Dr. Fleischfresser,

After a review of your revised document submitted in response to the reviewers comments, we have decided to accept your article for publication in the Journal of Open Engineering.

Thank you for your contribution!

Devin Berg

Editor, TJOE

Dr. Fleischfresser, Thank you for your submission to the Journal of Open Engineering. Please consider the two reviews that have been completed. In particular, there are three main points that I'd like you to address. 1) While TJOE does not screen submissions on the basis of novelty or impact, both reviewers have noted that it is not clear what the main thrust of your manuscript is. Can you please clarify the main point that you are trying to make with this article? From your manuscript you address both numerical evaluation of the kinematic equations as well as the project-based engineering pedagogy. Perhaps the manuscript could be reframed to make it more clear what the implications are in one of these areas. 2) One of the reviewers noted that the notation presented in equations 1 through 3 made following the rest of the mathematics more difficult. Please consider eliminating this notation and instead writing out the trigonometric expressions fully in the subsequent equations. 3) In the numerical experiments portion of the manuscript you include some figures. In the spirit of the journal, it would be desirable to provide the code used to generate those figures as part of your submission. Thank you again for your submission and please consider the reviewer comments as well as my comments above in your revision.

1. The main thrust is the numerical evaluation of the kinematic equations and its reproducibility. The interest to develop this work originated from my daily routine of teaching vector mechanics to undergraduates, and a couple of years ago the pedagogical side of using computer projects was the main interest. But the focus is different here. 2. An argument for keeping the notation was made in my reply to the reviewer. 3. Direct link: https://doi.org/10.6084/m9.figshare.3840429.v

Corrected link: https://nuvem.utfpr.edu.br/index.php/s/CMUBxzy8fE3yMt2

REVIEW FOR THE JOURNAL OF OPEN ENGINEERING The manuscript presents an kinematics analysis of a mechanism denoted by two slender bars with a design revolution. This mechanism is a typical four-bar linkage analyzed in a wide variety of books and papers about mechanism and dynamics of machinery. Numerical simulations are performed to compare two different configurations. TECHNICAL SOUNDNESS Technical formulation seems to be correct. However, an approach using generalized coordinates or dimensionless variables might be more interesting. Some typos can be found in the paper: - vector notation: omega, V_A, V_B, ,rho_OA, rho_CB, rho_BA,.... - units in mathematical mode CLARITY It is not clear the main contribution of the manuscript: the kinematic analysis or numeric simulations? In spite of technically correct formulation of the kinematics equations, the notation and abbreviations used makes it difficult to read. It might be preferable to use throughout the manuscript the notation sin(alpha) instead l, cos(alpha) instead, and so on. It is not clear why the kinematic analysis was separated in original mechanism and modified mechanism. That seems the original mechanism is a particular configuration of the modified mechanism. Author does not explain why they employed the constant rotation w= 2 rad/s and the variable rotation w = 0,1+2,3alpha rad/s for the kinematics analysis. The selected simulated rotation constitute two really simple examples to evaluate the mechanism. It would be more appropriate to use more complex simulations. For instance, harmonic and exponential rotation. COMPLETENESS The state-of-the-art section is weak. Taking a look at the literature, it can check that there are many works about kinematics and kinetics analysis of four-bar mechanisms. The citations section is incomplete, no reference has date.

REVIEW FOR THE JOURNAL OF OPEN ENGINEERING In this paper the author derives the kinematic equations governing the four bar linkage, a common dynamics benchmark problem. The author then compares different linkage lengths and two driver input angular velocities by numerically evaluating the equations. This article is something that may belong well in an introduction to kinematics course notes, but does not really belong in a modern technical journal. The four bar linkage is one of the most common and widely studied linkages there are. There are many thousands and thousands of derivations of this out in the wild. It isn't clear to me that this derivation offers anything new to this classic problem. At the end of the article the author states "This work was motivated by the desire to introduce project-based activities in the undergraduate engineering mechanics’ classroom." This article could possibly be framed in this light and offer something useful to the journal's audience. Maybe this derivation method is an exceptional way to enlighten students and that would be worth telling a story about. But as it stands this article doesn't have a story worth telling in this journal. TECHNICAL SOUNDNESS I think this article is likely technically sound. If the author compared his results with other benchmark results of the four bar linkage then we could feel fully confident of the soundness. CLARITY The writing is fine but doesn't use common nomenclature and descriptions for kinematics. For example, it is odd that the author never mentions the phrase "four bar linkage". The introduction cites a number of frivolous references that do not seem related to the article in any substantial way. COMPLETENESS This is fine. OPENNESS AND REPRODUCIBILITY This article over presents the derivation of this common problem, which is good for reproducibility but simply showing the final kinematic equations would be more than sufficient. The author evaluates the equations numerically and it isn't apparent if software was used to do this. If it was used, there is no code or data artifact cited.

One additional comment. It is not acceptable to use copyrighted figures from a textbook in this venue.