Beetleweight "walker" - build diary

Hi all,

It's been a while since my last post on the forums so before I start, a quick update with Strix 2 and some context for this build. Due to my upcoming exams, I've decided to postpone my robot building until after May, which means I only have 3 months to get Strix 2 ready for the Featherweight Champs this year. I'm really happy with my design and I want to do it justice by building it to the highest standard I can, which just won't happen in that time frame. So I'm aiming to have it ready for the 2020 champs.

I think this is the perfect opportunity to have a crack at my first beetlewight, as I'm confident I can build one in 3 months.

Inspired by classic walkers like Gammatron, I've decided to have a shot at a "walker" of my own!
Note the quotation marks, because as far as BBB rules are concerned, this is a shuffler. So it'll be allowed 50% weight increase to give a max possible weight of 2.25kg.

Attachment 8712 Attachment 8710 Attachment 8711

My CAD is still in pretty early stages - I will continue to change it until my exams are done, after which I will build. For now though this is the sort of look I'm going for.

I've had a prototype of this walking mechanism as a fully operational LEGO robot for a while. Conveniently it is almost the exact scale as UK beetleweights. So with a few changes I'm confident that this machine will really walk if I can make the parts properly.

*Inspired by Jason of JKBrickworks, because I am absolutely not smart enough to come up with this on my own!-https://www.youtube.com/watch?v=cZa-IWwk36s

Here is footage of my prototype which I filmed a few years ago. This was pretty much as fast as I could make it without the mechanism being too weak or unstable. So I'm going to aim to achieve this speed with my beetleweight.

https://www.youtube.com/watch?v=IYeD...ature=youtu.be

Since I have a bunch still kicking around, I'm thinking of using an old style 12v argos drill motor on 3s to power the hammer. I'm going to need something with plenty of juice to self-right this thing. With a robot like this I think I need an entertaining weapon if the machine itself is going to be so slow.
I'm also going to put this wide plough on front - I need something to keep spinners away, as any decent horizontal spinner will easily mangle the legs. Nonetheless I will absolutely be making lots of spare legs and linkages.

So yes, I am starting this build with full knowledge that it will likely never win a fight. I just fancy trying to make something that is a bit unusual! (And hopefully works!)

Anyway! So the main reason I'm making this post is to ask for some details about beetleweights - I don't want to spend ages on this CAD if this isn't going to work from the beginning.
Can anyone recommend a nice torquey gearmotor for the walking mech? I see these 12v 25mm motors are popular, but apparently some are worse than others despite looking all the same. I'm after something with a slow speed, around 100rpm. I can't find any of the "good" plastic-backed 25mm motors with anything except a 1000 rpm gearbox - so I'm thinking of using these, although they are quite heavy.
https://www.technobotsonline.com/pol...red-motor.html
I'm also wondering what sort of hdpe thicknesses people use on Beetles? I'm already over the weight limit - what is the lowest thickness I could scrape by on for chassis materials? I'm thinking that the legs will probably be hit and broken before the chassis of the robot will, so it could be pretty thin.

I use one of the Pololu motors in Shu! for the lifting arm but they are indeed heavy. Two with appropriate cam gears shouldn't eat that much into the weight allowance though.

Ok cheers - If you can use these motors for lifters then it sounds like the sort of thing I'm after. :)

I'm afraid I don't have anything useful to add, but that looks great. It has a really nice mix of mechanical and biological features. I expect it's going to look quite funny ambling around the arena!

Thank you, :) That's the look I'm going for. Sort of industrial, like it just walked out of run-down scrapyard.

Quote:

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I expect it's going to look quite funny ambling around the arena

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- haha that's the idea, mate! :lol:

So my CAD has been refined and upgraded significantly since my last post so it's time for an update!

This design is meant to look like a sentient machine from a derelict sci-fi junkyard. The logo in the middle will light up in cyan when the robot is turned on. I've decided to call the robot Omikron - I think it sounds weird and futuristic which matches the overall theme of the robot. Omikron is a letter from the Greek alphabet and literally means "small o".

In terms of tech specs there has also been some changes. It turns out that the 2.25kg weight bonus is not universal across all beetleweight competitions. After asking about this on facebook it sounds like the limit is currently 1.8kg, which is significantly less than I thought it was. This has been the main driving factor behind the design changes.

I'm now using lighter Pololu 25mm 99:1 gearmotors for drive. Thanks to mark_m's post in this thread I'm pretty sure they will be able to move Omikron on a 4s or even 3s LiPo.
Chassis and front scoop is mostly 8mm HDPE, baseplate 5mm, top armour is 2mm.
The legs are 8mm hdpe and will be watercut - linkages will be 3-D printed due to their shape.

Unfortunately I'm not sure if there'll be weight for my beefy drill motor to power the axe. I might have to step it down to something lighter down the road, but I will concentrate on getting the walking mech working first and seeing what weight I have to spare. Sadly I've had to replace the chunky mallet with a slimmer axe-head to save weight, but I do think it suits the aesthetic of the robot better.

I think that's most of the new details down, once I'm 100% happy with the CAD I will order in the legs and chassis materials.

I'm still having trouble uploading images to my posts so I hope you can view these images

https://www.flickr.com/photos/159759...posted-public/

https://www.flickr.com/photos/159759...posted-public/