Carbon bracket design

Talk Composites - The Forum for Advanced Composites

Back

Carbon bracket design

Author	Message
Jucasan	Jucasan posted 9 Years Ago HOT Topic Details
Group: Forum Members Posts: 8, Visits: 91	I'm planning to make this bracket with CF but don't have a lot of experience working with it and need advice. 1) the radius of .5 in the ones with the ? mark. How small can I go? Thinking about using vacuum forming. 2) For the shape. I'm thinking about making a male in wood, lay the fabric on top and once is cure machining the contour. Is this a good idea? 3) What about the thread. Should I make a metal insert ? Any advice would be welcome. thanks Attachments carbon bracket.pdf (365 views, 171.00 KB)
	Reply Like 2
Fasta	Fasta posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 3.5K	Since this is like an extrusion then I would find a metal channel section that is suitable dimensions and radius on the inside. Then use this section as your female mould and make a carbon piece from inside the channel. This will give you a moulded finish on the outside of the new part and a coarse finish on the back side depending of your process/technique. For me I would use pre preg carbon only because it is so much easier than messing with the wet laid process but then you would also need an oven and vac pump etc to do it. It could also be done with a wet laid technique easy enough though. Release the part and trim to your overall shape. Maybe you could bond a 2mm stainless steel plate to back side of the bracket that already has the 10 holes in place. Then when the glue is cured drill through the carbon too and then tap the threads. Using this extrusion kind of mould you can make a length of carbon 500mm long and cut this up into a number of bracket parts? To take it a step further you could alternatively make two metal channels to form a moulded finish on both sides of the bracket if needed. Layup over the inner channel mould and then sandwich the two moulds together. Fastacraft Facebook page Edited 9 Years Ago by Fasta
	Reply Like 2
Jucasan	Jucasan posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 8, Visits: 91	Thank you Fasta, I would like to make the .5 inch (12.7 mm) radius smaller. How much would you consider is safe? I also read that machining CF can produce delamination. Any tip on that? Saw your website. Incredible stuff that you made. I went to see the americas cup in San Francisco and I felt in love with those boats. Jimmy Spithill is a hero https://www.youtube.com/watch?v=v6e7bzQWjuo Thanks again Edited 9 Years Ago by Jucasan
	Reply Like 2
Fasta	Fasta posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 3.5K	I think the radius could much smaller if needed. It will most likely depend on what tube or angle sections are available off the shelf and the radius that they already have or you could get a sheet metal fabricator to fold up some metal (stainless steel or aluminium is nice) to the dimensions and radius you want. Any radius 3mm or bigger should work fine. If you made a small length of carbon channel as suggested you would then just mark out the profile you want and typically it would often be cut with a diamond grit disc on an angle grinder or die grinder. Then shape further with sanding disc on an angle grinder. You could even cut the basic profile shape with a metal hacksaw blade and then shape further with the sanding disc? Do you really need a moulded finish on both sides? Doing just a moulded finish on the outside would look very tidy and be easy to do. Fastacraft Facebook page Edited 9 Years Ago by Fasta
	Reply Like 2
Jucasan	Jucasan posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 8, Visits: 91	Hello Fasta, Thanks again for your advice. I have access to a CNC machine so I'm going to make 3 plates bolted together as you can see in the PDF as a mold. Once the part is dry I can put the whole thing in the vice and machine the perimeter to remove the excess of CF and drill holes. I'm not going to worry about the inside of the part. Since this part is going to be structural still need to do some research in terms of how many layers I need, decide between pre-preg or wet and learn a bit more about vacuum bagging. But thanks to your help I'm one step closer. Attachments bracket mold.pdf (334 views, 159.00 KB)
	Reply Like 3
Jucasan	Jucasan posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 8, Visits: 91	Finished the sides of the mold. Haven't done the middle plate yet since the dimensions are going to depend on the amount of CF layers. Also machined those 2 inserts to be sandwiched in the CF to be able to tap the holes. What is my best option in terms of structural strength. Full CF laminate or sandwich? I'm thinking to lay Coremat but I'm open to sugestions. This part is the hinge of a back rest for a recumbent bicycle. I know is hard to tell but any guess of how many CF layes to make it? Thanks Edited 9 Years Ago by Jucasan
	Reply Like 3
Dravis	Dravis posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 592, Visits: 1.9K	How thick walls would you use to make the bracket out of aluminium? Thats a good guideline.. same thickness in solid CF .. Then test, you may get away with a thin core, but for a structural bracket, the saving in weight is probably not worth the bother. "Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
	Reply Like 3
Jucasan	Jucasan posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 8, Visits: 91	Thanks Dravis, sounds like a good idea
	Reply Like 2