Experimenting with Sensored Brushless Motors

Experimenting with Sensored Brushless Motors - Printable Version

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RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 4th-Jan-25

(4th-Jan-25, 05:31 PM)Kevan Wrote: The RPM's reached will obviously depend on the length of the straight, you'd need a big track to get the max theoretical revs...or small diameter tyres.

Indeed, and a whole bunch of other traction related factors too.

And, just to add, this is not an attempt at any kind of speed record. I have two simple objectives here:

1/ to build test-cars which are capable of reliable 10m/s, 12.5m/s and (hopefully) 15m/s performance over a 5meter acceleration lane from a standing start, followed by controlled deceleration. This is for a new digital slot car system evaluation.

2/ to explore whether, with proper design of the performance envelope, that brushless motored slot cars can perform competitively with brushed motored slot cars across a wide range of slot track designs that are currently in use (i.e. home, local club, national and international).

Maybe 1 and 2 are mutually exclusive, let’s see.

c

RE: Experimenting with Sensored Brushless Motors - Kevan - 4th-Jan-25

NSR are current ISRA world champions...using brushless motors a couple of months ago... first worlds for brushless.

RE: Experimenting with Sensored Brushless Motors - Kevan - 4th-Jan-25

Here's a good graphic showing how well brushless motors fared internationally in 2024...
...it's safe to say that list will only get longer

[attachment=38886]

RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 5th-Jan-25

The last two posts nicely capture progress of brushless motors across international competitions - which is great to see - thanks for these posts.

Unless I am mistaken all of these results are achieved in the analog racing domain using sensorless motors. Please correct me if I am wrong on these two points.

The focus of this threat is digital racing and the potential application of ‘sensored’ brushless motors.

As I say, the previous two posts are helpful reference points - so again thanks.

c

RE: Experimenting with Sensored Brushless Motors - Kevan - 5th-Jan-25

Yes, analogue, non magnet, sensorless brushless outrunners.

RC cars used sensorless before sensored was available. Sensorless were 'coggy' at low speed whilst sensored were smooth from a standstill.

RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 5th-Jan-25

Yes, my approach is aimed at:

digital, sensored, in-runners.

I wonder if the reduction of ‘cogginess’ will help in digital racing?

Perhaps…

Better control in lining up on the starting grid?
Better control on R1 curves?
Better control when navigating pit lanes?
Parade laps?
Lane-changing?

It’s going to be interesting exploring this digital performance space. But that will require a sensored brushless digital decoder (stage 3 of the plan I outlined in the initial post on this thread)… so plenty to be getting on with in 2025!

c

RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 5th-Jan-25

The recent discussion on this thread has helped me to shape the details of my ‘so-called’ stage 1 experimentation. I now realise I should include some sensorless motors in the trials too. This should help to answer the questions I pose in my previous post relating to ‘cogginess’.

Recap: stage 1 uses commercially available in-runner brushless motors plus a commercial ESC (electronic speed controller). Wireless control is via a commercial Spektrum DSMR transmitter/receiver combination. Track power is either 7.5V DC or 12V DC with step-down to 7.5V via a commercial high efficiency buck converter. A smart LED as discussed elsewhere will provide stay-straight/lane-change commands to the in-track lane changer electronics.

My next post will show the hardware configuration for ‘stage 1’ plus, hopefully, some on-track results. This may take a few weeks!

Meanwhile, I'm happy for the debate to continue on this thread - that’s the way we all learn from each other :)

c

ps the unloaded max wheel RPM for the 5500KV sensored brushless motor running at 7.5V is 18,200 RPM as measured by tacho. Transmission ratio is 31:13.

RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 7th-Jan-25

[attachment=38909]

RE: Experimenting with Sensored Brushless Motors - Dr_C2 - 14th-Jan-25

All of the above electronics and the 4300KV brushless motor have been fitted into a NSR Z4 AMG and tested on the H&B rolling road testbench at 7.5V.

At full throttle the H&B testbench reads 28.2mph which corresponds to 45.1km/hr.

Converting to ‘more useful’ units this gives a testbench speed of 12.5m/s.

This of course is the rolling road speed and track maximum speed will be less. However, I am happy with this maximum rolling road speed as the basis for ‘drivability’ track-level trials. Remember this car has a sensored brushless motor so low speed running should be relatively smooth too. Also, the transmitter in use has adjustment for maximum throttle, throttle curve, and adjustable brakes.

c

RE: Experimenting with Sensored Brushless Motors - Drifter2 - 16th-Jan-25

Dr_C,
I'm wondering if your sensored motors use a magnetic angle encoder or 3 hall sensors?
Very interesting either way.