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Jolt & friends - Team Overkill - NSW
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Nick
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Joined: 16 Jun 2004
Posts: 11715
Location: Sydney, NSW


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Robo Challenge day 3:

Hmm, maybe taking a brand new bot 20,000 Km wasn't such a great idea. On day 3 I had a bye for a handy but boring 4 points. After that the next match Wasn't until after 3 PM. Both Barghest (the electric lifter) and Utopia (the CO2 flipper) had problems and only Utopia was ready, but with a reduced CO2 capacity. that was good news as I expected to be double-teamed by the other bots.

Mr Mangle got spun up before Utopia box rushed and we met head on. Utopia had a bit more traction and was pushing Mr Mangle back until it's lifter suddenly rode up Mangle's forks enough to catch on the beater. Utopia got tossed several metres and landed near or on the wall - Mangle recoiled back a bit and stopped moving so the judges counted it out.

I can't find a cause for stopping in that fight; a test back on the bench showed both wheels turning so it wasn't a repeat of the dual drive ESC meltdown from last week. The bot still had power after the match and the link definitely didn't pop out. I still had radio control as I could spin the weapon up & down. It could have been high-siding as its hard to see whether Mangle's wheels are turning from a distance but it is really another mystery fault like the exploding ESCs.

I will go in one of the side competitions and as many whiteboard matches as possible tomorrow and maybe win something or just cause as much mayhem as possible.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion


Last edited by Nick on Mon Aug 28, 2017 4:06 pm; edited 1 time in total

Post Mon Aug 28, 2017 6:52 am 
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MoonSet416



Joined: 25 Sep 2016
Posts: 304
Location: Sydney


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That reminds me of the problem I had with my weapon esc in my fight against Insanity. After the match ended I drove tht bot to the gate before I tried turning the tx off, and turning it back on after like 2 seconds in hope to show that I might still have the weapon. The weapon was back on. Although the esc got fried right after starting, that was probably because I left it on full throttle even when it's not working properly. There's no way so much heat can build up in a second during spinup.

I suspect that the esc went down because of shock, it just needed a restart. Turning tx on and off quickly would not work though... I tried it in the middle of the insanity fight, (if the video eventually pops up on Youtube, look for where the commentator said I stopped moving for a while.) and restarting quickly didn't work for me.

Post Mon Aug 28, 2017 11:14 am 
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Nick
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Joined: 16 Jun 2004
Posts: 11715
Location: Sydney, NSW


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I had an idea overnight - it could be that conductive carbon muck that coated everything inside the bot. I tried cleaning it off with solvents but nothing has much effect on it.

Its still strange that I still had weapon control - that virtually eliminates the receiver and what's the probability of BOTH the drive ESCs cutting out at the same time? There is time to do more bench testing before we start battles so maybe something will show up.
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Post Mon Aug 28, 2017 3:43 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 304
Location: Sydney


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Yeah testing is always the best way to find out.

I reckon that if the carbon shorted something out along the main power line, the weapon should also stop, which is not the case. I think it could have been that one of the three phases of the drive motor could have been shorted. However, in that case wouldn't the other two phases be fine and the robot can twitch a bit?

Post Mon Aug 28, 2017 6:57 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Carbon residue isn't conductive enough to short out a power rail - its resistance would be too high. Residue is much more likely to bridge tracks on logic circuits in receivers and ESCs. The problem hasn't come back today so I am calling it a fluke problem.

Robochallenge final day

TL;DR: had a very fun day but didn't win any trophies this time. The full report will have to wait - I am completely knackered and need to sleep!
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Post Tue Aug 29, 2017 9:44 am 
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Nick
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Location: Sydney, NSW


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Continued:

Mr mangle was still fully working for the final day so I signed it up for everything I could: the Annihilator, a whiteboard and the Gladiator. Since there was little to lose, I fitted the low clearance anti wedge & flipper forks, the self=leveling wheels and the NTM 35-42 drive motors.

The first round of the Annihilator went well - I basically just avoided any trouble.



The second round didn't go so well; Equinox caught Mr Mangle from the side and threw it out of the arena:



That was to end of the Annihilator for me so I entered Mr Mangle in a 1PM whiteboard.



That was absolutely mad; Aegis is one tough bot to beat!

Gladiator:

After trading blows with 722 and Shard, Dennis caught me again with Equinox:



Post mortem

Stuff that worked:

The frame stood up to major hits from Equinox, shard and 722 with no bending or broken welds. I might think about filling in the scrapes but its not really necessary.

The new batteries were up to the job and stayed balanced, even after the Basher pack was severely depleted.

The front forks all worked although the heavy forks never had any major hits to test them.

The modified drive ESCs worked fine after half of them had the BEC disabled. One of them was partly mented by the Weapon ESC fire and still worked fine Smile.

The Self-levelling wheels worked fairly well but need to be a slightly larger diameter as the back of the frame had very little ground clearance.

To be continued once I get to Singapore...
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Post Tue Aug 29, 2017 8:10 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Other things that worked:

* The sliding power link door was effective, considering that it was mad about an hour before I flew out. It can be improved and lightened for next time.

* The new roll hoops never had to self-right the bot but protected against axe attacks and don't get caught on the pit button.

What didn't work:

* The enbiggened wepon motor Evil or Very Mad. Bigger is generally better but when the motor runs the battery down in two minutes and melts the wiring loom, its just too big for the job.

* The base for the power link. Its been fine until now, when the weapon motor partly melted the XT90 and the printed base it is glued into. The problem will go away withthe motor but the base needs to be printed in a higher temperature plastic like PC-Max. After seeing the epoxy melt around the XT90, maybe that needs to be changed too:



* The HK clone weapon controller; it may be damaged after the huge hit by Equinox. I might be able to battle harden the spare but it will need some extra testing.


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Post Wed Aug 30, 2017 10:20 am 
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MoonSet416



Joined: 25 Sep 2016
Posts: 304
Location: Sydney


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Just watched all the videos of i61, Mr Mangle delivered some really awesome hits.

I have an idea: how about some smaller (less stiff) rubber mounts for your electronics to reduce the initial impact.

Wow that weapon motor... I wonder how much amps it draws and what gauge of wire you are using as I'm now a bit worried about the new version of Contraption (with two weapon motor each drawing 120A peak) turning into a fire ball.

Post Wed Aug 30, 2017 3:42 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Good point about the shock mounts - I already did that for this event. They may even be a bit too soft and allow the electronics to hit the frame on one side, so I need to add little 3D printed bumpers as a backup.

I will definitely measure the motor current; all the melting happened at 20% power and for the Gladiator event, I turned the power down to just 8% and still had some good impacts on other bots.
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Post Wed Aug 30, 2017 9:18 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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The fire residue cleaned up easily with acetone; nothing else had any effect. As well as the dead weapon ESC, the carbon fibre mounting board, the top cover and one of the shock mounts need replacing which is not too bad considering the size of the fire.

After watching Neon and Telekinesis at Robochallenge and seeing the damage caused by Obliterator, I remembered how much I like under-cutter bots. Maybe its time for these two things to get together:



The motor outputs 7.5 KW continuous with a 15KW peak. It is limited to 8,000 RPM but should have enough torque for a quick spin-up, which is the weak point of many large diameter horizontal spinners. The downside is that the motor weighs 1.2Kg and needs a 12S battery pack, so there isn't much weight for heavy armour.
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Post Fri Sep 01, 2017 2:00 pm 
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maddox



Joined: 21 Dec 2006
Posts: 750
Location: Belgium


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Seeing Hannibalito after a fight with Caliope, I understand the need for more and better armor than 12mm thick HDPE over 3.2mm Hardox.

Post Fri Sep 01, 2017 2:40 pm 
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Valen
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Joined: 07 Jul 2004
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Location: Sydney


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weren't you just complaining about not having enough battery and needing smaller motors? Very Happy
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Post Sat Sep 02, 2017 6:26 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11715
Location: Sydney, NSW


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Well, I never said I learned from my mistakes! Laughing Its a different bot and for a successful large diameter spinner, I think it either takes a set-up like Glen's high speed in-runner and a heap of gear reduction, or a very large diameter, high torque out-runner. Since I already have the motor, I might as well go with that option and play around with the belt reduction ratio to get a reasonable speed without frying anything.

Its not that hard to make a test rig for the motor and bearing block, so once the shaft is made from a length of cheap Chinese titanium, I can test out just the weapon and decide if the project is worth doing.
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Post Sat Sep 02, 2017 6:56 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 304
Location: Sydney


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IMHO that motor is great for a horizontal spinner...

It does have higher power, but on 12s it probably won't draw crazy current, saving the wires. Also it looks really thin... Imagine Obliterator but with the motor mounted on the top cover right above where the blade passes through, and now you just saved a whole lot of space in the main body.

Post Sun Sep 03, 2017 7:18 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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I am hard at work on the CAD; the motor will be tucked inside where it can't be damaged and as most of the parts are thin the frame can only 60mm high, which saves plenty of weight on armour. Damage wise, I don't know how this bot will compare to Obliterator. The weapon bar (straight off Scissorhands) is only 2Kg but its a larger diameter and much of the weight is concentrated out at the tips for higher MOI.
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Post Sun Sep 03, 2017 7:36 pm 
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