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Thread: Ensign Wedgeley Crusher (FW Sportsman)

  1. #51
    There's another Robodojo event next weekend, so it's time to pencil in some panic-bodging for next weekend.

    In the meantime, I have made one change recently. Currently Wedgeley has only ever crushed drinks cans, but whenever he did so in the past the shaft collar on the lead screw that operates the jaw has slipped, which then pushes the shaft back and locks up the chain.

    No more!

    Now that collar is going nowhere, and Wedgeley can crush with impunity.
    Disclaimer: This means that another bit will probably fail when trying to crush future items.

    The welding was done by my dad. There is a MIG welder at the Hackspace that I will learn to use at some point, but I like the idea of this piece of welding history being involved at some point:

    Hopefully some exciting updates to follow later in the week...

  2. #52
    A strange thing happened yesterday... we finished all the fixes and mods to Wedgeley a whole day ahead of schedule. Partly that's because there wasn't too much (critical) stuff to do, but still this was unexpected. I assume something is now going to go horribly wrong tomorrow (forget to take Tx, battery explodes during fight, etc.). For now though, I'll just bathe in the glory thanks.

    First up, I had to replace the drive motor mount that got slightly borked last time, which was simple enough. Hopefully a bit more robust this time. We'll see I guess.

    The whole upper jaw mechanism needed fettling, which was a bigger job. There were a few pieces from last time that were meant to be identical that were decidedly not so, and some pieces were just fundamentally the wrong size. That made the motion of the jaw quite stiff and wonky. Nothing major here, just a bit less imprecision than before:

    Next, new teeth. Waaaay back in January I bought some M6 stud to grind into sharp gnashers for the original Wedgely, but both times have run out of time and bodged something else instead. Now, we have teeth:

    These are just cheap putty steel studs so they aren't going to cut through anything substantial, but should be enough to dig in and get some grip at least. Of course, with such FORMIDABLE AND TERRIFYING WEAPONRY we are going to need some serious safety devices:

    At the last Robodojo, we hurriedly installed some protection over the weapon mechanism immediately before facing Tantibus (i.e., an axebot). This was not the most substantial or comprehensive piece of armour, so it's been upgraded a bit:

    The "tailfins" are to protect the battery/electronics compartment and also stop the robot getting flipped over so much. Speaking of which:

    It seems like we're most prone to getting flipped over in a backwards-ish direction, and these bits of HDPE are hopefully going to tip us back onto the wheels if that happens. I doubt they'll last long, but they shouldn't be needed too many times.

    It even sort of works:

    Not really a SRiMech but it'll take a lot more to get us over now at least.

    Cheers for reading, and probably see some folks at Robodojo tomorrow!

  3. #53
    Robodojo was a mixed bag in terms of our performance this time. On the plus side, nothing broke (just a few knocks and dents as usual) and we managed to use the weapon in one of the fights to actually grab something. Unfortunately we also lost all 4 matches and Wedgeley is still completely impossible to drive in a controlled manner...

    The weekend got off to a bad start when Simon adopted a cat the day before, so he couldn't come. I suspect he did this with the express purpose of getting out of driving the robot, but I'll give him the benefit of doubt this time. At least that left a simple coin flip to decide whether Becky or I would have the dubious honour of driving in the first fight (I lost).

    First fight was against another crusher, Jamie's Reaver.

    I did manage some vaguely controlled driving here and a few grabs were attempted, but the anti-wheelie bars, along with general lack of traction and instability, meant the best I could do was avoid the more intimidating crusher on Reaver. Ultimately the wheelie bars defeated me...

    Next was Crota, upgraded with a new axe vs the sort of machete thing it had last time.

    The wheelie bars were shaved down a bit for this fight which seemed to help a bit with mobility, if not with steering. However, Becky did manage two firsts in this fight: a) it lasted a full three minutes; and b) the crushy grabby jaws grabbed some stuff, and possibly even did a tiny amount of cosmetic damage! We lost the judges decision, but only by a single point, which isn't so bad.

    Originally it looked like we'd be facing Midas in round 3, but it ended up being Parasite, another axe.

    So I think this fight indicates that the wheelie bars were in fact not shaved down enough, since we got beached again... Not much to say about this one really, I couldn't really bring the weapon to bear and ended up between Parasite and OOA pretty early on. Although we didn't do too badly in the pushing match, it was pretty inevitable we'd get shoved out from there.

    Finally we were up against Mitternacht, another crusher.

    I think this fight was broadly similar to the last one really. There was a brief moment where we might have stayed in the arena by chomping down on Mirtternacht's weapon, but I think we're still getting the hang of having an active weapon that works.

    So all in all, positive results in terms of the weapon and robot functioning reliably, but a few important lessons learned:
    • It's hard to focus on opening/closing jaws whilst also driving a barely controllable robot.
    • See above - the robot is barely controllable.
    • The weapon doesn't seem to be 100% reliable - sometimes it didn't respond at all.

    Although I don't want to do much more work on EWC, I think sorting out the driveability issues would be worth doing. I think that should be achievable and would leave us with a pretty usable, if not mega-competitive, machine to be going on with while we work on something else. In order to do that I'm thinking two changes are needed...

    1. New wheels. The scooter wheels look cool but they're just a bit pants. As a bodged solution six months ago they were great, but the contact with the ground (even after rasping 5 mm off to make them flatter) is tiny, and the rubber is too hard to be grippy. I'm thinking of having a go at CNC'ing some HDPE wheels and putting bike tyres on instead, which should be a good exercise.
    2. Gyro. The weight distribution on EWC is just so wonky it's unlikely to ever want to go in a straight line. Better grip will help, but I like the idea of trying a gyro anyway. It's kinda "belt-and-braces" to do both but I'm thinking that a tenner for one of these is worth a go. Anyone tried using this component in a robot, or have any better solutions for a cheap gyro?


  4. #54
    Last weekend Al mentioned that the pic of our locking system made it look a bit like the jaws had munched into the chunk of wood themselves... So I had to give it a go...

    Made some rather unpleasant noises in the chain drive but it did manage it; I don't think it would work on any of the other teeth (not enough leverage), but I was pleasantly surprised by this in any case.

  5. #55
    With a mere 9 days before the next Robodojo, it must be time to start PANICKED WEDGELEY UPDATES.

    The big job for this update is wheels, we need wheels that connect with the ground in a more grippy way than the current wheels. I considered getting hold of some Colsons, or other castor wheels, but I thought this would be a good opportunity to learn to use the CNC router.

    Good heavens, machining HDPE is MESSY.

    But mercifully easy to clean up:

    Machining aluminium is not messy though it takes aaaaages.

    It appears to work, in so much as the hub fits in the wheel!

    Just need to manually drill out and tap some holes now. And make another one of each of those, and also a bunch of other bits as obviously 20 mm thick wheels aren't going to fix the traction problems.

    Next week, that, plus hopefully some hilarious mishaps with a drift gyro.

  6. #56

  7. #57
    We'll be screwing some mountain bike tyre into the plastic for that purpose - though I think the thin scooter tyres we've used up to now were problematic partly because they could so easily miss the floor due to relatively small irregularities. However they only had about 5 mm or track width in contact with ground which is a bit of an extreme case!

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