Fork flex

supersonic

Think your maxles would help?!

http://www.youtube.com/watch?v=fiO6R4P1yxY

Northwind

I'd love to put an early spaghetti-Sid in that machine and see what happens.

The Northern Monkey

Explains why my tapered 9mm QR reba's feel stiffer than the 1 1/8" maxle revelations I had..


Reckon the domains would snap the machine though

supersonic

Northwind wrote:

I'd love to put an early spaghetti-Sid in that machine and see what happens.

Would be interesting - but if the steerer was thick enough, may flex less, especially with the shorter travel!

Tapered steerers are A Good Idea.

Northwind

I am Unconvinced, those things had more flex than they had vertical travel.

Course it's only a small part of the picture, forks get stressed in various directions but it's still cool

The Northern Monkey

So it begs the question.... what is the benefit of 20mm/15mm axles?

supersonic

Very true. But I still think a lot of flex we get when cornering is still from the steerer and crown - the steerer can of course flex in all directions.

Still not entirely convinced with 15mm.

Northwind

Don't think anyone's convinced with 15mm, Fox obviously aren't or they'd have used it on their big forks. I did quite like Rockshox press release... "Look, 15mm is a bit crap, 20mm is better. But youse idiots want it, so on your own heads be it. Fannies". Well I'm paraphrasing slightly.

cat_with_no_tail

and THAT ladies and gentlemen is why Double Agents have 9mm QR and are stiffer than a stiff thing.
win!

bluechair84

I was quite surprised by the amount of flex happening at the crown / steerer junction. But won't a larger axle help torsional twisting of the legs which this machine is not doing? It strikes me the axle will cope with off cambers and rock gardens as will be be better able to hold the wheel straight.

Oh, and what on Earth's a double agent?

Richie63

bluechair84 wrote:

Oh, and what on Earth's a double agent?

0014

cat_with_no_tail

bluechair84 wrote:

Oh, and what on Earth's a double agent?

Bionicons Fork.
QR (also 15mm options)
80-160mm travel at the push of a bar-mounted button
Weighs about 3.5lb (including bionicons version of a stem)

Stiffer than a stiff thing on viagra.

bluechair84

Ah of course

Raymondavalon

One thing I noticed on the test video, the forks weren't being compressed at all during the testing. I'd like to see that test undertaken with the forks' travel in use. Sure it's likely to flex less if the fork is compressed, but I think that the stanchions would be more prone to bending whilst compressed as well as more stress on the steering tube

bluechair84

Raymondavalon wrote:

One thing I noticed on the test video, the forks weren't being compressed at all during the testing. I'd like to see that test undertaken with the forks' travel in use. Sure it's likely to flex less if the fork is compressed, but I think that the stanchions would be more prone to bending whilst compressed as well as more stress on the steering tube

Though, the overlap between stanchion and lower leg should give more support, so adding to their resistance to flex. And the moment (force about a pivot) will go down as the distance is reduced, so less flex at the steerer too.

nicklouse

But as the contact points are the same the is no change other than the length. But if the machine sill operates with the same stroke the flex will be more. But the force will be more. But there are other machines that do something similar to what you are thing about.

Bikerguy15

bluechair84 wrote:

I was quite surprised by the amount of flex happening at the crown / steerer junction. But won't a larger axle help torsional twisting of the legs which this machine is not doing? It strikes me the axle will cope with off cambers and rock gardens as will be be better able to hold the wheel straight.

Same thoughts over here.

nicklouse

http://www.youtube.com/watch?v=NeLi7wSeaDA

bike producers also do their own testing.

supersonic

As nick says, would require more force for the same amount of axle movement with the fork compressed.

Torsional stiffness - according to fox, QR15 increases the stiffness by 15%.

Double agent - interesting fork! Have taken the oversize method pretty much to the extreme, as the stanchions are very thin. Still a 4lb 160mm fork is good going, but wouldn't like a front ender ;-). BR dodn't like the damping either.

cat_with_no_tail

supersonic wrote:

As nick says, would require more force for the same amount of axle movement with the fork compressed.

Torsional stiffness - according to fox, QR15 increases the stiffness by 15%.

Double agent - interesting fork! Have taken the oversize method pretty much to the extreme, as the stanchions are very thin. Still a 4lb 160mm fork is good going, but wouldn't like a front ender ;-). BR dodn't like the damping either.

I've got the upgraded damper cartridge fitted to mine now which makes a world of difference.

Does put the weight up to over 4lb though.

Stanchions are not *thin* as such, they just look it compared to most duallys. They're regular 32mm stanchions.

Also, Bionicon has the "FIT" system.

http://www.bionicon.com/en/bionicon-fit

F.I.T. = front impact transmission system.

Our patented F.I.T. bearing technology transforms frontal impacts into tensile forces along the steerer tube. The split tube construction allows a significant reduction in weight whilst simultaneously pre-loading the headset bearings.

How much of that is science and how much is technobabble I have no idea, but the theory is sound.

They've also got a bit about frontal impact on this page

supersonic

I meant thin walled, rather than small diameter.

Northwind

Raymondavalon wrote:

One thing I noticed on the test video, the forks weren't being compressed at all during the testing. I'd like to see that test undertaken with the forks' travel in use. Sure it's likely to flex less if the fork is compressed, but I think that the stanchions would be more prone to bending whilst compressed as well as more stress on the steering tube

But then the leverage force will be reduced (you could set up the machine to deliver the same force, but that wouldn't be a fair comparison)