I have only been to one and they were a little bit more expensive than I expected. Was literally first one I found can't even remember name. It is one of the more acceptable things to go to fyswick for. _________________ Steven Martin
Twisted Constructions
http://www.botbitz.com
Thu Jul 09, 2015 4:34 pm
seanet1310
Joined: 08 Nov 2006
Posts: 1265
Location: Adelaide
That and go to the poor excuse for a fresh produce market.
Best of luck finding cheap steel, depending on the sizes you need, you may get more luck finding cheap merchant steal in offcuts or cut to size instead of steel sheets. Downside is that they are not very wide. My one and only steel bot was made out of two pices welded together to form the base because it was cheaper and easier than getting plate steel of the right thickness cut. That was a very small bot though. _________________ Remember to trust me, I am an Engineer.
MetalMart Resells some of the better pieces of scrap they pick up, so hopefully I can find a small bit of sheet for cheap. I'll head there tomorrow and see what's what. Thanks for the suggestions.
I think my main problem will be constructing the drum. I'm not sure how I will get enough strength to the axle, as it's sort of three parts: Big Tube, tube endcap, axle. Is there an accepted way to do this?
Thu Jul 09, 2015 5:10 pm
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
Could this be better for an easily constructed drum weapon? Just bolt all the bits together? It still allows for friction drive.
Maybe build a driving block of wood, it might give you a better idea. Looking pretty good for first design but until you actually start making it you won't notice many of the issues.
For example you would assume you would mount the drills at the ends. However you really need those mounts flush against the ridge otherwise your wheels will slide inwards and jam on the chassis. It also puts a lot of force on the two tiny screws that hold on the motor.
Also a drill motor driving the weapon will be very slow.
Last edited by marto on Fri Jul 10, 2015 12:11 am; edited 1 time in total
Thu Jul 09, 2015 7:38 pm
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
Forgot to mention my CAD files for the front mounts of the motors (around the gearbox) were only STL format and not supported by my program so I left them out
Good point, definitely need to upgrade the weapon motor by the time October comes around. Just trying to get something up in the next week so I can nab that last competitor spot! I'm hoping the friction drive will mean the weapon motor is relatively safe and I can invest in a good one down the track.
I meant the rear ones. The motors are unsupported by gearbox. They are held on by two m3 screws. Which will be only thing stopping your gearbox bending in half. Particular when glen throws it 2m in the air.
Maybe look at smaller length of the weapon. And have a look for reboot (drum bot) one of the old threads. _________________ Steven Martin
Twisted Constructions
http://www.botbitz.com
Thu Jul 09, 2015 8:05 pm
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
Looks good Guessing for a sportsman class? Cause the drill motor would be fine for that.
As for the weapon at some stage you will need access to a lathe or welder to make it. The easiest way would perhaps be to buy an appropriate size metal tube, have some discs laser cut to fit the end - my metal shop sells these pre done so maybe you can find em too - then weld those in along with a solid axle.
Although i do recall the robot reboot having plastic wheels sikaflexed into the sides of the tube at some stage..
Most engineering shops sell these pressed bearing blocks cheap. They'd work well.
Thanks for the tips. I looked at a few of Rotwang's bots and they did use a wheel as their 'hub' for the drum ( http://robowars.org/forum/album_pic.php?pic_id=897 Back in 2003! 12 years ago ). It actually looks like they just used cheap plastic ones as well. Definitely a good idea if I can find something of a good size, because it can have built in bearings to save some work. I just need to take my ruler and check out what size the hubs are. The hub out of something like this: https://www.masters.com.au/product/100746230/richmond-semi-pneumatic-rubber-wheel-150mm would be good if it fits.
All parts looking easily replaceable which is goooooooooood because I know they'll need to be replaced. Ready for a big buy tomorrow then hopefully some fabrication pictures should show up in the next few days!
Have any luck? _________________ Steven Martin
Twisted Constructions
http://www.botbitz.com
Fri Jul 10, 2015 7:16 pm
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
Pretty good I think. I went to MetalMart after hearing about their scrap section.
1.5m of 50*50mm 3mm Steel Angle for ~$12
0.5m of 90mm Bore 4mm thick Steel Tube (for Drum) for $19
0.5m of 75mm wide 10mm thick steel bar (for drum mounts) for $10
And from the Scrap section I got 1200*1800mm 6mm Thick Aluminium for $50
The scrap section was pretty good for sheet metal, there was heaps of good condition stuff, I'm sure others would get a better price than me as I seem to get a bit exploited at places like this when the prices aren't properly set, I'll wear a fluro jumper next time to blend in. You grab what you want and they weigh it and give you a price, it was good fun and I grabbed some random stuff for other projects too.
Yup I could have done a lot worse, I've got about five times as much aluminium sheet as I actually need because it's been such a rare commodity up to now
I've got access to a mitre saw and a baby 400W bandsaw, but the tube might pose problems... We'll see! Hopefully I can get access to the workshop tomorrow and make some real progress!
Fri Jul 10, 2015 9:40 pm
miles&Jules Experienced Roboteer
Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD
Awesome….another bot. Cant wait to see the metal take shape. My recommendation …don't go above 4s and use kmart 18v drills..and they should last. _________________ Miles Blow - Julie Pitts
www.mulesfilm.com.au www.wombokforest.com.au
-Pickasso- Vivid Sportsman champion 2015
Last edited by miles&Jules on Fri Jul 10, 2015 11:09 pm; edited 1 time in total
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Guessing for a sportsman class? Cause the drill motor would be fine for that.
). It actually looks like they just used cheap plastic ones as well. Definitely a good idea if I can find something of a good size, because it can have built in bearings to save some work. I just need to take my ruler and check out what size the hubs are. The hub out of something like this: 
My recommendation …don't go above 4s and use kmart 18v drills..and they should last. 