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EL_99808601-Visitor
1-Visitor
February 28, 2022
Solved

HELP: units do not match

  • February 28, 2022
  • 3 replies
  • 3654 views

I am having difficulty figuring out what is wrong with my worksheet. This worksheet is a design calculation of spur gear. My problem is that addendum, dedendum, and clearance units are in 1/in, which is wrong. Why is it that the units are in reciprocal form? Is there any solution for this?. The goal is that the addendum, dedendum, and clearance must be in plain mm or in. Hoping someone can help me. Thanks

Best answer by StuartBruff
@EL_9980860 wrote:

Hi, it is from a textbook we are currently using for the Machine Elements subject by Myzka. Both the 1 and 1.25 are unitless, so how will I define it as unitless? My second question is, If there is a chance that both were defined as unitless, will the answer be in inches?

As Chris and Valery have mentioned, diametral pitch should have units of teeth per inch.   Your Mathcad expressions should then automatically calculate the correct units for the addendum and dedendum (inch).  I think the image below shows what you should get, but my knowledge of gear design is limited to what the internet showed me in a couple of minutes.

 

StuartBruff_0-1646207887606.png

 

Stuart

 

(Revised Mathcad 7 Express worksheet attached)

3 replies

S
StuartBruff23-Emerald V
23-Emerald V
February 28, 2022
@EL_9980860 wrote:

I am having difficulty figuring out what is wrong with my worksheet. This worksheet is a design calculation of spur gear. My problem is that addendum, dedendum, and clearance units are in 1/in, which is wrong. Why is it that the units are in reciprocal form? Is there any solution for this?. The goal is that the addendum, dedendum, and clearance must be in plain mm or in. Hoping someone can help me. Thanks

Where do you get your addendum and dedendum definitions from? 

 

Mathcad will generate the appropriate units for your expressions and if the units (dimensions) are wrong then there is something wrong with the expressions.  You have defined the addendum and dedendum as reciprocals of the diametrical pitch (in), so the units are bound to be 1/in.

 

Stuart

E
EL_99808601-VisitorAuthor
1-Visitor
March 2, 2022

Hi, it is from a textbook we are currently using for the Machine Elements subject by Myzka. Both the 1 and 1.25 are unitless, so how will I define it as unitless? My second question is, If there is a chance that both were defined as unitless, will the answer be in inches?

S
StuartBruff23-Emerald VAnswer
23-Emerald V
March 2, 2022
@EL_9980860 wrote:

Hi, it is from a textbook we are currently using for the Machine Elements subject by Myzka. Both the 1 and 1.25 are unitless, so how will I define it as unitless? My second question is, If there is a chance that both were defined as unitless, will the answer be in inches?

As Chris and Valery have mentioned, diametral pitch should have units of teeth per inch.   Your Mathcad expressions should then automatically calculate the correct units for the addendum and dedendum (inch).  I think the image below shows what you should get, but my knowledge of gear design is limited to what the internet showed me in a couple of minutes.

 

StuartBruff_0-1646207887606.png

 

Stuart

 

(Revised Mathcad 7 Express worksheet attached)

    C
    ChrisKaswer16-Pearl
    16-Pearl
    February 28, 2022

    Diametral pitch is a number representing how many teeth per inch (or mm) of pitch diameter you have in the gear (# teeth/pitch diameter). When you make this adjustment in your units (1/in), you will have the correct answers.

     

    Cheers

    E
    EL_99808601-VisitorAuthor
    1-Visitor
    March 2, 2022

    What are those adjustments, then? Can you show me those? Thanks!

    V
    24-Ruby IV
    ValeryOchkov24-Ruby IV
    24-Ruby IV
    March 2, 2022

    There is a lot errors in print texts!

    V
    24-Ruby IV
    ValeryOchkov24-Ruby IV
    24-Ruby IV
    February 28, 2022

    ValeryOchkov_1-1646072021363.png

     

    E
    EL_99808601-VisitorAuthor
    1-Visitor
    March 2, 2022

    Thanks for pointing it out. However, I am asking for a solution on the reciprocal form units of the addendum, dedendum, and clearance. Hoping you can help me.

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