Raspberry Pi/Technic Project help

[johp778]

Hi All

I've been working on an rc van using a Raspberry Pi as the control and have decided to incorporate a technic motor for drive and would like to ask for some help and advice.

I want to build a simple gearbox/drive in a compact design, but wasn't sure what gearing/design to use? I have forward and reverse control through the Pi/Scratch and it maybe easier to keep it as simple and reliable as pissible, any help/advice appreciated.

You can see my project here http://raspivan.weeb.../rasppivan.html

Edited September 12, 2014 by johp778

[Balrog]

Hm ... sorry I cannot be very helpful on this topic, but I have a question:

Why do you want to use a Lego Technic motor (with case or without?) for a project that is elsewise not related to Lego (Technic) at all? Wouldn't it be better to just use standard RC motors?

[johp778]

Hi, That’s a good question, well I guess I bought a Technic set while working on my Pi project, loved it and after experimenting with robotics motors and wheels and not being completely satisfied in one way or another, when I saw some Technic wheels that I think will suit my old transit van look, it made sense to combine the two. Other people have been using Technic motors with Pi for quite a while now, so I also thought it can’t be that hard to do and using Technic also means I have a stable drive setup, hopefully any easier way of mounting to my acrylic chassis, rather than the make shift brackets I originally tried and it’s very difficult to find the right looking wheels, that work (have the right shaft diameter/fitting) for the motors I chose. I did make a small RasPiCar that uses small rc motors and works fine for what I designed.

[anton1678]

@Balrog

I want to build a simple gearbox/drive in a compact design

I think this is the reason, because a Technic gearbox is easier to make, and lego motors go with it.

How many gears do you want for your gearbox?

For a good design, maybe Sariel's gearbox page can help you out.

http://sariel.pl/tag/gearbox/

[Balrog]

Hi, That’s a good question, well I guess I bought a Technic set while working on my Pi project, loved it and after experimenting with robotics motors and wheels and not being completely satisfied in one way or another, when I saw some Technic wheels that I think will suit my old transit van look, it made sense to combine the two. Other people have been using Technic motors with Pi for quite a while now, so I also thought it can’t be that hard to do and using Technic also means I have a stable drive setup, hopefully any easier way of mounting to my acrylic chassis, rather than the make shift brackets I originally tried and it’s very difficult to find the right looking wheels, that work (have the right shaft diameter/fitting) for the motors I chose. I did make a small RasPiCar that uses small rc motors and works fine for what I designed.

Then why don't you make the whole chassis out of Technic and simply add the body that you have. Seems easier to me than trying to add PF motors to an otherwise custom chassis. That would also allow you to easily add a gearbox, steering and even suspension. And "combining" the Pi with Technic seems a lot easier to me than trying the other way.

And if that was successful, you can still try building the chassis with the acrylic base. I mean, this project is really ambitious and it's basically about the learning (I guess), but I know what could happen if you want too much at once. Better roll it up step by step.

[johp778]

@anton1678

I’m not sure, motor speed can be controlled through the Scratch program on the Pi, removing the need for gears, however it’s not something you can do without a screen and I am only connecting it to my tv when I first switch on and will then disconnect the cable to control it from the mini keyboard.

Reverse is already in my program control, so no need for a reverse gear, thinking maybe 2 or 3 forward gears?

I will have a look at Sariel’s page, I’m sure there will be some helpful info

@Balrog

Yes I see your point and it would probably be alot easier, however I didn’t have Technic when I first ordered my acrylic chassis and I’m still not sure I know enough about Technic to build a chassis from scratch, but a good idea and something I may still do, but I would still like to work with what I have, I don’t really have a lot of Technic (mainly sets I don’t want to mix), so Technic works out expensive buying all the parts, although I do have my Unimog 8110 set that I wouldn’t mind using, it’s currently built as a jeep and trailer

I should add, the gearbox will need a manual switch to change gear

[johp778]

Hi All, I built 2 gearboxes last night, a simple direct drive to diff, so I guess a 1:1 ratio and I recreated the 2 speed gearbox out of the 8110 Jeep I built (designed by MrTekneex) and both seem like possible solutions and compact enough to fit in my chassis, but the jeep gearbox I didn't have time to sort the gear switching, so that would be something I need to add. I have also found this video on youtube,

which also looks like a possible solution, as I could then add an additional motor and control the up/down gear change remotely through my scratch code and mini keyboard, however looking at the gearing, I'm not sure if the 2 speeds are different enough? I don't have any understanding of gear ratios, I can't get my head around it, but I want to try and have a high and low gear, fast and slow. It's definitely a great way of learning more about technic and the challenges many of you face building such fantastic designs, with such complex functions. Edited September 13, 2014 by johp778