# Concerning the new power to wheel to weight ratio calculation

**URL:** <https://discourse.cataclysmdda.org/t/concerning-the-new-power-to-wheel-to-weight-ratio-calculation/17854>\
**Category:** The Garage\
**Created:** [December 11, 2018, 1:42pm UTC](https://discourse.cataclysmdda.org/t/concerning-the-new-power-to-wheel-to-weight-ratio-calculation/17854 "2018-12-11T13:42:57Z")\
**Posts on this page:** 1\
**Showing post:** 19

<div class="post-metadata">

**Author:** ![DrakeDragon8](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@DrakeDragon8](https://discourse.cataclysmdda.org/u/DrakeDragon8)\
**Post date:** [December 12, 2018, 2:20am UTC](https://discourse.cataclysmdda.org/t/concerning-the-new-power-to-wheel-to-weight-ratio-calculation/17854/19 "2018-12-12T02:20:58Z")

</div>

> [@Latest Experimental build, what's new?](https://discourse.cataclysmdda.org/t/latest-experimental-build-whats-new/17835/38):
>
> base co-efficient of air drag (CoD) is calculated by going down each column of the vehicle and taking the highest value. each column starts at 0.25, +0.1 for having rams, +0.2 for not having half-boards in front of full-boards, +0.3 for not having windshields in front of seats, +0.3 for not having roofs over seats, +0.3 for having turrets, -0.1 for being twice as long as the vehicle is wide. So basically, the aerodynamics of a tank are terrible and you’re looking at a base CoD around 1.0.
> 
> Effective CoD is multiplied by an approximation of the vehicle width in meters and an approximation of the vehicle height - 1.4m for motorcycles, +0.6 for having aisles, +0.5 for having fullboards, +0.1 for having roofs, so your tank is probably about 3m wide and 2.5m tall and you’ve got an effective CoD of 7.5. Compare that to a sports car, which has a base CoD of 0.25 or so, a width of ~2m, and a height of 1.5m, for an effective CoD around 0.75.
> 
> Air drag is proportional to the square of velocity times effective CoD, which is one of the reasons a sports car can reach 175mph with a single V12 and 3 v8s get a light tank to 51 mph. The other reasons include the tank massing 20x as much as the sports car and having at least 20x the rolling resistance.

I believe this is the cause

---

_[View the full topic](https://discourse.cataclysmdda.org/t/concerning-the-new-power-to-wheel-to-weight-ratio-calculation/17854)._