Hello everyone, since I've haven't posted anything for a while, I will present myself again. My name is Tiago and I'm part of the chassis group from ISEL Formula Student Team, from the Lisbon Higher Institute of Engineering.
This is our second year as a team and we are now building our first car to participate in the Formula Student Spain competition.
This time my issue is about the Structural equivalency spreadsheet, referring to tab T 5.4.2. , I don't know if I've understood it wrongly, but Is it just me or this rule and respective section in SES is just about confusing and ambiguous?
First:
The rules states: "If the harness is mounted to a tube that is not straight, the joints between this tube and the structure to which it is mounted must be reinforced in side view by triangulation tubes to prevent torsional rotation of the harness mounting tube. Supporting calculations are required. Analysis Method: Use 7kN load per attachment and the range of angles in T5.4.4 calculate that the bent Shoulder Harness Bar triangulation stresses are less than As Welded Yield Strength (T3.4.1 note 4) for combined bending and shear and does not fail in column buckling. If the team chooses not to perform the strength analysis rule T3.5.5 will apply."
Referring to the SES interpretation and approach:
ses1.jpg
So if the design corresponds to the first point everything is ok and no calculations are required, if the design corresponds to the second point, this means a CONTINOUS TUBE connected to the main hoop with additional supports due to the existing offset ex:case3.jpg extra calculation are required. And then starts a nightmare for my understanding.... for the third point my interpretation tells me that any design which has NO continuous tube has connected to the main hoop should include extra calculation in 3D. From this, I can conclude that any other shoulder harness bar whether or not continuous as well as NOT connected to the main hoop also needs extra calculations, well also this covers the rule right before this one ! Which is T5.4.1.
resuming all of this:
We have three generic types of situations (presented on the next images):
case 2.jpgcase 4.jpgcase 5.jpg
My doubts are right here, Is this section of SES only applying to the case where cases are not covered by T5.4.1 or does this include it ?????? Normally according to the excel file I would think that the first statement is the right one and no extra calculation are required when the shoulder harness bar is mounted in the main hoop bracing and proper triangulation is done, because the tab is only referring to rule T5.4.2. Since many teams have this type of design and haven't got problems with it, being able to participate in all events, and adding the fact that this has been working for a while and these rules are fresh new I’m a little bit unsecure with them.
Can anyone help with that, whether with their experience and/or interpretation?
Tiago
ISEL Formula Student