.:`=-~rANdOm~`-=:. Game Servers (Read Only) > Discussion
Holy crap! Racing mecha
Xrain:
--- Quote from: Jhon on January 22, 2014, 05:20:08 AM ---I'm not sure why they aren't using aluminum, but my guess is - Safety. This article might be appropriate - http://www.cineventions.com/steel_aluminum.html
One of their stretch goals is to use carbon fibre and titanium.
I've seen in one of his videos that the robot is planned to reach about 30 kph (18.6 mph). You could always ask him......If you're interested.
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That link actually isn't very applicable. It speaks only to a specific usage (camera jigs) which require a very high level of stiffness. This is because its a long boom with a camera at the end, so if it jiggles every time you move it, your footage would be pretty useless. Everything has an appropriate application.
This case however, the weight they were quoting was 3500kg or nearly 8000 lbs. That is crazy heavy for something that you are going to use as a racing vehicle. You might as well just race around D4 Caterpillar dozers. It speaks to me that they haven't really put much engineering design thought into optimizing for weight and speed. Its a fracking racing mech. The only things you care about is low weight and maximizing speed.
I would envision a racing robot as adding akin to adding a saddle to the Boston dynamics cheetah. Now that would be some interesting racing. :D
Jhon:
--- Quote from: Xrain on January 24, 2014, 05:57:34 PM ---That link actually isn't very applicable. It speaks only to a specific usage (camera jigs) which require a very high level of stiffness. This is because its a long boom with a camera at the end, so if it jiggles every time you move it, your footage would be pretty useless. Everything has an appropriate application.
This case however, the weight they were quoting was 3500kg or nearly 8000 lbs. That is crazy heavy for something that you are going to use as a racing vehicle. You might as well just race around D4 Caterpillar dozers. It speaks to me that they haven't really put much engineering design thought into optimizing for weight and speed. Its a fracking racing mech. The only things you care about is low weight and maximizing speed.
I would envision a racing robot as adding akin to adding a saddle to the Boston dynamics cheetah. Now that would be some interesting racing. :D
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Yeah, I wonder if they have a good reason for that.....So I asked him =P We'll see if they really haven't put enough thought into it.
LOL, riding that Cheetah would be awesome, although from how it looks now, it would fucking hurt your balls xD
Jhon:
--- Quote from: Xrain on January 24, 2014, 05:57:34 PM ---....
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I completely forgot about this topic.
Albeit late, I'll post his answer anyway:
"...First of all, aluminum and carbon-fiber are used extensively in the interface and power plant.
For the legs and chassis The Alpha Leg is made of mild steel and the final machine will be Chromoly. There are two main reasons I've chosen steel.
1) Fatigue. Aluminum has no lower fatigue limit. This means that parts made of aluminum *will* break, it's just a matter of when. Yes, you can push that out to "100 years" but weight savings will diminish.
2) Repairability and ability to modify. Aluminum needs to be heat treated after welding to reach max strength. This is an expensive process that requires putting the part in an oven for, literally, days. This makes in-field repairs or mods impossible (or extremely risky)
Of course, if I had a million bucks, I'd make the whole thing off titanium."
Xrain:
--- Quote from: Jhon on March 13, 2014, 03:54:41 PM ---I completely forgot about this topic.
Albeit late, I'll post his answer anyway:
"...First of all, aluminum and carbon-fiber are used extensively in the interface and power plant.
For the legs and chassis The Alpha Leg is made of mild steel and the final machine will be Chromoly. There are two main reasons I've chosen steel.
1) Fatigue. Aluminum has no lower fatigue limit. This means that parts made of aluminum *will* break, it's just a matter of when. Yes, you can push that out to "100 years" but weight savings will diminish.
2) Repairability and ability to modify. Aluminum needs to be heat treated after welding to reach max strength. This is an expensive process that requires putting the part in an oven for, literally, days. This makes in-field repairs or mods impossible (or extremely risky)
Of course, if I had a million bucks, I'd make the whole thing off titanium."
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1) I'm not quite sure what the issue is here, yes aluminum is more susceptible than steel to repeated stress fracturing. But how long are you expecting this robot to walk for 100,000 miles? I thought it was a racing robot, the thing should just barely be holding itself together by its bootstraps. On a more serious note lowering the mass lowers all of the forces involved in that walking motion. This is what engineering is about, applying steel where the forces involved necessitate it and using aluminum where you can.
One of my preferred methods of construction is carbon fiber coated aluminum. You use thinner aluminum tube and layup carbon fiber over the assembled structure. The aluminum dampens out oscillations keeping it from wiggling so bad, while the carbon fiber adds gobs of strength.
2) Yes to maximize the strength of aluminum, annealing is a good idea. But I don't really think they are that close to the safety margins that welding without heat treatment will compromise the integrity of the vehicle. Granted, Over time the vehicle will need to be overhauled to replace things that are getting dodgy. But saying you have to heat treat every time you weld aluminum in this realm of application is not true in the slightest.
But welding isn't the only way to assemble aluminum. Make the root fixtures out of steel, then thread the inside of the steel tubing, and each end of the aluminum tube; coarse class 2 threads would be the way to go to make it come together easy. Hard anodize the threads if you are going to take them apart frequently, and add some thread locker, and now you have a screw together robot, that if you break a tube you can swap it out in a few minutes and you still can weld the steel together. Everyone wins!
It will take a bit more to get everything fabricated since each thread takes about 20 minutes of lathe time, annodization sounds expensive but you can do it in a plastic bucket in your shop if you are determined. But you should be able to shave off quite a bit of mass overall, and increase repairability.
I would encourage them to look around more more innovative construction methods than triangle frame tubular construction. There are a million ways to assemble that bot, and many of them involve a lot less weight.
Tezuni:
--- Quote from: Xrain on March 15, 2014, 02:08:06 AM ---
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What they say about the fairbanks engineering program must be true, lol. Spoken like a real engineer there.
Now, let's put these ideas into making contraptions to explore under the ice of europa or something interesting like that...
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