Fan Scroll housing

[RichBinAZ]

I suppose the pandemic creates idle hands, so I've been busy again making something that would stop the curtains in my bedroom from swaying around and also hopefully deflect the air at me for cooling.

This time I made a scroll housing from compressed paper board (cereal boxes, beer pack boxes) wood glue and tape. I did no calculations ahead of time, just made a 180 degree scroll starting at 2 inches finishing at 5 inches tall, extending past TDC by 10 degrees and to my surprise it works nicely. Giving a nice breeze at roughly neck/chin level, even at low power levels. In the video I'm pulling 1 handed at 30W

Another youtube video.
https://youtu.be/dvqM8gfpxK8
If you want, I can do another video to show how I laid out the shape on the boxes as it is a little complicated and required "math"

[mict450]

Very ingenious!!

[RichBinAZ]

Did a row today and the scroll provided enough of a draft that I didn't have to use a separate fan to keep me cool. I may make a little extension to aim it down into the body a bit more.
I was rowing at around 125W, pumping it up to the 200W range doesn't seem to increase the airflow that much, rather it provides a narrower jet of air. Did a few pulls over 300W just to see if the scroll would blow off and it stayed put.
It does not seem to affect the PM5 calculator, as the avg power/time result from this 12K row seemed typical to other 12K rows I've done. Both in the numbers and seat of the pants feel. So all the drag calcs seem to end at the perforated band.

[jackarabit]

Very nice! Cheap and cheerful CBreeze. Reminds of my personal fave— the Blojack.

[RichBinAZ]

Neat, had not seen the Cbreeze before.
and as for drag factor, my newbiness is showing.
Perhaps drag factor is something that should remain a mystery to me.

[Citroen]

Perhaps drag factor is something that should remain a mystery to me.

https://www.concept2.com/indoor-rowers/ ... etting-101

Lever position, dust and elevation are the most significant things that affect drag factor.

[jackarabit]

So all the drag calcs seem to end at the perforated band.

My experience with my home-brewed deflector installed was a drop in df against df without. It appears that a flow restrictor (back pressure) on the exhaust acts to produce an effect identical to that produced by closing down the valve/shutter on the intake. Seems counterintuitive but that was my observation. Certainly Concept 2 promotes the view that power/pace calc is independent of df.

[RichBinAZ]

Just had a look at the drag factor in the logbook, for the first time, on recent rows and it looks like the scroll drops it by about 10-15 points on average (6%). DF seems to be fairly variable, probably because I have to reset the lever after the wife has rowed & I suspect I never get it to the same spot.

Still, the cooling works well and it encourages me to shorten the breaks to get the cooling effect back.
Plus I'm not running a separate fan so less co2 into the air??

[RichBinAZ]

I made another video showing how to layout a segment of the scroll. The initial part of the scroll is fairly straightforward, but the other bits are tricky. Which is the point of this video. So if you need a bunch of cooling to blow away the sweat, here's a fun project for you.
https://www.youtube.com/watch?v=DfeXKF-uJWw

[Cyclist2]

I like the math behind it. Thanks for providing that. I've done projects where I needed a certain shape (cone for a model lighthouse top, for one) and couldn't find a ready made piece. Dig out the math book and build it myself. I'll bookmark your YouTube and this winter I'll give it a try.

The only thing I'll do differently is use one big piece of cardboard on each side, rather than all the segments of smaller pieces, but I guess you enjoy the math a little more than I do.