@meamoantonio Well Antonio I could come at this from many sides, but I will keep my comments simple.
For one; I like the experiment at its base level (and I mean at the very lowest base). Crudity is often the best way to make a point (even if flawed), often even if bypassing more important points. I could put a small amount of explosive into a frame for a more dramatic effect showing cf as the weakest while again proving nothing, but I bet I would get some viral draw to the video (as well as having a 'blast' myself.
Unfortunately, coming from a technical background I have many reservations regarding the perceived results, and the lack of information given by those doing the testing.
Are all the frames brand new and of the same frame size (regarding rider size based geometry, not design geometry (i.e. flat TT vs slant, etc.)? Are all frames of the same discipline design (road race vs road tour vs gravel/hybrid vs MTB vs cargo, etc.)? Using different sized frames (even if from the same discipline) is not consistent for test purposes; and using pre-used frames completely throws test results out because you do not know what stresses a frame may have been exposed to.
I did not really look at the frames they used other than seeing & hearing that the steel frame was a Trek (type/model, tubing type/design unknown to me). So frames are designed to take different stresses in different areas. Some are built up more heavy duty overall than others given their designed usage, size of frame, size of rider, cargo, etc.
Application of force to a specific point (area range in this case) will affect on frame differently than another where one frame may fail in one area but not in another, and where a different frame may fail or not fail in the exact opposite areas.
The test certainly shows how a cf frame can easily fail, but the frame is not designed to receive high stress in that area so it is not really a good metric on which to base your conclusions.
The better, but similar, test would determine for the sake of consistency an exact location(s) to do a test(s). E.g. test at center points on TT & DT as measured from HT/ST/BB centerlines, and/or measure from where the tube reinforcements end and go to the center between those points (not applicable to straight gauge tubing).
The force needs to be consistent and measurable for all tests. E.g. the rubber bands used do not have equal force when stretched to the same length, the never used before rubber bands if used once on one frame and then used again on another frame have then be pre-stressed and will not provide the same force as they would if completely new bands (even given their inherent inconsistency) were used on each test, the bands are not covering the exact same length on tubing in each test, the manner off applying each band is not the same even on one frame test (applied at slightly different angles causing more or less force from each other), the bands are not evenly stressed on each side when applied (causes unequal torsional forces), etc.
So yes, it is a cool visual test; but is completely without any merit based on the lack of technical data (other than number of bands used) that would allow me to draw a logical conclusion as the what it really means barring a crude assumption based only on the number of bands used.
Now to do it in a more laboratory controlled manner, but without involving engineering, they should use strapping (preferably not easily stretched) installed in a manner where each side was evenly stressed. I would use a turnbuckle connected by steel cables which would provide force on a center axis only (eliminated torsional stress) that attaches to steel band clamps of the same width on both tubes (you could vary one width over the other if wanting to isolate a particular tube using a narrow band on that tube only)placed at the aforementioned points on the tubes. And I would do multiple test using bands of varied widths to better determine failure of a tube when force is applied to shorter and longer lengths of tubing; e.g use 1/4" bands, 1/2" bands, 3" bands, etc. Their tests covered various lengths of the tubes because it was obviously more difficult to 'pile on' 500 rubber bands in the same amount of tube length as it was for 200 bands. Now we at least have force more consistently applied and will have data for failure at a variety of tube areas to better compare frames.
But let me go one further to really make it more quantifiable and thus more repeatable if one wanted to conduct tests themselves. Add a cable tensiometer (preferably calibrated) to the turnbuckle connecting cables to provide numerical data.
The test shown, unfortunately, demonizes cf frames without taking into any consideration their engineering and design requirements, and so, though great fun for the shop guys to crush some frames, fails to provide any logical thinker a true metric into what material is best other than the unrealistic rubber band test which, as far as I know, a frame was never designed to withstand. I can, with my prior cardboard & and duct tape boat building experience, build a cardboard & duct tape bike frame that would easily surpass their test (proving cardboard is 'stronger' than steel!?), but that would be a failure when used as a bike so what conclusions can one really come to based on purely sensationalism only? So throw out all of your cf, alloy, steel, Ti, and wood/bamboo frames; and buy my proven to be better 'rubber band tested' cardboard bike frame for your next build!! Also, selling my cardboard boats which can be reused to make bike frames so my stuff is also more ecologically sustainable.
That is my simple breakdown Antonio; the complex one will be covered in my next thesis project.
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