Fess' 1st build thread. Tayto on hummie hubs

#50

left:

right:

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#51

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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#52

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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#53

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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Motor KV measure - HELP needed
#54

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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#55

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.

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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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Motor KV measure - HELP needed
#56

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.

#57

Volts in” is there 40.8

#58

true and there’s only a tiny bit of voltage drop.

#59

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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#60

Yeah I added an m3 method to the charts above I get about 71kv. which is wildly different than the other methods. :smiley: 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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#61

you will hit better than 82% of no-load when loaded. 10s bet u hit at least 25.

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#62

Thinking about wether I should cut through the enclosure to expose the heatsink on this dual escape. like this example here:

I’m torn between clean case, and no esc exposure to the ground, and the fact that this heatsink seems designed to be exposed. i’m hoping i won’t be too worried about thermals on a last mile board. but I could be wrong.

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#63

My biggest blocker now is deciding things… sigh

20700s 12s3p fit pretty close width wise. and sanyo 20700b is what I think I want in my second build, so this allows me to buy all the same batteries.

70mm long cells however are kinda tight length wise.

The Escapes with the heat sink are kinda bulkier than just old school focboxes. I guess it’s the heat sink.

the curve in the enclosure near the rear exit limits some of the length.

practicing tight fit stuff is part of what I need to do for the second build tho. so much :thinking:

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#64

Mock up of stagger stack idea. Holders need some improvements likely.
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Archived: the OG noob question thread! :grinning:
#65

Does staggering actually help?

#66

In a lot of cases no. In my target for my second build it will help fit trading width for height for 12s6p 20700s. In this build it would help fit 12s3p 21700.

Still Deciding which batteries for both builds at the same time and then deciding wether to practice a stagger stack on this build.

#67

Posted this to a friend. but days later the same thoughts running through my head.

god damnit. my head is all over the place on batteries.
my two projects are my tayto and my prototipo.
do same batteries for both to get one order of one type?
fit 50% more range and power into prototipo than 756wh 70amp 10s pack. at least 20% more range.
sanyho 20700b 12s6p in the prototipo would do that but requires staggered stack to fit width wise. and probably a riser for a few mm extra height. that’d be interesting and hard and novel.
if I go for that do i do a similar thing on the tayto just to practice…
in the tayto 2{0,1}700s are tight length wise if i do 12s3p. could do 12s2p but then I’m not practicing or doing anything the same as second board. starting to think i shouldn’t…

then alternatively just… get the P42As… do 12s5p in the prototipo… all the amps. 20% more range. ( than 10s5p 20700b stock )

and 12s2p in the tayto. 90 amps??? p42as are crazy…

those last options keep it simpler space wise and the only goal I compromise on is hitting 50% more range on the prototipo. trading it for 20%.

idk what help i need… probably just moral support… and decisiveness. :smiley:

instead I just go off and do maintenance on my other board. but I need to break through and get this moving. at the same time trying to be ok with not moving it forward.

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#68

Martha Faulker.

I did some soul searching. and some plastic mockups… and blah. I think I kicked the idea of trying to do 12s6p 21700 in my prototipo build. I mocked up 10mm spacers and I htink I could make it work, but I’m making things too hard. so no fancy 2nd board means no fancy techniques to practice int his build either. it’s probably enough I’ve challenged myself to build two batterie and two boards. if I’m any good I can get special later. .

So I’m choosing 12s5p for that 2nd build and 12s2p for this tayto build with P42A for both.
was torn between 40Ts and P42A… but I’ve adopted the hype and selected the later. particularly for the 12s2p tayto pack which should leave me space to work with.

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#69

P42a are here.

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in addition to a take apart pack so I can practice some nickel welding before moving on to the real dealz.

Thanks @ahrav for helping source cells and the practice cells!!

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