CM category suspension design

[747heavy]

thanks for the info !!
I looked at some videos on the internet.
This cars a quite fast, compare with some "real" cars like the WRC Subaru,
sure the low weight helps a lot here.

From the times you posted, it means ~112km/h average speed on this track/hill.
Seeing the inboard videos, and the many corners in combination with the motor bike engine, it means quite a lot of gear changes. That´s why I thought a pedal shift system at the steering wheel may being an advantage, so that so not need to drive with only one hand for most of the time.
Not sure, if such a system would be allowed by the rules.
It was just a thought which crossed my mind, when seeing some of the inboard videos.

Seeing some photos of the front splitter, there is maybe some scope for development/improvements there as well. Compare to the large diffusor and wing at the rear, the front aero/splitter looks very simple.
No diffussor/extractor section in the front splitter?!?
But again, maybe there are some rules against this, so I´m not sure if it´s by choice or forced by the rules.

All in all, it seems to be a nice and interesting category, with some freedom for technical developments without blowing the budget.
Just another thought, which cossed my mind, how about an CVT gearbox?

[747heavy]

just another quick question
Does this weight include the driver?
Because on the Banjo website, they claimed a dry weight of 420 kg.
I´m not sure if this is including the engine, or just for the rolling chassis.
If 550 kg is the dry weight for the car excluding driver, do theses cars use a lot of ballast weight?

[delacf]

just another quick question
Does this weight include the driver?
Because on the Banjo website, they claimed a dry weight of 420 kg.
I´m not sure if this is including the engine, or just for the rolling chassis.
If 550 kg is the dry weight for the car excluding driver, do theses cars use a lot of ballast weight?

During the competition, at all times, the vehicle must weight over 550 kg including driver, fuel, oil ... ... No gasoline, no pilot and with oil: 445 kg (minimum) with tolerance 3Kg. There are no restrictions on ballast weight

Seeing the inboard videos, and the many corners in combination with the motor bike engine, it means quite a lot of gear changes. That´s why I thought a pedal shift system at the steering wheel may being an advantage, so that so not need to drive with only one hand for most of the time.
Not sure, if such a system would be allowed by the rules.
It was just a thought which crossed my mind, when seeing some of the inboard videos.

The gearboxes automatic or semiautomatic are prohibited.

Rules: http://www.rfeda.es/docs/anuario/2010/anuario53.pdf

Then I comment on the aerodynamics. Greetings

[delacf]

Speed Car GTR:

[747heavy]

Thanks for posting the reg´s and the photos delacf.
I tried my best to read them, but my Spanish is maybe not that good, to understand all the details.
I understand that you can have max. 6 gears + functional reverse gear and that automatic or semiautomatic gearboxes are banned.
I would still think, that a pedal shift system would be permitted ( but maybe I don´t understand the finer points of the rules correct - sorry)

I also understand, that the max. overhang of the front splitter is 50 mm at the front, and that it can´t be wider then the car.
I´m not sure, if I found any reference that the underside of the splitter needs to be flat, but again my Spanish is not that good.

It looks to me, that you can only use 1 damper per wheel, if I understand the rules correct, but you could run hydraulic connections between the dampers.
The same may goes for the Anti roll bars (ARB). It´s a bit of an grey area. You could ask fo permission to run hydraulical ARB´s and interconnect the front and the rear (KINETIC system) if you think it could be an advantge.
But chances are, that people will throw it out by claiming it is more then one damper per wheel.
I´m just brainstoming here, not saying that you must or should do it, just mentioning some things which came to my mind.

Try to gather some data about corner speeds and acceleation. To me it looks like that if the corners are very tight (on therefore slow) the cars need good "power-down" and longitunal acceleration. Which may goes a bit in the direction to explain, why they run relative small camber (compare to a touring car for example).
But it can also be related to the "cross ply" tires, and I will freely admitt, that I have no expirience with this type of tire.

If camber control is a important point, maybe it is worth to consider a DAX or OCP type of suspension at one point.
I would not start out with one, but maybe something to keep in the back of your mind for later.

The brakes seems to be an area with a lot of technical freedom, apart from the ban of carbon/carbon brakes.
But if I read the rules correct, you could use ABS, or any type of pressure control and/or left/right brake pressure split to help with your braking and maybe your differential or traction under acceleration.

Again, just brainstormin here a bit, use what you think makes sense for you and feel free to ignore the rest.
Many ways lead to Rome, and there is more then one way to build a quick race car.

Good luck & all the best

[747heavy]

Hi Delacf,

It´s not 100% related to your question, but you maybe find something useful in this article.

http://131.155.54.17/mate/pdfs/11693.pdf

[delacf]

I would still think, that a pedal shift system would be permitted ( but maybe I don´t understand the finer points of the rules correct - sorry)

I think it would be legal if you do not employ electronic.

I also understand, that the max. overhang of the front splitter is 50 mm at the front, and that it can´t be wider then the car.
I´m not sure, if I found any reference that the underside of the splitter needs to be flat, but again my Spanish is not that good.

The floor must be flat, but only in the rectangle between wheels.

Try to gather some data about corner speeds and acceleation. To me it looks like that if the corners are very tight (on therefore slow) the cars need good "power-down" and longitunal acceleration. Which may goes a bit in the direction to explain, why they run relative small camber (compare to a touring car for example).
But it can also be related to the "cross ply" tires, and I will freely admitt, that I have no expirience with this type of tire.

I thought so, the same thing, but I have no experience with any tyres .

Thanks, you helped me a lot !!! =D>

[delacf]

What I could be useful deflection vs. Load plots for different pressures and camber angles with the tire in motion? Regards, delacf

[747heavy]

sorry i`m not sure I understand what you mean.

this data would be used, among other things, to define ground clearance/ride height for cars which are strongly depending on their underbody aerodynamics, and to calculate your correct gear ratio ( as your loaded tyre radius is going to change).

[delacf]

Sorry, my english is not very good. I "speak" of this (from the seventh page):

http://www.mrtyremotorsport.co.uk/uploa ... Advice.pdf

Regards, delacf

[747heavy]

Thanks delacf,

Don´t worry your English is just fine, better than my Spanish anyway

This information gives you an idea about the vertical stiffness of your tire.
You devide the load (kg) by the deflection (mm) and multiply the result by 9.81, this gives you the vertical stiffness of the tire in N/mm, aslo called the tire spring rate.

You will see, that this value changes with camber and inflation pressure, and is maybe different for your front and rear tires.

Apart from the two reasons I have given in the last post, why you will want to know it.
You need this value to make some calculations in regards to your suspension setup (spring rate and damping).
If you use a quarter car model for your calculations, this value gives you the tire stiffness (aka tire spring rate) Kt.

See as an example the following Quarter car model


the value for Kt is what you can read from the graph in the Dunlop publication.
The vertical tire stiffness changes with speed, this is the reason, that the values given are for a defined speed (velocity).
The tire growths slightly in diameter with increasing speed, due to centrifugal forces.
You tire is a spring in series with your suspension (spring), you you need to keep this in mind when you want to calculate your ground clearance (ride height) for a given load. This is more important for cars which generate high downforce with speed ( e.g. F1, LMP etc.).
This should not be too important for your hill climb project, but keep it in mind.

[delacf]

Ok. Thank you very much [-o< .

That's what I thought. Sorry, I'm starting to study the book of Milliken & Milliken. I must learn a lot in recent months .

This should not be too important for your project hill climb, But keep it in mind.

I'm thinking about designing the suspension for a Formula Ford 1600. I think the most important thing is to learn to design from the data of the tires and I have no data about the A15 AVON tyres. For this reason I am looking for information in the Dunlop site.

Within four months I start my project. I have four months to decide

Regards

[747heavy]

that´s nothing to be ashamed about Delacf, all the best on the way.
It´s a very interesting and broad topic, and one where as more you are going to learn/know you are going to realize how little you know.
But let´s that not stop you - go and give it a try.
Nothing ventured - nothing gained.

[747heavy]

What I meaned, wnated to say, is that the effect on ground clearance/ride height due to the tire vertical stiffness is not "too important" on you hill climb car or on a Formula Ford, as you will not have the levels of downforce and ride height effects on your downforce as you have on an F1 or LMP car.
For your projects the tire spring rate is important in terms of your suspension spring rate and damping.

of more interest for you would be to know the cornering stiffness of your tire, in relation to camber, toe and slip angle.



another value of interest :


maybe you find some interesting informations here, o.k. it´s more related to roadcar tires, but the fundamental pinciples are the same, the values and specific characteristics for a racing tire can be different.

http://www.tut.fi/plastics/vert/11_tyre ... tusivu.htm
and
http://www.rqriley.com/suspensn.htm

[747heavy]

maybe you find one or the other useful article here:

http://www.docin.com/p-52390408.html

http://www.docin.com/p-52390517.html