55 replies to this topic

[legomuppet9]

I am trying to make a very fast vehicle. Does anyone know a successful motor/gear ratio? Also, does adding an IR receiver make the motor spin slower?

Thanks in advance

[DLuders]

You didn't say what Lego motors you wanted to use, but if you use the Lego RC Buggy Motor, consider Jurgen Krooshoop's Small RC Red Racecar (with its 2:1 reduction).  It's on Rebrickable.  His Small RC Yellow Racecar uses a Power Functions XL motor geared up 1:3; it's on Rebrickable also.  He wrote that "This makes the red car considerably faster, both in accelleration":
and top speed.


    

  

[Alasdair Ryan]

If you want a fast car use the 'faster' output shaft of a buggy motor and gear it up a few times.

[D3K]

If you are making something from scratch, and your main goal is speed, I think it's important to leave fancy-schmancy stuff out of the build, to make it as light as possible! For example there is probably no need for advanced suspension on either axle.. I built Jurgens yellow small car, and it was brilliant, great fun!
I am planning on building a small fast MOC myself, and personally, I will use two xl motors on a single axle. This generates a lot of power when I've made simple test vehicles with that setup:-)

[legomuppet9]

Thanks for all the replies so far, jurgens yellow car does look good. I only have 1 xl motor and 2 m motors, so im quite restricted. Also I was wondering, does using bigger wheels make something go faster?

[Zblj]

Of course bigger wheels make model faster!

[legomuppet9]

But they require more torque to get them to top speed?

[DLuders]

The Power Functions XL motor has plenty of torque to get large wheels up to speed:

[piterx]

im about to build something with a 4 or 5 gears gearbox....probably that's the only way to have something funny to drive...we'd definetly need something like this directly by lego, in a small scale...
it would solve every torque-speed problem of our vehicles :D

[DLuders]

You could also consider building Sicil's Rally Car "Blacked" (which uses two Power Functions M-motors):

       

Edited by DLuders, 08 December 2012 - 05:08 PM.

[Alasdair Ryan]

DLuders, on 08 December 2012 - 05:07 PM, said:

You could also consider building Sicil's Rally Car "Blacked" (which uses two Power Functions M-motors):

That uses a servo motor which I don't think he has.
You should be able to build the yellow car that DBenders posted above.

[legomuppet9]

I've been building all afternoon and straight line speed is good however, it loses most of its momentum in the when steering. At the moment I am using mahjqa's basic power functions steering module. Does anyone know of a steering set up that means the model doesn't lose speed? I was thinking maybe only having one wheel at the front will improve the steering, am I right? If so, does anyone know of a neat steering system for one wheel? PLEASE NOTE: I do not have a differential.

Thanks in advance.

Edited by legomuppet9, 08 December 2012 - 08:26 PM.

[clarkdef]

I have been building a similar project, the plain truth is lego motors are weak, but the challenge of getting something that isn't designed to go fast, go fast is quite a fun task. The only thing which isn't fun is the cost of the parts, because ideally you want the best lego has to offer.

I have been using a drill motor which 9v powers nicely it's really got some power.

If you want to stay strictly lego its gonna cost, but I would say: 4x buggy motors, 2x 6272c01 Battery box and receiver, 1x steering motor, pf extension wire. This would give you awesome possibilities for a great car.  You also need transmitter and 2x ariels to go with 6272c01, it's the best option because of more running freedom outside.

Your gear ratios will depend on what tyres you use, and weight of vehicle. How fast do you want to go?

[DLuders]

fatfatfred posted this well-produced YouTube video of a "A Lego trike with Power Functions. Lights, 2 motors, radio-controlled. No steering at the front wheel; it steers by controlling the rear wheels seperately. It hardly works; the weight is at the back so it takes off with a wheelie. And the infrared signal is blocked by the roof so it reacts very slow sometimes. But who cares, it looks cool!"

[legomuppet9]

looks very interesting, however, i have the speed using my only xl motor, powering both wheels. therefore I want to be able to have steering (preferably return to centre) onto the front wheels.

[rm8]

Model in this videos use V2 receiver and buggy motor!





Only buggy motors with v2 IR;)
Nothing could compare with buggy motors. They are still on sale...use it

Edited by rm8, 10 December 2012 - 10:40 AM.

[jorgeopesi]

Here you will find a lot of information, almost too much, of one of the best. You have 3 parts.

http://www.sheepo.es...ive-rc-car.html

[legomuppet9]

unfortunately I don't have differentials or buggy motors, homever will 4WD/FWD work better?

[mahjqa]

4WD is more about traction and acceleration. Both won't be a problem on a Lego scale. Typically FWD is harder to pull off than RWD. This will add more complexity which will cost you both in size and weight, which in turn will bring down your top speed and acceleration. The only possible benefit FWD will give you is increased maneuverability, but benefits would likely be unnoticable on a Lego scale.

Fastest I built with a standard batterybox and standard motors (so no L or servo motors) is Ice Nine:



Bring down size, bring down weight, bring down complexity.

Another option; don't use a differential, but use two separate motors to power the two rear wheels. This allows for speed differences between the rear wheels (thus: better turning) and has the bonus of an additional motor. Find instructions for something like that right here:

Edited by mahjqa, 08 December 2012 - 09:51 PM.

[DLuders]

@ Legomuppet9:  You can find the individual Building Instruction steps for Mahjqa's Monster Chassis (featured in his video above) on his Flickr photoset.  Some pictures of his Ice Nine creation is in this Flickr photoset.

[allanp]

Or you could use a single rear wheel, like a trike in reverse. Using bigger wheels has the effect of gearing it up, so you would get a higher top speed but with less acceleration. One of the biggest drawbacks with lego is that you get quite alot of play or slack in the steering, which means the wheels can wobble and are not always kept pointing in the direction the car is going which slows it down alot. So try to design your steering with as little slack as possible. Use friction pins instead of frictionless pins. Try to have the axle the wheel goes onto going through a thickness greater than a single beam and have longer steering arms. You should also try to incorporate ackerman steering geometry to get the wheels pointing in the right direction. Using less grippy tryes will to the front wheels will also help.

[DLuders]

VMLN8R's Carver is a lightweight, fast creation that leans into the turns:

  

[Alasdair Ryan]

allanp, on 08 December 2012 - 10:12 PM, said:

Using less grippy tryes will to the front wheels will also help.

Yes use those they make a big difference....did you mean tyres?

[legomuppet9]

Thank you for all the replies and ideas so far! I will show a picture of my progress in the morning.

[clarkdef]

rm8, on 08 December 2012 - 08:49 PM, said:

Only buggy motors with v2 IR;)
Nothing could compare with buggy motors. They are still on sale...use it

How are you getting such a great distance on control out side? My pf only works about 2 meters from the receiver?