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WITNESS ME!


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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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WITNESS ME!

Greeting all,

I watched your matches at Sydney and now am super hooked on building a bot. SO hooked I've already built one that is going to destroy EVERYTHING FOR THE GLORY OF THE IMMORTAN!

Meet: MINI FLAIL!


Much Fear, Many Destruction, Wow. (it barely moves, is just a butchered RC car from ALDI...)

But yeah, it's a start - I've got great plans for a flail wielding bot, EPIC FLAIL (I'll keep the chain short so it's not an entanglement issue). Though unfortunately I'll be firmly in the grips of a thesis in October so I won't be able to make the Brisbane comp - you peeps will just have to wait to be destroyed by my tupperware tornado.

Post Mon Jul 06, 2015 9:24 pm 
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marto
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Joined: 08 Jul 2004
Posts: 5443
Location: Brisbane, QLD


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Hahah awesome.

Should come up to Brisbane anyway its only one weekend. I am sure that won't be spent doing thesis work. Throw together a sportsman in a similar fashion....

Steve
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Post Tue Jul 07, 2015 9:16 am 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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So I've been quietly lurking while I acquire parts and tools to build with and I finally reached a point this weekend where I could have a crack at building stuff.

So as a just for starters bot I'm building a two wheel thwack bot/wedge beetleweight. The plan is to build another simple beetle so I can battle with my housemates.

The current build is using:
Turnigy TGY-i6 transmitter with 6ch receiver
2x 10A cheapo ebay ESCs (i'm going to do a botbitz order soon)
2S 1.6Ah Lipo
2x 12V air compressor motors
2x 75mm caster wheels I got from the local discount shop

The top and bottom will be chopping board and the sides are some rectangular Aluminum bar. I got all the electronics and mixing done easy, it's the construction side that's going to be fun...

My original plan was to go with a pulley drive system because the motors don't have a reduction, but my test build/proof of concept drivetrain was awful, mainly due to me trying to make pulleys and not having proper belt for it. But that's why I done a test build! So do you guys know a good place to get small pulleys and belts? For like a 10mm drive shaft?

But the new plan is to go simpler and lighter and just drive the wheel by rubbing the small gear on the motor against the tire. Simple and should work for now, at least will give me something that drives.

Here's my failed drivetrain:
It was pretty late in the afternoon so I just slapped together what I had with a rubber band, worked for about 2seconds...


The next attempt should be neater as I've ordered a stepped drill bit to make nicer holes for the motor and bearings rather than using a dremel with adjustable hole cutter (worked by was messy)

Post Sun Sep 27, 2015 11:00 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11745
Location: Sydney, NSW


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You are going to need much more gear reduction than that, otherwise the wheel will spin much too fast and will not have enough torque to move the bot. We generally use somewhere between 16: and 25:1 with typical 550 sized motors. Those larger air compressor motors may go a bit slower, but you are still going to need extra reduction.
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Post Sun Sep 27, 2015 11:53 pm 
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andrew



Joined: 16 Jun 2004
Posts: 3108
Location: Castle Hill, Sydney. N.S.W


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dude, for drive for a feather drills with red wheels will be your best friend

Ive got a stack of drills here i bought cheap, all metal gears, what little testing ive seen they seem solid providing you dont overvolt them over 14-16 volts (18 volts maybe but pushing it for battle)

Ill happily setup and sell you a whole drive for like $30 (two drills with wheels attached) and shipping cost.

For feather drive drills are simple and fairly reliable

more moving parts you have in a robot more things to go wrong
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Post Mon Sep 28, 2015 12:51 am 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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Nick,
I was trying to figure out the reduction on a drill motor to give me something to aim for. So about a 25:1 is typical? My pulley system was going to achieve about a 4:1 reduction and I didn't know if it was going to work, the biggest problem I anticipated was not enough friction on the plastic pulleys (turned out I couldn't get everything straight so the belt just fell off). But I figured I'd slap it together to see if it works. Whenever I try something new I usually plan for my first attempt to fail, learn from it then improve.

The new plan will get about a 10:1 reduction, so I'll try that.

These compressor motors are very similar to the ones in the 12V kmart drills, just no gear box. I've got a couple of kmart drill motors out and they seem to have a slightly lower internal resistance than the compressor motors (about 0.3ohm vs 0.5ohm).

Andrew,
Thanks for the offer but this is for a beetle and drill motors are way too heavy (400g each vs 200g each for these compressor motors). I've already bought 10 ozito drills from Prong that will be used for a feather down the track, combined with electric window motors from my old Volvo to make a lifter...but I've gotta improve my building skills before I try that.

I've had a look at other beetle builds on this forum and elsewhere on the net, but i'm taking a what i've got sitting around/what I can easily get my hands on approach - and Kmart is 400m from my house lol.

Post Mon Sep 28, 2015 5:30 pm 
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Valen
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Joined: 07 Jul 2004
Posts: 4425
Location: Sydney


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this is what we did when we had a belt drive


It didn't work very well because any movement in the frame misaligned the pulleys.
Plan-B which used the same belts worked well because it had fibreglass panels inside that mounted the reduction system and they were isolated by a few inches from the sides of the robot.
In order to make that setup we made the pulleys and the belts because we couldn't get belts short enough.

In robotwars in general the most critical thing is isolating your alignment critical components from external influences.

I'd strongly agree with andrew, drills and red wheels (or something better than red wheels if such a thing exists?) is really your best bet for getting something running.


For beetles you want the 1000RPM gearmotors from ebay, somebody else will probably be able to direct you to a reputable seller.
ones like this
http://www.ebay.com.au/itm/1000RPM-DC-12V-High-Torque-Gear-Box-Electric-Magnetic-Speed-Reduce-Motor-/301706426830
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Post Mon Sep 28, 2015 5:44 pm 
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Knightrous
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Joined: 15 Jun 2004
Posts: 8469
Location: NSW


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If your looking for a "ready to use" setup that you can literally bolt or weld into your robot, check out the 24v scooter assemblies.

https://www.motiondynamics.com.au/100w-belt-drive-scooter-wheel-24v-1200rpm.html

These units have proven to be very successful in the past as they have a low power draw and can utilize small batteries and esc (Saving $$$)
When you become a more experienced builder, you can then discard the frames and reuse the components.
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Post Mon Sep 28, 2015 6:40 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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Thanks for all the tips guys. Valen, those 100rpm gearmotors look sweet - I'm pretty sure they'll go into any future beetle builds.

So here's the current version, I've named it Corpus Flailossus. It drives, just have to make a master switch and mount the weapon.



The original chassis had it about 80g overweight, so I made it shorter so it could lose some weight:

Post Mon Nov 09, 2015 7:16 pm 
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Jaemus
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Joined: 01 Apr 2009
Posts: 2674
Location: NSW


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Nice! A completed robot. What weapon do you have planned?
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Post Thu Nov 12, 2015 12:43 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 125
Location: Newcastle


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I've only just got back into the bot now since the beetle event got postponed - the weapon will be a simple thwack flail and some spikes on the front. Working on some plans to make a wedge beetle as well.

Post Tue Jan 26, 2016 9:40 pm 
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