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Messages - zacodonnell

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16
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

17
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

18
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

19
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

20
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

21
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

22
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

23
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

24
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?

-Zac

25
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.

-Zac

26
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 :)

Pictures:
https://plus.google.com/photos/107279152885550274671/album/6510901572747399649/6521088089889470914

Video:
https://youtu.be/uZRkuOkTNMA

-Zac

27
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 :)

-Zac

28
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 :)

Video
https://youtu.be/7al5lmLHymM

Pictures:
https://plus.google.com/photos/107279152885550274671/album/6510901572747399649/6520388756132149346

-Zac

29
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.

https://plus.google.com/photos/107279152885550274671/album/6510901572747399649/6520015569117808946

-Zac

30
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.

-Zac

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