Diff ratio 2.93

Gfhug · Post by **Gfhug** » Tue Dec 22, 2015 2:19 pm

Reading through the Motor report on the E Type from March 1961 differential ratio of 3.31 is quoted as standard with 2.93, 3.07 and 3.54 being available.
But how do you get 2.93 diffs?

43/12 = 3.58 (not 3.54 as usually quoted, why?)
43/13 = 3.31
43/14 = 3.07
43/15 = 2.87 (not 2.88 as usually quoted, why?)

But I can't work out 2.93, or is my arithmetic all wrong?

Geoff

44DHR · Post by **44DHR** » Tue Dec 22, 2015 2:52 pm

Geoff,

There are several different Crownwheels you can use in the Salisbury 4HA differential.

A 41 tooth Crownwheel to a 14 tooth Pinion gives you the 2.93:1 ratio, (actually 2.928).

The ratios are usually rounded to the nearest digit.

The 3.54:1 ratio is 46 over 13, (or actually 3.538)

The 2.88:1 ratio is 49 over 17, (or actually 2.882)

regards,

Dave

Post by **mgcjag** » Tue Dec 22, 2015 2:59 pm

Hi Geoff..2.93 were an option on the 3.8E

Gfhug · Post by **Gfhug** » Tue Dec 22, 2015 3:43 pm

Dave and Steve, thank you. Neatly explains it all, and that I neded to try different numbers in my arithmetic :?

rolando38 · Post by **rolando38** » Tue Dec 22, 2015 4:47 pm

wow, very good explanation !
now do you have an explanation for counting in 1/16 and 1/32 of inches instead of 1/10 or 1/100 ?

because so much I fully understand the interest of inches and feet in ancient times where it was very practical to have its own measurement tools on one's own body, so much I do not understand why these units weren't simply divided by 10, as even in the UK, people have 10 fingers, and it's easier to remove a zero or add a coma than divide by 1/16ths (don't even manage to prononce it..) ?

:D

but maybe I'm being too Cartesian...

malcolm · Post by **malcolm** » Tue Dec 22, 2015 5:27 pm

But Ronaldo, the 1/16th etc system has advantages. If you divide 10 by 2, you get 5. You then go down to 2.5, 1.25 and increasingly odd numbers. With the imperial system, you can start with 1/4, then dividing you go down to 1/8th, 1/16th, 1/32nd and so on ad infinitum. That's also why double 16 was a favourite finish for dart players. If you miss and get a single, you're down top double 8, then 4, then 2, then 1.
If you miss double ten, you go to double 5, but then you have to get a single 1 to leave double 2 and waste a dart

PeterCrespin · Post by **PeterCrespin** » Tue Dec 22, 2015 5:51 pm

malcolm wrote:But Ronaldo, the 1/16th etc system has advantages....That's also why double 16 was a favourite finish for dart players. If you miss and get a single, you're down top double 8, then 4, then 2, then 1.
If you miss double ten, you go to double 5, but then you have to get a single 1 to leave double 2 and waste a dart

Somebody buy this man a pint of bitter, please!

And put 'Land of Hope and Glory' on the jukebox.

T'riffic! :-)

rolando38 · Post by **rolando38** » Wed Dec 23, 2015 7:39 am

well I admit I ddi'nt get the dart part of the explanation, but I got the 1/16 to 1/32 part
and you can do excatly the same with decimals: if you divide 1/10 by 2 you get 1/20 and again by 2 you get 1/40 etc...

Gfhug · Post by **Gfhug** » Wed Dec 23, 2015 8:35 am

OK Rolando, when was the last time you saw measurements in 1/20, 1/40, 1/80 of a metre

malcolm · Post by **malcolm** » Wed Dec 23, 2015 9:56 am

Still waiting for my pint of (warm) bitter

christopher storey · Post by **christopher storey** » Wed Dec 23, 2015 10:41 am

The decimal v Imperial argument will rage for as long as numbers are still in use. A gross failing of the decimal system is its inability to cope with thirds, sixths, twelfths etc and there is no way round this : wherever one cuts off the recurring series it will be imprecise . It is also a peculiarly insensitive measure - compare one-tenth with one-thirtysecond etc. About the only thing one can say in favour of it is that one can just move the decimal point along in either direction in converting to or from units, tens, hundreds etc

Mich7920 · Post by **Mich7920** » Wed Dec 23, 2015 2:00 pm

Something is sure if we would like to change the world, there's really a lot of things more urgent...
Happy new year 2016 from France where I love my 9/16 or 1/2 on my E Type !

PeterCrespin · Post by **PeterCrespin** » Wed Dec 23, 2015 2:26 pm

malcolm wrote:Still waiting for my pint of (warm) bitter

That's another thing we do well. Wait patiently in queues without too much fuss. Don't try that in New York, Paris or Rome :-)

Here's a tenner, get me a packet of ready salted while you're up there. I'll keep this chair by the log fire.

JagWaugh · Post by **JagWaugh** » Wed Dec 23, 2015 3:02 pm

christopher storey wrote:The decimal v Imperial argument will rage for as long as numbers are still in use. A gross failing of the decimal system is its inability to cope with thirds, sixths, twelfths etc and there is no way round this : wherever one cuts off the recurring series it will be imprecise . It is also a peculiarly insensitive measure - compare one-tenth with one-thirtysecond etc. About the only thing one can say in favour of it is that one can just move the decimal point along in either direction in converting to or from units, tens, hundreds etc

I grew up conversant in both systems (Canada started going metric while I was in the 2nd grade). Now I live in a metric world (Switzerland), and regularily hear diatribes about how the inch system is impossible. Mentally I tend to work in metric for distances over an inch, and inch for everything below that. Frankly, I just don't understand the complaints - both systems have strengths and weaknesses, I guess I am just an anomaly by having learned both systems at an early age.

Andrew

Gfhug · Post by **Gfhug** » Wed Dec 23, 2015 3:56 pm

Now we can always start on pounds shillings and pence, that does confuse the furriners!

Simon P · Post by **Simon P** » Wed Dec 23, 2015 4:22 pm

Gfhug wrote:we can always start on pounds shillings and pence

Some of us still prefer to price things in guineas Old Boy! :D

Gfhug · Post by **Gfhug** » Wed Dec 23, 2015 4:55 pm

Roods, perches, bushels, pecks anyone?

Post by **mgcjag** » Wed Dec 23, 2015 5:40 pm

Give you a monkey for some

PeterCrespin · Post by **PeterCrespin** » Wed Dec 23, 2015 6:27 pm

JagWaugh wrote: I grew up conversant in both systems...

Mentally I tend to work in metric for distances over an inch, and inch for everything below that.

Andrew

I'm the opposite outcome of a similar upbringing. My education after about 10 years old and my whole professional life has been SI units but I tend to think of small sizes in metric and larger units in Imperial (there not being many 2-3 meter humans, though sadly all too many over 100-150kg). Having said that, it is utterly bizarre to find so many tape measures etc. over here that aren't even 'bi-lingual' so that many Americans don't even have the option to 'acclimatize' or ease themselves gently into the 20th century, let alone the 21st.

I'll probably be dead before my first reflex is to think of L/100km instead of mpg though...

David Oslo · Post by **David Oslo** » Wed Dec 23, 2015 6:39 pm

Any classic car owner should never think of m.p.g. nor L/100km :D

Just fill 'er up and enjoy :D

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