Man math help reqd. brain frozen!
Discussion
Years ago i could have done this in a flash in my head. but all the good working bits have died off
so
a Wheel is 80 inches in diameter. Circumference is 251 inches ( rounded down)
What is the rpm of it when doing 60 mph?
The best i can come up with is
60 mph is 88fps, which is (88*12) 1056 inches per sec. Divide that by 251 and it gives you just under 4.25 revs per sec
Near enough. or miles out?
so
a Wheel is 80 inches in diameter. Circumference is 251 inches ( rounded down)
What is the rpm of it when doing 60 mph?
The best i can come up with is
60 mph is 88fps, which is (88*12) 1056 inches per sec. Divide that by 251 and it gives you just under 4.25 revs per sec
Near enough. or miles out?
k that!spikeyhead said:
Give me a big hill and I'll have a go, not that I've ever ridden a penny farthing, but what could possibly go wrong?
You’re on your own mate.
https://youtu.be/BuPJoA9gIro
AdamIndy said:
Just needed to somersault his way out, preferably not via a ditch.silverfoxcc said:
Years ago i could have done this in a flash in my head. but all the good working bits have died off
so
a Wheel is 80 inches in diameter. Circumference is 251 inches ( rounded down)
What is the rpm of it when doing 60 mph?
The best i can come up with is
60 mph is 88fps, which is (88*12) 1056 inches per sec. Divide that by 251 and it gives you just under 4.25 revs per sec
Near enough. or miles out?
Let's do it in metric, and save a ton of ballache.so
a Wheel is 80 inches in diameter. Circumference is 251 inches ( rounded down)
What is the rpm of it when doing 60 mph?
The best i can come up with is
60 mph is 88fps, which is (88*12) 1056 inches per sec. Divide that by 251 and it gives you just under 4.25 revs per sec
Near enough. or miles out?
80" is 2,032mm
Multiply diameter by pi for the circumference = 6,380mm = 6.38m
60mph is 1 mile/min = 1,609m/min
1609/6.38 = 252.2rpm = 4.2 revs/sec
OK It is a wheel on a steam loco.
now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
what would the speed of the piston rod be at 60 mph?
The fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
what would the speed of the piston rod be at 60 mph?
The fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
silverfoxcc said:
OK It is a wheel on a steam loco.
now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
what would the speed of the piston rod be at 60 mph?
The fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
Piston speed would be an average as it would have dwell points at tdc and bdc but worked out as an average is regardless of if moving up or down at a given rpm of the crank.now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
what would the speed of the piston rod be at 60 mph?
The fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
silverfoxcc said:
OK It is a wheel on a steam loco.
now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
56" - because it's going there-and-back in that one revolution. 28" is the distance from TDC to BDC. In one revolution it goes TDC-BDC-TDC.now as we agree that at 60 mph the revs are 4.2 per sec take this one on (BTW i make it 15mph but it doesnt sound correct)
When cars give the piston speed at x ft per sec is that one up and one down or just one way
The stroke of the piston is 28 inches, so for one revolution it travels 56 inches so do we work on 28 inches or 56?
silverfoxcc said:
what would the speed of the piston rod be at 60 mph?
The fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
If it's travelling 56" (1,422mm) in one revolution, and is doing 4.2 revolutions per second, then it's covering 5,974mm in one second. Just under 6 m/s = 358.4 m/min = 21,560.7 m/hr = 21.5kph = 13.4mphThe fact that multiples of 60 and 30 crop up in the question and answer makes me feel a bit uneasy!
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