speedo'n' mileage meter

[spamcanman]

I have seen some loco drivers fit bicycle type speedos/mileage clocks on there locos I would also like to try one but I have been to Halfords and the smallest diameter wheel they sell for is 18" so what and where should I be looking to purchase one also I notice some are wire free could these lead to problems or should I go for hard wired

[alanstepney]

The bicycle ones use a single pin on a spoke, to "flip" round a star wheel that has 5 (I think) legs.
Thus the star wheel turns once for each 5 turns of the road wheel.
From that point it is just a matter of maths to work out what each rotation equals in distance, and from that, and the diameter of the loco /driving truck, wheels one can calculate how many pins one would need.
Or gear it accordingly.

[peterseager]

Alan

Thats how they worked when we first got bikes. Nowadays they use a computer. There is a magnet on the wheel and a reed switch fixed to the frame and connected to the computer unit.

I have one fitted and it works fine but as noted you need one that can be set for small wheels. Unfortunately mine is now discontinued and the replacement is no good for our purposes. A friend did buy a suitable one from a cycle shop in Saffron Walden. The owner said he had several customers with a similar requirement but for different uses. I suggest spamcanman asks around.

I have heard bad comments about the wireless type. I would stick with wires.

Peter

[welshy]

You can use any bicycle type mileage computer, just find out the range of wheel sizes the speedo accommodates (they can be set for a range if wheel sizes) and gear the magnetic reluctance pick up accordingly.
Mike

[spamcanman]

not sure about that Welshy, I purchased one from Halfords today the gentleman (boy) told me it's adjustable but they arn't there for wheel sizes 17" to 24".
I spoke with a guy on Sunday that told me some can be set by telling the unit how many mm's the diameter of the wheel is but none of the web sites go into detail

[durhambuilder]

I bought one for my kids bike, within the instructions was a table of common wheel sizes otherwise you had to multiply the wheel dia in mm by pi and type that number in, not sure how small it will go though, you may have to mentally multiply / divide by a factor of 10 as you are going along

[welshy]

Yes it does not matter the what size wheel it is set for as long as you know the size you can gear the speedo pick up to gain the correct ratio. for an 18" wheel the circumference is approx 56.5", If the wheel on the loco that you are driving the sensor from is say 6" then the circumference is approx 18.8". thus if you geared the sensor pick up to 3:1 this would be fairly close. obviously you can do the maths to get an exact ratio. Alternatively you could always fit 18" dia whees somewhere on the loco.
Mike

[baggo]

The one I fitted (came off Ebay!) does cater for all sizes of wheel. Think it's a cheapo Blackspur?

I did have problems with the sensor at first as it was fastened to the end of the steel swinging arm of the truck and it was giving 2 pulses per rev instead of just one. Moving it between the axle and the pivot cured it. No doubt due to the magnetic field induced into the arm by the magnet

I did calculate the wheel circumference and entered that but I found it needed 'tweaking' to give a reasonably accurate reading. Possibly the accuracy wanders at the extremes of the adjustment scale?

John

[littlechuffer]

if you have access to a hand held GPS
you can track the average speed, distance traveled etc
without any alteration to your loco
just pop it in your pocket and away you go.

[Shawki Shlemon]

On our track there are many points and signals therefore slowing down and stopping and restarting . the length of the main line is 500 K , when divided between signals and points there is not enough distant left to worry about measuring speed . A few people in our club either fitted or were interested in this and interest has died out . The only benefit I see is if one can clock distance traveled .

[garethp]

Another option is for someone who has some electronic knowledge (ie not me!) would be to construct a frequency divider so that the computer would recieve one pulse for say 5 or 10 wheel revs, a bit of fiddling with the settings on the computer would probably give accurate enough results. Or as Little chuffer mentions - use a gps, some new mobile phones have gps built in and software can be downloaded for very little money or for free.