Re: Calculate car speed.
Posted: Mon Dec 01, 2008 11:34 pm
And thus the interest in data! Otherwise we just endlessly speculate.gpraceman wrote:I would expect
Derby Talk is a forum for Pinewood Derby, Awana Grand Prix, Kub Kar Rally, Shape N Race Derby, Space Derby, Raingutter Regatta and other similar races where a child and an adult work together to create a race vehicle and a lot of fun and memories
http://www.derbytalk.com/
And thus the interest in data! Otherwise we just endlessly speculate.gpraceman wrote:I would expect
True. But, twice the holes, twice the hardware, more structure overhead...NealOnWheels wrote:Two sensors placed a short distance apart could do the job and would be car length insensitive.
Excellent!!NealOnWheels wrote:Two sensors placed a short distance apart could do the job and would be car length insensitive.
Place such a system at the finish line and you get the finish speed.
Place such a system at a point along the track where max speed is expected and you get an approximation of the max speed. On a typical track that point may be the transition from the slope to the flat.
Or do this at both points and use the data to determine the "lossiness" of a car.
Old thread but wanted to provide input for any searchers out there. I have one of these radar guns. If your goal is to find a max speed on the track for one car on the track at a time (or the fastest car) they would work "ok" but would not likely give the resolution that is desirable to see if you are faster or slower than before. Also they have a bit high of drop out rate where it fails to pick up the speed of an object, which will cause frustration depending on intended use. This would not work for finish line measurements as the gun will only give you the max speed it measure within the radar "field". It will not allow you to pinpoint a spot on the track to measure. And for the most accurate measurement you would have to measure directly in front of the car travel path, or cut a slot in your guide rails at the bottom of your curve to measure from behind (not sure if this would work). You could still measure from the at a slight angle but to get a more accurate reading you'd have to do some trigonometry math work (cosines) to correct the reading to a more accurrate one. Most radar guns only read in whole mph anyway.gpraceman wrote:A radar gun would give you a speed of a car at a certain point. I would wonder just how accurate a toy gun would be. You'd also need one for each lane.ohiofitter wrote:What about the hot wheels radar gun..........I know there cheap and they say they work.and you tube has a guy that dismantled one and made it bigger using house hold items..( I THINK) but you'd have to search for it.
Speed at a certain point(s) doesn't tell you who wins, so I don't really think it is a useful figure. One car could be slowing down more than an other, towards the finish, but not get nosed out before it crosses the finish. Looking at only speed at the finish would give a misleading result.
Not exactly. It is twice the holes, and twice the sensors, but this is trivial because sensors are only ten cents apiece. If anyone is really serious about doing this final speed project, I will provide him absolutely free of charge a Transponder http://www.newdirections.ws/tr.htm. As long as the track is four lanes or under, the unused lane inputs go to a row of sensors two inches down hill from the finish line. Although you can do the calculations yourself from the display in Section 4 Hardware Setup, Randy should modify GPRM as an option, that automatically pairs up Lane 1 with Lane 5, subtracts, and divides by the appropriate constant to give the speed. Same with Lane 2 and 6, 3 and 7, 4 and 8. This figure could be displayed on the racing screen..... But, twice the holes, twice the hardware, more structure overhead...
I'd be hesitant to make such a change to the software, as there isn't much demand for that feature. The complexity that would be added to the software really isn't justified.John Shreffler wrote:Although you can do the calculations yourself from the display in Section 4 Hardware Setup, Randy should modify GPRM as an option, that automatically pairs up Lane 1 with Lane 5, subtracts, and divides by the appropriate constant to give the speed. Same with Lane 2 and 6, 3 and 7, 4 and 8. This figure could be displayed on the racing screen.
You really don't realize how much work that would involve, as well as the added complexity to the software. The more complex software gets, the easier it is for something to break.John Shreffler wrote:Randy: I certainly agree that such a feature would have no place in the racing. But in this thread, I got the sense that the interest was to learn about performance during car construction and fine-tuning.
If you were to put it into GPRM, it would only be available to the Transponder because of the mechanical realities. It would have a hidden "switch" sort of like the Flight Simulator capability of Google Earth. Probably only one person in a hundred knows about Ctrl-Alt-A. It would not necessarily have to produce immediate profit. If mentioned at all, it would just be another feature to tout. The mathematical part of it is trivial, about 4 lines of code, although you would need another column on the display.