Its normally not well documented, so we decided to share our journey in a ground up, hands on development of a production electric skateboard.
Come on a ride with us and learn what it takes to be different.
Why create our own board?
In our opinion most electric skateboards currently on the market are based on more than 20 year old longboard technology, basically things that were never designed for the demands of high performance e-skating.
We often see other brands copying each others copies of traditional longboard tech with largely cosmetic treatments and only minimal technical improvements, leaving most of the industry sadly behind the times.
Why do we care? The answer is actually very humble – we're just addicted to the free feeling, adrenaline-on-tap, anti-depressant machine that a high-performance electric skateboard can be. We want to maximise that high as much as possible, milk it for all it's worth. We’ll go to great lengths to achieve it, as you’ll see in this blog series.
The Brief
Our road to a high performance, next level e-board is as follows:
Essentially we wanted to create a platform which could be highly customised to suit each individual rider. Choose your battery, deck, motor size, ride stiffness, truck width, thane or pneumatic wheels.
Go from a lightweight shop run board to a long-range missile. Carve like a surf skate or break the sound barrier. One board to do it all.
Flexible or rigid deck?
The first problem with motorising a skateboard is staying attached to it while riding. At speed a very stiff deck quickly becomes uncomfortable with repeated flexing over bumps and other obstacles. Some amount of flex is necessary.
However there is a common trait with decks that are flexible, and that is they don’t have much drop, concave or W. Which is a problem since you need those to feel locked in when moving fast.
Once you start adding shape to a flat surface it loses its ability to flex, hence steel roofs being corrugated to stop flex. A flexible deck also has the issue of requiring a flexible battery and enclosure, which take up a lot more space than a rigid system.
So instead of choosing to go with a flexible flat deck, or a stiff contoured deck, or a stiff flat deck (disgusting), we made an early decision to have a stiff enclosure which allowed for the swap-able contoured deck. We knew we needed to give it the ability to flex somehow, but we didn't know exactly how we'd do that yet.
Soon we learnt that would entail building an electric skateboard in a new way which has never been done before.
Material Selection
Developing a new way of building electric skateboards calls for a difficult decision: the materials it will be made from.
WOOD
The majority of boards on the market today are based around a wooden deck. However, to achieve the modular and compact design that we wanted with a deck that has concave and drop, it became apparent that wood was a poor choice due to the amount of thickness required to make it stiff, as well as the limitations of its ability to conform to complex shapes.
METAL
While not an obvious choice at first, metal does actually have some advantages. While it probably wouldn’t be suited to making the deck itself, an enclosure/structural chassis that the deck bolts to could certainly be made from metal. The Stooge Race Board is a great example of a structural chassis made from steel. This had us investigate aluminum frames, with higher stiffness to weight than standard steel grades. The material itself is quite inexpensive compared to carbon fiber. However if you want to form metal into complicated shapes then it starts to become quite expensive. There's also the need for plastic or fiberglass body panels and additional water proofing which all add to cost, complexity and weight.
CARBON FIBER
Composites such as carbon fiber are extremely versatile in their ability to form a variety of shapes. They are light weight, extremely strong, and would enable us to create very thin and rigid structures in order to utilize every millimeter of space available to hide the battery and electronics. And although the raw material cost is more expensive than wood or metal, composites allow us to simplify the design and assembly of the board whilst ticking all the boxes in terms of stiffness, function, and aesthetics. So for this application it won over other material choices.
Outsourced or In-House?
Initially we thought we would outsource prototyping and production to a local carbon fiber manufacturer. This would be very expensive and basically give us one shot at getting the design right - a unique design which has never been tested before. So we made a tough call and decided to develop a carbon fiber Radium enclosure and deck in-house with no prior experience of working with composites.
We believe the e-board industry is behind the times, and that a superior electric skateboarding experience can be created with modern, purpose-built components developed in-house from the ground up. It requires passion, determination, and a little insanity… but we’re not here to fuck spiders.
NEXT UPDATE Developing a suspension system like no other.
There are quite a few designs available that soften the ride by emulating cars with a full suspension system. Using control arms with ball joints, steering linkages, and a variety of mechanisms with lots of moving parts, these are everything we are against – complicated, heavy, fragile, high maintenance, and non-skateboard-like handling.
We came up with the idea to make the ends of the deck where the trucks mount into a separate component to the rest of the board. Able to swing up and down, like the rear suspension of a motorbike. This allowed us to consider the enclosure and deck in different ways.
We wanted a hinge point, mounted as far from the trucks as possible in order to keep the trucks somewhat level when hitting bumps. Otherwise this could potentially cause instability - when hitting a bump the tip of the deck would angle up, increasing the truck base plate angle which provides more steering, but less stability.
One of the biggest issues with making a compact and simple suspension system is the shock absorber. It's very difficult to find ones which are small and light enough for this application, with mountain bike shocks being the most common, and scooter ones only slightly smaller, less common, and frankly still too large. Spending the money and time required to develop a custom tiny shock absorber was not a path we wanted to go down. We believed it would still be too large to mount perpendicular to the swing arm in order to resist the arm movement.
Unless a cantilever linkage system was created, directing the force towards the enclosure and allowing the shock absorber to be mounted horizontally…
And so we came up with a design to test the concept with mostly guesstimated geometry. A basic prototype was machined on our Tormach 1100M CNC milling machine. For this test we used skateboard bushings as springs, with the ability to adjust the spring rate just by using different shape and hardness bushings.
Unfortunately it failed miserably. The first step on the “deck” (a plank of wood) sagged to the ground immediately with not even half the amount of an average person's body weight. The bushings didn't move so much as all the components around them just bent and distorted. But it was a start.
From this concept we learned a lot. Firstly, cantilever systems put a lot of force through components, and are too complicated for what we wanted to achieve, breaking our first defining rule.
The most important thing we learned here was – it was OK to just use skateboard bushings instead of expensive and heavy shock absorbers. They are light weight, readily available in all different shapes and sizes, simple, cheap, and super compact.
With lessons learned from the first prototype, we wanted to take advantage of skateboard bushings as shock absorbers. The solution we landed on was much more simple and robust.
It seemed to work on the plank, so we took the next step and acquired a second hand Landyachtz deck, chopping off the bits off we didn't need.
This thing was so much more awesome than we were expecting. A relatively dodgy concept prototype assembled with scrap parts and a hammer, but with such a smooth ride it was almost a daily for over a year!
For some reason the board just handled better than anything we'd ridden before.
The added shock absorption kept the deck always pressed against our feet and the way it carved was extremely satisfying once the right bushing combo was found. The suspension bushings actually affected how well it carved.
The most important finding of this test – the suspension system did not take away the experience of riding a “skateboard” and turn it into something different. It still handled just like a skateboard.
This design has one major issue – mounting it takes up a large amount of space on the deck where batteries and motor controller would normally be sitting. So to have a shock absorption system like this would mean we’d be restricted to a much smaller battery, or build a bigger board.
But compromises suck and the eskate industry is already full of them. We thought hard and came up with a new way of building an electric skateboard. Mounting a shock absorption system directly to the ends of the enclosure as opposed to the deck makes the enclosure the structural element carrying all of the weight. A lighter deck would sit on top and the battery size would not be compromised. The deck could easily be removed for internal access while still on all four wheels.
The result was a prototype "shock mount", a compact and simple way of adding shock absorption to a rigid structural enclosure and able to fit a large battery with an overall slimmer form factor.
NEXT UPDATE – Making the Enclosure and Deck Molds
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Once we had our initial concept enclosure and deck fully modeled in CAD, it was time to take our 3D model from the computer screen to a finished carbon fiber part for prototype testing.
For this you need a mold. The process of making a mold seems simple. You can either make a mold directly which is just a smooth surface in the shape of the outside of your part, and the composite material is laid directly into it, or you can make a plug/pattern/blank which looks like the final part, you then form a mold around the plug to create a negative pattern, and this then becomes your final mold/tool which you lay the composite into to create a clone of the initial plug. If you are confused imagine the conversations we were having at the beginning about plugs, patterns, tools, blanks, molds, negatives, positives... So to help understand here is a quick summary of terminology:
Our plan for the boards construction at the time was an enclosure with a big internal overhang, which would have a flat 2D lid screwed on top of it to seal the enclosure off, and then there would be a thin single piece carbon fiber deck bolted on top, with custom shaped plastic or urethane blocks supporting underneath each bolt, because adding a curved deck with concave and drop to a flat enclosure would leave lots of gaps in-between. To make the deck we would directly make the mould/tool for the carbon fiber to be laid into to form the finished parts. However the enclosure was more complicated due to having an internal overhang which would require a two piece mould to release it. So we decided the enclosure would first have a replica plug made, and then we would use that plug to make two moulds/tools which bolt together for the layup and then unbolt to release the part. The reason we didn’t decide to directly make the two tools for the enclosure at the time was because we thought getting two separate hand finished tools to align to each other without a seam would be difficult, and a plug could be used to form both tools from the same hand finished part.
Attempt #1
Our first attempt at the enclosure plug was a solid piece of MDF wood which is soft and easy to shape. The idea was to shape it by hand into the approximate shape of the CAD model, to fast track bashing out an initial prototype of our chassis so we could start testing the concept. We successfully shaped the overall bulk of it, however when it came down to the fine details our skills ran out, so we gave up on that approach.
Attempt #2
Plan B was to 3D print the plug out of plastic (PLA) filament, and then sand the printing defects smooth. Due to the limited bed size of our FDM printer (Prusa i3 Mk2), we had to print the part in 4 sections which were glued together. After a few days and kg’s of filament we had 4 separate pieces which would form our first plug.
Once the four separate parts were printed we glued them together using standard Araldite epoxy. This gave us a plug that roughly resembled our design but there were a number of issues. Firstly the bed of the printer was not perfectly flat, and during the print the parts also shrunk at the corners. We also found that the pigment used to colour the filament had quite a large impact on the way the parts printed, leading to more discrepancies. This made the 4 separate pieces not line up naturally, so we had to use a straight edge during the gluing to align them which left some gaps between the prints as well as some misalignment that we would have to try and sand smooth.
However when we first started sanding it quickly became apparent that PLA 3D printed parts are surprisingly abrasion resistant and don’t sand easily. So we started looking at the options available to build up the surface instead of removing it. It was really important that we not just correct defects but made the whole surface extremely smooth and slippery with no 3D print lines that could mechanically lock into the tool. We ended up trying a high build spray-on primer which helped but not as much as we would have liked because we then ended up having to deal with 3 different hardness materials that we were sanding which is the 3D print (hard), bog (softer), and the high build primer (very soft). This coupled with the fact that the 3D prints were so uneven made it very difficult to achieve a consistent surface.
(photo shows a mishap where the plug was left partially sitting in the sun near a window on a hot day, causing the print to melt and forcing us to go through the steps all over again.)
After we did our best to make the surface smooth we had a sheet of polycarbonate plastic waterjet cut to create an accurate divider that would create a parting line along the edge of our plug where the first half of the two part mould/tool would be formed with a flange that the other half could bolt to. Unfortunately while our fancy waterjet cut piece of plastic was super accurate, the 3D printed plug we made was not and so some decent gaps had to be filled. We scratched our heads for some time on how to go about filling those gaps. Initially we tried plasticine but ended up discovering a wonder-material called filleting wax which is far superior. Its quite amazing how compliant and formable filleting wax is and this allowed us to easily fill the gaps between the polycarb sheet and our plug.
The last step was to apply a release agent to prevent the resin from bonding to our plug. We overlooked this step and were too eager to lay up some fiberglass, so we read on the internet that Vaseline can be an effective release agent and proceeded to apply a coat of it to the plug.
Finally, it was time… We dug into our box of composite goodies not remembering exactly what we ordered since it had been so long already since the start of the project, and began chopping things up in preparation for the layup that would form the first half of the mould/tool. This included what we thought was a fine gsm plain weave fiberglass (but was actually nylon peel ply fabric designed not to stick to resin), as well as release film, breather cloth and vac bag.
We mixed up some polyester resin (we used polyester and fiberglass for the tools to save cost), and with paint brushes we placed our first piece of “plain weave fiberglass” onto the plug and proceeded to wet it out with resin, then repeated with a few more layers. It quickly became apparent how difficult the triangular pockets were going to be to work with as the fabric just wanted to drape over them, causing voids at the corners. So at this point we decided to add the release film, breather cloth and vac bag and see what would happen after we pulled a vacuum and let it cure for 24hrs.
The result actually looked pretty cool (and believable – we still had no idea it was nylon peel ply we used), but it was obviously super flexible as we could tell by trying to lift one of the corners. So we got out the heavy 600gsm plain weave fiberglass and added some additional layers ontop before we tried to release the part. We placed foam ribs between the layers to bulk up the part to make it more rigid and we really had a hard time getting the fiberglass to conform around the foam due to its thickness and inability for plain weave to stretch. Here you can see how it looked after curing:
We had a successful release from the polycarbonate sheet, but unfortunately when we tried to remove the 3D printed plug not only had the resin completely adhered to it, but even our efforts to remove the plug by destroying it resulted in the nylon peel ply layers doing their job and separating from the surface.
A complete failure resulting in an unusable mould and total destruction of the plug.
Attempt #3
We decided to have another crack at 3D printing the plug as this was going to be by far more cost effective than other methods. This time applying everything we had learned from the previous attempt.
Significant refinements were made to the 3D print settings and the same red PLA filament was used for all 4 pieces, this time a far better surface was achieved with much better tolerances that would save a heap of work in the steps ahead.
We got mad trying to sand all the tiny detail lines and pockets we designed into the parts so we just filled them with bog to get rid of that problem. We upgraded to a proper primer designed for this application called Duratech Surface Primer, which was much more effective at filling the 3D print lines and could be sanded to a really nice smooth finish with a lot less effort.
In the background can be seen our attempt at also 3D printing a single piece deck mould/tool directly.
Once we applied the surface primer to the plug and let it set, it was sanding time. If you’re not familiar with refining surfaces, the process is quite tedious and time consuming. 120 grit had already been used to rip through the bog underneath and achieve the overall shape, so we moved up to 240 grit on the softer primer to not burn through it too quickly or leave deep scratches. We then went to 400, the goal is to remove all the scratches from the last grit each time we go up a level. Next was 800 and lastly 1200 at which point the surface was feeling extremely smooth.
After that we decided to go one further step and rubbed a cutting compound into the surface which effectively works like even finer sandpaper. We then had to seal the surface (TR Sealer Glaze) because the primer is still porous meaning resin could soak into it. The sealer was applied with 2 coats and then buffed smooth and following this was several coats of TR Honey wax which is a proper mould release agent. Unfortunately we did not know that you have to buff the wax off before applying the next coat, so we ended up just smothering 6 coats of wax into each other.
We used the same technique as last time with a polycarbonate sheet and filleting wax to create the flange for the first half of the mould and during the layup we used real fiberglass this time! But unfortunately we only had 300gsm plain weave so it still didn’t want to conform to our part and we decided to add relief cuts to the fabric during the layup to help the plain weave conform without leaving cavities. We used a lot of layers of the heavy 600gsm ontop of that and then applied the release film, breather cloth and vac bag.
24hrs later anddd boom – we had a successful release! (sorry no photos were taken).
But the surface was shit.
There were so many pinholes and voids where air pockets got trapped or the glass bridged over a corner, despite pulling quite a strong vacuum on the part. The good news is that our plug was mostly intact and with some light touching up (ok we completely sanded and resurfaced it) it was ready to go again.
This time being many youtube videos wiser we had some new ideas on how to go about the layup. Firstly we ditched the stubborn plain weave and opted for chopped matt fiberglass instead which not only conforms far better but is significantly cheaper as well. Secondly we sourced a polyester gel coat resin, which is basically just thicker and what it allows you to do is paint on some layers of resin to the surface and let it partially cure before adding the fiberglass on top. What this does is ensures the surface of the part is free from air bubbles, reduces finer details, and provides a tacky surface that the first layer of fiberglass can stick to so it can be finessed around the finer details of the part and stay put.
We also learned how to use the TR release wax properly, which is to allow the wax to glaze over and then buff it back to a smooth surface with a rag between each coat, until 6 or so coats were applied.
After another layup attempt the resulting finished mould/tool was infinitely better although there were still some issues.
While the gel coat provided a perfect surface in some areas, other areas had these strange ripples, and we still had voids around the sharp corner where the flange meets the plug, with the very thin layer of gel coat just collapsing into the air pockets behind it. After much research we learned that we simply needed more layers of gel coat and more time for it to cure before starting the fiberglass layup on top of it (4 coats allowing each to tack off before applying the next works well), along with being more careful not to disturb the gel coat layer with too much movement during the layup.
Unfortunately though that was the least of our problems. When we removed the vac bag and the polycarb flange, the release agent was so good that the plug just popped out of the mould, and it wouldn’t go back in the same way. It was as if the mould had internal stresses that caused it to warp to a slightly different shape, so the plug didn’t sit right even with a lot of pressure on it, and it was basically not possible to get it to register back into the mould for us to lay up the second half of the two piece mould and get an accurate seam around the part.
It was at this point we realised we had just put too much faith into the accuracy of a multi-piece 3D printed part and this plug/buck method of making the tool.
And that was the last straw. It was all or nothing this time. We had a CNC milling machine sitting behind us laughing at our futile attempts with 3D prints, so we abandoned that method and went all out with attempt #4 which will be covered in the next part of Developing the Radium board.
]]>During that process we decided it would be best to commit to making proper tooling with our Tormach 1100M CNC milling machine, even though each mold would have to be broken up into 4 individual pieces to fit in the machine, with 4 molds (16 pieces) in total.
This changed our approach to making the plug/pattern for the enclosure of the board. Due to the inaccuracy and slowness of 3D printing for large objects we initially tried to make a replica plug of the enclosure, adding a flange afterwards from which the top and bottom half of a two piece mold would be formed. The idea behind this was that after laying up the first half of the mold onto a plastic flange around the part, the flange could be pulled off and the second half of the mold could be laid up directly onto the first half to ensure both sides meet up in the middle perfectly with no gaps. But despite our efforts this method didn’t go well, so this time we took advantage of the accuracy of CNC machining and made two completely separate plugs with a flange already built into both sides – one plug for each half of the two piece mold that would form the enclosure of the board.
The deck had some major design updates as well. We went through many ideas for how to make the decks, from single sided parts with foam cores, to honeycomb cores sandwiched between two layers of carbon. The issue we were having is that carbon fiber parts usually have an accurate cosmetic side that is produced by the mold, and a rough uneven surface on the back from vacuum bagging, but we needed both sides of our deck to have an accurate surface.
We are stoked with the design we landed on in the end – two separate pieces of carbon fiber, with the underside piece including wavy patterns to add stiffness. These two parts are then glued back to back, so both outer surfaces are accurate and smooth. A urethane bumper gets glued in around the perimeter, so the deck is thick but hollow which not only makes it comfortable to hold but significantly reduces weight, enabling the finished deck to weigh just 1kg.
To machine the molds we needed a base material to mill down into the final shape, which had to be sturdy and easy to sand smooth and seal, as achieving a totally smooth surface with a milling machine is just not practical. We decided to use epoxy tooling board, because even though it was significantly more expensive than MDF, it’s a much better material for making molds as it can retain fine details and is very rigid and stable, whereas MDF has a tendency to warp with moisture and internal stresses. However we did use MDF to make the mold for the urethane bumper as it was a simple 2D shape with no need for accuracy.
One of the most difficult parts of CNC milling is holding the parts, and we benefited greatly from the tooling boards strength here, by drilling 3 holes and tapping threads into the tooling board itself we were able to just bolt the blanks to a block of aluminum that we’d clamp in the vise, allowing all edges to be machined away without the cutter colliding with a clamp.
The molds had to be split into sections in CAD, and using the same software (Fusion 360) we created the tool paths to tell the machine how to go about removing the material, including deciding how rough of a finish to leave. The smoother the surface, the longer it takes to machine and it gets to a point where super smooth takes so many hours to machine that its faster to sand it by hand, so we landed on a finish that took around 2 hours of machining for each of the 16 section.
We used 3 tools – two different sized ball end mills for finishing, and a high speed steel 2 flute square end mill to rough out most of the material, which we experienced problems with. The tooling board basically turns to dust as its machined away, and we think the dust created a lot of friction and abrasion, causing the high speed steel cutter to heat up and go blunt after just a few hours of machining. The effect of this was that the pressure from the dull cutter caused the tooling board to not just machine away nicely, but instead it would break off in chunks, causing more material to be removed than was intended.
So to address this we used a constant air blast on the cutter to remove excess dust (causing it to end up on absolutely everything in the workshop) in order to keep the cutter cool and minimize re-cutting of abrasive particles which greatly extended tool lifespan. We also optimized the tool paths to only cut in certain ways as to not create thin sections that chip away.
After rough shaping with the 2 flute square end mill, a 12.7mm ball end mill is used to achieve the final shape and surface finish.
A small 3.17mm ball end mill then reaches into the tighter corners to remove the last bits of material that the 12.7mm couldn’t reach.
After this I vowed never to machine tooling board again, as not only were the entire contents of the workshop covered in fine dust, but the Tormach was so caked up with tooling board that it took 2 days to fully clean.
But it got the job done, and after a week of late nights we had all the individual pieces ready to be glued together forming the final molds.
There were still some chunks taken out on some of the parts before we got on top of that issue, and we just filled those gaps with bog.
After correcting any defects we sanded the surface smooth by hand, working our way up from 400 grit to 1200, and then applied a cut and polish.
After this we had a very smooth surface but still technically a porous one, meaning that resin can soak into the tooling board and bond to it. So to address this we used a product called TR Sealer Glaze, applying 2 coats and buffing them back to ensure the surface couldn’t absorb any resin under vacuum.
But epoxy is sticky stuff and sealing the surface alone won’t stop it from adhering, so we also applied 6 coats of honey wax mold release agent, placing the molds into our homemade curing oven to dry the wax faster before we had to buff it back between each coat. This still takes a while when you have to do 6 coats across 4 different molds.
At this stage we had two molds for the two piece deck ready to go, as they are already negative molds that we can lay the carbon straight into. However the enclosure molds were still technically a positive/plug that we needed to form the two piece fiberglass mold that we would use to lay up our carbon fiber enclosure, so we will go through that in the next part of Developing the Radium board.
]]>There are lots of different methods for making composites, but some of the most common ones are:
We quickly ruled out wet layup with no vacuum because our parts are fairly complicated and need pressure to conform to the mold. We also ruled out pre-preg due to not having an autoclave (expensive highly pressurized oven), and out of autoclave pre-preg since it can be difficult to achieve a good surface with it, and our molds were not rated to the temperatures required for curing pre-preg. We also didn’t want to over complicate things with vacuum infusion, which requires more equipment and consumables.
So we decided to go with wet layup + vacuum. Next we chose the carbon fiber we would be working with, which comes in different weaves and weights. We initially bought some thin twill weave for the surface cosmetic layer since twill is stretchy and great at conforming to different shapes, and some thicker UD (uni-directional) weave for the backing layers.
UD weave has all of the carbon fiber strands running in just one direction. This would allow us to create a bias of strength in one direction, since carbon fiber is only strong in the direction of the strands.
However we quickly learned during our first layup that unidirectional sucks and carbon fiber is much harder than it looks in the videos. We found that the UD weave just does not conform to the part. You’d push it down it’d pop back up again due to the stiffness of the strands. The resin (epoxy) also has very little tack to it and doesn’t really help the carbon stick, if anything the resin is more of a lubricant keeping everything slippery.
Nevertheless we placed a few layers on top of each other, painting resin on with a brush for each layer, and instead we worked the layup into the corners of the mold after we had vacuum bagged it, hoping that would be enough to push the carbon where it needed to go.
It wasn’t.
We also were able to tear some of the UD strands away from the back side of the part, with the carbon filaments feeling dry like they had no resin in them. From this we learned that carbon fiber does not absorb resin as readily as fiberglass, and would require a better technique to wet it out fully.
After that we ditched the UD weave and opted for a heavier twill instead for the backing layers. For the next layup we used 1 layer of 300gsm twill for the surface, and 2 layers of 600gsm for reinforcement. The lighter 300gsm weave is more flexible and conforms better to the tight corners of the mold,, but using a heavier weave is more cost effective to build up the total thickness required to achieve the desired strength of the part.
We previously placed the dry fabric onto the part and wetted it out with a brush, but this time we laid the fabric onto a large flat surface and used a squeegee to work a large amount of resin into the fabric and repeated for the other side before placing the already wetted fabric onto the mold.
This yielded significantly better results. Far from perfect, but enough to work with for initial prototypes.
The next challenge was the enclosure. Man, what a nightmare.
We used 9 layers for the first layup, with some layers of the weave running at 0/90 degrees and others at 45 degrees for torsional stiffness.
We found that pre-cutting reliefs to help the weave conform to complex shapes just makes the carbon a pain to work with, because it likes to fray apart. So we decided to cut the reliefs for the enclosure after we had laid all the fully wetted fabric down, and then had to fold 9 layers of heavy carbon back onto itself, which technically makes 18 layers where they overlap…
Then we had to put the lid of the mold on top without getting any carbon pinched in the flange, and install 18 bolts while the resin was starting to set (~45 minute working time), shove the release film into the sticky mold with sticky hands making sure its pushed all the way into the corners that fingers can barely reach, then do the same for the breather cloth, having to use tape to keep it in place. The breather cloth also has to wrap around the entire mold so the sharp edges and things like the bolts didn’t pierce the vacuum bag. Then we had to slide the vacuum bag tube over the mold and also stuff that into the inner corners. We’d then pull a vacuum, and really try to work the carbon into the corners of the mold by pressing hard with our fingers. Its very easy to have the vacuum bag or release film bridge across a corner, which would cause the carbon to pull away from the mold and leave bubbles or voids.
The results were actually a lot better than anticipated (total disaster was anticipated).
Not perfect, but usable.
The next stage was to trim the excess material from the parts. We used a band saw as well as a Dremel for the enclosure.
For the deck we waxed the finished carbon pieces and laid up a thick fiberglass template onto them, then removed the templates after curing and had it waterjet cut to the exact shape of our deck. This way we had fiberglass templates that would perfectly key onto our parts for tracing the deck shape and drilling the mounting holes accurately.
The next step was to glue the two halves of the deck back to back with more epoxy. A urethane bumper was also glued in at this step, which was trimmed afterwards.
We had great difficulty with the final step of shaping the deck after it was bonded. We tried lots of things, such as different ways of using routers to shape the edge the same way wooden skateboards are done.
We had the most success with stone grinding, however on first attempts we were too aggressive, causing the urethane to tear, and the curvature was made freehand – very difficult.
This still resulted in a finished totally usable deck, weighing just 1.1kg.
We refined the grinding process on the next deck we made. Using a shaping stone to make a curved grinding wheel, with a grit better suited to soft urethane, and improved our technique. We’re pretty happy with the result.
In the next instalment we’ll make the new suspension system, put some wheels on this thing and try it out for the first time.
The lessons learned from the first successful push board prototype were applied to the new electric suspension design and after a week of creating the milling tool paths and tedious machining it was finally ready to put to the test:
An immediate issue was that the deck was sitting too high above the trucks so we ended up making new suspension arms that dropped the deck down lower.
We were really excited at this point and the first test ride as a push board was very promising!
Check out the first test ride here – https://youtu.be/OTZybAHkA4k
An issue noticed while riding was a lot of fine vibration resonating through the stiff enclosure like an acoustic guitar chamber, so we added 9kg of steel weights to simulate a battery and electronics which saw that issue disappear entirely.
To make sure there was no immediate design flaw we rode the board off a 1ft ledge around 10 times with the steel weights which appeared to be no problem so we proceeded to electrify it.
Watch that test here – https://youtu.be/_graBY9akJ8
A small 5Ah 12S Li-Po pack and MakerX DV6 motor controller were initially used with some old Torqueboards 6355 motors, Torqueboards 218mm Caliber based trucks and an old set of our first gen motor mounts.
This board was named “XP1” for experimental prototype 1, and despite having a range of only 10km this thing was awesome. We were really happy with the feel of the deck and the way it felt to ride considering the primitive trucks that were on it.
Much experimentation was done with different bushings for the suspension (since regular skateboard bushings are used). Changing the duro, shape and formula of the bushings all have an impact on the way the board rides. A softer setup feels more attached to the road but more floaty and “lazy” handling. Taking the bushings out completely and replacing them with solid plastic to simulate not having any suspension creates a harsh, unpleasant and jumpy ride considering how rigid the whole chassis is. Personally I find the sweet spot to be in the middle with tall cone bushings that provide a nice linear compression, and then I just tighten or loosen the nut if I’m finding a particular trail too bouncy for example. It was certainly very interesting to play with and had me always very excited to go for a ride after tweaking something.
In the next update we make upgrades, build XP2 and iron out all sorts of issues.
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