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Thread: Build Log - Bread Dead Redemption (FW) - First Build.

  1. #61
    Great write up, and great to meet you and see BDR yesterday! Congrats on your victory again and on your performance throughout the day. Those dustpans were amazingly effective, especially at scooping up Wedgeley - seemed to spend a lot of time with either our bottom jaw or a wheel stuck in there!

    Is this the Sabretooth ESC you have? If so, it might struggle a bit with two drill motors on each channel. As James says, to run two motors per side you'd just connect them together in parallel to the same channel of the ESC, either by connecting both into the same output on the ESC or making a separate cable to common the reds and blacks. However, 12 A might be a bit weedy to run two motors - the FeatherTwo (which was designed for this type of motor and application) is spec'd for 30 A per motor continuous and 80 A burst. I'm sure that's a bit OTT, but a quick read around suggests "normal" current from a 550 size motor at 12 V is of the order of 10 A. That means there's a fair chance two in parallel will be drawing 20 A a fair bit of the time, especially overvolted with a 4s battery, and you'd be over 100 A if two motors stalled.

    In theory, the Sabretooth has overcurrent protection but I wouldn't rely on that save itself, plus if you trip the current limit the drive will cut out and leave you sat there like a muffin.

    Regarding tank steering, it says on the Robot Shop site that the Sabretooth "... comes with options for exponential control, autocalibration and built-in mixing. The operating mode is set with the onboard DIP switches ..." So to control the two channels independently, you'd just need to find from the manual which of the DIPs sets the mixing and switch it off - if I'm reading that right. Then you'd have independent control of each channel.

    If you want tank steering and two motors a side, these are OK and not too pricey. We have one running the weapon motor in Ensign Crusher and I believe Chris has one driving each pair of motors on Luna-Tic.

    Edit: forgot to say, good luck with the updates!
    Last edited by McMullet; 2nd December 2019 at 21:43.

  2. #62
    Ocracoke's Avatar
    Team Kaizen

    I am gutted I wasn't there for this one to see your bot in action, I had Azriel running for this and all. Anyway, well done on your first event!

    Upgrade from a 3s lipo to a 4s, overvolting the motors. More power.
    Yup, I'd go for this. 14.8v over 11.1v should make a bit of difference in terms of speed and power.

    Ditch the plan of adding an axe and put the spare weight allowance to making the robot 4WD. I'm not sure how to do this with the Dual Sabertooth ESC. Would it be possible to wire two motors together on each side and wire them in to the ESC that way, or would that blow the board? Either that or rig up some drive pods with gears so one motor drives two wheels. I'm not sure yet.
    The simplest option is to, as James said, is to put a motor for each wheel in and put them in parallel. I did this with my first Middleweight Kaizen, worked fine but you do need to ensure your ESC can handle it. If your ESC is a 2x25 then I suspect that might be OK though I would recommend putting a fuse per motor in (20A) to prevent the motors from stone killing the ESC and themselves (as I found out).

    I would like tank-style steering. It's what I'm used to and just using one stick was proving difficult at times. Again, whether this is possible with a dual ESC, I don't know.
    If you mean like a RC car, then yes, you'd want to move your elevator channel to the rudder channel for steering. If you wanted full tank like control, you'd need a different transmitter (one with both sides where the up and down movements are sprung on it) and then turn off the mixing on the ESC, which you can do on the DIP switches. I happen to have one as it goes, might be persuaded to part with it.

    Custom made dustpan (will have to happen eventually), or reinforce the current ones. I'm contemplating a Sawblaze style 3-prong pan, but I'm not sure that is needed for now. I'll have a think. The pans held up reasonably, but they may need replacing and modifying if I keep them as is.
    Yeah, I'd get the internals "right" first before remaking the body. If you ever wanted a hand in doing this, quite happy to help.
    Last edited by Ocracoke; 3rd December 2019 at 14:56.
    Team Kaizen - Build Diary for all the robots

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

  3. #63
    It was great seeing you and Bread Dead for the first time! Definitely one of my favorite events this year.

    Your Sabertooth should be okay by my reckoning. Boring Wedgebot uses a 2x12, which is absolutely not up to the task. The current limiting has kept it alive for... nearly a good 7 years now (part of the reason I've not been able to justify getting a new one) but is also a factor to its twitchy performance; even when it does get grip, that then overloads the ESC, but can never kill it..... long story short don'y use a 2.12 kids Your 2x25 looks alright as long as you don't push it overly hard.

    I'm looking forward to seeing how it comes along for the next Dojo, if you ever want a hand with anything, I'm only down the road in East Manchester) Good luck with it mate!

  4. #64
    Thanks to all for your comments and feedback. I'm still buzzing a week later!

    Based on what you guys have said, I've got all the parts on order to redo pretty much all the electrics for 4WD. So much for prioritising, eh? Hopefully shouldn't be too bad now that I've had a bit of experience. Praying that my measurements are right and it all fits, because it's going to be a tight squeeze.

    Sam is correct, BDR runs off a 2x12. Based on what Theo said, that may explain the total lack of pushing power last weekend if the ESC overcurrent protection was constantly kicking in.

    If you want tank steering and two motors a side, these are OK and not too pricey. We have one running the weapon motor in Ensign Crusher and I believe Chris has one driving each pair of motors on Luna-Tic.
    Cheers for that, I've ordered 2. I've also got a Flysky FS-I6X and 2 new motors. In order to fit everything in, I'm dropping back down to 100mm wheels from 120. This means I've ordered new mounts from Nat with the center to base height reduced by 10mm. The smaller wheels should mean more torque too.

    Should be a big improvement, if all goes well!

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