🦞 Lob-ster - mammoth inspired beetleweight build diary & iterations!

Hello! First ever write up for me, I’m not great with writing words, but I thought I’d share this mammoth journey with you! If you’re interested in seeing all my builds, they’re all here.

As soon as I’d heard about Baby Shoes the gangly ginormous rotational lifter bot I was greatly inspired:

Baby shoes - credit Ricky Willems

When a heavyweight version showed up (MAMMOTH!) at robot rockus and filled up the arena and tossed robots around I was obsessed! Seeing it on TV, particularly jumping over HUGE, was so beautiful and stupid, it’s the peak of robot combat for me, I really wanted to see this at beetle scale.

In 2021 I built Lob-ster, a very mammoth inspired beetle with my usual masses of red 10mm HDPE & crustacean flair:

It had the standard bbb drive gear (shameless plug), but the weird part is the weapon - needing loads of torque, I decided upon an 7.2V ikea drill (on 4S!) - I’d heard german roboteers used them for drive on their 6kg raptorweights, so I thought must have some beans as a beetleweight weapon. Using 5M toothed belt with 4:1 reduction seemed to have decent power!

I gave it a test fight at the crew whiteboard at our first post lockdown beetle event (Summer Showdown) with this solid 15mm HDPE bar, did a few nice bot tumbles but it couldn’t self-right, timestamped here if you want to see.

After some testing, more of a box shape (ala what mammoth used to have) seemed to work great for self righting, and with the multiple stages of teeth also for scooping up other robots - it’s so ground scraping it hits the ground as it spins :stuck_out_tongue:

check out this sexy slowmo doing the mammoth summersault:

and lobbing (get the pun now?!) an old crab chassis with added feather lipos inside to get it to weigh 1.5kg!

These tests are what excited me, it felt like it was true to the big lad, probably one of my proudest robot moments! Doing proper testing really is what makes things do the thing.

So send to the 2021 champs I did
:lobster: fighting K1 & Baba Yaga
:lobster: fighting GoodBoi
:lobster: fighting Nightfury
:lobster: fighting many bots in whiteboard

I don’t want to write an event report but the summary is: decent tosses, decent self rights, many wheels and drive motors removed! V happy overall, but things to be improved!

As it took a lot of different iterations to get something to do the thing I kept putting off a v2 for a loooong time. Finally got round to it this year as I had some new toys to play with:

For the drive - repeat max, with lego tyres I’ve seen on some US bots:

For the weapon upgrades I had a few spicy ideas - a 550 drill, a silly sensored brushless thing from Gareth/Felix, Henry’s fun 28mm brushless… but not giving enough time to the build got the better of me and so I stuck with the ikea drill (after having a great outing with it with grab crab v3 at rapture in 2022)

So a few quick CNC sessions later here was v2 of lob-ster - a bit smaller in all dimensions, with thinner bulkheads but most importantly protected wheels!

googly eyes yet to be added…

I took lob-ster this weekend to Robot Rebellion Chichester and had a great old time.
All fights with timestamps here.

Spinner wise fighting horizontals x 3 and a drum and losing 0 wheels / drive motors in the process was great. (however was declawed in final fight)

Chuffed about how the thing drove and controlled fights, I ended up going 5:1. I think getting 5th place? not entirely sure.

Sadly not so chuffed about the weapon - it never had the beans of the original guy. The 40mm smaller bar definitely had less throw. Ikea let me down with random clutch issues. The belt stretched, slipping and tearing, and whatever tensioning I did, I couldn’t get self righting or liftning from about half way through the day. I do wish I’d given it more time and also brought something bigger and sillier to the weapon, as somersaults is what this robot is for! Next time :slight_smile:

Thanks for reading my rambles, happy botting!


Fantastic result even with the weapon woes.

What was the nature of the clutch failure? I’d be reasonably confident in suggesting a tensioner may solve your belt troubles, forcing more wrap meaning less chance of slippage and failure that Way.

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Reckon a proper tensioner (with bearings/bush) close to the smaller pulley to force the belt to engage with more teeth would help a ton.

Also that old self righting video is still one of the most satisfying robot videos I’ve ever seen! :heart_eyes:

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I think you’re both right that a proper tensioner (bearings) would have been better than me just having HDPE blocks to force some tension around the pulleys - I think I got lazy as it had worked well on the past lob-ster and grab crab! Also Felix has mentioned reinforced belts too - mine started tearing!

I do need to take the drill apart and see what the failure there was, as it kept slipping too, potentially grub screws locking the clutch had backed out a bit?