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Dual front suspension system on a KTM


Kinematics

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2 hours ago, cwtoyota said:

Looks like nice work and a neat project. 
I've always been intrigued by leading link forks, Ribi forks and the other alternatives to telescopic forks..

What are the goals in using the dual suspension system?

 

The dual suspension gives a very much improved level of suspension compliance and response that is not possible with any design we have seen so far.
It does this by mounting the telescopic fork at a steeper angle....this gives the fork much better small bump sensitivity and makes it a lot less prodive when braking...the telefork in no longer being asked to provide a high level of bottoming control so it can be a lot more linear through its stroke and so reducing any midstroke harshness etc
The secondary suspension gives the front wheel a second wheelpath...it allows the wheel to move back at around a 45 degree angle...this combined with the teleforks more vertical wheelpath means the front wheel can move more freely in response to a greater range of bump forces being put into it....so a much higher level of suspension compliance/sensitivity and control.
The secondary suspension is also much stiffer than the telefork and it  now is taking on the roll of giving the required bottoming control and it can be tuned independant of the telefork...so there is less cross talk  and much less compromise in achieving a balanced overall setup.

51 minutes ago, rjg said:

Are you the same person who put it on a kx450? That was a true gem.

I am.....

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7 minutes ago, rjg said:

Sexy AF, nice job fella.

Can you post a video of it and give us some side views to see that contraption in action.

Will do mate when we get some...this is a demonstrator...the plan is to get people on it so they can experience for themselves what it has to offer.

This front suspension has the potential to revolutionize dirt bike front suspension in a big way...a new direction.

 

 

Dual suspension KTM350. 2.jpg

Dual suspension KTM350. 3.jpg

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  • 2 weeks later...
1 hour ago, djidji said:

Interesting work!

What's the travel of each path?

Edit: found it. 300 mm + 100 mm

jeanjean

I miss linkages at the rear too 😉

The travel on the KTM is different....250mm travel on the forks ( shortened 50mm ) and 90mm on the secondary suspension...340mm total...

It has 390mm of ground clearance under the lower frame rails.

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  • 4 weeks later...

Ok so we have recently have had a couple of very experienced riders test this bike......Geoff Ballard and Ben Grabham.
Geoff loved it....words from the man himself....

"It was amazing to ride this crazy forked Kato 350, and for me it was unequaled in 3 main areas..1: For square edge high speed type bumps it was hard to notice you even hit them. 2: Landing off jumps was like landing on pillows and 3: It’s cornering and especially cornering in technical ruts with tree roots etc it was very confidence inspiring and effortless.

It seems the main reason that from steering and bump control and stability is so good is that the trail of the fork changes through its stroke (350mm travel) allowing all these good things to happen.

The set up was just a little soft for me but it’s early days of development atm so the next test will be interesting as well and it’s great to see an Aussie designer coming up with something that certainly works so well.

Great job Suspension Smith!"

 

Ben "Grabbo" Grabham was also very impressed...he could see this setup working very well on a Desert racer in events like Dakar...Finke...etc....he is currently writing an Article on the bike test he did which will be in Australasian Dirt Bike magazine.

 

DSCF3584.JPG

DSCF3602.JPG

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24 minutes ago, rjg said:

 Budzzzzzzz  that is awesome.

 I am aware of both of those guys and if they say those kinds of things then you are travelling down a good path.

You get any video of it in a action?

 

No Video action on the KTM yet...not quite that organised ....maybe soonish.

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43 minutes ago, rjg said:

How did you go about finding a spring rate for the front linkage shock? 

Still in the guessing game of development or got a feel for it now?

At first it was just by careful calculation at what range it should need which was close...now its def known as per rider weight /discipline etc.

What is interesting is the spring rates we are using...the forks for instance the OC coil spring ones are using a .52kg/mm spring rate in each side...which is stiff even for a MX bike of same rider/bike weight...yet Geoff Ballard for example thought the front was on the soft side.
Whats going on here is a few things...one is the forks are more vertical which gives an inherently softer "vertical wheel rate"...the other is the addition of the secondary suspension on top of the Telefork...when you put two springs on top of another in series you get a softer overall spring rate..in this case the telefork is 1.04kg/mm combined ( ignoring the angle of the fork to keep it simple )...the secondary suspension has a rate of 5.4kg/mm...this is around 5 times stiffer than the fork....but when you add them in series.....they give a combined spring rate of .87kg/mm or equivalent of two .435kg/mm fork springs.....its actually way more complex than that for various reasons but thats a simple breakdown of what going on in terms of spring rates.

"One" of the knock on effects of this kind of setup is the ratio of unsprung mass too spring rate....the unsprung mass of the telefork on this bike in no different to any other comparable ktm dirtbike...but it is using a much stiffer spring rate to control this unsprung mass ( the telefork has a higher natural frequency )...but with no negative effect on overall suspension compliance because of the added compliance of the secondary suspension...this means the Telefork displays a much much better control over its unsprung mass ( wheel/tire/tube/brake disc/telefork components ) so better wheel control over bumps etc and this translates too better traction/road holding/stability/feel/braking etc......

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1 hour ago, Randy300XC said:

What type of riding is this best suited for?

The KTM has been built around Enduro/trail application....the dual suspension is probably best in this area...it would make for a killer Desert race bike as noted by Ben Grabham who has lots of experience in this kind of racing.
With further development I think it would perform great in a MX bike...but a bike built from the ground up.

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