Unit madness

[AW111]

I am involved in the Dyno industry.
Even in Australia, where we are notionally metric, people want

Boost - PSI
Manifold vacuum - Inches (of mercury)
Power - kW or Hp
Torque - ftlb or Nm
Speed - kph
Air temperature - degrees C
Exhaust temperature - degrees F

Bikes want power in ps (hp), but torque in kgm!


????

[ging84]

AW111 said:

I am involved in the Dyno industry.
Even in Australia, where we are notionally metric, people want

Boost - PSI
Manifold vacuum - Inches (of mercury)
Power - kW or Hp
Torque - ftlb or Nm
Speed - kph
Air temperature - degrees C
Exhaust temperature - degrees F

Bikes want power in ps (hp), but torque in kgm!


????

on a dyno
do they need a unit for a speed of 0 ?

[357RS]

In the Dyno industry I'd expect you to know that ftlb is not a unit of torque.

[TheEnd]

ging84 said:

on a dyno
do they need a unit for a speed of 0 ?

There's a few places around the world where dynos are done vs road speed instead of engine rpm.
I guess calibrating the rollers to an engine speed is too much hard work.

[NorthernBoy]

357RS said:

In the Dyno industry I'd expect you to know that ftlb is not a unit of torque.

I'm not sure what point you are trying to make there. Foot pound is definitely a unit of torque, do you just not like how he wrote his abbreviation?

That's to say, were you being a spelling pedant, or are you saying that foot pounds is not a measure of torque?

[AndyS2]

NorthernBoy said:

357RS said:

In the Dyno industry I'd expect you to know that ftlb is not a unit of torque.

I'm not sure what point you are trying to make there. Foot pound is definitely a unit of torque, do you just not like how he wrote his abbreviation?

That's to say, were you being a spelling pedant, or are you saying that foot pounds is not a measure of torque?

Look it up, every day's a school day!

[xyyman]

Harking back to my student days then, if I recall correctly, the term ft/lb is used as a measure of work and lb/ft a measure of torque. Although I do recall that the two are quite often, and acceptably, interchangeable as a measure of torque. Look up any industry accepted torque table to establish that. I suppose that a pedant of the nth degree may find that somewhat unpalatable. Ah well, back to sleep now.

[alephnull]

357RS said:

In the Dyno industry I'd expect you to know that ftlb is not a unit of torque.

Is this some desperate point about ft lbs assuming Earth gravity? Wow.

[littleredrooster]

xyyman said:

Harking back to my student days then, if I recall correctly, the term ft/lb is used as a measure of work and lb/ft a measure of torque.

You memory is playing tricks, then. It can never be feet per pound, or pounds per feet the way you have indicated. One is multiplied by the other, not divided.

[littleredrooster]

357RS said:

In the Dyno industry I'd expect you to know that ftlb is not a unit of torque.

Go on then - tell us more. ftlb - or more accurately lbs-ft - was always a measure of torque when I did my engineering qualifications. Might have changed since 1971, I suppose...

[GroundEffect]

AW111 said:

I am involved in the Dyno industry.
Even in Australia, where we are notionally metric, people want

Boost - PSI
Manifold vacuum - Inches (of mercury)
Power - kW or Hp
Torque - ftlb or Nm
Speed - kph
Air temperature - degrees C
Exhaust temperature - degrees F

Bikes want power in ps (hp), but torque in kgm!


????

Air in C but Exhaust in F? fk them.

Also PS is metric horsepower.

[AW111]

GroundEffect said:

Air in C but Exhaust in F? fk them.

Also PS is metric horsepower.

I think people want exhaust in F because of all the US data.

Horsepower :
1 imperial (mechanical) horsepower is 745.7 watts.
1 ps (metric) horsepower is 735.5 watts.

Figures from t'internet, because I am not at work, but they seem right.
http://www.princeton.edu/~achaney/tmve/wiki100k/do...


So kids, always quote your power in ps, because you get a bigger number (about 1% higher) !
Use "boiler horsepower" if you really want to confuse people.

[Negative Creep]

I can't understand why wheels are measures in inches but tyre diameter is always in millimetres?

[GroundEffect]

AW111 said:

GroundEffect said:

Air in C but Exhaust in F? fk them.

Also PS is metric horsepower.

I think people want exhaust in F because of all the US data.

Horsepower :
1 imperial (mechanical) horsepower is 745.7 watts.
1 ps (metric) horsepower is 735.5 watts.

Figures from t'internet, because I am not at work, but they seem right.
http://www.princeton.edu/~achaney/tmve/wiki100k/do...


So kids, always quote your power in ps, because you get a bigger number (about 1% higher) !
Use "boiler horsepower" if you really want to confuse people.

At work we only use PS for tractive power, Nm for torque and kW for heat rejection...my US colleagues like to use PS, lb.ft and BTUs. That helps....

[littleredrooster]

Negative Creep said:

I can't understand why wheels are measures in inches but tyre diameter is always in millimetres?

It isn't. It's the width which is metric, not the diameter.





Unless you have a BMW with metric rims, in which case they're all metric.

[Negative Creep]

littleredrooster said:

Negative Creep said:

I can't understand why wheels are measures in inches but tyre diameter is always in millimetres?

It isn't. It's the width which is metric, not the diameter.





Unless you have a BMW with metric rims, in which case they're all metric.

A yes, that's what I meant to say. As far as I know wheels are measured in inches all over the world?

[Evoluzione]

Negative Creep said:

littleredrooster said:

Negative Creep said:

I can't understand why wheels are measures in inches but tyre diameter is always in millimetres?

It isn't. It's the width which is metric, not the diameter.





Unless you have a BMW with metric rims, in which case they're all metric.

A yes, that's what I meant to say. As far as I know wheels are measured in inches all over the world?

Michelin did a metric tyre called the TRX, it didn't fit imperial rims, they were fitted to not only (as the chap says) BMWs, but Alfa actually produced the same model car with an imperial and metric rim! The metric (340mm) would only take a TRX (which was seemingly made of plastic), but the same style of wheel was also available in 14" which would take any tyre.

[Benrad]

Radical make their cars with a mix of imperial and metric bolts! Working for an American company in the UK in engineering makes inter continental communication fun (I too am in engine testing with dynos but I develop the engines before they're fitted). They use a very eclectic mix of units, particularly temperatures

[Evoluzione]

AW111 said:

I am involved in the Dyno industry.
Even in Australia, where we are notionally metric, people want

Boost - PSI
Manifold vacuum - Inches (of mercury)
Power - kW or Hp
Torque - ftlb or Nm
Speed - kph
Air temperature - degrees C
Exhaust temperature - degrees F

Bikes want power in ps (hp), but torque in kgm!


????

I feel your pain, the global measurement system is a big mess.
I was recently quoted some power figures from a chap in Norway, they use BHP and NM on their engine dynos.
We've been Metric since 1971, but still use a mish mash of both. I have no idea what 'a thou' is, any engineer over the age of 45ish will take a metric measurement and convert it to imperial.

There should have been a complete ban on imperial at a certain point in time, trying to change it gradually over so many years has resulted in lots of problems and massive expense.

The Meercans don't have any idea what metric is at all, but then that's no surprise, most of them don't even realise there is anything beyond the Pacific and Atlantic Oceans....

[Johnnytheboy]

In my industry (indoor plants), many plant pots are given product names based on the range name, then the size.

So for example a basic round pot 45cm in diameter and 40cm deep is called a R45/40.

A few years ago we bought another company and found that in all their paperwork the code was based on the diameter in inches, but the height in centimetres, e.g. the example I gave would be a R18/40.

Even for a family firm of crazy religious people, that was pretty strange.