Friday, November 15, 2013

Little Red Box



Datasheet:
Dimensions: length/width/height IN - 6.3/6.3/4.75.  CM - 14.4/14.4/9.4
Weight: 0.5 lb
Power: Power Functions rechargeable battery
Propulsion: 1x PF M motor
Steering: PF servo motor
Built: Early May 2013 


The goal with this MOC was to make an ultra-compact, drivable and steerable  vehicle base, with a brick built housing. I thought it would be funny to see a little red brick cube start driving around :). After just an hour or so of building, I had a functional design. And after some improvements, it looked like this:

The steering motor was attached to a connector plate, (left) which was mounted on a stud jumper (right). This way the motor was as close up against the battery as possible, although it was still a bit off center with the rest of the base.
                                                              

Since both the Servo motor and the steering mechanism have to be at perfect right angles in their neutral position, the wheels don't return to center perfectly.
I decided to use the servo motor anyway, as the return to center function is still convenient. And I can use the speed remote control for proportional control, which can remedy the problem of the wheels being off-center.




For the propulsion, I again created the simplest solution I could, with an M-motor directly over the wheels. (Note. The image above and the final version are slightly different, as can be seen in the video.)

I decided to attach the cover by having a mostly flat plate over most of the model.
Most of the base came out as a rather irregular shape, and there's a good bit of empty space with the cover on. So no doubt a smaller RC cube can be made.



Additional photos:








Figures are to scale.


Video: Lego Motorized Red Box - Youtube  (Looks much better in HD.)

Wednesday, April 24, 2013

Race Buggy



A simple model, built to test out the RC unit.


Datasheet:
Propulsion: 1xRC motor powered by the RC unit
Steering: RC unit steering output (return-to-center)
Suspension: Front/Rear  Double-wishbone (independent)/Dragged axle

After managing to buy an RC unit and handset, i quickly designed this model to test it out.
The rear frame was mounted on the units hinges, and used technic hubs (part x873c01) to secure the wheels better. 
The front was made with a standard independent suspension, connected directly to the front of the unit and it's steering output, and i added lights and a "LEGO Technic"  sticker, to give it more aesthetic detail.
 The RC unit i got didn't have it's battery cover, so i used a rubber band for securing the batteries instead, it didn't always keep them all the way in, but at least now they never fall all the way out.

The RC unit gives more power than i expected, and apear's not to have a thermal safety system like on the Power Functions system, which would limit the power given to the motors once it exceeds a given point. Thus, unlike on my previous RC car, which was driven by an RC motor, but powered by Power Functions, i could drive it aggressively, without the power being limited, or shut off. This, combined with the amazing range it has, due to it being controlled by radio signals, not infrared signals, makes it a lot more fun to drive.

The turning circle was quite wide, (mostly because the RC unit's steering output only turns 45 deg.) but when going fast enough, the car could sometimes skid, and turn a lot tighter, especially on wood floors, and was sometimes hard to control.

 Video showing the model's performance:  





(Not: One or more of the rear wheels fall off several times in the video. I've have since fixed this, and you can see the structure that's hold them together in the photos).

And some photos:

  


Monday, February 18, 2013

Street Racer

A small, extremely fast RC car. It doesn't have any off-road capabilities, so it's not quite a buggy, but it's not quite slick enough to be a race car either,  and so I've called it a "street racer"

(Update: i've improved the styling a little bit by making the entire hood red, and adding a few more bricks around the receiver  So the model doesn't look quite the same in the video.)

Datasheet:

Propulsion: 1x RC motor
Steering: 1x PF M motor
Suspension: rear independent
Drivetrain: direct drive
Dimensions: 41 studs long, 31 wide, and 16 high
Weight: 2 lb (.9 kg)

I love making fast RC cars, and now and then i try to make a faster one. I usually end up just building a simple chassis like the one below, which has some basic functions, and almost no bodywork. 

 After driving my most recent RC chassis (which i built with direct drive and return-to-center steering) around for a while, i decided to build it more interestingly, i gave it a custom independent rear suspension, which has the added benefit of raising the ground clearance while still keeping the direct drive. 

I then covered the chassis with a combination studfull and studless (system and technic) pieces, and added some other details like the mudguards, spoiler, lights, and exhaust pipes. I wanted to cover up the battery box too, but i couldn't find a simple way to do this.
I also put covers on the wheels because they are not all the same color.
The added weight of the bodywork decreases the acceleration and speed some, but not much.


The steering system is a pretty basic rack-and-pinion with a return-to-center system.
The steering motor drives the pinion directly then goes straight to the RTCS which is a simple design by Sheepo. The rack is made from three liftarms, allowing center one to move side to side, without also moving inward.
(As the steering arms turn to the side, they also move slightly inwards, with the sides of the rack able to pivot, they can absorb the turning and the center section can stay in place.

 The the small steering lock and lack of differential degrade the steering, but make it easy to maneuver when driving fast, and direct drive helps it achieve almost maximum efficiency. 
All in all, i think the model turned out well, and i learned a lot about make videos  while making the one for this model.




Photos: