[python] Re: Intro
- From: "Paul Bell" <paulb@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Mon, 17 May 2004 11:35:59 -0400 (EDT)
Hello All!!
Well I am a bit slow to respond to this letter but I thought I would take
the time to read thru all the archives to help answer some of my
questions. I also tried to read up a bit on wheel sizes but I am still a
bit confused. I went to an American high school in Bermuda because my dad
was in the service. Now I am so used to Imperial measures it is going to
take a while to break the habit ! Plus I think the wheel sizing is/was a
mess ha ha!
One thing I find ironic is the one design that really catches my eye, the
Python, seems to be designed for the taller rider and with no fairing. I
am not tall at all at 5'4" and I was really hoping for front fairing and
an areo tailbox as a minimum.
OK, that being said, onward with the design challenges :)
My number one question is related to wheel size and hinge angle. Since I
am short, with an inseam of less than 29 inches/ 73.5 cm, I have no choice
but to use a smaller front wheel. I am assuming that a 20 inch wheel /
406mm (is this correct??) will make a good front wheel. I currently have
two new 26 inch by 1 inch wide (559mm ?) rims with disc brake hubs that I
would like to use. Looks like I might be able to use at least the rear
one.
So any comments on using a 26 inch/559 mm rear wheel with a 20 inch/ 406
mm front wheel ? If in disscussion people feel that both wheels should be
the same size then I will just have to purchase a 20inch/406 mm (or about
this size) wheel set.
As far as hing angle goes, I would like to be in the range of 65 to 70
degrees. Should this angle be measured from the horizon or from a straight
line thru the two axles of the front and rear wheel.
I would also like to keep the hinge as close to the front wheel as
possible due to my short legs. I believe it will give me more
adjustability for comfort in relatiion to the cranks.
On the subject of cranks, should the hinge, front wheel axle, and the
cranks be more or less in straight line with each other or can the crank
be lower or higher than a line drawn from the hinge thru the front wheel
axle?
Lastly, is about wheelbase. If I go with two small wheels I could end up
with a very short wheel base. Any more comments on wheelbase to add to
what Michael said about long wheelbases turning into a twitchy bike with a
turning radius of a supertanker??? (what an odd combination and I could be
wrong on what I just said, If so sorry Michael :) )
I think once I decide these three things I will be able to start a drawing
and get on with building. I will worry about adding a fairing and hand
assist after I master riding a prototype model :)
I will probably stick to a wood frame unless some guys from the local HPV
group convince me to make one from some scrap frames :)
My idea for a fairing will be this. If you can image a tear drop shaped
fairing mounted to the back frame only. The front bubble of the fairing
would stick out over the nose long enough for foot and crank room. This
will leave the front half of the frame free to move. It will not be in the
wind stream so hopefully this would work. Altho I see that a gust moving
the the fairing would cause the bike to turn ! Maybe !!!. Anyhow,
something to try after right?
Cheers to all and thanks again for the help so far :)
Paul Bell
P.S. I am c.c. this to my local HPV list and I think we have some interest
there in the Python as well : )
> Hello Paul,
>
> I have very little experience, but I can share what I've read online.
>
>> I am pretty good with wood and have a Cabinetmaking college degree and
>> some tools. This means I have an interest in making some parts out of
>> wood
>> :)
>
> You've probably seen some of the websites devoted to wooden recumbents,
> if not, Google around, there are some cool designs.
>
>> Do you think the bike would be drivable with hand cranks?
>
> The thing to keep in mind with the Python is that there are very few
> experienced pilots, so there are many unknowns. So although I would
> love to build a totally customized Python, I've decided to start with
> the standard design (P3), see if I can learn to ride it, then start
> design my dream Python. But obviously you are free to do as you like,
> and I am hardly "the voice of experience", in fact, quite the opposite!
> I just read and think a lot.
>
>> I was thinking of making the fairing partly out of cedar strip's like a
>> canoe as I had all the tools and bits to do this and it seems like it
>> would produce a fairly light, but strong fairing. I think it would
>> possible be strong enough to actually be the main part of the frame.
>> Any
>> comments on this type of construction?
>
> The fastest bike in the world (the Varna Diablo, piloted by Sam
> Whittingham) has a carbon fiber monocoque frame, so your bike would be
> in good company! It was in 2002 that the Varna Diablo exceeded 130 kph
> (81 mph!), and in 2003 they set a new record with a 1-hr average of
> 83.71 kph (52.3 mph!).
>
>> I am pretty short at 5"4' and my in-seam is around 29 inches. This
>> means
>> that using a 700c front wheel like I saw on the YPE web page is out. I
>> think I will have to go with a 20" wheel(sorry not familiar yet with
>> all
>> the metric sizing for wheels)
>
> For a good primer, check out Shelton Brown's article on tire sizing:
>
> http://sheldonbrown.com/tire-sizing.html
>
>> I am also curious how pedaling affects the riding of the bike.
>> Can you make a long wheel base model and have the cranks behind the
>> front
>> wheel? and what problems does anyone for see by making a longer
>> wheelbase
>> model?
>
> One thing to keep in mind is that as the wheelbase goes to infinity,
> the hanging pendulum effect disappears. I assume that would make the
> bike very twitchy.
>
>> Keep in mind I would like to make a fairing and will need high speed
>> stability.
>
> You may have seen this already, but just in case you haven't, here's a
> quote from one of Jürgen's emails to this list (
> //www.freelists.org/archives/python/01-2004/msg00054.html ) :
> "Front fairing is not the best idea on center-steered bikes, because
> when turning you have to move the whole weight of the fairing. Tail
> fairing will be a good idea especially if you can integrate the seat
> with it. I want to realize it, when I build my Carbon Python this
> summer."
>
> Michael
> ============================================================
>
> This is the Python Mailinglist at freelists.org
>
> Listmaster: Juergen Mages jmages@xxxxxx
>
> ============================================================
>
============================================================
This is the Python Mailinglist at freelists.org
Listmaster: Juergen Mages jmages@xxxxxx
============================================================
Other related posts:
