Vehicles and Chases

[MurfinMS]

Hi gang,

Looking over the vehicle and chase rules, I've got to wonder if there's any sort of logic to the whole thing. The vehicles have both a Rated Speed and MOV.

TBYB (The Big Yellow Book) says MOV is "The maximum speed of the vehicle in a combat round, expressed in its MOV rating. MOV has a sliding value of 1-5 meters; this assumes a median value of 3.", and that Rated Speed is "The maximum speed of the vehicle, an abstract value used in the chase system..."

Okay, I can live with that, but what do these speeds represent in the real world? Or do they? Maybe in just missing it, but I'd like to know on what these values are based. MP/H or KM/H either times something or divided by something, possibly...

Anyone have any idea?

Help!

-Ken-

_____________________________________________________

"We are going to eat like budget-minded Kings...

Diet Chicken Bars, Compostina, Scrunch!"

[Andy French---Mission Hill]

[Atgxtg]

I have been working on a system for writing of vehicles since, well, before BRP Zero, and I think I can help a little.

MOV & Real World Speed: According to the Movement Table (page 181), vehicle's kph rate is their combat rate*3/10

so KPH=3/10*m/round. Now, as you already know, the Combat Move rate is 1-5 times the vehicles MOV rate, typical 3 times the MOV.

So kph= MOV*3+3/10 or kph=9/10 MOV

So:

Kph= 0.9*MOV

Mph=0.56*MOV

MOV=kph/0.9 (or approximately, kph*1.11)

MOV=mph/.56 (or mph*1.79)

MOV vs Rated Speed: Rated Speed is used in chases along with acceleration. Since a car can typically move several hundred meters per round, and a chase can take several rounds, vehicles can easily travel more than a kilometer during a chase, making it hard to handle on a battleboard. What they do is use the Rated Speeds to determine the relative speeds of the vehicles. the ACC rating determines how much the vehicles can change speed during each round of a chase.

I haven't been able to nail down the Rated Speed and ACC formulas, although rated speed is almost a square root of the KPH, or maybe KPH/10 (at up to about 100kph, I can check my notes). I've got a formula that works for most vehicles ACC, although it doesn't quite hold up for the Vintage Car.

I hope that helps.

If you have any more questions, I'll see what I can do. I've got stats for several hundred vehicles done up, so I've got a good general idea of how to write up a vehicle. I got some guidelines for writing up real world vehicles in BRP, but I haven't posted an updated version in awhile. I've got a Vehicle Design System in the works, although aircraft are being difficult.

[rleduc]

In general I think the mechanics are there to handle two separate events that occur in play – first a vehicle can come zooming through a ground combat, hence the MOV states, and second there may be a classic “chase”. Unless the setting is focused on some element of the vehicles I don’t worry too much about it. On the other hand, for post apocalyptic car chases in Rubble and Ruin I defined 1 MOV = 10 MPH (which is a useful scale for American automobiles), and I extended the chase rules to have a few extra spaces (in effect, it was slightly more complex, but that is the general idea). My goal was to take the core chase runs and add a little crunch that would marry into the car construction rules.

[Atgxtg]

for post apocalyptic car chases in Rubble and Ruin I defined 1 MOV = 10 MPH (which is a useful scale for American automobiles)

That would give the standard sedan in BRP (MOV 134) a top speed of 1340 mph!

MOV/2 is a better approximation.

[seneschal]

That would give the standard sedan in BRP (MOV 134) a top speed of 1340 mph!

MOV/2 is a better approximation.

Um, you mean your American-made sedan can't do 1300 mph? Sigh. It's all a matter of proper maintenance and the right gasoline brand.

[rleduc]

That will teach me to not have files open when I write something: Speed 1 = 10 MPH.

[Atgxtg]

Um, you mean your American-made sedan can't do 1300 mph?

I don't know, the speedometer stops at 120 mph

Sigh. It's all a matter of proper maintenance and the right gasoline brand.

I'll try a bigger rubber band next time.

That will teach me to not have files open when I write something: Speed 1 = 10 MPH.

Ah! . That's about right for cars. Aircraft, and Spacecraft are where I can't figure out the relationship. I've thought of asking Jason just what formula he used for Rated Speed, but I'm afraid he'd tell me that he didn't use any, and just made up stuff that looked good to him at the time.

Here is what I've been able to extrapolate about Rated Speed from the stats given for vehicles. Entries in Red are those that my estimated values, extrapolated from the other data points.

Move Rated Speed

5 1

10 2

15 3

42 4

55 5

67 6

75 7

83 8

92 9

100 10

117 11

134 12

166 13

183 14

200 15

267 16

334 17

350 18

366 19

400 20

467 21

534 22

584 23

Edited May 27, 2010 by Atgxtg

[rleduc]

I wasn’t sure how to add an image to a thread, so I put it on my blog here.

My take is, if you ignore the first three data points you are looking at the log of Move giving the rated speed.

[Atgxtg]

I wasn’t sure how to add an image to a thread, so I put it on my blog here.

My take is, if you ignore the first three data points you are looking at the log of Move giving the rated speed.

I'm not seeing it.

Exmaple: Move 350, Rated Speed 18.

Log(350)= 2.64 , ln(350) 5.86

Is there some other step?

[rleduc]

As I drew it there, the relationship is from Rated Speed to Log Move. The idea was simple to show the linear relationship between these two variables.

A sample calculation:

Move 350 gives log(350) = 2.5441

Speed = 18.

Y = 0.0593(18) + 1.4363 = 2.5037 which is approximately 2.5441 (within about 2% of the “true” value).

That shows Speed to move – except you still have to take 10^Y to get the actual move value from a relative speed. But again, I was more interested in demonstrating the linear relationship between the log Move and relative speed.

Hope this is clearer then mud.

[Atgxtg]

Okay, so you are saying that:

Rated Speed = (log(Mov)-1.4363)/0.0593

I'll have to plug that in the spreadshseet and see if it hold up for rockets and other vehicles. Thanks!

BTW, If it does hold, then I suspect it could be simplified some. The benchmarks we have are sample values, and rounded off.

[Atgxtg]

Okay, I tested the log relationship and it doesn't hold up beyond Move 600 or so.

The values for aircraft and spacecraft get father and farther off.

I've tried sqaure root and 0.3 power equations, among others, and still can't fit the curve.

[rleduc]

That’s unfortunate. What does the data look like further out?

[Atgxtg]

That’s unfortunate. What does the data look like further out?

Confusing.

Aircraft:

Jet Move 1084, Rated Speed 30

Jet Fighter MOve 1334, Rated Speed 33)

Spacecraft:

Rocket Move 33K, Rated Speed 70

Cargo Ship Move 42K, Rated Speed 90

Transport Move 50K, Rated Speed 92

Starfighter Move 65K, Rated Speed 100

It looks like the formal started was close to a sqaure root function, but with a decreasing exponent.

The relationship holds for most vehicles. Once strage gap is the jump between the rocket and the cargo ship. A measly 9K increase in speed is worth +20 to rated, while going for 42K to 50K is only worth another 2!

If the Cargo ship and Transport stats were typos and were 82 and 90 instead of 90 and 92,the decreasing exponent would hold up fairly well.

Edited May 28, 2010 by Atgxtg