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Author Topic: AmbiSinister  (Read 5189 times)

MDBuswell

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Re: AmbiSinister
« Reply #15 on: January 11, 2016, 09:19:03 pm »
The Snap Hubs wouldn't work stock because the shaft that sticks out is far too short to get any real bite on, and the adapter that comes with the motor is 5mm wide apparently. At least according to HobbyKing, which I only barely trust. I actually have a foam wheel from Fingertech as what's turning the shell currently, so the snap hub would be good to use. Though it honestly may turn out to be a bit too wide as the wheel isn't much bigger than one and I'm up against the shell as is. I think the blade adapter hub is 1" wide? That's a bit tough to run as my wheel is 1.25" wide and I'd rather not have metal that close to the shell. There was a suggestion of trying an M5 bolt and seeing if that is the same thread pitch as the adapter and then just using a lock nut on the thing.

For the bolt, last time I did run a normal bolt and put the bearing (Part of why I wasn't happy with things, a single bearing let it wobble regardless) straight on the threads. This time I'm trying to minimize the rock it has by doing things proper. Didn't even think that the shaft on a normal bolt wouldn't be precision ground, but it makes perfect sense. I'll see if I can find something that'll work, I'm fairly certain I need a 3 or 3.5" Bolt and have no issues with putting it in threaded side down as long as I can run a nut up to the bottom of the shell, or have a shim of some sort holding it up. Definitely something I gotta change!

For now, MassDestruction is the easiest thing for me to make living in Mass and having a job that seems to be unable to function without me for any period of time. Last time I took two days off we ended up losing my coworker and having a great melt down all over the place. But one of these years I was hoping to build a 12 or 30lb bot and come to Motorama. Looks like an amazing time and it's close enough that I wouldn't have to take a full week vacation to attend. Just need to find a new coworker so I'm not solo in the department anymore and I can think about taking a day off here and there again. But sooner or later I'm sure I'll get to meet up with ya!
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

zacodonnell

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Re: AmbiSinister
« Reply #16 on: January 12, 2016, 07:28:54 am »
A shaft collar would probably work well to locate the shell on the shaft.  That way the threads can be inside the base and the shoulder would be the only thing that sticks out. Those bolts only have about a 5/16 thread length.  You might want to put some plastic washers or maybe even I thrust bearing from stock drive products between the collarvand the shell to reduce friction

Zac

MDBuswell

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Re: AmbiSinister
« Reply #17 on: January 12, 2016, 11:22:16 am »
Yeah, I realized that when I ordered them. I have some UHMW shaft I may cut to length and drill through to space it out. It won't have to be very long because I have a top plate on the bot that it'll rest against. I also have thrust washers to put above and below the shell as well to make sure there's plenty of give, though they didn't seem to give very well when I tightened things up by hand. So it seems I'm still best off doing a bit of preload and not really tightening it down. Hopefully the bolts will be here tomorrow and I can go from there. Thanks!
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

zacodonnell

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Re: AmbiSinister
« Reply #18 on: January 12, 2016, 01:07:56 pm »
I was thinking a thrust bearing like part A 7Z 7-025 from http://sdp-si.com/eStore/Catalog#  (search for it in the box at the top left). Mcmaster has all metal needle roller thrust bearings I use for this same thing in all my bots, but the min shaft size is .5" so your .25" bolt won't work for that. Not sure how the plastic one will hold up, but I bet if you put metal washers on either side instead of the plastic ones, the balls will hold up pretty well in a small bot. It would greatly reduce the resistance on your shell. Plastic washers (especially a stack of a bunch of thin ones) will work ok too, but not as well.

-Zac

MDBuswell

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Re: AmbiSinister
« Reply #19 on: January 12, 2016, 09:00:58 pm »
Yeah, those are similar to what I have. But mine did come with metal washers to them. I put them on and spun up by hand and they felt very tight, but that could have just been me. I haven't dealt with much of this before. It's all a learning experience!

https://drive.google.com/file/d/0B_IPn7qcHqNONGJ3MlVtMmMtY0E/view?usp=sharing

And here's a view of the two bearings I've got attached to the shell currently. Much happier with the beefiness that it looks to have.

https://drive.google.com/file/d/0B_IPn7qcHqNOWlplWGNWemlyWlk/view?usp=sharing
https://drive.google.com/file/d/0B_IPn7qcHqNOdUtiUlhCdHVrZmc/view?usp=sharing
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

MDBuswell

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Re: AmbiSinister
« Reply #20 on: January 26, 2016, 10:18:50 am »
Well, the bearings worked out well. Everything could be locked down and the shell still spun. Definitely a step in the right direction! We went 0-4, lost all 4 batteries when getting flipped and the shell coming close enough to put marks on them. Throwing them away because I'd rather spend another $10 than take a chance on it blowing up eventually. But it was a fun time and there was tons of space around.

Now if only the shell was even remotely balanced. I spent the entire tournament upended and doing nothing but twisting the bot around the shaft instead of the shell. The old one used to self right by being unbalanced 2wd and would kick itself back onto it's shell. At least in the 2 fights I was able to do that for it. But this time the new chassis had the shell almost an inch higher off the ground, and the 4wd set up was balanced enough that it didn't kick itself off kilter. Silliness!

Moving onto the next redesign I'm still deciding whether it's worth it to continue trying to use this shell (Really leaning away from that) or trying to shrink the bot even further to use the smaller possibility I have for a shell. It's much thicker and aluminum, but also a smaller diameter. Also, it's a octagon and not a bowl, so friction drive would be out and I'd have to switch to pulleys. Not the end of the world if I can figure out how to mount one to the weapon motor. Being an octagon, I have a much better chance and balancing things off the bat instead of being off like this one was. Flat sides help with mounting teeth, and the center hold should actually be in the center this time. BUT, this bot is on the extreme side of compact as is, and I know it'll be a struggle to squeeze all the guts in an even smaller package.
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

zacodonnell

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Re: AmbiSinister
« Reply #21 on: January 26, 2016, 11:47:29 am »
You may consider using the friction roller to rub on the top of the shell instead of the side. It's more resilient to dents on the side, works even with an octagon shaped shell, and allows you to lay the weapon motor down to lower the height a bit (potentially)

I went through 3 shells before I could hit anything without breaking the shell. It takes a while to get it right.  Pete Smith used a prop balancer setup to help him balance the beaters on his three pounders, you could do something like that with your shell if you wanted. I've always wanted to try it but never had a setup that could handle an 18" diameter shell :)

-Zac

MDBuswell

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Re: AmbiSinister
« Reply #22 on: January 26, 2016, 01:30:16 pm »
Hmm... Decent idea with the roller. I never thought of that. With my current shell, it wouldn't really work as the shell has a very small diameter at the top. My main thing from the friction drive was an easy way of gearing down the shell. The motor is a 2150KV, and at 11.1V, that's 23,865RPMs. Bit too fast for a nearly 6" diameter shell. So the wheel I was using was probably about a 4.5:1 gear down, so the shell wanted to spin at 5,303RPMs. Seems more manageable to me. The top is maybe 2" in diameter, so I wouldn't get really any reduction at all because the motor is just over an inch in diameter. But with the Octagonal shell, it would be able to spin up there because that one is flat topped. So that is an interesting option to chase if I decide to change up the shell for a completely new design, or just start over with the other bowl I bought. The motor is also insanely short, at least in my untrained opinion. So I'd actually be increasing the height flipping it on it's side I believe. But if it works better, than it's always worth doing.

I may try the balancing thing. I think we actually sell lawn mower blade balancers here too, and that could achieve the same thing I think. I'd have to look at how it works to make sure I could mount the shell into it. But I was getting several comments about making the teeth much smaller. So most likely the current shell has spun it's last. But if I remain a glutton for punishment and keep trying to do a home brew shell, that is a much better idea than just winging it like I have been. The funny part is, it seems to take the hits perfectly fine which is exactly what I thought it wouldn't do. It's just any wobble sends the thing up onto it's top, and this version refused to self right like the last one did. So I either go back to 2wd and hopefully self righting, or I gotta put something on the top of the shell so as to make it unable to balance on it's lid.
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

zacodonnell

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Re: AmbiSinister
« Reply #23 on: January 26, 2016, 05:49:03 pm »
I had terrible problems with "break dancing" on my robot Steel Shadow. The center of gravity was just way too high on that bot. Yours looks pretty low so it could just be a balance problem.  I had a 90 degree bent pipe "tail" on top of the bot to show me the front and help it self right. The tail actually made it flip upside down even easier, but ensured that it would come back. I eventually redesigned for a much broader 4 wheel drive base and lower center of gravity with no ability to self right and was much more effective with the bot Tetanus.

The prop balancer would work well if you used your piece of drive shaft through the shell to go on the prop balancer I think. Not sure what a lawnmower blade balancer does but if you have one on hand it is certainly a candidate. Call it a case study :)

-Zac

MDBuswell

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Re: AmbiSinister
« Reply #24 on: March 02, 2016, 10:08:06 pm »
So, I decided to give 3D printing the chassis the old college try. Figured that if I could pull it off, it should be the better idea for this bot. The frame doesn't see outside abuse to I theoretically can strengthen it where the center shaft goes and have a decent design. So, I tried. Not sure if I failed yet. I had it printed at Shapeways because it was quick and easy to set up, though I don't know if there's something better to get it made out of that would be stronger. The motor stanchions don't seem the strongest, but I seem to want to over strengthen everything, so I'm tempted to let it go and see what breaks. It does fit inside the shell, though barely. Apparently fitting an entire antweight in a 6" shell is harder than I thought it'd be.

https://drive.google.com/file/d/0B_IPn7qcHqNOcmdQWUFTN29jaEU/view?usp=sharing
https://drive.google.com/file/d/0B_IPn7qcHqNObmswUjIxX2xHS00/view?usp=sharing
https://drive.google.com/file/d/0B_IPn7qcHqNOd1BXdE1ER0ktZ00/view?usp=sharing
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

zacodonnell

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Re: AmbiSinister
« Reply #25 on: March 02, 2016, 10:11:12 pm »
It looks pretty decent, but you're definitely going to want more clearance on the shell.  The hexagon style shell is not as space efficient as a round one, but it is a lot easier to make / find.

I say put it in a test box and slam it into a brick a bunch of times to see what breaks. It's likely that most of the parts will survive whatever the failure is, and if you're lucky you might be able to spot it with bending/discoloration before it goes really bad :)

-Zac

MDBuswell

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Re: AmbiSinister
« Reply #26 on: March 02, 2016, 10:15:52 pm »
Yeah, it looked good on the CAD. But holding it, I wasn't happy. I'll probably give it a go anyways and see what happens. But I don't think I'll stick with it. I actually have a somewhat crazy idea to save some space. I'm just having trouble getting it straight in my head. And I haven't crossed the threshold with CAD to be comfortable enough to do something in it that I can't imagine in my head prior. Thanks for the suggestion though! We're gonna give it a go.
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

MDBuswell

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Re: AmbiSinister
« Reply #27 on: March 06, 2016, 01:39:20 pm »
Well, try as I might, I can't convince myself to use the octagonal shell. So, we're back to the bowl I was using before that held up fine. It's a bit taller, which is what I wanted to get away from a bit, but it's gonna work better in the long run.

I did do a quick test fit of components and I'm pretty happy with where everything seems to land. The wiring is going to be fun to do, but theoretically the left side has a space for the weapon ESC and then the top place for the drive ESC's, so it should be straightforward once I get going on it. As long as the battery slides into it's home I am all set. I did design up a rin for the bottom of the bowl to be the teeth instead of the way I had things done before. I like this much more. I just have to find a local place willing to machine these out or steel for me. I should be coming in way under weight with this one I think, so I'm stoked about that. I had 7 ounces for the shell and the bowl is just over 2. So the ring can be 5 ounces and I'm still underweight.
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

MDBuswell

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Re: AmbiSinister
« Reply #28 on: April 25, 2016, 09:07:08 am »
https://www.facebook.com/Damned-by-Design-218960218447295/

I have tried building a new shell for the bot, and failed once again. Things were all put together yesterday but spinning up to anything that resembled speed had it flipping around again. When I took the shell off I could see that the tire was grabbing better on one side, which tells me I screwed up the center hole again. I'm not quite sure where to go with it from here. I'm going to try and better center the bearing to get the shell even and see if that helps. But I'm not positive I'll be able to get it to work. I know the teeth are better balanced because they are mass produced Felling Dogs. So they should be close enough to get me some semblance of spinning. This may well be the last ride of AmbiSinister as I don't have the tools to create the shell with enough balance to make it worth it. May be onto the next design!
Featherweight in progress - Gallowglass - Team Damned by Design
Antweight - AmbiSinister - Team Damned by Design

RevRobots

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Re: AmbiSinister
« Reply #29 on: April 28, 2016, 04:33:37 pm »
Sorry to hear that.  :( I was looking forward to seeing an ant shell spinner. I hope the next bot you build will come together.

Adam
Revelation Robotics