Making a carbon fiber chassis the novice way

[Benders]

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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.
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And the learning curve will always make it worthwhile if it looks good for the shelf or runs or not…by attempting it you are giving yourself a new skill…and that my friend is a win no matter how you score it!!!

[JosephS]

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.

I have no idea why I haven't noticed that before. I have been pretty focused on making sure that the chassis tabs lock into the bulkhead. I was assuming that the chassis would not be rigid enough.

[Benders]

One I had was really rigid…granted it’s been 30+ years ago and I don’t remember exactly how it was built…I traded around for it as a complete car back then…but I do remember that it was a flat sheet of cf I’d probably say 2-3mm thick and I always figured whomever built it cut it out on a bandsaw or something and then sanded the edges…it was a nice build don’t get me wrong but it was very simple as well…had Velcro straps riveted in to hold the battery pack and the esc was double back taped on the bottom…I can still see that thing thinking about it right now…

Thank you for reminding a old man of some good memories

[juicedcoupe]

I have Graphite, TQ10, and Composite Craft chassis. They all feel more rigid than my aluminum cars.

[JosephS]

I went ahead and did a test vacuum pull with the new bag and the attempted rear end supports.

I tried to fix the flex in the rear by drill though the cardboard and foam and using 1” piece of pencil to bolster the stiffness. I also switched to a pleated bag with that can hold a much bigger area.

I did this with the 2mm of material but left it uncut. I also increased the length of the bag and used a slower pump speed to give me more time to work out wrinkles.

The new bag is much larger than the old one and it should be much easier to move a resin covered piece into the bag.

The overall result is better than before even using much more fabric. It looks aesthetically

I think the edge is better with a smaller flange area as the cardboard backing warps and produces an angled surface. I need to place some backing under the supports. They help a lot with flex and I think with a plate underneath it will be good enough to make a mold.

It looks like the next step will be cutting fabric and making a mold.

[Benders]

While I’ve never fooled with cf cloth I can tell you from experience that a floral foam plug wrapped in masking tape works real well for fiberglass and the resin won’t stick to the masking tape. If I remember right, I used 2” masking tape and did 3 layers, but the last time I made a fiberglass part was 8-9 years ago and I suffer from CRS but the plug would help you retain its shape as you pull vacuum on it. Are you going to use hoses to draw the resin into your part as you're pulling vacuum? Personally I’ve never used vacuum to make parts but I know the process to do it. I just never had something to pull the vacuum.

[JosephS]

How was the smoothness on the inside? Did the tape leave lines on the parts?

[Benders]

I took my time with the tape making sure it laid down flat, and that each layer overlapped the last but the inside wasn’t bad at all. You’ll get a little transfer on your edges but nothing bad as long as you get the tape to lay flat. I’m told aluminum foil will work also but I wasn’t brave enough to try it due to the transfer of wrinkles and such as I was using the piece for a mold The edge transfer from the tape I was able to lightly sand out.

[JosephS]

So the cheapest tub pan take 2 had to fail so I could learn enough to continue on to this project.

Alcohol and alcohol based hand sanitizer is a magic cleaner for unset resin. It works even better than acetone.

I'm going to go about making the buck for this process in a whole different way based on my experience with the cheapest tub pan2 project.

The color on t2 aluminum is fragile. I have a completely different tub where I rubbed off the color and was left with hard grey anodize.

I'm going to coat a clean chassis with PVA then very use spray adhesive to attach fiberglass cloth to the chassis. I'm going to coat that in epoxy While that piece is curing I will use some clamps to apply a bit of pressure at the ends of the chassis to hold it to a smooth ceramic tile so the part cures flat. That part will be the buck to build my mold. So I'll have a piece of aluminum backed glass that I can add epoxy to and smooth out. There will be no holes, scratches or other defects giving me a perfectly smooth surface to cast a mold from.


Lets see how that sorts out tomorrow.

[JosephS]

The carbon fiber is basically done.
I still need to do a cosmetic layer of carbon fiber and epoxy.
Trim all the edges
drill and counter sink all the holes

I didn't understand how much stronger the carbon fiber would get on the second day of cure so this chassis is 2.6mm thick.About 7 layers of carbon fabric were used. It's very over built at this point. Now that it's approaching full cure it's quite stiff.

The original aluminum chassis is 2 oz heavier and only 1.7 mm thick.

I'm not exactly sure how to drill all the holes so everything lines up correctly. As well what counter sinks should I be using?

Also it's kind of challenging to take pictures of carbon fiber. How do I light it to so more than just a black shape?

[JosephS]

Progress pics.

I added the last cosmetic layer and the chassis is now an even 3mm thick. Very much overkill but it’s going to run just fine. I taped up the outside and started trimming. The t2 has a lot of variations on the side wall height.

[JosephS]

The sides are trimmed and the tabs are cut into the back. The chassis is about 5 mm longer than stock

[Dadio]

That's really coming along , I love the idea of FRP but every time I use it all I get is an oogy mess

[JosephS]

That's really coming along , I love the idea of FRP but every time I use it all I get is an oogy mess

I'll have to see how it holds up but it took a few tries to get something that looks like it could work. The big improvement that I made was using less resin in my layup. If you followed my cheapest tub pan 2 thread I basically made that into a solid block of CF by using an excessive amount epoxy. It also turns out that clean anodized aluminum is a great mold and releases well. This chassis was supposed to be a wrap for my busted t2 chassis. Even without any release agent, polish or wax the carbon fiber released from the chassis.

I'm already using this experience to plan my next project. The 3mm thickness makes the nose piece look a bit out of place. I think 2mm would fit nicely while still being stable. I may try making an all in one chassis with an built in nose piece to avoid fitment issues. I may also try and make nose pieces as well.

From a material standpoint fiberglass or kevlar would both be better for a nose piece since they will be heavier as well as more impact resistant. They will flex where CF will crack. I've also yet to encounter a situation where I want there to be less weight at the front of these rear motor cars.

Back to this one. I have to do a small repair to one of the tabs then start drilling holes. I'm not experienced in making precision parts. I am not sure how to go about setting up to drill all the chassis holes so they all line up when pieces are mounted,

[JosephS]

So I had not really noticed before but the t2 rear bulkhead has guides on the side.

I had to re cut the sides of the chassis so the the top of the bump actually fits over the chassis.

Now I am onto the nerve wracking step of drilling.
I have not had to ever precision align multiple holes. I need to get the distances right on each part so they will attach correctly, then as well align each part so that I don’t misalign the suspension.

I’m clamping the donor chassis to the taped up back and I’ll draw the holes first to see how well I do lining it up.