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hmartiro / project-thesis

xJüs, the hexapodal robot with a passive-backbone to improve behavior over harsh terrain.
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Manufacture carbon fiber legs #79

Closed PayneTrain closed 11 years ago

PayneTrain commented 11 years ago

@boleary134 @towlett

Can you guys make the carbon fiber legs if you are going to be around for some of break so we can test the xJus on them. I would recommend scaling them down to ~2/3 of the current leg size but I'd get final advice from @Hughzie and @hmartiro

Hughzie commented 11 years ago

My concern with making carbon fiber legs scaled down, is that we're changing two variables. Not very scientific. We won't know whether making them smaller or making them out of composites is what helped...

So I'd say make smaller metal ones first or same-sized composite legs

On Thu, Mar 14, 2013 at 10:03 PM, PayneTrain notifications@github.comwrote:

@boleary134 https://github.com/boleary134 @towletthttps://github.com/towlett

Can you guys make the carbon fiber legs if you are going to be around for some of break so we can test the xJus on them. I would recommend scaling them down to ~2/3 of the current leg size but I'd get final advice from @Hughzie https://github.com/Hughzie and @hmartirohttps://github.com/hmartiro

— Reply to this email directly or view it on GitHubhttps://github.com/hmartiro/project-thesis/issues/79 .

-- Greg --

hmartiro commented 11 years ago

How about 6.5" diameter and slightly more than a semicircle?

PayneTrain commented 11 years ago

I talked to DNS and he had some experience making carbon fiber parts for their wind turbine last semester. Contact him if you would like at: dnewill@princeton.edu

boleary134 commented 11 years ago

Seems plain weave might be the best choice (less unraveling when cut, used on EduBot). There is carbon fiber tape but smallest width is 1". Could use tape (like blue painter's tape) to tape off 1/8" to get the leg width of 7/8" and then use knife to cut off excess after hardener/resin applied. Glenn has hardener/resin. Will need his help with this to get the exact mass ratio of hardener to resin. Glenn suggested using a curved metal piece (similar to legs we already have) as molds. Would then need to put in vacuum bag. There is a small one in shop. Gigi has a larger one. Tom should talk to Fishdick's group because they have experience using carbon fiber.

Still need to figure out number of layers to use.

Need to buy the carbon fibers and mold release tape (or something else similar).

hmartiro commented 11 years ago

I think we should try to get the adhesive pad and carbon fiber stuff ordered tonight.

One thing - if the tape is 1", have we considered using 1" wide legs? They could be 7/8 at the mount and then go to 1" for the rest of the leg. Could lead to better stability and strength - idk, but have we checked to see how wide the legs of other RHex robots are? Also, is the tape all one orientation or in separate orientations? From what Hal said, we might need to have different layers with different orientations.

On Wed, Mar 27, 2013 at 1:49 PM, boleary134 notifications@github.comwrote:

Seems plain weave might be the best choice (less unraveling when cut, used on EduBot). There is carbon fiber tape but smallest width is 1". Could use tape (like blue painter's tape) to tape off 1/8" to get the leg width of 7/8" and then use knife to cut off excess after hardener/resin applied. Glenn has hardener/resin. Will need his help with this to get the exact mass ratio of hardener to resin. Glenn suggested using a curved metal piece (similar to legs we already have) as molds. Would then need to put in vacuum bag. There is a small one in shop. Gigi has a larger one. Tom should talk to Fishdick's group because they have experience using carbon fiber.

Still need to figure out number of layers to use.

Need to buy the carbon fibers and mold release tape (or something else similar).

— Reply to this email directly or view it on GitHubhttps://github.com/hmartiro/project-thesis/issues/79#issuecomment-15540070 .

towlett commented 11 years ago

Unfortunately the card has been canceled...

Also we may run into clearance issues with 1 inch wide legs. I agree that we should order as soon as we get the new cc information.

boleary134 commented 11 years ago

http://kodlab.seas.upenn.edu/uploads/Main/PassiveVariableCompliant.pdf

Check this out. This is the one report so far that goes into detail about legs. Gives info comparing different amount of layers (although done for EduBot and used fiberglass). Used 5L, 6L, 6.5L, 7L, and 9L and found best results using 5L and 6L but with increased chances of breaking.

boleary134 commented 11 years ago

although they used legs of width 18mm (0.7in) whereas our legs are 7/8in = 0.875in. Legs are stiffer with greater leg width.

hmartiro commented 11 years ago

When is the leg material arriving?

towlett commented 11 years ago

Got the confirmation of carbon fiber shipment. It will arrive tomorrow (Wednesday). We have gotten really spoiled by McMaster.

towlett commented 11 years ago

Next shipment of carbon fiber is scheduled to get in on Wednesday. We should be able to check leg 2.0 tomorrow and see if we get better torsional stiffness.

Hughzie commented 11 years ago
towlett commented 11 years ago

I'm going to try to get the new legs into an oven in Professor Arnold's lab tomorrow to post cure them. Here is the data sheet for the epoxy that we are using for easy reference.

http://www.defender.com/pdf/SystemThree_Silvertip.pdf

towlett commented 11 years ago

Sexy legs achieved.