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

[747heavy]

we have been there before, but maybe you did not read it, or you did not understood it. So here we go again:

some informations about honeycomb cores and how to use them:

http://remixshare.com/dl/so4xj/kapitel09.pdf

overview about the different production methods.
hand lay up (wet lay up), vacuum press moulding, autoclave moulding, injection moulding

http://remixshare.com/dl/9g4yb/kapitel01.pdf

keep in mind what flynfrog has said, he has a good and valid point - IMO
if you want/need to use a core material, use a closed cell foam or balsa wood as core. It will make your life easier.

Sorry, it´s not meaned in an offensive way, I doubt you have the technology and knowledge to use honeycomb core, for your project yet.
That´s nothing to be ashamed of, but you will need to walk, before you can run.
So do yourself a favor and start small/simple (no core construction), but start and learn your lessons along the way, while you are doing things.
You will have a better understanding, of what the challenges are, when you have laminated a part or two.
Try to produce some simple things, make a form of an cheap model car, or any other geometric shape, just to learn the technique. (form making, layout etc.)
Be prepared to throw the first two or three parts/attempts away, this is normal, and will happen.
That´s why I say, start with an easy shape, just to learn how to work with composites, and get used to the techniques.
Mind about undercut´s and the de-forming process, otherwise you way struggle to get your finished part out of your mould.
Don´t try to build a complicated part with core laminates on your first go. Chances are that you will be dissapointed, and maybe even damage your mould.
Therefore learn the processes first, and than go to more complex forms and structures.
You can even try to make some carbon fibre flat plates (maybe with a foam core)
to see, what the challenges are.
You can do this, between to glass plates (or mirrors) with a couple of heavy books to weight it up on top.
See what you can produce in terms of surface finish etc.
Have a read in the R+G book, it deals with a lot of aspects you will come across, such as mould/form making and preparation. O.K. they build a airplane model, but the processes involved are the same.

Good luck !!

[flynfrog]

If you really want to build the car I would make it a double deck chassis like the touring cars. You can build it out of flat plates that can be purchased. You are looking at 1000s of $ in tooling the route you are headed. The cost to machine the plug alone is going to be well over 1000 there are some low cost alternatives but they also are not that accurate. check out green power dudes thread on here you can see his buck creation.

[marcush.]

hey we are talking quarterscale here ...so the buck construction can be done on a table..
And tbh luke made life very difficult for himself and his sister with plaster bondo mix...(two hardness surfaces ...impossible to sand smooth..).

You need to be willing to learn before destroying all the expensive stuff and all the hours ... so think and ask and prepare before touching the hacksaw..

But of course a flat board can be sawed even by my 8year son...but then you can buy what is available of the shelf.Why build something that is nothing special?

[flynfrog]

hey we are talking quarterscale here ...so the buck construction can be done on a table..
And tbh luke made life very difficult for himself and his sister with plaster bondo mix...(two hardness surfaces ...impossible to sand smooth..).

You need to be willing to learn before destroying all the expensive stuff and all the hours ... so think and ask and prepare before touching the hacksaw..

But of course a flat board can be sawed even by my 8year son...but then you can buy what is available of the shelf.Why build something that is nothing special?

I was referring to flat sheets of carbon the way most RC cars built when carbon is used.

depending on the shape you want you build a foam cutter and some templates for the buck. But it will be hard to get an accurate location for the suspension pickups ect. But if he wants to custom machine all of these parts the project will never get finished. You could even have the carbon water jetted for a reasonable price.

[marcush.]

flyn..I know..my point is:Why do something that is avaialble of the shelf ...to save a few quid? I´m sure you will not be able to do this cheaper then a manufacturer ...you may be able to cut down on their profit but it will be sweat an dtears but not really satisfaction comparable of doing a true cfm-tub say a repro of the famous ATS carbonfibre chassis...

[flynfrog]

I get that my point is this car as it headed will be well over $20k. Yeh it would be neat odds are it would be slower and less sorted than the off the shelf cars. Not trying to knock anybody's project I am just offering my experience that if he ever hopes to finish the project costs of manufacturing methods must be taken into account

[marcush.]

I get that my point is this car as it headed will be well over $20k. Yeh it would be neat odds are it would be slower and less sorted than the off the shelf cars. Not trying to knock anybody's project I am just offering my experience that if he ever hopes to finish the project costs of manufacturing methods must be taken into account

hehehe..you could be right...but I´m sure doing a cf/honeycomb tub will not set you back 20K ...at least if you will not go throu shot 20 before coming up with something usable..
of course you will need to set up a proper vakuum pump ,oven...tooling block clever thinking moldmaking etc ...so anyone who thinks this is a 500bucks thing is dreaming..yes.
and if it will be quicker...I really don´t care...

[flynfrog]

no but after all of the one off pieces for the suspension brakes ect it adds up quick plus you need spares to race with

[747heavy]

another cutaway of an wheelbearing,hub/spindle and upright.
Such an layout is quite typical for a racing car.

[747heavy]

titan flexures in carbon wishbones Ferrari F1 front suspension
also note ride height adjustment via shims at the pushrod end



and cut away of an rocker



as used in the suspension

[747heavy]

locations of bulkheads in a monocoque

[marcush.]

747 ..great CAD drawings..I´m bemused by the presence of Needle type bearings in a rocker arm svivel....that seems to me a good example for ignrant engineering (I hope this was not your work... )
My reasoning:
Needle bearings do not cope well to oscillating loads
Needle bearings are not coping well with dirt (think about track,carbon dust,mechanics having to service car in the field..) and shock loads....
The failure mode of a needle bearing will also lead to a quick dnf ....so never ever I would do this ,especially in this application where you could very easily substitute the needle cage by two angular contact ball bearings with out the risk of contamination.with a decent sealing (one call with Trelleborg or even just internet research will put you quickly in the right frame of thoughts)you will not have any risk of field service issues plus you have the variable of Thrust load/end float (slack!installation stiffness,apparent hysteresis-the system is behaving differently for different starting points of a input ) covered....oh I´m again a bit too cheeky here ..please forgive...I know I´m nitpicky .

[mep]

If you really want to build the car I would make it a double deck chassis like the touring cars. You can build it out of flat plates that can be purchased. You are looking at 1000s of $ in tooling the route you are headed. The cost to machine the plug alone is going to be well over 1000 there are some low cost alternatives but they also are not that accurate. check out green power dudes thread on here you can see his buck creation.

Hola,
I don't know how you come up with such a high figure but 20.000dollar is way to much for building such a car. It should be possible to get 1:4 homemade model car for around 3.000 Euros and that’s close to the price those cars get sold in the shop. Remember its a homemade car the price therefore can be calculated different than a company would do it. For example you don't have to pay any working hours because you do almost everything yourself.

I don’t think the price will change much if you build it of composites or metals. Personally I would prefer metal because metal simply handles easier for me. Even with metal it should be easy to build a car that weights below 10Kg.

When you go with composites have a look on some model airplanes. When I was a kid I had one with a glassmaker fuselage. Basically they are build very simple. Without any core or vacuum or all this stuff because you don't need it on the small scale.

[flynfrog]

I was looking more at the cost of machining if we are not using any off the shelf parts that's a lot of small accurate machining that needs done.

[747heavy]

747 ..great CAD drawings..I´m bemused by the presence of Needle type bearings in a rocker arm svivel....that seems to me a good example for ignrant engineering (I hope this was not your work... )

no it wasn´t
so feel free to pick on it, I guess there are many ways to skin a cat.
I have seen rockers with needle bearings and rockers without, both seem to work - both have won races.

I think the sealing is not really an issue, you can seal both types in a sufficient way. Normally in a Formula or Sports car, they are in a relative "clean" location, and only need to operate for a weekend, before they get serviced again.

Needle bearings seem to be quite common for ARB and pedals (brake/clutch) as well, at least I have seen them being used in such applications.

For the task at hand (1/4 model) I don´t think it´s a big issue either way, I guess I would settle for a single ball bearing, even this is probably too heavy.