Would you dare ride this on a potholed highway? Or is this a static “art piece”?
You can check out the description and build pics on the Revival Cycle page.
My first reaction was the spindly frame would fold up at the first bump it hit. Yes, it has a telelever front end but the rear is all rigid. Yes, its all titanium and fully welded, and yes its extensively trianglated. But still…
I headed over to check out the pics and description to see whether it had been designed and built as a rider or a static piece.
I was hoping to see some comments that it had been designed with riding in mind (there is some talk of land speed racing with it) but I didn’t see anything. If anyone knows of any press where this is covered please let me know.
Here is Australia, we have some national guidelines for manufacturing custom vehicles.
While this specific guideline is for 4-wheel vehicles, I’d expect a certifying engineer would apply it to motorcycles since this information is already in the public domain (good for legal CYA).
Regardless, if I was custom designing a frame for road use I’d want to make sure it was strong enough, and this bulletin gives some guidance.
The guideline for suspension, steering and tyres calls out certain parameters for strength and safety:
Stress analysis should be carried out for modified or specially fabricated components and the following load conditions are suggested as a guide:
- bump loads: 4g vertical;
- rut loads: 1g vertical combined with 0.6g lateral; and
- skid loads: 2g vertical combined with 1.2g skid (longitudinal).
Overturning loads: 2g vertical combined with 2.5g overturning; where g is the static load at the tyre contact patch when the vehicle is stationary. The stress levels that are acceptable under these conditions will depend on the materials and the number of times in the life of the vehicle that the loads can be expected to occur.
This analysis can be carried out with FEA software. Here is an example dating back a few years now where my client wanted a beam extension on a Type-1 Volkwagen:
My thoughts on the Revival Birdcage bike revolve around the size of the welds in the frame. I’m not sure the diameter of all that titanium. It looks about 10mm. Maybe 8mm. Hard to say. I’m not even sure its solid bar or tube. There is one mention of “titanium rod” so I’m guessing its solid. Someone correct me if I’m wrong.
But the size of the tube somewhat dictates the size of the weld you can apply. The strength of a fillet weld is determined by the size of the fillet itself. Big weld; more stress, small weld; less stress.
A Ducati Monster or Yamaha TRX frames have much larger tube diameters than this bike. And much larger weld sizes. That’s for a reason: so they last the life of the bike when subjected to road conditions.
So all things considered, I’m thinking this is rolling art.
What do you think?