My life with Python trikes Mk1 , Mk1.5 , Mk2 ?

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If I asked you what causes a 2 wheeler you are ridding to get vertical after it has tilted to go around a corner could you answer ?
Yes.
Essentially the bulk of the force is due to the rider shifting their weight above the line required to maintain the turn, in effect unbalancing the forces in favour of moving one way. To a much smaller extent you can also slightly oversteer which will have the same effect. You can demonstrate this by riding the two wheeler hands free. It's quite simple to turn and unturn without steering input.
Using steering as the main force to lean is normally reserved for motorcycle racers who need very rapid movement.

Your hands are there primarily to damp the bars and provide part of the means to move your weight
 
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Not wishing to hijack Paul's thread at all, but he did mention we were looking to see if there was a relatively simple way of making a Tilt-O-Meter.

I make one with data written to an SD card and with a real-time clock timestamp so the data could be read by Excel and processed.
Then I thought about making one that just ran and displayed the max & Average tilts on a real-time display.
Here's what I came up with in its breadboard clothes. Seems to work just fine.
Can be made to run on any of the Arduino boards I would imagine. Requires only the MPU6050 Gyroscope board and a 16Char x 2 line display.

Cheers!

 
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Maybe no one makes a Python due to control issues near the edges of the envelope ?

However they do make these :-



Now if this had pedals at the front of the wheel for legs :-

a) is it then a Python
b) would it handle better than my Python ?
c) if the drawing is accurate it has 0' trail

Hmm....

Paul
 
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Dan

Excellent work , you could ditch the ' - ' signs and get more display space ?

:whistle:if I tilt left or right it has always seemed positive to me ;)

Paul

ps displays turned up today , much bigger than I expected
 
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A - no I don't believe it is. It looks more like a std Pashley type trike with a high rake on the steering.
B - I'd expect stability but very slow turning, also the only thing that moves is the front wheel. None of it tilts. Just the front wheel looks like it tilts but it doesn't. It turns and the enormous rake makes it appear to tilt. It's essentially a chopper trike.
C - I'd expect regular bike trail figures to work best for it.
 
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A - no I don't believe it is. It looks more like a std Pashley type trike with a high rake on the steering.
B - I'd expect stability but very slow turning, also the only thing that moves is the front wheel. None of it tilts. Just the front wheel looks like it tilts but it doesn't. It turns and the enormous rake makes it appear to tilt. It's essentially a chopper trike.
C - I'd expect regular bike trail figures to work best for it.
I am looking for a solution to my trikes speed instability when only steering with legs , it may be connected to the steering angle and/or trail ?

Paul
 
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Ok so I have ridden it , briefly.

First off I ONLY used the bars on the steering part , although the other bars were fastened and available.

Taking advice form the Finns I tried to treat it like a 2 wheeler ? so right foot on pedal [ no clips ] and a good push to get going and lift left leg [ hopefully ] before it is it's turn for a strong push and it worked.
Slight left turn and rode the gutter out of my cul-de-sac made the right 90' turn and headed off down towards the challenging 90' followed by a 360' , never got there !
Realised there is a small green on my right big enough to try riding around on [ DannyC's suggestion ] so up the down ramp and onto the green.

Turned to sharply and thought it was going to dump me , I felt there was to much lean for situation and I was not quick enought to try and correct it.
So foot down and spirited restart when it was straightened worked and we were off again.
Spent maybe 5 minutes just doing lazy circles trying to reach a flower or lamppost turning and trying again.
Decided I wanted to try altering the handle bars so called it a day and set off for the down ramp , over cooked it again on the tarmac with a 100' left hander and had to stop however the restart was easy and we got home , even did a little zoom turn onto the drive missed both cars by a hairs whisker and ended up stopped on the front path.
Not elated but happier some progress has been made.

The above was not intended to be today's post ! this was :-
Yesterday DannyC and I had a drains up as to what has happened so far and what are possible ways forward , well mainly DannyC [ bless his cotton socks ] has listened whilst I pontificated on my current situation.

I have not reached a T junction nor a cross roads but a multi exit island [ see below ]

Going back to the beginning what was the reason for tilting ?
We both want a narrow rear end due to obstructions encountered in the real world.
We both want a higher seat to get out of the dirt and for comfort etc.

Exit 1 )
So I realised that neither of us had actually tested how narrow a Python rear axle can go and still be safe ? [ we figure on 24" [ 61cm ] between tyre centres ]
I also realised that neither of us had actually tested how high can the seat be with the narrower rear and still be safe ? [ hoping for 16" - 18" [ 40cm - 45cm ]
maybe tilting is not needed at all ?

Exit 2 )
With the bars on the non-tilting part it rides fine and tilt feels controllable [ although not yet with a narrow rear end or high seat ] however there is unnerving steering instability not controlled by the feet .
can the steering instability be fixed ? zero trail or positive trail or change of pivot angle ?

Exit 3 )
With current trike and bars on the steering part I have great difficulty riding it ? is it just a learning thing - can I learn quickly ?

Exit 4 )
could both the above be fixed with dual controls on the fixed part doing both tilt control and steering control using control rods ?

Exit 5 )
What about a non-Python front end and tilting ? if so which one ?

Exit 6 )
What would happen if only the seat tilted , so the whole weight of the front end was not adding to the tilting weight/inertia ?

Exit 7 )
Would it be more stable when riding with the bars on steering part with more tilt damping ?

puzzled Paul
 
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  1. Depends on the tilting mechanism as much as anything. Some mechanisms will do better at keeping the centre of gravity within the track than others. Narrow can be done with the right mechanism and your current mechanism looks like it would tolerate narrow.
  2. I'd suspect controlled rather than fixed may be more achievable. See no. 4.
  3. Unknown, but the whole python / flevo thing seems like you are starting from a design of known dificulty to me.
  4. You know my position on dual function bars. Pull up and push down to tilt. Fore and aft to steer and can be held upright when stopped. It looks like both the simplest and best solution to me.
  5. Danny's design is the obvious. It's a sound principle and been built many times. Ask yourself why you want three wheels though. Would two do a better job? You could easily get off the floor and tilt perfectly on a two wheeler.
  6. How would you pedal or steer a non tilted wheel from a tilted rider position.
  7. I suspect tilt damping is primarily there to mask instability. I see only two ways to have stable tilting. One is by balancing as you would a two wheeler. Certain mechanisms lend themselves better than others to this and the other is by some control mechanism. That control mechanism can be as precisely controlled as a Mosquito with it's cable controlled tilt or as simple as bars you can leverage against so long as that leverage does not get to the point of excessive effort.
 
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Thanks for you comprehensive answer , more questions are not necessary bad !

1 ) was actually with no tilting ? we just assumed we needed tilting to achieve those figures without actually trying
  1. if it wasn't for the steering instability i would not be at this round about , all was peaches and cream ...
  2. only when I make them ;) I am to old and slow to learn to ride either a Python or Flevo 2 wheeler [ better things to do with my time ] hence the trike , my previous Python has performed faultlessly for k of Km
  3. we may yet head there , looking for a compact light way of implementing them.
  4. Danny's design is not stable or self standing or suitable for luggage it is only a 3 wheeled bike etc he wanted [ and I did with my iLean ] to abandon it before it was even tested. Most people with parallel tilters/iLean say when riding you think you are on a 2 wheeler , on mine you don't you feel as though you are on a trike that is some what supple [ unlike the rider ]
  5. You don't tilt far , in effect I have been doing that on my normal Python anyway as the front leans left and right when pedaling ?
  6. I think I am balancing as on a 2 wheeler ? if you consider the non-tilting part as an extension of the road surface then I am sat on the road on a pair of elastomer's mimicking tyres ?
Someone on the Python list has suggested the steering weave/instability could be due to poor set up of the rear wheels i.e toe in or out ?
Guilty as charged your honour , I made an appalling job of getting the wheel mounts square to each other , although it was never the intention of riddin this very far I seem to be :whistle:.

I do now have some 1m x M12 rod so ought to either attempt to straighten them or add new mounts.

paul

how can I get rid of this bl**dy list , every time I try to edit it out the thing comes back :mad:(n)
 
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Exit 5
A modification of this may suit...


Whereas that trike looks to be tilt steer with a fixed tilt to steer ratio you could try mounting the front wheel as per the red one in the video, ie free to steer, but instead of putting a set of handlebars in the head tube simply allow the steering to be free bar possibly a light duty damper between fork and frame. The steering would then act exactly as a two wheeler being ridden hands free but unlike a no hands two wheeler you'd have the stability of fine tilt control via bars on the fixed part. The steering should, in theory, always try to self upright the trike when in motion due to the trail just like a bike being sent down a hill without a rider will at least try to stay upright or as some motorcycles do when they've spat their rider off in a race and the motorbike carries on riderless for some time. You'd effectively be steering by tilting but the ratio wouldn't be fixed.

Whether that will work in reality remains to be proven. Unless of course it's already been tried.
 
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I'd expect that you'd need high tensile m12 rod. I would expect std stuff to bend.
Yes I expected it to bend , there are probably better ways ....
 
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So had some think/build time today . however as it's Sunday best keep the noise down I might get drowned out by the 4 neighbour's with handkerchief lawns and petrol mowers :mad:(n)



First up a wooden model of current tilter showing available space for moving bars only 45mm high and about 120mm long.
M12 bolt shows probably pivot point for a set of conventional handle bars.



Couple of possible pivots that will fit in the space either goose neck gripping those SA hub bearings or the trimmed down pivot from a shopping trolley.
My moneys on the shopping trolley :whistle:



Marked out new front end for surgery to tip the BB up to make the centre section horizontal and not slope down to the pivot.
Will need pivot cutting out at other end and repositioning ?
DannyC thinks I should leave it be , however if I am to have a taller seat I need a front end that has the pivot @ 10" high not the current 5".



Another possibility to finishing this to achieve a 10" pivot height , to be honest not much more work.
However if it is done craftily it can be made to take either a 20" or a 24" wheel , especially if the 2 braked wheels are on the back.

Choices choices choices ....

Paul
 
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Exit 5
A modification of this may suit...

Now you and Emeil have spent a year extolling the flaws of tilt steer , so I shall keep well away...
Also DannyC of this parish has a aversion to twisting chain so another black mark against it.
Impressive turning circle , although he is just sat on 2 elastomer's as I am ?

Had plans for this for a while 26 x 26 tilting delta always slightly tempted by it's simplicity ?



Good selection of pictures here :- Triflex


Even a video !

Perhaps tempt DannyC might work well with 24" wheels and SA brakes on the back ?

The main problem is the videos imply there are 6 versions ! so obviously ironing out some flaws me thinks !

Paul
 
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Now you and Emeil have spent a year extolling the flaws of tilt steer , so I shall keep well away...
How can you say that and then say you are slightly tempted by what is exactly that: a tilt-steer!:unsure:
My proposal takes a tilt-steer and breaks that fixed ratio that tilt steers have. It doesn't mean it would work but it's certainly no longer a tilt-steer. It steers by tilting as does my current tilting project but that does not make it a tilt-steer. The video and picture above are fixed tilt-steer machines. The ratio of tilt to steer is fixed and unalterable.

The Sirio does look like it rotates on elastomers which will provide some self righting. The bars are on the fixed part and the feet don't interfere with the steering. I have no idea how powering the front wheel would affect any ability to freely steer. I can't believe it would help but I don't know if it would hinder.

If that free steering idea isn't a goer then you could always copy the machine apart from putting handlebars in the head tube to provide regular steering or use USS on the tilting part. That would leave it requiring balancing as either way the bars would be on the tilting part and you'd be using the elastomers in twist as a stability and uprighting device. Either way though you'd do away with the python front which is, I believe, the single biggest issue causing you problems so far. Having a front end wagging about whilst upright is bad enough but the effect is multiplied when tilted. Get rid of the python pivot and your stability potential increases considerably.
 
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How can you say that and then say you are slightly tempted by what is exactly that: a tilt-steer!:unsure:
My proposal takes a tilt-steer and breaks that fixed ratio that tilt steers have. It doesn't mean it would work but it's certainly no longer a tilt-steer. It steers by tilting as does my current tilting project but that does not make it a tilt-steer. The video and picture above are fixed tilt-steer machines. The ratio of tilt to steer is fixed and unalterable.
I said I always liked it , however building it is another thing , however DannyC might be tempted ? I sold him a seagull I could see out my window once ?

device. Either way though you'd do away with the python front which is, I believe, the single biggest issue causing you problems so far. Having a front end wagging about whilst upright is bad enough but the effect is multiplied when tilted. Get rid of the python pivot and your stability potential increases considerably.
Go wash your mouth out ;)
Strangely the Python is most steady/stable when being pedaled up hill [ unusual for a recumbent ]

The Python mailing list has suggested the elastomer's may be causing the problem in conjunction with the rod end bearing ?

A Flevo trike usually has a rod end bearing and a single elastomer , I started by copying that.
I initially had great problems when trying to ride it with considerable steering input causing it to dig in on tight corners.
I though it was caused by the rod end allowing 3 degrees of movement [ as aircraft pitch , yaw and roll ], and there being no control over the yaw component .
As a quick fix I added a second elastomer and though I had it under control , maybe the tail is wagging and is still influencing the steering ?
It is my intention to build another trike where the pitch and roll are separated with single axis pivots , as 2 elastomer's cause a great loss of pitch [ suspension ] and that would be nice.

Even with 2 hard elastomer's the ride is much superior to my rigid Python trike.

Paul
 
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I admire the determination to stick with it though I don't understand why. It's easy for determination to become stubbornness though.

If you want to control the tilt more then two rod ends would create a fixed tilt axis instead of the wandering one at present. The elastomers will then only comply in the direction the rod ends allow. That would remove all elastomer suspension though.

That seagull was actually a parrot and it was already dead. Cue "The Liberty Bell".
 
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