Fiberglass Monocoque

[newyorkkopter]

Hey, I'm new here, and I 've been thinking about building a gokart with a fiberglass monocoque.
So how many layers of glass should I use, and also would some sort of core matierial be necessary for adequate stiffness?

-Thanks

 

[Russ2251]

"Experiment" is the word of the day.

Most folks here will have no idea of what you are talking about.

 

[devino246]

An entire kart structure of fiberglass? one problem i see with that is around the engine, the heat could soften the resin and mess up the structure.

 

[Russ2251]

the heat could soften the resin and mess up the structure.

It won't...no more than the sun would ruin a boat or a Corvette.

 

[anderkart]

Hey kopter, If its any help I found a little build info for ya here: http://forums.autosport.com/lofiversion/index.php/t105766.html

 

[newyorkkopter]

wow that did help thanks!
So how would I build a chassis with plywood and resin?
Would I take layers of plywood and bond them with resin?

I could cover the area with the motor with some metal so the glass doesn't come into contact directly with the heat, maybee

ahh experimenting is probably necessary, but still, do you have any general pointers?
Like how many layers, what weight of glass, etc. to try get the required stifness

anderkart, do you have more info regarding resin bonded plywood construction?
Would a kart built like that be able to compete with steel tube frame karts?

 

[Russ2251]

I could cover the area with the motor with some metal so the glass doesn't come into contact directly with the heat, maybee

The fiberglass will not get hurt. Engine mounting base remains relatively cool. Engine heat is not (and should not) be a concern...by any stretch.

 

[Doc Sprocket]

Any reason you want to avoid a steel frame?

 

[Kenny_McCormic]

Any reason you want to avoid a steel frame?

Weight, properly designed, a glass over foam unibody would be WAY lighter than a steel chassis.

 

[sideways]

The Lotus Elite was a sports car with a fibreglass monocoque, it used fibreglass 3/8" thick in highly stressed areas and 1/8" in unstressed areas. It did however use a metal sub frame to hold the engine and front suspension, it also used a metal hoop welded to to pieces of RHS to hold the windscreen, to mount the door hinges and to provide jacking points.

The Lotus monocoque was done in three separate layers, first there was a floor pan layer then a mostly structural layer then another layer for the body. the front subframe was mounted between the first 2 layers.

I hope that makes sense.

Thanks

Hayden

 

[sideways]

I just looked it up and found this picture. It explains what I said above much better.

 

[Mac]

They built Three-Wheelers without a steel framework back about 1967:
.

Sperry Rand " Tricart "

 

[Doc Sprocket]

There are substantial differences between karts and cars. It is my opinion that if the kart is to be a relatively simple on-road design, the weight difference will be negligible at best. Cost over steel will likely be higher, and certainly more work. Not to detract from anybody's aspirations, though- if you want to take a whack at it, by all means do. I just don't see any benefits in this case.

 

[tundrazach]

What kind of go-kart are you planning on building? I would not use a glass cart off road, or even on really rough roads.

But if you are building a track toy cart, I think it would be a viable design. From my experience, fiberglass gets much stronger in a "3d" shape. For instance, most yard carts are a flat steel chassis. If you used even 3/8" layered glass, I still think it would snap in half if you tried to build one of similar design. You would need an "incasing" design that can distribute the loads over a larger area.

We looked into designing and building carbon fiber monocoque frames for our FSAE competition cars at school, but it was wildly expensive (as in we could build an entire steel framed car for the price of the monocoque alone) and was going to be too large to manufacture in house and would have to be outsourced.

That being said, some teams HAVE done it. Here is an excellent presentation showing why they used the design and theres lots of good info in it to help you with yours.
http://me.sdsmt.edu/docs/83638.pdf

Also, I would use a weave mat. It has better strength properties then chop mat.

 

[newyorkkopter]

The fiberglass will not get hurt. Engine mounting base remains relatively cool. Engine heat is not (and should not) be a concern...by any stretch.

Excellent! Thanks for that

Thanks for your input guys
I’m planning on something I can use on pretty much smooth roads, not offroad or even rough roads.
I’m avoiding a steel frame because I don’t have the know how that it takes to build one
I have alittle experience, not much at all, with composites(carbon fiber) but still, I feel more comfortable going that route, for now atleast.
As Kenny wrote; there is a possible weight advantage if done properly, but again that’s not my reason why.

If you used even 3/8" layered glass, I still think it would snap in half if you tried to build one of similar design. You would need an "incasing" design that can distribute the loads over a larger area.

Ohh okay thanks for that. I was thinking about a bucket-like monocoque at first, but then I thought about simplifying it into a flat chassis like the steel frames. But, after your post, now, I’m seriously thinking about going to go back to the bucket-like design

So about the Elite; it had 3 layers but with in those 3 layers were there more layers of fiberglass?
Like for example, the structural layer on top of the floor pan; was that made with only one layer of 3/8’’ thick fiberglass or was it multiple layers?

 

[DustinWolfe]

theres a great book called how to build motorcycle engined race cars from a guy named Tony Pashley that explains this in detail. its a little advanced for this forum and its not for the beginner but with a little background experience in composites it would be a great buy. this book is pretty much amazing. ive read it like 5 times

 

[sideways]

For extra strength you could easily incase steel bars in the fibreglass.

Thanks

Hayden

 

[newyorkkopter]

hey thanks, yea that could might be reallly useful for a possible project later on, but still does that book go into making stressed composite parts?

hmm steel bars, possibly, but to start things off I'm probably going to go with a plywood chassis which I could encase with layers of fiberglass

Does that sound like something good enough for a kart to have some fun in?

 

[DustinWolfe]

yea it does but something you may want to look at is aluminum honeycomb chassis construction. its sorta more high end race cart territory but imo its better than tube frame and carbon fiber for this application. strong as steel tube frame without the weight and half the cost of carbon fiber

 

[newyorkkopter]

Excellent, now would that plywood chassis be strong enough to support two people and motorbike engine?
ahh aluminum honeycomb might be pricey.
Isn't aluminum honeycomb sandwiched between layers of some material, like for example carbon fiber?
Also do know of any good places to get aluminum honeycomb?