Hi,

I want to build a long range terrain robot, not a huge one, maybe 30 cm x 30 cm or 40 cm x 30 cm.

I haven't built the chassis, but I'm planning to use metal chassis whether aluminum or steel sheets.

My concern now is that what type of motors and battery I should buy ?

1. Should I get 12V or 24V motors ?
2. Based on motors voltage rating, what type of battery I should buy ?

 

There are too many variables to consider before we can start specifying motors.

What is the total weight of the robot?
How will the robot be powered?
What is the maximum speed required?
How far will the robot travel and for how long?
What precision is required?
How will the robot steer?
How many wheels on the robot? How large are the wheels? What kind of wheels?
What kind of terrain will the robot traverse?
etc... etc...

 

What is ‘long range’ and how heavy is it. and are you planning on solar charging.

 

Have you decided on & sized servo motors yet?
This will be a deciding factor on voltage.

 

This is like me asking you what size engine and gas tank I need to get if I want a long-range vehicle. Could you answer something like that? I sure couldn't. Without even considering numerous other issues, I would get expect very different answers if it turned out that I wanted the vehicle to do 120 mph for 1200 miles versus wanting it to go at 30 mph for 600 miles.

 

Electric wheel chairs can sometimes be found at thrift stores pretty cheaply. I know several people who have converted them into robots. This might be a good starting point for the propulsion system.

 

What is the total weight of the robot?

I have no experience with weighting rc robots, considering the weight of the metal chassis + motors + battery + electronics.

But let say max 3 - 4 kgs .. if my assumption is logical.

How will the robot be powered?

Using a big capacity battery, but I'm not sure what to use.

Didn't know that batteries are really expensive.

Good quality Li-ion packs; like, Molicel would cost me a lot

Also, I'm thinking about li-fe but don't know which type to choose because the ones I get in search results are really expensive like $1400.

What is the maximum speed required?

Not very important, any speed but not too slow, because I'm doing it for exploration and testing long range electronics.

If I'm sending it to a far location it should be a reasonable speed where not to draw the battery so fast and not too slow so I wait a lot of time until it reaches the target location.

How far will the robot travel and for how long?

I'm thinking to start within 1km not more than that.

What precision is required?

Precision in in movement or in communication or locating it in GPS ? I don't know what you mean.

But anyway in electronics part, it should work ok.

How will the robot steer?

I would use skid steering like the tank.

How many wheels on the robot? How large are the wheels? What kind of wheels?

I think 4 is ok.

What kind of terrain will the robot traverse?

Not planning for wet situations, but I want to include that property in robot design that it can handle wet areas.

Also, other terrains; like, street and sand. That's pretty much what I have in the region I live in.

 

What is ‘long range’ and how heavy is it.

Long range means, using a relatively big battery and long range transmitter/receiver electronics.

Basically a range within 1km is my first goal, then I might study if I'm interested in longer distance.

and are you planning on solar charging.

Didn't thought of that actually, but I won't mind it if I needed this technology.

 

Have you decided on & sized servo motors yet?

I'm planning using DC motors in skid configuration.

This will be a deciding factor on voltage.

I'm now in the decision between 12V or 24V motors.

There are information saying 24V use less current so I'm not sure if either 12V or 24V is better.

 

This is like me asking you what size engine and gas tank I need to get if I want a long-range vehicle.

I should've put a picture of the model of terrain robots I want to design.

 

Electric wheel chairs can sometimes be found at thrift stores pretty cheaply. I know several people who have converted them into robots. This might be a good starting point for the propulsion system.

That would be difficult in the area I live in. Scattered spare parts stores.

I think I have to buy it online.

 

24v is a better choice. Less amps on wires means less wasted battery energy.
If you could find 48v motors and controls, you could series two 24v batts.

Batt chemistry choice depends on environmentals. LiIon are no good in very cold, as example.

 

I should've put a picture of the model of terrain robots I want to design.

The two lengths of aluminium profile on the top are typically 40mm square so this is quite a big beast! Do you have actual dimensions and have you selected suitable wheels/tyres? That's where I'd start, but I'm just an engineer....

 

Opening post states 30x30 or 40x30 cm.
Those extrusions appear to be 20x20 mm.