[Teri_TX]

Hi Visionary,

Originally Posted by visionary

A word of thanks

Hi Teri, I hope you will not mind if I use your thread to congratulate Ironside on his sterling efforts to quantify the side-wind stability effects of the stall strip. The two videos posted in his post #82 are the most detailed public domain research that I have seen.

Prior to this work, Craig Vetter’s tuft test photographs from an accompanying vehicle were about the best stuff out there. However, Ironside has trumped Craig for two reasons, firstly by choosing video footage which imparts far greater information than a single still image, and secondly because he has focussed on sidewind stability as a specific issue rather than the general drag reduction which was the point of Craig’s image.

So I think due recognition for this important step is warranted.

Absolutely no objection from me on congratulations to Ironside. When I started this thread, I only expected an armchair discussion of what I perceived to be a cause of cross wind instability and a possible solution. I didn't think someone would step up and actually try out a stall strip so soon on a faired motorcycle. Ironside's tests are very encouraging.

Let us not forget Theo's report of "storm strips" on his velomobile. It showed great promise but the speed regime he operates in is less than a motorcycle's. One thing I've learned in my career is that one has to be very cautious about extrapolating data. Theo says Allert is planning to add "storm strips" on his streamlined motorcycle but that he rarely rides it now.

Much remains to done. Height and shape of the stall strips are just a couple of things that come to mind. Perhaps a second set of stall strips parallel to the center one ... Tests on a full streamlined motorcycle need to be performed. Vetter in a private email has told me "... this is consistant with my preliminary result". I await the official full report on his site.

I'm still holding my breath for a fully enclosed (no side gap) streamlined motorcycle. Allert's is the only one I'm presently aware of.

Ironside has "won a battle" to use a phrase, but there is still a war to be won. I congratulate Ironside for his battle victory in any event.

But, and I hate that there is a “but” , but the videos are of limited value as Ironside himself pointed out "To be honest, I can't see any discernible difference, but then again I don't know what I'm looking for."

I have taken some time to study the videos and have some experience of tuft testing myself, so here are my observations, which I hope will be seen as positive and helpful
<snip>
...

I wish I could see the videos but all attempts on Firefox, Internet Explorer and Google Chrome have failed. I have no idea of the cause. I'll have to just rely on your observations.

Ironside, please don’t give up, you are almost there. I would suggest real world riding rather than fan tests. I would keep the tufts on and take a ride with a couple of friends in a car alongside. One driver and one camera operator (simple handycam will do, phone footage will not work at suitable clearance distance) who can shoot you from slightly ahead and off to side, in windy and still conditions. Compare and contrast the footage with and without the strip(s) attached, and you will own this subject area.

Having a car filming beside Ironside may be tricky and/or dangerous in cross wind testing. The danger should be obvious, particularly if Ironside should get blown toward the car. Tricky because the filming vehicle needs to be distant enough to avoid altering Ironside's local air flow. Vetter didn't have this problem since he was not interested in cross wind effects on the tufts. Also, no slight toward Ironside, Vetter is an experienced accomplished motorcycle rider. Just be careful.

An alternative method would be to fit a GoPro camera on a suitable mount and do it all yourself. You could also use a “flow visualisation grid” with this method, located at a critical point it will show more than just the boundary layer flow.

I hope you get to do more testing and I look forward to seeing the results. It would seem that your test rides have shown some promise but I hope you can find a scientific method for accurate measurement of results.
But heh, a genuine world leader!

The GoPro camera seems to be a lot safer but does require fabricating a suitable mounting bracket sticking out several feet. The authorities may take a dim view of such a bracket. Hope Pete [Ironside] can borrow a GoPro if he doesn't have one already.

-- Teri