I am working on building an Antweight for an upcoming competition. I normally do RC planes and Cars. I have always wanted to do combat robots.

To be clear this is a 1lb Antweight.

I have several brushless motors at my disposal however I don't really have much of a budget so I would prefer to use something on hand.
Here I the two motors I have available to me.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6634

&

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14737

I want to do a horizontal spinning bar weapon.

Here is what I am planning on using for my bot so far.

I am using an old hard drive with the center milled out for the body with
acrylic top and bottom panels (or polycarb if I can find some and my laser cutter can cut it)

Banebots wheels the 1 3/8" size

Tamiya dual gearbox for the motors

I am thinking of using 2 x 10 amp botbits esc's that way when I upgrade to a beetleweight I don't have to buy new esc's (assuming they don't get destroyed in combat)

So I have 2 concerns
1. Tamiya gearbox motors are rated for 3v only. I want to run the weapon motor at 11.1v (3 cell lipo) Is it okay to put a voltage regulator in between the esc and motor or between the esc and battery. which is better?

2. Since I have never built a spinning weapon before I don't know how much current it will draw nor do I have a way to measure it.
What size battery should I use? I have very limited space. I have a 500mah 3s lipo that fits perfectly where I want the battery to go but I think this might not be enough for a 3min match...

Can you fit a separate 180mah 1S battery for the drive alongside say a 3-400mAh 3S for the weapon? Would be much better IMO. What size and material or weight is your bar going to be?

I would say 500mAh overall will be fine for 3min, I've run 750 in a beetle with a drum weapon no dramas

Welcome to the forum also
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<Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls

1S on the 10As may cause issues they are only meant to work down to 2S as they have a 5v regulator on their. They may work on 1S as I think the chips run off 3.3V but this is not something I have tested. Could you use a single 2S battery and get away with that for both. If they are the Tanya gearboxes I am thinking of those plastic setup a may not last real long.

eBay for some gearmotors might be a better option.

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com

The Tamiya Dual motor gears are pretty weak things. I remember having one of these about 10 years ago and stripped the gears pretty quickly on a toy model tank. I'd definitely look at something better.
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https://www.halfdonethings.com/

I have ~56x30x13mm of space free for the battery. I could use a 2 cell battery if I need to but Id really rather use a 3 cell.

The weapons blade will probably weigh ~60g however It depends on how much weight I have left over. If I have weight to spare it will go into the weapons.

I know the Tamiya gearbox is likely to break after a short time. I only need it to last for the competition then I can upgrade the motors when I have a little extra money. (trying to do this on a college students budget)

Tamiya stuff is total rubbish for combat robots, it'd be a big mistake to design a robot around their dual gearbox... you're much better off with these ebay gearmotors for only a little more than the tamiya set:

http://www.ebay.com.au/itm/6V-1000RPM-Torque-Gear-Box-Motor-New-/260793939183?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cb887b4ef&_uhb=1#ht_1599wt_906

http://www.ebay.com.au/itm/12V-1000RPM-Torque-Gear-Box-Electric-Motor-New-/260782707434?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cb7dc52ea&_uhb=1#ht_4362wt_906

We don't build 1lb antweights here but they seem like a nice inbetween to the antweight and beetleweight gearmotors I've used in the past.
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YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH

Welcome!

quote:

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Originally posted by Jolijar:

I am using an old hard drive with the center milled out for the body with
acrylic top and bottom panels (or polycarb if I can find some and my laser cutter can cut it)

~~ Don't use acrylic, its so so weak, and you can't cut polycarb on a co2 hobby laser unfortunately, it burns, doesn't cut proper and produces chlorine (aka kills you ) Maybe look at acetal. You can cut that but the ends get a bit melty, though i read with lots of air assist will cut accetable. Certainly good enough for robot use


So I have 2 concerns
1. Tamiya gearbox motors are rated for 3v only. I want to run the weapon motor at 11.1v (3 cell lipo) Is it okay to put a voltage regulator in between the esc and motor or between the esc and battery. which is better?

~~ Don't use those tamiya gearboxes either, can almost gaurantee they will break before it gets near an arena. Many other cheap robust and metal options about The 1000rpm gearboxes off ebay are okay, and you can transfer them up to a beetle when you need and you can run it all off 3 cells.

2. Since I have never built a spinning weapon before I don't know how much current it will draw nor do I have a way to measure it.
What size battery should I use? I have very limited space. I have a 500mah 3s lipo that fits perfectly where I want the battery to go but I think this might not be enough for a 3min match...

~~Depends depends! How big is the weapon, gearing etc. 500mah 3s lipo is what i use in my beetle, and that swings a huge blade, i reckon 350mah would do you fine in a 500g robot. Just make sure you get one with a high C number to handle the current, like 30-40c. They should be plenty cheap in that size Would certainly not expect any ant spinner to go past 20 amps peak. I think my beetle only hits 15 or so on start up.

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Okay you sold me I'll ditch the tamiya gearbox. I think I might go with the 12v 1000 rpm motors that you linked.

The only issue with this is that I'll need to move the motor location so that the tires are on the outside. This will make them more susceptible to damage. Of course this gives me way more room to mount components.

I also just scored a Aluminum plate that is 1.5mm thick
it weighs 65g although it is slightly larger than the frame so I should be able to drop it down to 55-60g

I am gonna take my HD frame to the college and mill it down tomorrow.
It weighs 200g even but I should be able to cut that in half.

I'll post some pictures up when I get the frame milled out.

Good advice there post up pics when you take them. Where are you based? I'm guessing US?
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<Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls

I am in the United States.
Illinois specifically.


What do you all think about Carbon fiber?

Is 1.0 mm thick enough to hold up?


Looking at this here.

http://www.hobbyking.com/hobbyking/store/__9781__Woven_Carbon_Fiber_Sheet_300x100_1_0MM_Thick_.html

Hmmm if its structural then probably but as your in the US its probably easier to just go Ti.

http://www.titaniumjoe.com/index.cfm/products/product-details/?code=SP:6AL-4V:11.000:18.600:0.020

about 0.5mm and significantly bigger too.

I am betting that CF would probably need a "large box" from HK so your prolly looking at $10 to post at least.

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com

Actually for once HK decides not to gouge on shipping its only $3
I would love to use Ti but that would eat almost all my budget.

I built an ant (150 grams) out of 3 mm carbon fibre. It got cut through the first time it went against a spinner. I wouldn't use it again. Now I use 0.8 mm titanium for the sides. I use 1 mm polycarbonate for the base. Spinners have hit the poly but I have never had the polycarbonate fail underneath the robot.
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So even the rain that falls isn't actually going to fill our dams and our river systems

The sides of the body will be ~2-3 mm thick and up to ~9 mm thick in some places.

The armor is for the top and bottom only. This means it only needs to protect against overhead attacks since it is unlikely The bot will be on its side.

I have 0.65 mm steel plate
and I have enough 1.5 mm aluminum plate to cover one side.

Both the Aluminum and Steel weigh ~60 g per side.
1 mm Carbon fiber would be ~ 45 g for both sides

My weight looks like this so far

Weapon motor Choice #1 (900kv) 90 g
Weapon motor Choice #2 (2050kv) 43 g

Drive Motors 60 g
ESC for Drive motors ~20 g
Battery 50 g
Wheels 22 g
Frame ~100 g
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252 g


Total weight remaining
Weapon #1 Steel armor -8 g
Weapon #1 Carbon armor 67 g
Weapon #2 Steel armor 39 g
Weapon #2 Carbon armor 114 g

This weight is needed for the weapon blade and various hardware.
The school was closed today for a snow storm so I was unable to mill the HD case.

I'll have closer guesses as I gain components and continue work on the bot.

Cool. Do you have any drawings or CAD etc?
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<Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls