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 <mailto: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 <mailto: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 <mailto:bepb@xxxxxx>>
>To: python@xxxxxxxxxxxxx <mailto: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 <mailto: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
<mailto: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
>>>****************************
>>>
>>>
>>
>
>
>
------------------------------
End of python Digest V11 #55
****************************
