Distance measurement? No problem, right?
I've got a fun little project where I'm to measure the distance traveled by a non-powered vehicle.
Remember the Pinewood Derby in Cub Scouts? It's sorta/kinda like that but with a person sized vehicle... Travel down a ramp, see how far it goes. No problem.
When I told the client I could do it, I specifically said I'm not equipped or an expert to measure the speed. They said, they'll take of that by using radar gun of the local law enforcement.
Now I have a voice message saying, in effect, "turns out, we can't use radar for an 'official' speed. Do you have equipment or source to measure speed? Something like used in track & field or go carts?"
Tried google for answers but not really anything easy.
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Any suggestions?
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Get a stopwatch. Cheap.?ÿ D=RxT.
You can average the speed over the entire length or confine your timing to, say, the last 50 feet for the top speed.
In drag racing, the trap speed is the average speed over the last 66 feet of the quarter mile race. Electronic timer starts and stops; speed ft/sec = 66 ft/measured seconds. Everyone is measured over the same distance, so speeds are comparable. The measured speed is an average speed over a very short distance and approximates the instantaneous speed at the end of the race.
Radar guns measure nearly instantaneous speed that is dependent on precisely where the vehicle is when the gun is activated. Perhaps there's a way to trip the gun automatically, but that's only the first part of the problem.
The drag racer is still accelerating over the last 60 feet while the gravity powered vehicle will be slowing down after reachng some maximum speed. Assuming that all such vehicles reach max speed at the same point on the track and finding that point would be a key to success.
A totally uneducated thought is that smart phones have accelerometers. If there's an app that graphs acceleration, then that speed sweet spot may be findable fairly easily. Otherwise, it should be near the end of the steepest part of the track unless there are ups and downs from start to finish.
Maybe a topo at close intervals?
You know how long the track is, right??ÿ Get a clock and there you go.?ÿ ?????ÿ
If you are trying to find the top speed (measured over a small distance) rather than the average over a large distance, then stopwatches will probably bee too sensitive to variations in the human response time.?ÿ Maybe have 3 people with stopwatches and record the middle time of the 3??ÿ
To do it right, you need a photocell-controlled timer but that's probably not readily available or they wouldn't be asking.
Bushnell makes a battery operated hand-held speed "radar" gun for about $100.?ÿ It's like what they measure the speed of a pitched baseball with.
I think that I'm seeing a good deed about to be punished!
thanks, for all replies... Top speed is what they're looking for.
Reading the replies I realize the top speed should be at the moment it comes off the ramp. Apparently they found a device they may attempt to use for speed.
I measured the grade of the "track" yesterday. Unfortunately, at 1.5%, it exceeds the grade allowed for the record they want to go for.
Event is next week... one minor celebrity and one very well known person involved. Should be fun.
Covid restrictions so no crowds allowed - I'm not supposed to tell anyone... I'll see about posting a picture and details afterwards.
In drag racing, the trap speed is the average speed over the last 66 feet of the quarter mile race.
The chain abides!
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@jim-frame 3/10ths of a furlong... or 11 social distance lengths.
There's an app that works on your cell phone. Slalom skiers use it for making sure the speed is consistent through out the course. Cost $0.
HOW it gets measured will be a big issue, if they are looking for a record. If it is just for bragging rights, an on board phone with GPS turned on will probably give you good enough results.
There are probably associated rules. If the grade off, then it might not matter. 1.5% is pretty flat.
Search for "chronoscope", or "chronograph". These are devices for measuring muzzle velocity of firearms and speed of thrown pitches, etc.?ÿ?ÿ
A bit off topic but as the County Surveyor I was recruited to "judge" a 50 balloon stampede competition as "official measurer" back in the mid seventies.?ÿ Luckily the "Balloon Racing Rules" were very specific and I could understand the scope and deliverables perfectly, and the price was right, gratis for three days using County equipment ????.?ÿ My pay was an official Field Marshall badge which allowed me all access to the festivities including the launch site, pre and post race festivities involving meals and parties restricted to the "blooners" & potentates like me.?ÿ I was well treated.
Back then dropping flour bags to score on targets wasn't a thing; where you landed counted (since banned because now balloons can be piloted to land with in a few feet of each other).?ÿ Back then there were three main competitions, the take off anywhere from a few miles away and land closest to the target, easy-peasy solution with a cloth tape or EDM.?ÿ Second was the Hare and Hounds Race, where the top guy took off early and the goal was to land as close as possible to where he did.?ÿ That involved 10-15 miles of high speed driving to keep the Hare in view & County radio comms.?ÿ And the Hare was tricky, he'd drop below ridges and maybe land or go full on heat and dump his competitors.?ÿ Then there was the common launch site cross country maximum distance race (limited to two bottles of propane & other restrictions).?ÿ That was a bugger.?ÿ Balloons landing?ÿ in agricultural fields miles apart but radially from the launch point very close.?ÿ No GPS so I went to each basket skid site, scaled from topo maps and determined all were losers except the top two who were scaled on topo maps as tied. The Grand Marshall told me to make a decision or he would by flipping a coin which be acrimonious.?ÿ So I declared Kraken the winner by less than a pencil width.?ÿ Reminds me of target shooting competitions.
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Pinewood derby tracks typically have a ramped start section and a generally flat runout section. Cars have a maximum allowable weight. Top speed would be in the last foot before the ramp levels out typically a vertical curve. Final speed would be much slower.
Paul in PA
Well... for this silly little project we established 2 new Guinness World Records... speed and distance traveled.
Previous record distance ~210 ft.
New record distance: 349.8 feet.
(I think previous speed was around 9mph, new record is around 17mph but I wasn't paying as much attention to that.)
Instructions: "Please refrain from posting event details on social media until formal press release in January 2021." Grr...
Distance measuring was easy... verify my credentials as a measure-er was PIA...
Did a screen shot of department of licensing website showing status of current license and texted to guinness person. Filled out forms, which among other things ask for equipment used (Trimble S7.) And then they requested video of the actual measurement.
I had purposely tried to avoid the film crew when measuring so they had to find someone in the crowd that had phone video, finally found someone who had videoed it.
(I had planned to shoot distance reflectorless but the front of the vehicle went past where I was set up so I had to use a prism - good thing because there would have been no video proof.)
Fun day.
How was the speed measurement done?
