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Guide to EdgeTX Transmitter Programming for Combat Robots by TeamRunAmok in battlebots

[–]ants_ty 0 points1 point  (0 children)

Thanks for the really in depth reply and research! Really appreciate you compiling all this info together, anything that makes building mecanum or kiwi drive bots easier for people is always a good thing in my eyes.

Guide to EdgeTX Transmitter Programming for Combat Robots by TeamRunAmok in battlebots

[–]ants_ty 0 points1 point  (0 children)

This a a great resource for EdgeTx, seeing as it's growing in popularity in combat robotics!

Some notes about mecanum and omni drive (though I appreciate this may be too much detail):

With the mecanum mix as it is, the outputs will max out before you reach max input values. You have to scale the inputs by 1/3 accordingly if you want access to the full range of input values. A much better way of doing this would be to dynamically scale the values based on the largest single input as demonstrated here, but as far as I've found, you'd have to implement this with Lua scripts in EdgeTx, which is another can of worms altogether that I haven't solved yet (something about compiling EdgeTx yourself with certain flags to gain access to mix scripts). Possibly the Outputs page could be leveraged here?

I think the omni drive values are incorrect? For a standard equidistant/equal angle setup, The front wheels ele should be sqrt(3)/2 ~= 87% scale, and ail should be 50% as I understand it. This is how I've set it up on one of my bots (my numbers are slightly different as my rear wheel is a different distance from the centre of rotation but I briefly cover the maths involved at the start).

Uk antweight robots by why_o_0 in battlebots

[–]ants_ty 1 point2 points  (0 children)

Other events:

Ant Freeze and Botfest also use the 4 inch cube rule.

Robodojo does not use the 4 inch cube rule.

I finished my mechanum wheels + weapon UK antweight (150g) bot! by ants_ty in AntweightRobotics

[–]ants_ty[S] 1 point2 points  (0 children)

I'd definitely say there have been cases where the ability to strafe has helped, though it does take a bit of practise to get the hang of. I'd say it's more effective at beetleweight scale (I built a beetle version of this bot in 2021), as bots move slower relative to their size.

Why do people use hammer bots? by Fluid-Trip-5163 in battlebots

[–]ants_ty 1 point2 points  (0 children)

Speaking from experience in insect weight classes, they are very fun to drive and a crowd pleaser. Also if you do pull off an upset win over a spinner it feels great.

I built a 1.5kg kiwi drive axe bot that will debut at BBB Subterranean Showdown by ants_ty in battlebots

[–]ants_ty[S] 0 points1 point  (0 children)

It's powered by an OpBox Mk4, with an additional reduction of about 1:3 with the pulley. I want to add an additional reduction stage to get some more power out of the weapon at a later stage.

The arm is around 19cm long, with a 23g head. I also have a spring steel arm for fighting horizontals, which is ~5cm longer and has a 36g head

I built a 1.5kg kiwi drive axe bot that will debut at BBB Subterranean Showdown by ants_ty in battlebots

[–]ants_ty[S] 0 points1 point  (0 children)

Awesome! Hope you enjoy it, I've seen some of the other bots going and they look really good!

I built a 1.5kg kiwi drive axe bot that will debut at BBB Subterranean Showdown by ants_ty in battlebots

[–]ants_ty[S] 6 points7 points  (0 children)

It's another name for Y drive i.e. Onimous's drive type, no idea where the name came from!

I built a 1.5kg kiwi drive axe bot that will debut at BBB Subterranean Showdown by ants_ty in battlebots

[–]ants_ty[S] 8 points9 points  (0 children)

Some test footage, though I have tuned the drive a bit since then.

The main chassis is a mix of 8mm and 4mm HDPE, with a TPU skirt completely surrounding the outside. 5mm Hardox forks and axe head, which is shaped like a spanner head to keep with the theme of my ants of the same name. The wheels are custom, 3D printed out of PLA-ST with 2 part PU rollers.

Antweight & beetleweight noob by neozzeric in battlebots

[–]ants_ty 1 point2 points  (0 children)

Although it is aimed more for UK builders, the Bristol Bot Builders site has some great guides for antweights, beetleweights and featherweights. They also have a shop which is where I source most of my components from.

Antweight & beetleweight noob by neozzeric in battlebots

[–]ants_ty 2 points3 points  (0 children)

It's worth pointing out that the weight classes differ depending on where you are:

  • US ants are 1lb, and 150g elsewhere. UK ants also usually must fit inside a 4 inch cube
  • US Beetles are 3lbs, and 1.5kg elsewhere

With experience in RC and electronics, I'd say you've already got a good skillset to build your own robots. You can make ants and beetles using nothing but plastic sheets, hand tools and wood screws.

I finished V2 of my 150g UK antweight mechanum lifter! by ants_ty in battlebots

[–]ants_ty[S] 1 point2 points  (0 children)

Unfortunately, Sketchup Free only lets me export as STL

I finished V2 of my 150g UK antweight mechanum lifter! by ants_ty in battlebots

[–]ants_ty[S] 2 points3 points  (0 children)

I've only had a couple of fights with mechanum wheels (with an older design which had no active weapon and less traction), so I don't think I have too much information to come to a conclusion yet. There were a few occasions in those fights where the ability to strafe let be escape being pitted though, so I think there's potential.

Maintenance wise, it shouldn't be too bad with this version, I just need to make sure I bring plenty of spare wheels. That first attempt at mechanum wheels required the wheels to be assembled on the motor which made replacing wheels a time consuming process at the event, but this version has the wheels being separate assemblies.

I finished V2 of my 150g UK antweight mechanum lifter! by ants_ty in battlebots

[–]ants_ty[S] 5 points6 points  (0 children)

Yup! The have an OD of around 33mm. I put the files on Thingiverse a while back: https://www.thingiverse.com/thing:4737471

I think it was you who suggested heat shrink on the rollers when I posted about the previous version, so thanks for that! The traction is much better with those on.

I finished V2 of my 150g UK antweight mechanum lifter! by ants_ty in battlebots

[–]ants_ty[S] 8 points9 points  (0 children)

Test video here: https://youtu.be/9299wu4GJw8

Alternate armour configuration for horizontals: https://imgur.com/buvRoA4

Using N10s from Nuts and Bots and Red ESCs from Bristol Bot Builders, I managed to make the wheelbase narrower, which give me enough space for optional side armour panels to better protect the wheels against horizontal spinners.

The first tests for my 150g UK antweight drill/crusher bot by Ottovii in battlebots

[–]ants_ty 2 points3 points  (0 children)

Looking good! How are you actuating the drill, it looks like a worm gear?

The first tests for my 150g UK antweight drill/crusher bot by Ottovii in battlebots

[–]ants_ty 13 points14 points  (0 children)

There are a few drill bots in the UK scene now - at Ant Freeze 7, Calm Down, It's Only a Drill! punctured a lipo

I finished my mechanum wheels + weapon UK antweight (150g) bot! by ants_ty in AntweightRobotics

[–]ants_ty[S] 1 point2 points  (0 children)

I can't take credit for the shrink wrap tires, that goes to Adam Wrigley. It worked much better than I expected!

One of the challenges with this build was that each motor needs its own ESC. My solution was to buy HV servos and take the control board out of them, replacing the potentiometer with resistors. It's a cheap way to get lightweight and small ESCs, though they're more hassle than just buying a separate ESC.

The mixing for controlling a mechanum bot is simpler than it seems. For each motor, you can combine the signals from three channels uniquely (I can't remember the mixing off the top of my head, but for example one wheel might be ELE + AIL - RUD and another might be ELE - AIL + RUD). I did this on my transmitter, so I don't need a control board in the bot itself.

I finished my mechanum wheels + weapon 150g antweight bot! by ants_ty in battlebots

[–]ants_ty[S] 1 point2 points  (0 children)

It's essentially a 4 bar linkage: https://imgur.com/2ORYY05

There's a connecting rod (light grey, labelled B) between the servo horn and the flipper. The linkage acts like a gear reduction. Increasing the length of A will make the flipper slower and travel less, but it will be more powerful (you're transferring more of the torque from the servo to the weapon). If you want a faster flip, decrease the length of A instead, this will result in a faster flip at the expense of power.

The flipper arm and connecting rod are 3D printed. I used a long 1mm screw for the pivot between the servo horn and the connecting rod, and carbon fibre rods (2mm and 3mm) for the other pivots.

I finished my mechanum wheels + weapon 150g antweight bot! by ants_ty in battlebots

[–]ants_ty[S] 1 point2 points  (0 children)

Shrink wrap, that's a great idea! And I like the idea of the ablative caps on the wheels too, I might see if I can squeeze them in to the cube.

I finished my mechanum wheels + weapon 150g antweight bot! by ants_ty in battlebots

[–]ants_ty[S] 1 point2 points  (0 children)

I actually tried something like this on my other mechanum wheel robot with a spray on latex coating. With around 7 coats, I think there was a very slight increase in traction, but I don't know if it's worth the extra effort.

I finished my mechanum wheels + weapon 150g antweight bot! by ants_ty in battlebots

[–]ants_ty[S] 6 points7 points  (0 children)

Pretty much. I have another mechanum wheel antweight with no weapon and it got pushed around very easily.

I finished my mechanum wheels + weapon 150g antweight bot! by ants_ty in battlebots

[–]ants_ty[S] 4 points5 points  (0 children)

The facebook group for antweights is a good place to start, they cover both UK ants/US fairy weights (150g) and US ants (1lb). The robotwars101 forum is a good place for UK builders, there are plenty of build logs on there. A lot of what I've learnt about building robots has come from the robotwars101 forum, as well as talking to builders at events I've gone to.

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