Neat tilting delta Python trike

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Hi all

Another take on a tilting delta trike this time a Python.

N55 space frame inspired

Now I am not keen on the ' bolt together ' aspect of this trike , however there are some great ideas to be seen including including a Duschar joint from a Flevo style bike.



regards Paul

p.s looks like DannyC's next project me thinks........
 
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I have tried emaling him to see which rubber he used in the joint , what the rear track is and what changed he would make to the position of the joint.

regards Paul
 
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The grade and amount would be usefull to know. It will be an interesting ride with two points of articulation, one controlled by hands and one by feet / hips. My initial thought is that this system is less plagued by compromise than many others and also relatively simple.
 
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I think my misgivings [ to much time to ponder this ] are that my Python experience is based on the handle bars being on the moving part of the Python so I am used to using them for steadying the steering and gaining the last few degrees of turn at low speeds.
I have tried in the past to ride it hands free and have done so for a few miles however eventually I do chicken out and take control again from my legs.
What I could do is make a mounting under the front of the seat on the non steering part of the Python transfer the bar ends with controls on to it and try riding it like that before I committed to a copy in steel ?

Historically most Python 2 wheeler's and most Flevo bikes have the controls on the non steering part of the machine.

There are some Flevo bike/trike plans available for perusal here Flevo bike/trike plans some what over complicated compared to a Python with many mysterious parts !

regards Paul
 
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With it tilting you wouldn't need to shove at the bars to get that last bit of steering out of it. The lean will naturally increase the turning ability, requiring much less input than a non tilter. This may be a good design to employ a steering damper on. Whilst a damper is usually a means of disguising an issue, here it will allow the feet only to steer whilst the hands tilt and will dampen (sic) the tendency for the front to wag which will be a bigger issue on a tilter as any steering input due to pedalling whilst tilted will be magnified so a damper will probably be quite useful. With your bars being on the steering part your arms are probably doing some damping now.

One design change you could consider is to have the bars on the steering part but make them pivot so with the use of cables you could adjust tilt like the Mosquito does. Unlike the vertical Mosquito bars you'd need the bars fairly horizontal (they can be tilted to suit for the actual grip part) so turning force can be separated from leaning force. Turning force would be as you'd expect on the bars and leaning force by raising one bar and lowering the other, pulling on a cable against the resistance of the rubber. More complex but not overly so and would probably be ok damperless as your hands are on the steering part.
 
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I can see how NOT having steering input from bars on the front triangle would be very "unnerving". As an amateur Python-Pilot I find that they are essential to my peace of mind. :)
But gentle pressure on the fixed-bars and leaning is what makes it tilt so I guess it is a must. Unless you can get the elastomer rating right for it to tilt just on leaning without tugging on bars?
It would not surprise me if you could get a decent balance of both functions (Steering & Lean-control) from a front triangle mounted set of bars and just leaning. It would be a body-learning behavioural thing I would think.
Bars on the front clearly won't let you tug-it into a lean because you are tugging on the bit that is meant to lean and not the (rear-frame) horizontal reference part. Interesting.
 
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I am also kot a fan of such way of making the frame. He needed to put something in the tubes where the bolds are.

I was looking ad the mosquito. That one balances automatically. Only as you go slow, it is harder to steer. That is why I was thinking to combine it with the phyton front. You make the rear construction vertical, what makes that tilting doesn't make you steer. Steering and tilting is diconnected, just like by other phyton with tilting that way.
 
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First one with a working Python-flevo-trike wins!! :p
 
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This is interesting a real life example and an attempt to minimise some of it's downsides ?

Flevo trike Eric Wannee


Variation number 6: Improved tilt mechanism on trike rear section.
The standard trike rear section contains a ball joint that has a dual function. It is therefore called the duschar ( DU bbel SCHAR kidney) principle. It pivots vertically to allow for suspension, and in addition it can tilt about the longitudinal axis to allow the bike to tilt relative to the rear section.
This tilting has a few big advantages:
  • If you drive around a corner at a reasonable pace, you can lean into the corner to avoid flying out of the corner;
  • If you drive diagonally down a sidewalk you will not be thrown from left to right;
  • A bump under one rear wheel is only half passed on to the rider, because the height difference is compensated by the other wheel.
But there are a few comments to make with this tilting system:
The rear part (the luggage compartment) does not tilt, and it is not sprung either. That means:
  • That the rear wheels have to handle a heavy side load in the bends;
  • The luggage in the bin is rattling (be careful if you are transporting 500 eggs!);
  • In a bend, the box does not tilt, so that - especially when there is heavy luggage - it tends to tip over towards the outside of the bend.
This last point gave me an ugly crash once: I drove with a bale of 50 kilos of wheat into a right turn. The centrifugal effect made the luggage want to go to the left. But my own weight also pushed the box to the left via the tilting hinge.
These forces combined at the time were great enough to topple the bin, causing me to take an involuntary air trip.
This got me thinking. How can you prevent this?

  • Of course you could widen the box considerably. But I just wanted a narrow box to be able to easily drive between posts, to cycle side by side, etc.
  • The bucket's center of gravity could be lowered. I have now done this because the rod has disappeared from the box, so that large heavy loads can be lowered.
  • The point of application of the tilting mechanism had to be lowered.
The lowering of the point of application of the tilt mechanism, I did by dismantling the dual action of the duschar system.
The detail image on the right shows how. The spring part now works in the same way as with the bike ; the tilting mechanism is a lot lower (approx. 17 cm above the ground) and is made with the same type of axle as the one used for steering.





The left picture is the system of the standard Flevo-trike. The tipping point (blue dot) is quite high.
The lowered tipping point is used on the right picture.
The trick here is that with the same tilt in the corner, the resulting force due to the weight of the rider (blue arrow) ends up much more in the middle between the two rear wheels (distance 'B' is much greater than 'A' .). Ideally, the pivot point should be on the ground: The blue arrow will then always be exactly in the middle between the two rear wheels. (This is the situation that occurs with the bike ! You wouldn't be able to feel while riding whether you are riding a bike or a trike.)

Dropping the axle would also lower the pivot ?

I read somewhere the Flevo trikes have a rear track between 15" and 28" with 24" being quite common [ can't find the reference again DOH ]

Paul
 
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I would mount the piviot below the axle. It is also makes that it is easier to balance.

It depends on what you want yo take with you, but I would prefer to have a rack, tilting with the trike.
You can mount the rack higher without a negative effect. As you choose for that, then I would also go for an other tilting system.
Other option is, to place it as low as possible and put some camber on the rear wheels. Togheter with the low piviot, this will help to keep the trike stable in the corners.
 
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I would mount the piviot below the axle. It is also makes that it is easier to balance.
Can't see why that should be ?


It depends on what you want yo take with you, but I would prefer to have a rack, tilting with the trike.
If the wheels stay upright then the rack needs to , otherwise you loose most of the luggage space

You can mount the rack higher without a negative effect. As you choose for that, then I would also go for an other tilting system.
No that is why he moved the pivot to get the CofG lower see below

[/QUOTE]Other option is, to place it as low as possible and put some camber on the rear wheels. Togheter with the low piviot, this will help to keep the trike stable in the corners.


Yes to as low as possible
No to camber on the wheels

In the left hand picture point A is where the weight is applied when cornering at that angle , if the forces were to push A further outwards till it was outside the rear wheel the trike would tip over.
Oddly it would be leaning to the left but tip to the right , sort of counter intuitive.
So no amount of camber will stop that as tip over purely depends on A in relation to the tyre contact patch which DOES not alter with wheel camber.

Paul
 
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The lower you place the pivot the more your body is moved side to side and the wider the trike becomes in a turn. This means that bars on the fixed part need to be wider still to allow for such a swing. In example A above you'd just about get away with bars the width of the rear track. In B the bars would be outside the rear track. The outside bar will be getting hard to reach. The more the body moves the more effort it will be to move it. I'd place the seat low necessitating the rear wheels to be behind the seat and keep the pivot close to the seat. Keeping the pivot close means you need the seat low to avoid it tipping but it also means less body swing. Having less body swing means it's easier to rotate yourself. I'd place the bars on the tilting part (not the fixed part or front triangle) and would control tilt by cables like the Mosquito and utilise a damper on the front wheel to minimise pedal steer. Pedal steer will be a bigger issue on this than a non-tilter.

One other possibility is one bar on the tilting part pushing / pulling on two cables for tilt and one on the front for steering. Keeping the bars off the fixed part keeps them much nearer the body.
 
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I will try to explain. My English isn't that good, so that is why it is hard for me to explain why s longer distance is easier to balance.
As you have a long stick and a small stick and you try to balance them on your vinger, you notice that the long stick is easier to balance.
The distance makes that before you reach a surten angle, will take more time to reach. That gives you more time to respond.
There are other things but it is for me hard to explain. Like why it moves slower and that stuff.

That is what I say. It depends on what you take with you. As you let it tilt with you, the luggage space will be limited. Not completely true, because you can make your luggage box more vertical. You only need to make sure that the luggage is fixed good and doesn't move. Else you notice that and that isn't always great to keep balance.

The place of the piviot makes that the point of gravity moves to the middle as you lower it. The amount of weight that is on the seat, doesn't mater. On an upright bike, the rack is above the wheels. You can do exactly the same with this, only you need to make sure that it is high enough so it doesn't touch the wheels when they touch.

With camber you make the trike wider as the mounting points are on the same spot. The contact patches are further to the outside, what makes that the A would be bigger then in the image on the left and the same with the image on the right with the B.
It is where the contact is with the ground. Camber (negative camber) will make it wider or you need to move the mounting points of the wheels further apart from each other to reach the same effect. The wheels have often some space left neer the luggage box/rack, so putting a bit of camber will not influence that. You make the track of the trike a bit wider and it will make that it doesn't tilt as fast, what gives you higher cornering speed.
 
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Sorry Emiel, it probably does. I tried the image insertion option, but it didn't work, so the link was listed, instead. I will work on it!
 
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I will try to explain. My English isn't that good, so that is why it is hard for me to explain why s longer distance is easier to balance.
As you have a long stick and a small stick and you try to balance them on your vinger, you notice that the long stick is easier to balance.
In that example you are correct but that example balances from the bottom which is a different issue. A better analogy would be is it easier to balance on short or long stilts? Either way it only applies if you are actually balancing. Here the tilt is controlled by levers not by balancing, though an element of balancing may be in effect too. The further from the pivot the rider is the more the rider moves. This movement has a vertical component so that means further to lift the rider back to center.
 
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