Ashley Kalym, Founding father of Rock Sled Suspension, offers us some perception into the what, how, and why of the long-travel fork he has been growing during the last 3-4 years. Ashley believes he has overcome the constraints of a conventional telescopic mountain bike fork design, specifically the stiction and binding points, with a leading-linkage fork design that makes use of an off-the-shelf-rear shock to damp impacts.
Rock Sled Suspension Main Linkage Fork
Although unusual, linkage forks are nothing new on the planet of mountain biking. Belief Efficiency’s Shout and The Message multi-link forks did achieve some traction for a brief time period, however the huge model suspension producers have stayed away from the design, selecting as a substitute to refine the damping methods of their conventional telescopic forks, whereas including weight to and growing the stiffness of the chassis.
“It by no means actually made sense to me as to why you’ll tie the chassis, shock, and damper right into a single construction. Any power that’s placed on the construction will in flip affect the damper”, explains Ashley. He’s not the primary to have had ideas alongside these strains. Movement-France, Adroit and Construction Cycle Works are some newer examples of manufacturers trying to overcome aforementioned biding points suffered by the bushings in a telescopic fork beneath flex, in addition to another traits they see as detrimental to efficiency.
Whereas Movement and Belief developed proprietary dampers for his or her linkage forks, Adroit and Construction’s designs use off-the-shelf air shocks and thus profit from their big selection of exterior changes. Ashley felt it made lots of sense to make use of a design that might use just about any rear shock available on the market; get the scale right and the leverage curve smart, and the fork’s conduct might, in some ways, be as tuneable because the number of rear shocks obtainable.
The entire aforementioned are considerably extra difficult than Ashley’s single-pivot main linkage fork, using a number of pivots. The primary iteration of the Rock Sled (not proven) was single-sided with a one-piece carbon steerer and carbon leg. It had a single hyperlink and a shock absorber delivering 160mm of journey. That was a bare-bones, proof-of-concept prototype.
Within the V1, the brake caliper was bolted instantly onto the hyperlink. Ash tells us the anti-dive power was huge. “Using alongside, should you braked with any type of power, the suspension would wish to prolong lots, except you had lots of weight over the entrance. It was actually fairly violent”. Aside from the anti-dive, Ash says the fork felt stiff sufficient whereas driving, and that it didn’t actually really feel any totally different from a daily fork.
With the second prototype, seen all through this text, Ash sought to resolve the aforementioned braking situation by mounting the brake caliper to a floating brake arm. It takes on a parallelogram association, so when the fork compresses the brake caliper stays equidistant to the fork leg, irrespective of the place within the journey the fork is working, simply because it does within the case of conventional telescopic forks.
So, how does it experience?
“The fork rides like a traditional fork by way of its steering conduct, axle path, and braking conduct. The place it differs is the a lot larger sensitivity, adjustment, and efficiency. Using bearings as the primary technique of fork motion implies that binding and stiction are just about non-existent, and with the ability to swap out the shock for any kind that you just want means a lot larger adjustability. Additionally, on account of there being some very succesful shocks obtainable (PUSH, Quick, EXT, and so on.) I believe the efficiency by way of damping can beat any telescopic fork on the market. As well as, as a result of the fork has a leverage curve then it might probably obtain the grail of being delicate off the highest, supportive within the center, and supportive at backside out” – Ashley Kalym, Designer of the Rock Sled Fork.
The place the Rock Sled Fork does differ considerably from a telescopic fork, is in floor clearance. Because it compresses, the fork legs are pushed down towards the bottom. Ashley says that, with a 29″ entrance wheel, the bottom clearance at bottom-out is 209mm (8.22 inches). Regardless of that, he says he hasn’t discovered any points with it on the path.
Although the top angle delivered by the Rock Sled appears wildly steep upon first look, it really is available in at 63° on Ashley’s Nicolai G16 Enduro Bike. With the linkage design, the axle path differs to that of a telescopic fork. Whereas the latter strikes in a straight line, following the angle of the steerer tube and thus head angle, the axle of the Rock Sled Fork will observe extra of a rearward arc because the fork is pushed into compression.
The prototype seen above has a 45mm offset at top-out, reducing to 17mm at bottom-out. A discount in offset proportionately will increase the bike’s path determine. Ash says this might, at the very least on paper, enhance your steering stability the deeper into the journey the fork is compressed. A 3rd prototype that was lately 3D Printed, designed for 160mm journey with a 571mm ATC is claimed to have a extra normal axle path with a 51mm offset at top- and bottom-out.
It’s value declaring that, even within the Rock Sled Linkage Fork, there’ll after all nonetheless be forces utilized to the rear shock outwith the airplane during which it gives shock absorption, however Ash has organized the linkage in such a method that, at the very least in idea, these forces ought to be enormously diminished compared to these skilled on a telescopic fork.
The gap between the pivot and the fork’s 20mm axle is simply about 200mm. Ash says the leverage that may be exerted over that distance is kind of small. Evaluating that to a rear suspension linkage, that distance is significantly lower than half the space between the rear wheel axle and any foremost pivot on the entrance triangle.
The newest design of the Rock Sled fork additionally makes use of a 15mm axle, primarily to extra simply serve the market as most path and enduro riders could have a Increase entrance wheel (15mm x 110mm). The ambition with this model was to scale back the variety of distinctive elements, simplifying the design from a producing perspective. The left hyperlink that doesn’t drive the shock is now the very same half as the fitting hyperlink that does. That is mainly lowering the prices of the CNC machining. Ashley has additionally diminished the footprint of the fork, bringing the width to <200mm, nearer to that of a standard fork.
What are the following steps for Rock Sled?
If pleased with the experience really feel of Model 3, Ashley will ship the Rock Sled Fork off to EFBE for testing, previous to producing a restricted run of forks on the market. He’s trying to maintain the worth as little as attainable, with a purpose to allow the best variety of folks to attempt it out. And, the much less cash the shopper spends on the fork, the extra they’ve left to spend on a high-end shock. Ashley tells us he has intentionally saved issues easy by way of development, bearings, nuts, and bolts, and so on., in order to make the manufacture as low cost as attainable, and subsequently the retail value as low cost as attainable. “I wish to goal for beneath £1,000/$1,000, however how a lot beneath this value level will probably be I don’t know”.
You’ll be able to maintain updated with Ash and Rock Sled Suspension on Instagram @rocksled_suspension and @rocksled_bikes
