1/4 Scale R/C F1 (Regarding Chassis and suspension)

[747heavy]

747, I'm pressed to think of something that would do justice as an expression of gratitude; really useful finds, thanks again

Hi newyorkkopter,
I´m happy to help you, if I can - not much thanks needed.
I would be happy to see you start and later finishing your project, because
I´m sure, that you will learn many useful lessons along the way, and that it is
a good thing to do.

Here a photo, so that you can see how a F1 monocoque is built up.
You don´t need to really shap the core material (honeycomb).
It is used as sheets with different thickness for different parts of the monocoque.

For your model, I would not try to use honeycomb, as it will be very difficult to bond it propperly to the outer/inner carbon skin, if you don´t have pre-preg carbon cloth and a autoclave.
For your model, I would use a foam or balsa wood core, and try to get some vacuum baging. Please remember, that at the points, where you want/need to fix something to your monocoque ( e.g. where your suspension pick up points are, or where you connect your engine and nose cone), you will need aluminium hardpoints, so you will need to locate them when you layup your monocoque.





Good luck !!!! & have fun

[flynfrog]

747, I'm pressed to think of something that would do justice as an expression of gratitude; really useful finds, thanks again

Hi newyorkkopter,
I´m happy to help you, if I can - not much thanks needed.
I would be happy to see you start and later finishing your project, because
I´m sure, that you will learn many useful lessons along the way, and that it is
a good thing to do.

Here a photo, so that you can see how a F1 monocoque is built up.
You don´t need to really shap the core material (honeycomb).
It is used as sheets with different thickness for different parts of the monocoque.

For your model, I would not try to use honeycomb, as it will be very difficult to bond it propperly to the outer/inner carbon skin, if you don´t have pre-preg carbon cloth and a autoclave.
For your model, I would use a foam or balsa wood core, and try to get some vacuum baging. Please remember, that at the points, where you want/need to fix something to your monocoque ( e.g. where your suspension pick up points are, or where you connect your engine and nose cone), you will need aluminium hardpoints, so you will need to locate them when you layup your monocoque.





Good luck !!!! & have fun

for a 1/4 scale rc car i dont think core is needed also AL harpoints are not really need either. The loads the car will see are pretty small as long as the hole fit is good strait carbon or even glass will be fine. You do bring up a good point that has been missed in this thread. DFMA there is no way any of us could afford to build this car with the amount of machining that will need to be done. It would be much better to spec off the shelf stuff. They do make 1/4 scale rc cars. things like hubs wheels brakes could be speced from there. maybe make your won suspension arms and go with a double deck chassis you might have a chance at making the car.

[marcush.]

builing a realcarbon monocoque would be something of course and prepregs are not really needed .
look into resininfusion technique ,here is a basic comarison of advanatges for ri
=SCRIMP

http://www.fram.nl/workshop/controlled_ ... on/cvi.htm
and how it works

http://pslc.ws/mactest/scrimp.htm



http://www.bacuplast.de/sandwich/honeyc ... dwabe.html

I feel a 1/4 scale model could really be something ..using original build methods
of top and bottom halves of the tub joined by a bonding process .

Corecell diameters down to 3mm are available in thickness down to 1.5 mm I feel this is reasonable thin to accomodate in a quarterscale chassis.
Of course the buildup will be anything but straightforward to get core between inner and outer skins the tooling will be considerable...

[747heavy]

some youtube videos about 1/5 F1 cars can be found here.

http://www.youtube.com/watch?v=yZf91RNa ... re=related

maybe this forum can also help you in the future:
http://www.rctech.net/forum/

[747heavy]

[youtube]http://www.youtube.com/watch?v=bPYmqVBd ... re=related[/youtube]

[newyorkkopter]

oh okay thats what I was thinking regarding the 3 arm idea(adjustable tie-rods)

shim adjustment normally.
some parts are purposemade to give a special geometry
also a possibility is fixing brackets with different heights

ahh that makes sense. But would shimming be used something other than track adjustment?
By the way fixing brackets with different hieghts sounds like a good idea. Thanks!

Hi newyorkkopter,
I´m happy to help you, if I can - not much thanks needed.
I would be happy to see you start and later finishing your project, because
I´m sure, that you will learn many useful lessons along the way, and that it is
a good thing to do.

thanks man
once again, excellent pic

I'm trying to avoid maching because I don't really have the know how to make such parts. So I think I'll go with with composite uprights, arms, maybe even brackets as well.

I could look into off the shelf parts, it might make things easier; like FG's mechanical braking system, for example.
hmm, maybe

But regarding honeycomb, how does honeycomb increase stiffness?
Does do it by increasing the distance between the carbon on one side from the other?
If thats the case does the concept work something like this?
two sheets of metal close to each other would probably be easier to bend than two sheets of metal father away from each other?
Is that it?

[747heavy]

in short yes, this is the concept.
You increase the crosssection of the part, that makes it more stiff.
But you want to do so without adding weight.
Think about bending a tube compare to bending a bar.



I think, it will be difficult to do such a model without machining parts, but you can do a lot with a file and a drill machine. I used to do it, when building my models, it takes just more time.
I think, making a composite upright, which woks and is stiff enough in this small scale will be very very difficult. Keep in mind, that composites (at least the once you are going to use in your model) don´t like hight temperatures. This will but some limitations on what you can do and can´t do.

Shims on race cars, are/can be used in toe-links (toe adjustments), push/pull rods for right height adjustment and at the upights for camber adjustments.
You have some other areas, like for Ackerman and bump/roll steer, but the first three are the most common - IMHO.
It´s a quick and error poof system, but at times it´sa a bit more heavy then a simple knuckle with threads on both sides.

[marcush.]

without tools there is no ways to make this happen.The cf composite route is demanding all the machining plus vacuum bagging ,mouldmaking etc ..you need to have a reasonable stock of machinery..but I think based on a dremel one can go a long way when working quarterscale....it depends on how versatile you are..

[newyorkkopter]

Sorry; was checking out hoverboards, hovercrafts and other things. Pretty cool, but time to get back into the 1/4 scale project.

gotcha, yea that makes sense that shims could get heavier

but I think based on a dremel one can go a long way when working quarterscale....it depends on how versatile you are..

Thanks; I do plan on dremeling, drilling, and screwdriving
Its stuff like machining an upright that I'm trying to avoid
Maybe I could make an upright out of solid urethane...maybe

wow!4x the distance and the strength and stifness shot up over 9x!
Pic made alot of sense, thanks for that

Okay so, F1 wings

Why is the wing in the middle twisted up?
by the way, is that what they're called or are they called elements, like in this case, the rear wing middle element?

[747heavy]

a photo, to show the location of camber shims



I´m not 100% sure what you mean with "twisted up" in your wing question.

The upper part of your picture shows a three element wing.
The total wing shown, would be a 5 element wing, but in reality it is a three element wing + a two element wing (beam wing)







some reading here:
http://www.sm-designs.ndo.co.uk/aerofoildata.htm
http://scarbsf1.wordpress.com/2010/03/0 ... -stalling/

[riff_raff]

newyorkkopter,

When designing a 25% scale model, you need to remember that the laws of physics do not scale linearly. The characteristics of structures and aerodynamic surfaces tend to vary exponentially with size. In other words, the smaller they get the more sensitive they quickly become to tolerance errors.

As for the reason for using honeycomb in composite structures, the honeycomb transfers shear loads between the composite outer skins. This basically increases the buckling load limit of the composite structure's section without adding much weight.

Good luck.
riff_raff

[newyorkkopter]

hey nice pic with the shims!
What I mean by twisted up is like why its not at the same angle of attack as the other elements
Wouldn't an element like the one all the way at the bottom(something more horizontal) be a better, more aerodynamic choice?

When designing a 25% scale model, you need to remember that the laws of physics do not scale linearly. The characteristics of structures and aerodynamic surfaces tend to vary exponentially with size. In other words, the smaller they get the more sensitive they quickly become to tolerance errors.

hmm so copying a full size F1 wing wouldn't be the best idea right?
Is there general rule to follow when designing wing profiles and elements?
I want the car to have noticeable, functioning downforce.
What's a good way to go about this?

Pic

[mep]

The space where wings can be placed is very limited by the rules so the teams are forced to make the best out of it. I think the bottom element is inclined like that to guide the air down to increase the angle of attack to the second and third element.

hmm so copying a full size F1 wing wouldn't be the best idea right?
Is there general rule to follow when designing wing profiles and elements?

Well generally speaking the Reynolds number is interesting when scaling wings down.
Take a plane as example. The bigger the wing becomes (higher Re number) the thicker the profile can be. So when you want to scale a wing down you go for profiles with reduced thickness. On some point this can become a problem because you can get into trouble to make a very thin profile strong enough.
On a race car they usually use very thin profiles even on full scale, so get further reduction is even more difficult.
Anyway I think a wing on a race car is far from being optimal so you I don't see much trouble to copy them. In the end with your low car speed it doesn't make big differences and your car doesn't need to fly like a airplane does.

[747heavy]

Hi Newyorkkopter,

if you want to play around a little bit with single wing profiles, maybe you
download this program.
It will give you some basic ideas about lift, drag and stall angles etc.
Have fun:

http://www.grc.nasa.gov/WWW/k-12/FoilSim/index.html



basic camber shim layout for race/road car:



another race car solution
camber shims in different colors/thicknesses for easier/quicker handling


one of the solutions used on another R/C cars

[newyorkkopter]

dude! that program is so cool!
By the way is it fairly accurate?
Excellent find and nice pics once again!

I think the bottom element is inclined like that to guide the air down to increase the angle of attack to the second and third element.

That makes sense, but couldn't you get a similar angle of attack without guiding the air down?
Does air going down then up have a slingshot effect or something?

your car doesn't need to fly like a airplane does

hah yeaa you have a point