Formula search

[Dennyz]

I am looking for the formula to calculate the wheel HP required to move a vehicle of a certain weight at a certain speed.

All I can find is 1/4 mile ET/HP formulas.

[motoman]

You have WAY too much free time on your hands..................

[Ken Talbot]

Something like this?

[randy]

Or this?

Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. If you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower.

One mechanical horsepower also equals 745.699 watts or .746 kW (kilowatts) of electrical horsepower. This means that if you really want to confuse people, you could complain about the 0.0268 horsepower light bulb your landlord has in the hallway as opposed to the mundane 20 watt measurement.

[Dennyz]

Thanks Ken.

The students (11th & 12th grade) in my "Design Technology" class got to talking about the cost and benifit of converting a small car to electric drive. I think they will be surprised how the numbers will work out and how important weight is. And how much the take for granted the power of their gas engine.

[HobbyMan]

Way too much effort to calculate. Air density, surface area, changes in the road(elevation, direction) etc........ Columbus sailed the ocean blue in 1492 /2 = 746. that is how I rember(not really ) also, check this out
I saw a guy who built this "rocket car" about 20 years ago. It even had a sliding canopy. With a very small engine and low HP, he had very good mileage because of the aerodynamic properties. Rember the Word's Fastest Indian? Streamlining makes all the difference. A couple of months ago, there was a solar electric race at Texas Motor Speedway. They had all electic motors and they seemed to get around pretty well.
now to call
forum.soapbox(on)
{Yes Mass is very important in making an efficient car. The only problem behind the idea of making lighter more efficient cars is the saftey issue. Ultimatly, with the way cars are designed to crumble today, besides the shock obsortion properties, you are more likely to be crushed or seriously injured. I went to the DMV to register a 96 Lincoln town car with my dad the other day. The woman there was startled by the vehicles aprox 4500 lb weight. Her car only weighed about 2300lbs. In a head on collision with cars aproaching at equal speeds (opposite velocities), since the heavier car has more mass, it will accelerate less, thus saving your life. (F=MA) (odds are that it is stronger too so it will not crumble as much) The lighter car will accelerate more and will probalby crumble with you inside it. This is just one of the saftey concerns with lighter cars. Besides motorcycles, my family only drives heavy/ very well built cars. My mom's life was saved from a side collision when a woman ran her F250 head on into the fender of our 88Lincoln town car. THe officer said "If you had been in any other car, you would be dead right now" As it is, she walked away, although the frame needed to be pulled out more than 3 inches. (thats about the same frame as an F150) If we must have lighter cars, we need trains. Anything heavier than a car gets transported by train. Everything else must not be bigger than an average sized car or motorcycle)}
forum.soapbox(off)
Never overlook saftey.

[LoserShoes]

But what about when you hit a fixed imoveable object (bridge abuttment)?

Steve

[malber]

hp=[pounds-force] x [velocity (mph)] / 375

From here.

[HobbyMan]

I would rather have a strong car with good seat belts. If the car doesn't crush, the seat belts might just save your life. Air bags might work too. With a cheaper car like a unibody, you will probable get shoved through the engine. Either situation is fatal at high enough speeds. I have seen MANY of these particular crashes in my lifetime. THe newer cars just fold you up into a ball. My family used to take long RV trips every chance we got. There may be some new cars that are safer, I don't know. But IMHO the majority of the cars on the road today are not as safe as the cars from yesterday on todays roads. About the HP equation. I am not quite sure about how that equation pertains to regular automobiles. As you can see, it is set up for a train.(minimal frontal air resistance). That equation does not factor in air resistance unless that is part of the 375. That could just be some arbitrary number that works for all train engines with the surface area estimated. We are going into air drag more extensively for the second time now in AP physics. Maby I will learn some new stuff that will apply.
Hobbyman Over and Out

[LoHo]

Or:

hp=$

[trbig]

The new cars do crush... but it is designed with the crush to happen around the occupants and not to intrude into the passenger compartment. The engine and trans breaks away and goes down and back under the car, not into the compartment. It all helps to diffuse the energy and spread it out. NO CAR was designed to withstand and protect the occupants in a 65 mph head on. I worked on ambulances for several years. MANY times I would come upon a wreck involving a newer car and an older style vehicle like an old Ford or Chevy pickup. The older styles LOOK to be in better shape with the newer vehicles mangled... but the older vehicles passenegrs would be dead while the newer cars occupants would walk away after extrication. All the old steel and weight transfers all that kinetic energy to the passengers on impact. So.. yes.. the older vehicles WILL stand up better in a crash... but the occupants won't.

Tod

[HobbyMan]

Yeah, I understand the idea behing the design, but no car is safe in my book. Even some older cars have some crush zones wich work similarly, but not to the same extent. It really depend on the circumstances. Anyway, look how easily it is to hijack a thread

[John]

Originally posted by HobbyMan
Anyway, look how easily it is to hijack a thread

And to add to your post count.

[HobbyMan]

well, that too. THough, it really doesn't matter to me. (You can tell by my status)

[HobbyMan]

I saw a new nissan today. the body was perfect all around except for the roof. It had caved in soo far(past the windows) that it was obvious that it was a fatal accident. There is no way that could have happened to one of my families 96 lincoln town cars or classic chevys. Have you seen the way cars are assembled today? They sure aren't built like they used to.