In article ,
Robin wrote:
On 13/02/2019 16:54, Dave Plowman (News) wrote:
In article ,
Brian Gaff wrote:
Actually my neighbour had a Metro and boy could that thing move. The
speedo kind of just hit the end and after that it was guesswork. Only
problem with it was that it tended to be full of rust even when new.

As I said - a very optimistic speedo. Some makers today do just the same.
When making one which is within 1% accuracy should be child's play since
they are counting pulses.


I find it hard to see how a simple count of pulses can deliver 1 per
cent accuracy.

Really?

The speedo *mustn't* read low. That's a statutory
requirement: "the true speed shall not exceed the indicated speed" in
your no-doubt well-thumbed copy of the The Motor Vehicles (Approval)
Regulations 2001. Wear on tyres alone can produce a difference of 2 per
cent in the circumference.
So you start out with a speedo dead accurate with new tyres. Then the
maximum error would be 2%. Not 10% as allowed. Things have moved on since
that reg was written.

--
*Frustration is trying to find your glasses without your glasses.

Dave Plowman London SW
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