Idea's for a carbon fiber box

[chips2481]

Hello. New to this forum and this kind of hobby/profession however hoping this project will be workable. It will be for an electric scooter. Currently the scooter, linked below, has metal tube frame. What I want to do is cut the middle section of the frame and bolt it to each side of a carbon fiber pan similar to the picture below. This way I will have no frame running down the middle of the pan leaving more room for batteries. Is this possible or would it end up breaking? If so what kind of thickness would I need to make it at? Is a simple box such as this easily done with a mold or do you need other tools?

http://www.goped.com/products/esr750ex/images/ESR-750-fold_lg.jpg

[morepower]

You need to give more info about the weight loading expected. You also need to remember using carbon will need a glass skin on the side where it could contact the terminals. Carbon is a conductor of electricity so you need to think about the risk of the electrical parts touching the carbon. There are a number of things you can do to add stiffness like adding a foam core or adding Kevlar. If the box is going to be made as a two piece part with the lid being the only removable part it would be stiffer than one made up from flat sheets bonded too…

[chips2481]

You need to give more info about the weight loading expected. You also need to remember using carbon will need a glass skin on the side where it could contact the terminals. Carbon is a conductor of electricity so you need to think about the risk of the electrical parts touching the carbon. There are a number of things you can do to add stiffness like adding a foam core or adding Kevlar. If the box is going to be made as a two piece part with the lid being the only removable part it would be stiffer than one made up from flat sheets bonded too…

You need to give more info about the weight loading expected. You also need to remember using carbon will need a glass skin on the side where it could contact the terminals. Carbon is a conductor of electricity so you need to think about the risk of the electrical parts touching the carbon. There are a number of things you can do to add stiffness like adding a foam core or adding Kevlar. If the box is going to be made as a two piece part with the lid being the only removable part it would be stiffer than one made up from flat sheets bonded too…

I am 180lbs, the total weight of the scooter with batteries will be 50-60lbs and the torque of the motor will of course add more. Probably best to say a 350lbs max load.
I will have all wiring well shielded and maybe a rubber linning inside the pan.
Seems like the biggest challenge would be connecting it to the existing tubing. Or maybe it is possible to make the entire frame carbon?
I pulled it apart and took some pictures of the frame, hope that will get some ideas.

[fiberglasshi]

What are you trying to achieve by cutting the frame apart and putting in the box? You can make a box out of a carbon kevlar mix that is stronger than the frame as long as it is constructed properly. If you’re trying to add a storage area then I’d say keep the frame and construct a box that is retro fitted to the frame.

www.fiberglasshawaii.com

[mugget]

If you really wanted to, you could definitely make the entire frame out of carbon. Have a search around here and the 'net - people have made bicycle frames from carbon and the technique and principles would be pretty much the same.

If you want to make the tube sections of the frame with an integrated box in the middle, you could do that as well, but it would just take a bit more thought to plan how you’re going to do it.

To cut the frame and connect it to the new carbon box section you would probably just need to get the frame fabricated with some mounting plates that you can bolt to the box. There’s just so many different ways that you could go about it - single mounting plates on the ends of the cut tube sections, a metal frame that runs around the perimeter of the box, under the box etc…

If you have never made anything with composites before I would suggest making some test pieces first up. For example maybe some 10x20" flat sections and experiment with core materials, then you’ll start to get an idea of what kind of base you can make. Once you start making test parts you’ll get a much better idea of what’s possible and the properties of different layups, core materials etc.

[chips2481]

What are you trying to achieve by cutting the frame apart and putting in the box? You can make a box out of a carbon kevlar mix that is stronger than the frame as long as it is constructed properly. If you’re trying to add a storage area then I’d say keep the frame and construct a box that is retro fitted to the frame.

www.fiberglasshawaii.com

The battery packs are 5"x 10"x12" so the only option would be on top of the frame which would make it too high up, I would be hunching over to grab the handlebar. Currently there are 4 smaller batteries, two on each side of the frame.

If you really wanted to, you could definitely make the entire frame out of carbon. Have a search around here and the 'net - people have made bicycle frames from carbon and the technique and principles would be pretty much the same.

If you want to make the tube sections of the frame with an integrated box in the middle, you could do that as well, but it would just take a bit more thought to plan how you’re going to do it.

To cut the frame and connect it to the new carbon box section you would probably just need to get the frame fabricated with some mounting plates that you can bolt to the box. There’s just so many different ways that you could go about it - single mounting plates on the ends of the cut tube sections, a metal frame that runs around the perimeter of the box, under the box etc…

If you have never made anything with composites before I would suggest making some test pieces first up. For example maybe some 10x20" flat sections and experiment with core materials, then you’ll start to get an idea of what kind of base you can make. Once you start making test parts you’ll get a much better idea of what’s possible and the properties of different layups, core materials etc.

I have seen many video’s of bicycle frames being made. Not sure about using carbon tubes though, I wouldn’t trust myself making the joints.

I can not believe I didn’t think of mounting plates. Some 4 bolt mounts on the front and back of the frame would be perfect. I know a guy who does welding, I will contact him. Maybe my next project will be a battery pan with carbon tubing to match the stock metal wheel mounts. That could be profitable to sell if I can get it right!

Your right for now just making some sheets sounds like a good starter project, I might clone the wood deck as a starter project. After some searching it looks like I need a vacuum pump and vacuum materials first. I already have an infrared heater to use with high temp resin I have been looking at.
http://www.ebay.com/itm/EPOXY-RESIN-HIGH-TEMPERATURE-FIBERGLASS-CARBON-FIBER-CASTING-ELECTRICAL-POTTING-/310403241063?pt=LH_DefaultDomain_0&hash=item4845799467

[mugget]

Yeah, not sure how you will go with finding videos of bicycle frame process, you may have to settle for a plain old words and pictures.

Check out these for a start:
https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDoQFjAB&url=http%3A%2F%2Fwww.instructables.com%2Fid%2FHow-I-built-a-carbon-bike-frame-at-home-and-a-bam%2F&ei=p5F_UYCtDcTliAeWxoG4Dw&usg=AFQjCNFyTC1BPWnDXR7DR9OwOx10taRKuw&sig2=F1bNweC7zCeglYmEwXqRWw
http://theprojectjunkie.com/composite-bicycles/homemade-carbon-fiber-bike-project.html

Even if you don’t go all-in with this right now, it’s good to know what’s possible!

Also I’d hold off on diving into vacuum and infusion gear etc. I’d say you could easily do it all with regular old hand/wet layup. Maybe even no need for the high temp resin. If you skip hand layup and dive right into infusion you’d really be going in at the deep end… and I’d say it could even make things difficult for you if you don’t have a good concept of wet layup.

[chips2481]

Yeah, not sure how you will go with finding videos of bicycle frame process, you may have to settle for a plain old words and pictures.

Check out these for a start:
https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDoQFjAB&url=http%3A%2F%2Fwww.instructables.com%2Fid%2FHow-I-built-a-carbon-bike-frame-at-home-and-a-bam%2F&ei=p5F_UYCtDcTliAeWxoG4Dw&usg=AFQjCNFyTC1BPWnDXR7DR9OwOx10taRKuw&sig2=F1bNweC7zCeglYmEwXqRWw
http://theprojectjunkie.com/composite-bicycles/homemade-carbon-fiber-bike-project.html

Even if you don’t go all-in with this right now, it’s good to know what’s possible!

Also I’d hold off on diving into vacuum and infusion gear etc. I’d say you could easily do it all with regular old hand/wet layup. Maybe even no need for the high temp resin. If you skip hand layup and dive right into infusion you’d really be going in at the deep end… and I’d say it could even make things difficult for you if you don’t have a good concept of wet layup.

I saw video’s on youtube. I like that bamboo frame. Might look into doing that for a bmx bike.

Yes maybe you are right about jumping in. Well I will start with the deck of this scooter as my first project to get a feel for it, it is about 12"x20" in size. Any recommendations on where to buy resins and fabric? How thick would you recommend for the deck and how much fabric and resin would be needed? The stock deck is a quarter inch thick of wood.

[canyon]

Chips
The the amount of fabric you need depends greatly on the fabric. I would suggest using a core of some type, either foam or wood, and overlaying on that.

Roughly guessing 4 layers of heavy weight carbon fiber on each side of the core should be sufficient to support a 200lb rider, especially since the lengths you’re looking at aren’t terribly large.

[chips2481]

Chips
The the amount of fabric you need depends greatly on the fabric. I would suggest using a core of some type, either foam or wood, and overlaying on that.

Roughly guessing 4 layers of heavy weight carbon fiber on each side of the core should be sufficient to support a 200lb rider, especially since the lengths you’re looking at aren’t terribly large.

Thank for the reply. 12k or 6k thickness? I was thinking of getting a pump since I am finding some for around $100. Will that help with the strength?

[kylecurts]

Thank for the reply. 12k or 6k thickness? I was thinking of getting a pump since I am finding some for around $100. Will that help with the strength?

Hey Chips,

The #K stands for the number of fibers in each bundle of the weave. Not all fibers are the same and the bundle can be spread out flat or more bunched such that the fabric thickness can vary dramatically. For example a 3K weave can be thicker than a 12K weave. If you’re not doing FEA to analyse the strengh then you’re just guessing at thickness so i suggest you use something on sale and something highly compliant like 8H Harness weave (my new favorite). Target about 8 layers, more in the joint areas…

I’d also suggest you go straight for wet layup and vacuum bag. I bought a used pump for $40. The biggest thing i learned with vacuum bagging is that you want to use the right materials…Woven coated peel ply, batting, flexible bag, and actual vacuum bag tape!!! Cutting corners will just cause you grief. But overall its pretty inexpensive and you can get great results.

Here is a link to the design and build of my first Carbon Fiber frame :http://www.curtsdesign.com/projects/carbon-fiber-bike-frame-i/

good luck!

-Kyle-

[chips2481]

Hey Chips,

The #K stands for the number of fibers in each bundle of the weave. Not all fibers are the same and the bundle can be spread out flat or more bunched such that the fabric thickness can vary dramatically. For example a 3K weave can be thicker than a 12K weave. If you’re not doing FEA to analyse the strengh then you’re just guessing at thickness so i suggest you use something on sale and something highly compliant like 8H Harness weave (my new favorite). Target about 8 layers, more in the joint areas…

I’d also suggest you go straight for wet layup and vacuum bag. I bought a used pump for $40. The biggest thing i learned with vacuum bagging is that you want to use the right materials…Woven coated peel ply, batting, flexible bag, and actual vacuum bag tape!!! Cutting corners will just cause you grief. But overall its pretty inexpensive and you can get great results.

Here is a link to the design and build of my first Carbon Fiber frame :http://www.curtsdesign.com/projects/carbon-fiber-bike-frame-i/

good luck!

-Kyle-

Kyle,
Thanks for the info. Could you help me out finding supplies? The thickest I found was 5h. I can not find vacuum bag or tape materials either.

[kylecurts]

The best place I’ve found to buy carbon fiber is: Soller Composites. They have a funky looking website but they have the best prices and selection. They list thickness along with weave and fabric size.

You could actually get all your other supplies there too (epoxy, vacuum bag supplies). I use the WEST system 105 epoxy and 205 fast hardener with the auto-measuring mini pumps. Really nice quality stuff.

I would probably piece together your vacuum bag supplies instead of getting a kit just because he size and complexity of your project will lead you to different peel plys and bag materials.

Remember if you’re cutting kevlar, you’ll need special shears.

-Kyle-

[chips2481]

The best place I’ve found to buy carbon fiber is: Soller Composites. They have a funky looking website but they have the best prices and selection. They list thickness along with weave and fabric size.

You could actually get all your other supplies there too (epoxy, vacuum bag supplies). I use the WEST system 105 epoxy and 205 fast hardener with the auto-measuring mini pumps. Really nice quality stuff.

I would probably piece together your vacuum bag supplies instead of getting a kit just because he size and complexity of your project will lead you to different peel plys and bag materials.

Remember if you’re cutting kevlar, you’ll need special shears.

-Kyle-

Great! That is a much better source then the others I had been looking at. I don’t see any rated at 8h however I am guessing the thicker .023" is probably it. 8 layers would be about 2mm thick minus any extra thickness from the epoxy, would that be enough? I was looking at their vacuum bagging starter kit, I do have a 6cfm air compressor, would their vacuum generator work as well as a pump?

[kylecurts]

The 8HS is listed under the 3K Harness-Satin section…its 0.011" thick. If you’re worried about the strength then check out their Unidirectional Fabric…Lay it up in the long axis, then at 30 and 45 deg every other layer. Those are general rules of thumb for pure bending, torsion, and shear stress. If you’ve never worked with Carbon Fiber before you’ll be amazed at how strong, stiff and light your frame will be. Especially with thick frame cross sections. You’ll definitely want to do a test wrap of a chunk of foam or something to get the hang of it and get a feel for the strength.

I’ve never used the those venturi style vacuum generators…i think the idea is to pull a vacuum with it and close a valve…but in my experience i never get a perfect seal so i just let my little diaphragm pump run the whole time. They’re rated for continuous duty. I use something similar to this on on ebay.

[chips2481]

The 8HS is listed under the 3K Harness-Satin section…its 0.011" thick. If you’re worried about the strength then check out their Unidirectional Fabric…Lay it up in the long axis, then at 30 and 45 deg every other layer. Those are general rules of thumb for pure bending, torsion, and shear stress. If you’ve never worked with Carbon Fiber before you’ll be amazed at how strong, stiff and light your frame will be. Especially with thick frame cross sections. You’ll definitely want to do a test wrap of a chunk of foam or something to get the hang of it and get a feel for the strength.

I’ve never used the those venturi style vacuum generators…i think the idea is to pull a vacuum with it and close a valve…but in my experience i never get a perfect seal so i just let my little diaphragm pump run the whole time. They’re rated for continuous duty. I use something similar to this on on ebay.

The unidirectional stuff looks good. I will plan on using that. I actually have a carbon tube that is 1mm thick and it is as strong as ever. Any idea the cfm rating on that pump you linked is? I found another that is 6cfm for $125.