Team Thrasher / Sunny Robotics

[zacodonnell]

 You are speaking my language. Enjoy the challenge

Zac

[rumham]

Here is my Robogames 2018 update for 'Rum Ham' the 3lb undercutter.

Build report:
https://imgur.com/a/ycipMwR

Disk machining video:
https://www.youtube.com/watch?v=Sbn0RFelWXA

[zacodonnell]

That's a fun video. I haven't seen many "how I did it" walkthroughs like it. Machining the motor pattern into the disk is a great way to get a low-profile high torque transfer connection. I've considered something similar with an outrunner before but the can shape is so seemingly random between them (and even between runs) that I never pursued it. I like the way you built in some potential adjustment for the variation.

-Zac

[rumham]

Machining the motor pattern into the disk is a great way to get a low-profile high torque transfer connection. I've considered something similar with an outrunner before but the can shape is so seemingly random between them (and even between runs) that I never pursued it. I like the way you built in some potential adjustment for the variation.
-Zac

This motor pattern was a lot trickier to reproduce than old style. I have to thank Brandon Wiebe for providing the motor model we used for the new weapons. For the old disk I found the motor files on grabcad.com .
--Luke

[Infernaltank]

Thanks for the build report.

Bummer you didn't do well at Robogames but hopefully you'll do well later this year.

[rumham]

Hey everyone. Here's the build report for Rum Ham XXX my featherweight that competed at Moto 2019.

Build/Event Report
https://imgur.com/a/UPk68bX



For more frequent updates like the team on Facebook.
https://www.facebook.com/SunnyRobotics/


--Luke

[zacodonnell]

I enjoyed reading through your build report. It's fun to see somebody else publishing them in this format.  I have to admit when I heard about a bar direct driven off of a motor like that I expected the magnets and shaft to break on the first hit. After reading the build report I see that a lot of effort was put in to keeping those parts alive. It's awfully tough with that much energy going through them though... That bearing mount setup on the blade is some serious kinda project!


You mentioned problems with the Castle controller. I have been running Castle gear on my 30s for a while now and I like the beefy heatsink, data logging, and reliability I've had with them. I did blow the leads off of an ICE-100 one time when a belt jammed at spinup. I emailed the company to get the half-price replacement and they said "it shouldn't do that, we'll send you one for free".  They've been pretty solid since then for me. The data logging has been really useful for motor/battery sizing.

I have also had the experience of scraping epoxy off of motor magnets with a screwdriver. It can be quite a pain if you get it in the wrong place when trying to lock the magnets in . I hope you didn't get pinched when you were working with the magnets - they can be pretty strong in a motor that size.

I like how you start with "Wiring my Rum Ham XXX was a pain" and then later on "Zac's new FBS...glad I didn't have to wire this".  When I read the first comment I thought "I feel your pain" and then hwen I got to the second one I laughed aloud.

Very cool stuff
-Zac

[zacodonnell]

I have very limited experience, but have been pretty unimpressed with the maxAmps batteries. On a heavyweight project with a few of the Canadians we were running them at Robogames a couple years back and they failed way, way before their specs said they would.

Were you able to measure how much power you actually got out of them before they ran flat? I'll bet the peak current draw with the sad motor winding was pretty epic, but in normal use do you know how much it pulls?


-Zac

[rumham]

I have very limited experience, but have been pretty unimpressed with the maxAmps batteries. On a heavyweight project with a few of the Canadians we were running them at Robogames a couple years back and they failed way, way before their specs said they would.
Were you able to measure how much power you actually got out of them before they ran flat? I'll bet the peak current draw with the sad motor winding was pretty epic, but in normal use do you know how much it pulls?
-Zac

Hey Zac,

I actually wasn’t able to use the MaxAmps batteries for the event; I accidently left them on the shuttle bus at the airport. Fortunately my buddy Pete had extra batteries for 60 Seconds of Glory that fit. These batteries were Turnigy Graphene 2200mAh 4S 45C. Running at 8S instead of 10S helped put the weapon in the 200mph range. During safety the tachometer said it was spinning at 205mph so we just had to bump the throttle down a tiny bit.

I’m not really sure how much current the weapon usually draws. I was surprised to learn that the Castle Talon 120 HV does not have data logging. But it draws a lot of current. My match with Crippling Depression lasted 47 seconds and the weapon spun up only three times. After that match the battery charger put in 750mah worth of capacity, so the batteries are way undersized.

I’m working on ways to reduce the current draw and or increase capacity without building a new frame. I have extra weight and width to spare but not length. Higher capacity batteries seem to all be around 130mm long and I just don’t have room for that. I’m currently looking at the https://www.maxamps.com/lipo-2800-5s-18-5v-battery-pack as it’s the highest capacity battery I can find that’s ~108mm long. Compared to what I was running at moto 2.8AH@10s should give me about 59 percent more watt hours of power. I would still have to keep the weapon spinning around 200mph for an apples to apples comparison. This still wouldn’t be enough power to run three minutes hard but it would be better than what it currently is. Ideally I would rewind the weapon motor to a lower KV so at 10s input voltage it naturally spun the weapon at 200mph (vs 300mph) but I’m not sure I’m ready to take on that project. I have a blown weapon motor so there’s not much to lose other than the time it takes to rewind the motor.

I’m also considering running the drive off its own battery. I think I can get another small battery and power switch to fit in the bot if I replace the massive drive VESC’s with some hobbyking 80a ESC.

--Luke

[zacodonnell]

The SimonK red brick 70A controllers have been rock solid for me on drive in the sportsman. I'm running 4x Afro 30A escs in Hyperpolarized (with four motors) and it is way faster than the shell drag will let me control. They don't even get warm.  It sounds like you're way overkill on your drive ESCs to me, and that should free up space as you say.

I feel your pain on fitting stuff in. Darn this optimization stuff..

-Zac

[rcjunky]

agreed, running a small lower voltage pack for drive with rb70's or aerostar 60's if you run 4s should result in more reliable drive. I know I complain a lot about running dual voltage since it adds a lot of wiring, it is great for some things.

[rumham]

Hello Robot Builders! Here's the build report for Rickety Cricket my 6lb gyro walking beetle

Build/Event Report
https://imgur.com/a/8MFkRu6



--Luke