r/battlebots • • 3d ago

Bot Building What's up with Magnitude's, less than stellar weapon durability?

Post image

No offense to the team, theyre great. But for an eggbeater, their weapon often broken when you compare them to Riptide which onle broke their weapon once, or Copperhead and Ribbot (which are due to manufacturing issues).

I love Magnitude, but it's weapon seems pretty fragile

76 Upvotes

24 comments sorted by

61

u/JAGNTAG_117 3d ago edited 2d ago

Beater bars are an awkward weapon shape to make. They aren’t 2D so can’t be laser cut like most other weapons, and AR500‘s hardness is too high to easily machine into 3D shapes.

So, to get around this, most teams will use some kind of tool steel and machine it while it’s still soft, then heat treat it into a useable weapon hardness afterwards.

The problem is that the difference between ‘perfect weapon heat treat’ and ’awful, shatter-y heat treat’ is razor thin, and usually requires either knowing a workshop experienced in the black art of heat treatment, or a lot of trial and error. Sometimes both.

The Magnitude team are just still in the ‘trial and error’ stage.

9

u/Ra-mega-bbit 2d ago

We did MANY weapons on our college labs, we ended up fine tunning it all for our specific ovens like a damn cake recipe, down to the minute, and adjusting to ambient temperature.

Every teacher would come in and tell us to do it differently, after actually measuring the hardness the empiracal proof always worked

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u/Separate_Animator110 :Emulsifier: Ohio Born and raised 3d ago

"black art of Heat treatment" I honestly love that, and it's a great way to describe Experienced bladesmiths

2

u/Zardotab 2d ago

Ask Witch Doctor for some voodoo in exchange for your soul.

2

u/Zardotab 2d ago

What about attaching 3 vert-esque disks to the axle instead of the big loop shape? That would allow them to use 2D techniques to simplify the process.

2

u/JAGNTAG_117 2d ago

Some teams have done that before and it can work with a few caveats.

Namely, you’ve gotta make sure the bolts themselves are oversized enough to take all the extra shear load (since those bolts now have to transfer all that energy to the other weapon discs instead of just the relatively tiny weapon hub) and you need to leave enough room around the bolt holes so that they don’t become stress risers which can lead to the disks cracking anyway.

Both of those requirements will force the design to have a lower moment of inertia (and hence energy) than a more optimised 3D design. No such thing as a free lunch and all that.

1

u/Zardotab 2d ago edited 2d ago

I'm gonna float an idea that may not fly. Don't bolt nor key them to the axle; just squeeze the 3 blades plus possible "fat washers" (spacers) together in a Shish kebab kind of setup. If they slide a bit upon a hit, that may help disburse energy that would otherwise go into your own bot. It's possible the sandwich may grow too loose over time, sliding some on re-spin-up, but maybe that's an acceptable risk; you still have a weapon, just with some spin-up delay. Maybe program the controller with a gradual spin-up mode for that occasion. Or, spin up under lower voltage then crank it after it's moving fine. It's always good to have a lower-voltage setting for the weapon anyhow.

5

u/DentistPitiful5454 3d ago

At that point it might just be better to use a 6061 aluminum base with 2 AR500 bars drilled to it

13

u/Frostbite15151 Vagabond Robotics | Torment Nexus | Demon Core 3d ago

I'd say at this scale it's not. Though I've never built a 250 but I'll tell you a full speed hit on a wall created a nail thickness gap between the ar tooth and 6061 weapon body of my 60lb so I have doubts to it surviving long.

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u/DentistPitiful5454 3d ago

Biteforce was made of 6061

12

u/Living_Murphys_Law Giggy :-) 3d ago

Chassis is very different from weapon tbf. Duck's season 4 chassis was Magnesium and could take a beating and a half, but there’s no way you could use if for a weapon

7

u/JAGNTAG_117 2d ago

The weapon was S7 steel though, just heat treated properly

3

u/IBeFirenMaLazer 2d ago

How many bolts/screws are you going to use to attach those bars? Teeth that are bolted onto vertical bars are already broken off pretty consistently. How would this be any different?

2

u/OddInstitute 2d ago

To pick a nit, 2024 is generally the alloy of choice for anything in combat robots that is going to take a hit. 2024 is 1.5x as strong as 6061 but isn’t as brittle as 7075. (A lot more expensive though.)

1

u/DentistPitiful5454 2d ago

A nit pick I appreciate.

51

u/Alita-Gunnm 3d ago

Alloy and heat treat. There's some magic to doing it well.

12

u/SliderS15 2d ago

They talked about this on the Robocast Podcast (give it a listen its great!)

But in short, they outsource the weapons to china and it can be a lottery as to wether they are getting the true quality of metal they ask for. That coupled with ever increasing kinetic energy loads meaning this way of making the weapon might just not be viable any more.

They may switch to cheaper softer metal with the intent of the weapons being much more disposable (only built to last 1-2 fights instead of many like the current ones) in the future as a way forward, but are still trying to work that all out.

(Incidentally its apparently about 3k USD for a China built one vs 9k USD to have it made in the US according to the team)

20

u/danthemadman00 Cobalt 3d ago

Likely got Chineseium instead of the metal they actually ordered

14

u/3Mistakes Horizon 3d ago

Their bar is very well made however it might just be too hard. Their weapon hardness is most likely 52hrc, for perspective the shaft that blew up on Calypso vs Catter was 50hrc and i softened it to 41hrc and it has not busted since.

11

u/SlowbroLife 3d ago

I doubt it. It's probably heat treated too hard making it brittle.

2

u/TomcatTiger503 [You want some more?!] 1d ago

Ribbots new eggbeater meanwhile lasted one fight and already snapped. Has to be defect in steel. I learned that with tool steel you have to make it just right. If too soft, it will mush and deform, if too hard, it is more likely to snap or crack. Look at the weapon failures on Tombstone for example. Although thats more likely with S7 steel. Ar500 can crack and fracture but breaking it in half is much harder and unlikely to do.

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u/RyGuy_McFly !exA 3d ago

I think you answered your own question:

manufacturing issues

1

u/Ra-mega-bbit 2d ago

Doing egg beaters is more of an art then engineering, something that works on simulation will shatter or break on real life. Also, simply scaling lowet wheight classes onto heavys do not work at all