Battlebots Good Weapon Material?

Hey, I'm working on a design for a Battlebot for their 2005 competition in Orlando Florida. I am working on a design that I feel will fair extremely well against any others. Currently, I am looking at a material to use for the weapon. My design calls for a flat bar, about

36-40" long x 3" wide x .5" thick.

What would be the best material to use? Keep in mind that this will be a spinner, spinning at 3000rpm, putting a fair amount of kinetic energy into the other bot.

Hardened S7 Toolsteel fare well against bending or breaking?

Could the peice be bent at a 45 degree angle a few inches from the ends? Without them breaking off, or bending the whole thing.

Does anyone know of any shops that will sponsor a weapon of those dimensions, with a huge strength and hardness?

Oh, and this bot isn't a pipe dream. ;-) We've got over $7000 invested into it. But we still need more money! If anyone wants to donate, Paypal snipped-for-privacy@HHSRobotics.com Please let me know! AJ Quick

formatting link

Reply to
AJ Quick
Loading thread data ...

Check out your local tractor supply store (TSC or whatever is in your area). They will have replacement blades for bush-hogs used on tractor equipment. Many of the larger HP designs are pinned about half way out. The center section or even the end sections may be just what you want. These are tough and have holes already machined in them.

Reply to
george

" Keep in mind that this will be a spinner, spinning at 3000rpm, putting a fair amount of kinetic energy into the other bot."

That kinda mass spinning at that kinda rpm will probably require a huge power source & also put some major kinetic reaction back into your own unit upon impact. A leaf spring from a car or truck will probably suffice. Hope you have a good lawyer on retainer when the shit hits the fan.

Reply to
Wwj2110

I think when George is referring to being "pinned" I think that he means that the blade has a pivot between the center and the end, a three piece blade. In a mower, that reduces the likelyhood of doing damage to the mower if the blade hits something solid. That sounds advantageous in terms of not wreaking havoc on your own bot when it hits something. If you do not do that, you had better have a clutch or some other way to allow slip between the motor and the blade.

Good luck and have fun! Richard

george wrote:

Reply to
Richard Ferguson

AJ

Have you actually tested that spinning yard long 1/2 inch thick 3 inch wide balde?? What happens to your robot when it encounters another, equally heavy, robot ot obstruction?? ?Got any videos to post?

Jerry

Reply to
Jerry Martes

--Bigger and faster spinners already exist, heh. As for lawyers we've had our fill! Why d'you suppose Battlebots went off the air? Lawyers, that's why.. Yecchh!

Reply to
steamer

AL64V Titanium with S-7 toolsteel heads

Reply to
Ernie Leimkuhler

On 19 Dec 2004 18:25:28 -0800, "AJ Quick" vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

I will "digest" what has been said here, and add one idea.

The one idea: quench and tempered steel. You will need to get this cut from sheet, probably. Best with laser. This stuff makes spring steel look like cookie dough! . Its yield strength is enormous. The 350 Bn hard stuff has a "0.2% proof stress" (which I have been told is equivalent to Yield) of around 1100-1200 MPa. 500 is even higher.

Definition Proof Stress: The stress that will cause a specified small, permanent extension of a tensile test piece. Commonly the stress to produce 0.2% extension is quoted in N/mm2 for steel. This value approximates to the yield stress in materials not exhibiting a definite yield point.

They are just machinable, and are weldable, with lots of care. they can be bent. They must not be heated beyond very set levels, because they are already fully treated.

Then George mentioned pivoting. The force on _your_ bot (pun intended) will be enormous if another bot stops that bar, even if you slice into it a few inches. The drive shaft and gearing will need to be some serious stuff, or you need a good clutch. Try a rotating pan, with pivoting blades a la slashers and rotary mowers. The boits I have seen with rotary cutters had multiple teeth to have a similar effect.

Ernie mentioned hardened tips on strong bar. I again suggest the

350-500 hardness grades of QnT alloys. Tips should then be chosen for hardness and extreme impact. From my (limited and often theoretical) experience, this places the stuff you need into about the 600 650 Bn range at max, or it starts to shatter too easily above that.........ah! I see on
formatting link
that they recommend S7 treated to 55 Rc. Roughly the same. Perhaps I was a little high, and getting toward brittle.

Reply to
Old Nick

" A leaf spring from a car or truck will probably suffice. Hope you have a good lawyer on retainer when the shit hits the fan. "

No it probably wouldn't. The shit would not hit a fan, it would hit a

1" thick wall made of lexan.

" Have you actually tested that spinning yard long 1/2 inch thick 3 inch wide balde?? What happens to your robot when it encounters another, equally heavy, robot ot obstruction?? ?Got any videos to post? "

Sorry Jerry, no video.. as my first post was trying to get a material to make the blade out of.

" Bigger and faster spinners already exist, heh. As for lawyers we've had our fill! Why d'you suppose Battlebots went off the air? Lawyers, that's why.. Yecchh! "

I doubt it though, in our weight class and level of competition.. yeah it went away because of some bad lawsuits. None related to injuries, but to who had the rights to the show.

" AL64V Titanium with S-7 toolsteel heads "

I'll look into that. I highly doubt we have the funds, as we've already thrown about $7k into it currently.

Thank you for the link and info "Old Nick".

I'm still kinda looking for a good answer to my original question, however. To all those concerned with kinetic energy and safety.. don't worry about it. The spinner has a way to slip.. also, it is powered by

2 5hp electric motors.. with lots of batteries. Its not going to fly off and kill someone.. if I use a leaf spring from a car.. yeah then it probably will.
Reply to
AJ Quick

On 20 Dec 2004 22:00:53 -0800, "AJ Quick" vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

Which question was that then?..the one about sponsorship, I guess.

You appear to have rejected all the attempts to answer the bit about what steel to use. You want a steel that resists bending, yet can be bent at 45deg. Sionce all of the attempts at replies have failed you, you must know better. So use hardened S7 and see what happens.

Reply to
Old Nick

Um.. excuse me?

The majority of the replies were about a way to make the spinner slip, asking for videos, or suggesting something that would not even be capable.

The 45 degree angle was a question.. would something say tool steel be able to be bent downward then hardened.. then withstand a side impact without bending to the side on that downward 45 angle?

If you can find me a supplier to get this "AL64V" or rather "6AL-4V" as it is known. Or the "quench and tempered steel" as you mentioned than let me know.

The spinner spins at about 250 miles per hour, and would exert about 13 Kilo Joules of energy.

Reply to
AJ Quick

AJ

I guess I have to apologize about asking for videos. I had assumed that you'd have tried something since you have spent $7,000.00 on this project already. I just didnt think you could have gotten this far without having tried something. You must know that an automotive spring can be heated and bent. The question about the durabilty of that spring could be answered pretty easily with some real life tests. I was curious about what you'd broken so far. Now that you've aparently become dissatisfied with the replies you get, I begin to wonder how real this project is. For instance, where does the 250 MPH come from?? I'd have thought a 3 ft long blade rotating at 3,000 RPM would have a tip speed of about 320 MPH. Maybe I'm wrong.

How about sending us a picture of what you have so far. Assuming this is a real project, I'd bet you can get some excellant information from guys on this news group. Your description so far of what you want has been less than well defined.

Jerry

Reply to
Jerry Martes

36 inch mower blades are readily available, of course. And the OP could "double up" to get the thickness required. Battlebot people probably have safety specs for this. Also, I think there are legal limits for RPM for each blade length, at least for OEMs. I think a 22 inch blade has a 3100 RPM limit. 26 inch blade is 2600 RPM
Reply to
bw

The 250mph came from the estimate of 2500 rpm with unmodified motors. I plan on adjusting the timing of the motors, and then overvolting them to 36 volts. Thats how I estimate 3000rpm.. so its going atleast 250mph (for 2500), or more if I make the changes. The gearbox uses 2:1 reduction, so the motors are spinning at 5000 normally, and should add another 1000 with modifications. You are very right, 3000 rpm is

321mph.. would you like your gold star?

I don't know why I have to prove anything to you guys. This is a metal working group, I expected answers regarding the metals to use. You would be surpised at how much this stuff costs. I can show you a whole list of parts we have to add up to $7k.. we have $2500 in motors (5hp electric motors aren't cheap, neither are 1hp, 1 pound motors), the 8 batteries we have won't be enough, and they ran $1100. Oh, and the $1500 control system, + all the controller for each motor ($150-$200) each and we have six... thats just a bit of it.

I posted our website, hhsrobotics.com, if you want to go there and see our 5+ years of Robotics history.

I'm sorry if I am not up for using a car leaf spring as a weapon. I am looking for raw metals that can be obtained easily, and worked with easily. The robot design is fully CAD drawn, and will be made with a high level of precision.. We take more of a NASA approach to this kind of stuff.. not redneck backyard fun. Yeehaw.

Reply to
AJ Quick

But you see, this is a discussion group, not an engineering consulting service. "Smash and grab" posting doesn't always work. There are some very knowledgeable people here that will give you valuable information if you ask the right questions.

You

Just one quick comment on that. The higher the precision, the quicker it will jam. The military learned that 50 years ago with weapons.

Reply to
Jim Stewart

Nasa approach...does that mean yur bot will explode as the start signal is given or someone will screw up a measurement and your bot will miss the arena and wind up heading out of the solar system on a course to eternity?

Id suspect a good redneck backyard bot (made from a riding lawn mower) would use a homebrew thermal lance made from a rusty piece of pipe found in the back 40, and Grandmas O2 bottle and turn your bot into $10,000 worth of smoldering scrap in right short order. Or simply bludgen it to pieces with the differential from a 62 chevy pickemup truck.

Yeehaw indeed.

Gunner

"Gunner, you are the same ridiculous liberal f--k you ever where." Scipio

Reply to
Gunner

Sorta the robot equivalent to the "My son can kick your honor student son's ass" bumpersticker.

Reply to
Jim Stewart
[...]

Seems to me redneck stuff (when put together by intelligent rednecks) outlasts precision anything when abused. But, that said,

formatting link
Thomas Registry if you don't already know it. Has a lot of links to places where you can get professional consultation, talk to engineers, and stay away from us rednecks. You might be able to find a source for the 6AL-4V material mentioned earlier at
formatting link
Yeehaw!

Reply to
B.B.

AJ

I first read your post with alot of interest when I thought you were spinning a big piece of steel and wanted to make an improvement. I was interested in seeing the preliminary results. Then you seemed less than gratefull to the RCM for the replies to your post. Frankly I was surprized to leard that you'd spent $7,000.00 on a project that hadnt been tested with at least one "bl;ade". I suppose I was a bit too critical about your error in having posted 3,000 RPM and 250 MPH. But you could easily have accepted that remark of mine without asking if I wanted a gold star. I consider that an attempt to disrespect me. Correct me if I misunderstood.

You sure dont have to prove anything to me and probably not to "this group". But, when you post to this group that you have a robot project that we are invited to contribute money to, there might be some indication that you are actually building something. The way In read it, the general nature of your thread has been that of a salesman.

I wonder what your objective was to write that you take a NASA approach then reject that that car leaf spring suggestion. I dont see how a leaf spring violated your specification.

Jerry

Reply to
Jerry Martes

BB

Was Smokey Yunick a red neck? In my ignorance, I'd have choosen Smokey's design in preferance to NASA's. Arent there some red necks that think really well and sometimes avoid unnecessary sophistation in orded to get the job done?

Jerry

Reply to
Jerry Martes

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.