rustednut

This is a time distance calculator and will work air, land, or water.

A straightline course and a stopwatch and most likely a helper will be needed. Time the vehicle through the course to the 1/10 th second if possible. Now...

For a 50 foot course....divide 34.1 by the time = MPH

For a 100 foot course...divide 68.2 by the time= MPH

For a 150 foot course... divide 102.3 by the time = MPH

For a 200 foot course...divide 136.4 by the time = MPH

Naturally, the more accurate the course measurment and time measurement, the more accurate the results

ryan_t888

I wouldn't want to try to get a speed reading from calculations. I have been through a few kinematics courses through the past 5 year. There are too many variables to consider when trying to stop a stopwatch at a certain mark as an 18inch truck flies by at 70km/h. Also maximum speed must be constant through the measured distance

100ft is about 30.48metres
At 71.3km/h(44.3mph) my car will travel 30.48metres(100ft) in 1.539seconds. From experience in a classroom error in stopping at this exact time with such a small time lapse can range from .15 up to .5seconds!

If I were to miss the start time by .2seconds and the finish time by .2seconds this would be a total of .4seconds. With this error travelling 30.48metres in 1.939seconds will be at 56.59km/h(35.17mph)

35 mph is a lot different than 44 mph.
0.2 seconds in nothing when compared with the reaction time of any person.

BTW, the metric system is much easier to deal with when making kinematics calculations.

Ryan

rustednut

Well, dragracers tipically have reaction times around .08 seconds and that includes getting the car moving. You should try it, your accuracy will be quite good. If one wanted to set up a chronograph with the starting and stopping controlled by breaking a beam of light, the results would be accurate, Thats how the NHRA and IHRA(drag racing orginazitions) do it. Just a simple low cost way of estimating speed. You are so right about the metric system being easier. just my $0.02 worth.

ryan_t888

Drag racers spend a lot of time with achieving that .08second reaction time.

One other thing I forgot to mention. How can one accurately see both lines when the lines are 100 feet apart or more. There will be a huge parallax error also leading to inaccurate results.

I paid $80 CDN on a GPS system and it is accurate to the .1mph. How much would the system you are referring to cost?

Ryan

rustednut

lets see. you have enough hand eye coordination to run rc's but not enough to see 50 feet and click a stopwatch? i threw this out as i was +/- 1 mph when checking against a cops radar and others might have had similar success except for your poo pooing it. y'all have a good day, i'm done with this forum as everybody has a better bigger or whatever 'er and it all reads about the same after a few pages. i'm sorry 1 mph is not accurate enough. yore rite i'm rong. wish i'd never posted. bye

jdmkyosho

kthxbye... ... ...

ryan_t888

You need to realize this is a public forum and many different opinions are going to be expressed in here. Not once did I say it will not work. What I am saying is the odds of getting an accurate and repeatable speed measurement is like finding a cop that will verify the speed of your rc car. I highly doubt +/-1mph is true and repeatable.

Ryan

Dokioto

I would use this to tell me my speed. I just bash (wish I could race) and it seems it would give me a good idea to how fast i am going.

notele

i have been looking online for a speed calculator and have found a few. the problem i have is that my friend threw larger tires on his truck and his speedo reads higher then his real speed. the calculators i have used are sayin the opposite of that. i was hoping anyone that went from 31s to 33s can tell me the speed they are really doin compared to what the speedo reads.

1QwkSport2.5r

This is an RC Truck forum, not a full-size automotive forum. Just in case you didn’t get that when you signed up.