Starting from scratch - What would a MTB look like?
Comments
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mrmonkfinger wrote:MacAndCheese wrote:Why do people make bikes with the bb/cranks on the swing arm?! So pointless like suspension seatposts, who attacks a rough section of trail and thinks "I'm going to sit down for this"??! Suspension has to work when your standing on the pedals!
Massive, massive fail, in comic fashion.MacAndCheese wrote:but there's nothing to isolate bumps between the rear wheel and the pedals so I just can't see it being that great
Oh no, you've done it again.
Look, the entire swingarm rotates around the bottom bracket*. Thus providing a fairly standard suspension. Some kind forum member even provided a link where you could read all about it.
* very very very nearly
Look at the video in the link, no pivot around the BB?Santa Cruz Chameleon
Orange Alpine 1600 -
mrmonkfinger wrote:Look, the entire swingarm rotates around the bottom bracket*. Thus providing a fairly standard suspension. Some kind forum member even provided a link where you could read all about it.
* very very very nearly
EXCEPT... you're standing ON the swingarm, basically. Your feet are on the unsprung mass.
Aaaand, besides, there's no actual advantage to pivoting at the BB.0 -
Been thinking about this further over lunch, I think you/the manufacturer is trying to say it will work similar to this (NS soda slope, solves the singlespeed problem by pivoting around the BB):
but the BIG difference, and the reason I think it will be a bit rubbish, is that on a normal bike(like the Soda) the riders weight is part of the sprung mass, where as on this design it's part of the unsprung mass. I think it might work ok if the rider keeps his weight forward and over the bars, which is probably why the first bike has such a stupidly long stem.
I'd still like to ride it and be proved wrong, but I just can't see it.Santa Cruz Chameleon
Orange Alpine 1600 -
Pivoting around the BB doesn;t really solve anything. Sure, it eliminates chain growth, but you sill still get bobbing whilst pedalling, because the rear wheel is trying to accelerate the bike. Also, since the chain is acting on the chainrings and sprocket above the pivot point, it will just encourage more bobbing.MacAndCheese wrote:Been thinking about this further over lunch, I think you/the manufacturer is trying to say it will work similar to this (NS soda slope, solves the singlespeed problem by pivoting around the BB):
Basically, chain growth is needed, to counteract the squatting force.0 -
Yep, there is almost zero anti squat so they bob like mad. Some people like the feel of them due to the little chain growth, but they have largely become obsolete except for single speeds,0
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Sorry, when I said the Soda "solves" the singlespeed problem, I simply meant the issue of chain growth. I guess the only way to really solve it is to use a standard suspension design with something like this:
Anyway, sorry Bails we seem to have gone off topic.Santa Cruz Chameleon
Orange Alpine 1600 -
I can't take you seriously if you don't think that this singlespeed fad is a problem.MacAndCheese wrote:Sorry, when I said the Soda "solves" the singlespeed problem,0 -
YeehaaMcgee wrote:EXCEPT... you're standing ON the swingarm, basically. Your feet are on the unsprung mass.
Aaaand, besides, there's no actual advantage to pivoting at the BB.
Yes, 100% wrong, and I agree. In that order.MacAndCheese wrote:I think you/the manufacturer is trying to say it will work similar to this
100% correct.MacAndCheese wrote:but the BIG difference, and the reason I think it will be a bit rubbish, is that on a normal bike(like the Soda) the riders weight is part of the sprung mass, where as on this design it's part of the unsprung mass.
100% incorrect.0 -
If the swingarm pivots AROUND the bb shell, which is part of the front triangle, then you are not part of the sprung mass.0
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supersonic wrote:If the swingarm pivots AROUND the bb shell, which is part of the front triangle, then you are not part of the sprung mass.
you did more better words than I did 8)0 -
But on the that new design the BB ISN'T part of the front triangle...it on the Swingarm, which is what i was trying to point out and using the Soda to illustrate the difference.Santa Cruz Chameleon
Orange Alpine 1600 -
If the BB presses into the swingarm yes - it looks like it does, but hard to tell at first glance.
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BB = effective pivot = doesn't move = you're not unsprung weight.0
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Only if the bb is part of the swingarm - it does depends where it is located. If in the 'alu' section that we can see, then it is unsprung mass. Hard to tell from the NS blurb, it says the swingarm pivots around the bottom bracket.0
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Sorry sprung mass lol!0
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I'll start again lol.
Pivot around the bottom bracket shell, BB part of the FT = you are sprung.
Bottom bracket part of the rear triangle, and the FRONT triangle pivots around the BB = you are unsprung.0 -
all available now.VWsurfbum wrote:Full suspension circa 140mm,
Remote or electronic controlled lock out
internal hub gearing
mind changing or cadence shifting gears"Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
supersonic wrote:Bottom bracket part of the rear triangle, and the FRONT triangle pivots around the BB = you are unsprung.
Either you moves when the suspension does, or you don't moves.
The rambike custom just has a (rather large) "L" shaped swingarm with the pivot located at the BB. The fact that it achieves this with a four link setup mounted high up near the saddle, is of no matter.
Having a monster sized swingarm does mean a fair amount of unsprung mass, but, the rider ain't part of it.0 -
You can move slightly though ie rotate - the dynamics are certainly different from the other way round. The fact the cranks are on a bearing is one reason - if they were fixed in place then as the rear sus compresses it has to turn the whole assembly around, with your weight on it. So it depends how you load the cranks (will be different on each as pedalling), and the tension in the chain. Unsprung is probably the wrong word to use, but the way the sus will work does change.0
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Yes, it does matter. It matters a great deal - it is THE thing that makes the design a URT (Unified Rear Triangle) bike, because your weight is ON the swingarm.mrmonkfinger wrote:The rambike custom just has a (rather large) "L" shaped swingarm with the pivot located at the BB. The fact that it achieves this with a four link setup mounted high up near the saddle, is of no matter.0 -
As far as I can see, and I may be wrong but, that ram is basically like a marin/whyte with the cranks on the swingarm, so there is no pivot on the BB whatsoever. The Bikerumor interview states its a URT design or atleast in similarity to the cranks and BB on the swingarm. Like I say I might be wrong
It might just be me but how the fark people thought it pivoted around the BB I do not know, its impossible for it to do so 0 -
Which MArin/Whyte had the cranks on the swingarm? I don't recall either of them using a URT design.0
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supersonic wrote:You can move slightly though ie rotate - the dynamics are certainly different from the other way round. The fact the cranks are on a bearing is one reason - if they were fixed in place then as the rear sus compresses it has to turn the whole assembly around, with your weight on it. So it depends how you load the cranks (will be different on each as pedalling), and the tension in the chain. Unsprung is probably the wrong word to use, but the way the sus will work does change.
Providing the wheel is locked relative to the swingarm, then yes. But it isn't, its free to rotate as the swingarm moves.
The rambike doesn't quite have the pivot located on BB, as the links are setup such that the pivot starts off quite high, is on the BB at mid travel, and then moves forward. So it does have some component of motion at the BB but its a far cry from a crap old school URT. Its much more like the GT i-drive setup, but done a bit more neatly (I have no idea how the IC moves on a GT, by the way).
I think we've successfully gone way off thread here!lawman wrote:It might just be me but how the fark people thought it pivoted around the BB I do not know, its impossible for it to do so
Its you, sorry.0 -
Providing the wheel is locked relative to the swingarm, then yes. But it isn't, its free to rotate as the swingarm moves.
The wheel rotates backwards as the sus compresses, so it will depend on the chain forces to how free the movement is. Even on 'zero growth' systems you get the pedals turning backwards depending on the gearing. Coasting I can see the two systems behaving the same in the same gear. Pedalling, it should be a little different. But I'd have to look at linkage to be sure ;-)0 -
Here's an interesting one!
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I'm confused...mrmonkfinger wrote:The rambike doesn't quite have the pivot located on BB...
its a far cry from a crap old school URT.
Is THIS the rambike that you're talking about?
If so, then Yes, it is precisely like an old school URT.
Seriously. There's no shades of grey here, it just is.0 -
I'd describe it as a URT with a virtual pivot!0
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supersonic wrote:I'd describe it as a URT with a virtual pivot!
Exactly this!!!
It cannot pivot around the BB, it pivots on the linkages, not the BB, and for those that say it does, please describe how on earth it does so with no shock or indeed any pivots around the BB?!
Yeehaa, I was implying that the linkages are similar to whytes/marins, but the bb has moved from the front triangle to the swingarm. its a linkage bike, with a virtual pivot with the BB on the swingarm to elimante chain groowth for easy single speeding. It is completely different to the NS soda mentioned, as that is a linkage driven single pivot that happens to have its pivot on the bb for the same reason.0 -
The virtual pivot could be located at the BB.lawman wrote:supersonic wrote:I'd describe it as a URT with a virtual pivot!
Exactly this!!!
It cannot pivot around the BB, it pivots on the linkages, not the BB, and for those that say it does, please describe how on earth it does so with no shock or indeed any pivots around the BB?!
Even so, it's still a URT design.0
