[WIP] Super Fast Speedcar - current top speed: 32.4km/h

[TechnicSummse]

44 minutes ago, Marxpek said:

Most dc motors have their maximum power at 75% of their maximum rpm, so that sounds about right.

It is like a gearbox, me cycling would be like first gear and the motors on the car are like the 2nd gear, the car cannot drive away on its own in the 2nd gear because it needs more torque, which is doesn't have available. Should i bring it up to speed with a bike it will need less torque to get the gears turning since it already is in motion, this is the whole reason we are using gearboxes in cars right? to get a car moving up to a certain speed then use another gear ratio and repeat. 

But who knows maybe i'm looking at it wrong, of course there is a top on the power any motor can deliver and resistances will grow with speed..

You CAN start moving your car in the 5th gear... well this would cause some smelly clutch problems... :D

But at the end you can start driving in the 5th gear... this will just take hours of acceleration, wich is not really good, if you drive to another road... sometimes you should be quick here... other cars could come along :D

But in your car you are using a combustion-engine. Combustion engines need a minimum rpm to not go out. DC or AC motors can theoretically run with 1 rpm, thats the difference.

 

But to look at it from your point of view... why you dont gear up 5:1... because this will lower your top speed. But at 5:1 you will still be able to start the car.

[mocbuild101]

11 hours ago, TechnicSummse said:

Long time ago, when i started this project, i checked all so far records, and the gearing-setup there. I calculated speed + wheel diameter + gearing at all those models... what i endet at, was a output rpm of 900-1100 on each of them; meaning the limit is at about 3/4 of the maximum unloaded motor-rpm.

I'd say that is probably about right, the motors will never get up to full rpm.

8 hours ago, Marxpek said:

But who knows maybe i'm looking at it wrong, of course there is a top on the power any motor can deliver and resistances will grow with speed..

Exactly, because when you gear up, any resistance on the output axle will be multiplied on the motor's axle - so gearing up 2:1 will double the resistance, and gearing up 5:1 will be 5x the resistance - which is a lot!

7 hours ago, TechnicSummse said:

But in your car you are using a combustion-engine. Combustion engines need a minimum rpm to not go out. DC or AC motors can theoretically run with 1 rpm, thats the difference.

But you can stall the electric motor if you gear up too much - in fact, even with a load that allows the motor to turn can still draw so much current (up to 6.4A for just 2 buggy motors) that the RC unit will shut down, stopping the car. (of course it will start up again, which will then cause a hiccup behavior)  

[mocbuild101]

After my last car I had a goal to lose weight - and I succeeded! - in fact, I managed to lose a whopping 110gm!

I also used the idea @Marxpek suggested - putting the front wheels through half beams to reduce friction.

So here it is: - 2:1 gearing, 670gm

Here is the results of the tests:

And yes, I have increased my top speed to 28.4km/h!

But I don't think I got the full speed from this car - because it was so unstable, it kept flipping over halfway down the track - every time I tried it!

If I can get all the way down the track, I think I could get above 30km/h! - but I will have to redesign it first...

Edited July 3, 2017 by mocbuild101

[TechnicSummse]

 

6 hours ago, mocbuild101 said:

After my last car I had a goal to lose weight - and I succeeded! - in fact, I managed to lose a whopping 110gm!

I also used the idea @Marxpek suggested - putting the front wheels through half beams to reduce friction.

 

 

Im sure, you can reduce more :D

My record-reacer weights 620g. But at one point i realised, the biggest weigth difference comes from wheels. Beams are really leightweight compared to that.

You can reduce from 2 to 1 wheel at the front, wich would also help you reducing rolling resistance.

 

Quote

 

And yes, I have increased my top speed to 28.4km/h!

Congratulations, you are on the right way :D

Quote

But I don't think I got the full speed from this car - because it was so unstable, it kept flipping over halfway down the track - every time I tried it!

If I can get all the way down the track, I think I could get above 30km/h! - but I will have to redesign it first...

you have a verry short wheelbase, the way you mounted the motors. A longer wheelbase means your car will be more stable. 

Also center of gravity seems verry high at the pictures. 

Think about these 2 points... this will help you getting your car stable on the street :)

 

Quote

So here it is: - 2:1 gearing, 670gm

You are using 40:20, right?

Try a 24:12 here, and use the motors pinholes to go trough with the axle.

Like this you can easily reduce your center of gravitiy

Edited July 3, 2017 by TechnicSummse

[mocbuild101]

4 hours ago, TechnicSummse said:

Im sure, you can reduce more :D

My record-reacer wieghts 620g. But at one point i realised, the biggest weigth difference comes from wheels. Beams are reaaly leightweight sompared to that.

You can reduce from 2 to 1 wheel at the front, wich would also help you reducing rolling resistance.

I am weighing it with the watch (that is 45gm) attached, if I take that off, it only weighs 625gm - only 5gm more than yours.

 

4 hours ago, TechnicSummse said:

you have a verry short wheelbase, the way you mounted the motors. A longer wheelbase means your car will be more stable. 

Also center of gravity seems verry high at the pictures.

Yes I know, and I have already made a new car that has a longer wheelbase and a center of gravity that is much lower to the ground.

 

4 hours ago, TechnicSummse said:

You are using 40:20, right?

No, I am using 24:12, like this:

 

[TechnicSummse]

42 minutes ago, mocbuild101 said:

No, I am using 24:12, like this:

Ahh.. thats what i meant how you should use it :D 

Im just a little bit confused of that, because you wrote the following to my 40:20 gearing:

5 hours ago, mocbuild101 said:

And you also have the same 2:1 gearing that I used in my 670gm car

Maybe, i just misunderstood you :)

______________________________________________

42 minutes ago, mocbuild101 said:

No, I am using 24:12, like this:

BUT... you are using the lower pinholes... you should use the upper pinholes of the motor... and center of gravity-problem is solved ;)

 

43 minutes ago, mocbuild101 said:

Yes I know, and I have already made a new car that has a longer wheelbase and a center of gravity that is much lower to the ground.

Sounds promising again :D

Cant wait to see some more of your nice and clean pictures... i need a big white paper and some LEDs...

[mocbuild101]

On ‎3‎/‎07‎/‎2017 at 9:45 PM, TechnicSummse said:

Im just a little bit confused of that, because you wrote the following to my 40:20 gearing:

Oops! 

On ‎3‎/‎07‎/‎2017 at 9:45 PM, TechnicSummse said:

BUT... you are using the lower pinholes... you should use the upper pinholes of the motor... and center of gravity-problem is solved ;)

I didn't do that with this car because the axle would have gone though more beams, but I have done that in my latest car - which I will be testing tomorrow.

 

Edited July 4, 2017 by mocbuild101

[mocbuild101]

Because of the bad weather, I didn't do any tests today - so I did some brickstorming and redesigned my steering system again.

I might have lost a good design, but that's probably for the better... because after I changed to smaller wheels, my ground clearance dropped to only about 1 stud - which could have been bad if I had hit a stone while testing!

I have also now used @TechnicSummse's idea and changed to only 1 wheel on the front - which really cut down the weight! - it's now 635gm, or 590gm without the watch.

 

Old steering: (from above)

New steering: (from below)

Edited July 5, 2017 by mocbuild101

[Marxpek]

On 3-7-2017 at 7:36 AM, mocbuild101 said:

But I don't think I got the full speed from this car - because it was so unstable

gps data can show this, just look closely at your time-speed graphic and extrapolate the graph from where you crashed, dc motors generally show a near perfect half parabolic curve in this graph (on a straight run)

 

2 hours ago, mocbuild101 said:

my ground clearance dropped to only about 1 stud

did you drop the rear as well? I don't think it is any use to lower the front but not the back.. 1 stud should be no problem but i would not go under and always check your track for debris. 

Be careful with the 3 wheel setup, think about what will happen when it tilts/crashes (hitting buggy motors or the unit unit on the ground at 30 km/h will cause severe scrapings or even worse, i'm always most worried about the battery lid getting hit) i have used axle outriggers, 3L pins and the smallest wheels i could find for protecting key position on the car so none of these items can get hit, or at least take some impact away from them...

here is an idea for weight reduction: remove the wristband from the watch..

[mocbuild101]

10 hours ago, Marxpek said:

On 03/07/2017 at 3:36 PM, mocbuild101 said:

But I don't think I got the full speed from this car - because it was so unstable

gps data can show this, just look closely at your time-speed graphic and extrapolate the graph from where you crashed, dc motors generally show a near perfect half parabolic curve in this graph (on a straight run)

What I meant is that I could never use the full length of track - because it kept crashing. (flipping)

 

10 hours ago, Marxpek said:

did you drop the rear as well? I don't think it is any use to lower the front but not the back.. 1 stud should be no problem but i would not go under and always check your track for debris.

Yes, but it has about 2 studs of clearance.

 

10 hours ago, Marxpek said:

Be careful with the 3 wheel setup, think about what will happen when it tilts/crashes (hitting buggy motors or the unit unit on the ground at 30 km/h will cause severe scrapings or even worse)

Yes I know, I will be putting some tape on the edges of the RC unit. (the buggy motors are protected by the wheels)

 

10 hours ago, Marxpek said:

here is an idea for weight reduction: remove the wristband from the watch...

Why didn't I think of that!

 

But anyway, no tests today... (it's been raining - again!)

[TechnicSummse]

21 hours ago, mocbuild101 said:

New steering: (from below)

I used a steering system pretty similar to this :D Thin triangle-beams are just awsome 

[mocbuild101]

I have finally been able to do some tests today! - and that's not the only reason why I'm happy...

 

But first, here's what my new car looks like...

It now includes @TechnicSummse's suggestion to use a single wheel on the front, and @Marxpek's idea to remove the wristband from the watch.

And here it is: - 2:1 gearing, 615gm (590gm without the watch)

Here is the results of the tests:

Yes, 32.4km/h!

But as you can see, I only did one test... look in the spoiler below to find out why!

Spoiler

This photo was taken just after the test:

Yes, that's right, I crashed! - into a very sturdy wooden post!

But rather surprisingly, I only broke one pin: 

If you want to see more, check out my Damage Gallery - it has photos of all the damage I have done so far.

 

[Bostons Brick Closet]

On 7/1/2017 at 10:42 PM, Jurss said:

I'am planning to build pure pullback thing (i have some 4 new and 3 old type), but have other projects at the moment, so justy don't have time for it.

I have also been thinking about doing something simalar to this, Planning to get a few of the new pull back motors of bricklink so I'll have 4 of the same kind and attach them. I hope this will provide the speed I need. It seems like it should work quite well as I will not need to carry the 6 batteries. What exactly were you thinking?

[jam8280]

In rubber tires, rolling resistance is mainly a matter of sinkage, sidewall flexure, and contact patch area. Your balloon tires may have less rolling resistance than you might think -- at least on cold, hard, smooth surfaces where sinkage isn't an issue. The contact patches are largely limited to the tread's narrow central ridge on such surfaces and are therefore quite small. In addition, there won't be much sidewall flex in a vehicle this light as long as the tires stay cold and the surface stays flat.

These ideas are borne out by the testing I've done with different wheel/tire combinations on the 2 cars below. (Details on the red and yellow cars at http://www.moc-pages.com/moc.php/430234 and http://www.moc-pages.com/moc.php/429695 , respectively.)

The 279 g red dragster is my fastest no-frills top-speed car to date at an average speed of ~17.3 kph over a 9.1 m course with rather rough pavement. If acceleration were constant -- and I'm sure it's not -- top speed would have been twice that, or ~34 kph. Still a far cry from 40 kph, I know, but I'm sure my top speed, whatever it was, would have been faster on a longer course with a smoother surface.

 

 

Bottom line: If you generally run on cold, hard, smooth surfaces, and if balloon tires give the drive wheels a diameter that lands your motors near the peak of their power-speed curves as the car tops out, then you may want to keep them.

The red dragster's top speed fell dramatically when I switched the drive wheels to the newer motorcycle wheels and tires with smoother treads -- probably because the larger drive wheel diameters took the single Race Buggy motor out of its sweet spot and added too much to the drive wheel moments of inertia.

v All that said, the 559 g yellow car is faster on asphalt with the big ZR wheels seen here, but traction becomes a big issue on smoother surfaces.

Edited August 18, 2017 by jam8280

[TechnicSummse]

6 hours ago, jam8280 said:

In rubber tires, rolling resistance is mainly a matter of sinkage, sidewall flexure, and contact patch area. Your balloon tires may have less rolling resistance than you might think -- at least on cold, hard, smooth surfaces where sinkage isn't an issue. The contact patches are largely limited to the tread's narrow central ridge on such surfaces and are therefore quite small. In addition, there won't be much sidewall flex in a vehicle this light as long as the tires stay cold and the surface stays flat.

These ideas are borne out by the testing I've done with different wheel/tire combinations on the 2 cars below. (Details on the red and yellow cars at http://www.moc-pages.com/moc.php/430234 and http://www.moc-pages.com/moc.php/429695 , respectively.)

The 279 g red dragster is my fastest no-frills top-speed car to date at an average speed of ~17.3 kph over a 9.1 m course with rather rough pavement. If acceleration were constant -- and I'm sure it's not -- top speed would have been twice that, or ~34 kph. Still a far cry from 40 kph, I know, but I'm sure my top speed, whatever it was, would have been faster on a longer course with a smoother surface.

 

 

Bottom line: If you generally run on cold, hard, smooth surfaces, and if balloon tires give the drive wheels a diameter that lands your motors near the peak of their power-speed curves as the car tops out, then you may want to keep them.

The red dragster's top speed fell dramatically when I switched the drive wheels to the newer motorcycle wheels and tires with smoother treads -- probably because the larger drive wheel diameters took the single Race Buggy motor out of its sweet spot and added too much to the drive wheel moments of inertia.

v All that said, the 559 g yellow car is faster on asphalt with the big ZR wheels seen here, but traction becomes a big issue on smoother surfaces.

 

There are also other facts you mentioned your other post but forgot here. One big point is the axle/bearing-friction, wich increases dramaticaly with higher rpm(smaller wheels).

Another point, wich only shows on high speeds is tire ballooning, like you can see in my video below:

We testet many wheels and it seems the one and only working wheel for our purpose is the newer motorcycle racing tread wheel.

Edited August 18, 2017 by TechnicSummse

[mocbuild101]

14 hours ago, jam8280 said:

Your balloon tires may have less rolling resistance than you might think

It's not that I think they are worse, it's that they are worse! - I only got 22.7km/h out of the balloon tires, which is almost 10km/h less than my current top speed (32.4km/h).

7 hours ago, TechnicSummse said:

There are also other facts you mentioned your other post but forgot here. One big point is the axle/bearing-friction, wich increases dramaticaly with higher rpm(smaller wheels).

This is right, especially for the high RPM of small wheels.

And by the way, I haven't given up beating you 34.8km/h record just yet, it's just been put aside for a while... (mainly because of the sorting of my Lego, but also because of TC12)

[TechnicSummse]

3 hours ago, mocbuild101 said:

And by the way, I haven't given up beating you 34.8km/h record just yet, it's just been put aside for a while... (mainly because of the sorting of my Lego, but also because of TC12)

Nice to hear :D

Same here... i just was at vacations, but i will start rebuilding soon. Today my present to my self arrived.... another 8366-set :D

So i can test now the difference of powering 3 motors from 1 or from 2 units.

Also this means i own 6 motors now... and i will build a 6 motor car... but far far in the future. For now i will rebuild until i reached the 40 kph with just 4 motors.

I will make a post in my topic later, with some pictures

[jam8280]

12 hours ago, TechnicSummse said:

There are also other facts you mentioned your other post but forgot here. One big point is the axle/bearing-friction, wich increases dramaticaly with higher rpm(smaller wheels).

Another point, wich only shows on high speeds is tire ballooning, like you can see in my video below:...

We testet many wheels and it seems the one and only working wheel for our purpose is the newer motorcycle racing tread wheel.

Added power lost to bearing friction is certainly a valid concern with a smaller drive wheel, but if that wheel also puts your motors closer to the peaks on their power-speed curves as the car approaches top speed, the smaller wheel could be worth the extra loss. My point is that in playing trade-offs like this with so many interrelated parameters involved, guessing isn't as safe as testing in a carefully controlled fashion.

Hmmm, hadn't thought about floating tires on their wheels. Was the tire in the video spinning at a speed comparable to that when the car is near full speed? 

[TechnicSummse]

2 minutes ago, jam8280 said:

Added power lost to bearing friction is certainly a valid concern with a smaller drive wheel, but if that wheel also puts your motors closer to the peaks on their power-speed curves as the car approaches top speed, the smaller wheel could be worth the extra loss. My point is that in playing trade-offs like this with so many interrelated parameters involved, guessing isn't as safe as testing in a carefully controlled fashion.

Hmmm, hadn't thought about floating tires on their wheels. Was the tire in the video spinning at a speed comparable to that when the car is near full speed? 

Well... as you saw yourself, you drove ~17 kph... we are doing 30+... so there is a lot of power left with those small wheels... at the end you would need to gear up those wheels like 3 time higher, then i need to gear a motorcycle wheel. Ending in 3 times higher axle friction at the same speed.

And tire-size doesnt really matter, since you must see it just as a part of the total gear ratio. The smaller the wheel, the higher you must gear for the same speed. The same counts for torque.

So using small tires just adds axle-friction without any benefit ;)

 

By the way... the balloning tire rotatet at ~2300rpm... with this wheel-size i would need 2600 rpm to reach my wished 40 kph... so it rotatet even slower then it would be needet...

[jam8280]

4 hours ago, mocbuild101 said:

It's not that I think they are worse, it's that they are worse! - I only got 22.7km/h out of the balloon tires, which is almost 10km/h less than my current top speed (32.4km/h).

Thanks, that's certainly an important data point. I'd like to know a little more.

Q1: Besides drive wheel diameter, what else changed when you changed the wheels?

Q2: Did you regear to compensate for the wheel diameter change?

Q3; What was the motor shaft speed near top speed with each drive wheel type?

[mocbuild101]

On 8/19/2017 at 4:30 AM, TechnicSummse said:

Same here... i just was at vacations, but i will start rebuilding soon.

So that's why you haven't been building, but what about @Marxpek?

On 8/19/2017 at 5:50 AM, jam8280 said:

Thanks, that's certainly an important data point. I'd like to know a little more.

1. Besides drive wheel diameter, what else changed when you changed the wheels?
2. Did you regear to compensate for the wheel diameter change?
3. What was the motor shaft speed near top speed with each drive wheel type?

1. I removed the pullback motor and reduced the weight by 165gm.
2. No.
3. I think it was, because it was at maximum speed/power.

By the way, you can actually find all the specs you need in the posts I have made.

The slowest one (with balloon tires) here: https://www.eurobricks.com/forum/index.php?/forums/topic/151974-wip-super-fast-speedcar-current-top-speed-324kmh/&do=findComment&comment=2819451

And the fastest one (so far) here: https://www.eurobricks.com/forum/index.php?/forums/topic/151974-wip-super-fast-speedcar-current-top-speed-324kmh/&do=findComment&comment=2821429 

 

Edited January 17, 2018 by mocbuild101

[jam8280]

3 hours ago, TechnicSummse said:

Well... as you saw yourself, you drove ~17 kph... we are doing 30+... so there is a lot of power left with those small wheels... at the end you would need to gear up those wheels like 3 time higher, then i need to gear a motorcycle wheel. Ending in 3 times higher axle friction at the same speed.

And tire-size doesnt really matter, since you must see it just as a part of the total gear ratio. The smaller the wheel, the higher you must gear for the same speed. The same counts for torque.

So using small tires just adds axle-friction without any benefit ;)

 

By the way... the balloning tire rotatet at ~2300rpm... with this wheel-size i would need 2600 rpm to reach my wished 40 kph... so it rotatet even slower then it would be needet...

You've clearly faced problems that I have yet to encounter. The tire ballooning issue isn't just theoretical.

For the record, that 17 kph figure is the red dragster's average over an 11 m rough asphalt course from a standing start. My top speed has to be higher and could be higher by 50%. Still no match for your top speed, but closer to your territory.

I'm aware of the relationship between drive wheel diameter, gearing, and drive wheel torque. When you guys change drive wheel diameter, do you actually do the regearing you described? And with available gears, how close do you come to the final drive ratio exactly compensating for the change in wheel diameter?

Ideally, to maximize top speed, you want your motor shaft speeds to level off at 40-60% NLS (no-load speed) to get maximum mechanical power out of them. In the absence of tire ballooning, if smaller wheels were to take the final motor shaft speed from, say, 30% to 40% NLS, the added final power might outweigh the added bearing friction due to higher shaft speeds throughout the drive train. If the smaller wheels were to take your motors from 60% to 75% NLS, on the other hand, they'd definitely be robbing you of power at the motors.

Has anyone run into thermistor heating inside the Buggy motors?

Gear too high or use drive wheel diameters that are too large, and the thermistors will start to heat up as the motors draw more current to supply the additional torque at full throttle. In my experience, the thermistors don't shut down all at once. Instead, they limit motor currents gradually as they heat, and that could impact top speed as well.

I ran into this problem with the red dragster when I switched to the larger new motorcycle wheels and a AAA box with disposable lithiums (total 6 x 1.8 = 10.8V) in lieu of the PF LiPo battery (7.4V). The thermistor in the motor started limiting current after 2-3 speed trials. When I put the car in the fridge for a while, the thermistor revived.

[TechnicSummse]

2 hours ago, jam8280 said:

I'm aware of the relationship between drive wheel diameter, gearing, and drive wheel torque. When you guys change drive wheel diameter, do you actually do the regearing you described? And with available gears, how close do you come to the final drive ratio exactly compensating for the change in wheel diameter?

Well i personally DID regearing with every other small thing i changed, including wheels. I startet (like @Marxpek also did) with the 108mm claas xerion wheel and testet different gearings until i reached top speed with it. They require for sure a lower gearing then the 94.2mm motorcycle wheels.

As comparasion:

- The Claas Wheel has the best results with an upgearing of 1,666:1 (20:12) at the highspeed output. If you gear it lower, you will gain acceleration, but loose speed... if you gear it higher (2:1 for example), you will loose acceleration AND speed, since there is not enough torque left, to reach the 50% NLS.

 

- The 94.2 motorcycle wheels seem to have the best performance with an upgearing in the 2:1 range.

(there are at least 2 reasons for this... first the wheel diameter, wich can be calculated as part of the gearing, as i wrote before, AND the lower rolling resistance) 

The rubber of those (class and motorcycle) wheels seem to be pretty much the same HARD rubber. 

 

It seems there is NO other usable wheel then one of those, because other wheels are much smaller and have softer rubber, wich causes more rolling resistance and ballooning.

 

But for sure, there are also other things wich influence the perfect gearing, like amount of motors, weight, axle bearings (amount of beam-holes the axle goes trough) and so on.

Quote

if smaller wheels were to take the final motor shaft speed from, say, 30% to 40% NLS, the added final power might outweigh the added bearing friction due to higher shaft speeds throughout the drive train.

No, because you could also use a lower gearing with the big wheels to reach this.

As mentioned before, use a 1.666 upgearing with 108mm claas wheels instead of a 2.0 upgearing

Quote

Has anyone run into thermistor heating inside the Buggy motors?

I did not while my runs... just with stalling tests.

Quote

Gear too high or use drive wheel diameters that are too large, and the thermistors will start to heat up as the motors draw more current to supply the additional torque at full throttle. In my experience, the thermistors don't shut down all at once. Instead, they limit motor currents gradually as they heat, and that could impact top speed as well.

I ran into this problem with the red dragster when I switched to the larger new motorcycle wheels and a AAA box with disposable lithiums (total 6 x 1.8 = 10.8V) in lieu of the PF LiPo battery (7.4V). The thermistor in the motor started limiting current after 2-3 speed trials. When I put the car in the fridge for a while, the thermistor revived.

I bet it was not the motor thermistor, but the current limiter of the batterybox. All regular lego battery boxes have a built in protection, wich limits current to ~700mA. The old 9V boxes current limit is even lower. The only real power suply for buggy motors is the RC-unit.

Keep in mind, one single buggy motor has a stalled current of ~3,5A. Wich means you would need at least 2 battery boxes paralleled to fully suply just 1 buggy motor.

Edited August 19, 2017 by TechnicSummse

[jam8280]

7 hours ago, TechnicSummse said:

I did not while my runs... just with stalling tests.

I bet it was not the motor thermistor, but the current limiter of the batterybox. All regular lego battery boxes have a built in protection, wich limits current to ~700mA. The old 9V boxes current limit is even lower. The only real power suply for buggy motors is the RC-unit.

Keep in mind, one single buggy motor has a stalled current of ~3,5A. Wich means you would need at least 2 battery boxes paralleled to fully suply just 1 buggy motor.

Yes, I'm aware of all that. I thought it might be the battery, too. But while the car wouldn't move (i) the battery light stayed on, (ii) the battery toggled off and on normally, (iii) the battery could still power a test motor through the SBrick just fine, and (iv) the still car still wouldn't budge with a fresh battery installed.

So the SBrick and battery weren't to blame, and that leaves only the motor. Philo's dissections have confirmed that the Buggy motor's only overcurrent protection is a thermistor, and the motor "brown-outs" and shutdowns I've observed with my cars and in other settings have all been entirely consistent with the heating and cooling of a thermistor.

For those who haven't had the pleasure, when I've tripped the overcurrent protection in PF LiPos in my boats, the battery lights always went out, and the batteries wouldn't turn back on until they'd been recharged. Others have reported the same behavior. But none of that happened here.

Edited August 19, 2017 by jam8280

[TechnicSummse]

9 minutes ago, jam8280 said:

Yes, I'm aware of all that. I thought it might be the battery, too. But while the car wouldn't move (i) the battery light stayed on, (ii) the battery toggled off and on normally, (iii) the battery could still power a test motor through the SBrick just fine, and (iv) the still car still wouldn't budge with a fresh battery installed.

So the SBrick and battery weren't to blame, and that leaves only the motor. Philo's dissections have confirmed that the Buggy motor's only overcurrent protection is a thermistor, and the motor "brown-outs" and shutdowns I've observed with my cars and in other settings have all been entirely consistent with the heating and cooling of a thermistor.

For those who haven't had the pleasure, when I've tripped the overcurrent protection in PF LiPos in my boats, the battery lights always went out, and the batteries wouldn't turn back on until they'd been recharged. Others have reported the same behavior. But none of that happened here.

You are right... the battery-light should turn off then.

Hmm.. but thats really strange then... maybe your motor is used to much, and the thermistor is kind of damaged? Because as wrote earlier, even with 2:1 geared claas wheels i couldnt trigger the motors protection. And this is really hard work to push ~900g with 2:1 upgeared claas wheel. Did you try another motor?

At wich temperatures did you do your runs? 30°C and more?

By the way... the protection should recover really fast (~10-15 seconds max)

Edited August 19, 2017 by TechnicSummse