Changing ring and pinion gears

[David Cochrane]

Chris Garner posted this a few years ago:

Some of you will know of W.H.Charnock, writer of motoring books and verse.

The following, written in 1951, is taken from one of his books entitled " Down in the Sumps"

C. W. & P.

I had a little axle; it gave me four point five,
The wind sang sweetly past my ears, my motor was alive;
I thought "This is terrific - I've only one desire -
"I'll go a little quicker if I gear a little higher."

I have a little axle; it gives me four to one,
My life is spent on second, my motor gets no fun,
And traffic is a torment and climbing hills a pain;
I wish I had my four point five to drive me once again.

[AustinWood]

It is also necessary to consider the stresses of letting an engine labour in too high a gear.

[circeonya@hotmail.com]

Not the first time I have heard that the A7 engine is much happier in the medium and just over rev range than being laboured at low revs with high throttle openings. My Austin A60 was doing 4,000rpm at 60 miles an hour which was considered a cruising speed in the Sixties, probably our little cars are not going to come to much harm reving at 4000 if the engine is good condition. We were advised with the sports car (which had a pressure fed crank and a close ratio box) that it was time to change down around 2000. Quite a different approach to the modern over square engines.

[Bob Culver]

Exactly when cranks exceed the fatigue limit is unclear. For failure it is reckoned to take 1 to 10 million cyles just above the limit, but at 100,000 miles a seven crank has done more than 500 million revs.
Provided there is no pinging and the spark is not very advanced the wide throttle low speed loading on a small bore engine is not formidable, and the cycles do not clock up as they do at steady high rpm.
Remarkable are modern large bore engines which attain very high cyl pressures at their typical operating speeds of just 2000 rpm or so.
It is surprising how well many of the 1960s engines survived at 4000 rpm. my 1964 Minx at 180 000 has done a lot of running at 60mph, although the stroke is same as Seven..