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Thread: Electric Axe featherweight - first build of FW

  1. #91
    McMullet's Avatar
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    D'oh! Shame about the paint.

    Other than that though, looks great - I've enjoyed skimming through the thread and will come back for a proper read later! Good luck in Portsmouth.

  2. #92
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    Thanks McMullet,

    So having opened up the bot and realising the battery wasn't in the robot when i weighed it, it means current setup is now 45 grams over weight. I think the additional wiring looms and paint have added to last years weight as well as the additional hardox plate over the battery and weapon motor.

    Im not happy about the amount of hardox on the side panels, although it looks good, i may sacrifice one of the sides and replace it with a flat panel of hardox, hopefully removing about 100g off the weight, currently each side panel is 950g in a folded 'dome' shame, so flattening it out will decrease the amount used.

    Also i did weigh it with the biggest battery, my 3.3amp 4s lipo, which is 100g heavier than my 2.6a 4s and my 2.3a 5s battery, so i may well be reusing these in battle instead of the heavier.

    Addition i removed a small section of battery protection hardox - this was added after Al and his crusher showed that this was a potential weak point at last years Portsmouth event, so i reduced the cover here and saved 45 grams, so, in fact if i don't do anything, the 100g battery and 45g plate saving will bring it under by 100g. Will still look at other areas i can shave off weight.

    If i go brushless on the weapon motor, this will greatly help as that motor weighs 1kg shy of. the front wedge is 2kg, side panels are 950g each and the back weapon cover was 1kg.

    One thing i am interested in asking others is how much does their welded hardox chassis weigh in comparison to a HDPE chassis and then looking at the designs of the way the chassis is constructed in Hardox to overcome the weight disadvantage and maximise the strength across the whole chassis. I was comparing density stats last night to work out a way of replacing the side panels so it got me thinking about this.
    Last edited by Roboteernat; 28th May 2019 at 21:00.

  3. #93
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    Portsmouth Extreme Robots 2019...

    So, that was fun!

    Firstly, thank you to the guys, Al, Dave, Ollie, Shock Will and Will and team for your help in various things during the weekend!

    The event went well, and managed to highlight a few interesting niggles of the robot that hadn't been seen before. These 4 fights over the 4 shows would be the bots 8th - 11th 'fight' so some of the parts had been used and abused.


    Having solved the weight issue by removing some of the hardox plate which wasn't strictly needed in those areas, and then removing some of the decorative aluminium tread plate from the top of the bot - the sections which were covered by the hardox sandwich, Wanna Choppa was now underweight. With the smaller battery, it would be OK.

    The new wiring did bulk out the wiring weight, but this was accommodated. A trick if you run out of black wire 12AWG, use 12 red and use black heat shrink! more wire now been ordered.
    20190512_182947.jpg20190516_172345.jpg
    So to the first day.
    Loading up the car with the bot, i failed even before i got to the car, with the gravel beating the balance of the bot and bits on the trolley i recently acquired from the tip - £4 well spent!
    20190518_083439.jpg

    Picked up Ollie as we were car sharing and arrived at the venue.

    Passed tech check, this time remembering to put the wires into the correct channels! i was able to fly through the tech check. The lights didn't fail on me that time either!

    Added some yellow UV paint for the new format of the show and i am very please by how much it glowed!
    20190518_125124.jpg20190518_163223.jpg

    1st fight.
    The bot went in... and came out! the lovely paintwork had a few scratches, and it was evident that the wedge was scooping up a lot of robots, so i was pleased by the GC again.
    What did happen however was my wheel bolt, my self made M5 LH bolt that holds the wheel on had snapped, meaning the wheel would unwind and lock and only really work one way.
    20190518_133629.jpg

    As a result of the wheel unscrewing, the thread on the gearbox stripped and damaged the thread on the insert into the wheel.
    I swapped out the gearbox for a spare one i have, and replaced the insert with a smaller brass one. back up and running.
    I was able to screw the new insert and lock it into the gearbox using a longer screw from Al and i was able to fix it for the 2nd fight.
    20190519_101648.jpg 20190518_195027.jpg



    2nd fight.
    Seemed to go ok, except towards the end i lost What was also interesting was CATastrophy managed to get underme as i was jostled by them, and slammed me against the arena wall. I was luckily able to drive upside down which was a bonus, unsure if the axe was out and therefor stopping it from resting on the wedge - need to review footage, but i was able to drive about. Before being slammed against the wall again. I then left my position in the control area to get a better view of the robot to see if i can drive - lots of people meant viewing was limited - i left my stool! Managed to find a hole to see through, and fired the axe, and somehow i was able to self right! I think if the axe was out when i was upside down, the 135 watt motor may be able to self right, otherwise the weight saving could have tipped the balance? either way i seemed to have self righted!

    Sadly, Pink team won the fight despite only having 2 yellow feathers in the arena and finishing with 2 yellow working

    That evening,
    I managed to make a spare wheel and machine down the hub so that the bolts i had would fit. I wont say how i did it without a lathe or mill to hand and only a pillar drill and single flute cnc router bit as it was extremely dangerous!
    The 2nd fight I used a smaller brass 3/8 insert to fit into the hub to allow it to screw in place. This turned out to have been a failure, as the insert was able to rotate under very heavy load inside the hub, meaning it wasn't turning the wheel at points. I needed to lock off the brass insert to stop it rotating and to do this i just screwed in a grub screw against one of the flats to lock it into place. It seemed to work ok, but not long term.

    3rd fight.
    This fight i wanted to attack a few bots and have some mini fights, so if i found myself against a bot i would try and go for them long term, not just a hit then move on. Sorry Will Stabby McUnicornFace!
    Managed to survive without too many problems, the screw into the hub and gearbox seemed to be loose, so it wasn't ideal but it managed to stay on without causing any binding.
    Some more scratches on the lovely paintwork.

    4th fight.
    That darn pit!
    Yep! i reversed into it towards the end of the 'fight'. I did have good drive and got a few hits on people so i was happy.
    Now to see what the bot is looking like.
    The welding on the front of the wedge seems to have failed with the front tooth on the wedge being lost somewhere, so i will need to refit a new piece, and i may even reweld using MIG the sections again, as in some places i am not happy about the gaps in the Arc welding i did. This is potential weak points that a spinner could expose!

    20190519_164827.jpg

    Lipo fire in the first show battles of heavyweights:
    20190518_180126.jpg
    Last edited by Roboteernat; 28th May 2019 at 16:48.

  4. #94
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    As a result of the wheel fixing problems experienced, i knew i needed to modify how the wheels attach for future comps. Guildford being in 2 weeks time of writing, i needed to work on this quick!

    My solution came from some couplings i made at work for another project. Turned out i could modify them over lunch and fit to some wheels.
    20190528_143519.jpg 20190528_143255.jpg
    In an effort to loose more weight im giving the bike tread and nylon wheel a go too. £2.70 vs £6 for replacements of white nylon to blue rubber so a saving too!
    20190522_143117.jpg 20190528_143119.jpg

    Edit: have just weighed the wheels, and without the bike tyre fitted, currently the new wheel setup weights 154g less than the blue wheel. With bike tyre this could be a saving of about 80g per wheel...?

    Turned down the wheel to a flat, and set to machining the hub, i managed to do one before end of lunch. Nice having access to some tools like this! After borrowing Shock Wills 3/8UNF tap to repair the wheel in Portsmouth, i managed to get some new Dormer ones from eBay and bought a die too.


    To make things parallel i used a 1/2 inch shaft and machined the 3/8 UNF thread onto one end to hold the hub square to the flat on the wheel. making the wheel rotate nicely and not wobble/bind on the chassis.
    20190528_153106.jpg 20190528_143242.jpg
    Final results look nice. I may have to take off some HDPE from the chassis to allow the tyre to fit - these are 125mm diameter wheels too. Thats why i turned down the diameter a bit to accommodate the tread, otherwise i will increase my GC.
    20190528_155322.jpg

    Just need to attach some bike threads now, oh and make a 2nd!

    what would you guys use, Road tread? offroad? or slick?
    Last edited by Roboteernat; 28th May 2019 at 21:47.

  5. #95
    McMullet's Avatar
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    Great write up of the event and the mods to your wheels. Seems like there are as many ways to fit wheels to Argos drills in the world as there are Argos drills. I got around to reading the whole thread, I especially enjoyed the cat posing in the background.

    Was the "team yellow" and "team pink" thing official or did there just happen to be some pink and some yellow robots? I always wonder how you decide who's winning or losing in the FW melee fights...

  6. #96
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    Quote Originally Posted by Roboteernat View Post
    what would you guys use, Road tread? offroad? or slick?
    I generally just use your average 'knobbly' mountain bike tyre, seems to work okay. Others may have used slick tyres etc, but not sure how they found them If you're not fussed about quality or don't mind them being used, you should be able to go into Halfords or other bike servicing places and ask if they have any old tyres going spare in the back. Saves shelling out £25 or so on a new tyre.
    Jamie McHarg
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  7. #97
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    The Exrreme Robots events have had a change around in the way they operate, and now the focus is more team and weight classes collaborating together to win the show. So teams are made of a mix of heavy, middle and featherweights all categorised into teams at random from hat for heavy and mid, and randomly for feathers. The aim is for all the yellow team to win matches to gain points to win the show then ultimately the series of shows in a location. Then overall throughout the year.

    It worked well but yellow team should have won any Al! The feather battle was a bit biased first of all, only 2 yellows went in, 2 emerged but as 5ere were more pink bots in the arena they won lol, it’s all fun anyway! The winner is made by one of the crew who watches over the fights and chooses.

    Funny enoug, I was going to pop into Halfords on my way back from work today and ask, that would be ideal, otherwise I will pop to the tip and see if I can get anything from there. I did get a tyre from a car boot sale for pence, but 5at one is a nice mitchellan brand so it’s better than the ones on my bike currently!

    I’m thinking I may give both knobbly and slick a go and try it out at an event.

    I am working on a mod where I can add a bearing to support the shaft of the Argos drill to stop it having play, which is the cause of those tabs breaking apart where the gearbox locks into the motor. This is a result of having a heavy bot resting with just the 1 fixing point in the gearbox mount. Am hoping it will be a simpler mod than supporting the shaft from the other side.

  8. #98
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    So as I had the opportunity to go to Halfords today I thought I would go and ask if they had any old bike tyres in the bin I could have. Turned out they did have 1. He said weekends are better as they would have more. The guy handed it over to me and I thanked them and left the store.

    Sadly the tyre he gave me was shockingly bare, as in a mountain bike tread made into slicks. Maybe this could be useful, but I thought I needed some tread.
    707D06CE-20F9-4BFA-94BF-FFB32EB4D400.jpg


    Off I pop to the tip, only 3 minutes away from me, and went to have a look at their bike stock. Hooray lots of bikes... for sale. However I did find a single mountain bike tyre which was very old and degrading on the side walls, but beggars can’t be choosers as they say, and off I trot with it.
    56960ED7-4721-475C-89C5-5F349BC25783.jpg

    I only really had today to look for a free one as I’m off tomorrow and and not around for the weekend and next weekend is Guildford.
    Shall see what I can do with this set :-)

    Will search Facebook for old tyres too.

  9. #99
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    I got mine from Wilkos mate. New ones for £7

  10. #100
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    Quote Originally Posted by Roboteernat View Post
    The Exrreme Robots events have had a change around in the way they operate, and now the focus is more team and weight classes collaborating together to win the show. So teams are made of a mix of heavy, middle and featherweights all categorised into teams at random from hat for heavy and mid, and randomly for feathers. The aim is for all the yellow team to win matches to gain points to win the show then ultimately the series of shows in a location. Then overall throughout the year.

    It worked well but yellow team should have won any Al! The feather battle was a bit biased first of all, only 2 yellows went in, 2 emerged but as 5ere were more pink bots in the arena they won lol, it’s all fun anyway! The winner is made by one of the crew who watches over the fights and chooses.
    That's nice! I've always thought it seemed like a long way to go for the featherweights, just for a random 3 minute melee twice a day. At least this way you're participating in the whole show a bit more!

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