Method for Theoretical Assessment of Safety against Derailment of New Freight Wagons

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The presented method is interesting, but highly theoretical. In practice, safety against derailment is strongly influenced by the way the wheelset is guided, affecting primarily the transverse and longitudinal stiffness of the elements of primary suspension. Resulting stiffness and damping of the primary suspension affects the ability of a rail vehicle to safely overcome curves and run on twisted track. Those aspects are taken into account in dynamic, multibody simulations of rail vehciels dynamics.

The authors should indicate in more detail the simplifications of the presented method and indicate their impact on the results in relation to a real vehicle. As I understood, it is a geometrical method, without taking itno consoderation any defection of suspension elements in any direction.

Author Response

Dear reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses in attached file and the corresponding revisions/corrections highlighted in the re-submitted file.

Kind regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1.     Abstract didn’t hit the key point of the paper.

2.     Table 1, please correct the radius range using “-”.

3.     The results from the experiments need to be compared and expressed intuitively, either in plots or in tables. The difference between the theoretical values and experiment data needs to be explained. 

4.     The final part of the paper should be conclusions, instead of discussions. 

Comments on the Quality of English Language

OK

Author Response

Dear reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses in attached file and the corresponding revisions/corrections highlighted in the re-submitted file.

Kind regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The main idea behind the presented research is to propose a theoretical method to simplify the assessment of safety against derailment of freight wagons. The article presents a description of the proposed method, which involves the calculation of several parameters related to the wagon's wheels and test track interaction. Unfortunately there are several issues related to the methodology and presentation, in my opinion the article is not ready for publication. The experimental verification of the presented theoretical calculations related to safety is not detailed enough. Moreover, it is not clear whether the authors carried out their own verification or whether they only refer to the final results reported elsewhere. Theoretical calculations are questionable, e.g. the lateral forces Y should include friction forces, but the friction forces are presented separately, even without taking into account the contact angle (eq.8, eq.10).                                                    

Comments on the Quality of English Language

In my opinion linguistic correctness is acceptable.

Author Response

Dear reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses in attached file and the corresponding revisions/corrections highlighted in the re-submitted file.

Kind regards

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors, the topic of the manuscript is relevant and of interest to specialists. Some recommendations:

1) The name of the manuscript - I suggest clarifying "new freight wagons"

2) in my opinion, known methods should be described more in the Introduction

3) Introduction, References - add literary sources. Pay attention to modern (2021, 2022, 2023 years)

4) "Figure 9" - bogie standard? or new too?

5) "In this paper we show that proposed methodology for calculation of safety against

derailment gives good results ..." this statement is made on the basis of what? Add graphs and describe them. Compare the results.

6) "This gives reason to claim that the proposed theoretical..." must be substantiated

kind regards,

Author Response

Dear reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses in the attached file and the corresponding revisions/corrections highlighted in the re-submitted file.

 

Kind regards

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

OK to publish.

 

One suggestion, (and this might be affected by the journal format), is that, take Table 3 as example, it may be better to write -14.042 kN instead of -14,042 kN. 

Author Response

Dear reviewer,

thank you for your comments and suggestions. Please, find our responses in attached file. 

Kind regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

My comments to the revised version of the submitted manuscript:

1. Row 135; point M is not the "instantaneous center of rotation". Its velocity is not equal to zero.
2. Row 190 / Equation 10; If the Y variable is the total lateral wheel-rail force then Y=N*sin(d)+T_y*cos(d), where N is normal force, d is contact angle, T_y is lateral creep force (friction force) and T_y << u*N, where u is static friction coeff. I can't see how the equation 10 relates to those forces, moreover the assumption that friction (?) Phi=u*N is not supported. The theoretical part should be explained in more detail and all the assumptions should be presented explicitly.
3. Why the friction forces (?) Phi1 and Phi2 are perpendicular to the vectors r1 and r2 ?
4. It is necessary to show the experimental Y and Q forces in the form of a time plot and not only one value for the particular instant of time.

Comments on the Quality of English Language

In my opinion linguistic correctness is acceptable.

Author Response

Dear reviewer,

thank you for your comments and suggestions. Please, find our responses in attached file. 

Kind regards

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors, 

1) The Title of the manuscript - I suggest clarifying "new freight wagons"

Author Response

Dear reviewer,

thank you for your comments and suggestions. Please, find our responses in attached file. 

Kind regards

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,
In my opinion there are still some aspects of the article that need further clarification, the essential ones are the calculation of lateral "Y" and friction forces "Phi", I think I didn't get satisfactory answer to my previous comment number 2. I have rephrased my comment below:
Row 190: "Total reactions Y" means that lateral "Y" force include all the lateral components of wheel-rail forces including friction forces but we see the friction forces "Phi" appear in equation (10) separately from "Y" which is a contraddiction. Whatsmore you assume the frictional forces at every wheel
have the same value Phi_y. How can this be reconciled with the fact that the outer wheel in contact with the rail (possible flange contact) has completely different contact and slip conditions than the inner wheel, and the equivalent dynamic friction coefficient of the inner wheel is much smaller than the assumed static friction of 0.4?
Row 104,324: In the formulas (1) and (29) there are multiple equality/inequality symbols, while in a mathematical equation there should be only one equality
symbol placed between left-hand side and right-hand side of the equation.
Row 172: "force from the mass of the wagon" -> weight,
Row 173: "ground acceleration" -> gravitational acceleration.
If you assume vehicle translation velocity equal to zero then we have pure rotation about the axis at point M which still is not "instantenous centre of rotation". I would suggest just using "centre of rotation" term.

Comments on the Quality of English Language

Linguistic part is acceptable.

Author Response

Dear reviewer,

please find our responses to your comments and suggestions in attached file.

Kind regards

Author Response File: Author Response.pdf