Recumbent - Aren't recumbent bikes inefficient?

Air resistance increases with the square of speed, right?

Yes, in general, relative to the same bike and same condition.


Please cite where I claimed to "blow past" anyone.

You got me. I was reacting to Janmm's brief comment, not your explanation.


Interesting you mention "drops and tucks". Another possible efficiency advantage for some recumbents is that the riding position by default may offer somewhat smaller frontal profile.

Frontal profile is not as big a factor as streamlining. I took a fluid mechanics course in college, which covered many aspects of aerodynamics. One of the impactful examples I remember was comparing the wind resistance of a 10' diameter sphere against the wind resistance of a 1' cube. The sphere had much less wind resistance, even though it presented a much larger frontal profile.

When I used the calculator you pointed out, I compared an upright in-the-drops against a SWB recumbent similar to yours and the coasting speed difference was 0.1 mph. The real recumbent advantage begins showing up when you compare all-out upright racing configurations against racing configured low recumbents. I wouldn't want to spend a lot of time riding for pleasure on any all-out race configured bike, whether its recumbent or upright.

This whole discussion is purely academic and has no real relevance or value. Why are we even trying to "prove" advantage of one against the other?

Bob

This whole discussion is purely academic and has no real relevance or value. Why are we even trying to "prove" advantage of one against the other?

Bob
I think we are just trying to "prove" that recumbents are not INefficient since that is what the OP claimed.

The right answer is that recumbents and DFs each have several advantages and disadvantages unique to each design. There is more variety in recumbents as it is less constrained by rules bodies. Choose the bike that suits your purpose for riding, your desires and your body.

Please give us a report if you get a raptobike!
Mark
I certainly will. It will be my 40th birthday present to myself :)

I think we are just trying to "prove" that recumbents are not INefficient since that is what the OP claimed.

The right answer is that recumbents and DFs each have several advantages and disadvantages unique to each design. There is more variety in recumbents as it is less constrained by rules bodies. Choose the bike that suits your purpose for riding, your desires and your body.

Oh, yes. You are absolutely correct. Now I remember. Heck no, recumbents are not inefficient. What's really inefficient is a beach cruiser bicycle (I can hear the stones being cast my way now). My wife rode a really cool looking Townie bike for a year. She even did a 35 mile ride on the thing. It was candy red with white trim and a big white seat and white rack. But efficient? Raspberries on that. It served its purpose and we had fun. But when I got my carbon road bike, she said I was riding one of those "cheater" bikes and she wanted one, too.

I think recumbent bikes, in general, represent the tenacity of a few individual designers who worked with it until they got some good designs and were able to commercialize them.

The title of this thread should have been "Are recumbent bikes funny looking?". Well yes, they are very funny looking. Then we could start another thread "Are cyclists funny looking?" and that would have to be a resounding "Yes, they are hilarious".

There got to be so many of us that nobody laughs any more. I live in Texas and ride in the country a lot. Even the local ranchers have begun to look at us as "normal".

Bob

Who you callin' funny-looking?

http://i189.photobucket.com/albums/z284/JanMM/goodlookin-2.jpg

When I used the calculator you pointed out, I compared an upright in-the-drops against a SWB recumbent similar to yours and the coasting speed difference was 0.1 mph. The real recumbent advantage begins showing up when you compare all-out upright racing configurations against racing configured low recumbents.



http://www.kreuzotter.de/english/espeed.htm

Hmmmm, not sure which bike you selected similar to mine...

Using the defaults, for 160 watts input power, I get 19.3 mph for racing bike on drops and 21.3 for SWB "racing equipped" over seat steering. For both bike types, this is based on the same tire type. Also note, the SWB modelled is a 20"x26". There's no selection for 26"x26" high racer. The upright bike is 5 lbs lighter in the model... Tle unfaired low racer calculates to 23.3 mph.

For a coast down on a -5% slope, I get 38.6 mph for SWB OSS, and 31.6 for racing bike on drops. Keeping the bike weight the same makes the SWB 38.1 mph...

I have a a Tour Easy LWB with front fairing for my touring bike. It is more "streamlined" but larger frontal profile than my high-racer. Not sure which may be more aerodynamic. I can't really do a fair coastdown test since the tires are different (medium touring vs. narrow high-pressure) and the Tour Easy weighs maybe 8-10 lbs more.

As for why the comparison of efficiencies, I thought that was the thread subject. %^)

Jon

From what I have read, a front wheel drive low racer, made out of CF, with high end components, and a full fairing is very efficient. ;)

From what I have read, a front wheel drive low racer, made out of CF, with high end components, and a full fairing is very efficient. ;)
You don't even need the fairing. A tailbox helps a ton.

I am sorely tempted by the Raptobike low racer (http://www.raptobike.nl/lowracer.php). The price is quite reasonable (roughly half the price of competitors) for a low racer and it is well made. Heck it is cheaper than its competitors frame sets. My goal for 2009 is to get one of those and kit it out nicely. Should be a lot of fun.

More power to you if you can go up a 40-60% grade. I am not capable. Where do such grades exist?

Just a couple of short ones. One is on an old road leading to the local college, a short section of ludicrously brutal hill. That one is going away with the next road upgrade. The other one exists along the MUP that duplicates the freeway at a piece of geometry that the builders just couldn't avoid, yet couldn't think to justify earthmoving to erase. Neither section is longer than 10m or so, but they're still pretty noteworthy when you hit them and go 'oh dear gods what were they THINKING, eek, i'm spinning out on this damn thing.." I can go up Moose Creek Hill with no trouble, and that is commonly considered to be about the outer limits of what the road designers tolerate in my area.
I do know of a place where there is a grade in excess of 80% on a public road, a gravel road up the side of a vertical cliff that was platted in a nearby town either sight unseen or liquor-enhanced. Speculators bought the land on the other side of the cliff and sell it online, and cut the road out as much as was feasable in order to claim that it was accessable by road. It can't be flattenned any more without a tunnel or full-take buying both adjacent properties.

I do know of a place where there is a grade in excess of 80% on a public road, a gravel road up the side of a vertical cliff that was platted in a nearby town either sight unseen or liquor-enhanced. Speculators bought the land on the other side of the cliff and sell it online, and cut the road out as much as was feasable in order to claim that it was accessable by road. It can't be flattenned any more without a tunnel or full-take buying both adjacent properties.

You must live in a place where the road designers are more than liquor-enhanced. :lol: I can't even walk up an 80% grade without spinning out - and that's without a bicycle.

Bob

80% is technically rock climbing not a road.

As a retired highway engineer, I assure you that 80% road grades don't exist, nor 40%. Possibly 30%, but I've never seen one.

For a fun experiment, park your car on a 20% grade (uphill or down) and try to exit the car without breaking your leg if parked uphill or bending the door hinges if parked downhill. Of course it can be done, as I'm sure people in SF know, but be careful. :)

As a retired highway engineer, I assure you that 80% road grades don't exist, nor 40%. Possibly 30%, but I've never seen one. :)

I thought the numbers being tossed out were a bit on the exaggerated side, but I didn't have the knowledge to say otherwise. I always thought a 10-15% grade was really pushing it on a bicycle.

Bob

Put a level and a ruler on those sections, measure carefully, and let us know. I will bet that the grades are not what you think at this point. Mark

You must live in a place where the road designers are more than liquor-enhanced. :lol: I can't even walk up an 80% grade without spinning out - and that's without a bicycle.

Bob

As i've been led to understand, grade is the number derived from the fraction of vertical/horizontal. A 100% grade would be 1/1, 1 meter of rise for every meter forward, a 45% angle.
I probably don't have the exact grades, but the ones that cause me to spn out are in the vicinity of 30 degrees; the one on a cliff is very close to a 45 degree angle, and when my father was showing it to me, w had to lean forward on the 6wheel ATV we were into make sure the front wheels wouldn't come off the ground.

Hills look worse than they measure. A 45 degree hill (100% grade) is not traversable.

Hills look worse than they measure. A 45 degree hill (100% grade) is not traversable.

We were barely able to traverse it on an ATV.

Recumbents have been banned from UCI competition since 1933 because of their proven "unfair" aerodynamic advantage! When I got my first Tour Easy 25 years ago I thought that maybe I had made a mistake. It only took me about 3 miles to get comfortable and realize that no...I hadn't made a mistake... unless you consider my obsession with bents for the past 25 years a mistake. I still ride my 25 year old Tour Easy daily even though I have quite a stable of bents to choose from. I still get comments on a daily basis such as: COOL BIKE! It just never seems to get old and it certainly is fun to ride. It is also fun to take your traveling lawn chair to public events as parking is never a problem and you are always comfortable. If you are into performance, it can certainly be had with the right recumbent(I also have a Gold Rush with a fairing and body stocking). If you want dependable transportation and exercise I don't think you can do any better then the right recumbent. If you want to tour the comfort is undeniable and what better way to start a conversation and meet new folks then to respond to someone calling out "COOL BIKE"! One thing I would steer clear of is those chopper looking things with the wide rear wheels and single speed and a harley type seat. They weigh a ton and even though they may look like a recumbent I don't believe that they are. Unfortunately I see a lot of kids riding or shall we say trying to ride those crazy things. Most of them don't look to happy. They may be giving recumbents an undeserved bad name. BENTS RULE!

The worlds steepest paved road is only 35-38% so the grades you are quoting are not correct.
This may help.
http://www.1728.com/gradient4.gif

http://farm4.static.flickr.com/3278/2300851157_4967bed58b.jpg?v=1212558882
Baldwin st NZ, 35% grade

BENTS RULE!

You tell 'em, Rodney!

I'd say that it depends on the model and the rider. In my case, the model is more upright, and I sit in it in a way that resembles a Harley rider. That is way less efficient than the laid down riders, who can hit speeds that rival or beat cars in some cases. But I'm not going out for a speed competition out on some lonely road in Nevada. :lol:

I'm also a slowpoke rider. I ride for enjoyment, even when I commute.

...So the whole d--- thing is inefficient in my case. But I do enjoy it.

Your post would have had a lot more credibility if you hadn't shown such an obvious bias through emotional exaggeration in your description. Its BS to talk about a particular bike design causing the rider to miss a pothole so big that it results in flying over the handlebars. That's riding with your head in a dark spot.

Bob

It wasn't my post, but I feel the need to respond. My wreck a few months ago was partially attributable to the fact that I couldn't see what was coming under the front wheel. I did not fly over the handlebars; due to positioning, I flew right into them as they spun around again and again, stabbing me in the breasts and abdomen. No head injuries, but I still had to go to the ER to check for abdominal injuries.

That didn't stop me from riding the bike, by the way. It just made me more aware of potential hazards and the overall handling situation. It is just different.

> and bents balance mostly by steering

Not in my experience. Above "stall speed" balance is mainly body position for me. With experience, steering input becomes less necessary even at stall speed and stall speed becomes slower.



It's all about the lean. It's like a motorbike. You still use your body. You use it a little differently, just like crotch-rocket riders lean differently than Harley riders...and face different hazards.

http://farm4.static.flickr.com/3278/2300851157_4967bed58b.jpg?v=1212558882
Baldwin st NZ, 35% grade

Thanks for posting that picture. Many riders would look straight up a grade like this and swear it was at least a 60 degree angle, not realizing its closer to 20 degrees. Appearance is deceptive.

Bob

It wasn't my post, but I feel the need to respond. My wreck a few months ago was partially attributable to the fact that I couldn't see what was coming under the front wheel. I did not fly over the handlebars; due to positioning, I flew right into them as they spun around again and again, stabbing me in the breasts and abdomen. No head injuries, but I still had to go to the ER to check for abdominal injuries.

That didn't stop me from riding the bike, by the way. It just made me more aware of potential hazards and the overall handling situation. It is just different.
Were you riding an electric recumbent that is pretty upright? Your description sounds like it. When you add more than human power to a vehicle than its handling and dangers change quite a bit. It sounds more like the dangers of an electric vehicle not engineered for safety than a bike.

Were you riding an electric recumbent that is pretty upright? Your description sounds like it. When you add more than human power to a vehicle than its handling and dangers change quite a bit. It sounds more like the dangers of an electric vehicle not engineered for safety than a bike.

Yep, it's electric, but I'm limited to 20 mph and was going about 15 mph at the time of the wreck. The "speed" contributed to the overall force of things. Nonetheless, I still can't see right ahead of that front wheel unless I lean up--at any speed.

Realize that I'm not dissin' the bents. I'm just saying that the set-up and hazards are a little bit different. I've flown over the handlebars on my upright before, so I know those have their hazards, too.

What brand of bike are you riding? Can you tell us a little more about your bike? Recumbents are much more varied than DFs, something that is true for you on your bike probably isn't the case on another recumbent.

What brand of bike are you riding? Can you tell us a little more about your bike? Recumbents are much more varied than DFs, something that is true for you on your bike probably isn't the case on another recumbent.

It's one of the Sun bikes, which does, indeed, position me a little differently than you are positioned in your picture.

Yes, if you are on a Sun EZ1 or something similar then your feet are in your LOS to your front wheel. You are very upright as well. Most recumbents are not as closed as that position.

In my case on my Corsa, Vivo and my trike, I have full view of my front wheels as well as an unobstructed view of my forward POV. I don't think it would be possible for me to get smacked around as you did in your accident on my three bents.

I ride a Cruzbike Silvio. I am not scraping the ground so safety/visibility is excellent. It also takes all standard road bike components... standard 700c road wheels etc. I don't feel any loss of efficiency on it. The riding position definitely helps aerodynamically and against the normally annoying headwinds.
Harold

The worlds steepest paved road is only 35-38% so the grades you are quoting are not correct.


Right- originally claimed as 38%, but then re-measured & found to be only 35%, possibly making Canton Ave. (http://flickr.com/photos/42328960@N00/158109519/) in Pittsburgh (http://www.post-gazette.com/pg/05030/448976.stm) the steepest at 37%.

There's a hill-climbing bike race (http://www.youtube.com/watch?v=lEzlWcWhFyU) that includes it.

Oh, & here's a recumbent attempting it (http://www.bentrideronline.com/messageboard/showpost.php?p=428147&postcount=30) (where I first heard of it).

http://lh6.ggpht.com/_4BVh5p_7LEs/STHjtIPgjiI/AAAAAAAABto/SWmsQlYGU2s/s800/09_canton_ave_DSC_0109.JPG

I've been riding my P-38 SWB recumbent for 1 year now. It took me 3 months to get used to what I can do the bike. I cannot climb a hill as agressively as I did with an upright because I cannot stand on the pedals. I fly downhill much faster than ever before (passing upright bikes all the time). On flats I can ride close to my speed on an upright. My real comfort came when I stopped caring about speed and AVS and just started to enjoy the road. My 45 mile ride used to take me just over 3 hrs. Now I don't care if it takes 4! I relax more and enjoy my ride more once my perspective has changed. I have a constant recumbent grin on my face. Why should I care about speed when riding is more fun than ever before? My advice is forget speed and spend more time in the seat (saddle) with no aches, pains, and worries. Enjoy the thrill of the ride. You can also take in much more of the scenery from a recumbent.

The year I started riding my first recumbent, everyone discovered that I was unbeatable at longer distances. I wasn't faster on the road, but I NEVER STOPPED. If they took so much as one butt break, they'd never see me again. Now that I have a lowracer, they haven't got a prayer of keeping up if I get happy feet.