Author Topic: Pizza Slicer - Team Food Fight  (Read 7664 times)

emancarrillo

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Pizza Slicer - Team Food Fight
« on: October 18, 2015, 11:21:34 pm »
Alright after my last event with Pizza Cutter. Which was a modified Viper kit. I wanted to make a fully custom antweight. Pizza Cutter is think is a good mix of defense and offense. A wedge with a small active weapon.

But this is going to be a robot that is very weapon forward. The idea here is to make something that can deliver some big hits. Pizza Slicer is my go at an even bigger Vertical Spinner. I got to see Bit Vicous in action at Robothon and was a fan of the robustness/power of his weapon. I had gone agaisnt mounting my spinner directly to the blade, because of all the bent shafts I had read about when doing it this way, But seems that the durability of Bit Vicious is because the motor it uses has a 5mm shaft. Couple that with a longer hardened shaft. And it should make for a very good motor base.

This is my first draft at this layout. Will have to do a bit of weight reducing, but think its totally possible to get this under the 1lb limit.

For reference the Blade is 4" long.


« Last Edit: October 19, 2015, 02:13:32 am by emancarrillo »

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #1 on: October 18, 2015, 11:40:40 pm »
One thing I'm considering is changing the drives from 11:1 Silversparks that are currently in the model to Pololu 50:1
Or even Maxons 17:1

Speed Calc: (1.75" Wheels at 11.1v)

Maxon 17:1 - 9.8 MPH (14 FT/S)
Silver Sparks 11:1 - 8.1 MPH (11.9 FT/S)
Pololu Micro HP 50:1  - 6.0 MPH (8.8 FT/S)


With the Pololu's I could potentially shift my battery placement a bit and have it run parallel with the blade as opposed to along the back wall. Also would give me the benefit of shaving a bit more weight off too.

The question is why are these not more popular? Are they more prone to breaking in Battle as opposed to the Silver Sparks? They're really cheap on eBay too.

The Maxons are fairly cheap of eBay (9USD), but requite a bit of modification to make them 17:1 as opposed to 64:1 the eBay ones come in at.
« Last Edit: October 18, 2015, 11:44:30 pm by emancarrillo »

Coboxite

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Re: Pizza Slicer - Team Food Fight
« Reply #2 on: October 19, 2015, 02:01:24 am »
All of your links are broken, you might want to fix that.
One problem I see is that the wheels are extremely exposed. For a horizontal spinner, they be tempting targets. You might want to consider a sweeping wedge design, such as Electric Boogaloo. You might also want to consider an asymmetrical weapon if you're going to be spinning it uber fast.

The reason why most ants don't use those tiny motors comes down to power. Once the weapon stop working, its nice to be able to push the other guy. Though, because your bot is so weapon heavy, all you need for the drive motors to do is get your bot around the arena. Beware of ebay motors, they are wildly varying from each other.

One last thing, it looks oddly like Viciously Circular.


emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #3 on: October 19, 2015, 02:53:22 am »
All of your links are broken, you might want to fix that.

Thanks for the heads up. They should all be fixed.

Quote
One problem I see is that the wheels are extremely exposed. For a horizontal spinner, they be tempting targets. You might want to consider a sweeping wedge design, such as Electric Boogaloo. You might also want to consider an asymmetrical weapon if you're going to be spinning it uber fast.

Good call. I can set the wheels back a bit and have the front wedges also double as guards. Deflect a bit incase I do face a horizontal spinner.



Quote
The reason why most ants don't use those tiny motors comes down to power. Once the weapon stop working, its nice to be able to push the other guy. Though, because your bot is so weapon heavy, all you need for the drive motors to do is get your bot around the arena. Beware of ebay motors, they are wildly varying from each other.

I'm perfectly ok with the motors not having super amounts of pushing power. As long as they're zippy enough to move me around. If my weapon goes down on this bot I'm ok at being at a disadvantage. Since it is so weapon forward, I don't expect to win a pushing match if it comes down to that. Just haven't seen much on those motors.


Quote
One last thing, it looks oddly like Viciously Circular.
Nice, hadn't seen that one before. Also seems to go by the name of End Game as well. And I agree the concept is very similar.

One thing I want to avoid though, and that I had a problem on my other bot, is when the wedge actually interferes with weapon getting a good hit on the opponent. This is a perfect example of what I mean.
https://www.youtube.com/watch?v=kx1tCl39P1g

One thing I consciously tried to do was minimize this effect, by having the weapon path actually go past the front of the wedge.
« Last Edit: October 19, 2015, 02:54:54 am by emancarrillo »

Koolaid64

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Re: Pizza Slicer - Team Food Fight
« Reply #4 on: October 19, 2015, 07:36:20 am »
I have tried the pololu motors in a number of different bots over the years and they always break in the first stage after any good hit. from you or them, doesn't matter. I would recommend the sparks for their robustness.

-Kyle 

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #5 on: October 20, 2015, 03:01:45 am »
Ah thats a bummer. The Pololu's would really help with the battery placement. If I can fit the battery parallel to the Blade, or in the wedge section. I can actually shift motor back a bit more and have back triangle pieces be a lot closer to the blade edge and make everything more compact.

The current layout is fine in CAD. But I'll need to mock everything up to see how it'll all fit when the wires start getting routed. If anything I can switch to a slightly smaller battery.

I'll probably finalize the 3D model soon and then 3D print a rough version for fit check.
« Last Edit: October 20, 2015, 03:05:32 am by emancarrillo »

Jeff Gier

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Re: Pizza Slicer - Team Food Fight
« Reply #6 on: October 20, 2015, 10:25:07 am »
That's a lot of weapon power! 

It's probably good to note that the stainless steel shaft you linked is not likely stronger than the stock shaft on the motor.  My turnigy's (but never tried this specific one) have had hardened shafts stock.  If you want to beef it up, you can get S7 or O1 tool steel from mcmaster for cheap and hardened them yourself.  You should be searching for steels with a hardness in the Rockwell C range. 

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #7 on: November 12, 2015, 03:40:19 pm »
So started to change to the design a bit. I'm getting rid of the triangle section in the back. I realized it would really impede the ability to self right if it happens to get flipped over. So that's gone to a straight back So it can rotate around the wheels if needed. Increased the front wedge sections a bit to hold the battery and electronics. Should be enough room to squeeze everything in.

Considering this controller too. Seems like a nice little package. But I have extra Tiny ESC's that I could use too. Just on my radar.
http://www.operativerc.com/products-miniduo.html


Also swapped out the bar for a hollowed Disk. Figured this would increase my weapon reach. The tooth is at a 4.5" circle. But still keep the weight down. Solidworks has it at about 62grams out of 3mm thick 4130. (Need to learn how to do stress analysis in SW to optimize thickness and design, but general idea)


Right now I'm debating on how to mount the weapon motor. I could directly mount the weapon to the motor. The 5MM shaft should help with this. And would be pretty simple to do. Just need  to press a longer shaft.

Could use a slight smaller motor and mount it a bit lower. And use a pulley system there. The easiest way to do this as I can sue almost off the shelf parts for this.

 Or mount it inside the frame. Make a pulley that mounts around the motor. Similar to how Ellis mounted his motor for Newton.
The most complicated to make. But the most protected Motor option.

Thoughts on these? (realize each one would require a bit more tweaking on the frame design)


 
« Last Edit: November 12, 2015, 03:43:36 pm by emancarrillo »

Coboxite

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Re: Pizza Slicer - Team Food Fight
« Reply #8 on: November 12, 2015, 06:00:52 pm »
If you want to direct drive the weapon, try building the weapon motor into the weapon itself(Stance Stance Revolution is a good example of this). You may also want a front wedge to stick out under the weapon to aid with stability and to help counter pure wedges.

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #9 on: November 12, 2015, 07:22:37 pm »
If you want to direct drive the weapon, try building the weapon motor into the weapon itself(Stance Stance Revolution is a good example of this). You may also want a front wedge to stick out under the weapon to aid with stability and to help counter pure wedges.

Good idea on that. Not sure why I over looked that. Lots of drum bots that do that and they seem to hold up fine. I do like how SSR uses a thinner blade and how his motor choice allows the blade to be bolted to it.

Now I need to find a motor that'll work. The ones Charles used are 98gm. I was already cutting it close. So we will see what I can find.

As for the stability thing. For sure need to solidify that. I was considering adding little feet off the main supports. But I'll play around with some ideas on how to stabilize it as best as possible. 
« Last Edit: November 12, 2015, 09:47:01 pm by emancarrillo »

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #10 on: November 12, 2015, 09:51:34 pm »
Quick Mockup of the other mounting option. Using a MultiStar 4220 in Green and a Turnigy D3530 in the orange.

The Multistar will work, it wont be centered. (unless I make the frame wider). But the motor should be a bit more protected.

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #11 on: November 14, 2015, 02:32:14 am »
Think I'm going to go with the Turnigy D3530 motor with a Servo City Hub to mount the blade. With a 5mm bearing on otherside to support the shaft. That should ideally be a robust, yet easy to construct weapon system.


Right now I'm working out the best way keep the bot from tipping forward. Since the motor is mounted so far out from the base I explored a few options. A,B,C is sorta the evolution.

A. Easily changeable supports. Figured if I go up against horizontals and they get taken out, they are easily replaced.
B. More integrated supports. Built into the Center brackets, if damaged, the whole bracket needs to change.
C. Compound wedge. Most robust. Can sweep the wedge back over the wheels like Coboxite referenced earlierly. The thing is that traditional Nutstrip wont work to attach the front wedge because of the angles. So will have to figure out a robust way to attach those parts. Would 3D printed Nylon work?
 

For the Weapon Brackets. I currently have them modeled as 3mm thick Aluminum. However I can go up to 6mm thick Delrin or even thicker HDPE and save weight. Would 5mm thick Delrin or  HDPE be strong enough to hold up?

« Last Edit: November 14, 2015, 03:54:59 am by emancarrillo »

Coboxite

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Re: Pizza Slicer - Team Food Fight
« Reply #12 on: November 14, 2015, 04:12:32 am »
I think of all of them, C is the best option, but a merger of B and C would be the best if you could make the front wedge extend just a little bit. Otherwise, you might be vulnerable to fast low wedges.

Delrin and HDPE are pretty tough, but UHMW is tougher still. That might be the best choice.

emancarrillo

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Re: Pizza Slicer - Team Food Fight
« Reply #13 on: November 14, 2015, 09:26:21 pm »
So I started dialing in the CAD a bit more. Getting to weight will be very tricky.

https://docs.google.com/spreadsheets/d/1Cs6lLY5C_PeHKXxx9U_GbdRsCkCgEEkwt1rQjZJXx3M/edit?usp=sharing


But If I switch to Pololu 50:1 From Silver Sparks and switch from my $8 Turnigy Battery to a smaller capacity battery. (have a hard time finding good options. Thunderpack 350mah. Might work, but expensive to shave only 8 grams.

I think I can get close to weight, but will have to shave weight wherever I can.

Also was hoping to use 1/16" Ti, but have switched over to 1/16" 6061 for the weight reduction. Which hopefully will work.
Center supports are 3/16" UHMW.


 
« Last Edit: November 14, 2015, 09:45:47 pm by emancarrillo »

Koolaid64

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Re: Pizza Slicer - Team Food Fight
« Reply #14 on: November 14, 2015, 09:58:17 pm »
given the size of your weapon to could save some money going to a bar style design. less material wasted you know. Anyway looking good, cant wait to see some real bits.

-Kyle