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Fabien Pedemanaud’s new Bos/Morewood bike.

Rick205

Monkey
Jun 20, 2006
200
0
Kind of strange frame color. I would have chosen something else for marketing purposes but the bike looks fast.

What tires?

Aaaah, you say that but look how many ppl have commented on the color now - maybe that could be the rm rootbeer obsession though :busted:

Awesome looking bike though, cant wait to seen nico's lapierre with all of the boss suspension on :drool:
 

DirtEveryDay

Turbo Monkey
Nov 24, 2003
2,695
4
Pacific North Wet
So who's carrying the BOS stuff yet? I'd like to see some prices. Not to fond of the needle bearing pivots in the rear, though...don't know what's wrong with good ol fashion BRASS.
Oh, and Cream Soda rocks da HOUSE!
 

P.T.W

Monkey
May 6, 2007
600
0
christchurch nz
:drool:
Top bike for a top bloke
I had a brief chat with him when he was racing our national series here in nz last year,realy nice guy an glad he didnt have to sleep on our park benches for too long
 

davep

Turbo Monkey
Jan 7, 2005
3,279
0
seattle
fixed

dirt bikes doesn't seem to suffer much the absence of virtual pivot designs either
Nor do they see changes in the direction of chain torque, or have to deal the same type of low frequency oscillation input (4 to 5 times the mass of the vehicle).

Nor do they have such a limit of input power..etc, etc.


there are lots of reasons that suspension 'effeciency' is much more important in a bicyle chasis than a moto. BTW word on the street is that DW has some sort of new suspension design in the works to be mfg'd by a large moto mfg.
 

ArthurDH

Monkey
Apr 20, 2007
162
0
Italy
When you motorise your DH bike and increase the weight by a factor of five let us know.
ok i've been rude, and i want to apologise

but the matter seems very interesting to me:
first of all, i can't see why a heavier bike makes a difference (besides having to build stronger frames and use heavier springs)...
maybe you're saying that single pivots are stronger and less incline to torsion and so heavy motocross bikes are forced to use them? or is it about something else?

about having the engine or not: i see pedaling forces are much different compared to those expressed by an engine, but i don't see pedaling efficency being the N 1 priority on a DH bike... not compared to ability to keep traction, resistance to torsion, etc... do you agree?
i mean, a DH run lasts 2-4 mins, and any pedal efficiency difference has to be VERY big to be significant is such a short time (and you're not even constantly pedalling for all the time)

i think shock could make a much bigger difference about all of this, but everyone keeps on developing new convoluted frame designs and selling them with crappy shocks... and they don't even bother making sure they're valved appropriately at least for the leverage ratio (there a few exceptions, i know...)

[btw i'm not an engineer, i'm just a third year biology student with a basic physics background... but i'm eager to learn]
 

Steve M

Turbo Monkey
Mar 3, 2007
1,995
23
Whistler
ok i've been rude, and i want to apologise

but the matter seems very interesting to me:
first of all, i can't see why a heavier bike makes a difference (besides having to build stronger frames and use heavier springs)...
maybe you're saying that single pivots are stronger and less incline to torsion and so heavy motocross bikes are forced to use them? or is it about something else?

about having the engine or not: i see pedaling forces are much different compared to those expressed by an engine, but i don't see pedaling efficency being the N 1 priority on a DH bike... not compared to ability to keep traction, resistance to torsion, etc... do you agree?
i mean, a DH run lasts 2-4 mins, and any pedal efficiency difference has to be VERY big to be significant is such a short time (and you're not even constantly pedalling for all the time)

i think shock could make a much bigger difference about all of this, but everyone keeps on developing new convoluted frame designs and selling them with crappy shocks... and they don't even bother making sure they're valved appropriately at least for the leverage ratio (there a few exceptions, i know...)

[btw i'm not an engineer, i'm just a third year biology student with a basic physics background... but i'm eager to learn]
A much heavier bike means that you have a much heavier rigid sprung mass (first of two degrees of freedom in bike suspension, well 2nd of three if you count the tyres) which means that the suspension characteristics will be totally different; you can run a LOT more compression (even for the total weight of the bike/rider combination) because the rigid motorbike part doesn't complain about shock loading. More compression (or more damping in general) tends to lend any bike more stability up until the point where the suspension can't absorb bumps freely, which is part of the reason why motos can be smashed through rediculously rough terrain at 100km/h while we're feeling sketchy at 60km/h. It also means the centre of mass is a lot lower - lower CoM means less weight shift under acceleration or braking. Less weight shift means you don't have to worry as much about anti-squat (or anti-rise/pro-squat in the case of braking), which is part of the reason why motorbikes don't benefit as much from floating brakes as DHers do. Strength etc are dependent on the specific design and manufacture - there are plenty of strong and weak, stiff and flexy bikes out there, both multi-pivot and singlepivot.

Now the engine - when a person pedals, you get a roughly sinusoidal power output, typically at about 2Hz (60rpm x 2 half-strokes per revolution, fairly typical for a DH bike), which happens to be very close to the natural frequency of bike suspension. This means that the suspension is near its resonant frequency (though it's damped obviously) and bobbing is greatly exaggerated by this. A motorbike revving at 6000rpm is delivering power at 100Hz (at least - that's assuming it's a single cylinder) and even that's smoothed out somewhat by the flywheel. This is nowhere near the natural frequency of the suspension, so there's no bobbing, the power output is almost constant. For this reason, you have no efficiency dramas with motorbikes, and they are able to reach dynamic equilibrium (eg a new sag point under constant acceleration) relatively easily, which is something mountain bikes never can.

I'm not convinced that the ONLY way to get the desirable pedalling characteristics, traction etc is via a 4-bar linkage, but it is certainly a viable method. You're right, on a DH bike pedalling efficiency is less of a concern, but being able to free up another parameter of bike design (ie removing pedal efficiency from the list of things a shock has to take care of) means you don't have to compromise as much on other things. To say that it's "not real suspension" is unrealistic IMO. Motorbikes and mountain bikes differ in a number of crucial ways.
 

ArthurDH

Monkey
Apr 20, 2007
162
0
Italy
A much heavier bike means that you have a much heavier rigid sprung mass (first of two degrees of freedom in bike suspension, well 2nd of three if you count the tyres) which means that the suspension characteristics will be totally different; you can run a LOT more compression (even for the total weight of the bike/rider combination) because the rigid motorbike part doesn't complain about shock loading. More compression (or more damping in general) tends to lend any bike more stability up until the point where the suspension can't absorb bumps freely, which is part of the reason why motos can be smashed through rediculously rough terrain at 100km/h while we're feeling sketchy at 60km/h.
i do not quite get this part
what does "the rigid motorbike part doesn't complain about shock loading" mean?
 

Steve M

Turbo Monkey
Mar 3, 2007
1,995
23
Whistler
i do not quite get this part
what does "the rigid motorbike part doesn't complain about shock loading" mean?
The rigid sprung mass of the motorbike (engine, frame, gearbox, seat, fork uppers etc - a fairly sizeable weight) provides a large amount of mass/inertia that you can use to your advantage as far as damping goes. Because it has all this mass, you can use a lot more compression damping (proportionally) than you could if the bike weighed only say 20kg instead of 100kg. The reason for this is that a large shock loading to the wheels of the motorbike will compress the suspension quickly and create a relatively small but sudden displacement of the bike's sprung mass (even without a rider on it). The thing is, the impulse (force x time, equal to the change in momentum of a body) required to move a heavy bike even 1" very very quickly is huge, because if the time component of the impulse is short then the force component has to be very large. High force = high acceleration = what feels harsh to a rider. However, when this force is being essentially "damped" by the huge sprung mass, the rider cops a lot less punishment. Again, this is why motos can run a lot more compression damping and go a hell of a lot faster over much bigger bumps than MTBs without threatening to kill the rider.
 

Akula_7

Monkey
Nov 15, 2004
917
0
Results:

http://esmtb.com/GP_Marzocchi_Sant_Andreu_de_la_Barca_mtb2469

Fabien Barel loks pretty stylish in his new lid and Bolle goggles, He has the most "euro" kit and bike ever but it comes together pretty well. Cedric is back to, on the pipe for a chap who has only been on a bike for a week or two, Pascual Canals is showing his 4th at worlds wasn't a total weather fluke either.

It's gonna be a stormer of a WC year, so many new teams, more money, ripper tracks, bags of riders.......can't wait!
 

bikenweed

Turbo Monkey
Oct 21, 2004
2,435
0
Los Osos
Awesome! Pascal won San Andreu again! It helps that he lives a block from the finish line, but he always wins that race. Pascal is a flat out ripper.

I wish I was at San Andreu again! Such a fun race.

Results:

http://esmtb.com/GP_Marzocchi_Sant_Andreu_de_la_Barca_mtb2469

Fabien Barel loks pretty stylish in his new lid and Bolle goggles, He has the most "euro" kit and bike ever but it comes together pretty well. Cedric is back to, on the pipe for a chap who has only been on a bike for a week or two, Pascual Canals is showing his 4th at worlds wasn't a total weather fluke either.

It's gonna be a stormer of a WC year, so many new teams, more money, ripper tracks, bags of riders.......can't wait!