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


techyiam

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1 hour ago, InfiniteWheelie said:

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.

A fork has the two legs, a crown and a steering stem.

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11 hours ago, techyiam said:

A fork has the two legs, a crown and a steering stem.

This is hair splitting. They didn’t name it “fork” exactly because it has “two legs, a crown, and a steering stem”. Those are just the particulars of what bicycles/motorcycles happen to require. They named it “fork” because it’s connected up top, and forks out into 2 legs, that’s it.

In e-wheels it still has 2 legs (which aren’t distinct from bikes/motorcycles), and still connects up top with a “crown” of some sort (whether a metal bridge or less direct method).

It think it’s silly not to call them forks just because the mounting hardware is slightly different, and there’s no need for a steering pole.

Edited by InfiniteWheelie
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On 2/5/2023 at 6:36 AM, techyiam said:

And a strut can take bending stresses, whereas a damper can only take axial stresses.

??? A strut and a damper operate in the same plane. I don't understand how one is axial (which it isn't, it's longitudinal) and the other isn't.

On 2/5/2023 at 12:18 PM, mrelwood said:

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

Exactly. Which is why I have no idea that some people are adamant that the Sherman S should be described as 'hydraulic' :)

On 2/5/2023 at 3:08 PM, Tawpie said:

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

True, but unless you are riding at the top end of a race team there really shouldn't be any need to mess about with linkages. Changing them on MTB's is unheard of, unless the original is total crap (like the Master). I'm not dead set against linkages but the system needs to be made right (which no EUC has managed to date) and all that extra weight, complexity and moving parts needs to be beneficial. Most EUC riders wouldn't/shouldn't need to mess with linkages just as 99.9% of MTB riders don't. MTB's use linkages for the same reason as MX bikes (which I gave on the other thread) but as has been proven with the SS, it's not necessary for EUC's.

On 2/5/2023 at 3:08 PM, Tawpie said:

But to me the biggest benefit of link suspensions is that they allow modification—links and dampers can be changed to suit the rider.

You are correct though in that linkage systems allow shock changes easily, and that is indeed a benefit if the stock shock is crap. It it wasn't though...

On 2/5/2023 at 5:17 PM, techyiam said:

(1) Electric Wheels with Hydraulic Suspension:    Sherman S

I think we are all ready to accept that you will keep naming the SS system hydraulic. And honestly, thats cool. It's still wrong though.

19 hours ago, InfiniteWheelie said:

That said, is "strut" even a term used in motorcycle or bicycle suspension?

No it's not. the only time you will hear of the word 'strut' being used is on cars (as you suggest), derived from the original term 'McPherson Strut' who designed the system.

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44 minutes ago, Planemo said:

?? A strut and a damper operate in the same plane. I don't understand how one is axial (which it isn't, it's longitudinal) and the other isn't.

Can you place a coil over shock, or an air shock in place of a strut?

Why and why not?

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The way I see it, a strut is a spring, damper, and a structural component all in one. In that sense calling the ShermS suspension leg a strut does make sense.

22 hours ago, techyiam said:

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

The V11 shock is also sealed from the elements, and it actually has an ample amount of lubricating oil in it. Hence, I shall call the V11 a hydraulic suspension from now on.

 

22 hours ago, techyiam said:

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.

Absolutely, I fully agree! So much so that I think we should call the ShermS suspension a “metallic suspension system” from now on! You know, to differentiate from the other metallic suspension systems.

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3 hours ago, Planemo said:

unless you are riding at the top end of a race team there really shouldn't be any need to mess about with linkages.

oops... yeah, agreed. I meant "as a designer I can play with stroke and wheel travel and leverage curve". Typical end users shouldn't ever 'need' to change a damn thing. But still, Master happened… and it can be salvaged.

 

3 hours ago, Planemo said:

that is indeed a benefit if the stock shock is crap. It it wasn't though...

Even if it wasn't crap, it was meant to cover the needs of the largest majority of riders and maybe I'm an outlier. If my suspension design uses an off-the-shelf damper, I can choose from a broad selection of a very nice, very to very very expensive replacement rear dampers. I mean, I think I'd like high and low speed compression adjustment, and I can get it.

(Well, I can get it, but I won't. Sadly, I'm but a normie, and a pretty tame one at that. Maybe I'd be able to tell the difference? Probably not.)

Edited by Tawpie
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14 hours ago, techyiam said:

Can you place a coil over shock, or an air shock in place of a strut?

Why and why not?

I'm not sure I understand your question. I wasn't talking about replacing anything, merely stating that both a strut and a damper work longitudinally, not axially as you stated.

FWIW, I agree with @mrelwood that the common understanding of a 'strut' is a complete assembly - with a coil spring (over the damper), an integral stub axle and suspension arm/brake caliper mounting points (as per usual McPherson strut, used on the front of many cars). I still wouldn't like to call the SS setup a 'strut' though because it's simply more accurate to call it a telescopic coil fork. Never, ever have I heard anyone call MC forks 'struts'.

And before anyone shouts 'but the SS doesn't have a steerer tube, it can't be a fork!' I would argue that it's still far closer to a fork than a strut and the fact that it doesn't have a steerer is pretty much irrelevant anyway as the two parallel forks are still connected.

In any event I think I'm done with my views on it lol.

12 hours ago, Tawpie said:

oops... yeah, agreed. I meant "as a designer I can play with stroke and wheel travel and leverage curve". Typical end users shouldn't ever 'need' to change a damn thing. But still, Master happened… and it can be salvaged.

I agree, having linkages gives the designer more packaging options for sure (although even thats a bit moot with the limited real estate on an EUC..) But given that any half decent air shock can have the progression altered with tokens and coil shocks can have progressive springs you get most user bases covered without messing with linkages which as I say is why no one in the MTB world does it. The factory linkage setups allow such a broad range of riding styles and rider weights it just isn't necessary. Changing shocks/springs/air pressures/damping yes.

I run my same MTB on gentle forest trails as I do in the Alps of Morzine. All I did for Morzine was add a token and a little more air pressure. The bike is totally unflappable in either scenario and they couldn't be more different.

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Arguing semantics usually doesn't help...

Instead, let's ask the practical questions, when comparing suspension designs:

  1. Where does the spring force come from? 
    For EUC's, thusfar we've only seen air springs, and steel coil springs.
     
  2. Where does the damping force come from? 
    For EUC's, it's either "nowhere" (V11); "one shock absorber" (S18 etc); or "multiple shocks" (Sherm-S etc).
     
  3. What mechanism resists wheel torsion? 
    Lots of variation here: S18 used 4 sliding tubes in bushings; Master T4 etc use 2 sliding tubes in bushings; Sherm-S uses wet struts; V11, V13, S22 use open channel sliders. 
    Sliders are not the only way... e.g.: MTB rear suspension; but EUC wheel linkages haven't appeared yet.
     
  4. How many moving joints are present?
    There will be at least two, from the anti-torsion mechanism. Exactly two, for Sherm-S. More for other wheels- each pivot point of each linkage counts. 
    All of these are potential sources of slop, friction, and wear.
     
  5. What creates the end-stops for the range of motion? 
    Often, rubber "bump-stop" features are integrated in the damper. Sometimes, end-stops are separate components (e.g.: T4 rubber rings). Worst-case, it's from metal-on-metal contact at the end of the slider (Master). 

.02

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On 2/5/2023 at 5:18 AM, mrelwood said:

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

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

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

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.

Simplify:

FIRST:  Mechanical Structure (supporting load and, controlling the path of movement):   A). Telescoping Tube  VS   B).  Linkage     

               examples:  A).  Motorcycle/MTB forks, and ShermanS   VS    B).  Motorcycle (rear) swing-arm, and KS s22

SECOND:  What Suspends the load:     A.   Coil Spring    VS    B.  Compressed Air

             NOTE:  a coil spring may be external/visible (ie - coil-over-damper), or the coil spring may be contained within the supporting structure (ie - typical motorcycle forks)

THIRD:   What Dampens (controls the rate of) movement of the load:   Hydraulic flow and valving

 

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On 2/5/2023 at 5:47 PM, 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. 

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

On automobiles with "air suspension", the "air" is simply used as a spring, as an alternative to a steel coil or leaf spring.  The air component provides no damping.  These vehicles all have separate hydraulic dampers (ie oil filled "shock absorbers").

The only real advantage of air springs in automobiles is that it is simple to alter the vehicles ride height, or firmness of the spring (by adding or removing air).

Hydraulic systems do not do anything to "suspend" or carry the load - that is done by the spring (be it steel or air).  The incorporation of Hydraulics in suspension systems is to control the rate of movement, within the range of movement allowed by the spring (and mechanical structure the spring acts on).

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On 2/6/2023 at 4:07 PM, techyiam said:

Can you place a coil over shock, or an air shock in place of a strut?

Why and why not?

Because the Strut (in a 4 wheeled automotive application) replaces the upper A-Arm (control arm).  The strut is a component of the mechanical structure of the chassis, not simply a sprung damper.

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On 2/14/2023 at 9:12 AM, RagingGrandpa said:

Arguing semantics usually doesn't help...

Instead, let's ask the practical questions, when comparing suspension designs:

  1. Where does the spring force come from? 
    For EUC's, thusfar we've only seen air springs, and steel coil springs.
     
  2. Where does the damping force come from? 
    For EUC's, it's either "nowhere" (V11); "one shock absorber" (S18 etc); or "multiple shocks" (Sherm-S etc).
     
  3. What mechanism resists wheel torsion? 
    Lots of variation here: S18 used 4 sliding tubes in bushings; Master T4 etc use 2 sliding tubes in bushings; Sherm-S uses wet struts; V11, V13, S22 use open channel sliders. 
    Sliders are not the only way... e.g.: MTB rear suspension; but EUC wheel linkages haven't appeared yet.
     
  4. How many moving joints are present?
    There will be at least two, from the anti-torsion mechanism. Exactly two, for Sherm-S. More for other wheels- each pivot point of each linkage counts. 
    All of these are potential sources of slop, friction, and wear.
     
  5. What creates the end-stops for the range of motion? 
    Often, rubber "bump-stop" features are integrated in the damper. Sometimes, end-stops are separate components (e.g.: T4 rubber rings). Worst-case, it's from metal-on-metal contact at the end of the slider (Master). 

.02

Excellent post.  Thanks RG!

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Hi. I'm not an expert on this subject but wanted to raise some questions about what type of suspension-damping system works best. It seems that the one on the s22 is the best in some ways such as dips but does not have the insulation for dust and water enough. The one on the sherman s does have that insulation and performs very well, so it should require less maintenance and be more durable right? I think you have to look at performance, durability-maintenance and light weight. Do you think there is one of the suspension-damping systems that will be standardized because it meets all the characteristics sufficiently? Will it be the sherman s? It looks like Kingsong, Veteran and Inmotion are going to make 16" suspension wheels this year, do you think each brand will continue with their systems or will they copy ideas from each other?

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1 hour ago, Pablocavern said:

It looks like Kingsong, Veteran and Inmotion are going to make 16" suspension wheels this year, do you think each brand will continue with their systems or will they copy ideas from each other?

It really seems like third iterations should combine best parts of each system. We already have good solutions for every task, just not in one package. We also know what the faults are in each system. They are solving same problems that mopeds and downhill bikes have solved years ago. 

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13 hours ago, Pablocavern said:

It looks like Kingsong, Veteran and Inmotion are going to make 16" suspension wheels this year, do you think each brand will continue with their systems or will they copy ideas from each other?

Rumor says that Inmotion is going with the linkage style suspension for the V14.

 The V11 rails were never good for more than relatively peaceful street riding, as otherwise the wear rate, friction and mechanical play were real issues.

 The main issue with the ShermS system in my eyes is the thickness it unavoidably adds to the riding stance. A 4” wheel well, two 2” tubes and 4 layers of panels alone make for 8.5”. My guess is that the comfortable narrow stance is too important for Inmotion to make a ShermS style suspension. Going with sliding tubes and a linkage rear shock shaves 2” from the overall width.

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16 hours ago, Pablocavern said:

It looks like Kingsong, Veteran and Inmotion are going to make 16" suspension wheels this year, do you think each brand will continue with their systems or will they copy ideas from each other?

That is an interesting question and I look forward to seeing what comes out from each company and how well each one works.

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4 minutes ago, Pablocavern said:

which system would you prefer prioritizing reliability, low maintenance and durability although they are good enough performance?

Well, V11 (and probably V13 as well) suspension durability is on the low side, S22 system is dysfunctional by default, and ShermS suspension durability is unknown. So it only leaves the Master style suspension.

I really like Inmotion’s view of riding stature and comfort, so I’m all for narrow wheels, which also leanss towards a linkage monoshock.

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In terms of performance, simplicity, and durability, forks seem to be the obvious winner. The only downside is width.

Linkage monoshocks allow for a thinner wheel which is a very important advantage. For everything else, it comes in a close second to forks.

If you want a wheel to be as thin as possible use a linkage monoshock, otherwise forks are a little better in my opinion. Both can make for a very good suspension.

Edited by InfiniteWheelie
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If over time it turns out that the sherman s forks hold up well while the Inmotion and Kingsong swingarms give a lot more trouble, I guess the forks will win out. On the other hand, on smaller eucs with narrower wheels is it possible that the forks don't widen the set up as much no?

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