Superkart aerodynamics

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Post Tue Jan 29, 2013 4:01 pm

Hi to everybody!

I'm a mechanical engineering student from Barcelona and as a final project of the degree I decided to design a 3D Superkart, but only the chassis and all the bodywork with Solidworks.

So, I want to ask for your help with the aerodynamics. I know more or less how to design and define all the components with solidworks with the help of Competition car aerodynamics book, some aero foil programmes to help with the NACA rear wing profile. But what I really want to know if there is any way to know the data (the amount of downforce, etc) or any kind of data in order to compare an actual superkart design from Anderson Karts http://www.anderson-csk.co.uk/maverick_div.php or MS Karts http://www.mskart.cz/new/en/catalogue/ms-superkart-vm-250-engine with my future design.

Without this information, I don't know how to prove that my design will be an improvement or at least I'll get close to the numbers obtained from an actual superkart model.

I hope that I made a clear explanation of what I want to do with my project and what information do I need.

Thanks a lot!

Sergi
Racingf1
 
Joined: 13 Apr 2012

Post Thu Jan 31, 2013 9:21 pm

May be i could help, my father as raced those superkart 250cc the last 25 years in france and europe.
He still have a Petersen chassis i think.
remydio
 
Joined: 17 Mar 2011

Post Thu Jan 31, 2013 10:03 pm

You might have some luck here http://www.ekartingnews.com/forum.php it was a pretty poplar forum in the day
"The question isn't who is going to let me; it's who is going to stop me."
flynfrog
 
Joined: 23 Mar 2006

Post Fri Feb 01, 2013 6:34 pm

Thanks to remydio and flynfrog!

Any kind of help in order to obtain the information thet I need, it's really wellcomed.

I'll try with ekartingnews website and I'll wait if remydio, you can obtain any technical data.

Thanks a lot
Racingf1
 
Joined: 13 Apr 2012

Post Sat Feb 02, 2013 12:55 pm

Should see my father in the nexr days, i'll ask if he does have any sort of solid infos about aero.
remydio
 
Joined: 17 Mar 2011

Post Sun Feb 03, 2013 8:56 pm

Here's a video of

CFD modelling of a 250cc kart

It mentions a drag of 853N and a downforce of 1160N at a speed of 55,4m/s or 199,44 km/h at the end of the video (@ 35:10min).
Of course, this is just a CFD calculation, but it's better than nothing.
"Torque * 2Pi * f" is nothing without control!
Blanchimont
 
Joined: 9 Nov 2012

Post Mon Feb 04, 2013 11:04 pm

Hi people!

I would like once again to all of you that have answered to my post!

For me I have great news because I got access to some baseline data in terms of downforce and drag generated by superkarts.

So now, I think that I have sth to compare with my own design.

Know what I need to know is about chassis dimensions, what for me is quite difficult, because for KZ and KF karts it is possible to find the homologation forms for the chassis, but for superkarts I don't know why, but it's not a public information.

So, if any of you could help me with this new issue...

One more thing, I don't know what am I doing wrong, but I can't register to ekartingnews forum...

Thanks a lot!

Sergi
Racingf1
 
Joined: 13 Apr 2012

Post Mon Feb 04, 2013 11:22 pm

Racingf1 wrote:For me I have great news because I got access to some baseline data in terms of downforce and drag generated by superkarts.i


Mind to share them with us?

Technical regulations are here in §9:
http://www.cikfia.com/fileadmin/content ... T_FULL.pdf
"Torque * 2Pi * f" is nothing without control!
Blanchimont
 
Joined: 9 Nov 2012

Post Wed Feb 27, 2013 8:54 am

Sorry for the delay. I've been quite busy and I din't have enough time to answer.

For Division 1 superkarts, the downforce values at 160 kmh (100 mph) are:
- Overall lift coefficient: -0.33
- Overall drag coefficient: 0,47

The front of the superkart tends to not produce any kind of downforce, and the key part is the rear wing.

For the rear wing itself the values are:
- Cl: -0.320

So, the expected overall downforce generated is between 320-350 N (at 100 mph).

In my case, I've found that for my model the best NACA airfoil was a NACA 9312 with an AoA of 13º.
The wing characteristics are:
- Span: 1200 mm
- Chord: 340 mm
- Air speed: 68 m/s
- SolidWorks Flow Simulation software
- Results with no endplates yet.
The results for this configuration are:
- Downforce: 1011 N
- Drag: 200 N

With and endplate (I'm still trying to define the best configuration) it increases the downforce values, but also the drag is a little bit increased.

Now, I'm not able, but I'm going to post to you some screenshots about my developments with the rear wing today.

I have a question related to the simulation results. If I have a symmetric airfoil, why do I have different flow lines in the result? The resuts should be symmetric too. As I said before, I will post during the day some screenshots to show all these things.

Once again, sorry for the delay in the answer.
Racingf1
 
Joined: 13 Apr 2012

Post Wed Feb 27, 2013 10:24 am

Racingf1 wrote:Sorry for the delay. I've been quite busy and I din't have enough time to answer.

For Division 1 superkarts, the downforce values at 160 kmh (100 mph) are:
- Overall lift coefficient: -0.33
- Overall drag coefficient: 0,47

The front of the superkart tends to not produce any kind of downforce, and the key part is the rear wing.

For the rear wing itself the values are:
- Cl: -0.320

So, the expected overall downforce generated is between 320-350 N (at 100 mph).

In my case, I've found that for my model the best NACA airfoil was a NACA 9312 with an AoA of 13º.
The wing characteristics are:
- Span: 1200 mm
- Chord: 340 mm
- Air speed: 68 m/s
- SolidWorks Flow Simulation software
- Results with no endplates yet.
The results for this configuration are:
- Downforce: 1011 N
- Drag: 200 N

With and endplate (I'm still trying to define the best configuration) it increases the downforce values, but also the drag is a little bit increased.

Now, I'm not able, but I'm going to post to you some screenshots about my developments with the rear wing today.

I have a question related to the simulation results. If I have a symmetric airfoil, why do I have different flow lines in the result? The resuts should be symmetric too. As I said before, I will post during the day some screenshots to show all these things.

Once again, sorry for the delay in the answer.

Some superkarts have more balanced aero than others. In Racecar Engineering, Simon Mcbeath once tested two superkarts
in a windtunnel. One produced a good bit more downforce than the other. The one with more downforce also had a better aero balance. The one with much less downforce, produced it all at the rear, similar to your test.
“To be able to actually make something is awfully nice”
Bruce McLaren on building his first McLaren racecars, 1970

“I've got to be careful what I say, but possibly to probably Juan would have had a bigger go”
Sir Frank Williams after the 2003 Canadian GP, where Ralf hesitated to pass brother M. Schumacher
Pierce89
 
Joined: 21 Oct 2009

Post Wed Feb 27, 2013 11:22 am

Pierce89 wrote:Some superkarts have more balanced aero than others. In Racecar Engineering, Simon Mcbeath once tested two superkarts
in a windtunnel. One produced a good bit more downforce than the other. The one with more downforce also had a better aero balance. The one with much less downforce, produced it all at the rear, similar to your test.


In fact, I got the help from Simon. So, perhaps you're talking about the same data that he provided me.
It's not too much, but for me it's quite useful because I really needed a baseline to work with.

Later on, I will post images showing at what point I'm on my simulations and what problems do I have to face. Beucause know I'm in the point to add the endplates and 2 beam wings (because the central part needs to be free). And it is quite difficult to find the optimal configuration within the dimensions that says the rules.

With all the assembly, if I achieve more downforce, but the drag it is also increased and the lift to drag ratio (L/D) is more or less the same or a bit lower than a single wing profile with endplates, the final assembly can be considered a good design?

Another point is that my rear wing configuration is in free stream air. Whereas with the "external" drag added by the driver over the airflow over the rear wing, I think that the levels that I achieved will decrease.
Racingf1
 
Joined: 13 Apr 2012

Post Wed Feb 27, 2013 3:15 pm

I'm going to show you my RW designs.

For the 1st one, is the simple version of the RW with the main plane and endplates.

The downforce generated is 1430 N and a Drag of 225 N for an air speed of 68 m/s. L/D= 6.4

The 2nd version, is the RW with the beam wing.

The downforce generated is 1642 N and a Drag of 331N for an air speed of 68 m/s. L/D=5

I have doubts with the 2nd simulation because the airflow around the main plane is not the same as for the 1st version.

So, any ideas if the simulation is right or wrong? And any ideas in order to improve the desing of the endplates?

To conclude, any can explain me how to post the screenshots that I did to show you my work? Because to post and image I see the option, but it refers to a website, and the screenshots are in my computer.

Thanks!
Racingf1
 
Joined: 13 Apr 2012

Post Wed Feb 27, 2013 5:00 pm

seems like a lot of downforce if you ask me. L/D seems about right, but everything seems like a magnitude higher than it should be.

Could anyone confirm this?
wesley123
 
Joined: 23 Feb 2008

Post Thu Feb 28, 2013 5:00 pm

~150kg of downforce at ~150mph? Doesn't seem too outrageous, but that depends on how big the wing is.
andylaurence
 
Joined: 19 Jul 2011

Post Thu Feb 28, 2013 5:06 pm

Racingf1 wrote:
To conclude, any can explain me how to post the screenshots that I did to show you my work? Because to post and image I see the option, but it refers to a website, and the screenshots are in my computer.

Thanks!

You need to upload the pics to a picture hosting service. Some of the other members can recommend some good ones.
“To be able to actually make something is awfully nice”
Bruce McLaren on building his first McLaren racecars, 1970

“I've got to be careful what I say, but possibly to probably Juan would have had a bigger go”
Sir Frank Williams after the 2003 Canadian GP, where Ralf hesitated to pass brother M. Schumacher
Pierce89
 
Joined: 21 Oct 2009

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