[BW] GR-01 Build Diary

[Giles]

About to start making my first fighting robot and I've decided that a build diary would be a nice thing to do in order to record my progress and to perhaps get some tips along the way!

I plan to make a drum style spinner, currently deciding on design choices.

I have some of the required parts and some early cad work done so far:


UHMW 5mm sheet - top/bottom armour
UHMW 15mm sheet - side armour/structural support
Polycarbonate 5mm sheet - experimental, might use it for housing some fancy LED power indicator strips.
Turnigy 1000Mah 3s 30C battery - main power source
Turnigy 180w brushless outrunner motor - Weapon motor
12v 1200 RPM brushed gearmotors x2 - Drive motors
BotBits 10A brushed ESC x2 - Drive ESC's
Turnigy Plush 25A brushless ESC - Motor ESC


Early cad sketch done in my lunch break at work, rough around the edges but I hope it shows the general idea. I'm currently having a hard time deciding if I want an invertible robot that can run on both sides or if I want a robot that has a larger drum which is raised up slightly. Does anybody have a suggestion here?

I plan to make the armour from 5mm UHMW for now, with hopes to upgrade to 5mm alu or something even hardier in the future. For now though, I think UHMW is strong enough and easy to work with for prototyping.

Another problem I'm having at the moment is choosing wheels. I was hoping to use BaneBot wheels, but I didn't realise those went out of production. My next option is to 3D print some hubs out of carbon reinforced PLA and make my own. Unless there are better alternatives?

Over the weekend I hope to finalise a design, cut out a base plate and 3D print myself some motor mounts and placeholder wheels so I can attempt to get something driving around as soon as possible.

Thats all for now! Thanks for reading

[Revsmin]

Hiya and welcome to the sport
All in all its a very good start, you've clearly done your research!
As for wheels Shockbots recently started selling exactly what you need: Clicky
I think the only thing I can say is that compared to most beetles the brushless is a bit on the small side; for reference RPM has a relatively small brushless and even that's 500w. Lynx has almost 1kw but that does have a big ass bar to spin.
Hope that's helpful!

[daveimi]

Will you're a diamond!!!!!

In terms of being invertible don't worry about it, focus on spinner proofing. Been fighting a lot in the beetles this year and it's mostly made up of spinners and bricks. (And my biscuit / roses tins)

The feather and heavy events are laiden with flippers but somehow the technology doesn't sit well at beetleweight.

[Garfie489]

The feather and heavy events are laiden with flippers but somehow the technology doesn't sit well at beetleweight.

A flipper just won at Kinematic :P

But yeh, looks a fantastic first attempt. Just a note for the name however, there are featherweight drive motors with the same name :P

[Giles]

Thanks for the replies guys! GR-01 not a good name? Damnit! Using my initials was my "I cant think of a good name" cop-out.

I've been tinkering with some more layouts in CAD. I'm quite liking this design with little corner wedges attached. Is it a bad idea to run the robot on "skis" like this? I'm planning to use the 50mm Shockbot wheels that have been linked above, wondering if I have too little ground clearance with this design? I'm also wondering if 4WD with small timing belts would be a nice idea instead of 2WD. I was hoping to keep this build rather simple, but 4WD doesn't seem too much of a hurdle.

In regards to the weapon motor, I have previously been told its not so powerful in one of my previous threads. I intend to use it for now, as I have it already, but design with enough space to upgrade the ESC/Motor in the future once I'm happy with the rest of the robot.

[harry hills]

Bit boxy but you seem to know your stuff.

I really look forward to seeing what you come up with. Speaking from experience you're going to want 4wd though. Maybes try for a larger set of wheels at the back so you can be somewhat invertible, then smaller ones at the front which save space. You have to think a little bit with the belts and ratio between them but nothing too taxing at all.

[Ellis]

You have either really done your research, you've built robots before, or you're a complete natural! All the right stuff going through your mind by the looks of it, with solid components and you're clearly comfortable in CAD... is that OnShape?

Big drum+4WD is an extremely popular and successful shape in American insects through 6kg bots. These both happen to be hubmotor drums, but for example: http://3.bp.blogspot.com/-DipBqGVjqz...217_144935.jpg - these are both formidable.

I would push for invertability, at least such that you can drive to some extent (so's not to get counted out) when inverted.

As Harry says, really looking forward seeing what you do!

[Giles]

Thanks Harry and Ellis. I guess 4WD is definitely something to aim for. I'm still trying to figure out if im biting off more than I can chew if I do both that and invertible drive too... hmm..

@Ellis
I built the odd one or two robots when I was about 8 years old or so haha. This mainly included taking apart RC toys and attaching sharp things to them. I wouldn't say I have any other experience than that really... I built a quadrotor a few months ago, and that re-sparked my interest in electronics and robotics. I was always an avid fan of RobotWars (who wasn't!).
I'm employed as a game developer, so my day is split 50/50 between 3D modelling and programming. CAD tools come quite naturally to me, coming from a 3D modelling background, the tools are similar. I've not used CAD for too long, the software i'm using at the moment is called Autodesk 123D Design. Its free and saves project files to the cloud, so its good for doing a few sketches during lunch breaks at work and then having the file available at home later. A bit on the basic side though, I've used inventor in the past and that's a much stronger tool.

One last sketch for today. Just trying to think outside of the box a little and try something that isn't a cube on wheels. This is missing all the driving belts, base plates etc, but hopefully it gets the point across. It would be invertible and use 4 of 6 wheels at one time. The back pair would be driven by the motors and belts from those would drive the front wheels. I think this is starting to get away from my construction abilities though, So tomorrow I'll probably re-visit my previous design and upgrade it to 4WD.



Thanks for the kind words though everyone. Very motivating indeed!

[Gabe01]

No, no please don't go back to the previous design. If you can build the first one you can build the second one. Great ideas, keep on going. A recent lesson for me, spend more time in the design stage and less in the build.

[Gabe01]

You wouldn't even need to bother driving the front wheels

[J.A.G]

Look ace
can`t Wight to see some vids

[harry hills]

You will need to drive all the wheels. Your drum supports look lacking in material. Beef them up if possible. Other than that I'm a fan.

[Giles]

Ok I will pursue that wacky invertible plan Expect more detailed cad models soon.
Today I was rather busy, so haven't done a great deal yet. I did manage to model and 3D print some motor mounts however. I printed them in two parts, as I'm not sure if the back support is really necessary.


I'm starting to look at timing belts/pulleys. Is there a specific brand/size/type that people tend to use on beetles? Or does anything go? Also I assume I'm going to want a belt that is able to slip a little for driving the weapon? Or should I just use a timing belt on that too? Whats a typical axle diameter for a beetle too? The wheels I've ordered fit onto a 4mm shaft.

Sorry for all the questions

[Ellis]

As long as the mount doesn't mind the forces (3DP reliability is tricky in robots bigger than really tiny classes) you should be able to just mount from the front.

For timing belts, I strongly recommend HTD-series tooth profile. These can be had in 3mm pitch (search HTD3) which is ideal for beetles. They're extremely tough belts, I use them in bigger classes (5mm pitch) with success.

Weapon belt slippage (seriously you must be doing good research) is important, yes. You can either run the same HTD profile belt onto a non toothed pulley, which given the right tension will spin up fine (the yank from the brushless tensions the belt such that it grips like fury, but can still slip in impacts), or you can use ~4mm round belts in round groove pulleys. Less tough but more compact.

Weapon shaft diameter, I'd go no smaller than 8mm (assuming steel). 10mm feels right. If it's a drum you may need to go with titanium to save weight. For drive stuff, 4-6mm is the right region.

Edit: actually 8mm, assuming the drum bearings are positioned close up to the bulkheads, would probably be fine.

[Giles]

All that sounds good to me. Thanks for the recommendations.

For the 3D printed parts, I'm printing them in fairly brittle PLA plastic right now, but once I have prototype working as intended, I'll reprint them all in carbon fibre, which will hopefully be nice and light and strong. I don't have any other tools for making parts like these really, so its either 3D print, buy parts or send CAD files off to be milled (never done that before, no idea on costs)