Posted by: drracing | April 6, 2012

Small Race Car Project – WIP

Hello everybody!

it’s already more than a month since the last time i wrote here, so i think it’s time for some updates.

The work on the small racecar i told you about in my last post is going on. I am proceeding (not as fast as i would like to but, hey, it’s not my job at the moment!) and i have completed the whole front wheel assembly, front suspension geometry and an overall layout for the front part of the chassis.
This car will have a lot if nice features that, i think, have never been seen on similar cars before (of course, some of them exist on “better” cars and, honestly, i am not reinventing the wheel). Of course, some of them have prons and cons, as usual. But i think the prons can give, in the kind of fields this car will race, some good advantages, and this is why i used them in my design. Moreover, some of the cons are connected to the weight. But since regulations demand for a minimum mass of the car, till when i am some kg less of this minimum weight, i am feeling fine. My idea is not to build up an extreme design and sometimes, believe it or not, it is more difficult than when you can do something at your best: here the biggest compromise is price and i am trying to keep always fixed in my mind this point. Again, my goal is to have a very easy and reliable car. So simplicity is another very important goal of the project.

This actually why, with the friends of mine involved in the project, we decided to use some road car derived components for some parts and existent (cheap) race components for some other things.
One of the best example is given by front wheel assembly. Here, hub is derived from a Fiat car part, as well as wheel bearing (and the driveshaft and CV joint we will use at the rear).
Brakes are taken from an italian company which mainly build tuning parts but have also some light formula cars intended components in its catalogue: they are not the best i could find, they don’t use floating technology for example (which i would have loved to have here), but they are cheap, ready and already ok for the wheel hub we are using. So for now it’s ok.

Wheels will be probably taken from OZ, with a design already existent from a company who asked them for specific dimensions. We will actually buy wheels from this company i think. Again, it’s not the best solution i could find around, they are not so lightweight and also ET is not exactly how i would like to have it, but it’s anyway a very good quality wheel and a good price/value compromise. Moreover they are ready and quite cheap and i hope the more weight they have could mean more reliability and strength/stiffness.

In the mean time, i have also done some load, durability and stress/stiffness calculations for control arms, bearings, bolts, brackets and upright also using FEA sometimes. We are not going to have an extreme design and one of the tasks is to be able to use the same bolt/tubing/bearings etc for different components, so that it’s cheaper to have spare parts and we don’t have to spend too much money when buying material. Normally to purchase higher numbers of parts means also better prices, as you probably know.

Moreover, i have found a cheap and effective (i hope) way to perform some basic Vehicle Dynamics simulation at no cost and without the need to develop anything myself for now. Bosch motorsport, since some years, is offering for free a very useful (although not perfect, of course, but as i said it is ready and it is for FREE) quasi static vehicle dynamics simulation software that anybody can download from their site.
This simulator allows to perform mainly laptime and straight line simulation, producing also nice graphs to show the main parameters values (speed, accelerations, suspension travel, tyre slip, differential…).
Of course, to develop a simulation by myself could be a lot more fun and a lot more effective, also for my own knowledge, but it would take a very long time.
Moreover, Lapsim has already a formula 3 model inside and, so, a F3 tyre model built in. Not dealing with the tyre modeling technology they are using (which is a quite nice and interesting one based on Pacejka MF but using only 4 main parameters), on our car we will use F3 tyres. And to already have a “trustable” (this should be verified, but performing some simulation with a F3 setup i saw that results were actually quite consistent) tyre model is something that can cut your times a lot!
So i am actually using it and i am very happy of that!

For now, i just performed basic simulations to look for a “ideal” weight distribution and weight distribution sensitivity and for the relative importance of Aero in a small (and slow) car like the one we are dealing with. And i actually had some nice surprises.
In a separate post i will probably talk more about this point, which is very interesting to me and also very funny to develop! Next step will be to perform some simulations to see, for example, the sensitivity in terms of lap time gap to CG height and track width.
Moreover, starting from data acquisition data, it’s pretty easy to build up tracks  models and then to modify them to incorporate, for example, banking or different grip zones.
One cons instead is the rpm limit to 10k rpm; since we will use bike engines, it could be useful to have the possibility to overcome this limitation, but this is actually a demo version of the “real” simulation package they sell, so it is not difficult to understand why this one and a lot of other parameters (like everything connected to tyre modelling, differential or a real aero map development) cannot be used. But hey, it’s free of charge!

For now, i just add some pictures about my wheel assembly as it is now. As i said, one of the main drivers is to keep the cost down. So, i know things could be cooler and better than this, but then we would probably not have the money to build them and no possibility to sell them! So they are like they are!

I will post more pictures soon!

By the way, i know the brake caliper is upside down, but i had only a left model and this is right wheel!

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Responses

  1. Great! Really great.
    I’d like to be in contact, just to see and learn something
    Manuel

    • Hi,

      thanks for your comment.

      I stopped this project since more than one year now, so I don´t think you will see any update about that.

      But if you have questions or you want to share your ideas, please feel free!

  2. hi there! could please perhaps share with us the assembly!?

    Cheers

    • Who is “us” exactly? 🙂

      I should look for the files in my archive anyway.

      What would you like to do with them exactly?


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