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Thread: Team Darklight - Featherweight Axe/Hammer diary

  1. #21
    The weight of the axe head does play a factor. However a heaver head is harder to swing, takes longer to accelerate, will have a lower top speed, and caused the robot to jump more when compared to a lighter head. Its a trade off between mass and speed and it will depend on what kind of axebot you want.

    A 3-Phase driver is an ESC, and pretty much all hobby brushless motors are three phase. Rory is more or less right about the issues with brushless and how they technically have no start up torque at all. This can be partly solved with sensors and smarter Firmware on the ESC's; you may have heard of SimonK, BL heli and VESC's, but as you will have seen in Robot Wars, reliable and affordable brushless controllers that can match the very mature brushed setups people use are not quite ready. This is less of an issue in FW's and lighter classes but the fundamental issues with brushless motors are still present.

  2. #22
    So, an update...

    Work on the bot stalled for a bit due to things, so it's a bit behind...

    Today, we looked at working out the logistics of the axe with the new scooter motor. We have a chain/sprocket setup ready to fit, and now need to work on the mods to the bulkheads to fit new bearings and hubs, etc.

    Also on how we are to power the thing. I had originally intended to use a TZ85A ESC for the weapon, which may be OK given ratings but it is close to the mark given it maxes out at 6s, or ~24v. I know Hatchet used a Victor 885 at one point for the weapon based on the build diary - are there any other good ESCs out there as alternatives?

    At this stage I anticipate it will be overweight, so also looking at where we can save weight in the overall design to accommodate this new setup.
    Last edited by qbnut; 14th May 2017 at 21:17.

  3. #23
    Haven't checked the forum in a long time so I've only just read this build diary.

    A Tz85 will run a scooter motor no problem, I've used one in Hatchet before and it was fine. With regards to the Victor, Hatchet did use one for 2 years and it was fantastic. They're difficult to find now though hence why I swapped to a Tz85.

    What reduction and chain pitch are you using btw? Hatchet now uses 8mm pitch chain on a 10:1 dual stage reduction, earlier versions were a single stage 5:1 reduction.

  4. #24
    It's a 6:1 reduction single stage. I'm using 6mm chain pitch as it's what the motors sprocket came with. We'll have to see how that goes

  5. #25
    We took the bulkheads back out today to take the now abandoned first weapon system off, and laid some parts on a scrap bit of board to check positions for the new one (I have already worked out it all fits in Sketchup)

    Also working out the drive motors mountings which is a work in progress.

    Looking like this it seems a bit like we've done less than we actually have!

    received_10210984035611030.jpeg
    Last edited by qbnut; 21st May 2017 at 22:03.

  6. #26
    Looking good
    what wattage of motor are you using ? and have you modeled it in Sketch up yet ?

  7. #27
    Kashei uses a NTM5060 370KV motor on 4S , combined with a SimonK software TZ85 to power the axe (fancy selfrighter actualy)

    We have stripped mod 1, mod 1.5 and mod 2 gears with that combo.
    But the motor doesn't go over 35°C on a warm day, and the TZ85's doesn't even care.

  8. #28
    6mm chain is a tad on the thin side unfortunately, I used it on the first Hatchet because the motor came with a 6mm sprocket, even though that was a relatively low powered set up compared to later versions I was still snapping chains every fight. By all means if you have it then use it, but just be aware it probably won't hold up for very long.

  9. #29
    What type of chain do you use now Sam ?

  10. #30
    Quote Originally Posted by mrsam View Post
    6mm chain is a tad on the thin side unfortunately, I used it on the first Hatchet because the motor came with a 6mm sprocket [...] I was still snapping chains every fight.
    I might have to take the advice of experience and beef it up then by the sounds of things! Of course that's going to be easier to do now rather than later.

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