Team Shadow: Ferrovore

[Danny B]

After running the old FW at a few events, we've decided to retire it due to a lack of compatible spares and the fact we were getting a little bored with a simple rammer. So we've decided to commit to a new FW, this time with an active weapon.

List of parts acquired so far:

• 2x Gimson GR02 motors
• 2x pairs of 125mm Banebots wheels
• 2x Botbitz 85A ESCs
• Plenty of 12V NiMH batteries
• 1x transmitter/receiver
• 1x Gimson GLA4000 linear actuator

The plan is to build a grabber/crusher robot, somewhat similar to Pitbull or Chompalot in terms of it's proportions. The steel for the top half of the jaw has already been machined(see the picture below), and the frame for the bottom half should be together in the next month or so.

Watch this space for more updates!

[shakesc]

nicely cut, where did you have that done?

[Danny B]

We're in the fortunate situation that one of us has access to a CNC mill at their workplace, so cutting conventional metals has become a very simple and cheap affair.

If all calculations are correct, the jaw should have around 230kg of force at the tip of the fangs. Probably won't cause much damage to well-made bots, but should still be enough to get a very solid grip.

[daveimi]

That's impressive, can still remember us attending our first event at the same time lol

[Danny B]

That's impressive, can still remember us attending our first event at the same time lol

Hopefully we might run into you again in Barnsley next year, it'll be good to see you again and maybe get Ferrovore's teeth into whatever bot you bring XD

[RogueTwoRobots]

Pretty sure Barnsley has been pulled from the live tour for 2016.

[Danny B]

Really? Bummer. Are there any other non-spinner events in the north?

[daveimi]

I've been waiting for the schedules for 2016 to come out, am hoping to get on the one in Jan.

[Danny B]

I've just had a look at the ticket website, looks like my best shot is Manchester in April.

[daveimi]

Yeah gonna sit down and have a sort out what's going on in 2016 at dinner time today hopefully.

[Danny B]

UPDATE

So, after some pondering, we've come to a agreement regarding what to do when the bot is flipped.
Due to the way the internal components and weapon mechanism are likely to be laid out, the body is likely to be flat-fronted with a sloping back (a la the series 5 version of Kat 3), giving us 2 options.

1. Move the drive wheels right to the back. This would be the lighter and simpler option, but it gives us no way to bring the weapon back into contention other than someone else flipping us back over, not to mention it would also make the front end very twitchy.
However, the biggest problem as far as we can see is that the bulk of the robot's weight will be at the front, especially if another robot is being dragged around in the jaws. If the wheels are at the back, there will be no weight on them and therefore very little grip.

2. Add a srimech. This would mean the extra weight of another actuator and a battery to power it, but it's a consistent and repeatable way to keep the weapon in a useful state. Also, it means we can move the drive wheels further forward, improving balance and grip.

In the end, we've decided to go with a srimech arm down the back, most likely powered by a GLA750-S to give it the speed it needs.

[Danny B]

An autonomous srimech! It's never been done before as far as I'm aware, we could be the first to do it.
The plan is to install a tilt switch in the robot, and if the onboard IC chip detects that it has been upside down for 2 continuous seconds, it will send a timed pulse to a DPDT relay to extend the srimech actuator. At the end of the timed pulse, the relay defaults to reverse and the actuator retracts until it hits its limit switch. (Program is in the photo below)

Meanwhile, the box section for the bottom jaw has now been cut and drilled, should be getting that welded together. Slight change of plan has been to extend the bottom jaw almost the whole length of the bot, so it can act as a reinforcing 'spine'. Now that all the large components have been measured, there's enough information to plan out exactly how they will be laid out inside. (See below)

[Eventorizon]

Its a good idea in theory and it would be interesting to see it implemented, but I think that for some reason or another you will find it causes more issues than it solves.

The tilt switch may be activated by hard hits during combat, which is more an annoyance than an issue, but if you were say hit by a vertical spinner and tossed your shrimec would start coming out before you hit the ground and potentially break on hitting the ground. It could also mean it sticks out at an unwanted moment and gets taken out/twisted/ripped off by another robot.

Id also advise against putting your wheels at the front of the robot as it makes it a pain to steer, you are better off having them in the middle, just rearward of the centre of gravity. Our new Axe bot has the wheels at the front and it has a habit of not driving straight when accelerating because of this.

You also don't need to have separate batteries for your drive, weapon and shrimec (unless they are all different voltages). It adds wiring complexity, more safety links and more points of failure. Conker 3 has a 5S (22.2v) Drive system and a 12S (44.4V) Weapon system so it has to have separate voltages as they are vastly different. However, given your list of parts, you only need 1 massive 12V pack to drive everything. You could slightly over volt everything to say 14.4V (I am assuming you are using 1.2V NiHM cells) to get a bit extra speed and power from the parts. A small overvolt wont be an issue as the parts run for a maximum of 5 minutes or so in a fight.

Hopefully that gives you some ideas and should help make your build easier!

[Danny B]

You raise some good points, although I have considered most of them already and figured out some countermeasures.

I figured the tilt switch would be sensitive to lateral force from a jolt, so I turned it around and programmed the circuit to activate when the switch is off, meaning the robot has to be completely upside down (within the 30 degree sweet spot in which the switch is inactive).
Also, to prevent it from activating before the bot hits the ground, I programmed the IC to only activate the srimech if the robot has been upside down for 2 continuous seconds (check it's upside down, wait 1 second, check again, wait another second, check again. If all 3 register, activate the srimech).
Not to mention, I don't plan on entering spinner events in the near future.

Regarding batteries, I suppose I could put the drive and weapon on a single battery. I probably still need a separate one for the srimech actuator, since it's running on a speed 550 motor and therefore a large drain.

Taking your advice on the wheel placement, I did some rearranging. Geometrically, the wheels are in the middle, and I can't really move them back without putting them right at the back.
So to shift the centre of gravity forward, I moved the batteries to the front. That combined with the weight of the heavy steel jaws hanging right out at the front should do the trick.

[Eventorizon]

Regarding batteries, I suppose I could put the drive and weapon on a single battery. I probably still need a separate one for the srimech actuator, since it's running on a speed 550 motor and therefore a large drain.

That's really not a problem. A 550 motor is tiny in comparison to some of the motors (Speed 900's for example) that were used on NiMH Packs about 4/5 years ago (before LiPo's were commonplace). People would run two 775 motors (Drive) and a speed 900 off one NiHM Pack. I even have a picture somewhere of someone running 4 Speed 900's for drive.

As for the shrimec, that should all work. It will be interesting to see if it works in the arena.

Oh, and I cant tell from your drawing which is the front and which is the back, might just be me.