMO, it is a great shame that Inmotion did not go with a hydraulic suspension system like the one that was used in the Sherman-S. 

There is still time to change their minds. 🙂

(For electric wheels, I find it so much easier to differentiate the two types of non-linkage suspension types, if the following terms are used:

(1) Hydraulic Suspension   ie. Sherman-S.

(2) Linkageless Slider Suspension    ie. V13.)

[conecones]

1 hour ago, techyiam said:

(For electric wheels, I find it so much easier to differentiate the two types of non-linkage suspension types, if the following terms are used:

(1) Hydraulic Suspension   ie. Sherman-S.

(2) Linkageless Slider Suspension    ie. V13.)

Hydraulic suspension is a confusing way to describe the Sherman-S. It makes more sense to call it fork suspension - then you can differentiate between air-sprung or coil-sprung. A purely hydraulic suspension (without the use of air/coil springs) is a completely different thing altogether. 

For the other types, they are all slider systems as none of the current "linkage" suspensions suspend the wheel on pivots (as done on MTB and MX)- the wheel only moves up/down constrained by sliders. So perhaps you can differentiate them as standard slider suspension and linkage assisted slider suspension. 

[techyiam]

22 minutes ago, conecones said:

Hydraulic suspension is a confusing way to describe the Sherman-S. It makes more sense to call it fork suspension - then you can differentiate between air-sprung or coil-sprung. A purely hydraulic suspension (without the use of air/coil springs) is a completely different thing altogether. 

(1) Coil sprung hydraulic suspension 

(2) Air sprung hydraulic suspension 

In the context of electric wheels, there aren't any confusion. Just like the proper term for a damper or a shock is hydraulic damper and hydraulic shock, respectively. Except now we have hydraulic struts. The damper is built into the strut. And a strut can take bending stresses, whereas a damper can only take axial stresses.

22 minutes ago, conecones said:

For the other types, they are all slider systems as none of the current "linkage" suspensions suspend the wheel on pivots (as done on MTB and MX)- the wheel only moves up/down constrained by sliders. So perhaps you can differentiate them as standard slider suspension and linkage assisted slider suspension. 

For electric wheels, the linkage would always be referred to the set of links that actuate the coil over shock. ie. progressive links.

On an electric wheel, the main sprung weight is primarily the rider on the pedals. Why would you use swing arms or mult-links to attach the pedals to the axle? No one is going to do this for the foreseeable future. 

 

Linkageless slider suspension 

Versus 

Linkage assisted slider suspension

I guess that is the question. 

[meepmeepmayer]

This is a good discussion and warrants its own topical topic. Split off

[InfiniteWheelie]

This has been discussed quite a bit elsewhere on the site. Here's a post I made that sums up what myself and some others have concluded.

 

Edited February 5, 2023 by InfiniteWheelie

[mrelwood]

7 hours ago, techyiam said:

IMO, it is a great shame that Inmotion did not go with a hydraulic suspension system like the one that was used in the Sherman-S.

Instead they went with a hydraulic suspension system like the one that is used in the Master… 

My guess: The thickness of the struts would add too much width to the familiar and comfortable narrow stance Inmotion ergonomics.

7 hours ago, techyiam said:

There is still time to change their minds. 🙂

I’m not sure if I’d ask them to imitate a suspension system that hasn’t been around nearly long enough to form any kind of data on durability. The forces at play on EUCs are very different to MTBs, and we haven’t yet even seen a strut system that would work very robustly. Some ShermS units have additional stiction, and all of them seem to have enough flex or insufficient margins to introduce drag and scratching on the components for example.

 

7 hours ago, techyiam said:

For electric wheels, I find it so much easier to differentiate the two types of non-linkage suspension types, if the following terms are used:

(1) Hydraulic Suspension   ie. Sherman-S.

(2) Linkageless Slider Suspension    ie. V13.)

The problem is that both of them are hydraulic linkageless slider suspension systems… 

How about we instead use the terms that differentiate the systems from one another?

 Coil strut, air rail, air rail damperless, linkage coil-over, and linkage air suspension system. All of these leave no question of which system one is talking about.

[Tawpie]

Sneaking the word "hydraulic" into the Sherman-S's marketing hype was a good move... it's not inaccurate and it sounds fancier than 'air'.

The purpose of the linkage designs is two fold: 1) you can play with the wheel travel for a given damper stroke, and 2) you have an easier time establishing the leverage curve because the computations are reduced to arithmetic

The choice of the damper's working fluid will require different considerations during the overall design but air and oil are performing the same function—the valving of the working fluid as it moves between chambers allows one to control the rate of damper movement which in turn controls the rate of wheel movement.

Can a fork style suspension work fantastically and be robust? Sure! I think the space restrictions make the design more challenging and compromises the designer's ability to add progressive stiffness via mechanical bits, but it's certainly possible and MTB bikes have been running them for decades now.

Is fork style 'better'? I don't know, it's a little (and I mean a small amount) simpler. Linkages give you freedom of space, you can put parts out of the line of travel where you can fit bigger doodads. But to me the biggest benefit of link suspensions is that they allow modification—links and dampers can be changed to suit the rider. This is really difficult with the fork style.

Is a coil lifter 'better' than an air one? It is in the sense of set-it-and-forget-it. Not so much if you loan your wheel out to riders that vary in weight.

Personally I prefer coil with links. Coil for set-and-forget, links because sometimes the designer might have tuned the suspension for something I don't like as much (looking at you Master) and it would be nice to have the option to change.

[techyiam]

4 hours ago, mrelwood said:

Instead they went with a hydraulic suspension system like the one that is used in the Master… 

If that is how you choose to define it.

It is implied that you would not to call the V11 suspension a hydraulic suspension because it doesn't have a hydraulic damper.

And you choose to call any suspension a hydraulic suspension because it has a hydraulic damper.

I don't call these types of suspensions hydraulic because they don't have a hydraulic suspension (hydraulic strut).

4 hours ago, mrelwood said:

My guess: The thickness of the struts would add too much width to the familiar and comfortable narrow stance Inmotion ergonomics.

So far, I haven't heard of any Sherman S owners complaining about the width of the Sherman S being too wide.

Personally, when I rode the Sherman S and the V13 back to back, I didn't find either too wide.

My first impression was that both the Sherman S and V13 were on a whole different level of refinement and smoothness.

4 hours ago, mrelwood said:

I’m not sure if I’d ask them to imitate a suspension system that hasn’t been around nearly long enough to form any kind of data on durability. The forces at play on EUCs are very different to MTBs, and we haven’t yet even seen a strut system that would work very robustly. Some ShermS units have additional stiction, and all of them seem to have enough flex or insufficient margins to introduce drag and scratching on the components for example.

The bending stresses on a downhill or free ride mtb front suspension fork is tremendous due to its length and cantilever nature. Check out their extreme usage at Red Bull Rampage. The drops, jumps, and hucks are on a whole different level.

The design of the front suspension fork is tried and true in a much more stressful operating environment. The developed technology already exist for a much more gruesome application. 

The stresses exerted on the suspension of Sherman S is considerable less than the stresses exerted on the front suspension fork of a downhill mtb.

 

(1) Electric Wheels with Hydraulic Suspension:    Sherman S, Commander Pro, Sherman S 16"?

(2) Electric Wheels with Slider Suspension:           S18, S22, V11, V13, Hero, EX20S, Master, T4, Master Pro, EX30, V14?

[techyiam]

2 hours ago, Tawpie said:

The choice of the damper's working fluid will require different considerations during the overall design but air and oil are performing the same function—the valving of the working fluid as it moves between chambers allows one to control the rate of damper movement which in turn controls the rate of wheel movement.

Many EE students don't like it, but isn't Fluid Mechanics a compulsory course in the EE curriculum? It's only been 40+ years. 🙂

A fluid can be a liquid or a gas as defined in a branch of physics called Fluid Mechanics. 

A liquid is not compressible.

A gas is compressible. 

A damper is speed sensitive because an oil, a liquid, is pushed through an orifice by a piston in a cylinder. And under the same force, the speed of the piston would be dependent on the viscosity of the oil.

What would happen to the behavior of a damper if the fluid is a compressible fluid such as a gas like air?

An air spring is essentially a sac filled with a compressible fluid, like air. For obvious reasons no liquid springs were ever made.

 

[mrelwood]

58 minutes ago, techyiam said:

It is implied that you would not to call the V11 suspension a hydraulic suspension because it doesn't have a hydraulic damper.

Correct. Since the damper is the only part on an EUC that has any liquid in it, disregarding regular lubing of course.

58 minutes ago, techyiam said:

And you choose to call any suspension a hydraulic suspension because it has a hydraulic damper.

If it has one, yes. Can’t figure out any other meaningful uses for the word hydraulic in EUCs.

58 minutes ago, techyiam said:

I don't call these types of suspensions hydraulic because they don't have a hydraulic suspension (hydraulic strut).

And what exactly makes the strut hydraulic in your mind?

58 minutes ago, techyiam said:

So far, I haven't heard of any Sherman S owners complaining about the width of the Sherman S being too wide.

Sure, but I would think that Inmotion has their own reference point of a wheel being too wide.

58 minutes ago, techyiam said:

The stresses exerted on the suspension of Sherman S is considerable less than the stresses exerted on the front suspension fork of a downhill mtb.

You are probably right. Though I was thinking more like ordinary riding situations, not high speed off-road racing.

58 minutes ago, techyiam said:

(1) Electric Wheels with Hydraulic Suspension:

Sherman S, Commander Pro, Sherman S 16, S18, S22, V13, Hero, EX20S, Master, T4, Master Pro, EX30, V14.

58 minutes ago, techyiam said:

(2) Electric Wheels with Slider Suspension:

Sherman S, Commander Pro, Sherman S 16, S18, S22, V11, V13, Hero, EX20S, Master, T4, Master Pro, EX30, V14.

[techyiam]

5 minutes ago, mrelwood said:

And what exactly makes the strut hydraulic

There is your problem. 

[mrelwood]

2 minutes ago, techyiam said:

There is your problem. 

I’m not following.

I take it that you are not interested in explaining your choice of naming the suspension types. That’s ok.

[techyiam]

7 hours ago, techyiam said:

And you choose to call any suspension a hydraulic suspension because it has a hydraulic damper.

6 hours ago, mrelwood said:

If it has one, yes. Can’t figure out any other meaningful uses for the word hydraulic in EUCs

 

Do air suspensions not use a hydraulic dampers

Of course they do, but yet they are called air suspension. 

Vehicle history has shown that not all suspension systems are called hydraulic suspension just because they use a hydraulic damper.

For electric wheels, the hydraulic struts themselves make up the whole suspension. And thus, the suspension on Sherman S can be appropriately labeled as a hydraulic suspension. 

It seems your mind is full, so further or repeating explanations would be futile

[techyiam]

On 2/5/2023 at 7:08 AM, Tawpie said:

Sneaking the word "hydraulic" into the Sherman-S's marketing hype was a good move... it's not inaccurate

From my perspective, I think it is more than that.

The Sherman-S uses a pair of hydraulic struts, which are sealed from the elements, and the telescoping mechanism are lubricated by oil.

Currently in the electric wheel world, sliders are not lubricated by oil and are often not sealed.

I am giving Leaper Kim and FastAce credit because they did do a good job. Their suspension is class leading, and they have raised the bar.

Edited February 6, 2023 by techyiam

[InfiniteWheelie]

42 minutes ago, techyiam said:

Do air suspensions not use a hydraulic dampers

Of course they do, but yet they are called air suspension. 

Vehicle history has shown that not all suspension systems are called hydraulic suspension just because they use a hydraulic damper.

For electric wheels, the hydraulic struts themselves make up the whole suspension. And thus, the suspension on Sherman S can be appropriately labeled as a hydraulic suspension. 

I think this is where you're misunderstanding...

Wheels like the Sherman-S or S22 DO NOT use an entirely hydraulic suspension... They use a steel spring instead of an air spring. The hydraulic part is only for damping.

Edited February 6, 2023 by InfiniteWheelie

[techyiam]

14 minutes ago, InfiniteWheelie said:

Wheels like the Sherman-S or S22 DO NOT use an entirely hydraulic suspension...

How are you defining hydraulic suspension for an electric wheel?

Also, by my definition, I don't consider the S22 as having a hydraulic suspension. 

Are you completely dismissing the idea of a hydraulic strut?

Edited February 6, 2023 by techyiam

[InfiniteWheelie]

@techyiam I'm not the most knowledgeable person on suspension. I've been trying to learn for the purpose of understanding e-wheels. 

That said, is "strut" even a term used in motorcycle or bicycle suspension? I think I've only only heard it in relation to cars. I'll have to research that more.

Edited February 6, 2023 by InfiniteWheelie

[soulson]

From what I understand—I don't own one—both of the suspension components on the Sherman S are actually struts.

A quick explanation might help. A suspension typically has two purposes: first, it must absorb energy, and second, it must dissipate that energy. Most suspension implementations use the two separate mechanical components for these two independent tasks.

A spring is used to absorb energy. In the V13, this first component is an air spring. In the Master and Sherman S, it's a coil spring. Either way, it does the same thing – it absorbs the energy from an impact. Now, if we just left things there and called it a day, like on the V11, the sprung mass (you) would oscillate or feel "springy", because all of that energy absorbed by the spring would pop right back out a moment later like a bouncing basketball.

To prevent "springiness", most suspensions also include a second component designed to dissipate mechanical energy. This second component is called a damper or a dashpot. They most often work by squeezing a viscous liquid through a small, sometimes adjustable orifice, which converts mechanical energy into heat, damping the oscillating spring.

A strut is a composite component made of both a spring and a damper. The V11 only has springs. The V13 has springs and dampers, but it doesn't have struts. The Sherman S has struts.

[InfiniteWheelie]

@soulsonAccording to your definition, why doesn't the V13 have struts?

[soulson]

I can take out the V13's damper and spring independently and hold them in my hand. It's not a very technical definition

[InfiniteWheelie]

So the V13 has them the spring and damper in separate tubes, whereas the Sherman S has them in the same tube...

Either way I don't see how @techyiam's definition makes sense. If a strut means the spring and damper combined, "hydraulic" still just describes the damping, The spring is either coil or air.

Edited February 6, 2023 by InfiniteWheelie

[soulson]

Fully hydraulic struts exist, which are single components that combine the absorbing and damping effects into one component by forcing a viscous liquid through an orifice into a chamber with a diaphragm with compressed gas on the other side. As far as I know, struts like this aren't used in any current EUC models.

Lots of EUCs have "hydraulic dampers" though.

[conecones]

If we categorize the wheels based on the functions of the suspension parts, you get this:

Sherman-S, S22:
Coil sprung preload + compression
Oil damped compression + rebound

S18, Hero, Master, V13:
Air sprung preload + compression
Oil damped compression + rebound

V11:
Air sprung compression + rebound, no dampening

With the exception of the V11 where there is no oil dampening, I don't really see where the term "hydraulic" can be use to differentiate the Sherman-S suspension. Having the spring & dampers within the suspension "strut" just makes it a fork does it not? 

I've see this same confusing "hydraulic" suspension term being used in MTB circles, where people would call a coil-sprung fork "hydraulic suspension" and an air-spring fork "air suspension", even though both use the same oil (aka hydraulic) dampening...

[soulson]

5 minutes ago, conecones said:

Having the spring & dampers within the suspension "strut" just makes it a fork does it not? 

I've see this same confusing "hydraulic" suspension term being used in MTB circles, where people would call a coil-sprung fork "hydraulic suspension" and an air-spring fork "air suspension", even though both use the same oil (aka hydraulic) dampening...

I would hesitate to call the Sherman S suspension a "fork" because the two struts are not mechanically linked with a cross brace or a triple clamp. Contrast: Commander Pro, which I would say is pretty clearly a fork. This is just my definition though.

Second point, full agree. I wish we could get away from calling these suspensions "hydraulic" as though it is some kind of point of merit. It's like calling my breakfast cereal asbestos-free. (V11 notwithstanding :D)

[InfiniteWheelie]

2 hours ago, soulson said:

I would hesitate to call the Sherman S suspension a "fork" because the two struts are not mechanically linked with a cross brace or a triple clamp. Contrast: Commander Pro, which I would say is pretty clearly a fork. This is just my definition though.

They're still mechanically joined, otherwise each pedal could move independently. Just because The Sherman S uses an inferior and less direct method of joining them, doesn't mean they aren't forks.

Edited February 6, 2023 by InfiniteWheelie