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Dreamcrusher/The Undertaker - OYES Robotics - NZ
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Jackbk



Joined: 07 Aug 2013
Posts: 22
Location: New Zealand


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Dreamcrusher/The Undertaker - OYES Robotics - NZ

Hi everyone, with nationals upcoming we thought we would start a build report about our two robots – I’ll start with a quick recap about where we are at/problems we have had so far and we will be sure to update it going forwards.

We are a group of robotics enthusiast from across the ditch, and we are just getting into the combat side of things.

For both robots, we have decided to start out with Banebots 20:1 gear boxes with 550 motors (4x on each) for the drive. This has worked out pretty well so far.

The Undertaker

Originally we only planned to bring Dreamcrusher to this years nationals, but decided that since we were spending the money to come, we might as well bring another robot so we will get to have more than 2 fights in total if Dreamcrusher gets knocked out straight away in the (possibly) double elimination. The Undertaker will be driven by my brother (Steven).

We started The Undertaker 4 weekends ago, so we are pretty happy with how it turned out. It is simply an invertable wedge built with 25mm steel angle welded together. We didn’t really run into issues with the build, so below is the final robot (for this year).

Photo:
https://drive.google.com/file/d/0B55eyg4wmER3VWt3QlFqMjl5RTQ/view?usp=sharing

And here is a video of it (pre paintjob) smashing up an old laptop:
https://www.youtube.com/watch?v=ERx4EoUos8w

It has plenty of drive power, and can push people sitting on a wheelie chair around.

Dreamcrusher

Dream crusher is a vertical spinner, built (mostly) out of 10mm aluminium plate. The base is currently 10mm polycarbonate, but we are planning on changing this to the equivalent weight aluminium.

Photo:
https://drive.google.com/file/d/0Bx6ALwF4U4rXcUVYLTc5NEVjYVk/view?usp=sharing

The first weapon we machined up for it was out of mild steel. This unfortunately blunted on the tip quite badly when it took a big hit.

Photo:
https://drive.google.com/file/d/0Bx6ALwF4U4rXUW1xVzlLZVR0T3M/view?usp=sharing

We have now machined another weapon out of Bisalloy, hopefully this won’t become blunt as easily. We are going to keep the original mild steel bar and weld some mining teeth to it, which will hopefully take most of the hit.

The original weapon set up had a Redback Racing 91 brushless outrunner chained up to the weapon. This worked pretty well on small targets (see videos below). However when hitting a larger item, it bent the motor shaft quite badly (using chain and no shock mounting is funnily enough… a bad idea). We shock mounted the motor, and the sprocket to the weapon and tested it again after straightening the motor shaft. The original (shaft bending) hit destroyed the internal bearings however and once we spun it up again the bearing shrapnel got sent through the motor, destroying the windings Sad a small motor fire followed.

Good thing we have cheap imported Chinese outrunners perfect for the job right? Nope. We do have spare imported Chinese outrunners, but as it turns out the shafts on these ones are 6mm instead of 8mm. With the recent disastrous experiments, we decided it probably wasn’t a good idea to run them even though everything is now shock mounted.

We ended up buying a Scorpion SIII-4035-380KV locally due to the time constraints we have. This seemed to work perfectly with the shock mounted set up, and seems to be able to dish out big hits without inflicting any damage on itself.

Dreamcrusher driving around:
https://www.youtube.com/watch?v=DWKsfXU2O-Q

Weapons test on small (~2.5kg) objects:
https://www.youtube.com/watch?v=qsSmYELQxEI
https://www.youtube.com/watch?v=Nz4VpXO6iuo
https://www.youtube.com/watch?v=uZ6chhMJ01g

Weapons test on 15kg hunk of steel:
https://www.youtube.com/watch?v=GZc4s0TzGf4

We have the front and back wedges and the top armor to attach still, hopefully they will be done by the end of the weekend.

We cant wait to meet you all in a couple of weeks and have a look at all the awesome bots! Laughing

Post Sat Aug 06, 2016 8:19 pm 
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Valen
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looking pretty scary there, good work!
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Post Sun Aug 07, 2016 12:42 pm 
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Nick
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Dream crusher drives extremely well and has plenty of weapon power; the competition is really heating up!
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Post Sun Aug 07, 2016 6:15 pm 
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RogueTwoRobots



Joined: 12 Jan 2008
Posts: 135
Location: Irvine, Scotland


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Really impressive looking bots, and well driven too. Are these your first attempts at combat robots? Fantastic if so Smile

Excuse my ignorance, but is there much of a combat robotics scene in NZ? If ever I was to move abroad, NZ would probably be top of my list, but need to make sure I can still get my smashy smashy fix Wink
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Post Sun Aug 07, 2016 9:38 pm 
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Jackbk



Joined: 07 Aug 2013
Posts: 22
Location: New Zealand


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Thanks!

There is not much of a combat robotics scene in NZ Sad someone tried to organize a tournament in 2013 but it was cancelled for some reason. Hopefully we will be able to get something started in the future.

And yup, this is our first *real* shot at them- apart from half building a full body spinner for the 2013 competition before it was cancelled. I was involved with the Vex Robotics Competition while I was in high school and my first couple of years of university though. These bots are certainly a step up, so we have most probably made a bunch of rookie mistakes. I just hope that when they lose, they at least lose spectacularly and put on a show haha

Post Mon Aug 08, 2016 6:47 am 
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marto
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Looking good.

Steve
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Post Mon Aug 08, 2016 10:50 am 
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miles&Jules
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looking awesome guys
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Post Mon Aug 08, 2016 11:02 pm 
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Jackbk



Joined: 07 Aug 2013
Posts: 22
Location: New Zealand


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So after doing what I was hoping would be the last rewire of Dreamcrusher before we leave, I noticed that one of the wheels was starting and stopping frequently while in reverse (going for a second, stopping for half ect). It was originally on a PWM Y cable where just the signal was split (and the power and ground not connected to the receiver), so during my trouble shooting I bypassed this cable and plugged esc straight into the receiver - the wires went up in smoke! Has this happened to anyone else before?

Pic:
https://drive.google.com/file/d/0Bx6ALwF4U4rXY3VudWJHVUtxdms/view?usp=sharing

Can it be caused by a configuration problem? I am a bit wary to set another ESC up just in case the motor caused it.

Post Wed Aug 10, 2016 12:23 pm 
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Nick
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Ouch! Was there another ESC plugged in to the receiver when the wiring smoked? It could be that the BEC circuits in the ESCs are supplying slightly different voltages and the current flow from them fighting to raise / lower the line voltage caused the meltdown. When using more than one ESC containing a BEC, its common to just use one to actually run the receiver and run only the ground & signal from the others.

Running only the signal to the ESC might have caused the irregular running; the earth return will be going via the power earth and adding a heap of noise.
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Post Wed Aug 10, 2016 12:46 pm 
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Jackbk



Joined: 07 Aug 2013
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Location: New Zealand


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Yep, there were two others directly plugged in at the time (receiver and other escs are fine thankfully).
That makes a lot of sense, i'll set it up so only one has the positive line connected and the others have ground and signal.


Thanks a bunch Smile

Post Wed Aug 10, 2016 12:49 pm 
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Nick
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Been there, done that! Laughing
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Post Wed Aug 10, 2016 12:58 pm 
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Knightrous
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On the other side of the coin, I've been running three BB85A ESC's together with all the BECs wired up at once with no issues for several years now. This one always seems to be a YMMV problem. Doing as Nick said though will fix the problem, it just opens you up to the failure point of if the ESC with the BEC dies, your bot dies.
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Post Wed Aug 10, 2016 3:08 pm 
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marto
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Notice how it is only the Ground wire which is burnt. The ground wire is common for the ESCs and RX (5v)

This means that if the main positive is connected but not the main ground wire it will try and pull all the power through the RX cable. Trying to power a motor through that wire ends with smoke.

Double check your wiring.

On the plus side if you replace that cable it should still work.

Steve
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Post Wed Aug 10, 2016 6:38 pm 
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Jackbk



Joined: 07 Aug 2013
Posts: 22
Location: New Zealand


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Thanks for the tips Knightrous and Steve - I might give it another go with them all plugged in (but grounded) to have a bit of redundancy.

It's good to hear the ESC should be OK - I'll put another pwm cable on it tomorrow and give it a test Smile

Post Wed Aug 10, 2016 8:43 pm 
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marto
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I am guessing in the wiring loom you have a dodgy -ve wire. This would explain the intermittent failure and the smoking RX cable.

Steve
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Post Wed Aug 10, 2016 8:49 pm 
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