PC Plod Build/Upgrade Log

[callumhoy]

This is a build/upgrade log for the heavyweight robot PC Plod which I just purchased from the previous owner for £45. That's a full chassis, armour, drive motors, wheels, weapon motor and most of the electronics for a, currently, 67kg robot for £45. Bargain!
I will be starting simple by just adding a transmitter/receiver and replacing the dead batteries in order to get it driving again. Then the team and I will begin work on adding an active weapon, as the old spinning disk shattered in a battle in 2000, when the robot was last used.
As this is the teams first ever attempt at work on a combat robot I will be documenting any and all changes or advancements I make here. All feedback and advice for a new guy is appreciated.

Turns out that they're still making the same type of battery that was put into the robot 16 years ago, YUASA NP Series NP 12-12. Since the team has no practical experience with combat robotics we've decided the safest bet for now is to just use the same type of batteries that were used before.

Integrated Robot Controller Document I was given with the robot.
Photo Album for PC Plod
Robot Wars Wiki for PC Plod
NP 12-12 Datasheet

[typhoon_driver]

What do you have in mind for the bot? Bearing in mind that the electronics, batteries, weapon, probably armour etc are all very old school tech and unlikely to do much in the modern arena.

What drive motors does it use?

[callumhoy]

Quite honestly right now I haven't much more in mind than to get it functioning properly. I doubt I'll be happy enough to have it entered into a competition for a year or two, this will be a long ongoing project for me.
Once it's working again I'll start work on replacing parts to upgrade it to a modern standard.
The drive motors are two 24V wheelchair motors. According to the previous owner they will do about 6mph.

[callumhoy]

I've been looking into different 2.4ghz transmitter/receiver pairs over the past few days and I've come to realise that I lack the ability to realise which controllers would work with PC Plod. The robot works off of effectively tank controls, both wheels forward to go forward, both back for backwards and one each way to turn, so both motors can spin both clockwise and counter-clockwise. I know we'll need at least 4 channels, possibly 6, one for each wheel motor and one for the weapon. Plus one spare left over, probably to be added to a srimech when we eventually add one.

So my question to all those with knowledge is this, what sort of things should I be looking for in a transmitter/receiver? Will any of the ones listed below actually work for my needs?

1) Radiolink 2.4GHz T4EU 4 Channel Transmitter Radio & Receiver
2) Radiolink T6EHP-E 2.4G 6CH Transmitter w/ R7EH Receiver
3) FlySky FS-i6 6CH Transmitter + iA6B 2.4GHz 6CH Receiver with Telemetry

If you need me to give more information let me know, I'll give what limited information I can.

[joey_picus]

You can run all the motors on one side from the same (side of a, for dual channel* controllers) speed controller, so you don't need a separate radio channel for each motor! The speed controller will drive the motors forwards and backwards from just one radio channel, so the bare minimum you'll need is three - two channels for drive and one for weapon. The drive channels are often 'mixed' to give forwards/backwards/left/right control on one joystick; this function can be done in the radio transmitter, in most dual channel speed controllers, or a separate device known as a 'mixer' in the robot between the radio reciever and speed controller(s).

All the sets you linked will work; the key thing for combat robotics is that the reciever failsafes properly (to avoid a runaway robot). I use odd radio gear myself, so I'll leave specific recommendations up to others, but it can come largely down to personal preference, and it's not something you need to worry too much about committing to too heavily as it's completely swappable.

*try not to get too confused between 'channels' on speed controllers and radio gear. it does happen. :P

[callumhoy]

Thanks, you've saved me from spending another hour or two reading everything I can find about transmitters unnecessarily and stressing over it all.

[callumhoy]

The old integrated speed controller has been entirely removed, cutting the circuitry down to the bear minimum needed to test all the motors. Batteries, through the safety key switch, into the drive motors.
Both the drive motors and the weapon motor appear to be fully functioning. So, with a Sabertooth speed controller ordered and on its way, I'm hoping for a first drive test within the next two weeks.

[daveimi]

There is a jumper on the sabertooth that let's you tune the sensitivity at different throttle inputs. I've done loads of testing with a sabertooth and wheel chair motors and the middle of the road settings all worked the nicest. If you read the instructions when you get it you'll see what I mean

[callumhoy]

Thanks for the advice, you've probably just saved me hours of playing around with different settings.

[harry hills]

You may want to upgrade from a sabertooth for actual combat. Dimension engineering products are a bit shit at the best of times now it seems and the boards are super delicate. Maybes something like tz85 or ragebridge for an upgrade

[callumhoy]

I agree, I intend to upgrade before putting PC Plod back into combat. Thanks for the recommendations.

The Sabertooth will likely be moved into a prototype featherweight as and when it gets designed and built.

[callumhoy]

Looking at the way the front of the robot is designed, the weapon would be entirely ineffective in combat with the bots being so close to the ground. So, we've decided, in an attempt in avoid having to redesign the chassis, to redesign the front plate setup. This should reduce the ground clearance and provide a ramp to force the opposing bot into the spinner.
This is how it looks in a first draft out of scrap metal:
IMG_1311.JPG
And here's a drive test with the draft front:
https://www.facebook.com/TeamTheScra...88734953835798

[callumhoy]

After attaching the weapon motor/weapon mount, we're struggling to see how the old cutting disk was mounted. Our original guess was that the holes in the front of the mount were where the disk was mounted and it was belt driven.
However, the largest disk that could fit (it's against the bottom plate) barely shows out of the front panel. Meaning that it's useless as a weapon, unless an opponent drives all the way up the front, and even then it would barely scratch the bottom of the opposition.
Any ideas?
Photo 7.jpgPhoto 8.jpgPhoto 9.jpg

[callumhoy]

So, we have absolutely no idea how to mount the weapon. As I said before, the biggest disk that would fit only extends out the front of the bot by a few millimetres. Explained in this video:
https://www.facebook.com/TeamTheScra...0165626710589/
So we're either going to have to change the weapon mounting system entirely, or change the weapon into something different entirely. And considering my personal preference of 'control weapons' such as clamps, crushers or lifters. It looks like we're going that route.

[callumhoy]

PC Plod's current weapon system is useless. So we're going to design a new one. Which weapon systems should we make designs for?
http://www.strawpoll.me/12980979