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Unread 02-08-2005, 09:13 PM
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Question "sandwich" claw

when building a claw, would it be beneficial to make it in a sandwich like fashion for example a layer of aluminum, a layer of fiber/plexi glass, then a layer of aluminum all bolted(or whatever it takes t attach them) together, to use the benefits of each part to the max?
thanks
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Unread 02-08-2005, 09:41 PM
Rick TYler Rick TYler is offline
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Re: "sandwich" claw

Quote:
Originally Posted by skillinp
when building a claw, would it be beneficial to make it in a sandwich like fashion for example a layer of aluminum, a layer of fiber/plexi glass, then a layer of aluminum all bolted(or whatever it takes t attach them) together, to use the benefits of each part to the max?
Composite materials take many forms, and are used for (you guessed it) a lot of different purposes. My wife works on the F22 fighter. Most of the wing spars are RTM carbon fiber parts (don't worry -- this isn't classified), but every few spars one is replaced with titanium. Titanium is heavier and less stiff, but it resists certain kinds of battle damage better. The wing is a titanium/carbon fiber/resin composite structure. We asked about getting some QC rejected carbon fiber spars for our robot, but it turns out they belong to the Air Force, too.

Your specific suggestion for an aluminum/fiberglass sandwich makes me wonder what you are trying to do? If you want a superstrong, lightweight, very stiff structure, you would be better off making a laminate of 45/45 biaxial fiberglass epoxied to both sides of structural foam like Divinycell. The aluminum won't buy you much, and will bond poorly to the fiberglass. IMHO, using mechanical fasteners to create your composite panel is suboptimal. Most boats and a lot of airplanes are held together by glue, not screws.

Let us know what you want your structure to accomplish and maybe we can give you better suggestions. (I wanted to make an epoxy/carbon fiber/fiberglass arm for our 'bot, but I was outvoted by conservative teenagers. Oh well...)

Rick Tyler
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Unread 02-08-2005, 09:49 PM
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Re: "sandwich" claw

conservative teenagers?! only in robotics lets say.
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Unread 02-08-2005, 09:54 PM
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Re: "sandwich" claw

Quote:
Originally Posted by Rick TYler
Composite materials take many forms, and are used for (you guessed it) a lot of different purposes. My wife works on the F22 fighter. Most of the wing spars are RTM carbon fiber parts (don't worry -- this isn't classified), but every few spars one is replaced with titanium. Titanium is heavier and less stiff, but it resists certain kinds of battle damage better. The wing is a titanium/carbon fiber/resin composite structure. We asked about getting some QC rejected carbon fiber spars for our robot, but it turns out they belong to the Air Force, too.

Your specific suggestion for an aluminum/fiberglass sandwich makes me wonder what you are trying to do? If you want a superstrong, lightweight, very stiff structure, you would be better off making a laminate of 45/45 biaxial fiberglass epoxied to both sides of structural foam like Divinycell. The aluminum won't buy you much, and will bond poorly to the fiberglass. IMHO, using mechanical fasteners to create your composite panel is suboptimal. Most boats and a lot of airplanes are held together by glue, not screws.

Let us know what you want your structure to accomplish and maybe we can give you better suggestions. (I wanted to make an epoxy/carbon fiber/fiberglass arm for our 'bot, but I was outvoted by conservative teenagers. Oh well...)

Rick Tyler
thats a lot of materials I've never heard of. is there somewhere i can go to find out more about them? by the by, this is for the claw on the end of a long arm, so I'm trying for light, stiff, and well i guess everything you listed there.
thnx
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Unread 02-09-2005, 12:04 AM
Rick TYler Rick TYler is offline
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Re: "sandwich" claw

Quote:
Originally Posted by skillinp
thats a lot of materials I've never heard of. is there somewhere i can go to find out more about them? by the by, this is for the claw on the end of a long arm, so I'm trying for light, stiff, and well i guess everything you listed there.
Check this Website:
Materials information. It's a site for amateur boatbuilders, but a lot of the materials would be the same.

Good luck.

- Rick Tyler
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Unread 02-09-2005, 07:28 PM
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Unhappy Re: "sandwich" claw

Quote:
Originally Posted by Rick TYler
Check this Website:
Materials information. It's a site for amateur boatbuilders, but a lot of the materials would be the same.

Good luck.

- Rick Tyler
i searched Divinycell on that site but couldn't find anything. is there somewhere else i could look also?
thx
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Unread 02-09-2005, 07:31 PM
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Re: "sandwich" claw

Using composites like fiberglass effectively takes some specific skill. If you don't have anyone experienced in it, and especially if you expect to use it on this years robot (its week 5), it's probably a bad idea to get started now. The difference between fiberglass and aluminum, for example, is not huge, but the amount of weight incorrect choice of sizes and thicknesses and gussets etc can add will be much more significant. At this point, you should probably stick to something you are a bit more familiar with.
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Unread 02-10-2005, 01:12 AM
Rick TYler Rick TYler is offline
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Re: "sandwich" claw

Quote:
Originally Posted by Max Lobovsky
Using composites like fiberglass effectively takes some specific skill. If you don't have anyone experienced in it, and especially if you expect to use it on this years robot (its week 5), it's probably a bad idea to get started now. The difference between fiberglass and aluminum, for example, is not huge, but the amount of weight incorrect choice of sizes and thicknesses and gussets etc can add will be much more significant. At this point, you should probably stick to something you are a bit more familiar with.
Upon sober reflection, I'm with Max. How about forgetting composites for this year and just making your claw out of steel or aluminum? I think there are real advantages to composites for some parts of the robot, but I wasn't thinking it through. I have a certain down-and-dirty understanding of amateur composites from two years of home-boat building. If you are starting from scratch and don't have any epoxy/glass/etc expertise on your team you'd be better off to save it for next year.

Sorry for (maybe) steering you wrong. I answered the question you asked without thinking about whether or not you might have been asking the wrong question -- or at least asking a really adventurous question. (Hey, I'm the guy who wanted to base our whole game strategy on a material that no on else on our team understands.)

It would have been a great Week One question, I think. You can learn more about Divinycell here.

Good luck!

- Rick

Last edited by Rick TYler : 02-10-2005 at 01:18 AM.
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Unread 02-12-2005, 02:54 PM
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Re: "sandwich" claw

Quote:
Originally Posted by Rick TYler
Upon sober reflection, I'm with Max. How about forgetting composites for this year and just making your claw out of steel or aluminum? I think there are real advantages to composites for some parts of the robot, but I wasn't thinking it through. I have a certain down-and-dirty understanding of amateur composites from two years of home-boat building. If you are starting from scratch and don't have any epoxy/glass/etc expertise on your team you'd be better off to save it for next year.

Sorry for (maybe) steering you wrong. I answered the question you asked without thinking about whether or not you might have been asking the wrong question -- or at least asking a really adventurous question. (Hey, I'm the guy who wanted to base our whole game strategy on a material that no on else on our team understands.)

It would have been a great Week One question, I think. You can learn more about Divinycell here.

Good luck!

- Rick

well, we finished it this week. i guess we have decided that we would build a composite of some sort w/alluminum sides
thanks for your help (and we do, by the way, have people experienced with this composite dealie).
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