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GPS speedo's for steam loco's???

Discussion in 'Steam Traction' started by Pannier Man, Feb 1, 2009.

  1. Pannier Man

    Pannier Man Member

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    Has anyone on here looked at the possibility of using GPS speedo's for steam loco's?

    Yes, I know they won't work in tunnels!! but as an alternative to having direct drive speedo's (when you can get one) re-calibrated for umpteen variations in wheel size, wouldn't GPS make a good alternative?

    We're not talking main line here, unless VAB were willing to accept something that wouldn't work in tunnels.

    Tom Tom's, Garmins etc, have this tendancy to default you to the nearest road whenever possible, and the MPH display is only a small part on the screen. Globaltop make something called a HG100 which is a basic 3 digit MPH display, but the display is reversed for HUD on a car windscreen, which makes displaying on a vertical plane of glass difficult. Many of these things update 5+ times a second so are gonna be pretty accurate.

    Does anyone know of something suitable, that has a directly viewed LED display that could sit in the corner of the window, is either re-chargable or could run off 12v from the battery box?

    And no, I don't want one that replies in a sexy voice "At Dr Day's junction bear right, big boy"!!


    Over to you....
     
  2. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    Garmin amongst others make suitable hand helds which will display just three things if required, eg, Speed, max recorded speed and perhaps altitude. Used now by serious loggers as mile posts are becoming more difficult to spot these days. Internal memory stores the info for later download to PC.
     
  3. Dinmore Manor & 3850

    Dinmore Manor & 3850 New Member

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    Our 38 has a GPS speedo fitted, powered by a 12 volt battery within the battery box and activated via a switch mounted underneath the reverser so that the unit is switched off whenever the loco is in mid-gear. An approx 1 1/2" square black box on the cab roof is the only external give away, the 4" dia analouge speedometer being fitted above the spectacle plate window. 9351 also has GPS speedo but operated via a vacuum switch. I shall dig out some pics for you if I can find them.

    Cheers, Mike
     
  4. Pannier Man

    Pannier Man Member

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    Thanks for the replies,... I knew someone out there would have taken this route already.

    I'd be interested in finding out which of the handheld Garmin's is recommended, just for my own railtour use, but would love any info you have on the on-board setup for the 38 and mogul. Has it been custom built or use propriatory gear?

    Thanks.

    Kevin.
     
  5. Stu in Torbay

    Stu in Torbay Part of the furniture

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    Get a receiver which has the option to connect an external antenna, and put this on the roof. The antenna needs a clear view of the sky. Reflected signals (called multipaths) of which there will be many in the vicinity of a loco cab (mostly made of metal) will introduce a range error on the receiver, which will give you incorrect position (and speed) information. Most commercial external antennas are a bit flimsy, so to protect better from rain, soot, steam, embers etc. sheath the coax cable in some flexible tube and put the antenna in some kind of plastic box (must not be conductive!) Even pot it in epoxy resin. This will help extend its life a bit more.

    We were looking at kitting out 6024's support coach with GPS via an external antenna, but haven't got around to it yet. There is a useful bracket on the end of a MK1 above the flexible coridoor connection.
    Subject to VAB etc, this would be the best as it keeps it within the gauge profile for the vehicle, but gives it a good view of the sky.
     
  6. 73096

    73096 Member

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    We had a hand held GPS speedo for 34007 that cut out in the cuttings!
     
  7. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    An external aerial is a must as it improves the accuracy over the units own when used inside.
    http://www.gpsoz.com.au/External_Aerials.htm
    As can be seen they are very low profile and are never going to cause a clearance problem.
     
  8. Small Prairie

    Small Prairie Part of the furniture

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    Not the end of the world though , use to have to look at the ground to make sure you were still moving !!!

    But out of interest , whats with all this high tech stuff for something that can be done already ...the phrase , if it aint broke dont fix it . does come to mind
     
  9. Pannier Man

    Pannier Man Member

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    If you've got the equipment, want VAB approval, then I can't see anything wrong with using existing gear. 9466 and 9600 have used direct drive speedo's that I would imagine were donated from other loco's and re-calibrated for their wheel size.
    However, as speedo's were only fitted to larger locos, the supply is limited. Modern traction has moved away from direct drive, so demand could easily out strip what's available.
    GPS would appear a good alternative if you're not looking for VAB approval, and it's not dependant on wheel size.
    Why not charge up the pocket GPS, slap one of those tiny external antenna's on the cab roof and not only see how fast your going (well, 25mph anyway) but also get some accurate milage readings, including the light engine moves and run rounds, on the trip meter? Or even better, get a D to A converter and power a pukka analogue speedo?

    Others, it seems, are already doing it!
     
  10. 8RPH

    8RPH New Member

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    The 9600 speedo fit is a new piece of equipment and exactly the same as that fitted to 4965, 4953 and 4936. This is a based on a simple tacho design that has been incorporated into a GW style housing. The crank drives a geared tooth around and a probe simply counts the teeth and produces a voltage output. This can be adjusted with a potentiometer to set it for any wheel diameter.

    I don't believe VABs would allow the use of GPS speedos on the mainline as there is always the chance the signal could fail or be blocked.
     
  11. Pannier Man

    Pannier Man Member

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    When 9600 was at Didcot a few years back, I took several pic's of the hanging bracket, crank pin nut, and what I thought at the time was a dynamo type of speedo, for future reference. Thanks for the info, didn't realise it was a probe counting type. Also took the opportunity to photo the AWS arrangement. But with things moving on, and knowing the cost of fitting OTMR to a certain other pannier, and the mainline work it's had in return, VAB approval and main line work are probably the last thing on smaller loco owners minds. No, VAB certainly wouldn't approve GPS, but for use on private lines, it must be a fairly cost effective option as a speedo, milometer etc without having to alter anything original.
     
  12. odc

    odc Active Member

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    Pioneer Garratt K1 has a GPS speedo fitted with an antena in the roof similar to 3850 and a hand held Walkee Talky type unit in the cab loosely suspended from the roof. This was seen and a cheep and easy alternative to a mechanical linkage that would need to articulate, that apart from altering the engine 100 year old appearence with brackets etc.

    Incidentallt this engine did over 8000 miles last year, not bad following all the sceptisisum it has generated.
     
  13. jeff6989

    jeff6989 New Member

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    Have a look at secondary Speedos as used by driving instructors. They are very accurate and need only 12v supply. Screening might be a problem if mounted inside cab.
     
  14. Jimc

    Jimc Part of the furniture

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    You probably want to be looking at the boating market rather than car navigation GPS. But the dubious reliability of GPS can be an issue. I have a GPS trace showing my boat leaping sideways towards the wind at 40 knots...

    Peak speed readings on GPS instruments are a lot less reliable than Rous-Marten's stopwatch.
     
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  15. Enterprise

    Enterprise Part of the furniture

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    Not strictly true. Instantaneous speed measurements depend on the algorithm used and that used in the GPS navigation software found in cheap(ish) satnavs and phones cannot be modified by the user. Sometimes inaccurate position data results in speeds that are "unlikely" as the software has not smoothed the speed over a sufficiently long period. More sophisticated GPS equipment is available for a rather more "sophisticated" price.

    All this is rather an over-simplification as for reliable and accurate speed measurement Doppler GPS is necessary. I don't think this is generally available.
     
    Last edited: Jan 1, 2018
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  16. Steve1015

    Steve1015 Active Member

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    Any decent GPS keeps a record and is therefore very useful on a loco without a speedo.
    Whilst maybe not 100% accurate it is better than nothing and is therefore a very helpful and handy tool
     
  17. BillyReopening

    BillyReopening Active Member

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    Agreed. One step further is live trackers for Steam Locos - On the main line this would be fun for enthusiasts :)
     
  18. David Humphreys

    David Humphreys New Member

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    If it is for your own use to track things, there are plenty of Apps to download for free. I use 'Speedometer' and have not had an issue within carriages because of overhead lines etc. It recorded up to 300kph/190mph on the Rome to Naples high speed train without issue. It is not linked to maps.
     
  19. 30854

    30854 Part of the furniture

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    Interesting one this. It strikes me that GPS technology is on the cusp of something very useful, simple speed readout being just scratching the surface. If the heritage movement can take up the subject amongst themselves, then head off with an agreed set of proposals to vehicle acceptance (and insurance) wallahs, with a view to developing a set of 'industry standards', there could well be considerable benefits to be had. If 'we' wait for something to be imposed from on high, other priorities could supervene. I know which scenario I'd prefer.
     
  20. Jimc

    Jimc Part of the furniture

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    There are plenty of apps that will download to a phone which will track. I use one called GPSlogger for my race boat. You can then get different apps that will overlay the GPS trace on a map. In our case how accurately the trace hits the railway track will be instructive. Obviously the greater the number of plots averaged over the better the accuracy. You'll be able to spot the plots that are wildly out, but even an average speed will be based on the zig zagging of the traces around the track, not a straight line, so will always tend to give a slightly greater distance travelled than is really the case. For the really committed there are all sorts of places where you can find out more about how to refine the accuracy.

    Don't get me wrong, GPS is very good, and a GPS trace would be ideal to see how a locomotive performed up a bank and all the rest. You just need to be aware that it does have limitations, and especially that a instantaneous peak speed measured between just 2 points should be treated with considerable caution.
     
    Last edited: Jan 2, 2018
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