- Thread starter beeRS
- Start date
RWD3M
Forum Supporter
- Messages
- 3,543
- Location
- Wiltshire, UK
I'm fairly sure I've mentioned it before but in 1973 (or thereabouts) Girling (the automotive brake people) went metric. As a result, the formerly 2" piston, brake calipers they supplied to Triumph (amongst others) now had 50mm pistons. No big deal really, but they also changed the mounting holes from 7/16" to 12mm. So, did Triumph put an M12 thread in the front uprights of the small chassis triumphs? Of course not, they came up with a bolt with an 11/16" (I think, imperial anyway) head, a 12mm shank and a 7/16" UNF thread 
As an aside, I worked in landing gear research at Airbus until I retired in 2020 (thanks covid!) and spent many hours trying to convince our bright young thing engineers that Aircraft are still designed in feet and inches and that measurement of 152.4mm on an A320 axle wasn't specifically designed to be 152.4mm! Honestly, I've seen some ridiculous numbers in documents relating to the dimensional vagiaries of varous aircraft parts, all because they insist on trying to use mm on aircraft designed in inches. Oh, and more often, the inches and tenths of inches standard too.
As an aside, I worked in landing gear research at Airbus until I retired in 2020 (thanks covid!) and spent many hours trying to convince our bright young thing engineers that Aircraft are still designed in feet and inches and that measurement of 152.4mm on an A320 axle wasn't specifically designed to be 152.4mm! Honestly, I've seen some ridiculous numbers in documents relating to the dimensional vagiaries of varous aircraft parts, all because they insist on trying to use mm on aircraft designed in inches. Oh, and more often, the inches and tenths of inches standard too.
Perry Owens
Member
- Messages
- 832
Whose idea was it to name SI units after dead Scientists? Most shooters could visualise a muzzle energy of 5160 ft/lb but not 7000 Joules. When you look up what a Joule is you find it's one Newton acting over 1 metre, so now you have to look up Newtons.
Stueeee
Old git
- Messages
- 1,079
- Location
- N W Kent
Or alternatively, as physics teachers were fond of saying 'what's a Watt -well it's one Joule per second' I got a better idea of power remembering that there are 746 Watts in a horsepower.
Dozzer
Forum Supporter
- Messages
- 542
- Location
- Essex/Suffolk border
When the LR special vehicle team was switching over from Imp to Metric, we had some Discoveries and Disco commercials that had a mix of both on the body panels and when we spoke to one of the Browns lane team they said while they were using up the old stock they had both on the line,
As a design engineer I can see why they did that - it allows the use of all the stock of existing uprights with the new calipers, it doesn't require a new part number for new uprights, with the chance the right side could be the old one, the left the new . . it means new calipers will fit existing vehicles, with the additional benefit the customer has to spend more money on the new bolts. No need to try to record yet another chassis number where something changed.I'm fairly sure I've mentioned it before but in 1973 (or thereabouts) Girling (the automotive brake people) went metric. As a result, the formerly 2" piston, brake calipers they supplied to Triumph (amongst others) now had 50mm pistons. No big deal really, but they also changed the mounting holes from 7/16" to 12mm. So, did Triumph put an M12 thread in the front uprights of the small chassis triumphs? Of course not, they came up with a bolt with an 11/16" (I think, imperial anyway) head, a 12mm shank and a 7/16" UNF thread
I think all Ford engines are the same - xflow in my trials car certainly is.
I use both. For certain things each has its advantages. For example if you are doing calculations on a new boat design it is far far easier to work in metric, but then design software came along & all those tedious calculations that used to take days can now be done instantly at the press of the "Design Hydrostatics" button. That made everything much easier!
Gareth J
Member
- Messages
- 3,666
- Location
- North Cornwall
Imperial IS by definition, metric.
While that's true and doesn't mean you can repeatably use an M6 bolt in a 1/4"bsw hole, it does make it easier to think of imperial as just some convenient size units that help us convey an appropriate level of accuracy without defining it.
"How long are your sausages?"
"About 5 inches"
"About 125mm"
The latter implies too much accuracy.
While that's true and doesn't mean you can repeatably use an M6 bolt in a 1/4"bsw hole, it does make it easier to think of imperial as just some convenient size units that help us convey an appropriate level of accuracy without defining it.
"How long are your sausages?"
"About 5 inches"
"About 125mm"
The latter implies too much accuracy.
RWD3M
Forum Supporter
- Messages
- 3,543
- Location
- Wiltshire, UK
You don't work for Airbus do you?!
RWD3M
Forum Supporter
- Messages
- 3,543
- Location
- Wiltshire, UK
Which reminds me, My '36 Morris is a mix of metric and imperial. The engine is all metric and the gearbox has a couple of metric bearings (from the factory).
ajlelectronics
Member
- Messages
- 10,622
- Location
- Gloucester, England
The Essex is all Imperial. Bellhousing bolts are 3/8" UNC.
My 01 Caterham is a mix of metric, BSF and UNC . . .
Because our then technical manager had his eye on the US market, our new machine 20 yrs ago was designed to be all unified threads . . . apart from the bits you can't get (easily) - like THK linear slides etc.
This apparently was just after the machine shop cleared out all the number drills and unified taps as they hadn't used them much in years . . . service engineers only carried metric tools . . .
We have components with metric and unified tapped holes.
Seems crazy now as so much of the US now uses "foreign" fasteners etc - metric fasteners and tools available everywhere with no particular issues.
Morrisman
Forum Supporter
- Messages
- 8,844
- Location
- Staffordshire, England
Not on mine they weren’t. They were 10mm.
3/8” could be oversized to 10mm easily enough but I was told at the time that they were factory 10mm.
Erie Fred
Member
- Messages
- 5,816
- Location
- Erie, Pa USofA
Easy Peasy
en.wikipedia.org
Adjustable spanner - Wikipedia
