SES 2015 - T5.4.2 Rule, What do you undesrtand from it ?

[John_Burford]

A multi-segment tube is one that is cut and welded to another tube before attaching to the main hoop. The critical factor is whether the bending moments in the shoulder harness bar are transferred across a weld. It is ok to weld a brace to a continuous shoulder harness bar, but is to not acceptable to have the bending loads go across a weld. In a frontal impact the shoulder harness bar is expected to yield plastically, so loading (bending) through the brittle heat effected zone is not allowed.

John Burford

[Bemo]

I don't get the confusion. Rule T3.5.5 is still in the rules. It was even modified for 2015...

[Martin Borkowski]

It is my first post so I would like to say Hello to everybody. My name s Martin and I'm part of PUT Motorsport team from Poznan University of Technology in Poland.
We are building the car and competing for the first time this year and we have the honour tot take part in FSUK, FSG and FSH. In the team I am resposible for the tubular frame design.

I would like to add my two question's to this thread. I have uploaded the SES to FSG competition site couple of days ago and have received a message today that it has failed the check.

First of all, the person who reviewed the SES has asked to provide more specific information about the frame material in the cover sheet tab. Unfortunately the tabs in Cover Sheet and in the tabs from where the material data is loaded from, are locked with a password. The only option to choose is basic material: Steel. This seem to be not enough. Any one else had this issue?

Another problem is with the calculations. I have chosen a design which is not compatible with rule T3.5.5 (the supporting tube is smaller cross section than the harness tube). Therefore I must have submitted the calculations. The harness attachment tube is continuus bent tube so I understand that the 2D calculations are sufficient. My question is if the calculations found in SES file in tab T5.4.2_Shoulder_harness_brace are enough to meet the rules requirements or do I need to make additional calculations as the person who have checked my SES has asked for?

My kind regards to all,
Martin Borkowski
PUT Motorsport

[Tiago-IFS]

A multi-segment tube is one that is cut and welded to another tube before attaching to the main hoop. The critical factor is whether the bending moments in the shoulder harness bar are transferred across a weld. It is ok to weld a brace to a continuous shoulder harness bar, but is to not acceptable to have the bending loads go across a weld. In a frontal impact the shoulder harness bar is expected to yield plastically, so loading (bending) through the brittle heat effected zone is not allowed.

John Burford

John Burford,

Of course I perfectly understand what you mean and I had already thought about that, but in my design there is no “Bending loads on welded joints " of course this one exists almost everywhere in the structure if we do not consider the joints to be perfect and the structure to act as a truss. So according to your understanding my design doesn't coincide with the problem you are stating right? Since the harness bar that I present, is a fully continuous bar ( no segments ), but the only fact is that this one is connected to the main hoop bracing with the lateral extra tubes in order to have a proper triangulation.

Tiago

[Tiago-IFS]

I don't get the confusion. Rule T3.5.5 is still in the rules. It was even modified for 2015...

Bemo,

the confusion is that the SES section T 5.4.2 in some way does include the rule T 5.4.1 as well, but this isn't stated anywhere, and we worry to know if we need to comply with extra calculations or not.

I wish I could explain everything better with some more images or even face to face explanation,

but thank you very much Bemo

Tiago

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Unfortunately the tabs in Cover Sheet and in the tabs from where the material data is loaded from, are locked with a password. The only option to choose is basic material: Steel. This seem to be not enough. Any one else had this issue?

Martin,

Have no idea what happened to excel workbook, but mine is fully operational. I downloaded it from fsaeonline.

Another problem is with the calculations. I have chosen a design which is not compatible with rule T3.5.5 (the supporting tube is smaller cross section than the harness tube). Therefore I must have submitted the calculations. The harness attachment tube is continuus bent tube so I understand that the 2D calculations are sufficient. My question is if the calculations found in SES file in tab T5.4.2_Shoulder_harness_brace are enough to meet the rules requirements or do I need to make additional calculations as the person who have checked my SES has asked for?

Supposedly It would be sufficient enough, but the judge has is reasons, could you post some images in order to have a better view of what you are saying ? and what might be making the judge asking for extra calcs?

It would also help me to clarify my issue.


Tiago

[John_Burford]

Tiago

You are making the assumption that the main hoop can be used as a rigid constraint for reacting your loads. This eliminates moments in the joint reactions, and it is an incorrect assumption. The main hoop has a low lateral stiffness. The analysis of the joint reactions should assume a 6 dof constraint at the shoulder harness attachment and the attachment to the main hoop is free. This is basically and cantilever beam. It is a conservative approach, and for hand calculations this is what we are looking for. You can include the main hoop in a Finite Element Analysis to capture the lateral stiffness of the main hoop if you want.

John Burford

[Martin Borkowski]

Please correct me if I am wrong. To comply with rule T3.5.5 the shoulder harness brace must:
- be attached to the farthest point from the line connecting both ends (see picture)
10984540_10206147987522542_7317938189144951163_o.jpg

- have the same diameter and thickness as the bent tube (25x2,5mm in this case)

- be angled no more than 45deg from plane of bent tube (see picture)
1.JPG

- terminate at node of the chassis
2.JPG

Am I correct that because of the last point my design does not follow the rule T3.5.5? I have shown in SES that the support tube I am using is of smaller diameter than the bent tube and that was the main reason the reviewer said that I need to attach calculations. In my understanding even if I use the required tube diameter, the design will still not be compliant with the rules and therefore the calculations are required.

Another question is if the FEA analysis is sufficient method of calcucations or does the rule comitee require hand analytical calculations too?

Thank you for your response.
Martin Borkowski