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24-Ruby IV

## Help please with cable car calculation - Prime 7 in attach

When the load is not very heavy - everything seems to be OK - see the first file. When the load is heavy, the center of gravity of the right section of the rope is in that place. Why? Send me please pictures with errors - not only Mathcad sheets!

7 REPLIES 7
24-Ruby V
(To:ValeryOchkov)

No sheet, no pic 🙂

The error simply is: In the calculation of x.gR you squared y' TWICE in the denominator!

If you remove the second exponent "2", x.gR approaches 7.5 meter with higher loads, as it should be.

BTW, your solve block fails with m=70 kg if you choose x.m smaller than 3.7 mm.

24-Ruby IV
(To:Werner_E)

Ich bedanke mich herzlich, Werner.

And why I have not solusion in the attach?

24-Ruby V
(To:ValeryOchkov)

@ValeryOchkov wrote:

Ich bedanke mich herzlich, Werner.

And why I have not solusion in the attach?

I don't know, but it doesn't seem to have to do with your initial question.

BTW, you get a  (strange) solution if you change the guess value for x.m from 5m to 3m. Guess you may want to check your equations.

24-Ruby IV
(To:Werner_E)

Thanks.

I have changed - but no solution (Prime 7).

Werner - only you can help me!

24-Ruby V
(To:ValeryOchkov)

Here is what I see in Prime 6 but I don't think that this "solution" is anywhere near useful.

I attach the file. You should be able to open it in Prime 7 and see these results as long as you don't recalcuate.

Can't help further concerning the equation check. Maybe you open a new thread as this one is about your typo problem with the wrong center of gravity.

24-Ruby IV
(To:Werner_E)

OK! I will do it!

If not solve myself.

How you open Prime 7 in Prime 6?

24-Ruby V
(To:ValeryOchkov)

How you open Prime 7 in Prime 6?

I used the procedure outlined here: https://community.ptc.com/t5/Mathcad/Prime-backwards-compatibility-solved-Or-at-least-hacked/m-p/637537/highlight/true#M188056

It doesn't work with all sheets and that depends on which new elements are used in the sheet. Its a quick and dirty method. Luc has a more sophisticated approach when it comes to making  a Prime file readable for older versions. In some threads he was able to back-convert sheets which would not work OK by simply exchanging the app.xml.
He has not published his method and I'm not sure if this is painstaking manual work where each file is handled individually, or if he has found a way to automate the procedure (at least partially).

BTW, if you open a new thread with your problem, it sure will help if you explain in detail what exactly you are trying to do and also will document the calculation steps in the file. In the past both Alan and Fred proved to be quite helpful with that kind of calculations, as far as I remember.

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