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Thread: Ensign Wedgeley Crusher (FW Sportsman)

  1. #31
    I’m hoping that I understand what you are meaning - I’ve found that so long as the weapon can be locked in a specific safe position it will pass the safety check. For example, Strix’s weapon is operated by a linac and locked when the flipper was wide open, but if I could design something that speficially locked the flipper when half closed I imagine that would pass checks too. It doesn’t have to necessarily be at the end of a weapon’s travel.
    I would personally just operate the jaws to a fully open position at the end of each fight and shove a chunk of hdpe between them to stop them clamping down.
    Also my linac could probably travel like 5mm-10mm before it came into contact with the bar. Within reason, it doesn’t have to be a 100% press fit. So you needn’t worry about getting the weapon in literally the exact same position each time.
    i guess you could make some sort of adjustable locking device but I think that’s more complicated than it needs to be.
    Hope that helped somewhat. I actually made my locking bar at the event itself, I’m sure you could do the same if you are unsure about what would be appropriate.

  2. #32
    Yep that's what I was on about! Thanks, that sounds like a plan. I will go for the "chunk of hdpe" approach and take a bag of offcuts in case the tech check asks for anything else....

  3. #33
    No worries - just so long as the bar or whatever can stay put on it’s own, and is big enough to grab without putting your hands in the path of the weapon, you will be fine

  4. #34
    Speak to the EO about it. Locking bars on slow moving electric actuator weapons are a very grey area; some argue that they're required, others argue that the link is effectively the locking bar as the motor won't turn without power and most actuators can't be back-driven. At Robot Wars, we got told that Coyote didn't need a locking bar for its jaws, but then the person doing the tech check disagreed and asked us to make one.

  5. #35
    FRA Build rule 1.6 covers it. All weapons need a locking bar, but it's up to each EO if they choose to let you run without one.

  6. #36
    Thanks guys.

    I think the easiest thing is gonna be to just cobble something together, if they don't deem it necessary there's no harm done.

  7. #37
    Predictably, we went right to the wire with this build again. Didn't help that I had a stinking cold the week before Robodojo... I woke up on the Friday morning and really just felt like going beck to sleep, but I had a clear day and there was a decent chance the Hackspace would be busy on Saturday so I wanted to get cracking.

    FRIDAY 10th MAY
    As mentioned, I woke up feeling like cr*p. I decided that I'd be better off spending the morning sitting down so I got started on the electrics for the new linac. As mentioned previously, the linac runs off another Argos drill motor, to minimise the number of spares we have to carry. We considered using a relay switch to run it but a cheap ESC isn't much different price-wise and offers some finer control if needed.

    My main job for Friday was thus to put some Anderson connectors and ring terminals onto the ESC, and then to wire up some microswitches to use as end stops. I'm quite pleased with these, since 1. I figured out how to set them up from scratch then found the exact same circuit diagram I'd sketched on the Gimson website, and 2. they worked first time, i.e., I had the diodes the right way round and hadn't cooked either of them while soldering.

    If anyone is interested and doesn't already know, this is how the limit switches are wired up:

    I spent a few hours tinkering with all this lot, all the while lamenting the fact that I'd seemingly forgotten how to solder. Having completed almost everything, I decided to maybe see if I'd possibly just chosen a slightly duff iron, so I tried the one on the next bench and suddenly soldering was easy again. Would've taken about half the time otherwise, but I quite enjoyed the sitting down aspect of the process so it wasn't a dead loss.

    I then spent the rest of the day making an adaptor to fit to the leadscrew nut. Basically a doofy do that stops the nut spinning and provides an attachment to transmit the axial/linear force out to the rest of the jaw mechanism. We'd got a bunch of little bits of aluminium so I made a little frame thing that fits around the nut:

    (Image taken after the event, hence the rest of the mechanism is also there, as are the limit switches.)

    Although this worked fine, I felt like I entered some kind of transcendental state of bodging while making these parts, as not a single face I cut managed to be at right angles or indeed anything resembling flat. I eventually give up filing it and let it be, lest I file it into nonexistence.


    Despite much procrastination, we were in reasonable shape going into the last day of building. All three of us were free for the whole day so we headed to Hackspace early in the morning (by which I mean, about 9AM) to get started. Remaining jobs at this point were:
    • Finish the nut fixture which needed a couple of extra hole drilling and tapping
    • Mount the limit switches to the linac frame
    • Try to beef up the mounting for the motor and bearings of the linac (currently just CNC'd HDPE)
    • Put some armour over the linac
    • Assemble the lower jaw/front fork and fit to the chassis - fairly simple job, quite a few holes to drill/tap
    • Add some "tailfins" to prevent wheelying and hopefully reduce the chance of getting flipped
    • Add some spring steel strip to the front of the wedge to stop the HDPE getting chipped
    • Cut/drill/mount all the linkages and parts for the upper jaw and mechanism
    • Cover for the sharp ends of the forks and a locking system

    Some of these jobs were optional, and some could be done in "tinkering time", to borrow once more from Scrapheap Challenge - that is to say, in a yet more bigger rush and shoddier manner on the morning of the competition.

    I had ordered most of the aluminium for the weapon linkages already cut to size from Metals4u - they don't appear to charge (much) for cutting so most of the pieces were only a quid or so. Simon took on the job of drilling holes in them and filing the corners down, and of cutting and grinding the front forks to shape (they're made of cheap mild steel, probably not up to much in full combat but fine for what we need). Meanwhile, Becky discovered the joys of tapping, as many threaded holes were required for the lower jaw assembly.

    We decided to scrap the idea of cladding the wedge in spring steel for now, as it unsurprisingly turned out to be hard to drill. Reading around, I will give it a try with a 90° milling bit that I bought for CNC engraving. We also had to drop the tailfins, as it turned out they would be harder to mount than originally thought and might have interfered with accessing the link.

    The extra bits on the linac were also left off, as we just didn't have time to finish. However, we got pretty much everything else done!

    Dry fitting various parts. Note the carefully engineered blocks to wedge the motors in place:

    Test fitting lower jaw/weapon mount:

    Lower jaw in place:

    Linkage integration:


    Previous Wedgeley for direct comparison:

    In my last update I made, or at least implied, a bold claim...
    Quote Originally Posted by McMullet View Post
    … the crusher (which will undoubtedly destroy exclusively itself if ever called upon to crush anything more substantial than a coke can)
    ... namely, that the crushing mechanism would NOT destroy itself if called upon to crush anything OF EQUAL OR LESSER substantialness than a coke can, and that is would INDEED CRUSH SUCH A THING.


    I was seriously terrified at this point that the whole thing would fall apart. As it turns out, the shaft collars aren't quite up to the axial forces and will start to displace if faced with an excessively resistant foe (e.g., a bean tin), so for future iterations we'll need to modify that part of the machine (might see if my dad can just weld if for us...).

    I will write up our experiences at the event shortly, but here's the final final build, with a few additions made on the day. Obviously there's a spoiler here that Wedgeley survived intact, but it was only a sportsman competition so that shouldn't come as too much of a surprise.

    This is the final form, with armour over the linac, to protect from axes and when flipped over:

    All just scrap bits screwed in place.

    Skid bars fitted to prevent wheelies - these were some very conveniently-shaped bits from the offcuts bag!

    Finally, the new weapon is designed to come off as one sub-assembly - just an Anderson connector and a couple of bolts and it slides off:

    Obviously, that also means if a couple of bolts break, it falls off, but we live in an imperfect world. This has the advantage that we can take the weapon off and drive it (relatively) safely around the house. I've been experimenting with various dual rate/exponential settings to make it more driveable in future.

    Last edited by McMullet; 18th May 2019 at 14:47. Reason: Extra pics

  8. #38
    Ocracoke's Avatar
    Team Kaizen

    Nice write up and was glad to finally meet you and Ensign Wedgeley Crusher in real life at RoboDojo. Was it my imagination that it seemed to move with a all or nothing affair? It seemed to be wheel slipping everywhere which I imagine made controlling the robot difficult. Could do with some bike tyre on the wheels perhaps?
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  9. #39
    Quote Originally Posted by Ocracoke View Post
    Nice write up and was glad to finally meet you and Ensign Wedgeley Crusher in real life at RoboDojo. Was it my imagination that it seemed to move with a all or nothing affair? It seemed to be wheel slipping everywhere which I imagine made controlling the robot difficult. Could do with some bike tyre on the wheels perhaps?
    Thanks, likewise! Hopefully we'll see you at the next one, maybe with Azriel along too?

    Controlled movement is still very much an issue, yes. I think the bike tyre idea may be a winner, either that or get some Colsons which was the original plan. Seems to be hard to get hold of the 5" ones though (they only ever seem to have one in stock at Robotshop which is not really going to improve matters...). I think the power-to-weight ratio is also part of the problem, as we're still only tipping the scales at about 7.3 kg - still definitely very underweight, though at least now the robot is significantly heavier than our cat. Playing with the Tx and dialling the power waaaaay down makes it quite driveable and still fairly nimble.

    Now.... for an event write-up.


    We started off this event in slightly better fashion than the one in January, as we didn't get lost/stuck in traffic on the way up the M1. Having finished building shortly before 8 PM on Saturday, we dashed home for the now traditional fish and chips and got to the pub we were staying in by 10:30, so plenty of time for a pint before turning in.

    We decided our main aim for this event was to win at least one fight by KO. Subsequently we added two more, which were for the robot to function for the entire event (i.e., not break down or need repairing) and for use to successfully grab another robot in the jaws at some point.

    We arrived at the event in high spirits, spirits that we slightly dampened by the absence of the excellent bun van than had been there in January as we were looking forward to another delicious breakfast cob. But no matter, we staked out a quarter of a table by the door and did some last minute tinkering (mainly adding the chunks of scrap HDPE in the photo from the previous post, giving some protection to the chain drive and lead screw).

    It was great to see a some familiar faces and 'bots, and we were sharing our bench with Luna-Tic, Crota, Amnesia and Bhargest.

    Fight 1: BWX
    For our first fight we were drawn against the latest iteration of Boring Wedgebots, number ten, abbreviated to BWX. Becky lost the die roll and so had the dubious honour of driving.

    BWX was looking a bit smarter than the last one we saw (eight I think), with a fancy paintjob, proper looking wheels and big ol' spike on the back. It also didn't have a huge block of steel cable tied on top to weight it down. However, the Sportsman side of this event was looking pretty strong so BWX felt like one of the less terrifying opponents.

    As discussed above, Wedgely was once more pretty twitchy to drive so any precise manoeuvres to bring the jaws into play were out of the question, and this ended up as more of a shoving match. Note the chorus of "ohhhs!" followed by complimentary remarks near the start - unfortunately I failed to catch this in the video because I was watching it, but basically the robot nearly went over the edge of the arena before dramatically reversing at the last moment.

    Here's the fight then:

    A lot of wheelspinning, a lot of wheelies, very little directional control... but ultimately VICTORY! Wedgeley Crusher's first combat win.

    Fight 2: Amnesia
    Yes, so this is Amnesia as in the FW champion Amnesia, so (with all respect to Theo and BWX) a slight step up in terms of the opponent intimidation level. It seems like the sportsman competition has become more of a "no spinners" affair, rather than the "beginners and bodgebots" that is was in January...

    Simon had the mischance to drive for this round:

    Thankfully Adam was kind enough to flip us back onto our wheels after flipping us 10 seconds into the fight... We then managed to end up with both robots simultaneously beached on the edge of the push out zone, then we managed to get free but immediately got stuck again.

    Unsurprisingly we lost this fight but it was enjoyable and I think we did well to manage a couple of minutes vs the FW champ!

    No significant damage from this fight, and the wheely bars seem to have helped a bit... maybe.

    Fight 3: Midas
    We faced Midas last time. It looked scary, which may be why we "accidentally" drove off the side of the arena on that occasion. The crusher was probably the weapon that was most able to do us damage, since the flimsy bits of extra HDPE armour were only going to be helpful against impacts (so axes mainly), if anything, not sustained pressure. This time it was my turn to drive.

    Pretty clinical work by Midas here... didn't stand a chance once we'd been grabbed. This is where the only way to win would've been to out drive the opponent which wasn't on the cards due to the robot being undriveable and indeed undriven by any of the drivers before the day.

    Intermission: Nut Collecting (Satanix and BWX)
    During a lull in proceedings we had a quick non-combat game vs Dave with Satanix and Lucy who took a loan of BWX. I was volunteered to drive since I only got a brief go in the previous round. Wedgeley continued to be difficult to control, although the ability to spin VERY FAST is useful when you want to redistribute the loot a bit...

    Fight 4: Tantibus
    Before every fight we'd been saying "ooh I hope it's not one of those nasty axebots", so I suppose it was inevitable that we'd get a nasty axe at some point. This was the point in question.
    As we'd each now had a good go each at driving, we started the lottery again from scratch and I managed to lose again.

    Again, pretty clinical job by our opponent. Two things stand out here: one, complete lack of traction - we had our wheels on the ground, so should've been able to shove back at least a bit; and two, the front forks need to be sharper/lower to the ground. Our supposedly wedgey front bit met the vertical slab of Tantibus and bounced right off it. Probably shouldn't have raced right towards the opposition either...

    In any case, this was a more successful second outing for the Ensign, and I'm happy with how the weapon came out even if we didn't get to use it. We need to make a few tweaks for the next event but if it came to it we could pretty much take it back without any additional work and it would just about do. However we will make a few mods before the next Robodojo in July:
    • Improve the top jaw a bit - maybe have some sharp teeth, and something more substantial than HDPE between the steel parts
    • Sharpen the lower jaw
    • Better traction!
    • Find something better than shaft collars for the lead screw restraint

    I also need to replace one of the diodes in the limit switch circuit as I cooked one while trying to crush another can.
    Last edited by McMullet; 23rd May 2019 at 13:50.

  10. #40
    Ocracoke's Avatar
    Team Kaizen

    Glad you had a good time! I really should have come over and see if I could have helped with the twitchy controls, it reminded me of The Honey Badger 2.x as to how quickly it was going (side note: I miss that robot).

    Thanks, likewise! Hopefully we'll see you at the next one, maybe with Azriel along too?
    If it is July, potentially. Jibril and a upcoming BotFest event is my main focus at the moment but I would like to go to another RoboDojo event if I can get the availability to do so.
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

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