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Thread: Deathly Hallows - FW - Alligrater

  1. #11
    04b IIRC is a 6mm chain and 25h works with fine (i can vouch for t8f and 05b 8mm chain). i take it a 13 tooth sprocket ( think that what stock on those motors) so that will require a 65 tooth sprocket (if your going for single stage) which will require a 126mm platewheel. https://www.gearsandsprockets.co.uk/...lex-sprockets/

    or you could use a two stage system which will make it more compact

    I fine THIS website helps with designing a gear ratio

  2. #12
    Took some pictures of the sprocket.

    IMG_20180501_195327.jpgIMG_20180501_195347.jpg

    So it's a 10T and as you see from the chain picture it fits nicely no issues despite low diameter.

    I will need to order the wheel sprocket soon as it is key to the layout. Once I know how it will fit together, I can work out the lowest angle for the wedge that I can get away with.

  3. #13
    One note about those motors. Epoxy the magnets.

    On the gearing design it on cad (fusion sketch up whatever) and see how compact you can get it.

  4. #14
    Quote Originally Posted by Maxamuslead View Post
    One note about those motors. Epoxy the magnets.
    I was told I'd need to glue them in. Any particular product I should look for - something special a thermal adhesive epoxy or good old super glue?

    I found a suitable sprocket on Robotshop, 48T and 0.25" so should work fine. 10:48 will give me 2750/4.8 = 573 rpm
    Still rather nippy but it will be manageable with a tweak to the TX settings I think. It's important I get the drive sorted quickly so I can work on the other systems. If it's a rolling wedge at least I can push stuff, and at 30kph (if my rough maths is right) I could push quite quickly.

    Looking at this sprocket it will go around the fixed axle no problem, fixing it to the heel is another question. Needs to be dead center, probably need to make a tool to ensure I fix it right. Was thinking I would bolt it through the wheel hub. No appropriate mounting holes so I'd make those, and a plate or spacers to keep the plate off the wheel.

    I think a belt tensioner will be essential. Found a few options mostly for dirt bikes.

    Also need to do the calculation for the battery.

    Can anyone tell me how much time is there between rounds typically? Do you get time to top up charge or should I plan for a massive 6S battery or a couple of smaller ones?

  5. #15
    Ocracoke's Avatar
    Team Kaizen

    Can anyone tell me how much time is there between rounds typically? Do you get time to top up charge or should I plan for a massive 6S battery or a couple of smaller ones?
    Depends on the event. Extreme Robots tends to be about an hour or so between FW melees. If Robots Live continues its 1 per show thing, it will be roughly the same. I can have 2x 2S LiFe batteries charged comfortably in that time but I tend to take 2 sets of batteries (4 in total) so I can swap one set out for the other and have the original on charge.
    Team Kaizen - Build Diary for all the robots

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

  6. #16
    Quote Originally Posted by Deathly Hallows View Post
    I was told I'd need to glue them in. Any particular product I should look for - something special a thermal adhesive epoxy or good old super glue?
    Epoxy, i used THIS stuff and it has worked fine (no loose magnets yet) and depending on how they magnets are held in it depends on how you glue them. If you look at Blacksmith Build log the last page shows you the two version i have found.


    Quote Originally Posted by Deathly Hallows View Post
    I found a suitable sprocket on Robotshop, 48T and 0.25" so should work fine. 10:48 will give me 2750/4.8 = 573 rpm

    Still rather nippy but it will be manageable with a tweak to the TX settings I think. It's important I get the drive sorted quickly so I can work on the other systems. If it's a rolling wedge at least I can push stuff, and at 30kph (if my rough maths is right) I could push quite quickly.

    Looking at this sprocket it will go around the fixed axle no problem, fixing it to the heel is another question. Needs to be dead center, probably need to make a tool to ensure I fix it right. Was thinking I would bolt it through the wheel hub. No appropriate mounting holes so I'd make those, and a plate or spacers to keep the plate off the wheel.

    I think a belt tensioner will be essential. Found a few options mostly for dirt bikes.
    Depending on what tools you have and what you are going to use for wheels depends on how you are going to mount it. If you using HDPE i would suggest drill holes through the wheel and bolting to too the wheel, about getting it true, i can see three methods:

    1 Eyeballing it, quick dirty and with the help of a ruler can be accurate enough that it shouldn't wobble too much.

    2 Use a 1” hole in your wheel and a 1in shaft, should be fairly accurate, what i used on my axe mechanism it worked well enough.

    3 Model it in CAD and find a model or make a model of the sprocket us that to make a wheel design and get it cut out.


    Quote Originally Posted by Deathly Hallows View Post
    Also need to do the calculation for the battery.

    Can anyone tell me how much time is there between rounds typically? Do you get time to top up charge or should I plan for a massive 6S battery or a couple of smaller ones?
    ermm I would look at 2700mah + battery what voltage is up to you. I fully drained a 2200mah battery using 550 motors x2 for drive and a MY1016 for an axe (so not contain draw) in 4 mins ish. Michael did you take part in the Featherweight play time at Manchester, if so do you remember how long that match was ?

  7. #17
    Ocracoke's Avatar
    Team Kaizen

    ermm I would look at 2700mah + battery what voltage is up to you. I fully drained a 2200mah battery using 550 motors x2 for drive and a MY1016 for an axe (so not contain draw) in 4 mins ish. Michael did you take part in the Featherweight play time at Manchester, if so do you remember how long that match was ?
    I didn't have a active weapon (much to my annoyance) but I ran separate batteries in The Honey Badger 2 for the drive and weapon for this reason. My 775 motors will go the distance on 2100maH batteries (2x 2S1P LiFePo4 batteries in series) which worked perfectly well... ish.

    I did take part but I wasn't in there for the full amount of time, my batteries packed up about halfway though (wheel was binding on the bodywork causing a major drawdown on the batteries). I think the whole thing was at least 6 minutes from what I recall.
    Team Kaizen - Build Diary for all the robots

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

  8. #18
    The sprockets if ordered turned up. Perfect fit - thank goodness.

    Now to mount them...

    The wheel profile does not have an obvious option. My idea was to make a custom mount out of HDPE that spread the load over the premoulded spokes then bolt the sprocket to this and the mount fix by glue or bolt to the wheels.

    IMG_20180508_190311.jpg

    Above you see the outside and inside profile.

    IMG_20180508_190326.jpg

    The sprocket is perfect, almost matching the hub.

    IMG_20180508_192532.jpg

    The finished mount...or so I thought

    IMG_20180508_191849.jpg

    So it fit snuggly over the 6 spokes and the hub shaft, so I thought I would give it a tap with a hammer to see how tight it was. (Above picture does not show finished mount but for illustration)

    BANG - it shattered into three pieces!

    So I made another, this time with wider slots. This is not going to grip the spokes tight.
    I will glue it in place with the fine two part araldite mentioned above.

    But before I do that I want to fix into it bolts to hold the sprocket in place. I will use the heated and countersunk method, allowing me to fix the nuts on the outside also with some thread glue to stop them moving.

    I also realize that the depth of the mount is too shallow as the revised version sits flat to the end of the raised hub. This gives very little clearance for the chain, perhaps only 3-5 mm, which would be enough if there was no flexing or movement but I think to big a risk, so I need to build a bigger block.

    EDIT: While walking the dog I concluded I will stick with it and buy some 20mm HDPE, perhaps a piece of 30mm too.
    Last edited by Deathly Hallows; 8th May 2018 at 23:18.

  9. #19
    While I wait for my thicker HDPE to arrive, I ordered a 79mm core cutter so the hub will be bigger and more solid. Should give more fixing options.

    Going to start on a wooden prototype to make sure I don't waste the HDPE sheets. I'm not yet sure about the layout of the motors and wheels. I want quite a compact design to allow flexibility in weapon and ensure the wedge is not too steep and the size (and therefore mass) of the body is not too large.

  10. #20
    IMG_20180513_120357.jpg

    Just quick update on the chassis mock up. Using 12mm ply as it's similar size to the HDPE I have but a fair bit lighter.

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