[Guillermo]

In order to avoid a tire thread from going off-topic I have started this new topic.

Tramlining the definition (thank you Tire Rack)

The term "tramlining" is being used to describe when directional control is disrupted by the vehicle's tendency to follow the longitudinal ruts and/or grooves in the road. It's name could be compared to the tram or trolley driver who does not steer because his vehicle follows the path established by the tracks.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=47&currentpage=47

All the options available to reduce tramlining affect mileage except for maybe the last one on this list

* Using lower tire pressures reduces tramlining (increase fuel consumption)
* Wider tires can reduce tramlining with the Insight (increases fuel consumtion)
* Adding spacers to the rear rims to bring them out further should help (but it brings more of the rear tires into high speed airflow therefore fuel consumption will probably increase slightly)
* Changing the front wheel alignment so it has "Toe in" like most cars do, will reduce tramlining (but increase tire wear and fuel consumption slightly)
* Adding vortex generators at the leading edge of the front undertray.
http://64.233.167.104/search?q=cach...t+4&hl=en&gl=ca&ct=clnk&cd=1&client=firefox-a

 

[boogetyboogety]

I can't imagine how five little stick-on gadgets on the hatch can prevent any kind of "tramlining" on our cars.... :?

 

[Guillermo]

I can't imagine how five little stick-on gadgets on the hatch can prevent any kind of "tramlining" on our cars.... :?

Because you looked at the wrong section of that article, look further down....

 

[Dougie]

That is a good article. I drove around with yarn tufts on my car for quite a while, but didn't think of the idea of vortex generators on the underside.

But I'm curious about the claim that the Insight is not a stable (aerodynamic) design. In most cases the fastback design is better than the conventional three-box design because there's more side area towards the rear. I have always thought that the reason that the car moves around in truck wakes is just because it's so light...

The book to read on this topic is "The Leading Edge" by Goro Tamai. It's mostly about solar racing cars, but is an excellent introduction to the aerodynamics that apply to the Insight.

Incidently, there's a chart in this book that tends to disagree with the idea that raising the car by an inch or so will increase the drag...

 

[Dougie]

Incidently, if you use the "ridge riding" method of lane position, with right wheels on the line and left wheels on the hump, tramlining will be the least of your problems. Just keeping on the pavement is hard enough! :lol:

 

[Insightful Trekker]

Wellll Dougie...

Then you open up another unfavorable condition, preferential skidding. Tires don't have the same adhesion on the painted lines. And its much worse when wet.

Watch that white road edge line :!:

HTH!

 

[ghillie]

In Melbourne we really do have trams - lots of them and it is an issue. That's one reason I'm looking at using wider than OEM tyres

 

[boogetyboogety]

boogetyboogety wrote:
I can't imagine how five little stick-on gadgets on the hatch can prevent any kind of "tramlining" on our cars....

[mod edit (Insightful Trekker): Corrected mis attributed quote]

Guillermo replied:
Because you looked at the wrong section of that article, look further down....

Yes, I read the entire article, I just have a hard time understanding how simple airflow at normal speeds would have enough force to counteract the much larger dynamic forces resulting from tramlining... I do understand drag coefficients and management of airflow around moving bodies and downforce (to the extent that I can hold my own in a party conversation, not as a world-class expert), and I can imagine the kinds of force that would force an 1,800+ lb. vehicle to be physically moved around due to whatever reason (such as tramlining). I just cannot fathom how the two can ever balance out, real world, at less than warp speeds... :?

I value your informed opinion(s)...

 

[joecvt]

If someone is interested in trying them, they can be ordered online here:
http://www.buyairtab.com

$2.50 each (not sure how much for shipping)


JoeCVT - Just your average CVT owner

 

[Guillermo]

Ok to be fair the vortex generators actually don't help much with tramlining caused by rutts on the road but i'll explain how it helps with crosswinds such as those generated by trucks driving by at highways speed.
Underneath the bottom front bumper there are several black plastic covers and an aluminum cover to help smooth the air flow under the car. But the area under the engine compartment is not as smooth for air flow as it could be. So the high speed air hits irregular objects and cause high pressure areas. These high air pressure areas lift the front of the car slightly reducing the load of the car on the front tires, so the steering gets lighter and more susceptible to cross winds.

Read this article to understand his phenomenon:
http://autospeed.drive.com.au/cms/A_2035/article.html

 

[Guillermo]

Incidently, there's a chart in this book that tends to disagree with the idea that raising the car by an inch or so will increase the drag...

It completely depends on how aerodynamic the under surface of the car is.
The Insight is better then many cars but if you look underneath it's not very smooth at all. So raising the Insight will increase the air that goes underneath and hits all those bumpy parts. A solar race car is completely smooth and aerodynamic underneath so raising it increases the distance between the road surface and the body surface therefore reducing it's drag.

I should have known this topic was going to turn all aero on us.

 

[Guillermo]

I got side tracked so I didn't reply completely before

The vortex generators disturb the laminar air and turn it into turbulent air which in itself slightly increases drag but the turbulent air is able to change direction more easily therefore less drag is produced under the car and less high pressure areas develop under the engine compartment area. This Mitsubishi technical report explains how vortex generators work. http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf

 

[Dougie]

I think there are already turbulators on the underside of the car. Those little bumps on the aluminum sheet under the front of the engine sure look suspicious...

 

[Lee]

Hey Guillermo, that web site is a gold mine of information. I backed off the end of the URL and found they have several years of ‘technical papers’ that show hybrid car development, electric cars, rally car prep etc. Also some articles on Li Ion batteries and 3-D part tolerance (OK so most of you are not so interested in the day to day engineering stuff). Cool site but I am very surprised that Mitsubishi would show so much of there hand to the public. The index is here:

http://www.mitsubishi-motors.com/corpor ... /review/e/

By the way, the effect from wind (cross winds) are called buffeting, trammeling is the effect from the road.