Fitst PF technic car [MOC]

[Daniel-99]

Hello everyone, today I will tell you a sad story about my first attempts in lego technic RC.

Lego technic set 9398 was my dream since I like really like both RC cars and lego. And then I get one I was totally disappointed! 9398 set was a slow turtle that stops in front of any "decent" obstacle. At first, I tried to deal this problem by changing gears and it gives a result, but the car became a super-slow turtle...

After that I decided to motorize a 42029 Pick up set with motors from 9398 set, but  the car had not enough power as well... The wheel were too big and heavy for two motors... (at least I thought that in my early days).

Finally I understood that the smaller wheels car has, the easier it will be for motors to move the car... And I decided to build a car with the smallest wheels possible!

The car is assembled form the 3 sections: front wheels with steering rack, rear axle and the middle part with all the motors emplaced.

Technical specs:

1 steering with servo-motor

2 propulsion with L-motor

3 PF battery box and receiver 

Here you likes it... This is my first "finished" motorized technic MOC !

[TechnicRCRacer]

Interesting model! I like how you built the front steering, very strong and clever. I've never seen a remote control with that type of steering linkage, neat! I would recommend usign a differential gear in the real axle and slightly larger wheels would not detract much from the motor's strength.

[Gray Gear]

Everybody starts small, and this certainly is a small start. But that's how you gain experience 

Adjusting the wheel size is not really a good solution. The gearing in the drivetrain is what matters in determining how the motor's power get to the wheels.

[Hrafn]

Small cars definitely can have an advantage in the power to weight ratio.  I agree with @Gray Gear that you could go larger on the wheels - you should have enough torque not to stall the motors even with larger wheels.

[Johnny1360]

Great to see you finished it, something I should do more of myself, I always seem to abandon projects once I get about half done, lol.

I am sure that now that you have finished, you are ready to start the next one which will be ten times better, having learned from the first one.

Now that you have finished your first one you have opened up Pandora's box, good luck and have fun, that's what it's all about.

[Daniel-99]

This steering system fixes the wheel axle in the hub for the length of 2 studs. That helps a lot with stability, but... the scrap radios is too big, since I did not figured out how to make the steering point next to the wheel. The improved version of this idea you can find in my other build (RC mod of Chevrolet Corvette).

This car has no differential, since I had non of those at that time... But if there was one available, it would not fit to the rear axle since its bigger diameter is as big as the diameter of wheels!

Gear ratio solves the problem of big wheels only by half. If I lower the motor with gear combination I will loose a lot of power with friction! And even if I lower the speed, all plastic axes and gears will struggle with big torque!... 

[Hrafn]

8 hours ago, Daniel-99 said:

Gear ratio solves the problem of big wheels only by half. If I lower the motor with gear combination I will loose a lot of power with friction! And even if I lower the speed, all plastic axes and gears will struggle with big torque!... 

With proper bracing, mating spur gears (especially double bevel ones as spur gears) should not introduce much friction.  But bracing takes space, which you don't have much of in this small model!

[Gray Gear]

9 hours ago, Daniel-99 said:

And even if I lower the speed, all plastic axes and gears will struggle with big torque!... 

Arn't you using a single L Motor for propulsion? I doubt that torque will be a problem, especially in such a small model