Guest29 January 2008 at 11:58 #47168
My speedo reads about 10-15mph slow. Can anyone reccommend an instrument restorer. John Marsh at Vintage Restorations says that the instrument is a Governor type and he has no parts for o’haul. Any ideas?Peter S3029 January 2008 at 12:18 #47169
I have two suggestions: look under “Some links” in the main menu, go to classic car-directory-homepage and do a search, select instruments, you will get some companys (I just tested it).
I assume this is a speedo that has a rotating magnet, which became weak. I would be tempted to take the thing apart..Colin M3429 January 2008 at 20:34 #47170
1. Firstly if it was not my ‘best’ spedo, my non-recommended action would be to take it to bits and play with the spring that counterbalances the bob weight and then recalibrate on the lathe running at various speeds. Try different springs and tensions….not recommended with anything other than a ‘spare’ spedo picked up at an autojumble! Of course if you do not have a lathe, go straight to step 2.
2. Recommended action for your precious device. Do a calibration run to produce en error curve – percentage error at various speeds. This should produce a graph of percentage error vs ‘indicated speed’. Decide the error over the range – say 15%, then contact Speedograph Richfield http://www.speedograph-richfield.com/ and discuss your needs. They are very helpful and have told me they can make up a gearbox of a suitable ratio to fix most problems. This is very useful if you have geared up you back axle – for example putting a Rapide ratio into an M45.
By the way I fix my own capilliary temperature gauges. You do need courage to attempt one but I love doing them. Its probably the smell of ether, but of course nowadays it is getting more difficult to persuade ones local pharmacist to sell it to you.
Regards to all
Colin MallettAlistair Crawford30 January 2008 at 09:44 #47171
you said … “This should produce a graph of percentage error vs ‘indicated speed’. Decide the error over the range – say 15%, then contact Speedograph Richfield http://www.speedograph-richfield.com/ and discuss your needs. They are very helpful and have told me they can make up a gearbox of a suitable ratio to fix most problems.”
I have had a gearbox made up to fix my (governor) speedo by Speedograph and it works fine, and is accurate as verified by my Road Angel satnav.
The process can be a bit easier – contact them/go to their website and get their form which asks you to measure car wheel revolutions by sticking tape on tyres and rolling it along your driveway then measuring distance, whilst your able assistant notes the number of speedo cable revolutions. Send off that completed form with your speedo and cable and it comes back with a small custom-made gearbox inserted into cable, that recalibrates it, and a relatively small invoice (about ?100 for me inc packing and tax).
Only remaining problem with speedo now is that it flickers up to 30mph then stabilises but I have learned to ignore that. No doubt when summer returns and Lagonda outings become more frequent, the flickery speedo will irritate me and I will strip down and clean and lubricate the cables and all will work perfectly.
regardsColin M3430 January 2008 at 13:05 #47172
Of course you are right! I wrote the bit about doing the calibration graph and then went on the web site and found they did it all! And I love the idea of using a GPS to do the final calibration!
By the way dear readers Speedograph also do new brake cables for Lagondas such as the 2 litre and 16/80. All in all very helpful.
Cheers ColinGuest30 January 2008 at 16:47 #47173
Dear Peter, Colin, Alistair. This has been another example of the benefits of this Forum. Many thanks for your constructive advice. I have now spoken to Richfield who do indeed sound very helpful. All I have to do now is to persuade my wife to push the car down the drive whilst I count the cable revolutions. Or have I got something wrong.
During a conversation with John Batt he volunteered the services of one of his contacts who is happy to repair these instruments “on the kitchen table”. I’ll go the Richfield route though.
Donalanelliott1 February 2008 at 18:05 #47174
I have only just joined the Forum, so my comments may be a bit late. You can just pull-off the speedometer pointer, advance it about 10 mph, and then put it back! Regards, Alan ElliottColin M342 February 2008 at 10:31 #47176
I would like to add to Alan?s suggestion of just moving the pointer. This was on my mind when I mentioned doing the calibration run to produce the error curve. The error will not be linear and if you follow Alan?s suggestion, you could have the speedo/rev counter running 100% accurate at one point. This ought to be at the most critical part of the range ? say 50 mph or 2500 rpm. Beyond the, you will have established the error and will just have to live with it. Of course there is enormous fun to be had ?on you kitchen table? playing with the spring tension as well?.
When I repair temperature gauges, once re-filled with ether, I use the ?Alan Elliot method? for calibration. Using a digital thermometer and an electric kettle I move the pointer to read dead right at about 90 degrees c. This is ?good enough? to warn me that something has gone wrong with the cooling and who cares whether the temperature gauge indicates 80 degrees when the car actually runs at 76 degrees ? or vice versa for that matter.
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