I’m quite impressed with the amount of discussion my little question has started, thank y’all for being significantly less full of jerks than most of the fora I frequent.
My take-away so far:
High voltage and low kv seems to be a sweet spot for the standard size wheels(83->90mm), motors(<=65MM dia) and gearing used, allowing for a wide range of speeds without hitting a frequency limit for switching fields.
My focus is larger wheels(120->200MM and a max speed of 25mph. I’d like it to be able to lift a 280# fellow up a wall if needed. Seems like the the 1/8th scale rc motors would satisfy what I’m thinking about
The reasoning for the VESC vs RC ESCs is laggy response to input and inadquate brake tuning (too strong or too weak)
Has anyone considered that the laggy response could have been upsteam in the system (transmitter/receiver) rather than ESC?
@olestra. In USA olestra is a fat substitute that causes “anal leakage”!! I remember back when they were doing tv ads For chips with it and have to say “may cause anal leakage”. Really fast.
@Hummie bingo! I picked out the name 15 years ago for an undead warlock in WoW as I thought it was appropriately gross, having experienced the phenomena myself from a bag of chips, cooked in olestra. Disturbingly nasty, lasted for 3 days.
320a for a one cell vehicle
I’d thought more like 900a motor current needed w high kv motor needed to be similar n get to similar speed n torque as typical
one cell 4v battery, dual 900kv hubs w/ 0.0005ohm & 84mm tires, 1250a motor current limit, 690a battery current limit per motor (1380a battery combined):
As for wires,esc and battery:
There’s a quite a few ESCs – I’ll be looking into the lag of responsiveness and braking levels of what’s out there. I’m feeling like the transmitter/receiver stack might be a significant factor – it blows my mind how cheap some of these are – quality has to be suffering there – the rock-crawler RC guys might have some good data.
My batteries are going to be lipoly packs (one per 2 motors) taken from a city bus 4s2p should work.
Wiring seems like 8ga will be sufficient, I’ll look up some charts as I get further along
the body of knowledge on RC ESCs around here is probably starting to dwindle as VESC has come to dominate so much. It wouldnt be all too surprisng to me if lag is not a significant issue in most cases, a few people just had some bad experiences and those stories are being parroted. My own experience with an FVT ESC several years ago was that there was no lag at all.
That said, RC ESCs still have a major disadvantage in that they have no current limiting, so be careful, they will easily burn themselves or your motors up in high-torque situations. That’s what happened to my FVT ESC years ago, it burned up, and so I decided to give up on the whole DIY ESK8 thing until better ESCs became available.
Really curious, and really confused about this 4s build. Those motors are only 70A @5s, whereas 6374’s are about 70A @12s, so they’re about half as powerful. With 4s2p, you could easily reconfigure that to 8s1p and run a more conventional setup. The only big advantage that I can think of is that it allows you to use $40 RC ESCs that are limited to <6s instead of VESC, but you need to go 4WD to get the same power as a 2WD 6374 setup, which means you need 4 ESCs, which puts the price of the electronics very much in line with going with VESCs anyway. Are you going this direction because in-runners = protection from the elements?
@Jmding crap, misread spec. thought I was looking at 120amp nominal. time to look for different ones
I’m thinking 4wd because loose sand and gravel has ruined my day on many different vehicles. I’m not looking to be completely cheap, just the cost of 4x vesc makes me shudder a little.
I currently have a monster with go-cart wheels – got it off craigslist for 200$, it had lead-acid batteries(fixed that!) and currently has some unknown receiver and brushed esc and motor.
I like it’s size and feel, but think I can do it better/right.
doesn’t look too bad with the 4x 1900kv, 0.0074ohm, 16v (4S) & 120mm tires geared for 25mph top speed w/ 100a motor/battery limits… plenty of torque for 31.5% grade… only 100a motor current per motor required for nearly 120lbs thrust… 15:1 gearing sounds like a challenge. nearly 400a battery amps required for accelerating up 31.5% slope while passing through 25mph w/ 120lbs thrust. ~80w ohmic heating per motor seems fairly low for 120lbs total thrust.
I think there’s a thread where someone was looking into making their own Onewheel using go kart tires and they stumbled across some hubmotors that work with them. Not sure what kind of speed you’d be able to achieve and the thermals would probably be insane.
@thiswasandy looks very cool – for this application, I’m planning on staying away from hubmotors. though.
When I inevitably catch a stop sign or park bench and go superman… I’d rather deal with only a bent axle on a truck than a bent axle on a motor. well, that and whatever bones I brake
