Hemisphere test >:-)

Since low aerodynamic drag is a base of movement in these vehicles, I will post my short study of 15 minutes. This study clearly shows the difference between flat surface vs round surface and reaction in air flow around them. Because the study is not done in scientific manners, I created basic shapes without any details or minor flluctuations on their surfaces, these results are not exactly true offcourse, just giving some quidance of this phenomenon.

The study contains a solid 50cm hemisphere, airflow is 10meters/s and surface is theoretically perfect with roughness of 0. Both hemispheres are equal, only variation is their air flow direction, the other is flat face to wind and the other is round face to wind. The results are: flat face to wind gave 13N of force and round face to wind gave 6N of force, so more than twice of force is generated when flat face is put towards the wind.



Previously made simulation with streamlined body (see previous posts) gave results 7N @ 20m/s, which is nearly the same as 50cm hemisphere but with double speed ! With equation F = ½ s v² A Cv , force of drag will give Cv value of 0.095 with given parameters. But frontal area needs to be rechecked in the process when, for example, the bubble is added. So there is a lot of variables and Cv value is not even close to it's practical and real value.

Mock Up

I totally forgot to show the mockup concept I worked during the summer. It is basically a 2x4 block of wood as a base with seat, BB-support and cranks attached to it. It's not a high tech unit, but it does basic things you need, all can be adjusted and get the quidelines of what can be expected on real thing. This mock up was later totally updated with bigger seat and frame curves along it's shape with accurate measurements which were transported to 3D-program. Previous 3d-model which was made with only few simple not accurate, quideline type of measurements, was totally foolish, and had a bit of a problem to solve it, I even felt "damn,this is going to be sh*t". But as so many times before, I had to think it fresly from the start, with the basics again, and I changed my sitting position closer to the ground and a bit more backwards and few other things and remeasured everything and squeeged all air out of it and shape became nice tube-like form and the overall shape was possible to make very streamlined, and I even got it more narrow and lower. And the most important thing is that I fit inside, into shape that looks impossible and ridicilously small, even unreal, but it's there.

It's funny to realize that only few measurements master the whole design, and there is not much you can do about it, form just pops out from you and your own body dimensions.

I concider myself lucky, and unlucky. For many sports size is not a benefical if it's on the bigger side, that is my problem, I'm on the wrong side. But to be big, at least you can do is to be narrow, and that's what I am. If one is big with wide shoulders and muscular upper body, I wonder what would the vehicle be like, wide for sure, and that is not optimum.

Computational Fluid Dynamics

Playing with my new toy, CFD-simulation tool. Just figuring out what are the things I should and can do, and what I should not even concider.
Because aerodynamics is a whole new world, and you could spend your whole life with searching the right shape, I just kept it simple and created the basic quidelines which to follow. Here is one of the samples I have tested. Forward directional force is aprx. 7 Newtons @ 20m/s, this model is without a bubble.

Wow, my weeks took longer than I expected ;-)

Hi, haven't been here for a while, strange, but that's how it goes. Project, that streamlined bike has not been buried, it's still going, going stronger and with determination, which has never been lost. The whole spring and summer went with training and traveling, skating hasn't been my main goal anymore, it's biking, and only biking. During spring and summer I'v done biking about 12 to 15 hours a week, and that pace should be kept up during wintertime. Only race I took part this year was TdH-2010, which I passed with 4:07, that included one crash and two technical problems, so I'm pretty satisfied for my result, and I'v done racebiking only twice this summer, mainly focusing on mountainbiking, so from that perspective I'm more than happy. MTB is well deserved change to sometimes boring straight paved roads.

Now, rainy weather is here to stay and forces me to stick inside and finally I have some time to put into this project. During summer I do have done something, more modeling, few more new softwares and CFD simultors and virtual wind tunnels have been tested, and some new parts designed including new set of wheels and rear suspension concept and put also some effort into "landing gear" which seems to be quite challenging task, not to mention some new electronics focused only for competition purposes, so lots of stuff in my head waiting to come out some day.
Now, more modeling, final shape is just there, on fingertips :D

Next week and weekend

Next week I should have a packet with some of the items i need to be able to build a mockup of a streamliners basic lines. It would tell a huge amount of information about the whole project, it's measures, my pedaling position and I really get the first feeling of the vehicle. Up to now, everything has been pretty much just an image of the concept, but soon that all will be put into some form. So the next few weeks are really, really interesting.

Until then I'v put my effort into training, this weekend was exceptionally hard. We had a coach from Denmark to put our physical abilities under a test. 16 hours of training, theory, all technical stuff and finally a brutal strenght torture..

Low steering..

Front suspension, well I'v seen them a lot, but not like this. This is a idea that came from center pivot suspension. But instead of using center pivot hub I made one idea of using regular hub and using linear arms to replace the regular fork. This setup would be more sturdy, but because of many joints and bearings, definately will be more heavy, but what ever we wish to accomplish, ther's an idea behind it.

Few words about the design, hub is joined into arms by 4 bearings, and the arms are joined into control arms by aother set of bearings, control arm is joined into frame by bearings. The result is that when the arms are moved back, the other one moves forward, hub turns into desired direction and there we have a steering. I could say this is a low side steering or arm-steering.

Offcourse when upside fork is removed, we loose the upper frame where we can attach the transmission, but instead of putting it into above the wheel, in this idea the transmission is below the wheel, actually on side of the wheel.

Actually Im not sure is this any where good way to build a steering, but one advantage is that it is slim, very low in construction, but probably the heavy side because of the bearings and arms, at least its more heavy than regular upright fork.

Model is very simple, just to test the idea and see what is there to go wrong, and without testing, hard to say anything more about it.

Adjustable cranks

Carbon cranks with adjustment from 150mm up to 180mm. Q factor is 135mm, but easily adjusted by lenght of the spindle. BB is with no threads, and oversized for strenght. Spindle is hollow titanium tube. Spider is integrated. Chainring is with 130mm spacing. Weigh is 1000g including spindle, cranks and chainring, but it's still a solid object so weigh should come down when putting this together in real.

Why?, The reason is obvious, components with decent qualities aren't available, qualities such as lenght, weight, Q-factor, BB's etc. are not packed in one killer-product package, you should have 3-4 cranks, and combine those into one. Thats what is done in here. Adjustable lenght, sturdy BB, simple design, custom narrow, aero.

The cause is the world of standards where bikeworld stands, this is my little tiny snap into it's anxiousness to keep oldish axioms no matter how bad they are in modern standards point of view. Good example is the BB. The thread size and the shell radius is from the age when Adam met Eve. The shell and it's components were good for the use at that time, but today where DH, sick jumps and rude bashing is the use where bikes and it's components are put, shell is ridicilously underbuilt as is the bearings. Even that ISIS is great as a crank attachement, it lacks in BB, bearing balls are smaller than a head of the needle..
ISIS-Overdrive would be a perfect combination of strenght and easyness, sealed concept in a modern size.. but it lacks the support from the market, there are no bikes out there to use the standard, thatway ISIS-OD BB's are not widely available, if not at all. Dynamic bike world, where the wheel is allmost reinvented every year, some things never change.




I ran an FEA analysis to this part, material was 6061 aluminium.