Got my drives sorted. I did have to redo the motor mount to fit my motor (with sleeve on), hole diameter 37.5mm in my CAD model for reference. The gearbox mount fitted well.
Now gotta get into the workshop to get the heavy work done, then on to the weapon!
Thu Jul 23, 2015 6:54 pm
miles&Jules Experienced Roboteer
Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD
Bought the Al box section for my mounts, and secured the two main bits of my frame together. It looks like no difference to my previous photos, but drilled and countersunk 8 6mm holes. It took way longer than I thought it would.
Is 6mm Aluminium an overdone featherweight base? everyone puts their armour mass into the side armour and it's obvious why, so am I wasting weight here? I'm thinking of just using polycarbonate for the top cover now. I've got heaps of it lying around.
so far Steel+Al weighs just under 5kg. Solid as anything though.
Next workshop day I should be able to complete the drill mounts and grind the wheel holes in the base, maybe even have something driving. The electronics all work, though there's substantial sparking when stopping or changing direction on the drill motors, makes me very nervous.
Sun Jul 26, 2015 9:16 pm
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
Looking good chief, if you weld the angle together then sure you should be able to drill some big holes in the bottom pieces.
Those brushless motors are really good too, I've used one on a compressor and they have impressive torque for a hobbyking motor.
The sparking is common especially when the drills are new as the brushes aren't bedded in all the way. Although they typically don't last long enough to wear in haha. _________________ www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz
Sun Jul 26, 2015 9:27 pm
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
Yeah Glen they are great, grabbed a couple on liquidation for cheap but that was a couple years ago now.
In other news, I've got Drum Hub 1.0. Will see how they fit tomorrow, should press fit nicely for welding or epoxy. Bearings included and $6.50 each so the price is definitely right. The steel is pretty soft and thin though, maybe filling it with some sort of epoxy is called for, but tests will determine that. A large part of the design choices have been made on cheap availability of replacement parts and this is no exception. They take a 1/2" shaft, I might go exotic on the shaft material just for fun.
Mon Jul 27, 2015 9:08 pm
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
having one solid top or bottom isn't a bad idea, it'll help stop the frame from turning into a parallelogram on a big hit, but yeah when you are over weight thin that bit down some ;-> _________________ Mechanical engineers build weapons, civil engineers build targets
Tue Jul 28, 2015 7:21 am
miles&Jules Experienced Roboteer
Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD
5mm aluminium is pretty light weight….its less than half the weight of steel…..thats what piccasso has for its base.
you could probably make the length smaller ..also off centre wheel alignment will make you bot smaller and drive straighter. _________________ Miles Blow - Julie Pitts
www.mulesfilm.com.au www.wombokforest.com.au
-Pickasso- Vivid Sportsman champion 2015
Tue Jul 28, 2015 8:40 am
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
Thanks, I don't really have any experience so I wasn't sure, the Al seems really hefty. If I'm over the weight limit first step will be to follow Glen's suggestion and drill some holes in the bottom of the steel angle where it meets the aluminium.
With off centre wheel alignment... it just intuitively seems like it would mess with steering a ton, I just can't make it make sense in my head. Certainly the 400*250mm shape is pretty wide, next version of my bot I'll definitely try to bring the width down, as it would have great weight returns due to the shortening of the drum. I've been looking at right angle drives for this purpose as well.
Tue Jul 28, 2015 11:27 am
miles&Jules Experienced Roboteer
Joined: 19 May 2010
Posts: 3973
Location: ipswich QLD
Yep Pickasso and Warning are both champions and they are off centre drive. The side by side is great for spinning on the spot…..but for straight driving you cant beat off centre of 4wd. thats how me and jules do al our bots now….but maybe for a drum it doesn't matter…just go side by side.
Also invertible is important are you going to cut wheel slots in the ali so it can drive updated down? _________________ Miles Blow - Julie Pitts
www.mulesfilm.com.au www.wombokforest.com.au
-Pickasso- Vivid Sportsman champion 2015
Tue Jul 28, 2015 1:33 pm
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
And the wheel holes are cut thanks to my Aldi Jigsaw.
And the drum hubs fit perfectly for welding:
Annoyingly, the hub was meant to take a 1/2" axle, yet my special high tensile 1/2" axle has a fair bit of wiggle room... Going to have to order 13mm or something.
Next workshop day I'll definitely be able to test drive!
Tue Jul 28, 2015 10:25 pm
Nick Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
Do you know what sort of bearings the wheels have? They look like they are formed into the wheel hub, so they are likely to be low tolerance & sloppy. They could also be imperial 1/2" or 12.7mm. _________________ Australian 2015 Featherweight champion
UK 2016 Gladiator champion
Wed Jul 29, 2015 6:56 am
Thomas AIC
Joined: 22 Jun 2009
Posts: 151
Location: Canberra
They are ball bearings that have been pressed into the hub. The packaging said they fit a 1/2" (12.7mm) axle so that's what I purchased, but it's too loose for the bearings to function properly.
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