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I'd like to build city-scale (6 studs wide) vehicles motorized with either PF motor or clockwork. The primary problem right now is connecting wheel(s) to motor. Are there small enough LEGO wheels with axle hole? Any other idea on how to connect it to motor (with gears, friction, or by any other means)?

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4 Answers

up vote 9 down vote accepted

If i remember right, the tires of the small LEGO City wheels fit perfectly on a Technic 1/2 bush which then gives you an axle hole, but note that this is very flat on the ground. I don't know if its high enough to add a very small gear and build up the connection to your motor.

small city wheel

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4 studs wide seems not enough to put motor or clockwork. I meant 6 studs used in trucks, buses, SUV: they use large wheels. But this is useful info anyway. –  Denis Otkidach Oct 26 '11 at 12:29
    
if you use the 1/2 bush and add an axle on your own, you can build your vehicle as while as you like - just depends on the axle you're using. –  oezi Oct 26 '11 at 12:52
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If a gear doesn't fit, a rubber band belt would. –  Pubby Oct 27 '11 at 10:23
    
@Pubby You know they do make LEGO technic belts. –  J. Walker Jan 31 '13 at 22:54
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There are a number of pull-back motors for system wheels. Look through the Motor, non-electric section of bricklink. There is even one rechargeable electric motor.

There was also an all-rubber tire with an axle hole in some of the old space sets, though that may have a rounder shape than you're looking for.

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Most vehicles in modern city sets use wheels with ∅20×12 mm tires. Such tire can be put on 12 tooth double bevel gear or combination of narrower ∅11×8 mm wheel and 12 tooth bevel gear to connect with axle. The only problem I see with this solution is that tires are swollen a bit by gear so they are not freely turned when covered with mudguard with arch.

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Ever since this question was asked I wanted to build something that would fit that scale. Here's the result:

enter image description here

I know this is not using only LEGO pieces but, I thought that there was no way to make the LEGO motors fit 'inside' a normal looking LEGO City vehicle. So, this is basically a homemade motorized brick made of a 2x2 brick glued to the 2x2 wheels-brick. I then gutted out the insides to make place for all the electronics.

It's controlled by an ATtiny chip (similar to the Arduino chip) and uses a 3.3V LIPO battery. The motor is a small 'pager motor' that I got from an old toy. The chip is programmable and can run the motor at different speed. I'm pretty sure I could figure out a way to make a steering mechanism to go with it and, if I go really crazy, a BlueTooth brick to remote control it...

You can see it in more details in this video, see it run in this video and I have more pictures on my blog.

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+1 I was just about to edit what I thought was a typo until I looked it up. You really did mean it's a ATtiny chip. :) –  Major Stackings Dec 30 '12 at 2:34
    
In this case, an ATtiny13. I love working with this chip. I'm going to get some surface mounted ones to make even smaller projects. –  pcantin Dec 30 '12 at 13:16
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