Tilt Steer Delta

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I've been thinking along these lines lately:-
Take a 20" wheeled donor with rear suspension like this one: where the rear top stays are pivoted at the wheel end and the suspension linkage passes around the seat post rather than being attached to it.



Then build this:-




3x20" wheels. The rear triangle has a head tube at the top so the tube passing through it is free to rotate. The steering is by brake cable (2 each side for safety) with USS pulling on one side or the other of the cable to pull on one side or the other of an actuator bar welded to the main tube. The rear suspension of the donor is used at the front hence the desire for that particular type of suspension arrangement.

As with any tilt steer system it's a compromise and will usually be a bit too much or little lean for any given corner but rarely worse in that respect than having no tilt. It needs to be wide as the pilot is not ideally placed between the rear wheels but needs to be forward from the ideal. At rest when parked it'll probably flop as there's more weight above the axis of rotation than below but with the lard onboard the pilots weight should act below the pivot axis to bring it to rest in the straight-ahead position as a Python does.
If excessive swing is used it's going to tip with the forces being outside of the rear wheels let alone outside the three contact points area. At slow speeds this will not tip as the centrifugal force will not be sufficient to pull it over. However at faster speeds it becomes more of an issue as with any delta.



Helping in this respect is the front wheel contact point moves outwards as you turn due to the head tube angle being ahead of the front wheel though it's only a little help and the wide rear track of 37". The only way to make matters better is to widen it more or lower the head tube. The latter is not desirable because of extra wheel flop. The general idea has been blatantly ripped off from here and the stability was questioned, measured and deemed acceptable by the builder/user.

The rear suspension on the front could also be of interest to Pythoneers as it's perfectly adaptable to such a design and the main tube over the front also acts as a crud catcher / gonad saver.
 
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Hi there

It came from here :- Adventures of Greg ultimately the handling was considered dangerous [ IIRC ] and was abandoned.

The lean steer I tried highlighted a few of the problems that would make it hard for me to use one on my usual journeys ?

a) Very poor turning circle
b) unable to initiate a turn when stationary
c) unable to turn tightly at low speed as the tilt needed dumps you on the floor !

Still that's just me YMMV :whistle:
 
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One alternative to consider is moving the rider to a more between the paired wheels position for more stability. I'm not the biggest fan of this idea, hence why I didn't start from this position, as it puts a lot of extra stress on the head tube welds and the head tube itself because gravity, centrifugal forces and any bumps are transmitted less through the tubes and more through the welds. It does though place the rider in an inherently more stable position.

 
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I can't see anything like that on that link Paul!?
Purely because of the way the frames are nested on the site ?

Down the left hand site are links to blog pages , this is the link for Sept 02 2004 as you can see exactly what you found in condensed form ?

This is where tipping tests are carried out Nov 5 2004

Feb 22 2005 he starts on his 2 wheeler.

This is probably the safest tilt steer delta trike :-

Mosquito velomobile



Four bar linkage at the back , probably the one I would copy if I wanted something the same ?






Try here for build of trike basic's Delta Mosquito style bit OTT for us Zombie types ?

A quick all steel prototype ? [ well some wood ! ]


No sign of a welder !


Part 2 more wood and bolts !

Paul
 
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Thanks for that Paul.
I suspect that there's a mistake in the assumptions in that November link. I believe they have the estimated C of G a fair way out. They have it way too high IMO throwing everything said about it into question. To my eyes the C of G is a lot lower meaning it's more stable than said at rest but then gets worse as it leans. They say exactly the opposite because of their estimate of the C og G. There doesn't appear to be any conclusion as to it's safety or lack of and given my own doubts I think I'll abandon this design without setting welder to steel.
I do agree with them though that in such a design a failure to get the rider between the rear wheels is to design in a higher potential for an accident.
I also think you're correct in that the 4 bar linkage is a better idea than the head tube pivot primarily as it pivots the rider rather than swings them and I'll have a ponder on such a system. The Mosquito however is exceptionally wide perhaps because it doesn't get the rider twix the rear wheels either.
 
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I also think you're correct in that the 4 bar linkage is a better idea than the head tube pivot primarily as it pivots the rider rather than swings them and I'll have a ponder on such a system. The Mosquito however is exceptionally wide perhaps because it doesn't get the rider twix the rear wheels either.
I think your title is misleading ?

Now in the recumbent world tilting just describes a trike that all ' tilts ' when cornering , however the trike also has a completely independent [ of the tilt ] steering mechanism and there is no way of initiating tilt except weight shift.

The word leaning is almost always associated with steering and usually only the part of the trike with the wheel used for steering leans ?

Result then if I saved the welder being deployed building a iffy design (y)

Lean steer I am unsure why they feel the need to have handlebars connected to the rear bars to initiate a turn ?

Surely just the act of leaning will initiate a turn ? and the bars could just be fixed to a non moving portion of the frame to give more leverage ?

Paul
 
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???😕

The title of the thread is "tilt steer delta". The trike is a delta and it steers SOLELY by leaning/tilting, therefore it is a "tilt steer delta". The phrase "tilt steer" describes any vehicle that can steer ONLY as it tilts - it can not steer without tilting. Technically it steers by the rear wheels, as all "tilt steer" deltas do, as when a turn is initiated the front does not in fact go off line but the rear tillers ever so slightly. There is no steering independent of the tilt. I do not see where you think that independent steering function is? The bars are NOT connected to the front wheel. The tilt is initiated NOT by weight shift (weight actually rises on this design as it turns so no amount of weight shift will do that) but by pulling and pushing the normal USS bars which pull on cables that pull on an arm welded to the main tube at the rear just forward of the head tube pivot. The main tube then rotates clockwise or anti-clockwise as a result and the front wheel being directly mounted to this main tube has to rotate with it. ie steering is a function of leaning and ONLY a function of leaning.

I associate lean with leaning and steer with steering. They are two separate functions though can be tied together as per point 2 below.

There are essentially two types of leaning trikes and this applies to both delta and tadpole:-
  1. There are those that can lean and also have a separate steering function thus allowing this type to always have a perfect amount of lean for any given corner. This type of trike usually tilts in it's entirety and is usually very complex. My green trike is this type. It can input steering regardless of lean angle.
  2. There are those that have no separate steering function and the front turns in relation to the rear as a direct consequence only of the angle of the pivot for the lean. This type are much simpler and the angle of lean is often not matched to the corner being taken. This is that type, as is the design it is based on, and is called a "tilt steer". The tying of the two functions is where the name comes from. In almost every case of this design only some of the vehicle actually tilts as it needs to have a non-tilting part to tilt against.
 
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Sorry I was trying to point out in the wider recumbent world , Bent Rider Online and WHPV and BHPC etc these terms have specific meanings and your phrase tilt steer is not used.

However of course it is your thread and project and you can call it what you like , sorry.



This tilts but does not use it for steering it has an independent steering function !
 
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No worries Paul. I don't read those forums on a regular basis but have scoured at least BRO for some articles. It's possible I've scoured the others but can't be sure. The system of fixed steering and leaning has been called tilt steer or lean steer (same thing) or not named at all on any number of articles I've read but I've never seen any other moniker given to the system.
 
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