The thing I'd worry about (and, please correct me if I'm wrong) is the stall torque on smaller brushless motors - I can't seem to find specs on motors, and when doing a rough calculation, I get in the region of 100Nm for stall torque, which seems good, although I'm not too good at math, so I'm not sure how wrong I am.
Brushless motors are weird. The reason websites won't give you a stall torque or a torque curve is because... they don't have one (for our uses anyway). The ESC you use with the motor has such a major impact on how they perform and things like the prop/wheel/tracks/impeller all give the motor a different profile. Where brushed motors deliver all their torque at 0rpm, a brushless is almost the other way around (kind of).
Stalling a brushless motor isn't the big deal that it is with a brushed motor. Most good brushless ESC's can detect the stall, or jam and will cut out. And even if it doesn't, since you are not burning out brushess and creating sparks, I've heard of massive 1500W outrunners stalled for over a minute with no ill effects.
The main issue with brushless is the higher speeds (usually). Where a bosch 750 or Mag motor outputs around 3000-4000rpm at the shaft, a brushless motor will be double or even triple that. The Rotomax 50CC's in Pulsar do around 8000rpm and the motors I am experimenting with do 20'000rpm (This higher gear ratio makes position sensing for the ESC easier and allows the motor to start spinning which gives the ESC the feedback it needs to fire the phases at the right time)
We are still tuning the ESC's we use to our motor setup and the system gets better and better, giving faster acceleration, more torque, lower start speeds and better efficiency. In a weapon setup its not so critical but it can make the difference between a 10 second spin up time and a 5 second spin up.
PS: Brushless is still new in the HW category so if you take a leap like we have then there are very few people who even have the slightest clew what is going on. But if it works the benefits seem to be... substantial!
Ah, see using brushless seems like a good option to me - the ESC side of things looks like it will be a steep learning curve - if it's alright with you, I'll reach out when we're about to wire up to ask hundreds of ESC tuning questions! One of my friends uses Rotomax 100cc ones in his helicopter (does all the crazy stunts in it), I'll ask him as well.
I wonder if some of the smaller brushless motors could work as drive motors?
If you are planning to put a machine together with the intention of getting it on the tv then I wouldn't expect a large leadtime on the build. Two months heads up was given last time with a month of actual confirmation. With that little time and the fact it's your first build stick with brushed motors. There's a good reason that 95% of machines use them.
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