DO I NEED TO TRIANGULATE DE FOLLOWING? chassis question TSR15

[ASIER]

Good morning,

My name is Asier and I´m the resposible of the chassis department in Tecnun Seed Racing, FS team from Spain.

Despite the chassis being manufactured and being late to solve it in a proper way, there is a node of bars in the Main Hoop that from some peoples point of view needs to be triangulated. Having done extensive research I am still waiting for a reasonable answer...

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We are going to Montmelo the Spanish circuit in Barcelona and I would like not to have any problems in the scrutineering.

Having said that, I would appreciate it if you could tell me whether a proper triangulation is needed or not.

Thank you so much for your cooperation! :)

Asier Telleria

[Claude Rouelle]

ASier,

What do YOU think you should / should not do?

[Claude Rouelle]

ASier,

What do YOU think you should / should not do?

[Jonny Rochester]

There needs to be a wider photo because I can't work out what bit is what. This is for electric I gather, and sidepods for the batteries?

It is likely that you have enough triangles to cover the rules, (maybe, I can't see).

If you do cover the rules, the next question is, is it good design? Or more importantly, will it flex or crack? If there is an obvious place for a tube as you have already pointed out, weld it in. And bring some tubes and make sure there is a welder at the competition!

[ASIER]

Hi guys,

Sorry I haven´t got round to writing you sooner, but I have had loads on my plate recently with several tasks...

Although the blue drawn bar is nor welded yet, my opinion is that in case of any frontal impact the mainhoop node would go backwards. To avoid this, the bar is needed.

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I am not sure at all... What is your opinion?

Thank you so much for your cooperation!

Asier Telleria

[CWA]

Hi Aesier,

First, can you include a copy of (or link to) the technical regulations that you should be adhering to? I am not sure which regulations are in place for the event you plan on attending.

My immediate concern is that your main hoop is not supported enough to be legal at all, even if you do add in the bar that you have suggested. Unless perhaps you are defining the more-rearwards hoop (the one angled in side-view) as your main hoop? I am not too familiar with the rules, so rather than speculating / fear mongering, it would be best for you to include some regulations for us to refer to.

For my general thoughts on your design, have a look at the drawing I have attached. Your suggested bar addition is shown in light blue.

My concern is the quadrilateral arrangement of tubes highlighted in green. This area concerns me if a roll-over is considered, where force will be acting into your vertical roll hoop 'from above' as depicted by the upper red arrow (pointing 'down'). With the tubes below your vertical hoop unsupported (and weakened by the bend), the force acting through the vertical hoop if the car should roll will be creating a bending moment around the lateral tube (and end nodes) that I have highlighted with yellow (the effective moment is depicted by the lower 'curved' red arrow).

This green arrangement of tubes is an area that I believe could benefit from triangulation, more than the area that you have suggested. I believe this area of chassis, if left unmodified, will attract particular attention from the scrutineers more than the area you have suggested modifying.

I have depicted my suggestion for tube addition with the dark blue line. This will provide triangulation of the green arrangement of tubes, to protect against potential buckling of the node circled red. From what I can make out, if you add your own light blue bar as you have suggested will make some difference if implemented with my suggested bar, but will make no difference if implemented without my suggested bar, at least in a roll-over situation. Perhaps your suggested bar will help add strength / reduce deflection in a longitudinal crash situation, which I believe is what you are implying, but what I have discussed above seems more critical to safety than this.

I'd be keen to hear the thoughts of others.

[Will M]

I agree with CWA about the MRH.
It looks like the MRH has a welded joint.
As I remember the FSAE rules it must be a continuous tube.
Or it has a very tight bend radius, which is also limited by the rules.

I outlined what I consider the MRH and the joint in question is circled in yellow.

-William

[CWA]

-William

Do you have a source for the regs, William? What you've said seems valid and rings a bell with me, but it would be good to check word for word, and cite the specific regs for the OP where applicable, I think.

[Will M]

T3.11 Main Hoop
T3.11.1 The Main Hoop must be constructed of a single piece of uncut, continuous, closed section steel tubing per Rule T3.4.1.


T3.10.7 The minimum radius of any bend, measured at the tube centerline, must be at least three times the tube outside diameter. Bends must be smooth and continuous with no evidence of crimping or wall failure.

Enjoy,
William

[CWA]

T3.11 Main Hoop
T3.11.1 The Main Hoop must be constructed of a single piece of uncut, continuous, closed section steel tubing per Rule T3.4.1.


T3.10.7 The minimum radius of any bend, measured at the tube centerline, must be at least three times the tube outside diameter. Bends must be smooth and continuous with no evidence of crimping or wall failure.

Enjoy,
William

Assuming the regulations Will has quoted are applicable to the event Asier plans to attend, it does seem that his main hoop is unacceptable for entry. For 100% confirmation, please can you cite a source for these regulations Will?

I would only add to confirm that I believe the rear pair of tubes cannot be considered as the 'main hoop' as I may have previously suggested, for they also breach regulations:

- T3.11.3 The Main Hoop must extend from the lowest Frame Member on one side of the Frame, up, over and down the lowest Frame Member on the other side of the Frame
- T3.11.4 In the side view of the vehicle, the portion of the Main Roll Hoop that lies above its attachment point to the Major Structure of the Frame must be within ten degrees (10°) of the vertical.

These are taken from a copy of the 2014 Formula SAE regs that I found here - http://fliphtml5.com/sibd/qhxw/basic. This source also includes the regulations Will has referred to. I assume they are applicable, someone should correct me if this is not the case.

Under this assumption, sorry to be the bearer of bad news Asier, but it does not look like you will be able to compete without modifying that frame in some extensive way.

[Will M]

http://students.sae.org/cds/formulaseries/rules/2015-16_fsae_rules.pdf
These are the 2015 Formula SAE rules.
That is all the feedback I'm going to provide until Asier provides some information/research/analysis of their own.

-William

[ASIER]

Hi guys,

CWA your answer is amazing, I feel what you say is totally true and makes 100% sense. I will take care of that triangulation and weld both blue bars. After all, the chassis weights 50kg and despite the weight being important we don´t care at all...

Will M you are right, that MH is bad welded and this is a problem I detected before. Definitively, we are manufacturing again the MH side of the frame.

Thank you so much for helping this beginner in the FSAE.

Best regards,

Asier Telleria

[Pat Clarke]

Asier,
I don't think you understand.
Regardless of how many tubes you weld into your chassis, it will not pass technical inspection at any FS/FSAE event!
Go back and read the rules relating to the main roll hoop and its supports.

Pat Clarke.

[ASIER]

Good morning Pat,

With the aforementioned points manufactured I believe there would not be any problem in the technical inspection.

However the following rule makes me think the opposite to be true..

T3.10.7 The minimum radius of any bend, measured at the tube centerline, must be at least three times the tube outside diameter. Bends must be smooth and continuous with no evidence of crimping or wall failure.

I will take a look in our CAD to be sure that the closest bend in the MH is right.

I guess that is the reason why of your post. Otherwise, what do you mean?

Thank you for your cooperation,

Asier Telleria

[Pat Clarke]

Asier,

I have posted specific details on the team facebook page so the team can see what the issues are.

I am also very offended by your private response, especially the language used.

I expect an apology

Pat Clarke

[ASIER]

Hi Pat,

I am so sorry about what has happened. I worked very hard to get the chassis and the university credits, and I misunderstood your comments. I did not know to whom I was writing and I am really sorry…

I swore this is not going to happen any more, and I will inform myself to whom I am writing before.

My kindness regards,

Asier Telleria

[Pat Clarke]

Apology accepted Asier

Pat Clarke.

[CWA]

Glad to see that bridge fire put out in time.

Pat, would you be willing to share your thoughts on the frame with others here? It may benefit some different teams in the future, and I'd also certainly be keen to hear what you have to say for my own benefit. If it is personal advice that you would rather stays private then I understand.

[Pat Clarke]

CWA,
The issue with Asier was a private one and is now in the past. It had nothing to do with the chassis design and the errors therein. These have already been highlighted several times.

Pat