Tantibus: The Swiss Army Feather

[Danny B]

So I decided to shelve my previous idea of a FW spinner in favour of something with more versatility, that I can use at any event. So I've already gotten started on Tantibus, and here's what I've established up to this point.

Chassis: HDPE (8mm baseplate, 20mm bulkheads running lengthways)
Armour: 6mm aluminium plate
Drivetrain: 2 x 775 motors run through 13.7:1 Gimson gearboxes (obtained)
Battery: 4000mAh 5s LiPo (drive), 3000mAh 6s LiPo (weapon)

The bot will have 3 interchangeable weapons. For now I'm just going with an axe, run from a 300w scooter motor (already obtained). But once I've had the opportunity to test the bot in combat I'll be expanding the arsenal to include a 180 degree lifting arm and a 270mm, 2.5kg vertical disc. Total estimated weight in the heaviest setup comes to 12.9 kg.

I've taken the liberty of throwing together a rough but size-accurate cardboard replica of the chassis, as you can see below. The shape is rather reminiscent of Blacksmith from Battlebots, especially with the axe.

The plan is quite ambitious, but I want to push myself to make something better than just a generic lifter.

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[Maxamuslead]

why are you planning to run with a 2 battery step up ? As if you got 18v 775 you could run a single 6s battery thus saving weight and removing points of failure ?

[daveimi]

Are we to start putting our FW build threads in the FW section now? Genuine question as the Build Thread section seems mostly heavies etc.

[RogueTwoRobots]

Running two separate packs for drive and weapon is a common approach, but usually for larger voltage differences. Running a 5s for drive and 6s for weapon seems a little pointless (5s fully charged is 21V). Running on a single 6s pack would be more logical and just put dual rates on if you want to limit the voltage on the drive motors.

If you do go with the 2-pack route, 4000mAh is overkill for a drive pack. 1600-2000mAh would be a better size and still leave you enough in reserve. The weight saved could then go into your weapon pack (maybe take that up to 4Ah) to give you plenty of juice when running a spinner. As an example, Onyx uses a 300W scooter motor for its axe and two 550 drills for drive, and it never struggles with a 2200mAh pack for the whole robot.

[Maxamuslead]

Are we to start putting our FW build threads in the FW section now? Genuine question as the Build Thread section seems mostly heavies etc.

idn tbh i did mine by mistake but no one has complained. if your going to start one stick in in build logs as technically is still a "build Log"!

[Danny B]

Running two separate packs for drive and weapon is a common approach, but usually for larger voltage differences. Running a 5s for drive and 6s for weapon seems a little pointless (5s fully charged is 21V). Running on a single 6s pack would be more logical and just put dual rates on if you want to limit the voltage on the drive motors.

Point taken, I didn't consider dual rates. I've just tracked down a 5000mah 6s that should be plenty for any drive/weapon combo, and still weight 400g less than the 2 separate batteries.

By the way, how long is the axe on Onyx? Mine would be 35cm from axle to tip, geared 5:1 ratio, and I just want to be sure whether that's adequate for self-righting.

[Danny B]

UPDATE

I've started on the axe, and progress is pretty good. Turns out Hardox 500 isn't so bad to work with so long as you have an angle grinder and a pillar drill with some cobalt bits.
Anyway, I've made the shaft and bolted on the head (see below). The look reminds me of Behemoth's old axe from back in the day. Total weight is a nice meaty 1.2kg.
I've also acquired all of my HDPE for the chassis, all I need is to find someone with a table saw to cut it to shape. All being well, I should have an assembled chassis and working weapon within the next month!

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[Danny B]

UPDATE

The basic chassis is now together (see below), and actually turned out a couple hundred grams lighter than expected!

Progress hasn't been quite as fast as I'd hoped due to other commitments, but over the next week I'll be ordering most of the mechanical parts I need to get the axe working (axle, sprocket, chain etc.) Electric-wise, ordered a 30a ESC from Ranglebox to run the scooter motor last week, just awaiting news on that and that'll be the last piece of the circuit

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[Maxamuslead]

to give you a hand, here is the motor sprocket which is t8f which its keyed so it goes on the scooter motors without the need to mod anything.
https://www.ebay.co.uk/itm/Electric-...item1a2a5ee73b

8mm chain is the go to so here is where i got a 8mm sprocket

http://www.beltingonline.com/roller-...atewheels-972/


Side note: i don't think a 30a botbitz esc will be enough, originally i was going to use one and it does work but reading other build logs I swapped it for a 85a.

[Danny B]

Question regarding aluminium. In terms of both strength and weldability, which is preferable: 5083 O or 6082 T6?

[Danny B]

UPDATE

The axe works! So far I've only tested it at half voltage since I only had a 12v lying around, but it should have loads of power once I get hold of a 6s lipo.

[Danny B]

Drive and weapon controls are now fully installed and operational! Even at just 50% voltage it can still self-right, and it made mincemeat out of an old heater I had lying about (see below)
Only three major things left to take care of now:
- Outer shell
- Safety link/locking bar
- More powerful battery

https://www.youtube.com/watch?v=GtgBGzNP2kA

[Outlaw]

Very snappy self righting, and I feel sorry for that old heater, haha.

Looking awesome.

[sean retro]

What did that heater ever do to you?

At lest the axe works.

[qbnut]

Axes are cool again glad to see I'm not the only one!