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davidhembrow

Sinner Mango Velomobile wheel arch aerodynamic improvements

by davidhembrow Sep 8, 2015
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Great work David and thank you for sharing it!

I've been trying to shorten the long edge of the wheel arch as my Mango's (Tour) been lowered by 2cm (using a hard+hard spring combo), but without any success, being quite new to the 3D scene I don't think I have the skillset yet to do such editing/modifications.

Any tips, advice or even better, a remake of the wheel arch piece to account for the lower suspension strut, would be quite welcome! Right now with the original model, a tire like the Shreda will rub against it when doing a slight turn, a Marathon Tour Plus tire won't even fit with the part in place.

Unfortunately I haven't rode with these parts long enough to be able to make an observation on speed gain, although I do agree with David, it does clearly make an aerodynamic difference.

Cheers!

You're very welcome. These arches are designed for the Mango Sport body and the wheel arches have a slightly greater radius on the Tour body so they may not be quite a perfect fit for you. Scaling the design up slightly would account for the larger radius of your wheel arches. Incidentally, that's also why you can fit wider front tyres which are more likely to rub.

To work with the larger tyres and lowered suspension I think the easiest thing is simply to cut some of the plastic away until there is no rubbing.

My first attempt at making these was with a design flat across the bottom and without the cut-away section. As a result, it rubbed on the corners even with narrower tyres. I then modified the design to have the shape shown here as that does not rub on my Mango. However, I only printed one of the new design which was installed on the left side and still use the modified prototype, cut away so that it now looks more or less identical, on the right side.

Do you have any approximate indication on how much speed you gain these?

Ralf: That's almost impossible to quantify. However my best ever racing results were with similar aerodynamic modifications. You can watch some videos https://www.youtube.com/watch?v=PTx7DKSlbPg and https://www.youtube.com/watch?v=PSeUtB5flcE. In that case the modification was more temporary: a sort of spoiler just before the wheel arch to disturb the laminar flow which otherwise went into the arch. This 3D printed attachment achieves something similar in that the top of the wheel arch maintains laminar flow all the way past the wheel while the flow of air is broken by the sharp back edge on the other pieces at the front of the arch. I have no wind tunnel, but a large PC fan attached to a cardboard tube provided some good fast flowing wind and tufts of cotton attached by tape allowed me to see where the air was going. But measuring the actual speed difference is almost impossible because there are so many other variables.