From all my readings all that stuck was focbox and focbox unity are hw4 based. so two current shunts. but with something better than usual on the fets that makes them handle more current. and of course with unity only using one cpu it’s even more unique.
I believe focbox unity handles high current pretty well. despite not being hw6. which was the thing i thought was better about hw6 stuff. but I also think i’ve learned the three shunts in hw6 makes it track phases better and perform better in general and better without sensors.
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Maybe because the rotor is heavy or bearings filled w grease. Maybe run them a while then try to find the kv
Right so there is something like that going on. One motor seems to have a lot more resistance than the other. I’m not sure how I should think about this.
using vesc-tool to control, a constant 3 amps spins one motor up to 95% duty cycle right away. the other would get seemingly stuck at 26% duty cycle. but letting it run for a few minutes it slowly crept up eventually seeming to break loose and jump to 95% duty cycle.
suspect motor after a minute or two of 3amp
good motor up to speed/full duty cycle at 3amps in under 3s
rerun suspect motor after that minute or two “warmed up” also up to speed in under 3s.
let suspect motor cool down for 30s or so, then it takes 6 seconds to spin up.
what do you make of this @hummieee ?
How do they spin unpowered in ur hand? I’m assuming the one w resistance is noticeable resistance in ur hand too. Be good to get the kv of each but assuming it’s not an electrical issue, which it probably isn’t, it’s gotta be compressed bearings, or some heavier grease in that one(I mixed and tried different bearings and the high heat resistant have thick grease), or possibly damaged bearing (how do they sound), or slight rubbing inside. With all these possibilities it’d be best if u ran them for at least 10 miles to eliminate any rubbing inside and we could go from there. Worst case send them brack and I’ll replace the bearings.
I can feel slightly more resistance in the one motor.
Do ten miles and if it’s still there I’ll take them n replace the bearings. But then again it could be the thicker grease and that will take more time. Do 20!
How do they sound? Could be noise from the bearing or rubbing of excess glue and that will wear down in a bit
Whatever it is do at least 20 miles and then let’s see what happens.
ok. right now it’s just on the bench running off another boards battery. was trying to figure out the KVs before deciding on my pack.
getting you a video of both now.
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Hard to tell from the sound but if one is turning slowly in ur hand it’s either thick grease, compressed bearing, or glue rubbing. Can u ride them at least 20 miles and then feel again and we can decide then. Hopefully u live in USA and it’s just 18$ shipping box to me you’d have to pay. These are unused right?
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Yeah. I can ride em. but I’m moving slowly on this build. so it’ll be a bit.
yes i’m in CA. yes they are unused.
Thanks for your input.
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I had zero luck with the kv command in todays attempts. this time I never got anything execpt 0kv out of it. asked on vesc forum. we’ll see.
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Can u figure manually at top speed?
: erpm converter to rpm( divide by 7 for the 14 magnets), times .95 since that’s the max duty cycle, divide by the voltage
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Ignoring the KV command, I continued down the calc it myself path. currently not sure my formula is correct.
my procedure ended up being like this. Use vesc-tool to run the motor at a fixed amps ( 3 amps in my case. ) let the motor spin up to 95% duty cycle. (doing lower duty cycles gives wildly varying results. )
then I sampled the realtime data 10 times by doing a screen grab of that section of the screen.
and in put it into a spreadsheet
left motor:
| power |
Duty Cycle |
erpm |
battery current |
motor current |
volts-in |
pole pairs |
v=W/A |
rpm |
kv m1 |
kv m2 |
kv m3 |
|
|
|
|
|
|
|
|
|
|
|
|
| 83.8 |
94.60% |
19109 |
2.08 |
2.57 |
40.8 |
7 |
32.61 |
2,730 |
88.5 |
83.7 |
70.7 |
|
|
|
|
|
|
|
|
|
|
|
|
| 73.3 |
94.90% |
19159 |
1.82 |
2.26 |
40.8 |
7 |
32.43 |
2,737 |
88.9 |
84.4 |
70.7 |
|
|
|
|
|
|
|
|
|
|
|
|
| 67.9 |
94.90% |
19203 |
1.68 |
2.07 |
40.8 |
7 |
32.80 |
2,743 |
88.1 |
83.6 |
70.9 |
|
|
|
|
|
|
|
|
|
|
|
|
| 63.6 |
94.90% |
19231 |
1.57 |
1.94 |
40.8 |
7 |
32.78 |
2,747 |
88.3 |
83.8 |
71.0 |
|
|
|
|
|
|
|
|
|
|
|
|
| 60.9 |
94.90% |
19255 |
1.51 |
1.87 |
40.8 |
7 |
32.57 |
2,751 |
89.0 |
84.5 |
71.0 |
|
|
|
|
|
|
|
|
|
|
|
|
| 59.1 |
94.90% |
19299 |
1.46 |
1.8 |
40.8 |
7 |
32.83 |
2,757 |
88.5 |
84.0 |
71.2 |
|
|
|
|
|
|
|
|
|
|
|
|
| 58 |
94.90% |
19311 |
1.44 |
1.77 |
40.8 |
7 |
32.77 |
2,759 |
88.7 |
84.2 |
71.2 |
|
|
|
|
|
|
|
|
|
|
|
|
| 55.8 |
94.90% |
19345 |
1.38 |
1.7 |
40.8 |
7 |
32.82 |
2,764 |
88.7 |
84.2 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
| 52.98 |
94.90% |
19361 |
1.31 |
1.61 |
40.8 |
7 |
32.91 |
2,766 |
88.6 |
84.1 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
| 54.8 |
95.00% |
19375 |
1.36 |
1.69 |
40.8 |
7 |
32.43 |
2,768 |
89.9 |
85.4 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
right motor:
| power |
Duty Cycle |
erpm |
battery current |
motor current |
volts-in |
pole pairs |
v=W/A |
rpm |
kv m1 |
kv m2 |
kv m3 |
|
|
|
|
|
|
|
|
|
|
|
|
| 60.3 |
94.90% |
19230 |
1.49 |
1.83 |
40.8 |
7 |
32.95 |
2,747 |
87.9 |
83.4 |
71.0 |
|
|
|
|
|
|
|
|
|
|
|
|
| 52.4 |
94.90% |
19261 |
1.29 |
1.64 |
40.8 |
7 |
31.95 |
2,752 |
90.7 |
86.1 |
71.1 |
|
|
|
|
|
|
|
|
|
|
|
|
| 48.6 |
95.00% |
19280 |
1.2 |
1.47 |
40.8 |
7 |
33.06 |
2,754 |
87.7 |
83.3 |
71.1 |
|
|
|
|
|
|
|
|
|
|
|
|
| 47.8 |
94.70% |
19309 |
1.16 |
1.4 |
40.8 |
7 |
34.14 |
2,758 |
85.3 |
80.8 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
| 44 |
95.00% |
19330 |
1.08 |
1.34 |
40.8 |
7 |
32.84 |
2,761 |
88.5 |
84.1 |
71.2 |
|
|
|
|
|
|
|
|
|
|
|
|
| 41 |
94.90% |
19352 |
1.01 |
1.26 |
40.8 |
7 |
32.54 |
2,765 |
89.5 |
85.0 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
| 35.8 |
95.00% |
19367 |
0.88 |
1.11 |
40.8 |
7 |
32.25 |
2,767 |
90.3 |
85.8 |
71.4 |
|
|
|
|
|
|
|
|
|
|
|
|
| 41.3 |
94.90% |
19381 |
1.02 |
1.25 |
40.8 |
7 |
33.04 |
2,769 |
88.3 |
83.8 |
71.5 |
|
|
|
|
|
|
|
|
|
|
|
|
| 38.2 |
94.90% |
19393 |
0.94 |
1.16 |
40.8 |
7 |
32.93 |
2,770 |
88.6 |
84.1 |
71.6 |
|
|
|
|
|
|
|
|
|
|
|
|
| 39 |
94.90% |
19401 |
0.96 |
1.18 |
40.8 |
7 |
33.05 |
2,772 |
88.4 |
83.9 |
71.6 |
|
|
|
|
|
|
|
|
|
|
|
|
| 38 |
94.90% |
19419 |
0.94 |
1.16 |
40.8 |
7 |
32.76 |
2,774 |
89.2 |
84.7 |
71.6 |
|
|
|
|
|
|
|
|
|
|
|
|
I’ve listed two methods of kv calc. m1 is the process I followed above.
M2 is just RPM/Volts
I think M2 makes more sense because If Power is actually power in the motor then the duty cycle would already be accounted for. so don’t need to factor it again
Also m2 suggests these are probably nominally 85kv motors. ( I don’t think @hummieee did higher thatn that? ) m1 would suggest 89kv
edit: added m3 method. just take the input RPM/Effective Volts
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yeah. I was working on that post as you worte. though what you post is kinda an m3 method. I didn’t capture the input voltage in my previous samples so I’d need to do another round.
true and there’s only a tiny bit of voltage drop.
I think u should ride them a while and the high current draw w no load makes me think they’re high heat bearings w thick grease.
I get 68kv I think. But doesn’t reveal the cause of the drag. Good to know though. That’s what I wound almost all to be. 30mph on 12s. 84mm diameter wheel
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Yeah I added an m3 method to the charts above I get about 71kv. which is wildly different than the other methods. 
so hmm.
but the real deal here is I wanted to know my top speeds at 12s and 10s.
and at 10s my no load rpm is pretty consistently about 2750 for a top speed of 43.5kph / 27.2mph ( which was the @sesat method ) so 82% loaded that’s 35kph/22mph so… I likely do want to chose 12s.
I do wish I understood what what was wrong with the above methods for kv determination. at most one of them can be right.
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you will hit better than 82% of no-load when loaded. 10s bet u hit at least 25.
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