Misunderstood terminology

General cycling advice ( NOT technical ! )
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CJ
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Re: Misunderstood terminology

Postby CJ » 3 Apr 2018, 1:38pm

rjb wrote:BBC breakfast this morning were hyping on about Porton down making Titanium. Alchemy indeed it'll be gold next week. :lol: why couldn't they say it was a new technique to refine Titanium. Give Joe public some credit for their intelligence.

I didn't believe it was even that and did a it more digging. It's actually a way of moulding parts out of powdered metal, that would otherwise be machined from solid (on lathes and milling machines). It's a process called sintering, that's commonly used for making complex-shaped parts more cheaply than they can be machined. Sturmey-Archer were making hub-gear parts that way when I worked there in the 80s. That was in bronze or steel though. The trouble with sintering a metal like titanium will be that it reacts instantly with the atmosphere to form surface oxides and nitrides; and that those oxides and nitrides, if mixed into the body of the metal, make it brittle.

So Porton Down must have invented a process for pulverising titanium and then sintering it 'in vacuo'. And whilst this may eventually be useful for dropouts and other 'weld-ons', we already have cheap enough ways of forming this expensive metal into tubes, so any hopes of a Ti frame price drop are in vain.
Chris Juden
One lady owner, never raced or jumped.

AdamS
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Re: Misunderstood terminology

Postby AdamS » 4 Apr 2018, 12:45am

Bmblbzzz wrote:
AdamS wrote:A pet peev is the bicycle trade needlessly metricising imperial measurements. It's even more infuriating where it is done inconsistently: "Ah, you'd like to buy a stem. Do you have a 1 inch headset or a 1 1/8" headset? Are your bars 25.4mm or 31.8mm?"
Tyres sizing is particularly ridiculous. What British tourists refer to as 700C, their German counterparts refer to as 28 inch!

I assume this is a result of parts, in this case stems and bars, being designed in the USA then marketed to the rest of the world. Bar diameters were already described in mm for road (26.0 and various slightly variant designs).


I suspect it's more down to the UK's former importance in bicycle manufacturing. Inch-based British Standards more often than not became international standards. The 26.0mm size is a bit of an anomoly because it is a native metric (italian) size which became the standard for nicer road bikes. Not that I ever had 26.0mm drops, mine were 15/16" and 1".

ANTONISH
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Re: Misunderstood terminology

Postby ANTONISH » 4 Apr 2018, 8:13am

AdamS wrote:
Bmblbzzz wrote:
AdamS wrote:A pet peev is the bicycle trade needlessly metricising imperial measurements. It's even more infuriating where it is done inconsistently: "Ah, you'd like to buy a stem. Do you have a 1 inch headset or a 1 1/8" headset? Are your bars 25.4mm or 31.8mm?"
Tyres sizing is particularly ridiculous. What British tourists refer to as 700C, their German counterparts refer to as 28 inch!

I assume this is a result of parts, in this case stems and bars, being designed in the USA then marketed to the rest of the world. Bar diameters were already described in mm for road (26.0 and various slightly variant designs).


I suspect it's more down to the UK's former importance in bicycle manufacturing. Inch-based British Standards more often than not became international standards. The 26.0mm size is a bit of an anomoly because it is a native metric (italian) size which became the standard for nicer road bikes. Not that I ever had 26.0mm drops, mine were 15/16" and 1".

My favourite is the Italian BB 36 x 24 ( 36mm external diameter - 24 teeth per inch )

Bmblbzzz
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Re: Misunderstood terminology

Postby Bmblbzzz » 4 Apr 2018, 10:39am

AdamS wrote:
Bmblbzzz wrote:
AdamS wrote:A pet peev is the bicycle trade needlessly metricising imperial measurements. It's even more infuriating where it is done inconsistently: "Ah, you'd like to buy a stem. Do you have a 1 inch headset or a 1 1/8" headset? Are your bars 25.4mm or 31.8mm?"
Tyres sizing is particularly ridiculous. What British tourists refer to as 700C, their German counterparts refer to as 28 inch!

I assume this is a result of parts, in this case stems and bars, being designed in the USA then marketed to the rest of the world. Bar diameters were already described in mm for road (26.0 and various slightly variant designs).


I suspect it's more down to the UK's former importance in bicycle manufacturing. Inch-based British Standards more often than not became international standards. The 26.0mm size is a bit of an anomoly because it is a native metric (italian) size which became the standard for nicer road bikes. Not that I ever had 26.0mm drops, mine were 15/16" and 1".

I was thinking of the 1-1/8" headsets, which postdate British dominance but are firmly into the era of big USA brands and gnarly mtbers.

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RickH
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Re: Misunderstood terminology

Postby RickH » 4 Apr 2018, 12:23pm

Is the latest MTB handlebar centre diameter of 35mm a shift from converted imperial sizes or is it really 1 3/8" (which would be just over 34.9mm) but called 35mm for simplicity (or confusion)?

Bmblbzzz
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Re: Misunderstood terminology

Postby Bmblbzzz » 4 Apr 2018, 1:59pm

Don't know, but I do know that at least one manufacturer (Deda) describes their bars and stems as 31.7mm rather than 31.8mm. Whether this represents nothing more than a difference in conversion/rounding or an actual difference in diameter (perhaps to make their products unique, like Cinelli used to use IIRC 26.6mm?) I do not know. Perhaps it is an actual difference in measurement but as a result of a rounding difference?

markyp
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Re: Misunderstood terminology

Postby markyp » 9 Apr 2018, 12:42pm

BigG wrote:MickF is close, but not quite right. Work is torque (or force) multiplied by distance. Power is work divided by time. These are not definitions, just indications of the calculation process.


Rotational
Torque = force × distance (N×m)
Power = Torque × angular velocity (Nm × rad/s)

(note: a radian is dimensionless, it's the ratio between the radius and the arc length. Hence, one complete revolution will be the circumference divided by the radius, i.e. 2pi

The torque×angular velocity should be borne in mind when considering crank length; e.g. pedalling approximately 3% quicker with 165mm instead of 170mm cranks will produce the same power.

Linear
Work done = force × distance (N×m, Joules)
Power = rate of work done = (force × distance)/time = Nm/s, J/s

Brucey
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Re: Misunderstood terminology

Postby Brucey » 9 Apr 2018, 2:05pm

the old cinelli size was 26.4mm

1-1/4" is exactly 31.75mm. Whether you round up to 31.8mm or down to 31.7mm is a matter or perspective or possibly convention.

1-3/8" is exactly 34.925mm. Calling it 35mm is just simpler, but I have little doubt it is actually 1-3/8" nominal size.

cheers
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Brucey
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Re: Misunderstood terminology

Postby Brucey » 9 Apr 2018, 2:17pm

ANTONISH wrote:
AdamS wrote:
Bmblbzzz wrote:I assume this is a result of parts, in this case stems and bars, being designed in the USA then marketed to the rest of the world. Bar diameters were already described in mm for road (26.0 and various slightly variant designs).


I suspect it's more down to the UK's former importance in bicycle manufacturing. Inch-based British Standards more often than not became international standards. The 26.0mm size is a bit of an anomoly because it is a native metric (italian) size which became the standard for nicer road bikes. Not that I ever had 26.0mm drops, mine were 15/16" and 1".

My favourite is the Italian BB 36 x 24 ( 36mm external diameter - 24 teeth per inch )


It is easy to forget that until sometime in the late 1970s, the UK had the biggest cycle factory in the world, ( being Raleigh in Nottingham) and one of the biggest cycle export industries. Their designs dominated world-wide, pretty much.

Fortunately the US cycle industry has had little international impact on traditional cycle parts. Their contributions to traditional bikes you might find outside the USA are mostly confined to

- the (recent i.e. in the last few decades) popularity of the 559 rim size, which MTBs inherited from cruiser bikes.
- the use of 24tpi track nuts on some coaster hubs (which causes much wailing and gnashing of teeth...)
-Ashtabula BBs in BMX bikes

However more recently you can blame lunatic US-based designers for the endless proliferation of different BB and headset designs which don't work very well and are liable to be 'here today, gone tomorrow' for the most part.

I am told that the weird Campag/Italian threading standards were as a result of the Marshall plan; the Italians received a load of US built lathes etc which would only cut US-style imperial pitch threads.

However it might well go back further than that; whitworth threads used 55 degree flanks (as found in some Italian bicycle standards) and (obviously) inch dimensions. These thread standards were the first to be properly defined (anywhere) and all nations adopted them for a while. It was difficult to buy a screw-cutting lathe that would cut anything else, for a long time. For example I have a lathe manufactured about 1890 in Germany (which sold well at the time, tens of thousands were made and sold over the world) and it uses (and cuts) whitworth screw threads. There isn't a metric dimension in it.

Arguably one reason Germany lost WW1 was that their industry didn't have properly ratified thread standards, so for example parts from standard German army rifles etc wouldn't interchange with others made to the same design but in a different factory. They each used their own ideas for thread standards; they were quite happy if their bolts fitted in their tapped holes, with little thought beyond that. Germany produced their first DIN standard for screw threads during WW1 and it was basically a straight copy of the whitworth standards, inch dimensions and all. Obviously anything designed in Germany before that wouldn't necessarily have used any standard.

cheers
Last edited by Brucey on 9 Apr 2018, 2:37pm, edited 3 times in total.
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Bmblbzzz
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Re: Misunderstood terminology

Postby Bmblbzzz » 9 Apr 2018, 2:22pm

A propos uniqueness (but not misunderstandings), an advantage of 31.8mm or 31.7mm or 1-3/8" bar clamp size is that at last the same steerers fit both flat and drop bars. Whether this is enough of an advantage to outweigh the complication of them not fitting 26.0 or 25.4, I will leave to the reader's decision. Though at least, so far, it's common to all manufacturers.

Bmblbzzz
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Re: Misunderstood terminology

Postby Bmblbzzz » 9 Apr 2018, 2:29pm

US or UK influence: I'm pretty sure things like 559 rims on MTBs can be described as traditional by now!

I'm pretty sure the 31.8mm bar size originated in the US, for mtbs first before reaching road stuff.

But all those bottom bracket designs that have proliferated over the last decade or so - I think there are far too many of them for any to have gained the status of a standard in other than the technical sense!

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Re: Misunderstood terminology

Postby MikeF » 9 Apr 2018, 11:09pm

markyp wrote:
BigG wrote:MickF is close, but not quite right. Work is torque (or force) multiplied by distance. Power is work divided by time. These are not definitions, just indications of the calculation process.


Rotational
Torque = force × distance (N×m)
Power = Torque × angular velocity (Nm × rad/s)

(note: a radian is dimensionless, it's the ratio between the radius and the arc length. Hence, one complete revolution will be the circumference divided by the radius, i.e. 2pi

The torque×angular velocity should be borne in mind when considering crank length; e.g. pedalling approximately 3% quicker with 165mm instead of 170mm cranks will produce the same power.

Linear
Work done = force × distance (N×m, Joules)
Power = rate of work done = (force × distance)/time = Nm/s, J/s

And Torque is lbs ft and Work done is ft lbs :wink:
"It takes a genius to spot the obvious" - my old physics master