Lego Scalextric cars

[dundarach]

Sorry if this is in the wrong forum, however being I'm a train person and being it's still power and motors etc. I thought this might be the place.

I have a bunch of 4.5v technic round motors - 6116m2

I want to power these from my scalextric track which is either 0-12v or newer --16v without destroying the motor.

A thought might be to use a 0-5v voltage regulator to throttle back the supply, however could I two questions of the more enlightened than me:

1. would something like a 0-5v voltage regulator give me a range from 0 to 5v to accelerate the car?

2. is there an easier way to do this?

Many thanks everyone, really want to build an all lego slot car, rather than butchering cars or lego :)

[Spitfire2865]

Im no electrics expert, but wouldnt a resistor help limit voltage?

[dundarach]

Well that's what I thought, however the internet seems to warn against this....??

[JopieK]

You could better use a voltage regulator indeed I think. That is not very difficult, then just test how it works. A resistor is a second option, but be aware that the motor might draw quite some current and makes the resistor overheat if it is not beefy enough.

Maybe those participant know more about it?!:

http://www.eurobricks.com/forum/index.php?showtopic=16969

http://home.netspeed.com.au/mephisto/bodville/bodville.html

[dundarach]

Many thanks, yes saw Bodville :) however I think he uses AFX chassis and mounts lego on top.

I think I'll wire up a voltage regulator and report back...

[Heppeng]

The easiest route would be to use the lego compatable chassis that come in the Demolition Derby set:

But that might depend on your budget - complete set is £99 I believe.

[dundarach]

Would love the demolition derby set, however would also like to try and make an entirely Lego car, motor, wheels everything and literally only take power from the tracks :)

However that set is nice and that, and the bodville site is what's now started my re-interest in scalextric - haha

I'm not interested in speed, was thinking more along the wacky races type thing, where I could build outrageous contraptions from Lego and drive them (relatively slowly) around a track.

[John Hill]

HI, a variable resistor is the cheap way of controlling motor speed and is not too bad for flat out racing as the 'throttle' is mostly open but is not near so good for low speed where the motor has greatly reduced torque. If you want good control at all speeds look for a pulse width modulated (PWM) motor speed control.

If you want to get really serious you could look at DCC (digital command and control) which is used by model railroaders.

John

[JopieK]

DCC is way too complex for such a system. I think a more simple wireless protocol is much easier. The base will then power the cars, a power regulator for the wireless logic and the 4.5V motor! The wireless logic can then use PWM to control the motor.

[dundarach]

Thanks everyone, however what I really want is simply to build an all lego car, with a 4.5v motor, stick it on the scalextric and use the controller to race as normal.

So for example, I could take my lego car to anyone's track, stick it and race, without frying the 4.5v motor by running too much power through it.

[peterab]

Many thanks, yes saw Bodville :) however I think he uses AFX chassis and mounts lego on top.

Yes, that's exactly how his cars work.

Thanks everyone, however what I really want is simply to build an all lego car, with a 4.5v motor, stick it on the scalextric and use the controller to race as normal.

So for example, I could take my lego car to anyone's track, stick it and race, without frying the 4.5v motor by running too much power through it.

I'm not familiar with Scalextric controllers any more but I have a suggestion which may work. If I remember correctly the controllers contain a variable resistor which are powered from a fixed voltage DC supply. If you replace the supply with a 4.5 supply, you could use the existing controllers. Another option is to add in a 4.5V voltage regulator between the existing 16V supply and the controllers. Both these solutions mean you would have to bring your own supply to other peoples track, which is less than your ideal, but both solutions should be relatively easy to design and impliment.

[dundarach]

Peter cracking idea about simply lowering adapter value....!

That must be worth a try as I'm only using old style classic track anyway therefore only 1 car to 1 lane etc...

I'll have a little playing around and report back :-)

[kieran]

If you hope to race / drive alongside a standard car you really need to keep the voltage drop in your LEGO car. If you know the max current at 5V for the motor you want to use and the max voltage applied to the track you can calculate the voltage drop and current handling of a resistor, if you know that you can calculate the power you need to dissipate in the resistor. If you can fit a big enough resister in the car with no risk of it melting the LEGO then for a simple solution this could well be the way. The variable voltage will come form the trigger controller anyway, all you want to do is only allow the LEGO motor to see 1/3 roughly of what ever the voltage is on the track, then you get speed control as well.

if you used a fixed voltage regulator to get to =5V in the car, it will only ever go at one speed if the supply voltage is above 5V + 1.2V drop over the reg, as the voltage drops below this the regulator will become erratic and not deliver a very smooth voltage/current. if you wanted to make a variable supply to the motor based on varying input voltage this can be done but is much more work.

hope that helps a little.

[dundarach]

Kieran

Thanks, no not really looking to compete with non lego cars, simply have a bit of fun.

However yes this helps, I've gone for a 100ohm 10w ceramic resistor which I'm going to wire up tonight and see what happens as a rough trial.

i'll let you know.

I simply fancy building some cars and trying them out, however using nothing except the guides and everything else stock lego.

Chris

[kieran]

10W will handle the heat I think, do you know the coil resistance of the 4.5V motor?

[dundarach]

A quick update.

After trying various 10w wire wound resistors, actually the one which 'appears' to work the best is a 10w 10ohm wire wound.

This give me control and provides enough power for the motor to run.

Whether or not something goes pop, we'll see.

Also everything is stock, so no modifications to Scalextric or Lego parts, except the guide blades meeting the Lego :)

See what you think, prototype one...

Next step is to improve gearing and hide the resistor.

[kieran]

Fantastic, looks great fun

[dundarach]

Really got the bug now :)

[kieran]

Can see why, this looks like a lot of fun

[elicend]

As a slot fan, i must follow this topic !

[dundarach]

Quick update:

Sorry for the dreadful video, space is tight in the Lego room, I'm going to move out into the lounge at weekend for a day or so...

[Commander Turtle]

These look like great fun, I'd love to make a car if I had the rest of the setup.

[spzero]

would it not be better to use the 12v version of motor instead then you have full power and no resistor

[tbroyd]

Really interesting reading your thread. I have been using the scalextric Demolition Derby cars shown above as a basis for some cars and would like to progress to making the chassis from Lego

[dundarach]

Yes the 12v motors would be ideal, however don't have any of these :)

It's more proving that they are indeed usable and can actually be driven, which they can and sound great.

Slightly bigger track:

I will try and get some better video