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-   -   kg per cm conversion to oz per inch (http://www.rcuniverse.com/forum/beginners-85/9130742-kg-per-cm-conversion-oz-per-inch.html)

kargo 09-28-2009 04:10 PM

kg per cm conversion to oz per inch
 
OK gang, looked on wattflyer.com but didn't have any forum topics that seemed to match my question so I'm asking here;

I'm looking at some cheaper electronics on hobbyking.com, and am trying to make some comparisons to stuff I've used in the past.
They say this servo has 1.6kg of torque, whow do I convert this to ounces per inch, which I am familiar with?

Thanks

BEAR-AvHistory 09-28-2009 04:12 PM

RE: kg per cm conversion to oz per inch
 
http://www.onlineconversion.com/

RCKen 09-28-2009 04:18 PM

RE: kg per cm conversion to oz per inch
 
Type the following into a Google search

<span style="WORD-SPACING: 0px; FONT: small arial, sans-serif; TEXT-TRANSFORM: none; COLOR: rgb(0,0,0); TEXT-INDENT: 0px; WHITE-SPACE: normal; LETTER-SPACING: normal; BORDER-COLLAPSE: separate; orphans: 2; widows: 2; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class="Apple-style-span"><span style="FONT-SIZE: 17px; WHITE-SPACE: pre; BORDER-COLLAPSE: collapse; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px" class="Apple-style-span">convert 1.6 kg per cm to oz per inch
 
Answer is:
<span style="WORD-SPACING: 0px; FONT: small arial, sans-serif; TEXT-TRANSFORM: none; COLOR: rgb(0,0,0); TEXT-INDENT: 0px; WHITE-SPACE: normal; LETTER-SPACING: normal; BORDER-COLLAPSE: separate; orphans: 2; widows: 2; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class="Apple-style-span"><span style="FONT-WEIGHT: bold; FONT-SIZE: 18px; WHITE-SPACE: nowrap; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px" class="Apple-style-span">1.6 (kg per cm) = 143.353381 oz per inch</span></span>

<font size="2">The Google search engine has some very powerful conversion tools.

Ken </font>
 

</span></span>

opjose 09-28-2009 04:25 PM

RE: kg per cm conversion to oz per inch
 
Sorry Ken, that is not right at all.

Google interprets the question incorrectly so you must avoid relyiing upon it to figure out what you mean!


I did this on paper the other day to figure out how to size some servos so I know that figure is off...

This confirms it...

http://www.linengineering.com/flash/Calculator.swf

1.6kg/cm = 22 oz/in

I was looking at 17kg/cm servos which comes out to 235 oz/in

Otherwise my 20kg/cm servos would be MIGHTY POWERFUL for their size ( standard! )

RCKen 09-28-2009 04:31 PM

RE: kg per cm conversion to oz per inch
 
OPjose,
 You know what?? You are absolutely correct. I apologize to the group for the bad info. The Google conversions usually work, but like everything else on the internet you come across bad info every now and then.

Sorry everybody.

Ken

kargo 09-28-2009 04:31 PM

RE: kg per cm conversion to oz per inch
 
Thanks RCKen and Bear,

I use google like that but when I first did the conversion that much torque out of 9 gram servo sounded a little fishy. So I looked up a servo I was familiar with and they listed the specs as this;

BMS-380MG Micro Servo (Metal Gear) 3.6kg / .15sec / 15.6g

Weight: 15.6grams / 0.55oz
Dimensions: 26 x 13 x 26 mm / 1.16 x 0.51 x 1.02 inch
Torque At 4.8V: 3.6kg/cm , 50 oz/in
Torque At 6.0V: 4.2kg/cm , 57 oz/in
Speed At 4.8V: 0.15sec / 60 deg at no load
Speed At 6.0V: 0.14sec / 60 deg at no load

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8752&Product_Name=BMS-380MG_Micro_Servo_(Metal_Gear)_3.6kg_/_.15sec_/_15.6g

Put that in the google converter you get about 322 oz per inch for 3.6kg per cm.


http://www.google.com/search?hl=en&q...&aq=f&oq=&aqi=


Maybe I'm inputting it wrong...

kargo 09-28-2009 04:33 PM

RE: kg per cm conversion to oz per inch
 
Sorry, didn't read Bear's post very well.

Allfat 09-28-2009 04:37 PM

RE: kg per cm conversion to oz per inch
 
Actually, it is not Googles fault for interpreting it incorrectly, you are in face entering in the wrong information. Torque is not ounces per inch (oz/in), it is ounces times inch (oz-in). This is for any torque, foot-pounds, kg-cm, whatever.

This being the case, I don't think google can convert this value, I think I have tried before and it just did not return a direct conversion, just websites with oz-in and kg-cm in the text. Some servos will list torque in oz-in and kg-cm, so you can get a conversion factor from any of the manufacturers or websites that list both values.

opjose 09-28-2009 04:39 PM

RE: kg per cm conversion to oz per inch
 

This does it for you: [link=http://www.linengineering.com/flash/Calculator.swf]Torque Calculator[/link]

Red B. 09-28-2009 05:08 PM

RE: kg per cm conversion to oz per inch
 
The units are wrong. Torque is the product of force and lever arm (presuming the are perpendicular to each other), not force diveded by lever arm.
For some reason most servo manufacturers continue to state torque in terms of units that are gibberish.

In the SI system the correct unit for torque is Newton times meter, i.e., Nm. Instead of meters centimeters may of course be used.
The kg is a unit for mass unit, not force. The force excerted on a 1 kg mass by the gravity of the earth is approx. 9.81 N.

As an example, a servo is that is capable of suspending a 1 kg weight using a lever arm 2,54 cm long, is producing a torque of 9.81 N times 2,54 cm = 24.92 Ncm.
If using imperial units 1 kg = 35.274 oz and 2,54 cm = 1 in and the torque will be 35.274 oz times 1 in = 35.27 oz.in.

Thus the conversion factor is 24.92/35.27 = 0,706 Ncm/oz.in. or inversely 1.415 oz.in/Ncm.

If for some reason one would like to continue using kg instead of Newton as the incorrect unit for force, the conversion factors will be 2.54/35.27 = 0.0720 kgcm/oz.in or inversely 13.89 oz.in./kgcm.

As an example 50 oz.in. = 50*0.0720 = 3.6 kgcm, or more correctly 50*0,706 = 35.3 Ncm

Allfat 09-28-2009 05:12 PM

RE: kg per cm conversion to oz per inch
 
It is not our choice to use kg-cm, despite the fact that is it technically an incorrect unit. It is the manufacturer of the servo that is giving the specs of the servo in the incorrect unit. We are just trying to figure out what that is in the standard system, not the metric system because they spec most all of our servos as oz-in, not in kg-cm.

Red B. 09-28-2009 05:20 PM

RE: kg per cm conversion to oz per inch
 
Quote:

ORIGINAL: Allfat

It is not our choice to use kg-cm, despite the fact that is it technically an incorrect unit. It is the manufacturer of the servo that is giving the specs of the servo in the incorrect unit. We are just trying to figure out what that is in the standard system, not the metric system because they spec most all of our servos as oz-in, not in kg-cm.
As I wrote in my previous post the conversion factors you are trying to figure out are 0.0720 kgcm/oz.in or inversely 13.89 oz.in./kgcm.

Two examples:
5 kgcm = 5*13.89 = 69.45 oz.in.
100 oz.in. = 100*0.0720 = 7.2 kgcm

Lnewqban 09-28-2009 08:33 PM

RE: kg per cm conversion to oz per inch
 
Red:

Your conversion factors are correct in both directions.

For long time Kg force has been used by engineers worldwide, as well as oz force and lb force in the Anglo technical world.

They are not correct, but they have been practical in mental and fast calculations.

Thus, the force that pulls a 1 Kg of mass has been called 1 Kg force, or just "1 Kg", althought it equals a force of 9.81 Newtons.

We say that we weight X pounds, in reference to the force that pulls our bodies to the ground, when in reality our bodies have a mass of X pounds.

brett65 09-28-2009 11:44 PM

RE: kg per cm conversion to oz per inch
 

Quote:

ORIGINAL: lnewqban

Red:

Your conversion factors are correct in both directions.

For long time Kg force has been used by engineers worldwide, as well as oz force and lb force in the Anglo technical world.

They are not correct, but they have been practical in mental and fast calculations.

Thus, the force that pulls a 1 Kg of mass has been called 1 Kg force, or just ''1 Kg'', althought it equals a force of 9.81 Newtons.

We say that we weight X pounds, in reference to the force that pulls our bodies to the ground, when in reality our bodies have a mass of X pounds.

Some people think that in space everything is as light as a feather because there is no gravity(actually there is microgravity). An astronaut can't just push on the shuttle and send it off course, its mass is too great. Mass is always with us and constant, same in space as it is on earth. That is unless happen to burn some mass off.:)

kargo 09-29-2009 12:14 AM

RE: kg per cm conversion to oz per inch
 
Who let the engineer types in on this conversation?:D:D Thanks for the input gang...

The Ghost 09-29-2009 02:36 AM

RE: kg per cm conversion to oz per inch
 
You can download a full Convert program [link=http://joshmadison.com/software/convert-for-windows/]HERE[/link] free. It has all of the conversions that you will ever need.

Cheers

Flight Risk 10-16-2012 01:20 PM

RE: kg per cm conversion to oz per inch
 

Quote:

ORIGINAL: Red B.
As I wrote in my previous post the conversion factors you are trying to figure out are 0.0720 kgcm/oz.in or inversely 13.89 oz.in./kgcm.

Two examples:
5 kgcm = 5*13.89 = 69.45 oz.in.
100 oz.in. = 100*0.0720 = 7.2 kgcm
Great. This is the info I need. We get used to seeing figures of about 15 oz.in. for park fliers, 40 oz.in. for standard servos, 75 oz.in. for high torque, and over 100 oz.in. for giant scale. So if we see 3.3 kg.cm. we are thrown for a loop..

So a quick and dirty conversion which is close enough for our purposes, unless you are doing scientific work, could be 1:14 or even 1:15. We generally need to only get in the same ballpark with servo strength. IMO


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