Design and Test of a New Type of Overrunning Clutch
Round 1
Reviewer 1 Report
The paper deals with a very interesting subject. Overrunning clutches are widely used in machines and a new type is presented in the paper. The paper needs major improvements before publication.
The idea is to replace the roller in a common overrunning clutch by a part with a double arc geometry. In the paper, this new part is called ‘double arc roller’. Unfortunately, due to its particular geometry, the part is no more able to roll but slides in the mechanism. The name should be changed to be more accurate, ‘double arc sprag’ or ‘double arc slider’ could appear as more appropriated.
The text contains many mistyping errors that have to be corrected, here are some examples:
P2 line 70: ‘Che[21]’ should be ‘Che [21]’
P2 line 94: ‘SOC[26]’ should be ‘SOC [26]’
P3 line 108: the text should be ‘This also declines the contact stress and increases torsion stiffness in application’
P3 line 114: replace ‘A point’ by ‘point A’
P5 line 179: add unit ‘2, 3, 4, 5, 6 mm’
Table1: the SOC contains 15 sprags (see Figure 9), not 16
Table 2: use ‘MPa’ instead of ‘Mpa’
DOI of the papers in the references should be provided.
Overrunning clutch can be also refered to as freewheel : ‘freewheel’ could be added in the keywords and in the abstract to enhanced the referencing process.
Figure 2 presents a mechanical model in a state that is never used in the paper and should be simplified. To study the bonding condition the equilibrium is opportunely simplified with only contact forces in point A and B. Doing so, the part is in equilibrium with only 2 loads. A basic mechanical analysis directly conducts to conclude that the loads are directly opposite and oriented in line AB. Thus the final equations are obtained very quickly.
Moreover p4 line 156, the sliding friction values are false. The presented self-locking angle is 11.4° when the friction coefficient is 0.1.
The overrunning condition of the system is a key issue. In its state, the text is too unclear.
Figure 3 presents a static state with loads that are not consistent with equation 6. Moreover, the text explains that forces at point A can be omitted. It is not true when the system is self-locked.
Figure 5 presents homothetic figures. There is no interest in presented each configuration separately, one drawing should be enough.
As a consequence, Chapter 2.2 needs to be rewritten.
Loads in figure 7 could be simplified in point A and B as in figure 2.
The contact stress comparison should also be simplified. Indeed, it has been previously established that loads in A and B are equals.
P10 line 309: the text may be ‘The outer diameter, inner diameter and thickness of the inner ring’
Equation 20 needs to be corrected to have consistent symbols, for point A: include (R-r)/(Rr)
Equation 31 should also be corrected. At point B ‘=’ is missing.
The choice of r1 and r2 values for the DAROC example is not explained.
In this study, contact stress in point A is presented but not exploited. The proposed approach only considers a comparison dealing with contact stresses. Considering only this point of view would lead to consider r1 equal to R and r2 as infinite. If such designs are inappropriate, then the limiting factors should be established and considered in the study to explain the choices for r1 and r2. At least, the self-locking condition should be clearly explained and considered.
The interest of high r1 and r2 values is clear to decrease the contact stresses. This is a common remark with r21 and r22 in SOC. The authors may investigate the limiting factors of r21 and r22 in SOC and apply them in this study. This will enable a fair comparison between the mechanisms.
The experimental chapter is very interesting and well presented. It shows the potential interest of the new proposed design with a high torsional stiffness.
Author Response
Response to Reviewer #1
Dear Reviewer,
We would like to express our sincere appreciation for your careful reading and invaluable comments to improve this paper. We have addressed all issues raised by the reviewer. The amendments made are mentioned below with reference to appropriate paragraphs and sections of the revised manuscript. Revised portions are marked in red in the paper. If other reviewer mentioned the same error, it will be highlighted in other color.
[Overall Comment] The paper deals with a very interesting subject. Overrunning clutches are widely used in machines and a new type is presented in the paper. The paper needs major improvements before publication.
[Answer] Thank you for your carefully reading of our manuscript. We are honored to receive thoughtful, detailed and valuable comments, which help us greatly improve the manuscript. We have made revisions to our manuscript in light of the reviewer’s comments one by one.
[Comment 1] The idea is to replace the roller in a common overrunning clutch by a part with a double arc geometry. In the paper, this new part is called ‘double arc roller’. Unfortunately, due to its particular geometry, the part is no more able to roll but slides in the mechanism. The name should be changed to be more accurate, ‘double arc sprag’ or ‘double arc slider’ could appear as more appropriated.
[Answer] Thank you a lot for pointing this out. The double-arc geometry can realize the bonding condition and overrunning condition by the clockwise or counter clockwise rotation tendency, that’s why we called it a ‘roller’ at first. However, this geometry will not actually rotate in most occasion. So, the double arc sprag is more suitable for this work. We have replaced all the ‘double arc roller’ into ‘double arc sprag’ and all abbreviations are replaced as ‘DASOC’ at the same time.
[Comment 2] The text contains many mistyping errors that have to be corrected, here are some examples:
P2 line 70: ‘Che[21]’ should be ‘Che [21]’
P2 line 94: ‘SOC[26]’ should be ‘SOC [26]’
P3 line 108: the text should be ‘This also declines the contact stress and increases torsion stiffness in application’
P3 line 114: replace ‘A point’ by ‘point A’
P5 line 179: add unit ‘2, 3, 4, 5, 6 mm’
Table1: the SOC contains 15 sprags (see Figure 9), not 16
Table 2: use ‘MPa’ instead of ‘Mpa’
[Answer] Thank you for your carefully reading, and I feel sorry about the mistyping and errors in the manuscript, which have bad impressions with our work. Actually, not only in this comment, there are other some mistyping errors appeared even caused misleading and inaccurate about this paper. So, we carefully check our work again and try our best to minimize the mistyping errors in this paper. All the errors mentioned are corrected.
[Comment 3] DOI of the papers in the references should be provided.
[Answer] Thank you for your advice. We have tried out best to provide the DOI of the papers in the references. However, some of the references are written in Chinese or dissertations or patents, which are without DOI.
[Comment 4] Overrunning clutch can be also refered to as freewheel : ‘freewheel’ could be added in the keywords and in the abstract to enhanced the referencing process.
[Answer] Thanks for your advices for the object which we studied. In fact, we founded the freewheel related papers at first, but it makes us confused that both one of the energy storage parts and the overrunning clutch called freewheel. We checked the Chinese-English terminology translation website (The website is at the end of this paragraph) and finally determined the translation is ‘overrunning clutch’. Due to the ‘Freewheel’ can also be referred, we decide to adopt your advice and add the word ‘Freewheel’ in abstract and keywords. To avoid duplicate with title, the ‘overrunning clutch’ in keyword is moved out.
https://www.termonline.cn/search?k=%E8%B6%85%E8%B6%8A%E7%A6%BB%E5%90%88%E5%99%A8&r=1666232891643
[Comment 4] Figure 2 presents a mechanical model in a state that is never used in the paper and should be simplified. To study the bonding condition the equilibrium is opportunely simplified with only contact forces in point A and B. Doing so, the part is in equilibrium with only 2 loads. A basic mechanical analysis directly conducts to conclude that the loads are directly opposite and oriented in line AB. Thus the final equations are obtained very quickly.
[Answer] Thanks for your suggestion about the figure. It is, indeed, too complicated and much information in figure 2, and the contact forces can also be conducted by using the static equilibrium at A and B nodes with only 2 loads. So, we simplify the figure 2. In the new figure 2, the rotation direction is presented to show the two working conditions. The redundancy parameters are deleted and the figure are separated in two subpictures which show the geometry and static mechanism under overrunning conditions. We wish this figure can improve the presentation ability and explain the two working conditions well.
[Comment 5] Moreover p4 line 156, the sliding friction values are false. The presented self-locking angle is 11.4° when the friction coefficient is 0.1. The overrunning condition of the system is a key issue. In its state, the text is too unclear. Figure 3 presents a static state with loads that are not consistent with equation 6. Moreover, the text explains that forces at point A can be omitted. It is not true when the system is self-locked. Figure 5 presents homothetic figures. There is no interest in presented each configuration separately, one drawing should be enough. As a consequence, Chapter 2.2 needs to be rewritten.
[Answer] Thank you for pointing out our mistake in friction coefficient. The friction coefficient is truly 0.1 when self-locking angle is 11.4°, and it is hard for a kind of material to get the sliding coefficient at 1. The mistake is made by another mistyping and we felt sorry for the mistyping errors. We have double checked and corrected these mistakes.
We are sorry for the unclear of the overrunning condition and we find that there may be a similar problem in the bonding condition. So we explain both two condition at the beginning of the section 2 and take an example of the motorcycle downhill problems. It is a classic example in overrunning clutch usage. The torque transmission are cut when the angular speed of driven shaft is higher than driving shaft and the torque transmission will be recovered when the angular speed drops. The correction of figure 2 also shows the two working conditions in different relative rotation direction. We think this will be better to make the explanation of two working conditions especially overrunning conditions more clearly.
We feel sorry for the mistake in the Eqs, and we have revised the formula and given the correct results of subsequent discussion
Figure 5 is redundancy and homothetic, the key parameters are mentioned in figure 3. We delete the figure 5 and replace with Table.1. In this table, the minimum effective length of double arc sprag is given and the parameters in Table are appeared in figure 3. This may be better to present the relationship between virtual radius and l1.
[Comment 6] Loads in figure 7 could be simplified in point A and B as in figure 2.
[Answer] Thanks for giving us the advice in figure7. We simplify the figure 7 by separating the static mechanism and geometry. Figure 7 now are disassembly into 6 pictures, which makes the whole picture clear and specific.
[Comment 7] The contact stress comparison should also be simplified. Indeed, it has been previously established that loads in A and B are equals.
[Answer] Thank you for your advice. Firstly, it is true that the loads in A and B are equal in three overrunning clutches. However, the number of roller/sprag of the three overrunning clutches are different. This will leads to the different forces on the the roller/sprag of different overruning clutches, even though they are under the same torque.
[Comment 8] P10 line 309: the text may be ‘The outer diameter, inner diameter and thickness of the inner ring’
[Answer] Thanks for your correction. We changed the text to ‘The outer diameter, inner diameter and thickness of the inner ring’
[Comment 9] Equation 20 needs to be corrected to have consistent symbols, for point A: include (R-r)/(Rr)
[Answer] Thanks for your correction. We changed the symbol to (R-r)/(Rr)
[Comment 10] Equation 31 should also be corrected. At point B ‘=’ is missing.
[Answer] Thanks for your correction. We supplemented a ‘=’ at Eq.31.
[Comment 11] The choice of r1 and r2 values for the DAROC example is not explained. In this study, contact stress in point A is presented but not exploited. The proposed approach only considers a comparison dealing with contact stresses. Considering only this point of view would lead to consider r1 equal to R and r2 as infinite. If such designs are inappropriate, then the limiting factors should be established and considered in the study to explain the choices for r1 and r2. At least, the self-locking condition should be clearly explained and considered.
The interest of high r1 and r2 values is clear to decrease the contact stresses. This is a common remark with r21 and r22 in SOC. The authors may investigate the limiting factors of r21 and r22 in SOC and apply them in this study. This will enable a fair comparison between the mechanisms.
[Answer] Thanks for your suggestion. Firstly, we can get that the range of r1 is from r to R, but can not be equal to R; and the range of r2 is from r to infinity. This is because when r1=r2=r, the overrunning clutch proposed in the paper has no difference in performance with the traditional roller overrunning clutch, and therefore the improvement of the slider is of little significance. Secondly, in terms of rigid body kinematics, when r1 approaches to R, r2 approaches to infinity, the overrunning clutch can form the engagement condition. However, in terms of elastic mechanics, if r1 is equal to R and r2 tends to be infinite, this may cause the overrunning clutch to be deformed and unable to lock itself. I am sorry that at present we have not conducted in-depth research on the upper bound of r1 and r2. In this paper, the values of r1=7.5mm and r2=10mm are obtained by experience. Actually, the values of r1 and r2 can be larger than the data given in this paper.
[Comment 12] The experimental chapter is very interesting and well presented. It shows the potential interest of the new proposed design with a high torsional stiffness.
[Answer] Thank you very much for your helpful and valuable suggestions. The high torsional stiffness is another key issue to evaluate the loading capacity of an overrunning clutch. In this aspect, DASOC can perform much better than normal ROCs due to the larger radius of double arc. This is the future work that we will discussed.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is generally very interesting. However, it needs some revisions before it can be accepted for publication.
Row 70 Space missing “Zhang[5]”
Row 71 Space missing “Che[21]”
Row 94 Space missing “SOC[26]”
Row 158 Space missing “11.4owhen”
Row 159 Spaces missing “7.5oto 8.5oin”
Row 188 Spaces missing “ 2,3,4,5,6”
Row 232 Space missing “stress[27]is”
Row 239 Space missing “2.06x1011Pa”
Row 249 Please change with “Fig.6 shows a schematic diagram the 3D model”
Row 267 Remove upper case for references “ROC[10,11]” and leave a space.
Row 279 Remove the point in the middle of the sentence “can be obtained. as shown in Eq.21” or start with a capital letter „can be obtained. As shown in Eq.21”
Row 281 „are the ratios” instead „are the ratio”
Row 292 Replace the point after Eq23 with „Eq.23, where”
Row 296 “r21 and r22 are the radii (or radiuses)”
Row 300 Replace the point after „obtained.” with „obtained, as shown”
Rows 309 and 310 Leave blank space between numerical values and units “52mm” to “52 mm”
Rows 321 and 322 Leave blank space between numerical values and units “6210.1N” to “6210.1 N”
Row 329 and 322 Leave blank space between numerical values and units “95Nm” to “95 Nm”
Row 331 Title of the table must be on the next page with table 3
Row 341 Remove “and” in “ the materials and of the”. At the end of this sentence, it would be better to say “are all heat treated having a hardness of 55-60 HRC.” Also it would be interesting to mention the type of heat treatment applied.
Row 342 “ The material of the spring is rubber” and “ the geometrical parameter is presented in Table.1.” or “ The geometrical parameters are presented in Table.1.”
Row 343 “shows the structure of DAROC in before and after”
Row 348 “ The experiment begins with”
Row 359 Leave blank space between numerical values and units “95Nm”
Row 381 Please delete the point at the start row (put it at the end of the previous row)
Row 386 Please change “Eq.32.” with “Eq.27.”
Row 389 Please change “Eq.33.” with “Eq.28.”
Row 404 Change „ The average torsion stiffness can be calculated in Table.6” with „The values of the average torsion stiffness are presented in Table.6.”
Row 408 Please change “Fig.11” with „Figure 11”
Row 410 Add „ .” - Table.6
Author Response
Response to Reviewer #2
Dear Reviewer,
We would like to express our sincere appreciation for your careful reading and invaluable comments to improve this paper. We have addressed all issues raised by the reviewer. The amendments made are mentioned below with reference to appropriate paragraphs and sections of the revised manuscript. Revised portions are marked in blue in the paper. If other reviewer mentioned the same error, it will be highlighted in blue.
[Overall Comment] The manuscript is generally very interesting. However, it needs some revisions before it can be accepted for publication.
[Answer] Thank you for your carefully reading of our manuscript. We are honored to receive thoughtful, detailed and valuable comments, which help us greatly improve the manuscript. We have made revisions to our manuscript in light of the reviewer’s comments one by one.
[Comment 1] Row 70 Space missing “Zhang[5]”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 2] Row 71 Space missing “Che[21]”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 3] Row 94 Space missing “SOC[26]”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 4] Row 158 Space missing “11.4 when”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 5] Row 159 Spaces missing “7.5 to 8.5 in”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 6] Row 188 Spaces missing “2,3,4,5,6”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 7] Row 232 Space missing “stress[27]is”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 8] Row 239 Space missing “2.06x1011Pa”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 9] Row 249 Please change with “Fig.6 shows a schematic diagram the 3D model”
[Answer] Thanks for your correction. We changed the sentence with “Fig.6 shows a schematic diagram of the 3D model of three overrunning clutches”
[Comment 10] Row 267 Remove upper case for references “ROC[10,11]” and leave a space.
[Answer] Thanks for your correction. We removed the upper case for reference and changed with normal size reference and leave a space.
[Comment 11] Row 279 Remove the point in the middle of the sentence “can be obtained. as shown in Eq.2 1” or start with a capital letter “can be obtained. As shown in Eq.21”
[Answer] Thanks for your correction. We removed the point in the middle of the sentence.
[Comment 12] Row 281 “are the ratios” instead “are the ratio”
[Answer] Thanks for your correction. We changed “are the ratio” into “are the ratios”.
[Comment 13] Row 292 Replace the point after Eq23 with “Eq.23, where”
[Answer] Thanks for your correction. We supplemented a point between “Eq” and “23”.
[Comment 14] Row 296 “r21 and r22 are the radii (or radiuses)”
[Answer] Thanks for your correction. We changed the “radius” into “radii”
[Comment 15] Row 300 Replace the point after “obtained.” with “obtained, as shown”
[Answer] Thanks for your correction. We changed the error text into “obtained, as shown”
[Comment 16] Rows 309 and 310 Leave blank space between numerical values and units “52mm” to “52 mm”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 17] Rows 321 and 322 Leave blank space between numerical values and units “6210.1N” to “6210.1 N”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 18] Row 329 and 322 Leave blank space between numerical values and units “95Nm” to “95 Nm”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 19] Row 331 Title of the table must be on the next page with table 3
[Answer] Thanks for your correction. We correct the problem of the title and rechecked after finish the paper to make sure there is no similar error in this paper.
[Comment 20] Row 341 Remove “and” in “the materials and of the”. At the end of this sentence, it would be better to say “are all heat treated having a hardness of 55-60 HRC.” Also it would be interesting to mention the type of heat treatment applied.
[Answer] Thanks for your correction. We delete the “and” and changed the sentence with “are all heat treated having a hardness of 55-60 HRC.” As for heat treatment, we used hardening process in diesel in 60~80 degrees to make sure the hardness within the allowable range.
[Comment 21] Row 342 “The material of the spring is rubber” and “ the geometrical parameter is presented in Table.1.” or “The geometrical parameters are presented in Table.1.”
[Answer] Thanks for your correction. We changed the error text into “The geometrical parameters are presented in Table.1.”.
[Comment 22] Row 343 “shows the structure of DAROC in before and after”
[Answer] Thanks for your correction. We changed the error text into “shows the structure of DAROC in before and after”.
[Comment 23] Row 348 “ The experiment begins with”
[Answer] Thanks for your correction. We changed the error text into “The experiment begins with”.
[Comment 24] Row 359 Leave blank space between numerical values and units “95Nm”
[Answer] Thanks for your correction. We supplemented a space.
[Comment 25] Row 381 Please delete the point at the start row (put it at the end of the previous row)
[Answer] Thanks for your correction. We deleted the point at the start row.
[Comment 26] Row 386 Please change “Eq.32.” with “Eq.27.”
[Answer] Thanks for your correction. We changed the error text into “Eq.27”.
[Comment 27] Row 389 Please change “Eq.33.” with “Eq.28.”
[Answer] Thanks for your correction. We changed the error text into “Eq.28”.
[Comment 28] Row 404 Change “The average torsion stiffness can be calculated in Table.6” with “The values of the average torsion stiffness are presented in Table.6.”
[Answer] Thanks for your correction. We changed the error text into “The values of the average torsion stiffness are presented in Table.6.”.
[Comment 29] Row 408 Please change “Fig.11” with “Figure 11”
[Answer] Thanks for your correction. We changed the error text into “ Figure 11”.
[Comment 30] Row 410 Add “ .” - Table.6
[Answer] Thanks for your correction. We supplemented a “.” at Table.6.
Author Response File: Author Response.pdf
Reviewer 3 Report
Paper is interesting, clear, and well written. Experimantal tests seem effective.
The researchers aim to find an overrunning clutch, a freewheel, having better performances than the typical ones.
Any form of innovation or optimisation of a mechanism can be interesting. I think that what is proposed in the paper is a good improvement of the working way of this kind of mechanism. The experimental tests appear to confirm the theoretical approach described in the first part of the paper. We , indeed, cannot speak about "a gap" in the field, but this research contributes to improving the technical aspect of these kinds of mechanisms.
Paper presents some technical innovations on a particular machine element. In the introduction of the paper an analysis on the actual solutions, I agree with, has been made. (However, see point 6 as a comment to references)
The used scientific procedure appears as "classical" and gives a consistent approach to the research. The analysis of previous publications is supported by a theoretical approach and hypotheses are validated by experimental tests. No suggestions about further controls. In the last paragraph the description of future works appears correct and specifies the steps of deepening of the research..
As the freewheels work in different phases, during the description, I advise to strongly stress the phase you are describing. Try to strictly follow the paradigm of the "description by phases" very often used for the description of operating machines or components.
The possibility of building an innovative clutch mechanism seems effective considering both the theoretical / mathematical model, and the experimental tests which appear to evaluate it.
Are the references appropriate?
I think they are, even if, as I indicated in my previous comment, references could be improved by adding some European and American papers on the subject, also considering different kinds of clutches to spread the examples. It could be interesting to add some "historical papers" or old patent documents (see for example US Patent "Roller clutch as fitted to Cheylesmore tricycle", 1881).
Some figures could be simplified (as for example Figure 2) according to the text description. However a deep reading of the text can partially justify the redundancy of the elements contained. As the freewheel mechanism has different working phases, I advise to stress in the text, near formulas or figures, the phase you are analysing.
Author Response
Response to Reviewer #3
Dear Reviewer,
We would like to express our sincere appreciation for your careful reading and invaluable comments to improve this paper. We have addressed all issues raised by the reviewer. The amendments made are mentioned below with reference to appropriate paragraphs and sections of the revised manuscript. Revised portions are marked in green in the paper. If other reviewer mentioned the same error, it will be highlighted in green.
[Overall Comment] Paper is interesting, clear, and well written. Experimantal tests seem effective.
The researchers aim to find an overrunning clutch, a freewheel, having better performances than the typical ones.
Any form of innovation or optimisation of a mechanism can be interesting. I think that what is proposed in the paper is a good improvement of the working way of this kind of mechanism. The experimental tests appear to confirm the theoretical approach described in the first part of the paper. We , indeed, cannot speak about "a gap" in the field, but this research contributes to improving the technical aspect of these kinds of mechanisms.
Paper presents some technical innovations on a particular machine element. In the introduction of the paper an analysis on the actual solutions, I agree with, has been made. (However, see point 6 as a comment to references)
The used scientific procedure appears as "classical" and gives a consistent approach to the research. The analysis of previous publications is supported by a theoretical approach and hypotheses are validated by experimental tests. No suggestions about further controls. In the last paragraph the description of future works appears correct and specifies the steps of deepening of the research.
As the freewheels work in different phases, during the description, I advise to strongly stress the phase you are describing. Try to strictly follow the paradigm of the "description by phases" very often used for the description of operating machines or components.
The possibility of building an innovative clutch mechanism seems effective considering both the theoretical / mathematical model, and the experimental tests which appear to evaluate it.
[Answer] Thank you for your carefully reading of our manuscript. We are honored to receive thoughtful, detailed and valuable comments, which help us greatly improve the manuscript. We have made revisions to our manuscript in light of the reviewer’s comments one by one.
[Comment 1] Are the references appropriate?
I think they are, even if, as I indicated in my previous comment, references could be improved by adding some European and American papers on the subject, also considering different kinds of clutches to spread the examples. It could be interesting to add some "historical papers" or old patent documents (see for example US Patent "Roller clutch as fitted to Cheylesmore tricycle", 1881).
[Answer] Thank you for your valuable comments. We have carefully revised your suggestions. In fact, the research on overrunning clutch in Europe and America has been very mature, and their articles have inspired me a lot. In the introduction section, we have supplemented two articles on the application and design of overrunning clutch in Europe and the United States and two patents on overrunning clutch in the United States
[Comment 2] Some figures could be simplified (as for example Figure 2) according to the text description. However a deep reading of the text can partially justify the redundancy of the elements contained. As the freewheel mechanism has different working phases, I advise to stress in the text, near formulas or figures, the phase you are analysing.
[Answer] Thanks for your suggestion about the figure. In fact, the information in Figure 2 is too complex and too much, and the contact force can also be carried out by using the static balance at nodes A and B (only 2 loads). Therefore, we simplify Figure 2. In the new Figure 2, the direction of rotation shows two working conditions. The redundant parameters are deleted and the figure are separated in two subpictures which show the geometry and static mechanism under overrunning conditions. We hope this figure improve the demonstration ability and explain these two working conditions well.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I thank the authors to have taken into account most of the remarks.
Some minor modifications have to be done prior to publication.
Section 2.1 line 30. The self-locking at the overrunning condition due to the fulcrum C is not explained. The overrunning condition implies slipping at point A. The contact in C makes the sprag unroll and the spring pressure makes the position stable. The statement should be clarified.
Figure 3 still shows a model that is not used by the authors. The loads in point B should not be detailed as they are neglected. Moreover, two options to model the equilibrium of the sprag are possible to counterbalance the load in A. The first one is to consider a normal load in C and a normal load in D. As a consequence, the spring pressure cannot be ignored. The second option is to neglect spring pressure and to consider a tangential load in point D.
In the current form of the paper, Figure 3 is consistent with option one but the maths is made with option two. Please correct the paper (figures and/or formulae) in order to be consistent.
Figure 2: add the force due to contact pressure in D or the tangential load in C.
Figure 6 would be much more explicit with representing the total loads at point A and B instead of tangential and normal components with arbitrary lengths. At least, line AB should be represented as it is a key to easily understand the equilibrium of the parts: angle between line AB and the normal of contact is to be lower than the angle of the friction cone.
The torsional stiffness depends not only on the contact stiffness of the rollers of sprags but also on the stiffness of the coupling of inner and outer rings with the system.
The contact with each inner ring is made with a key which is similar for each configuration tested. A key is also visible on the outter ring of the SOC but the coupling is much more different for ROC and DASOC. This may introduce a bias in the comparison that should be pointed out in the paper.
It is clear that the radiuses of contact directly influence the values of contact stresses. In the study, the authors have chosen to put forward DASOC using greater r1 and r2 values than in the ‘compared’ SOC. Thus, the comparison is unfair. The authors should have in mind that the designers of the SOC could have chosen the same r1 and r2 values as for DASOC (or even greater) to decrease contact pressure but they haven’t. There is a reason for that. There is a limiting factor that has not been considered in the study. I fully understand that the presented work needs to be developed later, there is no problem with that. The authors have to detail the limits of this study to be clear with the lecturers. This fact is to be included in the text and/or in the conclusion.
Galling due to wear may be a major limiting factor. That should at least be included in point 3 of further studies.
Some other minor corrections should be addressed prior to publication
Page 4, line 138: “and, and” should be corrected
Figure 5: SOC uses a sprag, not a roller
Page 16, line 454: replace “were studied” by “should be studied”
Author Response
Response to Reviewer
Dear Reviewer,
We would like to express our sincere appreciation for your careful reading and invaluable comments to improve this paper. We have addressed all issues raised by the reviewer. The amendments made are mentioned below with reference to appropriate paragraphs and sections of the revised manuscript. Revised portions are highlighted in yellow in the paper.
[Overall Comment] Some minor modifications have to be done prior to publication.
[Answer] Thank you for your carefully reading of our manuscript. We are honored to receive thoughtful, detailed and valuable comments, which help us greatly improve the manuscript. We have made revisions to our manuscript in light of the reviewer’s comments one by one.
[Comment 1] Section 2.1 line 30. The self-locking at the overrunning condition due to the fulcrum C is not explained. The overrunning condition implies slipping at point A. The contact in C makes the sprag unroll and the spring pressure makes the position stable. The statement should be clarified.
[Answer] Thank you a lot for pointing this out. We are very sorry that there is an error in the expression here in the article, which leads to your confusion. In fact, in this state, point C should not generate a self-locking state. We have modified the corresponding part of the original text.
[Comment 2] Figure 3 still shows a model that is not used by the authors. The loads in point B should not be detailed as they are neglected. Moreover, two options to model the equilibrium of the sprag are possible to counterbalance the load in A. The first one is to consider a normal load in C and a normal load in D. As a consequence, the spring pressure cannot be ignored. The second option is to neglect spring pressure and to consider a tangential load in point D.
In the current form of the paper, Figure 3 is consistent with option one but the maths is made with option two. Please correct the paper (figures and/or formulae) in order to be consistent.
[Answer] Thank you for your carefully reading, and we feel sorry about appearing repeated errors. With reference to your opinion, we have made corresponding modifications to Figure 3, and also made changes to the subsequent calculation method to ensure that the calculation method is consistent with the figure
[Comment 3] Figure 2: add the force due to contact pressure in D or the tangential load in C.
[Answer] Thank you for your comments. According to your suggestion, we have modified Figure 2 accordingly, adding the pressure at point D and the tangential force at point C.
[Comment 4] Figure 6 would be much more explicit with representing the total loads at point A and B instead of tangential and normal components with arbitrary lengths. At least, line AB should be represented as it is a key to easily understand the equilibrium of the parts: angle between line AB and the normal of contact is to be lower than the angle of the friction cone.
[Answer] Thank you for your suggestion. We followed your suggestion and made corresponding modifications to Figure 6, adding line AB, and the length of each force is changed so that the resultant force of the two components points to AB. I believe this change will make the Figure more clearly.
[Comment 4] The torsional stiffness depends not only on the contact stiffness of the rollers of sprags but also on the stiffness of the coupling of inner and outer rings with the system.
[Answer] Thank you for your comments on the content of the article. I explained your views in the further study. In fact, the stiffness of the overrunning clutch is the coupling stiffness of the stiffness of the outer ring, the stiffness of the inner ring and the combined stiffness. But according to the research, it is found that the combined stiffness has the greatest impact, and there are many reasons for affecting the combined stiffness. The most prominent one is the dimensional deformation of the slider and the inner and outer rings caused by the force during the combination process. We will continue to dig deeply into the detailed calculation of the overrunning clutch stiffness as an important follow-up study.
[Comment 5] The contact with each inner ring is made with a key which is similar for each configuration tested. A key is also visible on the outter ring of the SOC but the coupling is much more different for ROC and DASOC. This may introduce a bias in the comparison that should be pointed out in the paper.
[Answer] Thank you for your comments on our experiment. In response to your comments, I added an explanation in the experimental section. The shape of the key of SOC is different from those of the other two types of keys on the outer ring of the clutch, which is thinner and longer than the other types of keys. However, the size of the cross sectional area of the three keys in the direction of shear force is basically the same, which leads to little difference in the deformation of the three keys under the same shear force. The deformation of the key within the given force range in the experiment is very small according to experimental results, which basically does not affect the results. Therefore, the influence of this part of deformation is ignored in the experiment.
[Comment 6] It is clear that the radiuses of contact directly influence the values of contact stresses. In the study, the authors have chosen to put forward DASOC using greater r1 and r2 values than in the ‘compared’ SOC. Thus, the comparison is unfair. The authors should have in mind that the designers of the SOC could have chosen the same r1 and r2 values as for DASOC (or even greater) to decrease contact pressure but they haven’t. There is a reason for that. There is a limiting factor that has not been considered in the study. I fully understand that the presented work needs to be developed later, there is no problem with that. The authors have to detail the limits of this study to be clear with the lecturers. This fact is to be included in the text and/or in the conclusion.
[Answer] Thank you for your suggestions on our experiment. It is true that, theoretically, the designers of the SOC can chose the same r1 and r2 values as for DASOC, but the aim of this study is to design a new type of overrunning clutch which has a better performance to replace the market overrunning clutch. Although the dimensions of the overrunning clutch roller designed in this paper are different from them, the overall dimensions are the same, so it can completely replace the existing products on the market, and has better performance. We chose the product with an inner diameter of 20 mm and an outer diameter of 52 mm (HENG OU brand CK-A2052) to measure its parameters. The DASOC we developed to have the same inner and outer diameters, so that it can replace the market SOC, whose stiffness performance is 6.2 times that of the SOC. In future research, we will continue to conduct the r1 and r2 research on SOC. We have also explained this in the conclusion.
[Comment 7] Galling due to wear may be a major limiting factor. That should at least be included in point 3 of further studies.
[Answer] Thanks for giving us the advice, and we have added this in the further study part.
[Comment 8] Page 4, line 138: “and, and” should be corrected
Figure 5: SOC uses a sprag, not a roller
Page 16, line 454: replace “were studied” by “should be studied”
[Answer] Thanks for your comments. We are sorry for the mistakes. We have checked the manuscript and made corrections on those parts with typos.
Author Response File: Author Response.pdf
