ChasR
RR Helper
motivation
Posts: 10,309
Club RR Member Number: 170
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May 24, 2012 15:01:29 GMT
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As some of you may know the Stag has no speedo since the ZF gearbox never came with a speedo drive (unlike the original Borg Warner 35 it has replaced). With me second guessing the speeds I go at when I leave the Sat Nav at home I figured it was about time I got it working and maybe one of you chaps here have hit a similar conundrum with a gearbox/diff swap. At the moment from when I got the car from the late previous owner the car has the original Smiths mechanical speedometer with a motor fitted in the rear which AFAIK went to a chip (now long gone) and then to a Ford speedo sensor which used a trigger wheel as a pickup off the prop:   On the basis that the trigger wheel was throwing the prop a few mm off centre and causing some horrific vibrations I have ditched the idea of going back to that. I was considering constructing a chip using a Frequency to Voltage converter (like an LM2917) and maybe using something like reflective tape or the prop bolts to go about giving a pulse. Hopefully I should get a sensor which can work. Before I go down an avenue when I am weeing in the wind do you chaps have other or proven ideas I can go down. I know Smiths sell an electronic speedo but I was trying to avoid spending in excess of £200 to fix my issue  . |
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May 24, 2012 15:18:37 GMT
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some pushbike speedos are accurate up to 100mph, myself and several others have run them on ratbikes no problems. I used to use the £8 ones that appear in aldi every now and again.
Work off a magnet that you araldite to the wheel, and the pickup goes on the brake caliper. Run the cable back to the unit, tell it the circumference of your wheel and your sorted.
Or, spend a bit more and buy a cordless one....
For extra points, gut the speedo and fit the unit behind the original dial showing thru the odometer hole....
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May 24, 2012 16:05:09 GMT
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Have a look on eBay as there's a lad on passionford just bought a kit that does this,it's basically a proxy sensor that counts the number of pulses and converts it into a speed reading,I.e 100 pulses = 10mph etc.
I can get you a sensor that runs off 12v and gives an output pulse on/off everytime a metal object is placed near it.
You could rig up a simple a/d counting circuit to send the signal required to the speedo.
He was told to fit it to an undriven wheel although I'm not sure why?
Also,an abs sensor and sensor ring would do a very similar job,there's millions of different types as well as they tend to just fit over the hub end or over a brake drum etc.usually a heat gun is a good enough source to remove them,that toothed wheel set up you've got there looks like proper overkill,they usually made of nothing more than 0.5mm steel.
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v8ian
Posted a lot
Posts: 3,832
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May 24, 2012 20:59:06 GMT
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Perhaps not quite what you are looking for, but looks like a simple piece of kit to install,
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style.
Austin A35van, very different------- but still doing it in style, going to be a funmoble
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Last Edit: May 25, 2012 8:42:40 GMT by ianboyd
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ChasR
RR Helper
motivation
Posts: 10,309
Club RR Member Number: 170
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May 25, 2012 20:51:06 GMT
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Good to see a variety of replies . Have a look on eBay as there's a lad on passionford just bought a kit that does this,it's basically a proxy sensor that counts the number of pulses and converts it into a speed reading,I.e 100 pulses = 10mph etc. I can get you a sensor that runs off 12v and gives an output pulse on/off everytime a metal object is placed near it. You could rig up a simple a/d counting circuit to send the signal required to the speedo. He was told to fit it to an undriven wheel although I'm not sure why? Also,an abs sensor and sensor ring would do a very similar job,there's millions of different types as well as they tend to just fit over the hub end or over a brake drum etc.usually a heat gun is a good enough source to remove them,that toothed wheel set up you've got there looks like proper overkill,they usually made of nothing more than 0.5mm steel. Do you have more information on this? It would nice to keep the original speedo or something that does not look too different . Oddly enough I do have two Stag speedos to play with, and it does seem it is not too tricky to gut one and transfer the bits over from another speedo . Let me know how you get on . |
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May 25, 2012 21:44:02 GMT
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I modified a smiths rev counter for my herald as the original one was an inductive one. I used an NE555 chip as they were cheaper than lm2917's (and I blew a couple).   that was for working with electronic ignition and a standard coil. |
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May 30, 2012 20:10:42 GMT
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Some (possibly all) bubble Rover 200s have an electronic speedo that are 'driven' from a hall effect sensor mounted on the GB (in place of the mechnical drive). That might give you an electronic speedo you can butcher.
As for the bike computer idea, I tried one in the rally car as I was too tight to buy a proper rally trip meter (£3.99 vs £300!). It worked really well up to about 50 mph, but just 'faded' after that. That was a Lidl cheap model that used a reed switch and I suspect as speeds increased the switch wasn't getting enough time to energise as the magnet whizzed past. The magnet was mounted on the drive shaft and the reed switch on a bracket as close as I could get it. I do wonder if an electronic system using a hall effect sensor would operate at higher speeds. Does anyone know how the 'wireless' bike computers work?
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`state
Yorkshire and The Humber
Posts: 1,215
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May 31, 2012 14:32:49 GMT
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Have a look at the gps speedo`s over on www.speedhut.com. I'm putting a saab engine into my chevette along with the omega box so had the same problem.Think I'm going to go with one from speedhut as at least the gps will be accurate. |
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Look at all the plastic people who live without a care.Try to sit with me around my table,but never bring a chair.
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May 31, 2012 14:48:07 GMT
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Some (possibly all) bubble Rover 200s have an electronic speedo that are 'driven' from a hall effect sensor mounted on the GB (in place of the mechnical drive). That might give you an electronic speedo you can butcher. As for the bike computer idea, I tried one in the rally car as I was too tight to buy a proper rally trip meter (£3.99 vs £300!). It worked really well up to about 50 mph, but just 'faded' after that. That was a Lidl cheap model that used a reed switch and I suspect as speeds increased the switch wasn't getting enough time to energise as the magnet whizzed past. The magnet was mounted on the drive shaft and the reed switch on a bracket as close as I could get it. I do wonder if an electronic system using a hall effect sensor would operate at higher speeds. Does anyone know how the 'wireless' bike computers work? hall effect sensors should work, as that's what was used to trigger ignitions on many motorcycles and are used on the motorcycle replacement speedo's  |
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or if you'd want something FAR easier.... I've got an old set of jag XJS V12 clocks going spare......  Electronic speedo, which unbolts from the rest rather easily, nice simple connections too, and the old-school solid metal clock backing plate. Yours for £15 posted if it's of use ~EDIT No2... accidentally deleted the pic off photobucket, and it's on another pc.. have a generic jag clock in exchange! lol |
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You're like a crazy backyard genius! |
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ChasR
RR Helper
motivation
Posts: 10,309
Club RR Member Number: 170
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That looks like a possibility Chairchild . One thing I wish to ask though is whether you can separate the speedometer from the rest of the casing and what size roughly is it? A Stag stock speedometer is 100mm in diameter . |
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10cm, easily comes apart - undoes with 3 nuts   simple 12v supply, earth, and the input runs at 2000 pulses per mile. some pretty funky gauges too   also - had a peek on google as to what stag clocks looks like, and they're the "normal" Smiths type If I'm right? In which case it has a glass front screen, which won't work with the trip reset button.... The front of the jag clocks is curved, so useless too. Easy fix though - replace the glass with some suitable thickness acrylic, and drill a hole |
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You're like a crazy backyard genius!
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