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Offline reSpawnTopic starter

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RC Car
« on: May 23, 2007, 09:29:17 AM »
The vacantion is here soon, and I'm trying to learn electronics because I want to build a robot, that is a RC Car, like you see in "Robot Wars" but without weapons.
First, I want to make the chasis, for which I thought aluminium is a good candidate. The car should have 4 wheels, and the steering to be easier for me( I think ) I want to make it tank-like, not using a servo. The thing is I don't have an ideea how the motors(1 motor for each 2 back wheels) will be connected to the wheels, because they also need to be geared down for torque(right?).
If you guys can help me with some ideas, links or some howto of similar robots it would be great.

Last but not least I'm sorry for my poor english ( english is my foreign language)

Thanks in advance.

Later edit:
Also, can someone tell me a very used and easy to learn(not a must) CAD ? I want to design them on computer first. (I hope it won't be that hard to learn it ...)
« Last Edit: May 23, 2007, 10:35:32 AM by reSpawn »

Offline sotu

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Re: RC Car
« Reply #1 on: May 23, 2007, 11:54:16 AM »
Google: google sketchup, it's a very easy 3D building program where you can design your own robot or whatever u want for that sake easely. And the greates thing: iTS FREE! ;D its soo easy 2..
And for the motor problem. If you have 2 wheels 1 turn forward and 1 turn backward. If you have 4 wheels 2 move forward and 2 moves backward,  im not really sure off how to connect the electricion. Im still working on that myself.

Tips: Order a robot kit. From example www.pololu.com They show u step by step how to fix up the entire robot. Im going to order one of those myself!
How to build a biped bot:

Offline reSpawnTopic starter

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Re: RC Car
« Reply #2 on: May 23, 2007, 12:04:49 PM »
well, I was not talking about how to wire the motors electrically, but how to connect them with the wheels and on chasis.

Offline Admin

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Re: RC Car
« Reply #3 on: May 23, 2007, 02:01:36 PM »
Sounds like an RC tank (includes closeups of drive train):
http://www.rctankcombat.com/press/RobotFest2007/

[youtube=425,350]C6M4peQCxuY[/youtube]

Offline reSpawnTopic starter

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Re: RC Car
« Reply #4 on: May 23, 2007, 02:30:34 PM »
no, I just want the steering to be tank like: to turn left you accelerate the right motor and brake the left one.

Offline ed1380

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Re: RC Car
« Reply #5 on: May 23, 2007, 02:37:41 PM »
he means diferential drive
Problems making the $50 robot circuit board?
click here. http://www.societyofrobots.com/robotforum/index.php?topic=3292.msg25198#msg25198

Offline Admin

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Re: RC Car
« Reply #6 on: May 23, 2007, 02:47:19 PM »
Quote
he means diferential drive

ooooohhhhhhh, I thought he wanted treads . . . although its the same exact design in terms of electronics and motors . . .

well in that case:
http://www.societyofrobots.com/mechanics_chassisconstruction.shtml
http://www.societyofrobots.com/programming_differentialdrive.shtml
http://www.societyofrobots.com/remote_control_robot.shtml

this is RC and differential drive:
http://www.societyofrobots.com/robot_asme.shtml

Offline sotu

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Re: RC Car
« Reply #7 on: May 24, 2007, 06:11:56 AM »
Ok if the whole through the wheels are to tight for the motor's rotating stick i gess you could try to extend the whole or something. If its to big, i dont really know. But if its just a little to big you could try glue it thats what i did. And the attach the motor to the chassie you should try a metal band with holes in. The holes are so you can attach it to something with screws. And you can also shape the band a little. So you can attach it hard over the motor with a little band on each side where you screw it to the chassie. Thats what i did on my first robot: http://www.tunliweb.no/1st_bilder.htm
Look at the metal band going over the motor!
How to build a biped bot:

Offline reSpawnTopic starter

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Re: RC Car
« Reply #8 on: May 24, 2007, 09:33:04 AM »
and what about a CAD? I thought there were CADs that already have things like motors of different sizes, and other pieces a robot builder might use instead of drawing it on its own.
Also about the chasis constructions, in the robot you made, you connected directly the DC motors to the wheel, I am looking for a cheap gearbox to gear it down for torque. Also what about the other 2 wheels I will have, and they won't be connected to any motor, how do I attach them to the chassis?
Sorry for my newbness.
BTW Cool site & forum you have here :)
Later edit: I just unmounted a RC Car I have laying around here, and I understand now how the wheels are attached to the chasis. now I need only a good CAD's name.
« Last Edit: May 24, 2007, 09:44:20 AM by reSpawn »

Offline ed1380

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Re: RC Car
« Reply #9 on: May 24, 2007, 02:29:00 PM »
google sketchup-free
solidworks-if you have to ask you can't afford it (many many thousands of dollars). you could get student edition though. much cheaper.
Problems making the $50 robot circuit board?
click here. http://www.societyofrobots.com/robotforum/index.php?topic=3292.msg25198#msg25198

Offline reSpawnTopic starter

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Re: RC Car
« Reply #10 on: May 27, 2007, 11:49:26 AM »
google sketchup-free
solidworks-if you have to ask you can't afford it (many many thousands of dollars). you could get student edition though. much cheaper.
Does SolidWorks have premade parts like a motor, diode ... and stuff like that?

Offline Eco19R

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Re: RC Car
« Reply #11 on: May 27, 2007, 12:04:20 PM »
google sketchup-free
solidworks-if you have to ask you can't afford it (many many thousands of dollars). you could get student edition though. much cheaper.

Does SolidWorks have premade parts like a motor, diode ... and stuff like that?


Solid Works = CAD software, If you want to "design" circuits you use schematic layout software,

http://www.expresspcb.com/ <--- Free electronic schematic capture software + simple PCB design software
« Last Edit: May 27, 2007, 12:05:46 PM by Eco19R »

Offline reSpawnTopic starter

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Re: RC Car
« Reply #12 on: May 27, 2007, 12:47:16 PM »
I know what SolidWorks is, I don't want to design circuits, but to see how componenets come together.
So, does SolidWorks have premade parts like motors?

Offline ed1380

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Re: RC Car
« Reply #13 on: May 27, 2007, 03:25:30 PM »
google sketchup-free
solidworks-if you have to ask you can't afford it (many many thousands of dollars). you could get student edition though. much cheaper.
Does SolidWorks have premade parts like a motor, diode ... and stuff like that?
Yeah, but you ahve to sign up for it
Problems making the $50 robot circuit board?
click here. http://www.societyofrobots.com/robotforum/index.php?topic=3292.msg25198#msg25198

Offline reSpawnTopic starter

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Re: RC Car
« Reply #14 on: June 04, 2007, 07:58:22 AM »
Hi. :) I'm back with a CAD of the robot I want to make and of course, I need help :P
Can someone tell me what dimensions I should use for both red and green line?
The chassis(that brown thing) is set at 30 cm / 20 cm. The chasis should be big enough for later upgrade with sensors and other parts, also I haven't represented the MCU and batteries..
« Last Edit: June 04, 2007, 08:00:46 AM by reSpawn »

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Re: RC Car
« Reply #15 on: June 04, 2007, 08:14:23 AM »
Hmmm the larger the red_line/green_line ratio, the faster and more efficient your robot will turn.

The smaller the red_line/green_line ratio, the less likely your robot will flip over during start/stop motions.

In terms of cost and weight, you want both as small as possible.

So in the end, you must CAD all your parts and see what size you need for everything to fit where you want them, as well as taking in to account vehicle motion dynamics  ;D

You can also consider building your robot in multiple layers, where the bottom layer just houses motors and batteries, and the second layer can be changed as you upgrade to new components.

Offline reSpawnTopic starter

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Re: RC Car
« Reply #16 on: June 04, 2007, 08:29:59 AM »
the parts I made are in real size. As for weight... I couldn't find where to set it in SolidWorks, I will experiment more.
Can you give me some examples of ratios? for instance 2:1 will it turn fast? slow?

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Re: RC Car
« Reply #17 on: June 04, 2007, 08:32:27 AM »
well there are only two ways to know:
calculate it
build and then experiment

but if you cant do either, just do a 1:1 ratio ;D

Offline reSpawnTopic starter

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Re: RC Car
« Reply #18 on: June 04, 2007, 08:38:21 AM »
so in conclusion, the bigger red_line/green_line ratio the better right?

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Re: RC Car
« Reply #19 on: June 04, 2007, 08:42:45 AM »
wrong :P . . . there are always design tradeoffs . . . it really depends on what you want the robot to do . . .

i recommend adding all your parts to the CAD, and then try and shrink the robot until it cant anymore.

sensor placement also affects robot shape.

 


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