Cycle speedometer

Speedy Builder, you missed the 15 off your sum. A useful factor to remember is 60 mph = 88 ft/sec, so 15mph is 22 ft/sec and revs/sec is 22*12/(4*pi) = 21.

The cycle speedometers with which I have been associated require the wheel diameter to be keyed in, but being for cycles, the range may well be limited, possibly only covering the normal sizes of cycle wheel, so 4" may be an impossibility.

The particular instrument that you have in mind needs to be investigate, to check that it can accommodate 100 mm wheels.

Howard

Dooooo ! Stand corrected, Could do better, or See me later - Thanks Duncan, so probably 21 pulses / second not very fast for a bit of electronics (perhaps).

Bob

Most bicycle electronic speedos I have used allow either the exact wheel diameter or circumference to be entered in order to generate an accurate speed reading. As it is a simple mathematical function there should be no problem if the value entered is significantly smaller than a bicycle wheel.

I lent my cycling GPS (Wahoo Elemnt) to a friend to record his lap of the local track. The information recorded was interesting, he said, but, perhaps, not that useful!

I uploaded the information to Strava. From that lap speeds, times and elevation could be seen. Also a map of the route.

It generated some interest at his club the afternoon he was using it, he phoned me to ask how to reset the device to record someone else's journey, ended up recording several other loco journeys and my friends drive from the track to my home!

Strava (other GPS apps available) can be uploaded to a phone to do exactly the same as I described for zero cost for the basic and entirely adequate version. It will give real time info, more or less, during the journey. I have noticed that these GPS devices don't quite have the transient response of the old school cycling "computers". The GPS devices are processing a lot more data I guess?