Re: New Stuff Thread....

Postby AgrAde on Mon 17th Jul 9:56pm

slidecontrol wrote:I suspect the exhaust tube prototype will tell you much the same at a fraction of the cost of plastic version of the same thing.

As said, I'm willing to pay in both time and money to learn about carbon.

Conners wrote:
AgrAde wrote:so even if this frame is an uncomfortable noodle that pedals shit I'll come away from it better off.

Just make sure you put loads and loads of carbon and resin around the head tube. You can afford for anything else to let go, but chances of coming out of a head tube failure as 'better off' are not so high. :butbut: :crazy:

Yeah, that bit is getting extra attention :crazy:
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Re: New Stuff Thread....

Postby Astoria Paranoia on Mon 17th Jul 9:57pm

I'mma sneak a Norco sticker on it :sneaky:
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Re: New Stuff Thread....

Postby shmoodiver on Mon 17th Jul 10:19pm

36 I get but a vivid air and deore cranks?
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Re: New Stuff Thread....

Postby Astoria Paranoia on Mon 17th Jul 10:21pm

Unsealed top linkage bearing too.
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Re: New Stuff Thread....

Postby AgrAde on Mon 17th Jul 11:53pm

Crank I just found online and needed something for a presentation. Handy because I picked up an XT 785 set which is basically the same, they've got a great Q-factor for wide rear triangles and a good chainring offset for boost.

Vivid air because I have one and it has been flawless. Wouldn't mind an X2 though.

Unsealed top link bearing because Autodesk.

It's kinda not a 36. the geometry is from a 170mm boost lyrik but I just roughed the sizing, it's slightly bigger than any real fork in terms of crown size etc, but I'll probably be putting a 170mm 36 on it. I'm hoping that Fox announce a 20mm boost 36 in the next few months so I never have to own a bike with 15mm.


Astoria Paranoia wrote:I'mma sneak a Norco sticker on it :sneaky:

Put it on the actual norco, it might help stick it together :hmmm:
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Re: New Stuff Thread....

Postby Conners on Tue 18th Jul 6:19am

AgrAde wrote:Unsealed top link bearing because Autodesk.

:lol:
What are you modelling it in?
Inventor? Fusion?
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Re: New Stuff Thread....

Postby AgrAde on Tue 18th Jul 1:16pm

Inventor.
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Re: New Stuff Thread....

Postby Dougal on Tue 18th Jul 2:45pm

AgrAde wrote:That's what I presumed your reaction was by that comment. I agree, I've seen some hilarious things while researching for this project.

Yeah, the math checks out. It should ride fine and be pretty bombproof as long as I can learn enough about carbon to put it together half decently. If my experience and learnings have correctly built the theory in my head, and theory matches reality through the calcs, then the performance will be exceptional and better than anything around (for me, with the way I like bikes to ride). Of course we have yet to find out if this is the case :D

Of course the first go isn't going to be perfect, geometry will be interesting because there's very few high pivot trail bikes around to get a good idea of how they're balanced. I learned a lot from riding the Craftworks ENR. But it's as much to learn about carbon as it is to learn about bike design and you can only learn by trying, so even if this frame is an uncomfortable noodle that pedals shit I'll come away from it better off.


The main bit I don't understand is falling rate. Better to shoot for same approx rate start and end, putting up with a hump in the middle if necessary. The hump helps to offset the weak midstroke of air springs.

The biggest single problem with falling rate is shaft speed. You have higher damping force and energy dissipation at the top of the stroke (where you don't need it) vs the mid and bottom (where you need reserve).

Regarding carbon. Way back there was a Mech E student at Canterbury who made his own carbon FS bike. He used the lost foam method (wrapped and then later dissolved a polystyrene core). Rear suspension was based on the original Outland VPP with two links under the BB. Your biggest concern is getting enough compaction for fibre-fibre bonding with max surface area and minimum resin. You need a lot more carbon to make up for only a few % of fibres actually fully bonding.

The more I learnt about carbon. The less I liked it.
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Re: New Stuff Thread....

Postby AgrAde on Tue 18th Jul 3:07pm

May be an issue with terminology. A falling leverage ratio means a rising wheel spring rate/rising shaft velocity.
The fact that you're talking about a hump indicates that it is terminology - a humped LR curve is typical santa cruz, and gives a choppy top end, very little midstroke support and a rampy bottom-out when combined with an air shock. Most bikes' LR curves are the opposite of a hump which gives the supple beginning, supportive mid before backing off as the air spring ramps up.

The leverage ratio of ~3 at the start of the stroke means that the shock shaft moves at 1/3 of the speed of the wheel. This increases to ~1/2 the speed of the wheel by the end of the stroke. This means the increase in relative shaft speed gives me more damping at the end of the stroke, along with increased wheel spring rate. I've designed the bike around more linear air shocks because I need a lot of bottom out resistance but hate packing air springs full of spacers - you can't effectively damp them.
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Re: New Stuff Thread....

Postby Dougal on Tue 18th Jul 7:37pm

AgrAde wrote:May be an issue with terminology. A falling leverage ratio means a rising wheel spring rate/rising shaft velocity.
The fact that you're talking about a hump indicates that it is terminology - a humped LR curve is typical santa cruz, and gives a choppy top end, very little midstroke support and a rampy bottom-out when combined with an air shock. Most bikes' LR curves are the opposite of a hump which gives the supple beginning, supportive mid before backing off as the air spring ramps up.

The leverage ratio of ~3 at the start of the stroke means that the shock shaft moves at 1/3 of the speed of the wheel. This increases to ~1/2 the speed of the wheel by the end of the stroke. This means the increase in relative shaft speed gives me more damping at the end of the stroke, along with increased wheel spring rate. I've designed the bike around more linear air shocks because I need a lot of bottom out resistance but hate packing air springs full of spacers - you can't effectively damp them.


The geometry I'm seeing doesn't seem to match the graph. Got a pick at full compression? The shock starting around 90 degrees and losing a lot of it's leverage around your main pivot with compression. I'm not yet convinced you're gaining that much leverage on the other side of the link to bring it back to an overall rising rate.
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Re: New Stuff Thread....

Postby AgrAde on Tue 18th Jul 7:50pm

The rotation of the lower link is nowhere near proportional to the wheel travel. Also see: Santa Cruz V10, or any other bike using "VPP" with the shock driven by the lower link.

Through the first part of the travel the rear triangle is mainly rotating clockwise around the lower link, meaning it doesn't move much. In the last part of the travel the movement of the rear triangle is much more translational so links are rotating a lot further for a given amount of wheel travel.

The red line extending forward from the main pivot-ish area is the IC movement of the rear triangle through the suspension stroke, as it moves forward away from the rear triangle the movement obviously becomes more translational and that lower link starts moving a lot for a given wheel movement.

I kinda presumed internal forces would get weird but they don't. Other VPP bikes damn near inflect.
pres2.jpg
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Re: New Stuff Thread....

Postby mudguard on Wed 19th Jul 5:57am

Coil for your Pike (or various Fox)


https://www.pinkbike.com/news/push-acs- ... -look.html
p5pb14947328.jpg
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Re: New Stuff Thread....

Postby Wobbler on Wed 19th Jul 8:20am

MSRP $389, supplemental spring MSRP $80

you'll prob need 3 odd springs to get it right? So at least a grand by the time you get it here etc
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Re: New Stuff Thread....

Postby mudguard on Wed 19th Jul 8:28am

Wobbler wrote:So at least a grand by the time you get it here etc


Yeah Push don't seem to do anything cheap. Still perhaps there is a coil Renaissance coming. Ohlins have a 29er coil and just made their first 650B fork. Wonder if the big two will bother with a 160mm single crown with coil.
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Re: New Stuff Thread....

Postby Dougal on Wed 19th Jul 9:04am

I actually like that they've gone that expensive. It keeps the lower end of the market open for other, simpler, coil conversions.

The 7 different coil rates is why not many other people play this game. The investment is pretty big.
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