Battery power question

[BDBlu]

My father and I are planning on building an antweight for fighting purposes.  The idea is 2 wheels with drummer.  We plan everything except one thing... we have little to no experience with electronic setup.  How much power do we need to transfer from the battery to the motor? Does it take away the total amount?  For example, 3V motor connected 7.4V battery.  Does it take away 3v and leave it at 4.4V for anything else?

[R1885]

Uh, no. Not at all. Everything gets 7.4V.
Also, why are you using 7.4 volts? Unless you have a serious weight problem, you don't need to hamper your self. Go with 11.1 volts.

[BDBlu]

Just an example.  I basically need to restrict the battery's output to the required motor's input?

[cephalopod]

You can overvolt some components safely, but some stuff needs pretty much exact voltage (see: many receivers blowing if they receive anything above 5v). Motors aren't so precise with requirements. I'll be running 12v motors at 15v in my new beetle.

[BDBlu]

Really?  I know some people burned out their motors by using too much voltage, so I was being cautious.  Do you have any reference for antweight circuit board?

[Somebody]

The easiest way to fix or build something is to understand it.

https://www.khanacademy.org/science/physics/circuits-topic

It will absolutely be worth learning, and will save you money and time. This is more of a general overview on circuits and not related to batteries much at all. But knowing how voltage, current, and resistances work will be crucial for you to pick the right batteries for your robot, and help you make logical decisions when wiring.

Really?  I know some people burned out their motors by using too much voltage, so I was being cautious.  What would be a safe estimate before you overvolt?

A lot of this depends on the equipment itself. I've heard as high as doubling the voltage, but I wouldn't recommend it on just any motor. More commonly I read about people giving about one and a half times the recommended voltage, which may still be pushing it as far as I know.

[R1885]

No, a motor can take more voltage than its nominal. Overvolting will increase both speed and power(as well as amp draw), but is harder on the motor. Some motors can take a lot more voltage than it supposed too, and some fry if you attempt it. In general, brushed motors can take overvolting, some can take as much as four times as much voltage as there supposed to, but brushless motors typically can't take more voltage than specified, and most are optimized for what voltage their set for anyway.

An idea of what motors your planing on using would be nice.

[BDBlu]

The easiest way to fix or build something is to understand it.

https://www.khanacademy.org/science/physics/circuits-topic

It will absolutely be worth learning, and will save you money and time. This is more of a general overview on circuits and not related to batteries much at all. But knowing how voltage, current, and resistances work will be crucial for you to pick the right batteries for your robot, and help you make logical decisions when wiring.

I really appreciate this!  I learn all more of these within a hour than a full year in high school.

An idea of what motors your planing on using would be nice.

We are still deciding on the drive motors.  We know geared motors are best for it, so we're scanning through robotmarketplace.com.  We need 2 geared motors and 1 non-geared for drum spinner.  We have a tight budget for this and it is something we want to do for fun, and possibly competitive if there are enough events.

Any recommendation?

[R1885]

We are still deciding on the drive motors.  We know geared motors are best for it, so we're scanning through robotmarketplace.com.  We need 2 geared motors and 1 non-geared for drum spinner.  We have a tight budget for this and it is something we want to do for fun, and possibly competitive if there are enough events.

Any recommendation?

A good place to start is to look at the top ant drums right now: The Bomb, Saifu, and Klazo.
All of them have an inbuilt brushless out-runner outrunner  motor incorporated into the drum, Saifu and Klazo use a form of the Turnigy SK3 motor, while the Bomb uses a type of AXI Gold series motor.
Be warned though, a drum needs a lot of machining to get right, anything wrong can send the whole system out of whack, start with a bar from an weed-whacker edger,

As for drive, there's really no general consensus. I'm in the camp that prefers the Fingertech Spark motors, others like the small generic gearmotors that look a bit like this(There are dozens of motors like this one, with wildly differing stats, look around and you'll find one you'll like), while some take their chances with ebay and go for a motor more like this(AKA Silver Sporks, again with wildly varying stats). Whats good for one bot may be crap for another, experiment and see what works for you.

Also, has anyone mentioned that spinners are extremely dangerous? Even an ant spinner can slice your skin straight down to the bone, and then some. Use extreme caution, or you'll be visiting the emergency room.

[Somebody]

The easiest way to fix or build something is to understand it.

https://www.khanacademy.org/science/physics/circuits-topic

It will absolutely be worth learning, and will save you money and time. This is more of a general overview on circuits and not related to batteries much at all. But knowing how voltage, current, and resistances work will be crucial for you to pick the right batteries for your robot, and help you make logical decisions when wiring.

I really appreciate this!  I learn all more of these within a hour than a full year in high school.

An idea of what motors your planing on using would be nice.

We are still deciding on the drive motors.  We know geared motors are best for it, so we're scanning through robotmarketplace.com.  We need 2 geared motors and 1 non-geared for drum spinner.  We have a tight budget for this and it is something we want to do for fun, and possibly competitive if there are enough events.

Any recommendation?

Absolutely happy to help! Welcome to the wonderful world of engineering. To back up what R1885 said, never forget safety, it is truly crucial. Don't spin up a weapon anywhere near you for the first few times or hits.

[BDBlu]

A good place to start is to look at the top ant drums right now: The Bomb, Saifu, and Klazo.
All of them have an inbuilt brushless out-runner outrunner  motor incorporated into the drum, Saifu and Klazo use a form of the Turnigy SK3 motor, while the Bomb uses a type of AXI Gold series motor.
Be warned though, a drum needs a lot of machining to get right, anything wrong can send the whole system out of whack, start with a bar from an weed-whacker edger,

We are thinking about ordering Saifu's chassis and fabricate the drum.  The Turnigy motor certainly beat out the motor we came across at a hobby store.  The thing is a bit too big and my dad suggested building a drive chain (which is a dumb idea since I don't have the tools) so we'll keep that as a back up just in case if we can't find another motor.

Also, has anyone mentioned that spinners are extremely dangerous? Even an ant spinner can slice your skin straight down to the bone, and then some. Use extreme caution, or you'll be visiting the emergency room.

This is the first thing we discussed while planning the bot.  We are aware of the danger and I have enough room in my garage to build a safety cage if I want to test against harder targets.  We are taking each steps as cautious as we need.

Absolutely happy to help! Welcome to the wonderful world of engineering. To back up what R1885 said, never forget safety, it is truly crucial. Don't spin up a weapon anywhere near you for the first few times or hits.

I didn't realize how fun building a bot is. Haha.

[R1885]

We are thinking about ordering Saifu's chassis and fabricate the drum.  The Turnigy motor certainly beat out the motor we came across at a hobby store.  The thing is a bit too big and my dad suggested building a drive chain (which is a dumb idea since I don't have the tools) so we'll keep that as a back up just in case if we can't find another motor.

You don't need a drive chain, the gear box is already doing the work.
If you are going to fabricate a custom drum, but don't have the ability to machine it, draw up the sketches in a CAD program such as E-Machine Shop and have a a big shop such as Big Blue Saw or Team Whyachi Bot Shop make it for you. More expensive, but they're likely to have superior equipment than what you have at home. Also, if you're going for the Saifu chassis, remember that it was designed for an all in one drum with motor built into it, so you will either have to make your own all in one drum, or you will have to modify the chassis to accept a stand alone motor.

[BDBlu]

You don't need a drive chain, the gear box is already doing the work.
If you are going to fabricate a custom drum, but don't have the ability to machine it, draw up the sketches in a CAD program such as E-Machine Shop and have a a big shop such as Big Blue Saw or Team Whyachi Bot Shop make it for you. More expensive, but they're likely to have superior equipment than what you have at home. Also, if you're going for the Saifu chassis, remember that it was designed for an all in one drum with motor built into it, so you will either have to make your own all in one drum, or you will have to modify the chassis to accept a stand alone motor.

I meant the drive chain for the drum motor that we found at a store, not the drive motor.  My apology for not clarifying.  Thanks for linking those 2 links, but they are a bit out of the price range.  We can come up with something.

[R1885]

I meant the drive chain for the drum motor that we found at a store, not the drive motor.  My apology for not clarifying.  Thanks for linking those 2 links, but they are a bit out of the price range.  We can come up with something.

Ah, that makes a little more sense.
The preferred way to getting weapon reduction is the use of timing belts/pulleys. These will help reduce unneeded weapon speed, isolate impacts away from the weapon motor, and reduce spin up time.
You really should consider getting the drum professionally made, anything wrong will cause your bot to shake around like a washing machine with a brick inside of it. You might want to consider an egg-beater weapon(Like on Gyroscopic or Weta), it would be much cheaper to make, easier to balance, and is almost as good as a drum.