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[WIP] 40+ km/h lego car

 

Since i like to see some ideas and open discussions, i decided to make this project public.

 

So lets start with the current progress:

A few pictures of the first tries, with the following specs:

 

- 4 motors, gearing 24:8 from low-speed-otput

- 1 PF-battery-box, attached to an old 9V switch, controlling 1 of the 4 buggy motors. Switch is controlled by a micromotor powered with the auxilary output of the rc unit.

- 3 motors powered with the RC unit

- total weight (without speed computer, to stay below the magic number :D) -> 991g (1012g with the computer)

4th motor is used as a booster, activated with the auxiliary padels, once the car reached like 15 km/h

DSCI1535.JPG

DSCI1537.JPG

DSCI1538.JPG

DSCI1540.JPG

DSCI1542.JPG

 

Fresh video, done 1 hour ago ;) (38,7 km/h) ->

 

 

Edited by TechnicSummse

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Very very fast!

Probably the fastest so far!

It is interesting how you use the low speed output :wink:

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Very fast! but you should be careful not to burn out the 9v switch - it's not designed to control buggy motors.

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6 hours ago, MattL600 said:

Very very fast!

Probably the fastest so far!

It is interesting how you use the low speed output :wink:

Thank you :)

Using the lower and the higher output allows to grade the gearing in smaller steps. While developing my 2-motor-racer, i was trying all possible gearings and jumping between high and low output while finding the perfect gearing. While using the high output only allows you the easy usage of 1,6666 / 2,0 / 2,5 and 3,0 gearing, with the lowspeed output you can go exactly between there with (compared to high output gearings) 1,48 /  1,85 / and 2,22 .

1 hour ago, mocbuild101 said:

Very fast! but you should be careful not to burn out the 9v switch - it's not designed to control buggy motors.

I got a few of them :D And they are also pretty cheap, im not afraid of that.

By the way, i made some loaded tests (not with amperemeter yet) and checked rotating speed... one times connecting the buggy-motor directly to the battery- box and the other time using an old 9V switch between there.

It seems there is no difference in rotating speed, if using a switch or not... so it should take the current easily. If the switch would be to weak, its would be a resistor there and lower the speed.

 

-> I am a little bit more afraid of frying my RC-unit with the 3rd buggy-motor attached there, since i couldnt find any informations about rc-units protection-system/max current.

But what i realised here is... powering 3 (of 4) motors with it, is faster then powering 2 or 4. So there should be some room compared to 2 motors... but 4 motors is defenetly to much for the RC-unit.... or the batteries...

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Great effort here, awesome performance and I just love the motor setup. I think you can get faster by simply replacing the normal BB with the small AAA battery box. The output voltage is the same and the weight difference is significant. Good luck with your project!

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Dude, you will burn your rc unit like this....don't say i haven't warned you... and one motor is not fully powered...

and you are still measuring on a powered wheel.....

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Just now, TechnicSummse said:

I am a little bit more afraid of frying my RC-unit with the 3rd buggy-motor attached there, since i couldnt find any informations about rc-units protection-system/max current.

You probably will, I actually thought that you had put 2 motors on the switch...

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The rc Unit has NO protection, the protection is in the buggy motors, but by attaching 3 of these motors you will greatly exceed the current the unit can handle and burn it up inside, just a small twig or rock inside the gears will do the trick.. 

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22 minutes ago, braker23 said:

Great effort here, awesome performance and I just love the motor setup. I think you can get faster by simply replacing the normal BB with the small AAA battery box. The output voltage is the same and the weight difference is significant. Good luck with your project!

I was allready thinking of this. But they cost about 20€ again.

At the moment i will try to stay with the elements i got here, and see how far it could bring me.

 

...and you are still measuring on a powered wheel.....

"Dude", please dont be so childish ;)

At first this is just a "while in progress" video, and no "official" record. At second... i told you i compared the speed computer with the 1 second mode gps... and yes yesterday again i made some runs with gps-phone...

first runs without phone-> 37,9-38,5 

attached gps-phone ->36,3 / speed computer 36,2...

after removing the phone (weight) i went again in the 38's

Yesterday you wrote the following to this....

14 hours ago, Marxpek said:

You already know i like your efforts but, i have a problem with the way you measure, should be fully gps, but when you choose the Lego computer it should be attached to a non powered wheel. But Let's not get back into that discussion ;)

... but you do it again now ;)

No matter if slipping, to big or to small set wheelsize or whatever... while comparing with gps it gives me allways the same results then the gps... so evrything is compensatet in this measuring. 

By the way... if you have a speed computer... try to fast spin a wheel attached to it by hand... what you will see is less then 1 km/h... short, even verry fast spins dont increase the speed computers counter. And even if my wheel would jump all the way... the wheelmass prevents fast accerelations wich could cause your feared problem.

And the next thing... do you have a car, or a motorcycle? Maybe an old one? What do you think at wich wheel the speedo is attached to? -> right... the driven wheel ;)

And why? Because the slipping will just appear in lower gears, while in high gears and high speeds there is close to no slipping.

___________________________________________________________________________________________________

 

9 minutes ago, Marxpek said:

The rc Unit has NO protection, the protection is in the buggy motors, but by attaching 3 of these motors you will greatly exceed the current the unit can handle and burn it up inside, just a small twig or rock inside the gears will do the trick.. 

Do you have any hard informatioins about that? I would love to see any experiments to proof that, or a circuit diagram of the rc-unit.

I've searched all arround, and couldnt find any prooven information... just a lot of guesses :(

 

 

Edited by TechnicSummse

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13 minutes ago, TechnicSummse said:

Do you have any hard informatioins about that? I would love to see any experiments to proof that, or a circuit diagram of the rc-unit

I have no link ready or something, but i found several reports of people trying the same as you and frying their unit in the process, i think one of those reports was from @Sariel, but it was all quite a while back, maybe he can confirm?

And of course there are no experiments on it, who would be willing to burn a rc unit up? But it seems you are, so let's consider your car the experiment ;D

It probably is no problem until something gets in the gears and stalls 3 motors at once (since they are hard coupled) then you will see a sudden spike in current in the rc unit, risking permanent damage.

But i must admit i am impressed by your approach, high risk, high performance car! I will accept this (your word basically since there is poor proof) as the current land speed record holder! 

But please work out your measuring.. you can NOT hook up the speed computer to the driven wheel, for at least 2 reasons: your wheels seem pretty worn off already, making them smaller, rotating faster, showing higher results on the speed computer., and any slight "jump" in the car will make the wheel spin freely for short moment.

Also think about how to prove there is no incline there (drive both ways for example)

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Why not just time them using a video over a set distance? - I have found that to be more accurate.

Edited by mocbuild101

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23 minutes ago, mocbuild101 said:

Why not just time them using a video over a set distance? - I have found that to be more accurate.

Though this very accurate and easy, it only calculates the average velocity over the set distance, not the peak velocity. Though if you record a short distance towards the end of the track where the car is fastest, this method should work well.

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On 25.6.2017 at 2:05 PM, mocbuild101 said:

Why not just time them using a video over a set distance? - I have found that to be more accurate.

On 25.6.2017 at 2:44 PM, Epic Technic said:

Though this very accurate and easy, it only calculates the average velocity over the set distance, not the peak velocity. Though if you record a short distance towards the end of the track where the car is fastest, this method should work well.

 

This defenetly would be the best way to meassure. But as you say... it must be a specific point on the track (mostly the end) where you sure reached the top speed, to not meassure the average speed.

But you would need a good high-speed-camera, to get accurate meassurings here. I guess my cam would not do a good job here :D

________________________________________________________________________________________________________

To the current progress:

Today i didnt have any good results :( 

Since the 3+1 Motors gave some nice results, i thaught downsizing could be a good idea... so i removed 1 motor+battery-box+ micromotor+ switch... to end with a light 730g 3-motor-model.

But sadly this didnt bring any good results... as you can see in the following pictures

20170625_142022.jpg

20170625_141758.jpg

It is still faster then only 2 Motors... but as it seems, the rc unit doesnt fully support the 3rd motor.

 

Little question... do you also like the orange rims? Or do you prefer the dark grey ones? :D

Edited by TechnicSummse

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5 hours ago, TechnicSummse said:

And the next thing... do you have a car, or a motorcycle? Maybe an old one? What do you think at wich wheel the speedo is attached to? -> right... the driven wheel ;)

Ok, I'm going to be blunt with this,

No, it isnt, if you have a car, look on the front wheel. It WILL have a magnet there, not on the rear, And on a motorcycle, it is on the rear, because if you wheelie, it stops the speedometer. But that is not the way you would measure, because your car does not wheelie like a motorcycle.

Check your info. Please don't make this an argument.

Edited by Aventador2004
Addition

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21 minutes ago, TechnicSummse said:

Since the 3+1 Motors gave some nice results, i thaught downsizing could be a good idea... so i removed 1 motor+battery-box+ micromotor+ switch... to end with a light 730g 3-motor-model.

It is still faster then only 2 Motors... but as it seems, the rc unit doesnt fully support the 3rd motor.

Some times, weight can be a necessary evil - in the form of more power and better traction. And talking about traction, have you tried doing with suspension?

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13 minutes ago, Aventador2004 said:

Ok, I'm going to be blunt with this,

No, it isnt, if you have a car, look on the front wheel. It WILL have a magnet there, not on the rear, And on a motorcycle, it is on the rear, because if you wheelie, it stops the speedometer.

Check your info. Please don't make this an argument.

:D 

You wanna explain me my job?

At older cars it is attached to the gearbox-output... meaning at the driven wheel... no matter if FWD or RWD ;)

Newer cars meassure with the anti-lock braking system-sensors... some systems just take 1 sensor for meassuring...others take the average of all sensors.

At motorcycles it is also attached at the rear wheel mostly. Just real old bikes using a manual speedo attached to the front wheel.

 

But you are right... this is not an argument... my argument is simply the 1:1 comparing vs gps in more then 30 runs wich gave a max-difference of +/- 0,3 km/h.

 

9 minutes ago, PorkyMonster said:

Some times, weight can be a necessary evil - in the form of more power and better traction. And talking about traction, have you tried doing with suspension?

Suspension would mean more weight again, and traction should not be a problem with this gearing, especially, since ~80% of the weight rests on the rear-axle, but i thaught about that.. i had 1 model using using springs... 

Edited by TechnicSummse

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32 minutes ago, TechnicSummse said:

Little question... do you also like the orange rims? Or do you prefer the dark grey ones? :D

Hihi look at the thing, who cares what color the rims are ;D

1 minute ago, TechnicSummse said:

At older cars it is attached to the gearbox-output... meaning at the driven wheel... no matter if FWD or RWD ;)

Newer cars meassure with the anti-lock braking system-sensors... some systems just take 1 sensor for meassuring...others take the average of all sensors.

At motorcycles it is also attached at the rear wheel mostly. Just real old bikes using a manual speedo attached to the front wheel.

The difference is these are all well suspended vehicles, so they rarely lose contact with the ground, but i will stop complaining about your measuring setup now, but i do think you should take that part a bit more serious..

38 minutes ago, TechnicSummse said:

but as it seems, the rc unit doesnt fully support the 3rd motor

"Experiment 1" ;D 

Keep it up! but don't burn it up.. i would hate to win our little contest like that...

We had an entire weekend of bad weather so i could not do any test runs yet sadly...

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1 hour ago, Epic Technic said:

Though if you record a short distance towards the end of the track where the car is fastest, this method should work well.

That's what I meant - a 1m or 2m section 3/4 of the way down the track.

31 minutes ago, TechnicSummse said:

But you would need a good high-speed-camera, to get accurate meassurings here. I guess my cam would not do a good job here :D

Not really, even a camera that films at 30fps (which is very common) would be enough for an accuracy of about +/- 2%, which at 40kp/h is only about a 0.8kp/h difference. (or at least that's what I have found...)

45 minutes ago, TechnicSummse said:

but as it seems, the rc unit doesnt fully support the 3rd motor.

Because 3 motors draw too much current from it, which will burn it out eventually.

47 minutes ago, TechnicSummse said:

Little question... do you also like the orange rims? Or do you prefer the dark grey ones?

Doesn't really matter, but the orange rims kind of make it look fast :tongue:.

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54 minutes ago, Marxpek said:

"Experiment 1" ;D 

Keep it up! but don't burn it up.. i would hate to win our little contest like that...

We had an entire weekend of bad weather so i could not do any test runs yet sadly...

The weather-thing sounds known to me ... sad to hear :(

 

I will try different gearings now... the 24:8 was just a easy to build-solution to save beams an take the motors themselves as frame for the wheels.

When trying the exactly same gearing at my 2 motor-model i just reached ~33 km/h... so maybe the motor is still full powered...if you compare it 2 motor vs 3 motor with this gearing, its a plus of ~3,5km/h ... not sure if full power only gives 3 km/h...

As long as you cannot record the currents while running... this is all just guessing :(

 

48 minutes ago, mocbuild101 said:

Doesn't really matter, but the orange rims kind of make it look fast .

Color MAKES cars faster... or what do you think... why most of the sportcars are red? :D 

Red= +20% Topspeed :tongue:

 

Well you are right... color doesnt really matter... but i like to keep this thing looking ok... thats why i also try to build symetrical...

Edited by TechnicSummse

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1 hour ago, TechnicSummse said:

You wanna explain me my job?

At older cars it is attached to the gearbox-output... meaning at the driven wheel...

At motorcycles it is also attached at the rear wheel mostly. Just real old bikes using a manual speedo attached to the front wheel.

My father is a car technician, so all the cars he works on I like to study. And they have the front spedometer on the front wheel. Sorry if I insulted you, I apologize, maybe I wasn't studying cars when they had it on the rear wheel.

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25 minutes ago, Aventador2004 said:

My father is a car technician, so all the cars he works on I like to study. And they have the front spedometer on the front wheel. Sorry if I insulted you, I apologize, maybe I wasn't studying cars when they had it on the rear wheel.

I am like a car technician... sadly i dont know the exact description of my job in english. Some one told me it would be "chief mechanic" but this doesnt fit 100%. The word by word translation would be "mechanic master"  ... i lead a garage, and i educate young people at this job ;)

What i am guessing is the following: The magnets you was talking about are the anti locking break-system-sensors. They are attached to ALL wheels. Newer cars also use them for speed meassuring... with newer i would say something like since 2005-2010. Older cars use a flexible speedometer-crank (hope this is the right word in english) attached to the gearbox-output, or a hall-sensor attached at the gearbox-output.

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1 hour ago, mocbuild101 said:

Not really, even a camera that films at 30fps (which is very common) would be enough for an accuracy of about +/- 2%, which at 40kp/h is only about a 0.8kp/h difference. (or at least that's what I have found...)

I have tried this with a camera at 60 fps on a section of 10m, it gave  very inconsistent results, so i ditched this way of measuring speed, it will also never show you the top speed.

 

1 hour ago, mocbuild101 said:

That's what I meant - a 1m or 2m section 3/4 of the way down the track

Have you already done a test run with your car? You will notice that every run is different from the next and the exact section you need to film is on a other spot on the track on every attempt. Filming for speed sounds easier then it is, (besides the fact people will distrust it since you can easily edit it faster..)

1 hour ago, TechnicSummse said:

why most of the sportcars are red? :D 

Red is the safest color car to drive, its a visibility thingy, so i do not think red it the right color for your car, since it has nothing to do with safety ;D

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56 minutes ago, Marxpek said:

so i do not think red it the right color for your car, since it has nothing to do with safety ;D

It would be good for safety if you see a speedy red RC car coming directly at you so that you can jump away!:laugh:

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3 hours ago, TechnicRCRacer said:

It would be good for safety if you see a speedy red RC car coming directly at you so that you can jump away!:laugh:

You describe a problem wich i had some times :D

_______________________________________________

Last pics for today... rebuilded the whole thing, pretty similar to my record racer. Not driven yet, but i defenetly need another bearing between the wheels... axle bends to much like this right now.

Also ground clearance could make some problems at the battery-box like this

DSCI1550.JPG

DSCI1552.JPG

DSCI1551.JPG

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11 hours ago, TechnicSummse said:

Suspension would mean more weight again, and traction should not be a problem with this gearing, especially, since ~80% of the weight rests on the rear-axle, but i thaught about that.. i had 1 model using using springs... 

Did you test out that model with springs (gotta be hard springs though...)? Weight gain should be quite negligible... no?

I do suspect that at that speed (which is "dangerously fast" relative to its size), tiny bumps (which can be many for a car that small... even on surfaces we think are flat) will send the wheels spinning the in air and lose traction momentarily regardless of weight distribution - and suspension might help to regain all that lost traction and get you to 40 km/h :laugh:.

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