I could be overly ambitious, but trying to win a competition. Printing Chassis

[thedecider33]

Hello,

I am very new to this forum and have been dive bombing into everything there is to possibly know about 3d printing.

I am trying to 3d print the frame of a go kart. I have been looking into carbon reinforced plastics and I think it should work?
I am prepared to see if it will hold up to the stresses through trial and error. (a little math too)

Gaps in knowledge:
Has anyone heard of someone trying to do something similar? . . . bike frame
Does anyone know a printable material that would hold up to the stresses?
Does anyone know a printer that could possible print the chassis?
Does anyone know how to find people with the printer would work?

I have some money saved and trying to turn this dream into a reality. Any guidance you have or could provide, I would be more than appreciative! Seriously! Anything will help.

My name is Drake and I want to thank you in advance for even reading my post.

[LambdaFF]

Sorry, it must be slf explanatory but what do you mean by "a go cart" ? Size / picture ?

[Marm]

A small dune buggy like car. Usually on road use only, but there are plenty of off roaders too. Here: https://www.google.com/search?q=go+k...ed=0CAkQ_AUoAw

Any of the filaments that are infused with anything do not usually increase layer bonding strength, just the strength of the material. Ie, Carbon Fiber infused filament may or may not have stronger tensile strength of the filament, but the strength between layers does not increase unless you do a lot of post printing work. I may be wrong on that, though.

The size of components you'll need to print.... I'm not sure 3d printing is the way to go, ESPECIALLY on a budget. You'll be hard pressed to find a budget printer that will do bigger than 12" cubed, and that's a reach. usually it's 8"-10" cubed, or some rectangular box with 8"-10" being the longest dimension. Too make a chassis, you'd have to print off a bunch of smaller sections and bond them together to make the longer elements of the frame. Joints=weakness. Although, if you have a good design, you might be able to find a company or university within your region (read 12 hour drive), that might have a printer big enough to print it in one go, or at least only a few parts.

If you want my honest opinion.... Go to harbor freight, pick up a low duty cycle Tig welder for a couple hundred. Get a bunch of titanium tubing (if you can, I have a good cheap source of Grade 1 I use, but that's me), if not, steel. Weld up a chassis. Use you CAD design to make the chassis as light but strong as you can. I think you'll be way ahead budget wise, and you'll have learned a very important skill (welding) in the process.

Yes, it's doable via 3d printing, but "some money saved" probably won't cover the cost of a printer, or maybe even the cost of having it printed. There are more experienced users in the larger printers that can offer more insight. At the hobbyist level, it's probably not practical. A lot of the smaller technical parts though.......

[thedecider33]

Thank you for both of your responses. I truly appreciate it.

So I have TIG welded this chassis :-). I have the CAD design, and want to recreate this entire frame with one piece. I could save so much time if I could easily just print a structurally sound frame.
Tig Frame.jpg

@Marm to your earlier point, you saying the a carbon infused plastic would not have a tensile strength stronger than just the plastic?

Even if it would take an expensive printer, simply knowing what material and what printer would be incredibly valuable. I'm in the theoretical trying to figure out if this is possible. Last thing I want is to ride down the street and the kart falls apart haha.

Is there a plastic that would get me close to the strength of this steel frame?

[thedecider33]

Tig Frame.jpg
Trying to get a bigger picture. I may have to take another

[LambdaFF]

I would agree with Marm on this one. 3D printing with thermoplastics cannot compete with welded metal structures for a chassis.

You could use 3D printing to print moulds more easily and make fiber carbon / fiberglass components for your cart : fairings / covers / seat...

Also recently the Mark One came out but we actually know little about it, the users are still a bit quiet and you can't make a chassis with it.

[Strongback]

I've heard of people making bike frames through 3d printing, but they're low speed vehicles and almost universally, the frame not built to deal with any form of impact.

Considering how low on the ground the frame is and the nature of 3d printed materials, I don't think you could make a frame that is actually safe to use on a go-kart, unless you redesign the vehicle, but at that point it's not really a go-kart anymore.

[Marm]

I really don't think the strength to weight ratio of a 3d printed tube would even compete with a modern fiber or alloy tube. Since you have some (fairly impressive TBO) metal working skills, I'd recommend combining the two.

Make all your longer structural parts out of aluminum. I only say aluminum as I doubt you have access to Titanium. (I learned to Tig on scrap Titanium. People are amazed I have that skill (Apparently Ti is a pain to weld), but since it was what I learned on, it's all I knew. Now when I work with steel, it's like I can make it dance to my will, it's like butter to me. If you get the chance, learn to Tig Ti). Design all the junctions in CAD, and then print those. Do it right and you will only have to use bolts to secure it all together.

Now... If you really want to get crafty, learn to form Carbon Fiber molds. You can get bulk CF fabric fairly cheap, I've used to help build racing sailboats. Use the CAD to design your hybrid chassis, but design the longer structural elements with CF in mind. You can make really weird shapes if you need. You can then slice those elements into 2d layers, and print those out (Fullscale) on a large printer. A local print shop can easily do that for you for little cost. Use these drawings to form foam boards. You then can stack the foam boards back into 3d shape of your design. Sand to smoothness, and there's your full size positive mold. Then use that to mold your CF piece, as would be appropriate for whatever method you decide to use. Google and youtube have many examples of this process. Just takes some CF, a releasing agent, a mold, a bunch of epoxy. This combined with printed technical parts may be just what you are looking for. And the CF parts would be stronger and lighter than anything 3d printed anyways.

[thedecider33]

Sorry about the late reply. Got a little swamped at work.

You guys have some great ideas. I love the carbon fiber and moulds. I have been researching a good bit about the process. Would it be easier to just print the chassis, then wrap the entire chassis in carbon fiber +epoxy then heat it to give it the structural rigidity?

I am currently thinking of ways to mix 3d printed parts and aluminum structural components to get the flexibility I want with the strength I need.

I will start a thread focussed on this project from beginning to end. I'll invite all that commented. It should be a fun process regardless.

[Marm]

Yes, you can wrap 3d printed parts with CF. I watched a video on a quadcopter built this way. The print was severely under engineered intentionally, as in it wouldn't stay together without the CF. But, from what I've been reading, if you wrap closed cell foam with CF, the Foam helps redirect stresses within the structure itself, greatly increasing the strength of the CF part. Ie, on a bent tubular element, the foam helps shift the stresses from the inside wall, to the outside wall, and vice versa.