unit conversion 8

[tulum]

I don't know if I am in the right forum (just dropping in), however, need some help with a conversion.


I have a support (electrical insulator) that is good for a certain force in in.lbs (fron the data sheet). I have also calculated the force on the insulator for the given arrangement, only the result is in daN.

How do I get the units to equal?

Thanks.

 

[IRstuff]

in-lb is a torque, not a force

daN, I assume is deka-Newton(?) is a force, so they are not convertible.

TTFN

 

[FrenchCAD]

deca-Newton it is

and IRstuff told it, there is no conversion between force and torque. You should be missing something here.

Cyril Guichard
Mechanical Engineer

 

[tulum]

The situation here is I have a span length (l) of bus between 2 insulator supports (there are 5 insulators in total). The force expressed on each support is 96.3daN or 217lbf.

THe insulator is rated for 1200 in.lbs...

How do I get to these units? I relaize one is a Torque and one is a Force, however there is a length of bus involved so can I not find out the cantilever force in in.lbs?

 

[zdas04]

Either divide your torque by the bus length (in inches) or multiply your solved force by the bus length (in meters) then every engineering book in the world has a conversion from lbf to N or in-lbf to N-m.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

 

[cb68]

or alternatively use

http://www.onlineconversion.com/

 

[gearguru]

Talking about units conversions: On the link below you can download a nice, free conversion program:

http://www.joshmadison.com/software/convert/

 

[xhpipe]

Another free and dandy converter can be had at

http://www.coade.com/miscellaneous/uconvert.zip

Regards,
XHPIPE

 

[yates]

I'm not an electrical engineer but may I suggest that 1n.lbs is not a torque, but a max. allowable bending moment on your insulator. You will have to use simple mechanics to find the max. bending moment in the insulator(depends on whether the ends are cantilevered or free-swivelling)

 

[Skogsgurra]

Sigh,

Why doesn't everybody use SI?

 

[sacem1]

Because the english led the industrial revolution and their standards turned into the most published and studied all around the world (I'm sure I'm going to get beaten to death in this last statement but lets keep it there)and afterwards english language turned to the "lingua franca" in tech talk instead of the french or german who would have stablished metric sistems all around the world, so we are here stuck with to big an investment in machinery, knowledge and experience in english/american units

SACEM1

 

[arto]

More likely, we shoulda insisted that all the US tax dollars invested in rebuilding Europe/Asia after WWII, be spent on equipment with English units. Then the question would be reversed. ;-)

 

[rmw]

Notwithstanding the fact that I have to deal with several products in metric units, and actually like metric when I can use it as a stand alone system, and not have to spend my time converting back and forth, (and I wish the South Africans and the Europeans would all use the same metric system), I still hold to my motto.

"I will convert to metric when they pry my cold dead fingers off of my slide rule."

rmw

 

[rmw]

Oh, and I forgot to mention, that I do, in fact deal with european rotating machinery in some of which the torque is rated in meters-kilogram, MKg, and others in meters-deca newton, MdaN. They are just close enough to drive one nuts.

Remember the slide rule rule.

rmw

 

[gearguru]

rmw,
in metric system the units and muliplicant symbols are "case sensitive". Therefore:
M means mega
K means Kelvin
m means meter (or milli)
k means kilo

And kg is a unit of mass, not of the force, therefore m.kg is not valid unit of torque. In metric prehistoric time the kgf (kilogram of force was used in some countries. To eliminate the confusion, the unit Newton was invented. Because it is small force, sometimes the daN is used, what is almost the same force as the now illegal kgf...)
Just to confuse people little bit more...

 

[rmw]

gearguru,

You are dragging me kicking and screaming into the modern metric era. I am to old to have been taught the metric system. My children were. (the slide rule comment should be a hint)

I must have been working with technical neanderthals, (Spaniards) because they only recently converted from meter kilograms for a torque rating to meters deca newtons. Recently being in the last 10-15 years. Their product models are still based on the old mkg ratings, while the spec sheets are given in the meters daN values. I also noticed that they did everything in mm, while other systems used cm, and other units. Enough to drive me nuts.

I appreciate your post, because I did not know why the change, and was just paranoid enough to think that they did it just to confound me. I had actually gotten to where I could convert m-kgf to ft. lbs in my head. (if my memory is good, the conversion is 7.23) I am giving you a star for your help. I found it enlightening, even if I did not want to know. Next they will be wanting me to change to a metric slide rule.

Now, I wish you would straighten out the South Africans, and the Germans, so that they would settle on tonnes/hr or kg/hr, bar or kpa, W/m^2K or kW/m^2/K, etc., and make it easier on us gringos.

rmw

 

[Skogsgurra]

Sigh - and sigh again...

It seems that the one thing that "drives all of you guys nuts" is that Newton thing and that you are not allowed to use the unit for mass as a unit for force.

As you all probably know, one kilogram has the same mass wherever it is, but it does not exert the same force on the moon as it does on the earth. So it is only natural that there are different units for mass and force.

It is understandable that you pounds and inches guys are reluctant to let go he old and well-known system of yours, but I think that you should give it a try. The English managed to introduce the decimal monetary system (and the US had it from the beginning) and if you ask an English child to reckon out how many pennnies there is (was) to a guinea they will be totally lost. Multiplying 12, 20 and 21 simply is too much - and the same situation exists when doing calculations in the rest of the imperial system.

Sigh, again.

It is very illustrative to se so many references to the slide rule. We metric guys seldom need slide rules - and if we need them - we use more contemporary devices like calculators and computers. Are they not known in the imperial world? ;-)

 

[TD2K]

I like my slide rule. Every so often I pull it out, do some work with it and then go happily back to my HP 11C.

 

[rmw]

TD2K,

A client of mine remarked once not too long ago, that every once and a while he gets his slide rule out of his desk drawer, and throws it on his desk just to remind himself of who he really is.

I have adopted his practice. It is a good reality check, then I go back to my HP 28S, and hope I don't push the wrong button if my teenage children are not nearby.

Skogsgurra,

If the metric system, and the decimal money system are so great, then why not a decimal clock. Days, deca days, centi days, milli days, etc. The logic must hold.

rmw

 

[gearguru]

rmw,
thanks for the star.
Your Spaniards are an example of the inconsistency in the metric world. They obviously need skogsgurra's assistance to learn the difference between the mass and force. A lot of people has no idea about it.
I am a metric transplant into an "imperial" - an ugly word for this country (US) and I love my locally made/designed/invented HP28S, TI, PC, PDA, SUN workstation, I also still keep my old metric made slide rule, more as a collectible than a tool.
skogsgurra,
I believe it is not the system of units what makes good or bad engineers or - a country...