whoa. i never broke 60wh/mi
i’m surprised at that difference.
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Super happy to see you finish this project. The end results were worth it. Watch out for Tucker 2024
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All of it
I don’t have an exact count, but adding up just the hardware alone reaches 6k. Probably close to 7k after including all the little bits, connectors, tools, etc that add up quickly (as I’m sure everyone here is familiar)
Timewise, easily 150+ hours, counting design and build.
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you’re not supposed to say this out loud.
my brother-in-laws father raced SCCA. He told me, i had to stop keeping track or i would have to stop doing it. 
Balance Lead Upgrade
Before the race this weekend, I wanted to streamline my charging setup. I manufactured and installed two wire harnesses that connect to the balance leads, and expose them on an accessible DSUB15 connector.
Dustcap on, dustcap off.
I then made some additional harnesses that connect to these two DSUB15 connectors.
One connects the two DSUB15’s in parallel and has a JST-XH connector that connects to my iCharger x12. This, along with an XT60 added to the terminal blocks of the G300’s, allows me to balance charge all 6 lipo’s inside the board at 1000W, WITHOUT needing me to take off the bellypan.
The other one can connect to the port and quickly see the status of all of the cells. While this can be done with the above harness and iCharger x12, it would require external power to turn on. While not super accurate, This gizmo makes checking the state of cells as simple as plugging it in. Probably won’t use it much in the long term, but it’s useful when testing.
“Brief” AVS Riderfest Recap
For those uninitiated, AVS stands for Apple Valley Speedway, and is north of LA. Big track made for drifting cars. Lap times for esk8 usually range from 1min20s~1min40s. I was able to post a 1min30s during qualifying on Ankle Wreacher.(I believe the esk8 lap record was set by @MarioChacon today, at 1min11s. I could be incorrect about this)
There was a race event held here on Today(Sunday). Qualifying times determine heat race positions, which then determine access to the Final race. The races are 3 laps(lasting about 5 minutes)
Overall, I couldn’t have asked for a better first race with the board, and I can’t wait to get the kinks ironed out. Thanks to the whole SDESK8 ARD Team for being such incredible, supportive, talented teammates (and congrats to @HAIRYMANJACK on 2nd place!) Wish I had more pictures to share.
Unfortunately. I had considerable problems with Ankle Wreacher throughout the day.
The main issue is that it would overheat incredibly quickly, which significantly affected my race results. Halfway though the 3rd (and last) lap every race, I would loose significant power as the motors thermally throttled. I lost 3~4 positions in the final race because of this (such is the nature of racing 
).
Once I came to a stop at the end of the third lap, the board would barely be able to move under it’s own power until it took a few minutes to cool down. Thank goodness it only needed to last 3 laps.
While it was 90°F outside, and nearly every esk8 board was having cooling issues, none had them to the same degree as mine (pun intended).
Most notable was @HAIRYMANJACK’s board(160A motor amps each motor, Reacher 7490 165kv), had a similar setup, but did not have the same overheating issues. Notable difference is rider weight (I’m ~50% heavier) and 165kv vs 265kv.
The fact I overheat but he doesn’t bucks my intuition. I would think that having 4x motors would lead to distributed power, meaning each motor would only get ~half the heat then a 2x motor board setup, right?
Relevant Hardware grey box
12s2p 9500mAh 150c LiPo
Reacher 7490 265kv motors
22T / 78T = 3.55 ratio
Relevant vesc settings grey box
Motor Temp Cutoff Start 85C
Motor Temp Cutoff End 100C
I adjusted the beta value of the thermistor to match a Reacher motor(same value as used by @HAIRYMANJACK)
Motor current started at 100A/motor, but I lowered it to 85A/motor after qualifying in an attempt to reduce overheating (to little avail)
I should be able to push significantly more then 85 Motor amps through these motors without issue…They’re rated for 10kW; 145A continuous, 200A max.
My hypothesis is that the 22T doesn’t give nearly a high enough ratio for the 265kv motors, especially for the racing at AVS where I spent the turn-y bits of the track at 20~25mph.
If I change out the 22T pinions for 18T, it would increase the ratio 3.55 → 4.33, which would let the motors run at a higher, more efficient RPM. This might also help with the Wh/mi efficiency problem.
I’d love to hear alternate opinions about what’s going on here, and if you’ve got it, best way to fix it.
Here's a bonus screenshot of me breaking the silly 100Wh/mi barrier, taken after coming off the track for qualifying(and after my motors cooled a bit).
esk8 news calc for either pinion size, for your convenience.
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Congrats on the race results on a new setup. Shame about the thermal throttling.
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I’d up the motor temp start and end cutoffs. Those reachers are pretty durable (well the Radium 6385s are at least). I have mine at 100 start, 115 end
sweet! always wanted to build a in board charging harness and expose the balance leads for easier checking. i didn’t want to perma join the balance leads. dual db15 is a great idea for that. 
W00t. congrats on huslting around that big ol track.
probably 'cause he had one motor. 4 is handicap apparently. 
/s
maybe you’re running into the iron losses thing @Skyart and @Tony_Stark were informing me of over on my v5#1 thread.
rpm based eddie currents from high rpms? though at 12s i’m not sure that’d be it. but if it gets worse with lower gear ratio… maybe? (seems unlikely)
did you record graphs of temps? are they stable or jumping around? maybe just move motor temp cutoffs the f out th eway and risk the life of the motors. definitely do that if they are noisy. (tho noisy temp sensors would feel jittery when the power cutts rather than smooth )
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and you are using the watts… so… bringing the heat?
it’s curious to me why you’re using so much. with 4x motors I’d expect some ineffeciency… but for it to tend closer to watts = mass * acceleration * distance. so it’s weird.
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This meshes with what I felt on track very closely, especially after coming off the track.
Very interesting.
Aye, I’d agree…
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With 4wd compared to 2wd total copper heat loss is halved, but copper heat loss per motor is actually 1/4, because P = I^2 * R
Really surprised you heat the motors so much…
Is your acceleration something stupid like 1G+?
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We don’t have a dyno chart for your motors, but it makes me wonder if you’re too far down and to the right on the efficiency map, where the efficiency drops like a rock.
At your top speed of 60MPH you need about 300N of thrust, depending on how much air resistance you’ve got. With your current setup that translates to 1.6N-m torque per motor, round it up to 2N-m for rolling resistance and iron losses.
The 6355 is half the weight of your motor, so that should be analagous to 1N-m on this chart, which would put you about here:
So it might be fine, but it’s close to the edge of the efficiency band. Given the uncertainty here you might be over the cliff, trying to push power through unloaded motors. I’d imagine that just going from 90% to 80% efficiency could get your gourd properly borked.
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welp. elsewhere in chat @tuckjohn mentioned getting temps up slowly to 95c … so. that’s pushing em pretty far. since/if? they aren’t short spikes moving the temp cutoffs out the way is probably not too helpful.
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Okay, so looking at this again after a couple nights of restful sleep.
@s_m_l_s_ is really putting in the work to make my board look good! Thanks man. Your photos are one of my favorite parts of race events.
No data recording on the board at the moment. I’m waiting on the Voyage systems Megan for logging on my board (Autumn 2023? I know It’ll drop when it’ll drop, I’m just too excited 
@janpom)
Unfortunately not. I mean, it’s quick off the line compared to a normie board when the motors aren’t overheating, but not 400 motor amps quick.
Very interesting information, and a promising theory. I can follow the argument that going from 90% to 80% efficiency could be the difference between fine and overheating.
However, efficiency != heat generated, right? Unless I misunderstand the graph, In the condition that the motor is along the bottom of the graph, the current going through it is small, so low efficiency*small number = small amount of heat. Whenever the motor starts to get/output appreciable power, the torque will increase, leading to an increased efficiency.
Would this make “living on the bottom edge” of the efficiency band fine? I also took a look at your “Total losses” graph in your Dyno thread, which seems to say the same thing.
This is really seeming like it could part of the issue, and hope it’s not. I think the best solution would be to get smaller KV motors to reduce the iron losses. That would be an unfortunate purchase I’d need to make. 
Considering the relative cost of pinions and new motors, I’ve bought smaller pinions that should arrive next week. I’m really hoping that the issue is just that the motors are over-geared, and just putting smaller pinions on the motors will solve the issue. Both of your proposed hypothesizes @fessyfoo and @Flyboy suggest that reducing the pinion size is going to make the overheating worse, so I’m excited to put them on and see what happens. For SCIENCE! It’s going to be fun if I’m proven wrong.
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