Lodestone (Team Picus Telerobotics beetleweight adventures)

[joey_picus]

Hello everyone! To cut a very long story very short, I went to the Kinematic event in Clydebank on a whim last August and, aided and abetted by Jamie McHarg, Steve McGregor, and Alasdair Sutherland, I had a great time watching and decided to build a beetleweight. Ten months on (I signed it up for the beetleweight championships as Schiaparelli, but a schedule clash came up so I had to drop out ) here's a rough summary of where I'm at.

My original thoughts were to try and do something a bit different - in Scotland, I'd seen a lot of the standard 1000rpm 25mm gearmotors broken or stripped, and it's not my instinct to use what everyone else uses (which may explain my usual lack of success!). Initially I thought I'd use a pair of military surplus gearmotors I had lying around, but they ran at about 90rpm on 28v, so some head scratching happened. I'd played around with a tracked design , and got as far as lashing together a prototype using some Makeblock tracks*, but the tracks themselves would have taken up about a third of the weight and I had trouble sourcing suitable motors while keeping it all in 1.5kg (it turns out standard motors are standard for a reason, who'd have thought?). And so it came to pass that plan...E? Q? Д? From somewhere beyond the reach of the Latin alphabet, was born Operation Use Microsoft Paint To Come Up With A Design In One Hour And Tack It On To Harry's Lasercutting Order. And I looked and saw that it was good:

harry's lodestone cad.pngbeetlesweater.jpg

As a result of literally being thrown together around whatever was available/on my desk, the result is an entirely overkill lasercut 5mm stainless steel frame containing entirely underkill 13mm Maxon gearmotors. Powering this winning combination of underpowered and slow are two Scorpion Mini speed controllers (obtained from Dave Weston on two separate occasions) and the biggest 3S lipo that would fit comfortably in the frame. The wheels were a bit of a nightmare because the 3mm bore ones I got from Robot Marketplace** turned out to be 1/8", leading to a frantic search/testing process, but eventually I settled on some slot car wheels from either Spain or Portugal, I'm not too sure which but the postage was more than the wheels.

beetle in bad lighting.jpglodestone's shininess will consume us all.jpg

Lodestone in its almost finished state - so named because it's about 90% iron and naturally points north - has a 2mm lasercut stainless baseplate, and I've got some of the 2mm Hardox for a top cover. My scales don't go higher than 200g but I think I should have a fair bit of weight left - unfortunately, fitting a weapon into the front section has proven problematic so I think it'll just go on wheel guards and more armour. It's not going to be quick, or especially nimble, but it's been fun to work with slightly bigger parts than I'm used to, and given the current state of beetleweights I think 'be very low, deflect impacts, and wait for opponent to break' has half a chance of being a valid strategy!

*I have far too much of these so should someone want some, I might stick them up for sale at some point
**ditto

[daveimi]

Looking good

[Albear]

nice! Are banana's for scale?

[mrsam]

Looks good, very compact and strong.

Only thing i will say, with the wheels that far back and the chassis that long it will drive like a canal boat.

[joey_picus]

It actually is slow enough that that isn't a problem somehow? XD it's less a canal boat and more a...Reliant Robin with bricks in the passenger seat? It has enough torque to not have difficulties with driving or control but maneuvrability is pretty awful regardless.

Thanks for the comments everyone The bananas aren't deliberately for scale but it is quite tiny - the idea is partially to pass under the worst of most spinners...

[daveimi]

Which ESC's you using?

[harry hills]

5mm stainless steel frame containing entirely underkill 13mm Maxon gearmotors. Powering this winning combination of underpowered and slow are two Scorpion Mini speed controllers (obtained from Dave Weston on two separate occasions)]

As per first post

[joey_picus]

Specifically the old-style ones (http://www.robotmarketplace.com/prod...ORP-MINI2.html) - I've actually had them for several years and only now had a use for them!