February 25, 2018, 12:58:21 am
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Messages - zacodonnell

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Progress Reports / Re: Revelation Robotics
« on: February 22, 2018, 08:26:38 pm »
Adam, did you ever get this sorted out? If two different controllers had the issue then you're probably right - somethings up in the wiring harness.


Progress Reports / Re: Team Brain Damage
« on: February 22, 2018, 08:24:44 pm »
Motorama was a great time. As far as I know pretty much everybody who was there had a blast. There weren't any arena breaches this year and there were a few surprises from some new machines - especially the rookie bot BEAM.

Magneato did better than it ever has before. The large ground clearance and exposed wheels helped it get out of a few sticky situations and the clutch worked flawlessly in all but one fight. In that fight the issue was a bearing slipping out of the press fit inside the flywheel assembly and holding the clutch plate away from the flywheel. That made me not be able to flip so when I gyro'd over I was dead against Brutalizer.

Playlist of all the fights:

Some notes on the fights: I haven't actually had time to watch them yet. There is a little profanity in at least one when I end up upside down and I think the bot won't be able to flip back. Turns out the failure to flip earlier in the fight was the flywheel not being up to speed so it did work, but I thought I had just lost the fight like I did against Brutalizer.

Here's are some thoughts on the overall performance of the machine:
1. The ground clearance and brushless drive setup were fantastic. This was the most mobile bot I've ever had, and it was a blast to drive.
2. The gyro effect from the flywheel was much more pronounced at this tournament than ever before. This bot is about 10 inches narrower than the friction roller clutch version, and with the extra drive speed I gyro'd over frequently. I have the steering turned down to 30%, but bouncing off of other bots was a big issue. This seriously hampered my ability to be aggressive and will be something I need to fix in the next version
3. The sensors on the arm worked great. The soft 40A bumpers I'm using survived every fight (though I replaced them each fight). They prevented the rear bar from becoming too bent to be usable and stopped the robot from ending up upside down on a missed flip. This helped a ton for me to go back after the opponent if I missed. It also made the self righting super reliable and kept enough energy in the flywheel that I got 2.5 attempts to self right without spinning the flywheel back up. 
4. The LED feedback was useful. I could see when the arm was having troubles (flashing red) and get a little more patient on my triggering.
5. I can probably shorten the soft-start window on the throttle after flipping. It's a linear 4 second ramp-up right now after a half-second delay. I think I could cut that in half and flip faster without overloading the motor.
6. 4600 mah is a little more battery than I need, but not a LOT more. In the highest fight I put about 4000 back into the packs. I think it's the right amount of margin - if I bound up a drive side I would have eaten the difference for sure.
7. Shock mounted, compliant armor works great against hammers and saws. I think I'll thin out the top armor and do some flexibly-mounted super thin ti as a standard setup next time. Pitter Patter hacked straight through the hard-mounted 6061 baseplate in about a half second, but barely scratched the spongy ti over my batteries.  He did peel the insulation off of the weapon motor wires though... Man was that close
8. I'm wasting a lot of energy in the flywheel by having the frame flex enough when I fire that the flywheel scrapes the baseplate. I have the scratches and high speed video to prove it. The next version will include some way to prevent that, and I think it'll provide even faster flip timing and self-righting.

Future thoughts:
1. Being dead when I'm upside down until I can spin up sucks. If I can swing it I'd like to include full invertability in the next version. Not sure yet whether that will be a stack of wheels, a couple of big wheels, or something else.
2. I am toying with some ideas on ways to make the flywheel be horizontal to avoid the gyro problem altogether, and I think that could be totally awesome. It will be more complicated though.
3. Being under the other bot's center of gravity makes the flips more spectacular. With the change to the sportsman rules to allow limited wedge shapes I'd like to be able to do a better job with this.
4. There are a few things that I think the onboard controller could help with, like some kind of sensor to tell it when to flip and maybe some kind of internal rpm sensing on the flywheel. I've toyed with each in the past but want to do a bit more in the future.

Thanks to all who made the event so awesome

Progress Reports / Re: Team Tamper Resistant
« on: February 13, 2018, 09:38:41 pm »
I like electromagnets :)  I've been trying to use them in my bots for years.  The best-working friction roller clutch I had on Magneato used electromagnets to capture the mechanism and springs that spring it into engagement when I turned them off. It was a little tricky to get right but drammatically reduced the firing reset time. Pretty complicated though..


Progress Reports / Re: Team Cosmos
« on: February 13, 2018, 09:36:01 pm »
I really enjoyed that!

I think the pin sandwich should work well. When I made Scurrie I found there actually was a lot of force driving the blade off the end of the shaft, so the little bit of meat you have above the nub is a concern. When the blade hits a wedge it tries to torque it pretty hard and that can really push down on your pin. It's even worse when you are upside down and it hits a wedge and the whole blade wants to rip off the shaft with no floor to help convince it otherwise.  I've never built an ant so I can't say whether that will be enough material.

I noticed that your pins aren't a press fit in the shaft, and they appear to be solid instead of some kind of roll pin. That should make them easier to put in and out. I hate dealing with roll pins :)  I feel your pain on tapping the steel. The holes in the top of the shell on Triggo were all tapped 6-32 screws, 24 in all. I used four taps to do it because I was afraid of breaking one. It was annealed 4130 but it still sucked.

This is gonna be fun


Progress Reports / Re: Team Tamper Resistant
« on: February 11, 2018, 06:07:48 pm »
I think I get it. #1 looks a lot like the toggle point on a four bar linkage. At the toggle point, the force could either cause it to expand or collapse depending on whether the rear-most pin goes up or down. I think time in this state will be very hard on the mechanism so making a successful transition will require going through this state quickly. If you don't, a lot of energy will be spent trying to compress the linkage / stretch the longer bar. You'll have to make sure that there is no load on the system from the opponent near the transition point by tuning the length of the slot in your original image.

It would be cool to see in action, but my guess is that at the speeds you'll want out of the flywheel that transition point is going to be hard to avoid. Is there a way to limit that issue?


Progress Reports / Re: Team Tamper Resistant
« on: February 10, 2018, 07:48:36 pm »
Apparently I missed this post in July about a flywheel powered flipper linkage. I am only barely able to visualize what you're talking about, and would benefit from a couple of images of a partially engaged state as well as the freewheeling and fully engaged images you provided. It sounds like a neat project indeed. I know I'm a little late to the party, but did you ever happen to build a mockup of it?  Even if you represent the flywheel as just a stack of watercut parts to see if the mechanism functions in a manual model would be very cool.


Progress Reports / Re: Team Brain Damage
« on: February 10, 2018, 07:39:27 pm »

I did the last bits of maintenance on the bot today. Replaced the rope, cleats, return bungee, and bumpers. I also made spare bumpers (I have lots now). I'm hoping the sensors drammatically reduce the need for me to swap bumpers every match, but they're not that expensive or difficult so I figured I'd have extra. I still need to swap the new wheels in. These are looking pretty rough after my testing. My plan is to organize my stuff and paint stuff tomorrow morning, then pack it all up in the evening.

I'm very satisfied with the self righting even at low flywheel speeds. I think the sensors are the big difference maker there because they ensure it goes to full extension regardless of how long the magnet has to be on. The flips in the video are so-so but the target is backed right up against the test box wall so there isn't really anywhere for it to go. The angle of the flips is definitely more forward than up, but it makes for some good shots into the plastic in front of the judges :)




Progress Reports / Re: Twisted Sick Robotics
« on: February 10, 2018, 07:20:15 pm »
It's looking really mean. Are the frame rails .25" 6061? With the standoffs I'll bet it is really stiff and solid when you tighten it all down. Mine is like a bowl of spaghetti in comparison :)


Progress Reports / Re: Team Brain Damage
« on: February 08, 2018, 10:22:14 pm »
More fun with cleats tonight. The shorter cleats work fine once I cut the outriggers off. In fact, in one of the tests the robot actually leaps forward after flipping the target. I'm not sure where that reactive force came from unless it was spring tension built up in the frame... Any thoughts? It makes for a cool flip though :)




Progress Reports / Re: Team Brain Damage
« on: February 07, 2018, 10:12:21 pm »
I got the new cleats cut out and mounted tonight. They came out ok, although I didn't have time to test them yet. There are a couple of things that might make them more effective but I want to watch the video before I try anything else. I took some pictures and also uploaded a few of the frame modifications I did before.



Progress Reports / Re: Team Cosmos
« on: February 06, 2018, 09:53:27 pm »
Also this brings back memories of the first ever robot video I saw online.  It took a whole night for me to download a 20 second clip of hazard hitting a shopping cart. Thanks for the flashback.


Progress Reports / Re: Team Brain Damage
« on: February 06, 2018, 09:45:57 pm »
I think I traced the drive issues to a loose receiver wire on that drive controller. I was able to reproduce it by tapping on the wiring harness / controller while trying to drive. At first I thought it was something internal to the controller, but when I went to swap the controller out I found an untaped rx wire extension in the chain that had the connector mostly pulled out. My extensions have a little plastic clip that is supposed to hold the parts together, but I always tape them anyway. Looks like that's a good plan as this one appears to have separated just from my test flips. I got it put back together and could no longer reproduce the problem on the bench.

I moved on to planning out the updated cleats that will hopefully not bend the frame as much. They're going to be angle brackets that share the load between the front and side rails and extend much less far from the robot. I'm hoping that with good cleats I can actually cut the outriggers way down, which would give me better reach on the opponents as well as providing the weight for the beefier cleats. I'll work on that tomorrow or Thursday. With any luck the snow will force work to cancel :)


Progress Reports / Re: Twisted Sick Robotics
« on: February 05, 2018, 09:05:51 pm »
What adhesive did you use? And how much diameter did the tread add? They look grippy :)

When my drive setup is working, it's way more power than the wheels are putting down. I long for more traction, but don't have any weight or time to do something like this. Perhaps next time if it works well I can, uh, rip off? your design


Progress Reports / Re: Team Cosmos
« on: February 05, 2018, 09:03:14 pm »
This is gonna be great! I have brought a shell spinner to Motorama I think every year since 2004. There's some sweet irony in the fact that 2004 was the last year Killabyte competed there, and that I am unable to bring Triggo this year. It's like the essence of the shell spinner is passing back and forth :). I'll definitely be rooting for it to put on a good show.

Can't wait to hang out with everybody


Progress Reports / Re: Team Brain Damage
« on: February 05, 2018, 08:57:39 pm »
I agree, it is being a bit frustrating. I didn't have any time to work on it last week either. If I can't get it to be pretty reliable before the show I'll swap the old setup back in and try again next time. My biggest fear is thinking it is working and having it flake out on me during a fight.

Hopefully more to come on this tomorrow night.


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