engineering my second recumbent motorbike
 

it was born because of the quest for a fuel efficient variomatic recumbent motorbike, my recumbent version from a chinacopy hondabike with a 150cc honda dylan drivechain.........

the second one, wich will be much more fuel efficient, is beeing created in 3d at this very moment. my variomatic recumbent is now relaxed doing every refill above the 100MPG and that's good enough for now. no more effort will be put in the variomatic becouse you don't want this type of gear for fuel-efficiency. the rubber frictionbelt is nice to drive but taking too much power to use.

the next one will be a 125 ( or less ) fourstroke with a maximum of gears, a full streamline wich will be engineered and tested before the built will be started. progress will be posted !


greetings from a very wet Netherlands,


abel

What do you think about the sidewind effect on a full fairing two wheeler? Is a full fairing dangerous on two wheels?

maybe when there's a serious wind.

i've driven it with 5 beauford and sideways it's a bit wobbely indeed, nothing i would get afraid of. my BMW R1150GS has a much bigger frontal surface and that's why it's far more scary when you hit the wave of a big truckload in the other lane. my recumbent does nothing with these 50 tonners ( KG ! )

sidewind reaction due to wind only is a bit more because of the fairing, i will work on the side-surface to get some less effect but it's allways going to stay a bigger surface then a naked bike. also it's a very light motorbike what's not improving the stability.

i'll keep you informed what hurricane i can take and when it's really getting suicide to drive.

:D

Sounds interesting, Looking forward to some progress reports. Side winds on motorcycle, and other 2 wheeled vehicles are always a source of contraversy, as I suspect you are aware there are both successful designs and the other kind. I keep thinking about a three wheel recumbent with a 50cc honda motor but the list of projects is so long that it may be years before I am able to get to it. In Canada it would be classed as a bicycle and thus no insurance and registration, a great grocery getter.

Craig Vetter stopped his MC economy competition due to worries over crosswind safety. His current experiments employ ballast in the nose. Extra side area is never good in a crosswind, but the effect is much worse if the shape works well as a wing. I'd use a fairly abrupt transition from front to side, to have the shape stall at low side force, and other variations to keep the stall from being abrupt.

An other consideration with respect to side winds is to make sure that the center of pressure is behind the center of gravity so that the bike tends to turn into the side wind. This can be achieved by extending the bodywork beyond the rear wheel, as well as redusing the side area infront of the front wheel. In the 1950's there where many attempts at full streamlining in racing; as you are probably aware, some succesful with repect to side winds others not. Vetter reports in his website that his 'freedom machine' last vetter fairing, is no worse than other motorcycles and on the whole quit managable. Keep up the good work. 'I have a dream that one day...' we will all be riding 100mpg [2.3L/100km] motorbikes that can still do 200km/hr...

His bike is also very tall, compared with what AMDparts wants to do. Begin to reduce the rider's height as much as comfort allows, and then, instead of approaching a teardrop cross-section shape that has sides perpendicular to the ground, try using the uppermost profile of an airfoil, with a more domed front profile a la VW 1L. The "hump" profile in theory should nudge off any sidewinds, and the low center of gravity wouldn't allow much of a loss of control anyway.

Looks great! :thumbup:

The best cure for sidewind after making sure the CG is ahead of center of pressure is downforce, especially on the front wheel. The bottom profile should be more curved than the top and the cross section should be an elipse. The angle of attack of the whole body would be nose down. With a recumbent the rider's weight is more to the rear than an upright so a longer tail is needed. See the Aptera shape developed by Dr. Alberto Morelli. The engine should be as far forward as possible ala the Gurney Alligator and a long parallel link swing arm for the rear suspension.

hi grand,

i have to react on one thing of your post;

the sittingposition i have on my first proto recumbent motorbike may be totally different from the scooter it has been, the weight destribution is even. in my case there is no more pressure on rear or front wheel then with the original sittingposition. i have checked it.

the longer tail may be better with sideways pressure, it will do seriously negative in drag. when you minimize the surface of the rear and loose the air earlier the drag will be reduced a lot. that's why this VW 1L car or a speedboat's tail is this short.

abel

Grant-53 The moment you mentioned using down force on the front wheel i thought that sounds like a good idea why didn't I think of that? so thanks I will look into that idea some more.

It helps to live within 50 miles of the National Soaring Museum, the Glenn Curtiss Museum, and the International Motorsport Library at Watkins Glen, NY... :)
As for the long tail vs Kamm back, the surface drag of a long tail is more than offset by the reduction in drag induced by turbulence and separation. There are lots of good books and articles available that explain this in detail. I use my old college text on fluid mechanics and Dr. Joseph Katz's book "Race Car Aerodynamics: Designing for Speed".
The interactions with side wind and the lean angle of a faired recumbent will take a good bit of thought and testing to optimize. Some air will go under and some will spill over the top. Reduce side drag and try to minimize lift, again rounder on the bottom and flatter on top. My boys want a home made wind tunnel for a science project and I have some models to test. My fairings on an upright bike come only to the knee and are round cones at present. Cross winds have had little effect.

Thanks, Grant. The VW 1L is truncated for compactness, not drag.

Another way to reduce side force is to just arrange for vent flaps to open, defeating any pressure differential. It is unfortunate, but as long as the air stays attached, you can get an actual boost from a side wind, but if you have to spill it to reduce side force, even the drag goes up.

AMDparts In looking at your yellow recumbent bike I see one area you have neglected and that is the underside of the bike beween the wheels. What I have done on my bikes; and recomend you do is to install a underbody that goes from close behind the front wheel to the centerstand then cover the underside of the centerstand. this may improve FE by 5%. I use 2mm aluminium for my street bikes and 3mm aluminium for my duelsport bikes.

Downforce or Sideforce?
 

The trouble with wings on a tilting vehicle is that they wind up pushing you to the outside of a turn. Downforce affects traction, but won't help with basic directional stability.

hi redyaris, i've done that this week. the bottomside of the frame is covered with 1.8mm PMMA plating. a cheap way of cover and with some heat you can form it the way you want it.

the bottom of the nose has had a cover also , and the sides of the nose too. those forms i'm making better at the moment. i think it's working quit well, my fuel-log wil show it soon...........

I do agree that wings are a problem for single track vehicles, however BMW does add down force on the front wheel of the 1988 - 1993 K1 to counter-act the pitch moment that reduces the down force on the front wheel of most motorcycle as speed goes up. The fairing of the K1 is designed to add a messured amont of down force on the front wheel. The K1 fairing is one of the few that was developed with aerodynamics in mind, and in fact it has one of the lowest drag coefficiants of any production bike [see chapter 10 of Hucho]. If I am not mistaken Hucho also mentions that some down force on the front wheel can in fact help basic directional stability. Motorcycle aerodynamic design is alway problematic in that ...some may be good but more may not be better..., I suspect that this is the case with downforce on the front wheel. Although some work has been done to generate downforce on the wheels of a racing motorcycle, to incrrease traction and cornering speed, the systems proved to be overly complex and no one has ever gone beyond the prototype stage. ;)