Marc S.
100 W
Chalo said:
Why?
Aerodynamics
- Thread starter electr0n
- Start date
Why?
Chalo
100 TW
Because a heavy velomobile is only more efficient than a normal bike when it does not have to work against gravity.
tahustvedt
10 kW
The calculated (http://www.kreuzotter.de/english/espeed.htm) difference between a 20 kg bicycle and a 50 kg velomobile climbing up a 7% hill is about 4 km/h. That's with a 71 kg rider. A heavier rider would probably give a smaller difference. Not as much as you would think. I used hands on the top with wide slicks for the normal bike comparison.
Chalo
100 TW
It is true that most of the handicap a velomobile has is in disabling its rider from making the most of its pedals-- a disadvantage that electric drive does not share. But there is no doubt that a big wide heavy vehicle with three wheels that are free to disagree with each other will be slower both climbing and maneuvering. The aero shell only works for one kind of resistance.
Anyone who has pushed a car on flat ground understands this intuitively. I build pedicab trikes-- the best, fastest pedicab trikes I am aware of-- but they are still trikes, and heavy, thus slow. All the aero improvements in the world would not change that. They would only make the trike heavier and harder to live with.
Anyone who has pushed a car on flat ground understands this intuitively. I build pedicab trikes-- the best, fastest pedicab trikes I am aware of-- but they are still trikes, and heavy, thus slow. All the aero improvements in the world would not change that. They would only make the trike heavier and harder to live with.
Marc S.
100 W
Chalo said:
Current velomobiles weight around 30kg, the latest and fastest models a tad above 20kg. Thats not really heavy.
Chalo
100 TW
Marc S. said:
Apples to apples, please. Bikes made with comparable materials and techniques (and to a comparable cost) weigh in the 5kg range.
Marc S.
100 W
Chalo said:
Well...
From the website of the Milan SL: http://www.milan-velomobil.de/sl_schnell.htm
45.4 km/h at 116.5 watts
50.0 km/h at 134.5 watts
54.8 km/h at 158.0 watts
60.0 km/h at 185.0 watts
tahustvedt
10 kW
Chalo said:
I was a lot weaker on my recumbent bike (Raptobike Low Racer) than on my road bike. But that's probably because I had only trained my muscles on the upright bike. It felt much harder to climb the same hill as on an upright bike. Is that what you mean?
In my comparison I used a road bike with fat slick tires compared to a Quest trike velomobile with added weight to make it 50 kg. The difference both at 350 W and 500 W was only 4 km/h. The difference in power at 18 km/h up the hill was 115 W. The calculator may be flawed, of course.
tahustvedt
10 kW
BTW. I'm in the process of designing my own E-assisted velomobile that'll be larger than the usual bullets, but not as large as an ELF. Hoping to keep it under 50 kg.
Marc S.
100 W
Chalo said:
Why should I compare a velomobile to a carbon race bike? Because of cost and carbon fiber? :lol:
When I did an actual comparison in the ebike simulator, I compared my current etrike to a velomobile. Same motor, same battery.
My Sprint reaches 43.5mph at 18miles range (48Wh/mile), while a Quest would reach about 52mph at a 54 mile range (17Wh/mile). On the flat.
The weight difference would be maybe 10kg.
Kai
10 W
- Joined
- Aug 4, 2008
- Messages
- 86
Chalo said:
Low cadence pedaling (hammering) uphill with recumbent trike is somewhat similar experience to the legpress at gym, in my opinion. Because my back is againts the seat it kind of helps pushing with my feet. On a upright bike you need to also pull with the other leg to get that power. Hamstring muscles don't have the stamina quadriceps have and nonathletes rarely use hamstrings at all
made_in_the_alps_legacy
10 kW
quite a misleading statement "if" you consider the power required to accelerate masses, not only in translation but in rotation tooChalo said:
of course, one might fairly assume that aerodynamic performance are mostly driven by shapes.
LockH
1 PW
I assumed watt was meant was "all else equal". (Points about shapes, rotations... good on ya.)
made_in_the_alps_legacy
10 kW
"ceteris paribus" just because the latin expression sounds funnierLockH said:
Modbikemax
1 kW
I just made a major purchase in Aero. Doubled the cost of the bike. Made in the USA no less by Aerospoke.
I haven't had a chance to put some miles on it but I can say it is very smooth. It should be it cost over ten times the wheel it replaced.
Spinning the wheel at speed on the work stand you don't get the wind noise you get from a spoked wheel.
Plus it looks fast standing still and a lot cooler than a perspex fairing.
I haven't had a chance to put some miles on it but I can say it is very smooth. It should be it cost over ten times the wheel it replaced.
Spinning the wheel at speed on the work stand you don't get the wind noise you get from a spoked wheel.
Plus it looks fast standing still and a lot cooler than a perspex fairing.
Attachments
Modbikemax
1 kW
veloman said:
I did look at a disc. This was expensive but Carbon discs are drug money. Most of them also run tubeless tyres which are glued on which is ok for the track but not road practical, plus they go flat after a day.
There are disc covers which look like crap and for what you get not that cheap either.
Plus old school works and there was a bike shop in town with one in stock, shock
. If I had not seen it in the flesh I would not have bought it.
John in CR
100 TW
Get some of that yellow on the rim and motor...maybe red for the spokes, or most of them black and 5 near parallel pairs in yellow. I don't know, but the bike looks so great, and the checker batt box works, so you gotta do something about the motor wheel.
LockH
1 PW
You GFs getting OT? (Maybe back to orig. subject of this thread. "Aero" plus dynamics.)
Modbikemax
1 kW
John in CR said:
There is a yellow 'Velocity' sticker on the rim. :wink:
I have a black hub motor and a black rim, coloured spokes sounds like a good idea.
LockH
1 PW
Best comment in thread? "aerodynamics play a huge factor in watts/mile"
Chalo
100 TW
My favorite?
That one was worth the most LOLz.
That one was worth the most LOLz.
Modbikemax
1 kW
There is no doubt there are efficiencies to be gained in the wheels.
Quality gear is always worth it. I picked up at least 3kph on my non ebike when I fitted some Mavic aero wheels. You notice it more when you don't have a motor.
Preliminary tests on the Aerospoke wheel (purely subjective) is that it is quieter and smoother which should translate into more k's per charge or higher average speeds.
Flat spokes on the motor wheel would help a lot too but the hub motor does not allow space to get them through the hole and from what I have read the partially flat spokes are no different to the round ones, so duct tape or the stick on discs may be the only answer.
Has anyone tried to fit flat spokes to a hub motor?
Quality gear is always worth it. I picked up at least 3kph on my non ebike when I fitted some Mavic aero wheels. You notice it more when you don't have a motor.
Preliminary tests on the Aerospoke wheel (purely subjective) is that it is quieter and smoother which should translate into more k's per charge or higher average speeds.
Flat spokes on the motor wheel would help a lot too but the hub motor does not allow space to get them through the hole and from what I have read the partially flat spokes are no different to the round ones, so duct tape or the stick on discs may be the only answer.
Has anyone tried to fit flat spokes to a hub motor?
Modbikemax
1 kW
I have just tried something which could be a winner, DIY Aero spokes.
I had an idea and usually they turn to shit but this actually worked and first time. Its so simple I am not surprised someone else hasn't tried it before.
If they have let me know.
I knocked this up in half an hour of messing around so room for improvement but the basic idea is there.
A cut off cable tie inside a length of heat shrink, slip it over the spoke shrink and hey presto. Its quite strong and stable too.
I had an idea and usually they turn to shit but this actually worked and first time. Its so simple I am not surprised someone else hasn't tried it before.
If they have let me know.
I knocked this up in half an hour of messing around so room for improvement but the basic idea is there.
A cut off cable tie inside a length of heat shrink, slip it over the spoke shrink and hey presto. Its quite strong and stable too.
Attachments
tahustvedt
10 kW
I don't think it will give lower air resistance. You have made the spoke even thicker than it was. I use Sapim CX-ray spokes when I build high performance wheels. They are 0.9 mm thick and have an elliptic shape. Even those high performance spokes have little benefit over round ones, and certainly not enough for a human to notice the difference in a scientific test.
Here's a set of wheels I made for my recumbent bike. The pictures show testing with round spokes and a test-profile, a molded fairing, lacing with CX-ray and the finished wheels on the bike. I made molds for the carbon fiber fairing and molded them myself, and used CX-ray spokes. The finished wheels weighed 1400 g. The reason the fairing is slightly wider than the rim brake surface is because the tire is also slightly wider. This is probably what you should be aiming for to make aero wheels, but the simplest and most efficient way to to it is with disc covers, though there are drawbacks if you live in windy places.
Here's a set of wheels I made for my recumbent bike. The pictures show testing with round spokes and a test-profile, a molded fairing, lacing with CX-ray and the finished wheels on the bike. I made molds for the carbon fiber fairing and molded them myself, and used CX-ray spokes. The finished wheels weighed 1400 g. The reason the fairing is slightly wider than the rim brake surface is because the tire is also slightly wider. This is probably what you should be aiming for to make aero wheels, but the simplest and most efficient way to to it is with disc covers, though there are drawbacks if you live in windy places.
