RIPPERTON
⚡ Regular
Should just copy my battery design (Rippy Scoot)
Dont compress the cells, give them 1mm gap.
Dont compress the cells, give them 1mm gap.
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CRF #2 - 250R - LGX P41A 20s1p - EM200
- Thread starter bananu7
- Start date
I appreciate your response.
All the elements of my design stem from tackling practical problems.
Compressing the cells has been shown to reduce their chance of swelling and improve the lifetime performance. There's a link to a paper analyzing that higher in the thread.
Not having a carrier but just bolting everything together means it's much harder to prevent chaffing and movevent inside of the battery. Mine isn't going into a scooter that will roll on smooth pavement, it's going into a dirtbike where it will experience constant harsh vibrations and large g-forces. I want to take all of that away from the cells themselves, and suspending them in a carrier means i can do just that. I can all by eliminate flexion of the electrodes, rubbing of the cells against each other and the enclosure etc.
This also seems to be a common practice in industrial designs which those cells have been designed for in the first place. In there, each cell is glued to a plastic carrier with appropriate spacing and then the entire stack is compressed together. The electrodes are often welded, of course, but there's still no movement of them because they rest on the edges of the plastic carrier plates. I tried to strike a balance between a fully professional design and something that I can fabricate myself. I do not consider the protection elements optional.
P.S. I would probably try to wing it more if the bike wasn't going for sale. I definitely wouldn't want to hand over an unsafe battery, so I'd rather overkill it a bit.
P.S.2. I've just realised the positive busbar line is a perfect spot to put an internal 500A fuse which I didn't have space for in the battery for #1.
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Nice build! How thick are these plates? I'm in the same situation and do NOT want to use the wobbely LK mounts.
If one would mill the hub down 1mm, so the sprocket sits inwards and also would mill the motor mounting tabs 1mm aswell, do you believe, that placing the mount on the outside coule be possible?
I found a source locally. AFAIK they're still available, but require pickup in person. It's a very much "while supplies last, don't ask too many questions" kind of situation
I'd offer to get them for you but i need to actually build the battery and verify they're up to spec, which will hopefully happen in the coming winter months.
6mm. Forgot which alloy specifically. They're way stiffer than 3mm stainless sheet at least by feel. 5mm would likely be okay as well.
I'd personally avoid modifying the hub like that, as that means, for example, that the chain slider would be offset. I think it should be possible to get the plate on the outside and somehow make it all fit. Might require grinding of a bit of bottom frame welds, maybe a bit of the swingarm and optimizing the shape.
That being said, my #1 bike has been running the entire season with the inside mount with 0 problems whatsoever. I was initially cautious as well, but this part of the build has literally been the least problematic once put in place. I didn't have to check/tighten anything not even once, everything seems solid, so in my opinion modifying the motor is the easiest way to solve this particular problem and stay within the limits of this particular frame.
P.S. I also just realized that i have contradicted myself a bit, considering that the #2 does have a different hub, with the Kawasaki wheel and all... So maybe that's not such a bad idea if all you need is like 1mm. The OEM hub isn't very thick in that area though and they do crack around sprocket mounting bolts, so I'd be very careful. I'd probably try cutting a custom offset sprocket before attempting to modify the hub, actually. If you have a hobby CNC, that's a totally doable process, and perhaps even easier in a way than milling the hub evenly.
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RideAlongMechanic
🧲 New user
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- Apr 27, 2022
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Nice Choice on the build. I also Just picked up a crf 250 to build. I was evaluating pouch style cells, but struggling to fit them in the frame via 3dmodel. Do you have an estimate on the overall dimensions yet?
Also there are couple 3d scans out there of the CRF frame, it has been helpful for my research/layout. A cr500 conversion scan exists on grabcad. Front motor mount and y are modified from the crf250 to fit the 500. and another on the electric motorcycle builds facebook page for a battery cage design.
Also there are couple 3d scans out there of the CRF frame, it has been helpful for my research/layout. A cr500 conversion scan exists on grabcad. Front motor mount and y are modified from the crf250 to fit the 500. and another on the electric motorcycle builds facebook page for a battery cage design.
Yeah; the dimension of the pack including the BMS on the side suggest it will all barely fit. I'm currently working on other parts so the battery is paused, but will get back to it next.
I have been a horrible builder lately, with no updates. The main reason was that I did way less than I planned to over the winter. I wanted to have the #2 bike ready for the season, and it's still far from that.
I am fighting my analysis paralysis by trying to make steady progress on one part right now - the airbox/electronics holder. I went through many design iterations, especially in the digital realm:
I tried Blender, Solid Edge and new to me Plasticity. I worked from 3D scans, surfaces, solids, triangles... I ended up with a model i liked and tried preparing it for a printer, which was very disappointing (would use too much plastic, wouldn't fit/would need complex splitting that took me a lot of time, would take forever to print).
I suppose maybe posting about failures isn't that bad either? It's not always the first thing that works.
Anyway, I went back to physical sculpting. I dug out my old model with half of the old airbox embedded in the foam. I started using a different filler (much softer), I started using scraping, planing, shaving and rasping instead of sanding (which means foam and filler flakes instead of dust, much better). And it's actually going kinda okay? It was a lot of a psychological barrier where I felt it was going nowhere, so i had no motivation to keep working on it. Now that I kinda realize all models look like shit in the middle stages and stopped caring, I can actually make meaningful progress. And it turns out I'm way better at shaping by hand/by eye than on the computer screen.
Because i made it narrower on top, I'll actually need a split mould. I'm not very happy about it as it's going to be my first time using ez-mould, and adding a split makes it all more difficult, but i feel i have all the theory i need for this. I might need to buy some glass microballoon filler and some gelcoat pigment though.
This part is very important for the bike because it'd allow me to prepare almost all of the wiring (except two final wires going to the battery) and make it functionally complete, sans battery. At the same time, I plan to make at least two copies and put the second one in bike #1, but that might get a bit more complicated - go to thread #1 for more details.
I am fighting my analysis paralysis by trying to make steady progress on one part right now - the airbox/electronics holder. I went through many design iterations, especially in the digital realm:
I tried Blender, Solid Edge and new to me Plasticity. I worked from 3D scans, surfaces, solids, triangles... I ended up with a model i liked and tried preparing it for a printer, which was very disappointing (would use too much plastic, wouldn't fit/would need complex splitting that took me a lot of time, would take forever to print).
I suppose maybe posting about failures isn't that bad either? It's not always the first thing that works.
Anyway, I went back to physical sculpting. I dug out my old model with half of the old airbox embedded in the foam. I started using a different filler (much softer), I started using scraping, planing, shaving and rasping instead of sanding (which means foam and filler flakes instead of dust, much better). And it's actually going kinda okay? It was a lot of a psychological barrier where I felt it was going nowhere, so i had no motivation to keep working on it. Now that I kinda realize all models look like shit in the middle stages and stopped caring, I can actually make meaningful progress. And it turns out I'm way better at shaping by hand/by eye than on the computer screen.
Because i made it narrower on top, I'll actually need a split mould. I'm not very happy about it as it's going to be my first time using ez-mould, and adding a split makes it all more difficult, but i feel i have all the theory i need for this. I might need to buy some glass microballoon filler and some gelcoat pigment though.
This part is very important for the bike because it'd allow me to prepare almost all of the wiring (except two final wires going to the battery) and make it functionally complete, sans battery. At the same time, I plan to make at least two copies and put the second one in bike #1, but that might get a bit more complicated - go to thread #1 for more details.
I have finished sanding the pattern for the airbox. I have a photo somewhere but it's nothing spectacular, the same but smoother. I ran into a huge bummer though. When getting ready to put the pattern coat on, I realized my entire, new, 5KG can of PCP (Pattern Coat Primer, not the drug) has gone bad through the winter freezes... Super annoying.
I already have a new can on its way to me, along with a fresh batch of MEKP. I'm determined to get this to the finish line. Meanwhile, bike #1 is getting a bit more complicated, so check that thread too.
I already have a new can on its way to me, along with a fresh batch of MEKP. I'm determined to get this to the finish line. Meanwhile, bike #1 is getting a bit more complicated, so check that thread too.
The pattern has been coated with first layer, sanded and the 2nd layer is curing as I'm writing this. The oven is working splendidly, keeping 21+/-2 degrees C inside. Photos are straight after curing of the first layer, before sanding. I've added a lot of thixotropic silica powder to make it denser and allow me to put it thicker in places where it could be helpful. It wasn't a very good idea because i just made it all uneven again but it sanded off very easily. The primer, when fresh, it's a really good product. If all goes well, i should be able to start with the first half of the mold tomorrow.
Small update: I got two more layers of PCP on it (4 total), each subsequent one thinner than the previous. First used about 170g, second about 150, third 100 and fourth just about 60g. If i had the shape right the first time i could've used way less, but i kept sanding through it. I think a cheap spray paint would be really helpful for flattening key surfaces.
Either way, 4 layers and some extra filler is really as far as i want to take this. It's currently cured and waiting for last sand and polish, and I should be ready to prep it for taking the first half of the mold. I'll put it on a base plate, seal bottom with wax, and put a plastic fence across it that will form the side profile of the mold. Wanted to do that over the weekend, but life got in the way again...
Either way, 4 layers and some extra filler is really as far as i want to take this. It's currently cured and waiting for last sand and polish, and I should be ready to prep it for taking the first half of the mold. I'll put it on a base plate, seal bottom with wax, and put a plastic fence across it that will form the side profile of the mold. Wanted to do that over the weekend, but life got in the way again...
I sanded the pattern down, but didn't do a very good job at it. Still had a lot of scratches from lower grits, but I decided I've put way too much effort into it already.
When fitting everything, I realized the shape is so complex that it will require a 3-piece mold, as it won't release from just two halves. That doesn't mean much more material used, but it's yet another molding cycle to do. It's two layers of gelcoat (4-8h after each), then a coupling coat (4-8h) then the reinforcement, and that multiplies by the number of parts of the mold. So it's easy to see that even such a small thing can take days even when everything goes according to plan. At that point i don't have much choice so I'm just going with it, but will certainly take it into account in my next projects.
At least all the hours of youtube videos watched meant i felt right at home when doing the seal. I figured it would be even easier if I had a CNC mill, as i could just scan the part and generate a perfectly matching cross-section shape.
In the end, first layer of gelcoat went on, and the second will follow right after:
The oven is really helping here as at least I have a decent sealed place to put it in where I'm not afraid it wil get knocked over and don't have to worry about temperature swings (it still gets down to single digits in the night).
When fitting everything, I realized the shape is so complex that it will require a 3-piece mold, as it won't release from just two halves. That doesn't mean much more material used, but it's yet another molding cycle to do. It's two layers of gelcoat (4-8h after each), then a coupling coat (4-8h) then the reinforcement, and that multiplies by the number of parts of the mold. So it's easy to see that even such a small thing can take days even when everything goes according to plan. At that point i don't have much choice so I'm just going with it, but will certainly take it into account in my next projects.
At least all the hours of youtube videos watched meant i felt right at home when doing the seal. I figured it would be even easier if I had a CNC mill, as i could just scan the part and generate a perfectly matching cross-section shape.
In the end, first layer of gelcoat went on, and the second will follow right after:
The oven is really helping here as at least I have a decent sealed place to put it in where I'm not afraid it wil get knocked over and don't have to worry about temperature swings (it still gets down to single digits in the night).
Initially that was the idea that it will be open at the top (bottom as it sits in the last photo) and it will taper so that it could be one piece. But then I put it on the bike and thought I can have more useful shape if I make it narrower at the top (to fit the frame rails better, sorry I don't have a better photo here), so it couldn't just be pulled out of the mold upwards, so then it was gonna be 2.If what you want to make is the black part (before gelcoat), it looks to me like it could be a one part mold
Maybe I am missing something though.
And then I realized the front is actually wider than the rear so if I did just two I might not be able to slide the 2nd part off as it will be locked in two dimensions. It could maybe work but I think I'd rather play it safe here and do three parts. It's not really much harder or doesn't take that much effort, just takes a bit more waiting time, and if the alternative is having it stuck inside then I'd rather wait a bit more than do it all over again.
Either way, the first part received the coupling coat today and in the afternoon I can lay down the reinforcement. Really this part of the process is quite pleasant. No sanding, just pop into the workshop, mix some resin, put on, put into the oven and leave for work...
The first part of the mold went well. I've reinforced it with the main heavy CSM - it was quite hard to properly wet down, but i think thanks to the coupling coat it should be structurally sound. I've cleaned up and prepared the next "quarter" and it's ready to accept gelcoat.
This process takes an awful lot of time, admittedly, but a lot of it is because I'm just very inefficient. With the experience I've gained, i think i could repeat all the steps so far in 1/5 of the time (and in calendar time, that would be even quicker, eliminating useless wait times).
This process takes an awful lot of time, admittedly, but a lot of it is because I'm just very inefficient. With the experience I've gained, i think i could repeat all the steps so far in 1/5 of the time (and in calendar time, that would be even quicker, eliminating useless wait times).
I'm at the 3/3 stage. The first layer of gelcoat already went on the last part. It's probably already cured during the night but i was rushing to work in the morning so the second layer will likely be applied in the evening; from there I will need at least one more day for reinforcement layers, and the mould should be ready to use.
It's actually not a lot of work, but it takes a lot of time. I need to clean up the garage to allow for easier access next time because stuff like applying 6 layers of release agent 15 minutes apart is way easier when i can easily reach everything (or am working on multiple parts at the same time).
Sigh, I already had a reply but the forum decided to remove it
I'll post in a few posts to avoid this happening again. First, the mould:
I forgot the aligning pyramids between parts 2 and 3. The alignment was still good, but then I tried to fix a few chips, wrinkles and problematic spots with spot repairs. Even after sanding, I couldn't get it to mate perfectly. Note to self: don't try to fix the mating surfaces.
On the positive note, the mould didn't shrink or change shape at all; this is undoubtedly thanks to the special uni-mould tooling resin.
I'll post in a few posts to avoid this happening again. First, the mould:
I forgot the aligning pyramids between parts 2 and 3. The alignment was still good, but then I tried to fix a few chips, wrinkles and problematic spots with spot repairs. Even after sanding, I couldn't get it to mate perfectly. Note to self: don't try to fix the mating surfaces.
On the positive note, the mould didn't shrink or change shape at all; this is undoubtedly thanks to the special uni-mould tooling resin.
For the actual part, I decided that it's likely it won't come out great, so I'll see if the shape fits with a cheap prototype. I had a lot of 100g and 450g left from the uni-mould kit, so decided I'll do two layers of gelcoat, 1 layer of 100g and 2 layers of 450g.
I had some sealed gelcoat from last year that looked okay, and about 2kg of left over resin that already started to clump. I roughly sifted through it, added some acetone and decided it's better than throwing it out. The gelcoat went in no problem:
But the actual laminate was another story. So, the problems, in order:
* Getting 450g mat to fit those tight curves is really tricky. I previously only used 150g and that's way easier; I think 200-300 would be a happy medium.
* Because of that, I had spotty mat coverage in places and it didn't really extend past the edge when in place. It's hard to judge how much mat is needed, as when dry it will appear larger than when it wets out and actually covers the entire surface of the mould.
* I initially mixed about 110% of the cloth mix in resin and that turned out to be way too little for my poor technique. I think I used too much in the initial layers, trying to wet the mat from the bottom.
* I mixed up more but didn't have a container ready so it started to get a bit chaotic.
* I should've used just one layer of 100 and one layer of 450, but i was insistent having already cut two layers
* Even when adding more resin, i had trouble wetting the last layer out. Pressing, brush, using a roller, nothing helped. It also started to fall off at the top of the mould.
At that point i decided i need vacuum to have any chance of making the shape i wanted. I should've known that it will just want to delaminate at the top when it curves and cut the mat with enough slack to go over the bend and out to the top surface with resin there.
* I didn't have vacuum setup prepared so had to cut everything very quickly
* Because of that my peel ply coverage wasn't perfect and i got a part of the ply stuck _underneath_the last CSM layer (I have no idea how it happened).
* I used my quick bag which normally would work great for this scenario but it was too small to go all the way to the bottom of the mould
Because the mould is made in parts, that also meant it got punctured almost immediately by a bolt sticking out. I should've known that, but I only really needed it to hold for a while to press the resin to the top layer. Thankfully, that seemed to work. Even though the bag lost the seal almost immediately (after I patched the biggest leak), it seemed to consolidate the layers enough:
This was in the morning today. I only ripped out the vacuum layers, and as the resin was still quite sticky, decided to leave it for the day to cure a bit more before demoulding.
P.S. I forgot to mention the most annoying part; I tried fitting the pattern in the 2005 frame again and I have no idea what i had in mind but it decidedly looks like the large Votol EM200 with that huge radiator won't clear the shock absorber. For the smaller 260 i planned to put it entirely inside, and with the larger one to have a cutout so that the radiator sticks out, but i will have to revise those plans. I still have some wiggle room; I could use the 260 on the CRF#2 and get the 200 to my main bike for now (which i planned to use the 08 subframe anyway necessitating a new mount). I could cut the radiator a bit. There are options, it's just another dumb snag. I think the most annoying part is that 08 subframe, which yeah I technically like much more but it would be nice to just make more of those boxes for the assymetrical 05 frame and get more use of the mould. We'll see how it goes, next one will certainly go much quicker with all the experience I got from this.
And this post is dedicated to @jbjork who I just realized has involuntarily pulled me into this mess. The rabbit hole goes way deep, it seems.
I had some sealed gelcoat from last year that looked okay, and about 2kg of left over resin that already started to clump. I roughly sifted through it, added some acetone and decided it's better than throwing it out. The gelcoat went in no problem:
But the actual laminate was another story. So, the problems, in order:
* Getting 450g mat to fit those tight curves is really tricky. I previously only used 150g and that's way easier; I think 200-300 would be a happy medium.
* Because of that, I had spotty mat coverage in places and it didn't really extend past the edge when in place. It's hard to judge how much mat is needed, as when dry it will appear larger than when it wets out and actually covers the entire surface of the mould.
* I initially mixed about 110% of the cloth mix in resin and that turned out to be way too little for my poor technique. I think I used too much in the initial layers, trying to wet the mat from the bottom.
* I mixed up more but didn't have a container ready so it started to get a bit chaotic.
* I should've used just one layer of 100 and one layer of 450, but i was insistent having already cut two layers
* Even when adding more resin, i had trouble wetting the last layer out. Pressing, brush, using a roller, nothing helped. It also started to fall off at the top of the mould.
At that point i decided i need vacuum to have any chance of making the shape i wanted. I should've known that it will just want to delaminate at the top when it curves and cut the mat with enough slack to go over the bend and out to the top surface with resin there.
* I didn't have vacuum setup prepared so had to cut everything very quickly
* Because of that my peel ply coverage wasn't perfect and i got a part of the ply stuck _underneath_the last CSM layer (I have no idea how it happened).
* I used my quick bag which normally would work great for this scenario but it was too small to go all the way to the bottom of the mould
Because the mould is made in parts, that also meant it got punctured almost immediately by a bolt sticking out. I should've known that, but I only really needed it to hold for a while to press the resin to the top layer. Thankfully, that seemed to work. Even though the bag lost the seal almost immediately (after I patched the biggest leak), it seemed to consolidate the layers enough:
This was in the morning today. I only ripped out the vacuum layers, and as the resin was still quite sticky, decided to leave it for the day to cure a bit more before demoulding.
P.S. I forgot to mention the most annoying part; I tried fitting the pattern in the 2005 frame again and I have no idea what i had in mind but it decidedly looks like the large Votol EM200 with that huge radiator won't clear the shock absorber. For the smaller 260 i planned to put it entirely inside, and with the larger one to have a cutout so that the radiator sticks out, but i will have to revise those plans. I still have some wiggle room; I could use the 260 on the CRF#2 and get the 200 to my main bike for now (which i planned to use the 08 subframe anyway necessitating a new mount). I could cut the radiator a bit. There are options, it's just another dumb snag. I think the most annoying part is that 08 subframe, which yeah I technically like much more but it would be nice to just make more of those boxes for the assymetrical 05 frame and get more use of the mould. We'll see how it goes, next one will certainly go much quicker with all the experience I got from this.
And this post is dedicated to @jbjork who I just realized has involuntarily pulled me into this mess. The rabbit hole goes way deep, it seems.
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So you are using one layer of 100g/m2 and 2 layers of 450g/m2 mat? That must turn out rather thin and unstable?
I usually use 4 layers of 450g/m2.
Do you cut the mat and then try to fit it in to the shape as one big part?
I rip (not cut to keep the fibers intact) small pieces that I can fit easier. A complex shape like that would be at least 5 pieces I think.
What release agent are you using, and are you supposed to use several layers 15min apart?
I have used some in the past, but not very successfully. It sure could save time and money to not have to paint and wax everything..
I usually use 4 layers of 450g/m2.
Do you cut the mat and then try to fit it in to the shape as one big part?
I rip (not cut to keep the fibers intact) small pieces that I can fit easier. A complex shape like that would be at least 5 pieces I think.
What release agent are you using, and are you supposed to use several layers 15min apart?
I have used some in the past, but not very successfully. It sure could save time and money to not have to paint and wax everything..
It's quite substantial, actually, should be more than enough for housing a controller and cables. It weighs 816g. If I recall correctly, I had about 270g of mat and about 200g of gelcoat, meaning about 346g of resin with 43-57% mat-to-resin ratio; or about 0.27m2 (since 450+450+100 conveniently add up to 1kg/m2). With CF, I might be tempted to use just three layers of 200g twill, which would give us 600g/m2 of mat and 1200g/m2 total, adding up to 324g total weight, so a 50% reduction is totally within reach.
I typically cut to shape and then tear out the edges to make them blend better. 450g is thick enough that tearing it precisely is quite annoying. I try to use at least two different layouts so that the join lines will be covered. For this part, I had one layout with 3 pieces, and one with 5.
CR1 easy-lease chemical release agent.
CR1 Easy-Lease Chemical Release Agent - Easy Composites
Easy-to-use and highly effective semi-permenant chemical release agent for almost all mould release applications. UK next-day/fast EU shipping.
www.easycomposites.eu
Yes, you're supposed to apply 6 layers 15 minutes apart, with the last layer left for at least an hour. And it has operating temperature similar to resin, so 18-23C optimal. So far it's been working really well; it's easy to apply and leaves an excellent finish. I had no trouble separating the plug from the mould, or the mould from the final part. However, I've additionally used RW4 spray wax on the mould flanges to make sure any resing seeping in won't glue them. With gelcoat that wasn't really necessary as the flash lines didn't extend more than 4-5 mm into the mould.
Instead of paint, I encourage you to try PCP. Not the drug
but the Pattern Coat Primer. PCP Polyester Pattern-Coat Primer Resin - Easy CompositesI had lots of trouble earlier with epoxy primers, paint, fillers etc. This stuff is a complete game changer imo. It applies like a very flowy gelcoat (and can be sprayed), is really really hard when it sets, but at the same time sands super easily and doesn't clog the sandpaper. I only got mine to about 500 with sandpaper, but it's supposedly polishable well beyond 1200 for gloss finish. I also have some hi-gloss coat i might try next time, but i kinda wanted matte anyway, plus i polished the mould afterwards anyway.
And lastly, I recall that you had problems with mould shrinkage. I'm starting to sound like an Easy Composites shill but their tooling resin seems to really be super stable and exhibit 0 warpage or shrinking. I checked it just today and the price ends up maybe 2x what I pay for the cheapest polyester locally in Poland, so it feels like it's well worth the investment even if you don't buy into entire uni-mould kit.
P.S. I would've forgotten; here's the final part!
Attachments
Working on the battery: I've printed my current iteration of the enclosure - not fully, just a slice to see if it will fit in the frame, and whether the cells will fit in the enclosure. The printer seemed to clog on the last layers (it was a 23h print despite being really thin), but it is still usable.
The cells fit inside with plenty of room; the elastic tabs on the side will need to be folded, of course, but i think that i can protect them from chaffing adequately. I thought for a while about using the enclosure as a pressure element, but it would be hard to get it precise enough, plus i would then need to press on the BMS as well, so it seems that my original idea is still the best i had. I need to cut out the old engine mount from the frame to see if the box will indeed slide in fully - the frame might need a bit of modification, and i feel that cutting a couple mm from the reinforcements really won't hurt it, but obviously i'd rather make it all just fit. It's a delicate compromise between making it fit both in the frame (smaller = better) and the cells (bigger = better).
I also want to start working on the clamping bars soon - I need a simple centering jig to make drilling holes in them repeatable, and then I'll need 40 of them. The top carrier plate design is pretty much finished and ready to be sent out for manufacturing, but i want to order everything at once.
I've also managed to obtain another 2005 subframe, so if I end up making another composite box, i might actually just build the 2nd bike just like the first, with an enclosed electronics box. I might want to buy a 2005 seat as well and keep the 2008 seat and frame for future builds/upgrades; that's perhaps less of a problem for now, the battery remains the biggest risk item.
The cells fit inside with plenty of room; the elastic tabs on the side will need to be folded, of course, but i think that i can protect them from chaffing adequately. I thought for a while about using the enclosure as a pressure element, but it would be hard to get it precise enough, plus i would then need to press on the BMS as well, so it seems that my original idea is still the best i had. I need to cut out the old engine mount from the frame to see if the box will indeed slide in fully - the frame might need a bit of modification, and i feel that cutting a couple mm from the reinforcements really won't hurt it, but obviously i'd rather make it all just fit. It's a delicate compromise between making it fit both in the frame (smaller = better) and the cells (bigger = better).
I also want to start working on the clamping bars soon - I need a simple centering jig to make drilling holes in them repeatable, and then I'll need 40 of them. The top carrier plate design is pretty much finished and ready to be sent out for manufacturing, but i want to order everything at once.
I've also managed to obtain another 2005 subframe, so if I end up making another composite box, i might actually just build the 2nd bike just like the first, with an enclosed electronics box. I might want to buy a 2005 seat as well and keep the 2008 seat and frame for future builds/upgrades; that's perhaps less of a problem for now, the battery remains the biggest risk item.
I did some test fitments yesterday. I cut off the engine mount and very slightly altered the frame gussets. A lot of people trying to slide a rectangular battery into this frame seem to hit those exact two corners, but they really don't need much, maybe 5mm from a solid aluminium piece, to make everything fit quite well. This is an oversized enclosure with plenty of space inside and 3mm wall thickness; the final form will be slightly smaller, especially on the corners, and with fiberglass construction it shouldn't be much thicker than 2mm all around, so hopefully it will just slide in easily.
I still haven't decided on how to make the enclosure, but I'm leaning towards a simple CSM layup on a positive 3D-printed plug. The main advantages of that process are
* i work outside of the shape not inside of it, and that's quite a deep enclosure
* the plug will take minimal prep if 3D printed
* the inside will be more dimensionally accurate than the outside (meaning the cells will surely fit, and at worst it won't fit the frame - but it's much easier to alter it from outside than inside).
I think with my improved skills i can make it look reasonably smooth without hours of sanding afterwards.
I will also need to think about closing it; the slide-on cap i made for the first battery is kinda ok, but I am leaning towards a flange with screws all around with a gasket in between. In fact, i could even make it just like i make my split moulds - make the bottom half with a fence, rip the fence off, apply release agent and form the cap on the plug itself. Then I could use the alignment pyramids and have perfect alignment of the halves - yet another reason to use the positive method.
I'm going to start inserting thumbnails from now on because full size pics take ages to load...
So with the enclosure mostly sorted, i think i'll focus my attention back to the isolation and compression plates now, because they will likely take 1-2 weeks to get here after being ordered, and it'd be best to minimize waiting time. There's still a couple of small fixes i need to do - alter the shape slightly, redo the bottom splitter, figure out exact height (i can unroll the electrodes more or less or cut them to length - shorter battery is better, but might be tricky to assemble) and I've been thinking about an additional feature - terminal covers. I want to prototype a simple snap-on "box" that would go over every pair of electrodes which would make things much safer especially during initial assembly, but also later during handling. To mount them, I'm considering either clamp bolts (I'd make them go from the bottom, extend to the top, and just slide the box over the exposed threads) or two small slits where two latches would go, to the side - leaning towards the latter option right now. The balance wires would simply go through a hole in such isolation box.
I still haven't decided on how to make the enclosure, but I'm leaning towards a simple CSM layup on a positive 3D-printed plug. The main advantages of that process are
* i work outside of the shape not inside of it, and that's quite a deep enclosure
* the plug will take minimal prep if 3D printed
* the inside will be more dimensionally accurate than the outside (meaning the cells will surely fit, and at worst it won't fit the frame - but it's much easier to alter it from outside than inside).
I think with my improved skills i can make it look reasonably smooth without hours of sanding afterwards.
I will also need to think about closing it; the slide-on cap i made for the first battery is kinda ok, but I am leaning towards a flange with screws all around with a gasket in between. In fact, i could even make it just like i make my split moulds - make the bottom half with a fence, rip the fence off, apply release agent and form the cap on the plug itself. Then I could use the alignment pyramids and have perfect alignment of the halves - yet another reason to use the positive method.
I'm going to start inserting thumbnails from now on because full size pics take ages to load...
So with the enclosure mostly sorted, i think i'll focus my attention back to the isolation and compression plates now, because they will likely take 1-2 weeks to get here after being ordered, and it'd be best to minimize waiting time. There's still a couple of small fixes i need to do - alter the shape slightly, redo the bottom splitter, figure out exact height (i can unroll the electrodes more or less or cut them to length - shorter battery is better, but might be tricky to assemble) and I've been thinking about an additional feature - terminal covers. I want to prototype a simple snap-on "box" that would go over every pair of electrodes which would make things much safer especially during initial assembly, but also later during handling. To mount them, I'm considering either clamp bolts (I'd make them go from the bottom, extend to the top, and just slide the box over the exposed threads) or two small slits where two latches would go, to the side - leaning towards the latter option right now. The balance wires would simply go through a hole in such isolation box.
Since my previous attempt at a new box failed, i decided to enlist some help. Same mould, third try, professional setup:
And the result...
Not 100% perfect, i had some areas of bridging, but overall it's definitely the best composite part i've done so far. 346g all said and done. Going back to battery over the weekend...
And the result...
Not 100% perfect, i had some areas of bridging, but overall it's definitely the best composite part i've done so far. 346g all said and done. Going back to battery over the weekend...
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