[python] Re: Some Python - Data / Pictures
- From: Vi Vuong <vi_vuong@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Thu, 24 Mar 2011 17:59:59 -0700 (PDT)
Hi Gerald,
I got much better fit and grip with seat pad made from 3 square synthetic grass
mats. Ventilation is decent in cool weather. Will report back when it gets
warmer. http://en.openbike.org/wiki/File:GuineaPigSeatPad.png
Vi
________________________________
From: Gerald Kuettner <bepb@xxxxxx>
To: python@xxxxxxxxxxxxx
Sent: Thu, March 24, 2011 7:29:39 AM
Subject: [python] Re: Some Python - Data / Pictures
Hello Jürgen,
thanks for the compliment, but actually the 28" python was my first serious
alloy welding project and I am still a novice welder. At a closer it shows some
welding and design blotches. On the 20" Python they just may not have had the
time to show.
You are right, the two seat are complete different.
The seat off die 28" is a mesh over a welded tube construction. It realy just
bolted on top of the middle frame. Additional bracing supports the seat on four
places. Especialy the bracings required frequent repairs in the past.
To some extend this is due to falls during my efforts to master the bike, but
it
also bends if I put to much power into my pedaling.
The seat of the 20" python is just a sheet off 2mm alloy bend and supported
with
two bracings also cut from 2mm sheet alloy. The back is riveted directly to
the
frame.
Up to now it performs a lot better than the mesh seat.
I original planed to affix some kind of close cell foam mat on top. But I have
done some 300 km on the bike and for the moment I am comfortable as it is.
I fear that the isolation off the mat will make it uncomfortabe hot on the
back.
Maybe puting some holes in the seat and mat? Any expiriences?
Gerald
-----Ursprüngliche Nachricht-----
Von: "Jürgen Mages" <jmages@xxxxxx>
>An: python@xxxxxxxxxxxxx
>Gesendet: Mi., 23. Mär 2011, 08:20:07 GMT+00:00
>Betreff: [python] Re: Some Python - Data / Pictures
>
>Thanks very much Gerald,
>
>they both look great - you seem to be an expert in alloy welding. I will
>include
>at least the 20" one in my survey. We also should set up a wiki page for
>these,
>so that you can update the info on your own.
>
>I am wondering how the seats are performing, because they both look quite
>unusual?
>
>Cheers,
>Jürgen.
>
>
>On 21.03.2011 23:33, Gerald wrote:
>> Hi Jürgen, Dear All,
>> yes, of cause there are pictures - I just hope they will make it through >
>> the
>>volume limit.
>> I also added the measurements generally taken for the Project survey. I >
>> would
>>be nice if you would include them.
>> > 28" Python -current- 20"_Python
>> Roll-out 4/2010 2/2011
>> Pivot-Angle 62,5 62
>> Trail 33 22
>> Seat-Height 25 27
>> BB-Seat 30 31
>> Ground-Clearance 11 14
>> Wheelbase 137 90
>> kg 16,9 13,9
>> BB-FWA 40 53
>> Turning-Circle >6m 1,5
>> Front Tubing 50x20 50x20
>> Wheelsize 28 (622) 20 (406)
>> CG (%) 54 46
>> > > Generally the two pythons ride quite different.
>> The old 28" version is hard to ride if tight corners need to be > mastered.
>> But
>>on reasonable strait lanes, it runs just great and really > fast.
>> The reason for of the huge turning circle is that the front mudgard >
>> touches
>>the Seat very early.
>> This bike sports a rear suspension, but it is a bit different from > Jürgens
>>construction.
>> > The 20" version is quite different, as is to expect. The short wheelbase >
>>and the fact that the front part goes under the seat while cornering, > the
>>front part can bend 90*. In practice, doing some continuous circles > of
>>about
>>2,5m diameter at a rather unreasonable speed - if you don't get > thick.
>> Top Speed is 44km/h yesterday, 8th and highest gear and most probable as >
>> fast
>>as it can go.
>> The bike does not have a suspension, but rather thick tires (20" x 1,9).
>> > The measured speeds are, obviously, only short term sprints, not even 200m.
>> > The pivots of the two bikes are quite different. The 28" Python uses >
>>industry standard ball bearings. They worked great, had no play - but > there
>>problem is rust. After this winter, they are nearly finished.
>> > The 20" Python use standard 1 1/4 head tube bearings.
>> > The front part of the 20" Python actually comes from the sailing python >
>>trike I started last autumn.
>> I had postponed the project though the winter but still have the two > trike
>>rear parts - one 130cm wide the other 85cm. Maybe it is some kind > of python
>>option system bike :-). The two trikes and the bike share the > front part as
>>well as the rear wheels. Even for the bike. If you take a > close look at the
>>rear wheel, you see the single sided attachment.
>> > The front tubing of 50x20 might sound over sized, but since the material >
>> > is
>>only standard grade construction Aluminum Alloy (AlMgSi0.5 or > something)
>>this
>>is required.
>> > Gerald
>> > > > > On 18.3.11 22:33 , Jürgen Mages wrote:
>>> Thanks Gerald,
>>>
>>> while pushing my P3, e.g. through a pedestrian zone, I rarely apply >>
>>>downwards pressure to the back of the seat (which is my handle). It is >>
>>>more
>>>like a smooth sidewards shifting to keep the bike on its track.
>>>
>>> However, of course, this pushable/rideable rule is just a rule of >> thumb
>...
>>>
>>> Cheers,
>>> Jürgen.
>>>
>>> PS: Any pictures of your specimens available?
>>>
>>>
>>>> Hi Vi, Hi Jürgen, I am not sure about the pushable requirement. Maybe
>>>> a python beeing pushable is an indication that the pivot angle is
>>>> right, but it seems, just that a python is rideable does not
>>>> ensure it is also pushable. I do own two such specimens. Both of
>>>> them ride quite nice and I do so in public traffic.
>>>>
>>>> For a python to be pushable, I think, beside having the pivot angle
>>>> right you need to be able to put sufficient weight on the pivot
>>>> while pushing. If the back of the seat is to far back, you may not
>>>> be able to.
>>>>
>>>>
>>>> Gerald
>
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