On Sat, 22 Feb 2003, at around 21:08:03 local time, William Davies
<bill@rarebits4classics.co.uk> wrote:
>
>----- Original Message -----
>From: Michael Hargreave Mawson <OC@46thFoot.com>
>
>> Alternatively, is
>> it physically possible that a single gearwheel has been replaced with
>> one from a GT6, to give a quieter/smoother cruising gear?
>
>In a word - no.
Splendid - that rules that possibility out, then.
>
>> John? Are you there? Is there a speedo drive gear that could have
>> been fitted to a 1500 gearbox that would give a 9% *low* reading on the
>> correct speedo? And which speedo drive gear should I replace it with?
>
>I don't think John's on this list, though he's a regular on the
>spitfire-enthusiast yahoo group and (as you know) the Herald group.
Thanks for that. I unsubscribed from the spitfire-enthusiast group
some time ago, and the question would be off-topic on the Herald group,
so I'll drop him a private e-mail.
>
>> Ah, well, you see, I did have a problem with the original speedo in this
>> car, and fitted a replacement, which I then calibrated to the rev
>> counter (assuming a stock gearbox). The magnet *is* tired, and it
>> required a 7-9 mph tweak at rest to give a "correct" reading at speed.
>> "Correct" in this instance meaning 18 mph per 1000 rpm in fourth. The
>> speedo still reads 18 mph per 1000 rpm, so it hasn't deteriorated any
>> further over the last year.
>
>This would make me even more confident that the fault lies within your
>speedo. I can supply an almost limitless supply of used speedos, or it
>should be possible to have your original unit recalibrated. As long as
>I know roughly what the error is I'm inclined to live with problems
>like this,
I am too - but I'm still not convinced that I know what the error in the
speedo is. The rev counter is totally separate from the speedo, and I
presume that it is more-or-less accurate. *If* I have a standard
gearbox on the car, then I have recalibrated my speedo correctly to show
18 mph per 1000 rpm. However, given that the odometer is reading low
by nearly 9%, something about that *gearbox* has to be non-standard,
doesn't it? The gearwheels themselves and/or the speedo drive gear.
Until I can work out whether it is just the speedo drive gear, or
whether I have a GT6 box on there, I won't know whether my speedo is
reading 9% low as well as my odometer. Logic suggests that it is just
the speedo drive gear - but the evidence of my wife's car's speedometer
suggests otherwise (not that I trust Mazda not to have "enhanced" the
performance of that car by making the speedo read high...)
Given that it is not possible to put GT6 gearwheels into a Spitfire
gearbox, is there any easy way to tell what gearbox I have from a quick
visual inspection? Is there a number stamped anywhere??
ATB
--
Mike
Ellie - 1963 White Herald 1200 Convertible GA125624 CV
Connie - 1968 Conifer Herald 1200 Saloon GA237511 DL
Carly - 1977 Inca Yellow Spitfire 1500 FH105671
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