tag:blogger.com,1999:blog-13887692.post2388968631235552643..comments2024-03-21T03:15:06.288-04:00Comments on Cozy Beehive: Ventilation Design In VelomobilesRon Georgehttp://www.blogger.com/profile/18394865788996482667noreply@blogger.comBlogger14125tag:blogger.com,1999:blog-13887692.post-73413572911214658972009-07-04T08:18:36.708-04:002009-07-04T08:18:36.708-04:00I've test ridden a used early Leitra Sport(www...I've test ridden a used early Leitra Sport(www.leitra.dk) velomobile, three years ago in Munich while the last thirds of an summer thunderstorm.<br /><br />I was wearing T-shirt, bermuda shorts and sneakers. Despite the fact that is was condensing wet outside ( ~100% humidity, rain on hot asphalt, plus dropping temperatures) I returned completely dry. Neither rain nor sweat wetted any of my clotes. And ventilation inside is IMO close to the theoretical maximum.<br /><br />Watch this: http://fahrradzukunft.de/fz-0501/0501-02/2.jpg<br /><br />Bubble texts clockwise, beginning at the top:<br /> * scratch-resistant windscreen, as close to the eyes as possible (**), manually actuated wiper<br /> * white colour yields low surface temperature<br /> * adjustable flaps for body ventilation<br /> * easy separation of hood from the frame simplifies transport, p. ex. important for defrosting the hood inouse during winter<br /> * ventilation duct intake for windscreen ventilation<br />(** to avoid distortion of sight due to drops on screen, like in a motorbike helmet, which also has no wiper)<br /><br />what is not on this image - but equally important - is the "chimney effect": the fin-like little tower on top of the is a) a periscope panoramic rear mirror and b) an exhaust ductPeter Fischerhttps://www.blogger.com/profile/05067888365407122808noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-91692080818429931662009-05-23T10:08:28.542-04:002009-05-23T10:08:28.542-04:00I have never ridden a velomobile, but I have run a...I have never ridden a velomobile, but I have run across a number of randonneurs using them, and they seemed to have figured out how to deal with cooling even at slower speeds over very long periods of time. <br />At this link<br />http://www.paris-brest-paris.org/FR/index.php?showpage=680<br />you can search for photos from Paris-Brest-Paris in 2007 by some interesting parameters, one of which is the type of bike. There is a category in the drop-down menu for velomobiles. PBP was cold and rainy that year, not hot, but even still, those riders had to have been prepared for hot weather as well. And they had to have ridden sufficient distances in their velomobiles so as to discover and solve any cooling problems before getting to PBP.Coluber42noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-59226940691369835342009-05-22T14:29:07.557-04:002009-05-22T14:29:07.557-04:00Rene : Possible.Rene : Possible.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-91613870558926343322009-05-22T02:27:57.866-04:002009-05-22T02:27:57.866-04:00Conversely, what if it is cold out and the cyclist...Conversely, what if it is cold out and the cyclist's body heat fogs it up?Renéhttps://www.blogger.com/profile/13903740279774664523noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-56900871170607466102009-05-21T18:26:35.558-04:002009-05-21T18:26:35.558-04:00B nicholson,
Woh.
-BB nicholson,<br /><br />Woh.<br /><br />-BBluenoserhttps://www.blogger.com/profile/03448920726947078281noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-71207795910585659222009-05-21T11:53:39.100-04:002009-05-21T11:53:39.100-04:00Jason : Thank you. I placed a link to the Ansys pd...Jason : Thank you. I placed a link to the Ansys pdf below the post. Its a good read.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-13800944324287350322009-05-21T00:58:54.835-04:002009-05-21T00:58:54.835-04:00Ron, I love your blog. Thanks for the high quality...Ron, I love your blog. Thanks for the high quality content. <br /><br />Here is some information I have gathered pulled from an email I sent. Sorry about the formatting.<br /><br />"Apparently this topic was studied in detail for the Daedalus human powered aircraft. The information below is from the books, "Human-Powered Vehicles" and "Bicycling Science".<br />-Acceptable rise in body temperature 2 degrees C.<br />-Tolerable limit for pedaling [without cooling] is 12 minutes.<br /><br />For the human engine,<br />-Each ml /second of oxygen is equivalent to about 4.5 Watts of power to the legs and 18 watts of heat output(Bicycling Science)<br />-A liter of oxygen is found in about 5 liters of air.<br />-24 liters of air is passed through the lungs for a liter of oxygen to be absorbed.<br /><br />-Each liter of oxygen is equivalent to approximately 5 kcal<br />-The human engine is about 25% efficient.<br />-Air contains 20.9% oxygen, the minimum air required by humans is 17.5%<br />-VO2 max levels of 75 to 83 ml/kg/min represent the top of aerobic power for elite endurance athletes.<br />-Leg ergometry VO2 (ml/min)=W*6.1*2ml/kg/m+(3.5 ml/kg/min*body weight in kg)<br /><br />-A bicyclist producing 450 Watts evloves heat at about 850 W/m^2<br />-For a standing human 850 W/m^2 is absorbed by air moving at 3 m/s<br />-Air currents at 2m/s are up to 16 times as effective for cooling as air currents at .5m/s. Thus, even relatively small amounts of air flow inside a human-powered vehicle fairing can result in significant cooling."<br /><br />From personal experience even with small wheel openings and disk wheels a lot of air is circulated by the wheels (which act as air pumps) But for rider cooling a small duct about 1/2 inch by 2 inches directing air directly over the head provides sufficient cooling at 35 mph and 200 Watts power output. If the vehicle stops moving you overheat rather quickly.<br /><br />There is an hour record speed event in July http://www.recumbents.com/wisil/fordchallenge2009/ and one of the contending teams has done a lot of modeling for cooling http://www.ansys.com/magazine/issues/9-22-2008-ansys-advantage/002-sports.pdf<br /><br />This weekend there is going to be an event in Portland (Human Power Challenge) http://www.ohpv.org/HPC/index.html and the West Coast Velomobile gathering is happening concurrently.Jasonhttps://www.blogger.com/profile/06563663514307802008noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-42999138238888129702009-05-21T00:22:13.353-04:002009-05-21T00:22:13.353-04:00B. Nicholson : Interesting. I thought the whole sc...B. Nicholson : Interesting. I thought the whole script for the Matrix was stolen by the brothers from an African-American woman's SF manuscript back in the 1980's? So what stories did you make up for the movie? If you ever saw the first part, you'll recall the human fetus farm and energy plants. The humans are not born, but grown. The humans are then placed in pods where body heat is derived as a source of energy.Ronhttps://www.blogger.com/profile/16268869622833968439noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-14700450316869509862009-05-20T23:37:27.464-04:002009-05-20T23:37:27.464-04:00Hi, I made up the stories for Matrix I and II for ...Hi, I made up the stories for Matrix I and II for the Wa something brothers, miserable wretches, and I don't remember harvesting fetuses? III? I did the schooling bots bit for that film and little else.<br />I have a Quest (286) velomobile and it is great in the Florida sun, of course I have a www.ElationEbikes.com.au motor in mine and don't have to work so hard. The white color, though, is so bright by the sun that shades are required. I also got the flevobike top (slightly modified) to keep the rain and sun off my head.<br />There's plenty of ventilation for riding around town and you don't get sunburned.B. Nicholsonhttps://www.blogger.com/profile/12001610187304195113noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-19766436218093828652009-05-20T21:15:22.744-04:002009-05-20T21:15:22.744-04:00Reminds of the movie matrix, where the machines ha...Reminds of the movie matrix, where the machines harvested human fetuses for heat energy!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-41908799881028816782009-05-20T21:11:15.490-04:002009-05-20T21:11:15.490-04:00Josh : I see your point. I made a typo. You're rig...Josh : I see your point. I made a typo. You're right. I think I originally meant to write BTU/hr...which I'm more familiar with. So 90 watts of heat production in a human is equal to 307.09 Btu/hr. I'll correct it.<br /><br />Zach : See above for a better perspective. What 307 BTU/hr means that your body can heat up 307 pounds of water by 1 deg F in one hour. This is by definition of BTU. See Wikipedia. http://en.wikipedia.org/wiki/BTU<br /><br />Alloy : Thanks for sharing.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-79844130047618637172009-05-20T19:25:54.347-04:002009-05-20T19:25:54.347-04:00Ron, first off I have to say it's a neat and cool ...Ron, first off I have to say it's a neat and cool little car. I like the idea behind it. However, I have to agree with you. It would not make a good vehicle for long distance drives, especially without some sort of cooling system. But even if it did have a cooling system, I would not want to be in one of those for a very long time because of how cramped you'd be in one.<br /><br />Although I didn't understand half of your scientific explanation, I still think I would have to agree with you. Are you going to get one now?Zachhttps://www.blogger.com/profile/09687161566183295822noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-13681185954748798692009-05-20T19:16:05.517-04:002009-05-20T19:16:05.517-04:00Ron, I thought you might find this article interes...Ron, I thought you might find this article interesting. "The Ventilation of Streamlined Human Powered Vehicles.<br /><br />http://www.hupi.org/HPeJ/0002/ventilation2.pdfalloycowboyhttps://www.blogger.com/profile/14429465662167808264noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-59368140253668161412009-05-20T18:22:49.520-04:002009-05-20T18:22:49.520-04:00First off you can't measure anything in Watt/Hour....First off you can't measure anything in Watt/Hour. Watts is already a measure of energy transferred, if you're dividing by hours you're creating a measure of energy transfer rate rate. I typed rate twice twice.<br /><br />Yes, an enclosed bike is freaking hot, astute observation. This is an enormous advantage for people who are trying to ride a bike when it is outrageously cold outside. This is also one of the reasons that no-one drives one around town.Joshhttps://www.blogger.com/profile/15260298021546690086noreply@blogger.com