Body Design and Body Mounts

The three of us have spent many hours this week planing and discussing the theme for our robot, in fact we spent most of yesterday evening discussing it.

We've taken into account the disaster movie theme for PiWars 2020 and we've tried very hard to not take what we feel are the obvious choices.

If you're reading this expecting us to reveal exactly what we've decided, then I'm sorry but you're going to be disappointed, we're not revealing too many details on that yet, at least not until we know we have a confirmed place in the competition. 

What we will say is, it should be very much in keeping with the disaster movie theme and it's already been printed from a heavily modified 3D model found on thingiverse.com

Today, in addition to printing parts for the body itself, we've been playing around with where the body mounts and how all the other elements fit around it. 

Below is a photo of the mock up body mounts, which work for now, but still need quite a bit more adjustment before we make the final versions (note the scrap piece of acrylic being used as part of the body top mount). 

In this photo it looks a lot more top heavy than it really is, most of the weight is low down, so being a little taller than our previous robots has no negative effect on the handling, in fact I believe the COG is even lower than our 2019 robot.

The plan for tomorrow is code, code and even more code. We are pretty much starting from scratch with our code for 2020, in my opinion sometimes it's better to start with a totally clean slate than to re-hash and refresh old code.

"Any code of your own that you haven't looked at for six or more months might as well have been written by someone else." — Eagleson's law

It's alive, again.

Today we've been cutting, splicing and soldering parts of the old wiring loom, all with the intention of powering up the robot and to get it moving again.

We're going to build a brand new wiring loom once we've got everything in place and once we've fully decided on what power distribution boards we're going to use. I'm toying with the idea of designing our own PCB and getting a small batch made up by JLC PCB, but that's not very high on the list of priorities at the moment and I doubt this is something I'll pursue much further until we know whether or not we have a place in the competition (fingers crossed we get a place from the start this time). 

Anyway, here's the proof that we managed to successfully power up the robot via our makeshift loom, it's not pretty but it's more than good enough for the time being. 

What you probably can't see in this photo is the redesigned the battery box, this was done to enable the battery to be held securely in the centre of the robot where it's much less likely to get damaged (making sure we don't break *Rule zero) and to make it quick and easy to swap out the battery should it need replacing with a fully charged one in a hurry. 

Also the housing for the Raspberry Pi has been redesigned to make it stronger and we've moved a few things around to enable the Pi to sit centrally on the top plate.

 

*don't be on fire :)

 

 

Final locations of the boards, Maybe

I think we're nearly there with the mounting locations for each of the boards that we plan to use, all apart from the power distribution board, which we're looking at designing ourselves and getting a company like JLCPCB to make a small batch of them, watch this space. 

But back to the boards that we have already, it's been like one of those plastic picture puzzles where you slide each tile into the empty space in order to get each tile in the correct location to reveal your pretty picture. You put this one here, no, that wont work because of this one here and so on and so on.

However, I think we've pretty much got it now and we should soon be able to make a new top plate, which will tidy things up a lot.

Oh, and we finished designing and printing the mount/case for the Raspberry Pi 3 A+. It is now well protected, as are the GPIO pins, so the risk of accidentally shorting anything out is very low.

 

Build, Unbuild, Rebuild, Repeat

It's been too long since our last post, work and general life stuff has been demanding the lion's share of our time. 

But we have been doing robotics in-between, just not had the time to post here, anyway, enough of the waffle. 

If you've ever built a robot for Pi Wars then I am sure you'll be familiar with this scenario. You plan, measure at least once :), build, then change plans or location of a few components and before you know it you're back to a bench full of your robot in 100's of pieces. Well, that's where we've been for the past week or so. 

But all of this Build, Unbuild, Rebuild, Repeat has still been quite productive, even though you'd be forgiven for not thinking so if you saw the current state of the robot (below).

What isn't clearly visible here is the lower plate that supports the top section of the steering gears has been redesigned to tighten up the steering even further and to enable the entire battery tray to be removed and replaced very quickly. Although this of course means a redesign of the battery tray, but it's all in hand. 

The top plate is still a prototype one, hence the lovely collection of seemingly random holes and the fact that it's not straight, but again, it's all in hand. 

We've also changed the angle of the steering arm as this seems to give a more positive and more natural movement to it all, in reality it doesn't make much of a difference but it all helps to make for a better steering operation. 

 

Tightening Up The Steering Mechanism

Whilst we have been working on a number of areas of our robot, we've not got a huge amount to report at the moment. 

However, one area that I've been very keen to get on top of is the steering. In our 2019 Pi Wars robot we had about 2mm of slack in the steering components and whilst this didn't cause too much of an issue, it was one of the things that I really wanted to sort out but simply ran out of time before the competition started. 

So with time on my side at the moment (I know I'm going to regret saying that), I decided to tackle this niggling issue once and for all. 

The gears that I designed and printed have almost no play in them, so the only other area it could be was in the steering arm and servo horn. 

So the solution was to add nylock nuts to the steering arm connecting rod and to replace the plastic servo horn with an aluminium one. 

The servo mount is already a great deal more rigid than the one we made previously, so that along with the upgraded steering arm has resulted in a very precise and positive steering mechanism. 

Steering Mechanism Before

Steering Mechanism After