Back in July, I penned the following: “V2 of the Snakedriver is currently at powder. It’s been a long road to get to V2 with a delay happening last season that most likely was the best thing that could have happened for the project. It forced me to reassess the overall project and the literal “how” this bike would be produced. So that delay took me straight back to the drawing board to consider the emerging technology that is widely known as 3D printing, or rather more specific: Selective Laser Sintering (SLS) / Additive Manufacturing. It’s the complete opposite of traditional CNC machining where a block of material is carved up to produce a part from a CAD file. This is really a 21st century version of casting where the CAD file is the mold and the SLS machine is the furnace that melts metal in thin laters from powder on to a plate. Quite literally making lugs for tubes to “key” into. (Don’t let anyone tell you otherwise.) Which is amazing because as an industry, we’ve potentially come full circle. What’s fascinating though, and a huge advantage as an industrial designer, I’m no longer approaching parts as a shape or as a block that needs to be carved up from the outside. Yes, the manufacturing is considered from the start just like in traditional machining which as a designer you leverage to produce a more easily manufactured part but now you have true access to every aspect of the part geometry both internally and externally. So I really dove in head first and completely redesigned V2 from the ground up attempting to balance both traditional CNC manufacturing and leveraging additive manufacturings strengths.” That was July. Fast forward to August… August 10th to be exact. Up in the Carrabassett Valley of Maine. After the events of the 10th in Maine, I’ve been beavering away making another prototype which for reasons I’ll explain in just a bit, has been even more of a journey and I feel as though I’ve learned even more. Not just about this process, or about additive manufacturing, but about my own design process and methodology. Since August, I’ve been working on V3 which I just finished this past October: So back to Maine this past August. Lynn and I had been looking to take some much needed time off, and do some mountain biking. And… not working. We headed up for about 4 days of riding. It rained every day we were there but in true fashion, we made the best of it and had fun despite the rain. This is where modern weather apps really shine: You can find the holes in the weather to get out and ride if you’re stuck on vacation and it’s decided to be not so perfect. So back to August 10th. We had checked out the trail system the previous day and decided to make a longer day of it on the 10th. The previous ride we bumped into a local who recommended a climb. Immediately a few short pedal strokes into the trail I knew this was intended to be a downhill. So we climbed it anyway. But I wanted to take the new FS down this trail so on the 10th, we planned the ride to end with that trail and have some fun. Well, it opened up on us halfway through the ride (the one day I did NOT bring my rain jacket despite weather saying no rain was to occur – lesson relearned). Part of the ride included a bunch of climbing to get back up on a ridge to drop back into this trail we climbed the day before. We ate a bit and down we went. The trail was greasy from the days previous rain. So I was taking my time which probably proved a good idea what lay ahead of me. About 1/4 of the way into the descent, there was a deeply scooped right hander that had a nice berm. As I entered the turn, at almost a walking pace because of the greasiness, I heard an audible THUMP, almost the same sound you hear when a rock clangs off a carbon rim. Only with that THUMP, the rear end shifted decidedly to my left followed by the sound of rubber on frame. My heart sank a little bit. “Did I just snap the thru axle or did something come loose?” I dismounted and checked the wheel. It was centered but was incredibly loose. My eyes and hands scanned from rear to front and there it is. The drive side swing arm’s yoke had snapped catastrophically. Now my heart REALLY sank. I let out a Ralphy “OH.. NOOooo”. Lynn was far behind me so I was all by myself. Here’s a shot of the failure point: Immediately my head went from “vacation mode” to hyper-analyzation “what did I do wrong” mode. I took a step back and looked down trail as the descent went off into the distance of thick foliage. I reminded myself: Don’t focus on what just happened – Focus on what decisions you made and reach understanding about how you arrived right at this spot. I decided to reach that understanding and as I began my walk down the rest of that descent, I started rolling over the design, my choices, the process and what could have gone wrong. Lynn caught up and was wondering why I was walking. After I explained, Lynn gave me the additional pep talk I needed. This was all part of the process and I was thankful this happened now and not after a project of this size had been released and I wasn’t hurt in the process. It was a long walk down the mountain as it was now raining yet again, and I was eaten alive by mosquitos at the bottom. But I made up my mind to be as open with this failure as I could be and to learn from the process that proceeded. When I got back to our cabin, I immediately reached out to the small handful of peers with experience in Additive Manufacturing: Mark at Prova, Adam at Reeb and Elliot at Heeler. Additionally I spoke with a colleague and classmate from RISD, Max at Nice Bikes (previously Pratt Cycles). I shared Fusion 360 CAD models and opened up about the design and process with these peers. I really wanted to understand what I did right, what I did wrong, discuss the additive process, and dig deeper into this technology to further understand its intricacies. From those discussions, this is kind of a cliff notes of what I learned: · Additive Manufacturing inherently has many variables (which in isolation are marginal, but if many are present in the final print can lead to issues in a relatively short time frame). · Be aware of how many times the powder has been recycled. · The “how” of powder handling is extremely important. · Partner with suppliers who are actively testing their batches of prints. This way, the manufacturer is adhering to a protocol for consistent part strength. Many print tensile bars with each plate to test tensile strength, so if there is a problem with a print, it can be discovered immediately and the part or batch an be reprinted. · Understand and request material characteristics / data from the printer as this can vary from supplier to supplier due to the next note… · Expect 60-70% strength of parent material. · Print consistency depends on resolution of machine doing the printing. · Print orientation is critical · Wall thickness and lattice structures need to be weighed hand in hand and considered depending on application and location of part. · Think of parts like a ship mast: Smooth gradual transitions throughout the part must be adhered to. · 316L is decidedly not up to the task of printed high stress area shelled parts (think headtubes, yokes, dropouts etc.) due to the incredibly low tensile strength of the parent material. This last point really struck home. I knew I had created a confluence of forces where the part failed design wise. But if that part had been machined, there is absolutely no way that would have failed the way it did. 316 is incredibly soft as a material relative to other stainless steels. It “should” have bent, rippled or folded before it failed completely. So what i was seeing may have been a combination of a few factors: A. Design. The transition between where the swing arm connects with the main pivot and where the chainstay is welded could be more gradual, so in its cross section, there’s more material and width along with smooth gradual transitions to distribute forces more evenly. B. There was some sort of inclusion or void in the print due to print orientation / print resolution, material handling, number of times powder was recycled or all of the above. Like I stated earlier, how many times the powder has been recycled and how the material is handled is critical. The resolution of the print and orientation of how the part has been printed can both effect its strength if variability is present in the printed part. C. Fatigue. This area of a bicycle is subjected to an incredibly amount of dynamic pedaling forces. 316’s tensile strength and fatigue strength are relatively low, so perhaps this material was a poor choice for the parts intention at that location of the bicycle. OR… D. All of the above. After really exploring all of the above, I have a bit of a suspicion that what I saw was the result of not a properly designed part out of a material that was ill suited for the application the part was intended. There may have also been a bit of an issue/s with the part at that location since it failed relatively quickly (2 weeks into testing) but I’m more apt to look at my own decisions than to place blame on another’s as there are a lot of unknowns I’m dealing with. However, if the part behaved as most 316 parts, it *should* have shown signs of buckling or bending, and not been a catastrophic failure. There are ways to ultimately understand this but at a relatively high cost. Personally, I really do believe that 316L is just not up to the task of shelled components on a bicycle. Small parts like braze-ons, and ports that are non-load bearing, I believe the material is both economically viable and an acceptable choice. Or you need to design the part to have completely over design the part with ridiculous wall thicknesses as well as internal lattice structures which defeats any weight savings you may be achieving via a printed solution. So where does this leave me? First it meant a full redesign and refinement of the yoke and what I call the turnbuckle. V1 vs V2: There were a few other tweaks to existing parts I made as well but those two parts are the most visibly different between the two batches and material. In addition to design refinements, wall thicknesses were changed and internal lattice structures were changed for several of the parts (these two parts included). This also had me looking for a supplier of 15-5PH which when compared with 316L, is vastly superior in tensile, yield and fatigue strengths. So I broadened my search and followed a recommendation from Mark at Prova and contacted RAM3D out of New Zealand. I found them incredibly knowledgeable, open to discussion and answering questions in addition to a relatively quick turn around given the tight schedule I was now on to fully redesign and manufacture another prototype before the fall was up with hopes of taking it to the 2022 Philly Bike Expo. Right from the start, I only focused on producing another prototype. If I could take it to Philly, that would be a perk, but I already had set things to rights in my mind that it would not be finished in time for Philly. That way I could manage expectations and keep things realistic as well as not become stressed about an impending due date. The point is to learn, refine and build on ones knowledge so you can always be refining your process and methodology and learn from the journey so you not only come out on the other side with a superior product but you’re more knowledgeable than when you had began. So the goals and parameters continued to be straight forward: · All hardware, bearing types and standards chosen ahead of time before starting the design process – this is critical to your design methodology. You can always change them midway but having them on hand from the start is important. · Produce a fully defined CAD model of the FS assembly in Fusion 360 · 160mm F / 140mm R travel (aka design a “bigger bike”) · Longer Chainstay length of 440-445mm up from 435mm (Running changes to front and rear center were made with V3 vs V2) · Longer wheelbase (Running changes to front and rear center were made with V3 vs V2) · Slacker HT angle (64° vs V1’s 65°) · Design around a Horst Link · Balance CNC machining with 3D printing and attempt to balance those forms with traditional round tubes · Improved cable routing · Improve clearances · Increase lateral stiffness of the swing arm assembly (This became even more of a focus with V3) · 1-2 tool maintenance on frame part maintenance · Reduce weld time and machine time on parts · Reduce distortion/alignment/post weld machining from welding by keeping welds away from critical bearing interfaces · Room for a large water bottle So back to where I had began way back in July and beyond. (A note to the reader: some of this was penned before the failure in August.) Here’s an early shot of V2 before I went back to the drawing board: This used all CNC machined parts and the part count was a tad more than I’d of liked. But when I went back and started in on the redesign, I quickly found I could begin to merge parts so 4 parts became 2 or 3 became 1. Here’s a final shot of V2 all CAD’d up: Slowly but surely parts began to emerge one by one in Fusion 360. (Which, by the way, is a joy to use.) I spent the better half of the winter of 2022 in Fusion 360 dialing in V2’s assembly which went through multiple iterations and each part went through many revisions before arriving at their final versions. I’ve been learning a lot along the way of course and having essentially 2 seasons under my belt on V1 which is a straight forward single pivot design, it allowed me to begin to really form in my minds eye the bike I ultimately want to ride but also the bike I need to build and service (we’ll get back to that in a bit). But in the meantime, I wanted to continue down the path of a slightly longer travel bike that was designed around a Horst Link. Once everything was dialed, part files were exported and went off to suppliers for quote (Lichen MFG out in Washington state for CNC). Here’s a shot of the group of refined 3D printed parts when they arrived this past fall at the shop. This was an exciting day for sure! Above, you can make out the refined shapes in addition to the lattice structures added to the internal profiles of the yoke in particular. Additionally, the dropouts and the turnbuckle received internal lattice structure. (I think the next step will be pushing wall thickness a bit with relation to lattice structure use). And after patiently waiting, parts from Lichen arrived late spring/early summer and that too was an exciting day as well! To see and realize parts and have them come off the page is a great feeling. And those same parts were used in V3. So all was not lost. And while I awaited parts from RAM3D, I also was busy making a new front triangle with refined reach and front centers. 6061 T6 shock mount and 15-5PH shock mount base all finished up: In process: Parts were printed with additional tolerances of critical areas such as this shock mount base where I drilled the holes to spec and then tapped them using traditional methods. Here’s a shot of slotting the yoke after holes were reamed to spec and tapped: And while I had been awaiting parts from suppliers, I tended to all the smaller parts that required lathe time. Here’s a shot of spacers, shafts and bolt assemblies as I’m turning them: One long standing goal of this project is parts count. This build taught me the value of efficiency in numbers. AKA parts reduction. And those parts all need to be stock off the shelf (a primary design objective). For V4, I’m definitely focusing on part counts and weight is now on the table. V1 and V2 did not consider weight – it was more of an aside. (V1 sat at exactly 30 lbs). As I get closer to the final production version, I’ll want to be more thorough and weight will be layered into that list of design goals. But this whole process has made me really respect simplicity, ease of maintenance, parts reduction and weight reduction. And for the record, V2’s part count is 61. That’s including linkage parts, the snap ring for the hanger, the dropper port, every nut, shim and shaft. That’s too many in my opinion but I couldn’t arrive at this new location without first going to the moon and back to appreciate and realize this new parameter. With this project came a whole host of new tooling too. Not just specific tooling but making additional parts that could be incorporated with existing tooling to be flexible and allow for multiple iterations. Adjustability comes to mind here! So that meant creating small improvements to the previous pivot point tooling: Adapting the BB-subassembly tool to be able to build swing arms of all shapes and sizes: And who knows how many small tools for holding small parts in lathes or pressing parts into other parts I had to design, machine/turn for this whole project: But now I have adjustable tooling for future iterations and I’ve walked through much of the process of “how” I’m building these parts and dialing in my process and methodology. For example: The above is a .625″ hole saw making a pilot hole for a 20mm finish dimension. However, the tooling below it needs to be removable (thanks to this feature) to allow clearance for the cutting tools. Here’s that finish dimension of 20mm’s: And test fit. It’s nice and tight which welded up nicely: Once the front triangle had been finished up and parts arrived from RAM3d, I immediately went to work on the new swing arm. And what a good feeling this provided. Finally, here I am at a new destination where the design is realized and improvements are met first hand after a long road of lessons learned and knowledge gained. Which brings me to a rather important aside that I need to get down in writing and that is just how important it is in your design process to make a point of understanding and acquiring an intimate knowledge of the manufacturing techniques you’re leveraging. This includes physically getting your hands dirty and working with the materials and methods you’re incorporating. Now naturally you can’t possibly take part in all of these methods (i.e. SLS or say CNC) but at the very least acquire the understanding and knowledge that you can then use to inform your decisions. I’ve been reading and hearing a lot these days regarding designers or engineers never basically working in the processes or materials they’re applying or calling upon to make the parts they’re designing. I think during initial design stages, there’s value in really keeping things “blue sky” and not limiting your ideation by considering the “how” of manufacturing but at some point, this can become an incredibly bad choice in your methodology and approach. At a given time, you need to consider manufacturing techniques, what limitations they place on your design and how you can design around those manufacturing applications to make a better part that is more easily manufactured without losing any of your design criteria. There in lies the challenge. Ignorance can be bliss, but you’ll make your manufacturing team pull their hair out if you’re only designing for the screen of your computer. And you’ll cost yourself dearly in the long term because often, its straight back to the drawing board if you’re trying to figure out how to manufacture something that was designed for the screen and not for the applicable world. So all of the parts of the swing arm were considered around the tooling I had built or was required to build and more importantly, how a part was to be held, tacked and welded in this case: A whirlwind week of fabrication and I was back to a new starting point before everything was sent back out to powder and I could get back out on the trail. However, all this time, I had rebuilt V1 and was riding the single pivot which was probably one of the most valuable things that could have happened! And this directly informed changes to V3 from V2 especially some of the attributes I had lost when I initially started riding V2. Front center was just way too long. Rear center (aka chainstay length) was too long for my taste and riding. Some of that poppy playfulness was lost and that informed me of what needed to change with V3. So all of that helped to inform decisions. So back from powder after a week of patiently waiting and the Friday I picked the frame components up, it was straight back to the shop for reassembly: Then the following morning building up V3. And a conscious decision was to keep V1 built so I could actually do back to back test runs on a known and controlled track, which I’ll get to (that really was informative and confirmed some hunches with geo choices). I had a sense of relief with assembly too. And I was finished up a week before the Philly Bike Expo. Having patiently been waiting to get to this point, another week or two wouldn’t matter so I shelved the bike to take to Philly and testing would resume upon my return: The new yoke assembly: And for all those Pinkers out there, water bottles fit fine here: A bit of detail regarding the cable routing. Keeping things clean – and yes, this was considered from the start. I did not design the bike and then decide how to route the cables… And a detail of the ISO brake mount and horst link: But on to the fun stuff: HOW did V3 and V2 ride?!? And more importantly, how did all 3 stack up against one another? First ride out, when I originally finished V2, what was very apparent about a Horst Link was its subtle sophistication over small trail chatter and small hits. With the single pivot, this was muted to a degree and parsed somewhat when it came to dialing in an air shock like the Fox X2 I’ve been running (and favoring throughout the builds and testing). But when riding V2 and V3, the added layer of a second link really starts to make the nuance of “how” these bikes ride and handle that much more sophisticated. Flipping back and forth between builds (V1 and V3) on controlled tracks from point to point testing, I discovered the single pivot (V1) was tending to sit higher in its initial stroke and travel when compared to the Horst link bike (V3) which tended to sit a tad lower in its travel. I’ve been fiddling with air pressure and sag to see if I can find a happy spot that is a bit more akin to where V1 was sitting but a lot of this also can be mitigated in pivot locations (which I’m still learning and the curve is real there!) and design in addition to shock setup. Climbing: V1 climbed exceptionally well for a single pivot. So much of what made single pivots bad way back when has been tuned out via shock design and progression over the past decade. It wasn’t a rocket, but it wasn’t a bear to climb. The same I was surprised to say about both V2 and V3. But because the Horst sits a tad lower in its travel, I’m thinking about bottom bracket height a bit more (currently 25mm throughout all prototypes) and whether I want to raise this with V4 a touch. Not a lot, but if you have slight changes in terrain height, especially climbing where you are up and over an obstacle followed by a dip, some times I’d just brush a pedal or knock a crank arm. This was virtually non-existent on V1 and hence why I didn’t change anything between V1-3 in this regard. But in the saddle or out of the saddle, V3 performed better than I expected a longer travel bike to perform. The shorter wheelbase between V2 and V3 really helped in corners and if you were out of the saddle climbing and had to pick up the front end to get up and over an obstacle. The amount of effort to get the front end up was minimized, but V1? That front end pops up relatively easily. So that’s something I really need to address and assess with the next iteration that will be V4. Descending: Pointed down hill, boy does V3 (and V2 while it lasted) soak up the hits. Not to say V1 didn’t, but with a Horst Link, I’m finding out just how much more nuanced and sophisticated the wheel path becomes and hence just how better of a performer the bike becomes in demanding terrain. But that was really what V3 was designed to do. However, if I’m being honest with myself, I honestly really preferred that poppy playfulness of V1. So that was filed away for all things regarding V4. I also found the change in head angle from 65° to 64° necessary for the amount of travel difference between V1 and V3, but for V4, I’m dialing back travel to either 140/120 or 150/120 and resetting head angle to 65°. This has been and continues to be an all around great performer and design choice to keep the platform relatively snappy and fun. V2’s wheelbase was massively long. Way too long according to my opinion, so with a few clever strokes design wise, I was able to real that front center back in, reduce reach a bit, and downsize rear center from 450 to 440mm and some of that pop was back with V3. I’d like to go even shorter on V4 however and be closer to V1’s 430mm CS length – this just seems to be a great all around length for the well rounded trail bike I’m looking to ride and build. However, still with the increased wheelbase and slack angles when compared to the Marauder, the Snakedriver just loves to be leaned and carved. Funny what a degree or two here and a handful of millimeters there will do when it comes to handling and performance. (Which, I think I need to do an extended reboot blog post of all I’ve learned and applied when it comes to geometry and handling I’ve gained from this project.) But V3 just loves to eat up hits and plow through terrain thanks to 160/140mm travel front / rear, longer wheelbase and slacker geo numbers. Its quite under control, composed and can be picked up and man-handled into and through terrain and obstacles. Both V1 and V2/3 share this, but its really apparent with V3. V1 and the single pivot sometimes will feel a bit “on the edge” when things get really hectic, but ironically I never felt like I didn’t have enough travel. In V2/V3, there have been many instances where I feel I have TOO much travel. So there’s that to consider too – but I’m coming to the conclusion that a 140-150mm fork with 120-125mm of rear travel is basically where I want to be when it comes to travel. Points in Between (aka the stuff I live to ride for): In a straight line and level trail that is relatively smooth, the single pivot just stood firm and planted and you feel relatively fast, snappy and nimble where as the larger travel V3 felt a tad more sluggish and over suspended honestly. Read its WAY more bike than the terrain I’m riding demands but when jibbing, jumping, having a fun and looking for the fastest lines, V1 and V3 both shine in this regard. V3 feels like I need to use a bit more effort in some instances but overall they’re both fun bikes to ride despite V3 just feeling like more bike than what I need. Preloading the suspension, hopping and jumping are a blast. Railing turns and leaning into them with ample weight over the front tire and the bike just hooks up and wants you to go faster. Which, last season, I actually started having some right heel drop issues late in the season. At first I thought “Ah, crap! Is some of my Lyme junk coming back?!” But I started paying attention to my riding style and when this was happening. Basically what I found was with the addition of an FS, I was ALWAYS charging and ALWAYS putting the hammer down. Basically I noticed I was constantly sprinting and over exaggerating how low I could get my body. Which meant I was putting a tremendous amount of effort into my right leg and calf. I ride left foot forward a lot, so much of my weight is resting on that right foot and thigh. So immediately late in the season, my right thigh would burn only a matter of minutes into a ride because I was sprinting to a downhill, then charging the line then right back to sprinting to the next one. I wasn’t giving any time to rest in between segments of trail. Basically I was having too much fun I suppose. Well, come the end of the season, my right leg was cooked! (Actually, in my searches I watched a great piece of tips from Aaron Gwin on cornering, body positioning and how much weight to load on both legs/feet. I naturally do what he is saying, but it was a great reminder to be aware of weight distribution on your feet/pedals inside vs outside etc. Watching that and putting those recommendations into practice and reminding myself to be aware of these things really helped honestly and I haven’t had a problem all season long this year.) But all that aside, what I’m looking for is an all around good trail bike in the Snakedriver. One that climbs and descends but lives for those in-between segments of trail where you’re jibbing, looking for rocks, roots and obstacles to bunny hop or use to boost off of and generally just have fun. That’s the balancing act I’m going to be figuring out with V4. After Christmas I’m going to start back in on V4 in earnest which will be quite different from V1, V2 and V3. It will share that same overall line choice and aesthetic but I’m kicking the idea around of changing shock orientation (vertical vs horizontal) which frees up a TON of space in the front triangle as well as looking at a flex pivot to reduce complexity, weight and make maintenance a bit more straight forward as well as support if anything should require replacement. And maintenance and upkeep are high on my list of priorities. A lot of what you don’t see throughout all of this process is all the small considerations. Part of the time spent is just nailing down torque specs, maintenance routines, upkeep and thinking about what is important for the end customer. Basically I need to really do my homework on this one so customers are well supported and have a lot of freedom to maintain their bikes without having to deal with proprietary hardware. And many want to know when this will be ready. I’m being incredibly thorough, taking my time and attempting to try and leave no rock left unturned. The last thing I want to happen is to release this platform and suddenly have to issue a recall or advise customers on existing bikes for some detail that was overlooked. So the answer to the “when will it be ready” is simple: It will be ready when its dialed and not sooner. So thank you one and all for your patience and your excitement. I’m just as excited as you are but I tend to move slow and methodically with new designs. For those of you that would like to see the entire build set, here’s V3’s linked here start to finish. So lots more images than are posted and shown here.