[FSE] FSG 2011; SEF car E34

[Ondra Fric]

Dear Mr Bulling,

our last year car (more accurately our 2010 combustion engine powered car before splitting of the team) uses almost the same solution. The SEF we had last year was very similar to this year's one and it passed through check up correctly because it was considered as a frame diagonal member substitution and not as a monocoque.

I am not sure if I understood correctly to the shearing test. Is it meant to be some kind of a steel ball/cylinder pushed perpendicularly to the surface of the sandwich? How shall we support the sandwich? Does it have to be supported by desk with the hole of the same shape as of the impacting member? Is it necessary to fasten the sample against tensioning of upper skin?

So if we will consider it as a monocoque side impact I understood your email that it is necessary to fasten it by bolts ("So your sandwich-panel is to use as an "Monocoque side impact" (see rule B3.37.3). "). Do I understand it correctly? According to my opinion it is not necessary to bolt it to the frame. I had calculated that bonding to the outer side surface of the frame tubing is sufficient.

On the page 22 of the SEF you have marked that I used wrong surface of bonding for shearing and you consider it as tensional loaded. If I push to the outer skin of the sandwich it bends into the car and it means that the skins will slide on the outer side of the surface of the tubes where it is bonded (this is not brittle material as carbon). With such ductile material as aluminum it is not correct to think that the skins bends out of the bonding surface. Shearing on the surface between the tube and the sandwich as you have marked will surely occur but bonding at this place will be done only as redundant because of accuracy of manufacturing.

Concerning the shoulder harness we had already find the solution by gusseting to the main hoop and also supporting the firewall.

Best regards

Ondrej Fric

> ------------ Původní zpráva ------------
> Od:  <ulf.bulling na dekra.com>
> Předmět: FSG 2011; SEF car E34
> Datum: 22.6.2011 13:04:32
> ----------------------------------------
> Dear Mr Fric,
> 
> I have checked your SEF. My remarks you can find in the attachment. In 
> fact of your sandwich-panel we talk to Mr Steinfurth (FSG). So your 
> sandwich-panel is to use as an "Monocoque side impact" (see rule B3.37.3). 
> 
> At least I can't find your shear test to rule B3.31.3.
> 
> You status at the FSG website is changed to fail.
> 
> With best regards
> 
> Ulf Bulling 
> Fachspezialist / Specialist 
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--------------------------------------------------------------------------------------------------------------------------------------------------------------
Ondřej Fric
CTU CarTech Electric - Formula student electric racing team
Czech Technical University in Prague
icq#:  394-760-523
tel:     +420 775 396 531