We've noticed a lot of google traffic searching for parts and insights into 30lb sumo robots.
With that we decided to put out a little info to get you new builders started.
Don't forget to check out http://sparc.tools/
Not only is it full of info for new builders but a virtual meeting place for a majority of combat robot builders the world over!
Don't forget to check out http://sparc.tools/
Not only is it full of info for new builders but a virtual meeting place for a majority of combat robot builders the world over!
You need a minimum of 4 parts for any robot.
Ravi Baboolal of All Black Robotics talks about the 4 components needed for a 30lb robot.
1: Motors
2: Batteries
3: Control system
4: Motor controllers
- Motors -
Realistically the aspiring builder has two options when selecting drive motors for a robot.
A) scavenge / repurpose
B) purchase new
Which ever way you go it's good to keep in mind that you will likely need a gearbox or gearing system. A gear system utilizes gears, pulleys or chains to reduce the output of a raw motor into something more useful. For instance, the E-scooter motors I use on my 150lb robot Roach have an output of 2750 RPM (revolutions per minute) had I attached a wheel to that motor the robot would have had little pushing power but moved at 30mph...much too fast to be of use.
Instead I used a series of timing pulleys and chains to reduce the motor output to something useful (1000 RPM) all while gaining much needed torque for pushing other bots around.
For an in-depth look at how gearing works check out;
Scavenging
Scavenging motors is an affordable way to go, though this doesn't mean digging through piles of trash looking for the perfect motor (most of the time). But rather repurposing readily available options such as cordless drill motors, E-scooter motors or car window/fan motors.
Cordless drill motors can be a great option, they are built to be powerful, lightweight and perfectly suited to run off DC power (battery packs). The drill motor itself comes with a gearbox which amplifies the motors raw power into something more useful. The trick to working with these is they can be difficult to mount to a robot frame and have a threaded output shaft. However these issues are not insurmountable. There are a number of ready to use wheels and hubs which mount directly to a drill, otherwise you can mount your wheels to the motor with nothing more then a drill and the right thread cutting tap.
For details on dissembling a drill check;
Purchasing
If you'd rather buy a purpose built gear motor there are now many options built specifically for fighting robots. Check out the following websites;
Quick recommendations for the 30lb class; check out the Banebots gear motor and wheel combo
- Batteries -
We could take an entire week to go through battery details. But I'm going to make this quick and easy. First thing you must do is select a voltage, this usually depends on the motors you're using. So lets say you've settled on 12v drill motors motors. Now we need a 12v battery with enough capacity for our robot.
Here is a nice little tool for determining how much capacity you need, capacity is measured in Ah or Mah (Amp Hours / Miliamp Hours)
Lets say, 2x 12v harbour freight drill motors with 3" wheels
This is a fairly common set-up.
The calculator will spit out a number, in this case 0.11Ah to run for 3 minutes. Meaning we need a battery with at least 0.1Ah or 1000Mah capacity. For this I may select a 12v 5amp sealed lead acid battery.
Like this;
At 6Ah we should be able to run for a lot longer then 3minutes too!
You have a number of options when it comes to batteries. Generally select the battery with the highest capacity you can afford so long as it will fit in the robot.
Here would be a few other options:
Two of these (wires are a bit small) http://hobbyking.com/hobbyking/store/__51193__Turnigy_Receiver_Pack_Sub_C_4200mAh_6_0v_NiMH_High_Power_Series.html
or one of these
Battery Chemistries;
NiMH
NiCad
Li-Poly
LiFePo4
SLA
For reference I used 2x 24v Nicad battery packs to run my 150lb robot Roach. The battery packs were run in parallel equating to 7.2Ah which gives me 10-15minutes of run time.
Which ever you select please research the battery, how it needs to be charged and the equipment required to do that. Most batteries require special charging equipment.
Here is a little intro video for RC batteries;
Next week we'll cover Control Systems and Motor Controllers.
If you have design or component selection questions do not hesitate to reach out via Facebook, email or twitter!
Until next time.
-Ravi B
All Black Robotics
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