Fitting your Ant in the 4" cube

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jes
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Fitting your Ant in the 4" cube

Post by jes »

Hello. I've never built a combat robot before, but I'm about ready to start designing and I have done some thinking about the 4" cube that might be useful to others.

If you assume your robot wants to be primarily wide, but also long, and not very tall, then this diagram shows what I think is the best way to think of the 4" cube (black is the cross-section of the cube; red is the cross-section of the robot).

Image

We want to fit the robot at a perfect 45 degrees across the diagonal of the cube to maximise its width (shown here as the x axis). Its length (z axis, not pictured) is exactly 4". The height of the main body of the robot (the central rectangle) dictates the maximum possible width of the main body, and then on each side, and on the top, we also have a triangular cross-section in which we can make whatever protrusions we like. (Technically you could also have a protrusion on the bottom, but probably you need your wheels to touch the floor).

The diagonal of a 4" square is sqrt(2)*4" = 143.68mm. At the centre line of the robot, you can have 143.68mm of width. For every 1mm you go above/below that, you need to go 1mm inwards (on each side). So for example if the robot has a rectangular body that is 50mm tall, then that is 25mm above/below the centre line, so we need to go in 25mm on each side. So the maximum width of a 50mm-tall rectangular robot is 93.68mm.

You don't need to include the wheels in the calculation of the height, provided they are sufficiently shallow and sufficiently far away from the outside edge that they lie within the allowable-protrustion region.

Obviously if you are more keen to have a long robot than a wide one, you can just mentally swap width and length and the same maths applies.

Hope that is helpful to someone.

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Kyro
Posts: 388
Joined: Fri Jan 18, 2019 12:36 am

Re: Fitting your Ant in the 4" cube

Post by Kyro »

i mention this in my video regarding the 4 inch cube rule...

https://youtu.be/GRSzb-Lg9Uw

this is to hopefully clear up any confusion, and to show the different ways i fit some of my bots in the cube...

a bit nostalgic looking at some of these robots now...
only 1 remains the same
Team Rocket
Esper(4wd flipper)
Mantis (4wd grab 'n' lift)
Dominus (Vert SPINNAAH)
Breakout(modular cluster)
Remembering Rex (antweight cassius)
Fennec (4wd flea) former world champion

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LimaHotel
Posts: 249
Joined: Fri Mar 16, 2018 10:30 am
Location: Mold / Chester

Re: Fitting your Ant in the 4" cube

Post by LimaHotel »

Or you build your bot entirely by eye, then hope! Well, then be disappointed! But have enough leeway to make some modifications!
Same's true for weight!
Jiggy Sawdust
Jammin' Good with Weird and Flippy
The Pushbot from Mars

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