Don Terrill’s Speed-Talk

When listening to aerodynamic discussions you here the term side force.What produces side force and how does it effect the handling of a car.We have a short track car that when it runs the best lap times it is loose on entry.Because of liberal body rules I can flatten the right side of the body and add more area.Will this tighten the car on entry?

Are you sure about the term you've heard? Down force is a term that enters almost every automotive aero conversation. Its purpose is of course to add load to the tires, allowing them to generate more 'side force' and thus higher cornering speed.

It's not usually possible to directly create much side force (the giant end plates on winged Sprint cars excepted) but If rules permit, wings, spoilers, splitters, underbody contours and other down force-generating devices can be very effective.

I’ve been watching you tube video from kyle engineers it has been very informative.i added the flat right side and it did make some difference.IT was still line sensative but it seemed easier to run a good lap.Won heat and started on pole,was leading when the race was stopped for rain.RAined out this week also ,now I have to 2 weeks without touching anything lol’

I would think in this context "side Force" would describe the result of a vehicle in a yaw condition relative to its direction of travel, very common in say dirt track, The result being likely an increase in drag as to a higher drag coefficient from the side profile of a car, and some accompanying loss of DF as the airflow over any wings, etc is no longer optimized. However with a large enough end plate on the downwind side of a wing, it might convert to a typical spoiler effect, and recover some lost DF, but now at a higher drag, or even subtle additional useful braking effect

I'm just guessing as to what was meant by the term "side force" was used in whatever the context was.

Kevin Johnson wrote: ↑Sun Oct 14, 2018 4:09 pm

https://en.wikipedia.org/wiki/Cornering_force wrote:Cornering force or side force is the lateral (i.e., parallel to the road surface) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length.

I don't dispute the above, but that has little to do with OP's question about side force when discussing aero forces, correct?
I admit increased DF increases the "side force" possible as described above, but in reality, any DF increases all tire grip related forces, seems odd they would single out side force.

Am I beating a dead horse?

I know that Google adapts to your history and I have done many, many thousands of searches related to engineering and physics. The article that I quoted was the very first hit for the search parameter 'side force' with an expanded citation from Wikipedia.

A long time ago David Redszus suggested that I obtain the collected series of articles by Taborek from Machine Design in 1957. I found an original reprint but a link is provided below. Taborek defines it on page 7.

http://www.edccorp.com/library/TechRefPdfs/EDC-1110.pdf

Unfortunately the pdf is an older non-searchable format so you actually have to read it.

After researching the best explanation I found ,that it is a stabilizing force much like a weather vane.Much like the center of gravity you also have a center of pressure from aero forces.THis force should be to the rear of the CG to help the drivability

In the context of aero, I agree with your findings. My earlier comment in this area, was once I believe observed at a Daytona road course HPDE with a members car with recently added rear DF mods. In a flat infield turn at about 130, the the rear drifted out, the driver timely counter steered, but the rear just kept coming around. The rear wing did not have larger then expected wing end plates.

Speaking with the driver shortly after the shunt to hear his story, he later in the day gave 2 more different explanations of the shunt. I had it all on camera. My later research led me to believe the rear wing in yaw lost a large portion of DF, as the end plates now disrupted clean air flow, additionally effectively shortening the chord of the wing to airflow, the end plates never added much side force behind the COG to help straighten the car, and the driver was never going to save it. But that is just my guess.

Those Tatras did take out a lot of officers during the war and the side force from the fin sadly did little to help.

Reading a book on aero the author stated that high downforce car are for professional drivers not amateurs.I was surprised at this statement but if you take in account that a car would lose DF in yaw very quickly it is understandable.We did a yarn test once and stood at the apex of the turn less than 10 feet from the car.The main thing that I took from the test was how much the direction of the air changed in the corner.

Aero side force is a real thing and is commonly measured in a wind tunnel test. Most left turning race cars are not symmetrically built and can have significant aero force on the right side of the car. And if the engineer knows his stuff, he can get sideforce and a lot of rear downforce. When I was doing work on stock cars back in the early 2000's, we had cars that looked like a banana from above with the rearend noticeably skewed to the right. And they fit the templates of the day. The most benefit from this was exposing more spoiler to the wind for downforce. A side effect was right side aero force which also helped hold the car in the corners.

Have you seen CJ Rayburns old speed record late model? It had a large air dam on one side for this very reason, also winged sprint cars get a a lot of help from the sideboards on their wings.