AERODYNAMIC IMPORTANCE!

[briogio]

I've been reading through these forums quite a bit and everyone seems to recognize the importance of aerodynamics. It is the most efficient way to go fast and use less energy. Well the most efficient and fast 2 wheelers ever made were racing motorcycles with "dustbin" fairings and prone position "kneelers". So to this end I propose what's old is new again and a prone positioned kneeler would be "smartest" bike to build as an electric bike and if this bike supported your knees, butt, stomach/chest and elbows I think it could be made to be more comfortable than any regular seated 2 or 3 wheeler. The prone position should not be too "extreme" because that would be hard on your neck, but I reckon 20 degrees would be just about right. Anyway when I saw this picture I was inspired, this will be the direction I go with my first EV, ok maybe my second cause I want to put together a Kona "Stinky" full-sus playtoy!

 

[spinningmagnets]

Since you are posting this in the E-bike section, Here's one of my favorites:

Of course this one is a scooter instead of a bike, but the principles are the same, perhaps search ES using "Vetter" as the search word?

 

[briogio]

You're right maybe I shouldn't post it in the bike section, it just gets the most traffic that's all. Although you could build a "prone" bicycle I'm sure. I like the 2 pictures you put up, but they are just covering the front wheel which I think is only half the answer, being in a "prone" position makes for lower and lesser front end and so less drag, plus it must feel pretty cool in the corners. :lol:

 

[jbond]

Feet first is a lot easier to arrange than head first on PTWs. That Vetter bike is one of my favourite FF designs. I'd really love to see a recumbent bicycle that was streamlined and looked as good.

There's a sweet spot in here that hasn't really been addressed yet. That's a LWB recumbent like a Tour Easy or Bacchetta Bella with a full fairing and a mid mounted electric motor. It should be possible to make it convenient to use but still considerably more aerodynamic.

Here's another pic of an Electric commuter. Amazingly effective, but very clearly home built.

100KWHr Thundersky battery, Kelly controller, Lynch motor. 60mph, >150mile range.

BTW. I run a website for FF motorcycles. There's a few people on there playing with electric as well. http://www.bikeweb.com

 

[briogio]

That's really cool that you run that site, I've had it bookmarked for a long time. I've always loved FF bikes for many reasons, but I just think it would be a really cool sensation to be prone especially in corners, so I want to investigate it more thoroughly. I have a 2000 Ducati Monster that I blew the motor on a few years back and I'm seriously thinking of building it back up as an electric prone motorcycle (just went out to my shop to assess how I would fit, I think I can make it work). I always loved the chassis but the engine was kind of a snore. Anyway I'll keep a picture log and post on the motorcycle section, I agree with you about looking good, mine's gotta and will. I've always built, and ridden, beautiful bikes and I'm not about to stop now! I think I might try and create a clear dustbin fairing because the front end, and Brembo brakes, look pretty sweet. Know anyone who's done anything similar?

 

[knoxie]

Feet first is a lot easier to arrange than head first on PTWs. That Vetter bike is one of my favourite FF designs. I'd really love to see a recumbent bicycle that was streamlined and looked as good.

There's a sweet spot in here that hasn't really been addressed yet. That's a LWB recumbent like a Tour Easy or Bacchetta Bella with a full fairing and a mid mounted electric motor. It should be possible to make it convenient to use but still considerably more aerodynamic.

Here's another pic of an Electric commuter. Amazingly effective, but very clearly home built.

100KWHr Thundersky battery, Kelly controller, Lynch motor. 60mph, >150mile range.

BTW. I run a website for FF motorcycles. There's a few people on there playing with electric as well. http://www.bikeweb.com

Thats Cedric Lynch inventor of the Agni motor and the Lemco pancake style motors, a true EV pioneer! Apparently he was walking around bare foot at the first TTXGP in the pits! which was a bit of a problem for the marshals! :lol:

 

[briogio]

Here's a better picture of what I'm talking about. I'm sure some clever bugger could lengthen the wheelbase and put a bicycle crank on it, if they wanted to. :wink:

 

[Jeremy Harris]

If you google velomobile you'll find a host of really nice streamlined bikes and trikes. They are pretty popular in places like the Netherlands. I quite fancied the idea of building one of the Alleweder kits that are available (http://www.alleweder.eu), although some of the others, like the Mango ( http://www.velomobiling.com/gallery/Velomobile1/Velomobiles/Mango/) look a bit nicer. Most are trikes, but there are quite a few streamlined bikes around, too. The best layout is probably feet forwards, as has already been suggested, which pretty much means a recumbent bike as a starting point.

Jeremy

 

[briogio]

Thing is I've done the recumbent thing, and for a bicycle "prone" probably isn't appropriate (although I did dig up an example). But I'm looking to build a fast and efficient e-motorcycle, and I think it would be a gas to ride through corners in the "prone" position

 

[dogman dan]

The basic problem with prone, or any extreme tuck is your lack of eyeballs on top of your head. It's a problem that I have on my Death Race bike, my handlebars could be lower, but guys that do have em lower are missing corners. I run the seat as low as possible.

Recumbents can rock for aero though.

 

[Hillhater]

There is not much difference in body angle on that last bike, to a conventional road bike with drop bars...an arrangement that has been proven to be effective !
And i doubt you will be able to provide much effective pedal input if you are supported on your chest !

I suspect there is a reason why fast road bikes are either conventional roadies or recumbents !

 

[dogman dan]

Fortunately for roadies, they only need to look at the back wheel of the guy in front of them in the peleton. Riding alone, with drop bars on a commuter, I garantee you will fail to see something eventually and hit it.

 

[Hillhater]

Agreed Dogman, they both have the same problems with vision, but at least the guy on the roadie can breath properly :wink:

 

[jbond]

Fortunately for roadies, they only need to look at the back wheel of the guy in front of them in the peleton. Riding alone, with drop bars on a commuter, I garantee you will fail to see something eventually and hit it.

Err what? As a kid I rode a lot of miles on a drop bar racer. I never had any problems failing to see things.

As for the OP, go for it. Even if you end up with a pretty standard racer riding position, please do experiment with trying to improve the aerodynamics with a real fairing. It's way past time bicycles were properly faired.

I really want a commercialised version of Cedric Lynch's Lynchmobile. I'd also really like a 'bent like a TourEasy with a mid drive and a substantial fairing. And I find it hugely disappointing that 'bents are so expensive and there are so few aftermarket proper fairings for them. I want something as developed as the Velomobiles but on two wheels, not three.

 

[JennyB]

View attachment 1Thing is I've done the recumbent thing, and for a bicycle "prone" probably isn't appropriate (although I did dig up an example). But I'm looking to build a fast and efficient e-motorcycle, and I think it would be a gas to ride through corners in the "prone" position

It doesn't really work as an efficient and practical position for bicycles, though I remember a similar Italian track bike back in the 80's or 90's. There were also good reasons why the dustbin fairing were banned from racing. Something to do with crosswinds on the Isle of Man, I think .

If you'd still like to go ahead, how about an F2 sidecar replica?

[youtube]9--PzwKfkFQ[/youtube]

You could use the battery as ballast so it was ridable solo, go shopping, scare your friends, bring along a genset if you need range... :lol:

 

[John in CR]

Sam Whittingham went airborne for over 100M at about 70mph with his lima bean fully faired bike during a record attempt, and that was in very low winds. Luckily that carbon shell just slid on its side for a long distance after landing, so there's some level of protection as long as you don't hit something solid. I would want some significant battery weight and a properly designed fairing that addresses cross winds, which the old dustbins don't. I know it's possible, but does anyone here know how?

I saw a video of side gust testing of the Monotracer, which showed it self correcting after the side gust. I believe it has something to do with side areas and their position relative to both the fixed rear wheel and steering front wheel.

Achieving high speed on a few kw would be great fun as long as you don't get blown off the road or into the other lane. To give everyone an idea of the potential, the one hour electrathon record is 62 miles, so that's 62mph with a battery that is just under 1kwh, so essentially 62mph on under 1000 watts.

 

[briogio]

Sam Whittingham went airborne for over 100M at about 70mph with his lima bean fully faired bike during a record attempt, and that was in very low winds. Luckily that carbon shell just slid on its side for a long distance after landing, so there's some level of protection as long as you don't hit something solid. I would want some significant battery weight and a properly designed fairing that addresses cross winds, which the old dustbins don't. I know it's possible, but does anyone here know how?

I saw a video of side gust testing of the Monotracer, which showed it self correcting after the side gust. I believe it has something to do with side areas and their position relative to both the fixed rear wheel and steering front wheel.

Achieving high speed on a few kw would be great fun as long as you don't get blown off the road or into the other lane. To give everyone an idea of the potential, the one hour electrathon record is 62 miles, so that's 62mph with a battery that is just under 1kwh, so essentially 62mph on under 1000 watts.

How about swiss cheesing the sides of the dustbin fairing?, to the point where 30 to 50% of the side surfaces were holes. I'm willing to try it

 

[Jeremy Harris]

Sam Whittingham went airborne for over 100M at about 70mph with his lima bean fully faired bike during a record attempt, and that was in very low winds. Luckily that carbon shell just slid on its side for a long distance after landing, so there's some level of protection as long as you don't hit something solid. I would want some significant battery weight and a properly designed fairing that addresses cross winds, which the old dustbins don't. I know it's possible, but does anyone here know how?

I saw a video of side gust testing of the Monotracer, which showed it self correcting after the side gust. I believe it has something to do with side areas and their position relative to both the fixed rear wheel and steering front wheel.

Achieving high speed on a few kw would be great fun as long as you don't get blown off the road or into the other lane. To give everyone an idea of the potential, the one hour electrathon record is 62 miles, so that's 62mph with a battery that is just under 1kwh, so essentially 62mph on under 1000 watts.

The key to cross wind stability is to make sure that the lateral aerodynamic centre is close to, and slightly in front of, the lateral centre of gravity of the bike. Bike steering is set up to self-centre if perturbed; if you push the front wheel to the left it will want to come back to the right, plus our natural balance response is also to lean towards a disturbing force to make any correction. This means that you want the bike to respond like this to a gust - the gust must act to turn the bike away from it, so that you have a natural response to making the steering/lean correction that's required. If you fit a fairing with a large lateral area behind the centre of gravity (i.e. a tail fairing) it will significantly reduce form drag, but will move the lateral aerodynamic centre aft, behind the lateral centre of gravity. This will make the bike feel unstable, because a gust will make the bike want to turn in towards it and lean away from it at the same time, a very uncomfortable thing to try and correct.

The easy way to fix this imbalance, whilst keeping all the advantages of a tail fairing is to move the centre of gravity aft. Another thing that helps is to use the effect discovered by Karman and used by Cedric Lynch on his streamlined bike, and just cut short the tail fairing. This isn't quite so efficient as a long tail, but the vortices shed from the bluff end will create a stagnation zone right behind it, which effectively lengthens (aerodynamically) the fairing, but without presenting any increased side area to cross winds. The same technique is used on a lot of modern cars (often incorrectly referred to as rear spoilers) for the same reason.

Adding lateral area at the front to balance the bike is another option, but means increasing wetted area. As air is viscous (i.e. slightly sticky) anything that increases the total area of the fairing will increase the drag slightly.

Finally, you also need to consider the forces acting in the normal axis (i.e, up and down). If the curve over the top side of the fairing is greater than the curve over the lower side of the fairing, when looking from the side, then it will generate lift. This may create handling problems at high speed with the steering going light. Going the other way, and having more curvature on the lower side will generate down force, but too much will increase rolling resistance at speed and adversely load the suspension.

Jeremy

 

[wojtek]

anyone has experience of building an e-velomobile?
I have opportunity to buy used Allewender FAW at quite good price... I reserved it now!

http://www.2dehands.be/fietsen/fietsen/ligfietsen/alligt-alleweder-faw-velomobiel-86926613.html?qq=Faw&pcpl=&list_cat=ligfietsen&pc_id=&afd=fietsen%2Ffietsen%2Fligfietsen
they also have Allewender A4 but recommended more the FAW one...

I was thinking to use hub motor. Maybe BMC V3 as i think with this aerodynamics it is important to freewheel.... But then it weights around 31-35kg without battery - quite heavy. Incl battery and myself and some other extras, it would weight 120kg... Going up the hill [18 degree or more] BMC might struggle.

Jeremy - thanks for great info on the wind issue - when exactly do you think would be the best place of placing the battery in a velomobile then?