Making a carbon fiber chassis the novice way

[JosephS]

I guess the other way to make a mold would be to vacume form it , not to difficult to make a rough and ready vacume former with a hoover and a hot air gun .
By the way I'm very interested in how you get on , a very interesting project .

Can you explain that more? How would you imagine that working for this?

I was going to look into thermoforming for my learning project. The initial idea was to make a replica t2 motor guard out of kydex, but that can always change.

[Dadio]

Well much like a Lexan body but using the original chassis as a buck and pulling a vacuum former Lexan mold over the top , you may even be able to do a pair , one outer and one inner so you could get a perfect outer and inner finish .
There are a number of tutorials on YouTube on making a DIY vacuum forming machine but in essence you hold the flat Lexan sheet in a frame and heat it with a hot air gun till it droops then lower it over the chassis that's placed on a box that has a perforated top and a good fit with the frame and pull a vacuum in the box with a vacuum cleaner to suck the Lexan tight onto the chassis and holds it till the Lexan cools , it's another thing I've looked into and on my list of things to try one day .

[jwscab]

this stuff, polyethylene sheet, is what you want to use as a liner, as nothing sticks to it. it may be helpful for creating a smooth surface?
https://www.mcmaster.com/8651K92/

[JosephS]

this stuff, polyethylene sheet, is what you want to use as a liner, as nothing sticks to it. it may be helpful for creating a smooth surface?
https://www.mcmaster.com/8651K92/

I would need to add supports to the outside of the mold so that it doesn't deform when trying to make a part, unless this is an exceptionally rigid material.

something along this idea would be sheet wax.
https://compositeenvisions.com/product/sheet-lining-wax-for-carbon-fiber-molds-12x24/
it basically makes a perfect surface for part layup at the cost of some increased dimension. I can then just lay the mold material on-top and have a perfect surface.

the proper way to do this would be a kit like this
https://compositeenvisions.com/product/mold-making-starter-kit-1653/
pricing out the individual pieces this kit is a bit expensive, but not outlandish. I should be enough to make 2-3 chassis molds that are of good quality.

I'm seeing how much I can get done with what I have first. I had these materials for nearly a decade before I tried my second attempt at a chassis. I expect to putz around with this for a few more days before getting on to something else.

[JosephS]

Well much like a Lexan body but using the original chassis as a buck and pulling a vacuum former Lexan mold over the top , you may even be able to do a pair , one outer and one inner so you could get a perfect outer and inner finish .
There are a number of tutorials on YouTube on making a DIY vacuum forming machine but in essence you hold the flat Lexan sheet in a frame and heat it with a hot air gun till it droops then lower it over the chassis that's placed on a box that has a perforated top and a good fit with the frame and pull a vacuum in the box with a vacuum cleaner to suck the Lexan tight onto the chassis and holds it till the Lexan cools , it's another thing I've looked into and on my list of things to try one day .

I wonder if this would work with an air hocky table.

[jwscab]

pump needs to be pretty substantial. But you could use the table for the perforated surface with a good pump.

[Dadio]

Well much like a Lexan body but using the original chassis as a buck and pulling a vacuum former Lexan mold over the top , you may even be able to do a pair , one outer and one inner so you could get a perfect outer and inner finish .
There are a number of tutorials on YouTube on making a DIY vacuum forming machine but in essence you hold the flat Lexan sheet in a frame and heat it with a hot air gun till it droops then lower it over the chassis that's placed on a box that has a perforated top and a good fit with the frame and pull a vacuum in the box with a vacuum cleaner to suck the Lexan tight onto the chassis and holds it till the Lexan cools , it's another thing I've looked into and on my list of things to try one day .

I wonder if this would work with an air hocky table.

That would be huge but you could tape off most of it and use a good vacuum cleaner .

[Frankentruck]

I wonder if this would work with an air hocky table.

Playing air hockey is the correct use of an air hockey table. If only I had an air hockey table.

[JosephS]

Getting back to it. Since I know now that I will have to bag the part I decided to test laying the material and bagging. So no resin for this attempt.

Now this that is glued to a board I can tack down the fabric as I test relief cuts.

The front of the chassis is pretty straight forward. Looking at the top there aren’t wrinkles that need to be worked out.

The rear is another story. There are 2 main pain points. The first is the chassis angle as it plunges towards the bulkhead. The angle is sharp enough all on it’s own to wrinkle. The next is the location of the bulkhead support. It’s just all sorts of trouble.

I am trying a variety of cuts to see what gets the best coverage. There are a lot of different ways to try and I don’t think it’s too critical for the mold as long as I have enough support. I think that I will have the exact same problems when molding the part so I am trying to come up with something that looks ok.

Now that it’s tacked up I can put it in a bag and see how well it handles vacuum .

I am glad I went through this with no resin first.

This showed some problems i didn’t know I had. Wrinkles and voids are bad.

Even the front of the chassis will need some relief cuts. There is a corner wrinkle.

The bag is not big enough for the the project with the board attached. There isn’t enough material for it to full draw down around the rear bulkhead support.

The force of the vacuum is enough to bend down the rear plate.

Since I am not using a real vacuum system I am also now worried that the speed is to fast for working out the bag.

I have a larger bag that I will try. Unfortunately it is finicky to seal properly.

I can add some relief cuts to the front seams.

I can try to pull the vacuum slower and hope it still is enough to get a good fit for the mold.

Fiberglass is good to go by surface applying resin. Carbon fiber requires some additional force(vacuum) to pull the resin into the fibers to develop strength.

It maybe to cold today for me to try any resin.

Supporting the rear may be a challenge.I can try cutting in a piece of wood at the end and shim it to keep the geometry correct.

[JosephS]

Thought of a different way to slice up the cloth.

This one cuts a straight strip out along the widest point in the chassis and tries to wrap it straight back. The rest of the material is cut out and folded over.

I don’t feel like I have enough coverage on the bulkhead mounting tab since the folded cloth goes over the last angle of the chassis. Still this seems like it’s worth trying. I may try 2 alternating patterns to build up support in the corners.

[JosephS]

The weather is getting warm enough again to start working towards a layup.

I am working towards a fiberglass mold, but also trying to learn what is involved in making carbon fiber.

I want to have at least a couple of mm thickness for my mold, even if I Ian going to add reinforcement after my initial layup.


Cutting fabric is a skill.

Unrolling the fabric without disturbing the weave is challenging. For this step it’s not critical, but I want to attempt to have a good weave for a final chassis.
What seemed to work best was to pick up the roll, then unwind the width I needed. Pulling on the edge makes a wave I can’t smooth out.
Even with unrolling there was a wave in the edge that was just cut straight. I may need to watch some sewing videos.

Each layer of fiber is about .1mm I piled up 19layers to get 2.0 mm. I’ll have to measure again after the resin is applied to see if any appreciable thickness is added.

I think I will have to cut the pieces to pattern one at a time. The thickness of fabric is enough to displace the bends in the fabric if I cut them all the same.

Now I need to figure out how to brace the rear of the chassis against the pull of the vacuum pump.

[JosephS]

Had a bit of insomnia so started looking ar resin to fiberglass cloth ratios. Most of what I found was for epoxy, but I’ll assume the polestar resin will be similar.
To get a wet out and a coat it seems to be that the ratio is between 2 -2.5 oz of resin per oz of cloth.
This should be enough For wet out and a coat.

783F2CC2-6C86-4B6A-BA17-FC7C918297C8.jpeg (23.06 KiB) Viewed 1040 times

783F2CC2-6C86-4B6A-BA17-FC7C918297C8.jpeg (23.06 KiB) Viewed 1040 times

The scale is reading about v2 7oz so that would be a 14-18 oz of resin which is a whole lot of resin to work with.

The temps are begin get in the right place to start up again. Though I have read that the bigger the batch of resin the faster it cures and the hotter the batch would get.

I should have enough resin left to try this. Now I need to figure out the support

[Benders]

I totally figured I’d see it cut from cf sheet…back in the day when cf was new to the scene I had a rc10 that was converted to a stadium truck before the st came out and it ran a flat pan made from cf sheet…it looked somewhat similar to the carpet racers back in the day…man was that thing quick! Was the fastest thing in the novice class where I raced as a kid…

[JosephS]

I totally figured I’d see it cut from cf sheet…back in the day when cf was new to the scene I had a rc10 that was converted to a stadium truck before the st came out and it ran a flat pan made from cf sheet…it looked somewhat similar to the carpet racers back in the day…man was that thing quick! Was the fastest thing in the novice class where I raced as a kid…

A sheet would be the best and cheapest way to get something that can be driven. The GT nose brace supports can be fitted to give the front end and the motor guard from the T2 and the graphite both allow for mounting to a flat rear. I'm sure something simple can get worked out for the rear bulkhead supports.

I'm trying to learn a new skill and see how I do just for the fun of it . I don't know if I will make anything that would be strong enough to drive, or good looking enough to put on a shelf. I've already learned a bit and very much appreciate professionally made carbon fiber pieces.

Fiber reinforced plastic multiplies the difficult parts of cloth design and plastic fabrication.

[juicedcoupe]

I'm sure something simple can get worked out for the rear bulkhead supports.

The bulkhead wasn't attached to the sides on the graphite cars. It was attached to the bottom of the chassis and the transmission brace.

The side attachment on the aluminum pan is to reduce the chance of bending the aluminum. Graphite doesn't have that problem.