June 23, 2018, 07:52:37 pm
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Messages - zacodonnell

Pages: [1] 2 3 ... 33
1
Progress Reports / Re: Team Ignition
« on: June 08, 2018, 11:38:49 pm »
I find that every time I make a shell I wish the teeth were longer against the shell than the last time. On the last version of Triggo and Tetanus before that they stuck out 1 inch and were 2.5 inches along the shell. Triggo had serious bracing on the inside of the shell right where the teeth attached, but they still dented in from huge vertical hits. Anything less than 2:1 I think is asking for shell buckling, especially without some more internal bracing.

I look forward to seeing how your design holds up. I like the tilted back shape for the vertical spinners. I tried to do something similar and I think it helped a lot. The best bet against horizontal spinners is making it so the teeth mesh (traveling the same direction as the other bot's weapon). The design you have can only work one direction, so I think that is a big detriment.

-Zac

2
Progress Reports / Re: Team Thrasher / Sunny Robotics
« on: May 05, 2018, 10:33:23 am »
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

3
Event Results / Re: Motorama 2018
« on: March 24, 2018, 10:10:35 am »
Reformatted results:
Thanks Joey for entering them and Mike for hosting botrank

Motorama 2018
2018-02-16
0,Denise,Scooter
0,Spark Plug,Scoop
0,Paw Print,Demise
0,Nibbles,Millstone
0,Gimli,Skeeter From Hell
0,Deathbell,Denise
0,Spark Plug,Crabby
0,Paw Print,Nibbles
0,Gimli,Bugfish
0,Demise,Millstone
0,Scooter,Nibbles
0,Bugfish,Scoop
0,Demise,Denise
0,Crabby,Skeeter From Hell
0,Spark Plug,Deathbell
0,Gimli,Paw Print
0,Scooter,Bugfish
0,Crabby,Demise
0,Spark Plug,Gimli
0,Scooter,Deathbell
0,Crabby,Paw Print
0,Scooter,Crabby
0,Scooter,Gimli
0,Scooter,Spark Plug
0,Spark Plug,Scooter
1,The Highlander,Bread
1,Cornerstone,Toxic Envy
1,Vile Ant,Taco Annihilator
1,Robot,Verbal Irony
1,Commander Doom 2,The Patriot
1,Low Blow,Andreas Speed Wedge 1
1,Foiled!,Slim Pickens
1,The Highlander,Hit or Miss
1,Ratfish,Bird Law Intern
1,FireArrow,Odium
1,Cornerstone,Rising Phoenix
1,Hercules,Swamp Woman 2
1,All Defense,Dumpling
1,Physique Black,Angry Accountant
1,Vile Ant,Here

4
Event Results / Re: Motorama 2018
« on: March 21, 2018, 07:36:43 pm »
Magneato's fights look good, and I don't see any errors I know about in the sportsman fights. Thanks for doing this Joey! I can reformat this data to fit the botrank format that Mike posted. I'll plan to get to it this weekend.

(edit: I tried to post the first part of this message in with my phone yesterday but it got clipped somehow. It's the second time that's happened to me. Sorry about that)

-Zac

5
Progress Reports / Re: Team Thrasher / Sunny Robotics
« on: March 13, 2018, 07:30:03 am »
 You are speaking my language. Enjoy the challenge

Zac

6
Progress Reports / Re: Team haciM
« on: March 09, 2018, 11:47:40 pm »
Are you planning to bore or tap the new to shaft? Having tension across the frame plates will keep the whole thing much stronger but working with the ti stinks. Tapping is especially rough so get the right tools for it.

 I am often amazed at the carnage caused in the arena. That bar of yours looked very sturdy, but there is so much energy in the weapons in this class. My shells used to always band at the point where the hub stopped and the top of the shelf started, so I added some gussets there and that helped a lot.  Not really a viable solution for you, but maybe leave a little more meat around the hub? It looks like it been fairly uniformly so that might not be of much use.

Zac

7
Progress Reports / Re: Team Thrasher / Sunny Robotics
« on: March 08, 2018, 08:32:02 pm »
It took me a while to figure out how the whole thing worked, but I think I've got it now. Basically the timing belt on the large rear axle turns a jack shaft in the middle of the bot, which drives a gear pair for the claw. When the claw can't rotate anymore because it grabbed somebody or hit the end of travel, the gears can no longer rotate. This means if you keep rotating the pulley on the back axle the timing belt is stuck, so the top of the timing belt will become a winch cable that pulls the whole arm assembly around the rear pulley/axle.

That's pretty clever! The mechanical (dis)advantage of such a long lever arm means the belt/chain you're using as a tension member better be pretty stout.  As you scale the design up you might have to go to some pretty serious chain to make it work. While I enjoy such projects more than most people, I do have to ask if you think all that chain/pulley/bearing stuff works out to be more efficient than a secondary clamping motor for the claw. Especially as you scale up I think it will be diminishing returns pretty fast.  Can't beat the coolness factor though!

I think you should totally build a sportsman version. When you do, it can hang out with Magneato in a competition for most craziness in the box at once.

Thanks for taking the time to do a build report and picture rundown

-Zac

8
Progress Reports / Re: Team haciM
« on: March 08, 2018, 08:22:29 pm »
You can buy just the mounting blocks for a few bucks each to give it a try. Unfortunately you'll also find testing a horizontal spinner like that in a way that reproduces the issue can be challenging without wishing you had better insurance. How exactly where they coming loose? If you had rear support on the motor, did it pull the motor toward the gearbox or just wrap around the diameter of the can? I can't remember which of the styles your bot had because Alex did something similar on his.

-Zac

9
Progress Reports / Re: Team haciM
« on: March 06, 2018, 10:22:46 pm »
If you're running the 550 motors then the little tiny face screws just aren't man enough to hold that heavy motor in a horizontal spinner. I always add rear motor support (UHMW blocks, foam, etc) to help. Even then I have to tighten them every couple of fights.  I always used the dedicated 550 boxes (there were not either/or models available when I bought them).  In triggo I was exploding the magnets in the motors every fight so I made the entire gearbox and motor assembly shock mounted (including packing the back of the motors in supporting foam) and drove a belt with it. This helped reliability a lot. It's a little tricky to implement though.  The 775 motors have much beefier face screws but also heavier motors, so they have the same issue with the high-G horizontal hits.

I use flathead screws for almost everything. They aren't as strong as button heads for pullthrough, but in my experience heads getting beat up, scraped off, or unscrewed by being reached by the other bot / floor are much more common failures. I've had almost no pull throughs with an aluminum baseplate.

-Zac

10
Questions / Re: Help Finding Drive Motors
« on: March 04, 2018, 09:49:33 pm »
Hi Rsoko, welcome to this crazy game. I'm sorry to hear you're having troubles with your drivetrain. From your description it sounds like you're trying to build a robot to compete in the 12lb combat class, and you're aiming for pushing power over speed, is that right?  If so, 6x kitbots 1000RPM motors with 4 inch wheels would be pretty undersized, and I think you'd run into gearbox and overheating problems.  The good news is that there are lots of options out there for you.

The tried-and-true standard in the 12 and 30 pound class has been the BaneBots P60 gearbox for a while now. It offers a very reliable and compact setup for not too much money. Because it can be used in the 30 pound class it comes in a little heavy for the 12s, but if you're looking to push other bots around and maybe going with a simple wedge bot for this machine it can be a great fit. It also provides you with lots of room to grow in the future as the parts are very common, flexible, and available.

The drive setup is made up of several parts:
Motor - http://www.banebots.com/product/M5-RS550-12.html
There are lots of sizes. The RS550 is heavy-duty for a 12 pound bot, and a little light for an unweaponed 30lber. If you're close on weight then the RS-395 motor is a good choice, but you'll have to get the smaller pinion and the 300 series gearbox version.

Pinion - http://www.banebots.com/product/P60P-GM54.html
This is the little gear that connects the motor to the rest of the gearbox. This requires a small press or bench vise to install as a tight press onto the motor shaft. Because it presses on the motor, the hole in the gear must match the motor shaft. Banebots sells all kinds of pinions - you'll just need to get the one that matches your motor and gearbox choice.

Gearbox - http://www.banebots.com/product/P60S-44-5.html
The gearbox is where all the magic happens. This takes the super-high-speed motor output and slows it way down into something usable for a wheel. It multiplies the torque as it reduces the speed, so a 16:1 box will make it 16x slower and 16x as much pushing power. This ratio is a good fit for this motor and class with a 4" wheel. It would be ok to go with even a little more reduction, like maybe the 26:1 box if you want even more control, but you'll need the 5:1 pinion for that. The banebots gearboxes are custom made with threaded mounting holes and decent shaft support. For a simple setup you can just bolt them to the baseplate and put a wheel on the shaft and go. Of course, it is even stronger to use a pulley on the gearbox shaft to drive a wheel that is mounted separately, but that gets a lot more complicated.

Hub - http://www.banebots.com/product/T81H-RS81.html
The hub goes inside the wheel and is used to link the shaft to the wheel. This hub is made to fit on the stock output shaft of the P60 gearbox because both are a .5" diameter. The square part of the hub locks into the wheel to make sure it turns when the hub does.

Wheel - http://www.banebots.com/product/T81P-395BA.html
Wheels are important too. They have to match the hub you're using to the shaft. This wheel is the closest banebots has to the 4" wheel you mentioned. They offer three different hardnesses for this size, and the one I linked to is on the harder end. They won't wear as fast as the other types and should provide reasonable traction in the arena.

Motor controller - You mentioned that you already have brushed controllers that support up to 4S Lipo, but you didn't mention the current rating. This setup would work well with a controller that can handle around 15A continuous. If yours are rated for less than that you might want to get some bigger ones. The BotBitz 30A controllers are not too expensive and popular, but there are a few others in this size range that work reasonably well. http://ttrobotics.com/botbitz-30amp-esc/
A good alternative is the RobotPower WASP: http://www.robotpower.com/products/wasp_info.html

Hope this info helps!
-Zac

11
Progress Reports / Re: Team haciM
« on: March 04, 2018, 08:54:33 pm »
I can hardly believe a bot that was that solid with so little wasted space was created without a drawing. I sure had a lot of fun hanging out with you at the event and look forward to the next batch of scary stuff coming out of your shop.

-Zac

12
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.

-Zac

13
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:
https://www.youtube.com/watch?v=xKgZECBte_0&list=PLATw5d_vDtZlo3eKnj8lYY-IAC4PkZq3X&index=8&t=0s

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
-Zac

14
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..

-Zac

15
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

-Zac

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