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New builder in Canberra


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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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New builder in Canberra

Hi,

I'm from Canberra and found out about the upcoming competition in Canberra in August.

I grew up watching the old TV shows but always thought it must be expensive to build them.

However I was in Sydney this weekend with family and we watched the competition at Vivid, and after talking to the builders there I realized that it doesn't seem that expensive to make a robot.

I have an engineering and electronics background and I would think it would be fun to make a robot for the Canberra competition.

One of the builders explained an easy way to start is with a Hobby King RC controller and a bunch of Kmart drills.

I am thinking about building a hammer or puncher type robot using a big spring with a high torque motor and ratchet with a quick release to power the weapon.

(Shoutout to Erica from The Creative Element who gave me her business card and told me about the Canberra competition)

Post Mon Jun 06, 2016 8:39 pm 
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seanet1310



Joined: 08 Nov 2006
Posts: 1265
Location: Adelaide


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Hey Leithal_weapon,

Welcome to the forum.

It does not cost a lot to get started, some people can do it very cheap like miles&Jules who often procure old drills with dead batteries from tip shops and the like. Hobbyking is good for remotes and batteries. Electronic Speed Controllers are a lot cheaper than they once were. Botbitz I think is still revamping but they are the cheapest source of decent and proportional ESC. If you need a few for a more complex design this price can build up.

The electronic and engineering background should come in handy.

Regarding the weapon, the only local design I can think of that is slightly similar was from miles&Jules. It was a garage spring flipper. tensioned via a winch gearbox with brusless motor (high torque setup). Had a decent little kick to it although in the build thread there are only early trials of the mechanism. They used a cam though to tension and trigger rather than ratchet and release.

http://www.robowars.org/forum/viewtopic.php?t=1559&postdays=0&postorder=asc&start=1155
P

If you are trying a complex weapon or a lot of interaction such as the one proposed I would try to start the design and testing of the weapon soon, even if it is on a wooden platform for starters.
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Post Mon Jun 06, 2016 8:53 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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What parts from hobbyking should I get?

Im using 18V kmart drills for the wheels, not sure what other motors/servos/actuators i might end up using for weapon stuff.

I had a quick look at local model shop but their stuff super expensive.

Also what sort of drive system do you guys use? 4 wheel drive with 4 controller, or just 2 controller, or even just 2 wheel drive?

Post Wed Jun 08, 2016 3:57 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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I'm still new but from what I saw on the night, every combo you just listed is used Smile

2WD is probably the most popular, after the bits of trouble I had with my 2WD setup I'm thinking of converting to 4WD if that helps.

The important stuff I've ordered from hobbyking is batteries and and the transmitter/receiver.

Previously they didn't have any suitable speed controllers - you need a brushed ESC with full power forward and reverse (most car brushed ESC's only do like 1/5 power in reverse) but there are some new rockcrawler ESC's that do 1/2 power in reverse which would be ok:

http://www.hobbyking.com/hobbyking/store/__81504__Hobbywing_Quicrun_60A_2S_3S_Waterproof_Brushed_ESC_for_1_10_AU_Warehouse_.html

But they only take 3 cell LiPo batteries (11ishV) for an 18V system you'd be looking at a 5 cell. And they are never in stock :S

Best bet is to wait for Botbitz to start selling ESC's again and get their speed controllers. The high current one can run two motors at once so you'd only need two to run a 4WD.

Post Wed Jun 08, 2016 8:12 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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I'm curious what goes into these ESCs?

I wonder why it is so difficult/expensive to get them.

At uni we built a PWM motor controller for a very high current DC motor and it was just using off the shelf electronic components.

Post Wed Jun 08, 2016 8:59 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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So is this the right controller to get: http://www.hobbyking.com/hobbyking/store/__9041__Hobby_King_2_4Ghz_6Ch_Tx_Rx_V2_Mode_1_.html

EDIT:
Also do I need mode 1 or 2? Mode 1 is out of stock. but mode 2 isn't.

Post Wed Jun 08, 2016 9:10 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Also do I need this out of stock USB cable: http://www.hobbyking.com/hobbyking/store/__9043__Hobby_King_2_4Ghz_6Ch_Tx_USB_Cable.html

Post Wed Jun 08, 2016 9:13 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Finally, what capacity battery would I want? 4WD, with fifth motor for the weapon?

What size does everyone normally use?

Post Wed Jun 08, 2016 9:20 pm 
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evil_steve



Joined: 06 Sep 2015
Posts: 296
Location: Adelaide, SA


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That's the right controller. With the standard for robots mixing set up Mode 1 (which is in stock in the Australian warehouse) would have the steering (sprung on both axis) on the left stick and the weapon control (ratcheted on one axis) on the right stick, and Mode 2 is the opposite. It's pretty easy to take them apart and swap that though.

The USB cable is needed to program the mixing onto the controller. You can get away without it by using a v-tail mixer . I'd recommend getting one, but with a mixer (or a borrowed cable) it's not needed immediately.

Battery wise, 2-3000mAh seems standard for featherweights but I'm new enough myself that that's based on limited experience.

ESC wise, from what I gather the BotBitz ones are decent quality brushless ones that have been reprogrammed to run brushed motors in a manner suitable for robot combat. I started off using 85A Botbitz ESCs running two drill motors each (for 4WD) but managed to fry one of them and ended up using 30A ones running one motor each for 2WD. I've not yet come across anyone running 4WD with 4 ESCs but given how mine failed on the weekend I'm curious if it would work.

Post Wed Jun 08, 2016 10:32 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Here is what I have chosen (not yet ordered):
http://www.hobbyking.com/hobbyking/store/__16255__Hobby_King_2_4Ghz_6Ch_Tx_Rx_V2_Mode_1_AUS_Warehouse_.html
http://www.hobbyking.com/hobbyking/store/__46730__TURNIGY_Ultra_Small_V_Tail_Mixer_AU_Warehouse_.html
http://www.hobbyking.com/hobbyking/store/__18564__Turnigy_3000mAh_5S_30C_Lipo_Pack_AU_Warehouse_.html
http://www.hobbyking.com/hobbyking/store/__77245__Turnigy_B6_PRO_50W_6A_Balance_Charger_Red_AU_Warehouse_.html

Can someone double check this is suitable for use 2WD 18V kmart drill drive?

(I think I will go with 2WD for the moment as it seems the bit botz 30A drivers would be OK for this? Not sure if I can afford the 85A ones just yet)

Post Wed Jun 08, 2016 11:18 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Finally, what is the time frame for bot bitz coming back for new orders?

Otherwise from what I gather I can just reprogram the same ESC from hobbyking using the open source code and the special cable: http://www.hobbyking.com/hobbyking/store/__44789__Atmel_Atmega_Socket_Firmware_Flashing_Tool_AU_Warehouse_.html

(which is a pretty cool cable just from an electronic engineer's perspective)

Post Wed Jun 08, 2016 11:58 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Talked to Steve, sounds like new ESCs will available in a month, or I can grab some of the current bot bitz ESC in US. I will use these ones in the final design.

In the meantime I ordered these cheap 12V brushed ESCs - http://www.ebay.com.au/itm/New-320A-7-2V-16V-Brushed-ESC-Speed-Controller-for-RC-Car-Truck-Boat-AU-/162059195559?hash=item25bb7b14a7:g:UeoAAOSwKfVXKa3i

Should be enough for prototyping, will need to drop to 4S cell for the moment, but maybe that isn't much of a problem since winch motors are 12V anyway.

Post Thu Jun 09, 2016 2:41 pm 
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seanet1310



Joined: 08 Nov 2006
Posts: 1265
Location: Adelaide


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The brushed HK ESC don't like over voltage so don't be tempted. Other than that in my experience they are quite decent but wouldn't hold up in combat due to the high stall currents. Good enough for getting a bot moving and tested as you would not be in stall pushing matches etc.

The ebay ones look similar
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Remember to trust me, I am an Engineer.

http://www.youtube.com/watch?v=rp8hvyjZWHs

Post Thu Jun 09, 2016 6:27 pm 
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leithal_weapon



Joined: 06 Jun 2016
Posts: 35
Location: Canberra


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Yeah I don't plan to use them in combat, and I got a few extra incase they smoke...

Post Thu Jun 09, 2016 7:42 pm 
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