[python] Re: python Digest V11 #55
- From: Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx>
- To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
- Date: Wed, 18 Sep 2013 16:50:34 +0200
Hi Howard,
I have just done some measuring on my trike (for a pic see:
http://cycle.free-creativity.com although nowadays I use ropes and no second
steering handle), but I am not sure how useful it will be for you since I have
a tilting trike. At the moment the angle is 67 degrees. It has been lower in
the beginning I think, when I didn't use ropes and had the rod ends at neutral.
The reason I adjusted the rod ends for a bigger angle wasn't because for
steering issues but to get more clearance between the mudguard and my seat.
Didn't notice much difference for the steering after that adjustment.
Stability has always been great (except when slipping the front wheel). As a
matter of fact, using the Jetrike tilting system was a bit too stable for my
taste: at higher speeds it was hard to corner (lean enough). So I adjusted some
arm lengths to lessen the seat rize effect for better high speed cornering.
It's still not 100% the way I would like it, but the trike does it's job and is
now more than 2 years old with many miles on it. I use it as a SUV (or should
we call it SUC: Sports Utility Cycle?) for pulling a big trailer (part of my
job as a garderner) and sometimes for speed (together with a friend's Strada).
Not sure what you exactely mean by : "I have found it necessary to reduce the
angle to the low 50's I have
tried 51 - 52 degrees and found the stability wonderful but the wheel
flop prevents sharp turning."
Can you describe 'stability' a bit more? What went wrong/undesirable while
cycling? At low speed/high speed?
What I suspect is that the CoG has a lot to do with it. As with the Python:
when you steer to the left, the CoG will move to the right. With a Python you
can adjust this by leaning to the left, but your trike can't. I think what
happens is that when you steer your tike to the left the CoG will move to the
right and generates a force for more steering input. (not really sure but just
a theory). Think about it: you want to move to the left, but your CoG goes to
the right. That is counterintuitive in my eyes.
My question: does the trike have a tendency to flip when cornering at speed?
Lowering the pivot angle might help since your legs (and therefore the CoG)
leans more into the corner, but as you say you run into other problems like
wheel flop.
"I agree that the PSI is more of a problem with the trikes and so a reduced
pivot angle seems necessary.
I don't agree. Why would it be more of a problem? Why reduce the pivot angle? I
think to keep PSI as low as possible you would better stick to the Python
theory: having the pivot line going through your hips. If you can't manage that
with an 60-65 degree angle then you should shift your pivot.
Kind greetings,
Patrick
Date: Wed, 18 Sep 2013 20:23:09 +1000
Subject: [python] Re: python Digest V11 #55
From: hstevens94@xxxxxxxxx
To: python@xxxxxxxxxxxxx
Hullo Vi .......and congratulations on the number of models and experiments you
carry out!! My next trike will not have a roof but the suggestion is a good
one.I agree that the PSI is more of a problem with the trikes and so a reduced
pivot angle seems necessary. This time I am fitting a damper a la Hipparon
which may help and avoids the unsightly wheel flop when at rest. My building
efforts seem to be rather slow this time, but I should be finished in the next
month. CHanging the pivot angle after construction affects the whole geometry
so that the mid section is either too high or too low, so I am hoping that 55
degrees will be just right!! Thanks for your comments.
Thanks also Gerald for your comments on pivot angle. Anyone else?? Regards
from "Down under"....... Howard
On Tue, Sep 17, 2013 at 3:07 PM, FreeLists Mailing List Manager
<ecartis@xxxxxxxxxxxxx> wrote:
python Digest Mon, 16 Sep 2013 Volume: 11 Issue: 055
In This Issue:
[python] Re: python Digest V11 #53
----------------------------------------------------------------------
Date: Sun, 15 Sep 2013 23:11:12 -0700 (PDT)
From: Vi Vuong <vi_vuong@xxxxxxxxx>
Subject: [python] Re: python Digest V11 #53
I have tried as low as 45 deg on both trike and bike, near zero trail? I guess
trike needs less self-centering from seat rise effect to control.
Gerald, I notice more PSI on trike with same pivot angle. Do you? Maybe I am
expecting more from a trike...
Wheel flop is also unpleasant when walking bikes. For trike I tend to pull
from the front, but somehow a python does not look well when it "flops"
standing still, not to mention damaging chain ring. I have increased low pivot
angle to ~60 understanding trade off.
Howard, if your MK3 will have a roof also, I suggest attaching a bungee cord to
the BB to keep both in place, see http://youtu.be/sB1V7Wb5HfQ. How about using
rod-end pivot for angle adjustment?
Vi
>________________________________
> From: bepb <bepb@xxxxxx>
>To: python@xxxxxxxxxxxxx
>Sent: Sunday, September 15, 2013 10:34 AM
>Subject: [python] Re: python Digest V11 #53
>
>
>
>Hi,
>my python trike too, has a pivot angle around 50 or 52 degree,
while the bike has 63. Maybe it makes sense because on the bike
there is some influence from the tilting.
>Load of 20-30kg is no problem if the slope is not to steep and the
road has grip. If not, I have problems with the front wheel
slipping.
>Obviously, sitting more upright or leaning forward helps but is
very uncomfortable. Part of the problem is that my trike has a
very short wheelbase and part of the luggage rack is behind the
rear axle.
>
>Looking forward to see more pictures, both of your MK3 and Pauls
trike!
>
>Cheers
>Gerald
>
>Am 15.09.2013 10:03, schrieb Howard Stevens:
>
>Hi all,
>>I am interested in all the python trike chat at present. I use an Avid B7
>>disc brake on the front wheel and agree that the braking from the front
>>brake is so powerful that I see no need for another unless it is as a backup
>>brake in case of failure. I have not experienced any tendency to jack-knife
>>or lift the rear section. I am interested in what people have experienced
>>with loading their trikes and the stability of the pivot joint in the
>>recommended low 60's . I have found it necessary to reduce the angle to the
>>low 50's I have tried 51 - 52 degrees and found the stability wonderful but
>>the wheel flop prevents sharp turning. This time I will try 55 degrees. As
>>I am building in f/g and carbon fibre it is not easy to make the angle
>>adjustable and so I would really be interested in the experiences of others.
>>Cheers Howard Stevens
>>
>>
>>
>>On Sun, Sep 15, 2013 at 3:08 PM, FreeLists Mailing List Manager
>><ecartis@xxxxxxxxxxxxx> wrote:
>>
>>python Digest Sat, 14 Sep 2013 Volume: 11 Issue: 053
>>>
>>>In This Issue:
>>> [python] Re: Building a cargo style trike
>>>
>>>----------------------------------------------------------------------
>>>
>>>Date: Sat, 14 Sep 2013 07:47:29 +0100
>>>From: Paul Needham <paul.2.needham@xxxxxxxxx>
>>>Subject: [python] Re: Building a cargo style trike
>>>
>>>Hi all
>>>
>>>Sorry but I am new to this mailing list format and don't
seem to know
>>>how to add to my own post when I get the mail in digest
format [ need to
>>>look that up ].
>>>
>>>Thanks for all your replies , I think initially this will be
a 2 x front
>>>brake trike and have a shortish wheel base of 36"
>>>
>>>If there is insufficient cargo space I will look at making a
different
>>>rear end.
>>>
>>>The sliding idea did not work as I cannot find any tubing
with a loose
>>>enough fit to slide inside another piece far enough to make
it work.
>>>
>>>I had another idea of a 3 bolt extending rear end , a bit
more work but
>>>better I though , however that won't work properly as I
realised the
>>>rear boom out to the axle slopes down to the pivot.
>>>
>>>This means any change in wheel base by moving the axle will
cause the
>>>pivot angle to change DOH !
>>>
>>>Progress can be followed here :-
>>>
>>>http://forum.atomiczombie.com/showthread.php/8210-Building-a-python-trike
>>>
>>>regards Paul
>>>
>>>------------------------------
>>>
>>>End of python Digest V11 #53
>>>****************************
>>>
>>>
>>
>
>
>
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End of python Digest V11 #55
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