Sunday, 13 January 2013

Power Functions Car, with a Differential & Self-centering Steering

I cannot believe the last post in this blog was more than a year ago...time really does fly. I wished everyone had a great Christmas last year & a great start this year. I had a rather long break during the Christmas holidays and as usual I spent some time to work on some Technic/Mindstorms models, so I built this:
This Power Functions car was built primarily based on Snow White by Jaeho Jung and Sariel's The Unofficial LEGO Technic Builder's Guide. The PF car is modular in design and it is basically divided into 3 main modules:

  • The drive module
  • The chassis
  • The steering mechanism
The drive module is the same as the one designed by Jaeho Jung, with an overall gear ratio of 1 : 3.75
1 : 2.25 ratio from motor to intermediate axle

1 : 1.66 ratio from intermediate ratio to wheel axle, giving a final ratio of around 1 : 3.75
The chassis module consists of the PF battery pack and long beams for connecting the drive module and the steering module.

The steering mechanism is a little more interesting here, one of the biggest problem with the PF medium motor + rack and pinion setup is the inability of the mechanism to return the steering to the centre after turning to the right of left. So I incorporated a self-centering mechanism found in Sariel's book to see how well it works & I was surprised by the results - it worked really really well.
Self-centering steering mechanism from Sariel's book
After playing with the model for a while I decided to see if I could include a differential to the drive module to see if the handling of the car would be different compared to a solid axle and here is how it looks like,

A drive module with differential, with an overall ratio of  1 : 2.78


The underside of the chassis
The differential did improve the cornering speed somewhat, and overall both the configuration were fun to drive around with. The power functions elements that were used in the construction are,
  • 1 power functions XL motor.
  • 1 power functions medium motor.
  • 1 power functions receiver.
  • 1 power functions battery pack.
  • 1 power functions remote control.
And for anyone who wants to improve their construction technique in LEGO Technic/Mindstorms, I would strongly recommend grabbing a copy of Sariel's The Unofficial LEGO Technic Builder's Guide.




2 comments:

Seamus Lowe said...

I know Lego's are for kids mostly, but after seeing these Lego Mindstorms and programs that help kids learn to build them, I really want some. I think they're great and really help kids use their creativity.

Blog Teknik said...

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