MPH question????
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alvin l nunley
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nine sheets to the rescue. 41 miles per hour average.
Nine sheets is an Excel collection of about 20 different utilities.
If you have Excel, email me at anunley@austin.rr.com
gear ratios, speeds, corner weights, stagger, tire temps, day at the races and others
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Maxxx T - you don't need an Excel program to figure your MPH, just a calculator.
Miles Per Hour is the same as V=distance divided by time (V=D/T)
Distance = 1/5 mile or .2 mile
time = 17.56 seconds or .00487 hours (3600 seconds in an hour, 17.56 divided by 3600 = .00487)
V = MPH or miles divided by hours (miles/hour)
V = .2 miles divided by .00487 hours
V = 41.067 Miles Per Hour
Plug any track length in and the lap times and you can figure MPH
Miles Per Hour is the same as V=distance divided by time (V=D/T)
Distance = 1/5 mile or .2 mile
time = 17.56 seconds or .00487 hours (3600 seconds in an hour, 17.56 divided by 3600 = .00487)
V = MPH or miles divided by hours (miles/hour)
V = .2 miles divided by .00487 hours
V = 41.067 Miles Per Hour
Plug any track length in and the lap times and you can figure MPH
I don't know what kind of track you are on, but I just want to throw this out there. I have yet to race on a dirt oval that was called "1/5th mile" that was exactly 1/5th of a mile. Distance measuring wheels can be bought or borrowed and used easily to measure feet. On dirt this is best done at the end of the night to measure the line the karts take (the groove).
1/6 mile = 880 feet
1/5 mile = 1,056 feet
1/4 mile = 1,320 feet
1/6 mile = 880 feet
1/5 mile = 1,056 feet
1/4 mile = 1,320 feet
alvin l nunley
Site Supporter
and the difference in your miles per hour and my miles per hour is because of a rounding error. Your formula should read; v = .2 miles divided by .00487777. This gives you 41.002 a minor difference for sure, and not worth worrying about.
It surprised me when your formula gave a different number than mine. Your formula seemed to be correct, and it was, other than the rounding error.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
is
alvin l nunley
Site Supporter
In reality, MPH is totally irrrealevant...ET (elapsed time) always 'Wins'
racing promotor
Moderator
I would think track was bigger than a fifth mile 17 and a half sec on a fifth would be very slow.
VERY true Al....But, let's face it....EVERYBODY Lies! LOLIn reality, MPH is totally irrrealevant...ET (elapsed time) always 'Wins'!
to a karter, this is correct, but how many times have you been talking to your friends, (non-karters) and the first thing they ask is, "how fast do they go". What do you tell them? Tell them your lap time, in seconds, and they'll just stand there with a blank look on their face.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
To satisfy the curiosity of non karters, we always used this method and the max RPM for a typical track session. As for conventions, we always used the right rear tire circumference. If you want to make it real easy (this equation has the units conversion from feet per second to mph built in), assume a RR circumference of 34.5 inches and divide engine rpm by gear ratio, then multiply that answer by 0.032671. 0.032671 is G, the Garbage constant, which contains all the conversion factors. If you wish to use this equation for your actual RR circumference, G=tire circumference divided by12 x 60 and that answer divided by 5280.
Al's comments about track length are spot on; since the main track we race at uses an AMB system, they have elected to include the average speed of each kart in the printout, and it's hoot. Somebody decided when the track's shape was altered slightly that it was now 1/5 mile - well that's not even close, even if you measured the track right up against the outside barriers. As a result, my young friend is told his Jr Sportsman II is going 63 mph. In actuality, using RR tire circumference and max engine rpm, it runs between 44 and 46 mph MAX speed, depending on track conditions. Computers are GI-GO devices: Garbage In-Garbage Out; until someone changes the track length in the computer program, the speed printout is going to stay garbage. Give it accurate info and be rewarded with the right answer, which makes things really simple with things like Al's spreadsheets - just feed them accurate info and you're home free; do otherwise and you're not using them to any advantage.
Most karts I've seen run between 35mph (on the smallest tracks) up to about 70 for an animal on a very large, reasonably high bite track. There are many different ways to calculate and measure speed but because of inaccuracies in track length (they're nearly always advertised as bigger than they are) and tire slip (creating inflated MPH numbers from speed sensors), the best way to get accurate speeds is with a gps.
Todd
www.dynamicsofspeed.com
Todd
www.dynamicsofspeed.com
Our track is a 1/5 mile asphalt, a good fast lap for an unrestricted animal is 12.7-12.9 seconds.
http://kart-smart.software.informer.com/2.1/
you can download this for free, plug in your numbers and it will tell you your max wheel speed, if that's what your after.
you can download this for free, plug in your numbers and it will tell you your max wheel speed, if that's what your after.
XXX#40
2A supporter
racing promotor
Moderator
Selinsgrove 1/5th mile dirt, Track record 11.4 with a 340 lb Animal
I agree, I race on a 1/5 mile clay oval every weekend, lap times are anywhere from 11.4 on a good night to 12.2-12.5 on a bad night, running akra clones. My fastest lap there is 11.32, that was with everything perfect and dialed in, just flat out hooked up. 17+ secs sounds pretty slow
you can also figure your mph based off your rpm, gear ratio, and tire diameter if you want. it will be close, I'm sure they are discrepancies like wheel spin etc. some tracks make it out to be faster because they are measuring the outside of the track and your time is in the groove which is less distance. on e how .com it said to take your gear ratio, say a 15/65='s 4.333.
take your rpm lets say 6800, and your rr tire circumference, for example 34.25. you take your tire size and divide it by pi to equal 10.907 diameter.
your math would be 6800x10.907=74167.60. then take your gear ratio x a constant(336) 4.333x336=1455.89. then divide 74160.60 by 1455.89 and you get 50.94 mph. sounds about right? a lot of work though.
take your rpm lets say 6800, and your rr tire circumference, for example 34.25. you take your tire size and divide it by pi to equal 10.907 diameter.
your math would be 6800x10.907=74167.60. then take your gear ratio x a constant(336) 4.333x336=1455.89. then divide 74160.60 by 1455.89 and you get 50.94 mph. sounds about right? a lot of work though.
i was told one time by kenny shrader (i met him back when he was driving the bud car, got invited to the race hauler thru a mutal friend) that miles per hour were for the fans to ogle at...they never really talked about MPH in the garage...it was more lap times and rpm. also, a race track insurance agent that came to inspect the track i was flagging at said that for track measurements, they come 10 feet up from the bottom of the track and measure there as this was where the groove was usually located...they measured to try and make the track a circle (which is what we do anyway!) and that was what they based thier insurance calculation on...
just passing on what i was told....
just passing on what i was told....