This looks amazing dude
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TPU suffers creep and plastic deformation. Not suitable for spring material. Would end up permanently deforming.
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Update time! Montrevel race.
I finished second, I could barely survive the heat in the leathers (37c/100f). Furthermore, our hotel didn’t have air conditioning either.
I had good pace in splits, but didn’t have the consistency to pull it all together. Optimal laptime a hair faster than David’s, but David’s best lap was faster than mine, and he was more consistent throughout the heats as well.
Was also racing urethane category on my cavity, which is waiting for some upgrades as well, hence the 2 medals. There’s some pretty cool pictures this time
Turns out my top speed is actually ~78, not 70 like I originally thought. I think the battery temperatures helped the power output quite a bit with these lipos - and the straight here is also more open and marginally longer than our usual tracks.
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CNC/ board update time!
Lets mill the part that holds everything together, the “rails” I’m calling it from now. Slight issue: part is 875mm long, cnc useful travel ~300mm. Having planned this heresy from the beginning, I built the enclosure with a door on the rear that flips up, and allows me to access the back and allows long material to stick out:
Made a flip-up cover from some painters tape, so that the chips are at least somewhat contained:
Ironically this ended up sealing better than the unfinished flip-up door.
First setup:
After 4th setup:
At this point chips were flying everywhere because the front “doors” had to be open due to the material sticking out towards the front by the end. The missing parts in the middle aren’t milled away, it’s just contoured out so I’m left with those sheets for future projects.
Here’s the milled out rail:
And a test fit of parts in the internal space:
10 lipos + BMS + ESCs easily.
20S6P with BMS + 4x G300 would be the max that fits internally.
Building that 20S6P soon.
Also cut out the acryllic part for the middle on a co2 laser. The graphics is not final, but I did want to put something on there. Will make a new one when I have new graphics… The “Billet Raceworks” text is probably gonna be either above the number, or right below the number and above the other logos. But that’s for the future.
Next up was mounting the vice on the table:
Programming this part in CAM was really difficult for me, but in the end I managed. First setup about to finish here.
Second setup, and the start of my day today. Thankfully I didn’t break my favourite endmill in this move, that only came later 
No idea why the stock pulled out. I tightened the vice quite hard. Been tightening it even harder since, and the stock seems to stay in since.
Setting up for setup 3. I thought the best way to approach this part is to start with the sides, then do bottom then top, but no idea if that’s the ideal way or not. The learning curve is quite steep…
Something probably wasn’t square. Had some unavoidable jaw lift in the vice. I’m suspecting Z tram since I didn’t measure that at all, but I’ll buy the spindle mount thing for the dial indicator and check. I’m also not the biggest fan of this vice, but it was only 140€ and not 1000€+ like a Kurt or similar quality offerings so…
I was experimenting with full DOC with the 10mm endmill and that was going quite well.
Until a minute later when the cutter decided to touch one of the parallels and yeet it out into the side of the enclosure, and break it’s own edges in the process. Sigh that was one of my favourite cutters and the most expensive one as well.
This is setup 3 (bottom) done:
And at this point all the CNC operations are done:
I still need to drill the kingpin hole, which will be done in the drill press in the vice on an angle block. The center of the hole is marked by the CNC. Also drill out the shoulder screw thread to 8.5mm (M10 predrill), as the spindle can’t handle drills that diameter. There’s a 6mm hole I just need to widen on the drill press. Then tap all holes in the tapping arm.
It’s crazy how less compact the chips are. Believe it or not, all the chips in the box here came out from this part only…
However, as cool as this progress was, there’s some bad news as well. I’m leaving today for summer holiday, to the Italian race then to Hungary, then to Brno race and coming back to Denmark from there. So because I missed my deadline yet again, here’s another month of delay now.
What’s left is the pair of this part, which will probably take me half a day of concentrated work, then milling out the arms. Probably in total it’s going to take 3 full days of work until every CNC part is done. Mid august most likely…
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I can’t wait to know the final weight of this board
Crazy impressive work!
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Probably the most impressive stuff I’ve seen on the forum.. You are a racer and amazing engineer, that’s a great combo. I am curious, design wise, if the battery in the chassis will be better for your racing results than the battery box on top. This time you will be a little higher off the ground - so I believe if your results with this board will be even better then you will probably set the standard for racing formfactors! Appreciate your work and congrats !!
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Next level stuff. Exciting to follow
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God damn dude this is incredible. You put like every daydream esk8 idea I ever had all into one build 
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I don’t care if it’s not done by the end of the year, this is getting my BOTY vote regardless. So satisfying watching the milling videos. More of those please.
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I think you may be confused about what is good and what is bad…
All I see is good news…
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Thanks for the positive comments everyone!
@glyphiks Chassis itself (alu parts and swingarms) was somewhere in the range of 9-11kg last time I checked, which was a while ago and I did a couple updates since. Add wheels, 4wd drivetrain with big motors and enclosed gears, big battery, big escs, and it’s gonna be quite heavy! Still significantly lighter than an etoxx psychoframe though
I think weight is not necessarily a bad thing if the chassis and trucks are tuned for it and there’s power to spare. It’ll certainly help with getting the tires up to temperature. I’ll try to hit a happy medium - no compromises in terms of any of the parts or their strength/reliability, while still trying to at least somewhat keep the weight reasonable. Will be interesting putting it into the car though.
@57efy the ride height should actually be relatively similar to what I have now, only raised by a couple millimeters. Moving weight lower is always a good thing in my opinion, regarding moving the battery into the belly of the board.
Regarding setting the standard… That’s exactly the plan 
This is just the beginning, so much more custom things to come! Including electronics. If everything works out, this is going to be the most advanced board to date both in terms of applied mechanical and electrical engineering.
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I was chatting with one of the kart guys the other day about tyres and his recommendation for racing (although illegal in karting events) is to heat the tyres with a blow torch before racing.
I’ve not personally tried it but I think it might be a solution to my issue of not enough LiPo battery for warm ups then racing. You’ll certainly not have that issue with the battery you’re planning though!
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It might work, but it’s a thermal shock for the tire. If you heat it up too quickly, you reduce the lifespan.
Reducing the number of heat cycles extends the lifespan. Best solution would be to use tire warmers and have the tire hot to the core.
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Yeah for sure. I’m talking, finals or something 
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3D printed interlocking cell holders for the 20S6P battery build for the Reliance RS50 cells. Printing them from ASA for heat resistance.
Void in the middle fits a 22S JBD smart BMS - I already have a 50A one on hand, I really hope that’ll be fine thermally so that I can max out my 45A charger.
The rest of the battery I won’t model yet - I’d prefer to figure that out hands on.
As far as ESCs, I’m gonna be using a D100s + 2G300 in the beginning, itching to swap that D100s out sometime in the future. Haven’t fully decided if 2x G300 or an R200S will be the replacement for it yet. Leaning towards the R200S, but I’d prefer seeing some real world testing first from someone else.
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ASA cell holders are printed out, just need to populate them with the RS50 cells.
Also tapped all the holes in the rails.
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Got some catchup to do with posting…
Italy race updates. Was my easiest win by a long shot. The real competition didn’t show up 
The track was quite abrasive and worked perfect with my kart tires. Peaked 2G for the first time.
From the end of heat 2 I was “struggling” with some electronics issues, thought its receiver wiring related, tried solving it on the spot but couldn’t so I just ended up continuing with the unpredictable throttle. The throttle felt “sticky”, it didn’t back off the neutral or apply brakes properly. The brakes did come on eventually after a random amount of time… Even had a pretty scary overshot corner. (coming from the right side of the picture)
Couple days after the race I installed a brand new GT2E with a new receiver to see if it fixed it, and it didn’t… So I had the idea it might be the canbus cable. It was. After a new canbus cable the throttle felt good again.
When my throttle was working I was ~5 seconds per 3 lap heat faster than the fastest EUC (who is also seasonal 1st place). With the faulty throttle I changed my approach from my “point and shoot” style to a smooth style, with barely using the throttle and essentially not using the brakes, and that still ended up with ~1 sec per heat faster than the fastest EUC, I could carry so much more corner speed in comparison.
Hence the 66% power (consistency) rating given by the xerace timing system. That gap with 66% power is nuts
Also for reference, my lap times on the skate were 2 seconds faster than my lap times in the rental karts. Here’s my best lap on the skate. Another track record in the bag 
And I’m sure faster times would still be possible, I actually worked so much on the new board that I barely even had time to practice this year.
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Next up was Brno - that race didn’t quite go as planned.
I’m all good, the gear did it’s job. Not even a headache after breaking the Nexx X.WST3 helmet so spectacularly - that’s why I swear by running high quality fiber construction ECE22.06 rated helmets, especially for racing. And on the moto racing leathers I can’t even see signs of any damage, which is again great news, given that I went down at 64 km/h.
Fell right out of the bindings and heelstraps somehow. Board flipped on it’s top, fell on the racebox, then slid a fair bit but the racebox still works thankfully.
The cause of the fall was quite easy to determine - I felt a wheel lock up for a brief moment, under acceleration, just before I’d have switched to braking. One of the motors came loose - some motor mounting screws were lost, and the 2 remaining ones had sheared the thread off from inside the motor. I was using the full engagement of the stator base btw…
The loose motor shifted too close to the wheel spur and the gears locked up. The pinion suffered some damage but still usable, the straight cut wheel spur had a couple teeth converted into helical… It still runs with loosened backlash so I’ll run it until I’m ready to put on the double stage drives. ~1.5-2 months out from today I’d guess. By pitland I should be on the new drivetrain. 
Even though I crashed in the first heat (out of 6), I still managed to secure the esk8 track record, so that’s something at least:
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After Brno race, I got back to Denmark and continued working on the chassis.
First I milled the second swingarm base, with a CAM redone from scratch.
Setup 1 from the bottom:
Setup 2 from the top:
Left side
Right side
My previous issues with the vice I could mostly overcome by a better ordering of the setups and being much more vigilent about mounting the stock. That includes a rubber hammer and a ton of patience. Along with multiple spring passes for the contours so that the walls are actually parallel. It’s still not perfect, but it’s serviceable with extra care. So at least I don’t immediately have to drop 1k$ on a vice
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Next up was making the arms for the swingarms.
Here’s the CAM:
And then milling the top:
And the bottom:
Forgot to make pictures of the sides in the mill but I altered the design to this
I included 2 holes for cable management which were meant to be M4 thread, but I made the mistake to tap by hand… Should’ve set it up in the vice and use the tapping arm. Broke a tap in one of the holes so I’m not gonna have these to attach my cables to… Considering giving it a go in the next one with M5 instead and using the tapping arm. So glad I bought that, every time I tap by hand I realize how much I hate tapping by hand it always goes so much smoother and easier with the tapping arm!
I milled this twice and that concluded the CNC part of the build! I was so stoked to be done with it.
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