ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
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Sept 16, 2011 13:36:23 GMT
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On my Stag I have a slight issue of no speed.
Whilst the original Borg Warner Type 35 gearbox had a mechanical speedo drive off the gearbox, the ZF unit (4HP22) in mine does not. The cars that came equipped with it had an electronic speedo pickup off the rear diff AFAIK (Jaguar XJ40/XJS 6 Cylinder, BMW E30).
My question to you is whether it is possible for me to make an electric or mechanical speedo drive. The PO had a toothed wheel on the front of the prop I guess for this purpose with a Ford Speedo pickup. Would it be worth pursuing how this system worked (if so, how would you go about it) or would you do something else.
FWIW, the car is still on the original Smiths mechanical speedo, with a motor fitted in the back of it. No other boards, useful wiring is present.
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Sept 16, 2011 18:10:05 GMT
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A system with a toothed wheel/magnetic pick up on the prop works by counting the pulses every time the prop turns. If you've got a smiths gauge already converted then you're already half way there. It should just be a case of interpreting what wiring you've already got, verifying its all functional and then hooking it up.
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1994 Rover Metro
1994 Peugeot 405 Estate
1991 Rover Metro Gti 16v
2001 Fiat Seicento Sporting
1999 Fiat Punto 1.2
1994 Peugeot 106 Xnd (x3)
1991 Westfield 7
2004 Landrover 110 SW
2003 Seat Ibiza 1.9Tdi Sport
1959 Ford 107e Prefect
1992 Suzuki Vitara
2008 Skoda Fabia
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Sept 17, 2011 21:11:43 GMT
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Does the existing speedo work? Why are you trying to change it.
The obvious answer to your question is 'of course you can' - you can make anything. Manufacturers get their speed signal from all sorts of places. Some do it off a wheel speed sensor. Some off the diff. Some electronic and some with a cable or rod.
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ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
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Sept 17, 2011 22:43:24 GMT
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Does the existing speedo work? Why are you trying to change it. The obvious answer to your question is 'of course you can' - you can make anything. Manufacturers get their speed signal from all sorts of places. Some do it off a wheel speed sensor. Some off the diff. Some electronic and some with a cable or rod. To put it simply I have a working speedometer, but due to a lack of speedo drive (different gearbox (stock gearbox had a speedo drive, the ZF does not have any speedo drive) I have no working speedo ATM. Whilst I have a sensor, I have no idea on how it would work/interpret the signals. |
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ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
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Sept 21, 2011 10:55:01 GMT
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The biggest issue is that I have no idea on how to make it work. Bar a speedo with a motor in the back, a toothed wheel and a Ford speedo sensor, interpreting the signals and converting them into something the motor on the speedo can reproduce is another matter.
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Sept 21, 2011 15:15:45 GMT
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well an electronic speedo doesnt have a motor in it.
the transducer works the same as the pickups for the ignition on a ford edis unit.
what you need to find out is what interval the original speedo used to count ie 36 tooth pick up or whatever. once you find out you could get a lasercut wheel, mount it on the hub somewhere with the pickup and run the wires to the speedo.
i could explain better over msn or something
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Sept 22, 2011 18:46:06 GMT
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been racking me brains trying to remember which car it was that had the speedo drive off the front wheel via a speedo cable?
had a square hole on the hub to drive the cable end, but for the life oif me i cannot remember,poo!!
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Sept 23, 2011 11:26:01 GMT
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What does the motor on the back of the speedo look like? I'm guessing the PO fitted the motor as they couldn't find an electric speedo they liked the look of. If there's no evidence of any electronics to drive it I wonder if it might be a stepper motor that rotates a set angle for each pulse it receives.
If it worked ok before then maybe replacing the toothed wheel would be the easiest way to go. Did the old wiring get removed? Any way to adapt the toothed wheel you have to the new prop shaft?
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Sept 23, 2011 11:36:17 GMT
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been racking me brains trying to remember which car it was that had the speedo drive off the front wheel via a speedo cable? had a square hole on the hub to drive the cable end, but for the life oif me I cannot remember,poo!! I'm sure there are plenty. Imps? |
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...proper medallion man chest wig motoring. |
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Sept 23, 2011 11:47:54 GMT
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been racking me brains trying to remember which car it was that had the speedo drive off the front wheel via a speedo cable? had a square hole on the hub to drive the cable end, but for the life oif me I cannot remember,poo!! Aircooled VWs do this, along with plenty of other cars. |
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Sept 24, 2011 7:16:10 GMT
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I bought a scrap FX4 and that had a notched disc on the prop flange of the BW35 autobox and a sensor that then sent info to the Taximeter to calculate the charge. Push bike speedos work in similar way - magnet on wheel with reed swtich sensor on fork. I'd go with a prop flange trigger, sensor and proper electronic speedo which can be obtained from here - www.merlinmotorsport.co.uk/p1218/SMITHS-CLASSIC-SPEEDO-100mm-DIAMETER/product_info.htmlPaul H |
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Sept 24, 2011 12:04:33 GMT
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been racking me brains trying to remember which car it was that had the speedo drive off the front wheel via a speedo cable? had a square hole on the hub to drive the cable end, but for the life oif me I cannot remember,poo!! I'm sure there are plenty. Imps? Imps indeed - althoughdriven by an offset peg in the hub dust cap rather than a square hole. I would imagine that most rear-engined cars with mechanical speeds will drive it from a front wheel. |
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