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Carbon disk wheel DIY, pancake wheels

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Yanto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 7:34pm
Originally posted by runcyclexcski runcyclexcski wrote:

In that picture, the rig seems too tall? Taller than the cars it is following?


Not sure what point you are making here, it's a motorbike! bike+rider = taller than cars!
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runcyclexcski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 8:58pm
The point I was making is that everything about motorcycle design goes against HPV design points: no streamlining, too tall (taller than cars), etc. Thus, using a motorcycle picture to illustrate the uselessness of 'training wheels' in an HPV design is missing the point, IMHO.
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Yanto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 9:54pm
I showed the picture so you knew what i was talking about when i said i'd seen a tyre scrub in a diamond configuration, there was no intention to compare motorcycles with HPV's just your rabbit hole of diamond configuration.

If anybody has confused the matters and compared HPVs' and vehicles it is you by stating you want the stability of a vehicle, when commonsense shows you can't with a lightweight body of a relatively fixed side surface area, but hey I'll let you crack on and won't comment in future.


Edited by Yanto - 23 July 2017 at 9:55pm
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runcyclexcski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 10:07pm
Ian, please. do not get me wrong, I love your comments, and I enjoy to be challenged. Yes, I tend to explore rabbit holes, but I do not get stuck in them for too long. I come out of them after having learned something.

The closure for today is that I have decided to follow the design points of the Pac Car II (can't go wrong there, I think), and see if I can simplify it. The CAD data are available:

http://www.paccar.ethz.ch/cadshape/index.html

Their transverse cross-section seems to be a slightly squished ellipse, with the longer axis horizontal, rather than a vertical ellipse (like in most velos). This makes sense to me in terms of crosswind stability, and this also seems better than a simple circle.

Once I get their STL file, I will scale the dimensions by ~25-50% to make it roomier and more forgiving for the rider (I am not riding in the coffin position).

Once the approx shape is set, I will use T-slotted Alu profiles to build prototypes. The slotted profiles will let me adjust key parameters, and can also be re-used in my lab and biochem lab for numerous other purposes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 10:25pm
>you want the stability of a vehicle

I merely want a significant (say 2x) improvement of stability in crosswinds compared to existing 'standard' HPV designs, that's all. I drive at 100 mph all the time, and expecting an HPV handle these speeds safely would be insanity. 50 mph, in contrast, might be achievable. I rode my tandem at such speeds in calm weather.

>commonsense

I prefer to look at data rather than using 'commonsense'. Many things in my line of work contradict 'common sense' (or some version of it that was common 100...20 years ago). Quantum physics and imaging with visible light at nanometer resolution come to mind
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoyMacdonald Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 10:48pm
I used to hit 50 mph almost every day on the South Circular riding to the track on the Wasp. I hit 70 mph every time I rode the Wasp in the Darlington time trial. I always found the Wasp too low to be affected by side winds. It was not an issue for me that I can ever recall despite some 30,000 miles riding the Wasp in all weathers summer and winter.
In the Netherlands it is a different because of the vast flat areas without any hedges or trees to break up the wind hence it is more of an issue for the velomobiles I think.
 
You must end up with more side area than the Pac II unless it is to have the same propulsion method, and not be human powered.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2017 at 11:26pm
Roy, yes, I am scaling the Pac II in Autodesk, and I am approximating it with a triaxial ellipsoid in 3D, so it will end up fatter (just like the intended driver). Choosing the ellipsoid b.c. of the simplicity of modelling and materials . The original Pac II was driven by a small female grad student (according to their pics anyway), and was merely knee-high.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2017 at 1:42pm
Originally posted by runcyclexcski runcyclexcski wrote:

>you want the stability of a vehicle

I merely want a significant (say 2x) improvement of stability in crosswinds compared to existing 'standard' HPV designs, that's all. I drive at 100 mph all the time, and expecting an HPV handle these speeds safely would be insanity. 50 mph, in contrast, might be achievable. I rode my tandem at such speeds in calm weather.

>commonsense

I prefer to look at data rather than using 'commonsense'. Many things in my line of work contradict 'common sense' (or some version of it that was common 100...20 years ago). Quantum physics and imaging with visible light at nanometer resolution come to mind


Ok, well i went for a brief ride today, up here on the Wolds it's breezy 16-20mph constant gusting 35, I hit mid 40's mph a few times, didn't even notice the wind.

As for commonsense, well you ignoring it could be the problem, you are trying to crack a problem with science and maths, when you haven't even quantified what the problem is yet, if you have can you explain what "2x improvement" is, because my simple brain can't equate that to anything measurable.  

If you go down the diamond set up you will need 4 wheel steering, 4 wheel suspension, a large frame,  it will as commonsense says have a large frontal area and complex aerodynamic interactions between body and outriggers etc 

Whatever happened to KISS?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2017 at 1:57pm
Ian -- regarding the 2x improvement, it could be defined, e.g.

2x higher wind speed that causes critical yaw angle A.

But since it's all non-linear, different definitions will be associated with different experiences.

In the vehicles I showed only one wheel was steering -- the front one. That is KISS, compared to 2 front wheels steering. How efficient that steering is -- that' different, don't know. The Pulse rocks from one side to the other, so it works, I guess.

Not sure yet, but if the ellipse is squashed up=down, there are no outriggers needed, the side wheels get buried under the wider portion of the ellipse.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlanGoodman Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2017 at 2:04pm
[QUOTE=runcyclexcski] I drive at 100 mph all the time
Shocked
 
On a track I hope?

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