Team Darklight - Broadax 2 (Featherweight Axe/Hammer)

[PaulusSmallus]

It would be an interesting project to turn off the motor when it hits the end stop. Not sure how useful it would be though.
Electric actuators use switches and diodes to limit travel, but that will only work with DC motors.
It should be possible to have some micro switches (or similar) to detect when the axe is at its end-stop, then use a microprocessor to modify the signal from the transmitter to the axe motor to stop it moving.

This might just be another way for the robot to fail so might not be worth it, but it would be interesting.

[qbnut]

I thought about this when I built previous robots. I think simplicity is the key, the less there is to go wrong the better generally!

[Coolspeedbot]

Those HDPE hubs for your wheels, did you make those yourself or did you get them done else where? I'm asking as I'm thinking of making some wheels like that for my FW.

[qbnut]

These were CAD designed by me but I didn't print or make them myself, I got them water jet cut as part of a larger parts order.

I will be making a V2 hub for these that will be 3d printed, that will be lighter and more well designed to mould the rubber around

[Coolspeedbot]

These were CAD designed by me but I didn't print or make them myself, I got them water jet cut as part of a larger parts order.

I will be making a V2 hub for these that will be 3d printed, that will be lighter and more well designed to mould the rubber around

Ah I see, totally forgot water jet cutting was a thing . Thanks

[qbnut]

Preparing for Extreme Robots Cheltenham

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Many, many tweaks, changes and updates have been made to make it (hopefully) perform better than it did at KOB UK.

The lids would hit the front brackets if the axe hit a target hard enough, given the flex in the armour. Cropped the corners to provide much more flexing space

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This was the motor that came loose at KOB UK. The motor is fine, the leads not so much. The red lead had frayed, so soldered to repair it rather than replacing, then resleeved all the leads

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These side brackets hold the armour on, and would flex into the lid on a hard axe swing when it missed the target, causing the lids to be pushed off, the #1 issue Broadax 2 has so far had. Cut these corners off to allow for much more flexing space before they hit the lids

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The first bracket iteration just wasn't up to the job. New mounts made from 10mm bar threaded as needed and bolted into the mid section should see the lids stay on properly

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New rubber cast onto the wheel hubs. 60 shore has great grip but poor durability. We have a fallback to the 75 shore blue rubber castors if these wear out prematurely

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3d printed parts! We've added motor guards for the drive outrunners and a new mount for the link

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I have also rewired Broadax 2 from scratch. This eliminates the dual voltage setup, so Broadax 2 now runs at a fixed voltage for both drive and weapon, simplifying things. For Cheltenham it will run at 4s only, as I have run out of time to source new batteries that fit the space now available post new link holder and guards being added. Two of the original 4s 2200 MaH packs it uses, that allowed it to run at 8s for the axe, will no longer fit the new space unfortunately.

I have however now split the link so that the weapon has a separate one, as advised by EOs, as it means they can test all but the weapon in the pits, saving time.

Left is the new loom, right the one used at KOB UK

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[Eidg]

Looks rock solid.
When does the next uk kob event taking place?

[qbnut]

Looks rock solid.
When does the next uk kob event taking place?

It's not been announced yet, but probably August next year

[Eidg]

Thank you for your answer.

[qbnut]

Post Extreme Robots Cheltenham

The Cheltenham event was really good fun, and was a high for Broadax 2, followed by a low.

So in melee 1 of the Saturday session, Broadax 2 was declared the winner! This was a fantastic result, the bot ran exactly like it was supposed to, the drive was very on-point and it racked up the points! I have setup dual rates for the drive speed, at 60% and 100% setting - however, I ran this at 100% all the time given how large the arena at XR is.

Coming out of it though, as suspected, the cast rubber on the wheels had perished. It turns out it ate its own tread, such was the drive torque:

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Back to the blue castors it started life with for the following fights

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Here's where things started to go south. During melee 2 on Saturday, it was clear that the Axe was not firing every time, eventually it packed up altogether. But worse was to come, as with a hit to the rear of the bot, the rear lid bent inwards, and with it, one drive ESC bent in the same way, writing it off.

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This happened in a corner of the arena that I couldn't see, and it happens off-screen on all the current videos I can find, but from what most other roboteers have told me, this was the work of Dave Westons Satanix - it might be an ageing bot, but it's still powerful!

Once I got the bot out of the arena to inspect the damage, it was clear that I wouldn't be going back in this weekend To change the Axe motor requires a 70% percent strip down, something that I simply didn't have the time to do. Whilst I currently live a short distance from Cheltenham, I really didn't want to pull a late nighter to fix it, and to do so in the pits on Sunday would mean I would miss the first melee anyway, leaving only one remaining fight for the whole event.

So at that point, I called it quits, and just became a pseudo team mate to any teams that needed a spare pair of hands.

---

This weekend, I did a teardown, so the bot is a box of bits again. This was to get the axe motor out for a closer look.

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The axe motor can is basically the wrong shape and has seized solid; when the axe was hit, the can couldn't spin which meant the only way to go was to shear the shaft away from the mounting to the can.

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No magnets were harmed, but the can is no longer round, so it does not spin around the stator. You can't really fix the warping, so this motor is essentially destined for the bin.

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With that, Broadax 2 is now shelved until sometime next year, whilst I work on some new bots for the 2019 season. It can definitely be fixed, and may well see a live show or two again in the future.