🦀 Grab Crab v4 - turning the suplexing to yeeting!

I’ve finally made a new solo build video, I am not a huge fan of talking solo to camera… I used to do this more often, I think it was more useful when I used to do builds by hand with much less CAD, but still good to share the process I guess… enjoy! It’s got a good summary of my last few years of builds and what kinda thing I try go for :slight_smile:

To summarise the build in text form:

Firstly, here’s grab crab v3 before rapture 2022:

And after:

I had an onslaught of spinners and was super happy to come off ok against most of them until I got very stratus’d.

So for v4, I decided to keep most of the same chassis design with a few tweaks, but try out a new beefy motor - the ‘strangbox’ - @Strang_H’s set up on bonbonbonbon’s lifter - a 2836 on 100:1 28mm gearbox - BEANS!

The chassis was my usual CNC’d boxy red HDPE PE500 interlocking 5 and 10mm:

Now upgraded to repeat max drive (had been great on :lobster: Lob-ster earlier in the year, and repeat AM32 ESCs which seemed very responsive… so responsive in-fact I ran one on the weapon too. I decided toothed belts had caused me enough pain so stuck with trusty PU belt on drive and fun lego tyres, with TPU cores printed by the excellent Joe M!

I’d initially mounted the weapon motor for direct drive as in my innocence 37D motors happily stall out this way

I’ve now used barrel nuts and HDPE spacers for the wheel guards, these held up sooo much better than the puny aluminium standoffs in v3

But in my testing, this had way more power and was going to tear the D-hole into a… well hole I guess. So I tried a series of 3D printed gears, see the video for the full run down on that, the summary was the gear teeth were too small and shatterable whatever the material (PLA, TPU, Taulman 910, ABS…) so wouldn’t really work without a pretty major redesign, which I at this point did not have the time for!

Using 3mm hardox forks and claws, now reused from both v2 and v3, one here a bit bent from Stratus but still very usable!

So day of the flight to Burgh (cutting it very fine…) taking influence from the excellent Tosser electric flipper by THE @Gareth, I went for as chonky as I could fit 20mm wide HDPE CNC’d gears

And these worked well enough in a quick test, no teeth exploding, no crunching noises. Still had to be careful to not stall out too much! So finished bot, ready to head to Battle in the Burgh!

Full run down of fights in the video above, but due to some good yeeting and quite a nice draw managed to somehow come out on top?!

with an all control bot final with the excellent Boom Zoom getting some air miles!

Gonna whack this weapon motor on :lobster: lob-ster next with a lot of HDPE gears, because chonk plastic gears are fun. GG, thanks for reading. See y’all in 2024. :crab:


man that thing is super impressive!
and congrats on the trophy :slight_smile:

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wonder how much it would help with the tipping forward if you moved the weapon assembly right to back

good shout, I used to have the pivot point further back on v3, but yeah could try having weapon the motor at the back.

just thinking the likes of Nyx has it much more reward and you look to have plenty of space plus could also move the CoM closer to middle

Hi Joe. Well done on the win!

How did the HDPE spur gears hold up in the end post event? Also are they MOD2 or 3?

Hey Sam, thanks!

They’re just under MOD3 (MOD2.9 or something so they’d not hit the baseplate on the last minute redesign) They held up really well for 7 fights worth - a couple teeth have started to bend along about half the length presumably from when the arm is stalling on the chassis, but it’s still would be usable as is. I did make a spare pair of gears though just in case!

I think the 20mm thickness really helped, particularly with the hub being pocketed within the input gear


Very impressive machine! Echoing Mark, moving the pivot further back should help with the face planting - it’s something that Déjà Two and my ant grab-and-lift used to do a lot!

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Grab Crab has been revived for Rapture this weekend!

Have just given it a quick once over from Burgh and made some chonky TPU toes for my 3 spinner fights!

Thanks as always to the amazing @Liquid for his great prints :slight_smile: Lob-ster’s coming along for whiteboards or as crab spares if it gets pasted!


Rapture was a spicy weekend! Crab fought 5 spinners in 6 fights and managed to go 4-2, getting knocked in the quarter finals by judges decision to a very well driven Boom Zoom, I’m happy with how it went.

Had to pillage Lob-ster for parts after the weapon motor sheared it’s shaft clean off! Thanks to all involved in organising, it was a great if very tiring event! :slight_smile:

Couple pics of crab doing the thing!

Thanks Stuart Camp for the bangin photos as always! :crab: