I’ve been working on the Snakedriver project since 2019. 5 years of R&D and 4 prototypes have brought me to this current iteration. After an evening of assembly, tuning and triple checking my work during the build process, I took V4 of the Snakedriver on its first shake down ride. I couldn’t be more pleased. All of that time spent these past 5 years, the lessons I’ve learned and knowledge gained, and especially the hundreds of hours of design time spent since this past January on the CAD model in Fusion 360 have really paid off with this latest test. In short: I think I nailed this one. It’s super poppy and playful, nice and firm when you need it, climbs a lot like a hardtail and is a total ripper downhill. There’s still a bit of refinement to be done but right out of the gates this is the “one”. I’m beginning to see light at the end of the tunnel. So lets roll up our sleeves on V4 and see what makes this one different than the previous 3. My design process starts out on the trail. The mantra “build, ride, repeat” rings true to my design process and methodical approach. V3, which was a Horst suspension platform, taught me a lot about what I wanted in a suspension platform. Three things stuck out from that build. 1. A 160/140 trail bike was a lot of bike for how I like to ride. I definitely felt over-biked. 2. The bike ripped down hill and climbed well but was a bit too long overall. I missed the “POP” of V1 which was a single pivot. 3. The Horst was complex. There were A LOT of parts and in really wet weather, which we had an abundance of this past spring and summer (I believe it basically rained every single day from mid-June to the end of July, I kid you not) maintenance was constant because of all those moving parts. So with the above 3 in mind, I set about this past January outlining a few design goals to help steer the project into new territory: 1. Simplify. Less moving parts and reduce overall parts count. This meant exploring a flex pivot (I immediately eliminated 4 bearings, 4 spacers, 2 cone washers, 2 cap screws and 2 shoulder bolts). 2. Less travel. 140mm front / 120mm rear seemed like a nice pair of numbers for a trail bike. This also gives me the option to choose between either a Fox 36 with a 140 travel kit for a more aggressive build or a Fox 34 with a 140mm travel kit to shave some weight. 3. Trunnion mount. This removes a set of bushings/needle bearings and spacers from the shock and moves bearings into a CNC machined rocker. 4. Stock hardware. As much of the build as possible, I want to use existing hardware. This makes maintenance and field repairs that much easier. Almost every single piece of hardware on V4 is available from McMaster-Carr, your local hardware store and known reliable sources (SRAM’s UDH, Paragon Machine Works thru axles). 5. Shorten up the wheelbase and chainstays. I went long for the Horst, now I wanted to get more of that POP back into the bike. Shortening the overall wheelbase has really proved a wise decision as that first test right? Man-o-man. The bike’s got pop again! 6. Redefine what is expected in a trail bike in my own way. A lot of trail bikes (aka downcountry) mix trail and XC in some ways. Personally, I really like to be aggressive and go after lines. But I don’t ‘go big” per say. This isn’t a park bike and its not meant to huck 10-15’ drops. I like to bunny hop stumps and jib off features. I like to manual. I like to climb and carve turns on the descents. I like to go fast and lean hard. If that sounds like your kinda bike, keep reading… So that meant choosing some maybe out of the norm numbers which I’ll list below in short order. So January through to May was spent in Fusion 360 CAD’ing up the 120mm flex pivot version of the Snakedriver. I used all that feedback from on trail ride experience and leveraged fabrication knowledge I had gained from 3 previous prototypes to further refine how the parts were designed to make the bikes a bit easier to manufacture. This is an important point: Ease of manufacturing. Both for me, for my 3d printer and for anyone doing CNC work. That means attempting to design simplicity. That’s a tough parameter to meet. Complex is easy. Simplicity is hard work and really focusing on your design process from start to finish. So what I came away with from those 5 months of design work is as follows: · 65° HT angle · 76° effective / 74° actual ST angle · 1244mm wheelbase · 430mm chainstay length · 25mm BB drop · 185x50mm Trunnion Shock · 547mm Axle to Crown (140mm travel unsagged dimension) · Designed around a 30mm stem (allows this size to then be tuned by potential client with the use of 35, 40 and 50mm stems) · Room for tool mount under TT · Full sized water bottle fits inside front triangle and is mounted on DT · UDH compatible · ISCG 05 Compatibility · *Reach: 479mm / Stack: 620mm (*These are custom numbers but represent approximately a size large frame FYI) · Cockpit length is custom (514mm) which I have been playing with personally – I’m really digging this more upright stance now! Design work complete, it was time to send parts off to RAM3D for printing and contact colleagues who showed an interest in helping out with the project and do some CNC and water jet work. Sean at Handerhan Cycles, Joe at Cobra Framebuilding and Thomas at Hosford & Co. all contributed to this project and their professionalism, their tight work and enthusiasm was not lost on me. These are 3 very talented business owners and were a joy to work with. The fit and finish of parts I received from them were very high. Parts back from Print: Here you can see how I really changed the yoke and moved the bearings into the frame vs the yoke as well as refining the overall design profile and compactness of the part (This part has since gone through further refinement and has seen a few revisions which I’ll go over in a later post): The rocker was machined to my specs by Sean at Handerhan: Two parts combined (Sean doing the machining work for the brake mount, RAM3D doing the 3D SLM dropout): UDH compatibility realized: The reason for the proprietary brake mount is ISO and Post Mount required a few hoops to jump through and other than flat mount (which I absolutely DID NOT want to use) there are no chainstay mounting standards. This is why I came up with my own: To tuck the brake caliper between the loop of the seat stay and chainstay but also to free up the seat stay to flex through its 1° of rotation (approximately) as the suspension cycles through its travel. I may post the specs once its further refined but till then, this is proprietary to the Snakedriver for the time being. ISO may come into play at a later date as I do want to work through additional iterations of the swing arm now that I have begun the testing process. Beginning the hardware finalization process. Joe at Cobra turned blanks of the main pivot axle for me which was a huge help hitting precise tolerances I was looking for in this part: Last but not least are the shock mounts and ISCG 05 mounts (YES, Finally!!) in 4130 and 6/4 Ti from Thomas at Hosford & Co. Again, amazing turn arounds and high quality work from a super talented human: Parts in hand, it was time to finally finalize a drawing and get to work: The first step was updating my seat tube pivot jig. This went smoothly until I had an entire assembly welded and realized I had made an error in the rocker pivot location which was off by 25mm. I think when I read off the number from the CAD file (which is in metric) and translated it to imperial as all my machines are in imperial I read 8.5′ but I wrote 7.5″. So that meant I had to have parts reprinted and amend the seat tube pivot jig. So that was a bit of a setback but luckily, RAM3D was able to turn parts around for me quickly. Here’s the new assembly in the new jig with the correct pivot locations! What was nice though was I did make a running change to a big design feature I had overlooked: A bearing stop. The issue was how to make both bearing bores concentric without having to flip the part to bore them to tolerance. I was going to just use an internal spacer originally but this mistake had me rethink the entire assembly and design around using a snap ring as a bearing stop. This solves two problems. 1 it creates a bearing stop and 2 I can plunge straight through both bearing bores to make them concentric in one step. A local grinder, GriTech in Bennington, NH, reground a 1.125″ 6 flute end mill for me in HSS to my tolerance spec (27.975mm) and it came out perfectly. Nice bearing press with a definitive stop thanks to the removable, AND STOCK, snap rings sourced from McMaster Carr. (Note the tacking jig duals as the boring jig in the mill…) With the seat tube assembly complete, I could now finalize the front triangle: And then move on to finalizing the swing arm. This was another piece of tooling I updated and dedicated albeit its still adjustable. Once I nail down kinematics, I’ll produce a fixed version that allows for different CS lengths. This one came out correct the first time around. Here it is with a swing arm mocked up: With the front triangle finalized, and bearings test fitted, I was able to assemble and fit the swing arm and finalize the seat stays. With this wrapped up, the last step was to fit the lower shock mount. This part proved a tad difficult because the bend in the DT had a bit more spring back than I was anticipating so I had to cut down a lot of the part (which I did give myself some extra in the part file just in case). But because of this, I need to reverse engineer a DT bend so I can update my CAD file and then refine the lower shock mount so the fitting process isn’t as laborious. I got it done, but this needs my attention. I also need to design a pair of 185mm shock dummies so I don’t have to use the shock in the jig. But this was HUGE so tacking was next in the process. And once the bike was tacked, I was hard pressed to just put my nose to the grindstone and get this frame welded and finished. As I mentioned earlier, the yoke has seen some revisions. Also of note is although a 32t ring fits, it JUST fits. I need to lengthen up the yoke a tad and refine the transition between vertical and horizontal features that flow from the pivot to the chainstay to make room for a 34t just in case. I think lengthening this part by about 5mm and refining where and how these two elements transition will solve the problem and add an extra layer of strength and stiffness to this part: And the welding process. The shortest duration of time is one of the most fun naturally: Once welded, it was time to finalize all the mounts. A bit of refinement is in order for the tool mount and cable mounting points, but these worked well for the first iteration. Once all finished, it was reassembly time to triple check fit post weld. Everything went back together smoothly: Here’s a comparison of parts breakdown between V3 (below): Compared to V4. See what I mean? Way less to manage and the majority of these parts are STOCK. Huge feather in the cap below: Then off to powder. My coater, if you get work to him on a Thursday, he’ll have it turned around that Friday. Garrette at Rev Limit Auto in Merrimack NH came through for me big time on this one. Ready for the weekend of assembly and testing! And assembled and tuned… That was Saturday. Today is Sunday and I had a hard time sleeping last night! Lynn was hiking for the day with her sister and a friend so that meant Poka and I were headed out for the shake down ride. I chose a classic loop, dubbed the “Sayer Loop” as we used to take Kaya on this loop a lot and Lynn and I know exactly what trails either of us will be taking if we tell each other “I’m doing the Sayer Loop!”. It’s a nice mix of rocks, roots, climbs and descents with lots of fun stuff in between. Basically all you need from start to finish to thoroughly vet a new design. Like I mentioned at the beginning, this bike exceeded my expectations. It climbs like a hardtail, but descends like a full suspension bike with lots of pop and very playful on all features in between. The shorter wheelbase made the bike very nimble without compromising stability and the HT angle was just slack enough to get rowdy without being too enduro focused. A shorter rear really allowed me to loft the front end and quickly pick the bike up and over obstacles on the trail. Put it all together and you get a bike that can be leaned hard and carved. One big thing I noticed was this platform was more akin to the single pivot where it rode a tad higher in its travel and felt a bit more firm initially and through midstroke. The Horst tended to feel a bit too plush and sit lower in its travel creating the occasional pedal strike. Admittedly I was running about 5-7psi too much air in the shock and in my excitement, I left my shock pump at the shop by accident but with a bit of refinement I think the shock tune will be just so for the next ride. But overall, the bike is very playful, poppy and feels incredibly fast both on the climbs and the descents. I’m honestly sitting here surrounded by a post test ride glow. Next steps are refinements to the yoke, lower shock mount and cable mounting/tool mounting locations (The first one by the HT could be a bit lower, and the tool mount could be a tad closer to the ST). Additionally I want to explore different swing arm configurations testing different O.D. seat stays and refining the rocker and main pivot assemblies. I have some ideas how to cut weight and cost from these parts with a combo of turned and water jet cuts for the rocker and main pivot locations with a simplified printed part just for the lower pivot that will cut a lot of weight, expense and fabrication hurdles out of that particular part to allow me to use a full length radius seat tube to make the DT/ST overlap a bit easier to fabricate. But till then, here’s the full build set on Flickr from start to finish. Watch this space, Flickr and Instagram for updates as I get closer to finalizing this platform. The above bike is “the one”. There’s officially light at the end of the tunnel and the plan I put together to realize the lines of this bike go all the way back to 2007 when I first started building. This bike from 2012 was one of the last of its kind I made. I also knew this bike would make an ideal full suspension platform and in 2012 I decided to shelve the concept so I could develop it into a FS bike. Here’s that bike: And the current iteration of the Snakedriver for comparison! Only took 11 years to get here. More soon as I continue to refine the 120mm flex pivot.