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Brushless Slot cars

21967 Views 199 Replies 24 Participants Last post by  Dr_C
Hi All,

I have been looking into other hobbies recently as I saw an RC plane and thought I'd better give that a go too! Anyhow, these days all the electric motors in RC planes seem to be brushless. Is that something that we'll see with Slot Cars in the future? Are there any already?

Obviously they are more efficient and probably more reliable and have less wear, surely that'd be a good thing?

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Is the above as far as the art of brushless slot cars has developed? Or am I missing something? (Innocent question so be gentle please...)

Meanwhile I noticed recently that 16mm in-runner motors now exist... 130-size... and even they have 2mm diameter shafts. Unloaded they should spin up to 50k rpm.


Potential other benefits of brushless...

1/ candidate for slotcar land speed record challenge
2/ less wear and tear on motors... e.g no commutators/brushes/sparks inside the motor etc
3/ lower drive currents therefore more cars per amp of power supply or lower voltage drops alng the track.
4/ lower drive currents therefore lower system wear-and-tear and less pick-up arcing and so less emi radiated
5/ less heat so less chance of thermal damage to plastic car body parts
6/ more motor poles so better very slow speed running
7/ reduced vibration for a given rpm
8/ integrated tachometer for telemetry and/or governor mode operation
9/ better overall performance per $/£/euro than high end brushed motors used in slot racing.
10/ and repeating injectormans above post... reduced size... which presumably means more flexibility over where and how we mount our motors...

So maybe its not all about speed... tempting as above item 1 appears...

Not sure how many of the above list will be important as slot cars develop over the next 50 years... also not sure what I have missed... but maybe time to start our rethink...?maybe? So I am putting together a couple of test vehicles... based on in-lne and sidewinder motor pods... really just for fun at this stage and particularly as i now have access to 16mm mabuchi-sized brushless motors...

Enjoy the festivities...

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I might put brushless drive signals into next generation (independent) incar decoders... i.e. a 1-2ms pulse at 50/100 refresh rate like R/C models and compatible with brushless esc signals... just an option for anyone wanting to go down the brushless route... need to think about proportional braking control too...

Yepp... and decoder-pro version 1.0 spec includes an option for PPM input from a micro R/C receiver... so that is covered too... and the R/C receiver module (DSM2) is only 10mm x 10mm so not too bulky. We will need a special esc for proper proportional braking... then job done :)

Hi Ade... we are getting really close to being in a position to answer your question...

and we should be able to use any of these digital platforms in due course... for me DSM2 onto a firmware updated SSD decoder is the easiest starting point... but O2 and Scorpius decoders will also make an excellent platform... the breakthrough will be the firmware to control motor braking... and havng this mniaturised onto a slot-car decoder pcb... or perhaps a slave pcb which solders directly onto the brushless motor terminals... will share some photos and performance data towards end of Jan... meanwhile have a great and very festive holiday...

Shall we kick this stuff into touch for another 7 years? or press ahead developing a prototype which demonstrates the benefits?

Just to mention... in my opinion there is enough real estate on a DPR module to add two extra half H-drive circuits in addition to the circuit already present for brushed motor control... with these extra components the phasing of signals for brushless can be handled by the already onboard microcontroller. Even when operating under race conditions this microcontroller spends most of its time waiting repeatedly for the interupt service routine to be triggered...

This activity is going to be a lot of fun so will press on (over the next 7 years or less...) and report back on progress from time to time... surely the time will come when we have a race category for brushless GT...?

Enjoy the festive racing...

cylindrical brushless motors heading to my test track... 16mm diamter (similar to vertical dimension of a mabuchi 130-type motors), and same length and same 2mm shaft diameter i.e. ready for some pinion gears... and balanced for 50k rpm... and currents up to 8A... but we really wont need more than about 5% of that... (but that is guessing at this stage...)


on the motor side of the SSD decoder...

no sparks = no need for ferrite men.

... except perhaps three tiny little smd ferrite beads on the decoder pcb itself... i.e. one more than current brushed motor designs.

... and while we are redesigning the pcb for brushless lets add high speed optocouplers on the track reader side... that should take care of track transients that can confuse decoders...

Meanwhile ferrite men will still have a use in this brave new world... we will still need to suppress rf noise generated where the small sparks fly... i.e. at the track-pickup interface...

What about more cars per amp and smaller voltage drops along the track (i.e. more cars and more consistent power)?

Anyway... it feels like time to write some new decoder firmware to control brushless motors - both power and braking... lets see where it takes us... so with motors en route... next a driver circuit... three pwm inputs for brushless motor poles and one for pwm brake function...

Hi injectorman... let me try this one... lighter motors means we can add extra weight with very low centre of gravity i.e. lower centre of gravity for equally powered brushless motored cars as compared with brushed motored cars (for the same vehicle total weight). Result... like-for-like brushless will give better cornering...

I think the idea would be to have a few cars withn your collection which outperform everything brushed... take these along to your raceway and race against friends with similar brushless motored high spec racers... a new race category... why not? ... and we all love mixed portfolios/collections...

Not for today... but this looks quite a useful starting point...

If we put max power/torque/speed and the thought of batteries to one side for a moment... how about the brushless motor and decoder board together provide an identical drive system for each driver... no variation between motor performance whatsoever... this would be achievable because the brushless controller could be designed to even out motor performance differences by eliminating any observable manufacturing variability between our motors. Then, racing would come down to driver skills, layout awarenss/practice, car weight distribution, downforce, gearing, tyres, driver adjusted throttle/braking profiles... and some racing good fortune (and collision avoidance)... does this sound familiar?

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Agreed increased efficiency gives you that.

Just supposing fluctuating motor power is the real concern, is there another way of solving it?
While the lower current of brushless motors would somewhat reduce the fluctuations in track voltage, it cannot eliminate it. Some electronics in the car could deliver pretty consistent motor power even though the track voltage was fluctuating. So although we are still stuck with a fluctuating track voltage that doesn't necessarily mean we are stuck with fluctuating motor power. The simplistic approach would be to put an off the shelf linear voltage regulator in the car, but that would add mass and produce heating in the car. Redesigning the control chip to adjust the PWM so the motor delivered consistent power should add very little mass or heat in the car.
The regulator idea sounds cool. And, there are switching regulators which are far more efficient than simple linear regulators. If needed these would work nicely... they are light and they dissipate very little power so stay cool. Also, agree we could use the PWM function in the decoder to adjust for voltage fluctuations.

With my 130 sized brushless motors on route from China to Scotland, motor mounts at the ready, and compact brushless ESCs borrowed from another hobby... the fun may start soon...

I think in due course that will happen, smaller motors with higher power output. However, as a stepping stone I think motors that fit in standard motor mounts and match standard pinion shaft diameters are a useful starting point. If the 130 sized (off-the-shelf) brushless function well then I can see a case for designing something bespoke... and with the arrival of Industry 4.0 (and mass customisation) I can see the brushless motor requirements of our hobby could be met by low volume production at mass volume prices...

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Based on this discussion I can see that we can take almost any aspect of how brushless motors are known to outperforms brushed motors... we can then construct a highly plausible counter argument with respect to slotcar racing... thats what makes this subject so interesting... but it is time for a few data points on a graph...

Since I have volunteered to do some trials wth brushless configurations... a question... which should be faster...? a 911 RSR (991) with an in-line brushless motor or a 911 RSR (991) with a sidewider blushless configuration? Competition results to follow in Q1/ 2019...

So just to check... if there are long straights with gentle turns the in-line would likely be faster? While if there are lots of winds and sharper turns the sidewider would be faster and less likely to exit the track? Right?

(@Ade... it that your alto saxophone?)

Wouldn't it be better to compare the same car with bruhsed and brushless motors in the same position? Changing the motor orientation introduces more variable that might confuse the comparison.

Are you talking about a Scalex 911 RSR slot car or some other make? Perhaps those with experience of that specific car could answer the question.

There's a whole bunch of reasons why the motor orientation might make a difference to performance - for example the motor's position changes the magnetic attraction to the rails: weight distribution: gear ratio: tyre diameter: the efficiency of the gears that will fit : the stiffness of the back end. There is no general answer to which is best for all sorts of slot car.
Thank you 300SLR for such a helpful explanation of in-line versus sidewinder... so answer is try it and see or learn from others who have already tried it. Meanwhile, to answer your question, my test cars are a set of four Scalextric 911 RSR (991) with Scalextric PCR chassis. Sorry I only mentioned the brushless configurations... so yes... I will also compare with 130 sized motors at 22k, 25k and 29k (each using in-line and sidewinder configurations) as well as my flat 6 motors in anglewinder configurations (6,6-R,6-S and 6-RS).

So all angles covered... hopefully...

Thanks again for helping widen out the plan for side-by-side comparisons... I can already see 2019 being a fun year for brushless trials (regardless as to whether or not the brushless proove themselves to be winners...)... and the trusty PCR 911s should provide a perfect test platform enabling me to vary just one parameter at a time...

Happy New Year 2019

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