Team Darklight - Sawcerer (Featherweight overhead saw)

It seems that I've built one too many Featherweights over the last two years I've been building; now in to build number four, and this time, something that's not an axe, but something that's going to be entirely a lot more work, but entirely more effective in full combat (I hope!)

Introducing... Sawcerer! This is an overhead saw style bot, notably similar to the US robot MegatRON from which it takes a large influence.

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The chassis of the bot is all new, but I have designed it around recycling parts from the spares boxes of both Broadax and Broadax 2. As a result, its designed around the same 4248-based brushless drive, powered entirely by VESC 4.12 and/or FOCBOX ESCs as I have both to hand. Given how well this drive system worked in Broadax 2, I've taken over the exact same system with the 6:1 MOD1 single-stage gearboxes as well. This time around though will be aiming for 5s for the battery sizing to give the drive some extra kick.

The wheels are 125mm unlike the 80mm ones in both Broadax builds and Battleaxe. I've ordered some 'standard' castors to build around, though eventually, these will be on custom hubs and cast wheels, much like Broadax 2. This will be done after it's working though so as to not give myself too much to do at once to get it rolling.

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The weapon is intended to be powered by a spare 5060 I have lying around that was for Broadax, though weighing up swapping that for a sensored 50xx motor given I'm using VESCs, thus I have the option!

Finally, the arm is to be powered by one of the converted-to-brushless Gimson gearboxes that were used for drive in Broadax 1, then into a MOD2 stage to give a total 65:1 ratio. I have however made provision in the internal sizing if I need to swap this out for a P60 or something else later, depending on how well this works.

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The wedge design is designed to be interchangeable, but for the initial build will come in one style, the dustpan with forks design. I have however designed the forks to be bolt-in such that I can change the configuration as needed from short to long to none if required.

I will need to have custom pulleys made for the belting from the weapon motor, which sits inside the chassis, onto the arm shaft, then from the arm to the saw shaft, as nothing I could find off-the-shelf will meet exactly what I need here. Essentially I don't want to expose either the arm or weapon motors to the outside to shield from damage. Through the wonders of 3d printing, I have started to make prototypes to check sizing on everything, which I will have to eventually machine for the finished article.

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Further parts are arriving shortly, hopefully over the Christmas break it can be fully assembled at least in prototype, ready for next years robot combat season.

Looks Fantastic! A lot of builders have been considering a sawbot (me included) due to Battlebots success. Id be greatly interested to see how this one comes out and performs.

Loving the sound of this - that cad is soo nice! :p

Today's progress: bolted the chassis together, and checked everything for fit. Still a long list of things to do, including wedding the wedge parts together, turning down and weight saving the gear hubs, and making the custom pulleys.

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In pretend bot form, to check everything fits.

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Chassis half assembled. It's missing some parts in this photo, there's a cross part to hold the two bulkheads for the saw together that's not attached

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The good news is, it's in weight even before the weight saving to the gears! So may use that allowance for better armour or stronger arms.

Nice Robot i am looking forward to see it fighting.

Sawcerer is looking awesome, definitely going to be a fun one to fight! It's always impressive how quick your builds come together too.

Limited progress today, as still waiting for parts after the Christmas break.

I did however get the drive bolted together and the arm gearbox partially done for a bit of testing:

https://youtu.be/05eqCRWL8Qw

Which gear sice are you using? And on which gear ratio?

Quote:

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Originally Posted by Eidg

Which gear sice are you using? And on which gear ratio?

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The arm is two-stage 13:1, 5:1 MOD2, giving 65:1 total.

Progress is being made, but still plenty to do! The pulleys are off being machined, so meanwhile it's propped together with 3D printed PLA prototypes, which I printed to check fit and dimensions.

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Looks great! The spiky/starry details are really nice.

I haven’t been keeping this up to date with progress. Progress is, it’s pretty much finished and ready to run!

There’s a few 3D printed bits and bobs used to hold links and internal bits, etc, that I want to reprint, but I could throw it in the arena now and it would probably be fine.

Well, I've not kept this up to date at all, as it's finished, competed at Robodojo, and now being redesigned for mk.2 :)

Here's a playlist of how it did at Robodojo Round 4, July 2019: https://www.youtube.com/playlist?lis...jgwdDOqnUO1cBS

Was great to see this in the flesh (well metal) at Robodojo. Hope the repairs weren't too much work! Looked like you took a bit of a hammering against Drumroll (or whatever Drumroll was actually called).

What's changing for Mk II?

"I Can't Believe It's Not Drumroll"

Drumroll 2: The Druming

Quote:

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Originally Posted by McMullet

What's changing for Mk II?

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A long, long list:

• The drive
  
  • It's way too fast, even rate limited to 40% as it was at 'dojo
  • The ground clearance is dreadful, which is why I got beached against Telekinesis and the fight had to separate us and restart. It looked fine in CAD...
  • Blue castor wheels provide next to no grip on the 'dojo floor. Blue castors seem great in principle, but they aren't, and it's clear with that much power in the drive, all it did was slide and drift. The rest of my featherweight robot fleet will be switched to an alternative tread system as well.
  • The motors were very, very toasty after every fight, so needs some better way to dissipate the heat
  • It needs to be protected in a way that that wheels can't simply be sheared off due to the kinds of robots we have on the UK featherweight circuit right now.
  
  
• The weapon
  
  • I got the pulley distances calculated for a belt size that I couldn't buy when I came to actually purchase parts. I therefore added a belt tensioner, which didn't help and just got incredibly hot in the fights. Lesson learned, purchase the pulleys and belts first and design around them, not the other way round.
  • There's a serious lack of torque in the saw. It's fine for HDPE, but little else. And everybody, knowing there's now a saw on the scene, had alternative lid configurations made of Hardox. So it needs to be able to damage those.
  • I added a slip into one of the pulleys but all that did was smoke belts rather than cut in (see if you can spot it smoking whilst I'm in one of the corners in the Telekinesis fight)
  • The saw blade I chose to use was crap for Aluminium and Steel. It was a general purpose blade and frankly, a bit rubbish.
  
  
• The arm
  
  • Is not Drumroll / Revolver proof
  • Is far, far too weedy. It needs to be able to take a hit like that and maybe not be perfect afterwards, but at least still work to the end of the fight
  • Has that big MOD2 gear in it that makes up for 1.5kg of the total weight. It needs weight saving far, far more
  
  
• The pulley system
  
  • Don't use bushings for this application. Because they were pulled both towards the weapon motor and the saw at two angles, all that did was cause extra friction. Bearings are the way to go, so new pulleys needed

There's more, but that's the main crux of it

If you choose a higher gear ratio for the drivetrain, the bot will be slower and the motors might run cooler.