Team Astro Build Log (Cheese bots)

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Re: Team Astro Build Log (Cheese bots)

Post by Kyro »

with nothing attached, the be 1806 is pretty quiet if its well balanced... add a bar/disk and you will get that hum as it cuts through the air
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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Joined: Fri Jan 10, 2020 8:18 pm

Re: Team Astro Build Log (Cheese bots)

Post by JoeHLloyd »

I got a test chassis printed in PLA and boy am I glad I did - it has thrown up numerous issues. In general I think I've pushed to keep it as compact as possible and unfortunately I'm now paying the price.

  • The weapon does not appear to sit centrally. I'll bolt everything down to confirm but I think some dimension has not beem modelled correctly. I'll be getting out the verniers to confirm where I've gone wrong.
  • The drive motor holes are too tight. I can't really file them out and I can't exert much force on the motors because I'll snap the ESCs off. Mounting the motors securely whilst being space-efficient is a big problem. I think I'll just expand the holes by 0.25mm and hope it's still reasonably snug. Alternatively I could have detachable wheelguards, which would make installing the wheels/motors and filing the holes to fit a lot easier. If I was to do that I'd want them out of polycarb, and I'm not sure I actually can spare an extra 1.5mm either side because the design was bang on the cube limit.
  • I forgot to model the ESCs like a muppet, and they protrude into the cover. I'll have to raise the cover height. Not too big an issue, unless it goes above the heigh of the wheels in which case inverted manouvering will be impacted, and I'll have to get use bigger wheels. Not necessarily a bad idea as I was concerned about the amount of tyre contact the small wheels would have whilst inverted already.
  • The RX won't fit the bay. The given dimensions online were not quite accurate. This should be an easy fix - I've got 3-4mm I can increase the bay heighy by so I'll do that.
  • The weapon ESC wires/solder prevent it from fitting the bay, and may also clash with the right drive motor. I can re-solder all the big wires to angle into the ESC rather than away from it which may solve this issue, but it may make more sense to move the ESC to sit on top of the battery. There's plenty of space there. But it does mean running the motor wires through the congested wiring passage at the back.
  • The left drive motor clashes against the weapon support mount, preventing install. I can probably cut out the necessary section of this and still have it work OK.
  • There is a big clash of wiring at the back of the RX bay against the right drive motor ESC. This might be solved with a higher cover which is already necessary. If it isn't then I'm not sure what to do. Potentially swap the rx into the empty ESC bay if I move that to the battery area.
A lot of these problems would go away if I made the chassis deeper. Without wheels it's only 60mm deep. I really don't want to make it deeper because that means it will be heavier (and I don't know if I have the spare weight yet) and it will move the wheels further away from the weapon axis which will make it harder to control.

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Joined: Fri Jan 10, 2020 8:18 pm

Re: Team Astro Build Log (Cheese bots)

Post by JoeHLloyd »

I'm having to make minor changes to pretty much every part of the bot. It'll be another week at least before I'm ready to print the next test chassis.

What's happening:
I'm going with 30mm wheels over the 25mm I originally intended. This unlocks quite a few benefits.

1. I get 2.5mm more space at back of the robot to expand without changing the wheelbase. This 2.5mm, couple with a curved tunnel, has added about 50% more space to the congested cable tunnel between left and right, alleviating that problem.

2. I get better tyre contact if the bot is inverted

3. I can still get tyre contact when inverted above where the drive motor ESCs protrude.

4. The weapon support will now rotate out without hitting the back of the bot, which means I can remove the slanted support at the base, which means the drive motor will install more easily.

I'm also changing the drive motor securing method. I'll use 3 sides of a rectangle to secure the motor and drop it in vertically through the open side, then cinch it down with tiny cable ties. I wanted to avoid them if possible but unfortunately they are the most space efficient solution that will allow me to install the motor without accidentally breaking it.

I also discovered the DYS 1806 model was too short by 1.5mm. I have no idea why. Be warned the rest of you.

Also, this is the last time I do a bot in sketchup. Having to manually mirror every change from one side to the other is a PITA.

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