Help. Goal to build a 50mph lego RC car

[amorti]

what if you put a buggy motor back to front in a planetary hub? You get 5500rpm odd, what wheel do you need then?

obviously it'll take a lot of power to spin that, but theoretically.

[Sariel]

1 hour ago, ukbajadave said:

4 of these bad boys should see you hitting 50 in no time.

Not to nitpick, but driving on hexagons makes for a pretty bumpy ride even at low speeds. How do you expect them to perform at 50 mph?

[ukbajadave]

Maybe offset them so one point is going down as the other comes up? Or perhaps the solution is a periodic inverted catenary path...

Once they're spinning at 50 they'll look like circles anyway 

[Zerobricks]

1 hour ago, ukbajadave said:

My copy of The Unofficial Technic Builders Guide by @Sariel lists the buggy motor specs at 9V as 1053 RPM or 780 RPM depending on inner or outer output.

50 Miles per hour is about 80.5 Kilometres per hour. Divide by 60 to get distance in one minute (to match RPM) gives us 0.83 Miles or 1.341 Kilometres. Divide distance by revolutions gives us circumference of wheel, 127.36 cm or 171.94 cm depending on output used. The circumference gives us the radius (20.27cm or 27.37cm) which we double for a diameter. Then we use Sariels Unit converter to turn it into studs. So using a directly driven axle from the buggy motor to hit 50 MPH you need wheels of approx 50 (inner drive) or 70 (outer drive) stud diameter. Obviously Lego doesn't make a wheel in this size so here is the solution.

4 of these bad boys should see you hitting 50 in no time. As a bonus they are very light weight which will help with acceleration of rotational mass.

For the sake of your safety and people around you wear eye protection when you're about to spin these. Because they will explode into a mess of plastic projectiles.

[amorti]

24 minutes ago, ukbajadave said:

Maybe offset them so one point is going down as the other comes up? Or perhaps the solution is a periodic inverted catenary path...

Once they're spinning at 50 they'll look like circles anyway 

Good to remember that not everyone shares the British sense of ironic humour!

Guys, this is a joke at the OP's expense, or let's more kindly say it's a calculation which points out the ridiculous nature of his intention (pipedream)

[ukbajadave]

Of course it would never have reached 50 

The calculation was based on circumference of a circle. Anyone can see that my wheel only has 6 sides at 25 studs each for a total of 150 studs or 120cm. Even using the faster output (1053 rpm) the best I could have hoped for was a paltry 75 Km/h (45ish)

 

Also I have no buggy motors.

Edited November 9, 2020 by ukbajadave
Everyone likes metric AND imperial units, right?

[amorti]

You're not really mixing units until you present a torque figure in cm/lb's!