jonbeedle
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 posted on 31/1/05 at 06:53 PM |
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Instruments
I've just fitted a set of clocks from an MGB GT. Anyone ever done this? I've no idea if they will work especially the speedo. I'm
guessing the tacho will be driven off the ignition coil and the oil pressure, water temp and fuel gauge should be straighforward enough. Any ideas on
how to drive the speedo?
If it all goes 'breasts aloft' then I guess I could fit an electronic one but I would like to see if I can get this to work as I'm
trying to stay faithful to the 'book' philosophy of building within the budget of £250.....yeah right!
Cheers
Jon
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britishtrident
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| posted on 31/1/05 at 07:28 PM |
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Speedo is no problem--- somewhere near the bottom of the dial in a tiny font you will find a number between about 900 and 1100, this is the number
of turns per mile, the other info you need is the intended tyre size, diff ratio and the ratio of the speedo drive.
If you post this on the forum I can give you a % error of the speedo calibration.
You may have trouble getting the speedo drive gear ratio -- if it is a type 9 box with the blue gear I already have the info. The spedo cable from
1960s Ford should fit -- although it would be best to use a rightangle drive.
The tacho is also easy if you can post a picture of the rear of the tach I should be able to work it out for you.
Oil and water if electric require a BL instrument voltage regulator --- an alternative is to buy a combined oil and water gauge from an MG Midget
which purely mechanical these can usually be foud on ebay for about 20 to 30 pounds in good cleean working condition.
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JonBowden
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| posted on 31/1/05 at 07:45 PM |
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ok, so once you have the % error of the speedo calibration, what does one do about it to get it reading right ?
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britishtrident
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| posted on 31/1/05 at 08:29 PM |
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quote:
Originally posted by JonBowden
ok, so once you have the % error of the speedo calibration, what does one do about it to get it reading right ?
It might be just spot on in theory mine is 1000 tpm speedo, blue drive gear, 3.89 diff 185/60x14 tires -- bear in however mind speedos read
faster with age mine is brand new old stock Triumph.
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jonbeedle
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| posted on 31/1/05 at 09:57 PM |
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That is all very helpful, thanks. I will set about gathering the required information. Not sure which gearbox I have though, all I know is it is a
four speed from a Mk2 Escort. Is there a way of telling what type it is? My axle is also from a mk2 Escort but again I've no idea what the diff
ratio is. How do I find out?
Cheers
Jon
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stevebubs
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| posted on 1/2/05 at 12:57 AM |
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The obvious one is to make a mark on the tyre and prop, and see how many turns of the prop is required to turn the rear wheels 1 revolution.
Given there's not an infinite number of ratios available, it should be pretty straightforward to work out 4.11, 3.89, 3.54 etc.
Stephen
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jonbeedle
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| posted on 1/2/05 at 09:36 AM |
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Many thanks!
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jonbeedle
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| posted on 1/2/05 at 09:45 PM |
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quote:
Originally posted by britishtrident
Speedo is no problem--- somewhere near the bottom of the dial in a tiny font you will find a number between about 900 and 1100, this is the number
of turns per mile, the other info you need is the intended tyre size, diff ratio and the ratio of the speedo drive.
If you post this on the forum I can give you a % error of the speedo calibration.
You may have trouble getting the speedo drive gear ratio -- if it is a type 9 box with the blue gear I already have the info. The spedo cable from
1960s Ford should fit -- although it would be best to use a rightangle drive.
The tacho is also easy if you can post a picture of the rear of the tach I should be able to work it out for you.
Oil and water if electric require a BL instrument voltage regulator --- an alternative is to buy a combined oil and water gauge from an MG Midget
which purely mechanical these can usually be foud on ebay for about 20 to 30 pounds in good cleean working condition.
The number on the speedo is 1000, the tyres are 185/70x13 and the diff is 3.89. How do I find out the ratio of the speedo drive?
Cheers
Jon
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NS Dev
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| posted on 1/2/05 at 11:57 PM |
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I went for the budget approach a different way..................don't bother with the clocks!
Use a pushbike speedo (£12 or so), sequential shift light (£15 brand new from autojumble), low oil press light (with a sender that earths out at quite
a high pressure so it's not too late!), high water temp light, charge light, main beam light, brake warning light, indicator warning lights,
integrally lit hazard light switch, integrally lit foglight switch.....................that's about it!
All the lights are 12v LED's, with black anodised alloy bezels and flat faces......just big enough to engrave the warning symbol onto the brake
one with my mates engraving machine!
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flak monkey
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| posted on 2/2/05 at 09:34 AM |
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I was thinking about these pushbike speedos the other day, and this is probably a silly question. IIRC the sensor/magnet is set up on the front wheel
for bike speedos. Now when it comes to SVA how is the calibration checked? If on the propshaft like most electronic speedos i assume it can be done on
the rolling road somehow. But how is it done when the sensor is on the undriven front wheels?
Cheers,
David
Sera
http://www.motosera.com
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Peteff
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| posted on 2/2/05 at 10:34 AM |
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We extended the wire with some speaker cable and ran one off the rear wheel and it passed.. That was a Sigma from Halfords. It was 5 years ago at
Derby test centre. Calibrated by measuring wheel circumference with a piece of string it was dead accurate at all speeds up to 80mph.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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nick baker
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| posted on 2/2/05 at 11:36 AM |
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In theory you can also run it off the prop-shaft to the diff... Just multiply the figure that you calibrate it with (rolling circ of wheel or
diameter of wheel) by your diff ratio......
Also ran the Speedo for a buggy from the inboard CV joint cup once... worked a treat with the magnet strapped on with a Zippie.... didn't have
to worry about routing wires over wishbones and hubs etc...
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