Calculate gearing changes based on windspeed?

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Discussion Overview

The discussion revolves around calculating gearing changes in a race car based on known tail or head wind speeds. Participants explore the implications of wind on gear ratios, particularly in a four-speed transmission with a fixed engine output.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant seeks equations for adjusting gear ratios in response to wind speed, specifically for a race car context.
  • Another participant asks for clarification on whether the discussion pertains to changing actual gear ratios or shift points.
  • A participant specifies that the focus is on changing the final gear ratio to compensate for a head wind affecting top speed.
  • One contributor suggests that the potential top speed reduction due to head wind could be estimated by considering the percentage difference in speed, advising caution in changing final drive ratios due to potential impacts on performance in other track sections.
  • A later reply clarifies that the discussion is about adjusting the fourth gear ratio rather than the final drive ratio, indicating a misunderstanding in the previous comment.

Areas of Agreement / Disagreement

Participants express differing views on the implications of changing gear ratios in response to wind conditions, with some cautioning against adjustments that could negatively affect performance in other areas of the track. The discussion remains unresolved regarding the best approach to take.

Contextual Notes

Limitations include the dependence on specific track conditions and the variability of wind, which may affect the reliability of any calculations or adjustments proposed.

Kometes
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Hi All,

I'm looking for a set of equations to allow me to calculate gearing changes based on a known tail/head wind speed, anyone got any starting points? 4 speed transmission and a fixed engine output.

Cheers,
 
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In what context? Road car, racing, etc? The changing of actual ratios in the box or shift points?
 
Race car and changing the actual ratios. For example, car has w,x,y,z gear ratios in so that the engine is hitting the limiter at the end of a straight, if it then gets a 5km/h head wind I'd like to be able to work out how many teeth I'd need to go down on the final gear (z).
 
Since you're mainly fighting aero drag but hopefully still accelerating (depending on the class and track), your potential top speed will be down by about the same amount as the head wind. Knock off half the percentage difference (200 km/h vs 195 km/h for example) and start with that.

Personally, I'd be careful about changing final drive ratios to compensate for somewhat unreliable wind conditions at the risk of messing up corner exit performance at other places on the track. Unless you have extremely long straights, you might end up being slower.
 
Thanks for the reply Mender. It'd mainly be for top gear and there's few corners where you're maxed out in top gear so it should be fine.
 
Sounds like you're talking about changing the ratio of fourth gear and not the final drive ratio (diff), right? If so, ignore my comment!
 

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