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Balor Posted - 02/05/2020 : 10:54:04
Did anyone try that on a leaner?

For instance, stick steering, left - roll (connected to side wheels), right - yaw (steering).

Besides 'multitrack' mode on demand (no need to keep balance when you hold on to your roll axis control tight, hence unlimited static and straight ahead dynamic stability) and ability to resist truck suck and wind gusts w/o steering input (that can be very important in case of tight quarters and traffic), there is a possibility of 'tilt plus' mode when you hit max lean and continue increasing your turn radius while resisting side force by riding the outside wheel.

You can reach crazy G's this way, essentially giving you a much wider track and much lower CG.

Am I missing something?
8   L A T E S T    R E P L I E S    (Newest First)
Balor Posted - 02/13/2020 : 15:46:35
quote:
Originally posted by modular1

Hi Balor

This thread bamboozled me a bit, slightly tricky diagrams. But I have done a bit of work on V-ilean having made a few examples. Engineering a V-ilean is not that hard, standard square taper unicycle cranks work for 90 degrees and isis cranks (https://www.unicycle.com/unicycle-hardware/crank-arms-parts/isis-cranks) offer a larger range of V angles.

I found 75mm unicycle cranks suitable for flat ilean, with standard cranks there is a lot of shudder / wheel skidding going round corners. I uploaded a spreadsheet to http://modularbikes.com.au/trike/ , this shows the amount of rise you get from trikes with v ilean. My experiencewas that even fwd trikes with fixed bottom bracket drive which influences steering can be ridden no hands with v ilean. Best Wishes Stephen Nurse, modularbikes.com.au

Stephen Nurse



Nothing tricky about it, just tipover resistance calculation, 45 deg of 'tilt plus' mode (line from tilted CG to outside wheel) means 1G of cornering that should be enough.

Thanks for the link to that spreadsheet! Interesting info.

I wonder if I'll be able to use 'V-lean' for better control on MBB bike like Cruzbike did? I'll just need to remove my rear wheel :)



iLeaning quad can be made RWD and with lean wheels just lightly touching the ground, immune to scrab, but still providing static stability and tilt plus mode when equpped with a lock or direct lean control.
modular1 Posted - 02/13/2020 : 14:33:47
Hi Balor

This thread bamboozled me a bit, slightly tricky diagrams. But I have done a bit of work on V-ilean having made a few examples. Engineering a V-ilean is not that hard, standard square taper unicycle cranks work for 90 degrees and isis cranks (https://www.unicycle.com/unicycle-hardware/crank-arms-parts/isis-cranks) offer a larger range of V angles.

I found 75mm unicycle cranks suitable for flat ilean, with standard cranks there is a lot of shudder / wheel skidding going round corners. I uploaded a spreadsheet to http://modularbikes.com.au/trike/ , this shows the amount of rise you get from trikes with v ilean. My experiencewas that even fwd trikes with fixed bottom bracket drive which influences steering can be ridden no hands with v ilean. Best Wishes Stephen Nurse, modularbikes.com.au

Stephen Nurse
Balor Posted - 02/07/2020 : 04:49:21
Refined the model a bit, things are weirder for V-iLean, one should not use 'full tilt' in this mode I presume because there is a 'toggle point' before the outside crank gets fully vertical, that basically stops lean action and only rises CG.
Unfortunately, that means I'll get about 70mm of lever to push against during 'tilt plus' cornering, that can get up to about 1500 of newtons! Hmm.

P.S. Obvously, making OUTSIDE crank fully vertical on V-configuration Ilean is possible only by manually nudging it with a lever, otherwise it stops leaning with inside cranks get vertical (pointing upwards)


I guess I'll experiement with V-ilean, but likely only very mild (like 170-165 deg instead of 180) variats are useful and practicable, and that can only be had by modifying fine-splined shimano cranks by removing the centering 'bump'...
Balor Posted - 02/07/2020 : 00:14:33
Yea, 20 deg of tilt is absolutely not enough for a FREE-leaning vehicle. However, things are much more interesting with a lean-controlled one! Do read the link I've provided, and notice the line from CG (that's at 300mm from lean axis... approximately, should not be higher I hope) to opposite wheel:

In free leaning vehicle, if you try to 'overlean' the tiltstops, you will be pulled upright and crash (rather violently I presume) on the other side.
But hittting max lean and LOCKING it there (or in controlled lean case - simply resisting the 'reversing' moment manually, and like I said - iLean is great here because that force is going to be very low due decreasing leverage) you'll get what amount to a multitrack HPV with much wider track and a bit lower CG.

Talking of lower CG! The resistance to self-righting comes from two forces - a moment from displacing CG laterally (that's a GOOD one, because it adds resistance to side forces) and the force you need to rise your CG. It is not unlike steering a with horizontal steering angle and infinite trail - you get HUGE 'flop' force. Bad thing about it is that flop force provides resistance to self-righting, but does not contribute to better cornering (well, actually it does due to lowering of CG... but that comes in tandem with cg displacement that provides the continuous counter-torque).

If you add self-righting force in terms of a return spring for instance, that would make self-righting easier BUT it will be deducted from the leaning torque you generate to counter centrifugal force (Levand aptly linked to 'zero gravity bicycle' in an other thread).

But enter V-configuration iLean!

https://imgur.com/a/MM5I0ys


(that's 140mm long ISIS cranks one 'notch' off)


At max lean it actually rises CG due to asymmetry of cranks, hence compensating for CG lowering effect (to a point of course, but in THIS case it does it almost completely).
So, your self-righting force is going to be nearly an order of magnitude less (less than 4mm of 'flop' vs 28mm of flop at max lean)

Unfortunately, in MY case (diamond quad) the fact that middle wheels are located between the 'main' wheels complicates things even further - I'll be robbing main wheels of traction and like on a Pulse will be rising my rear wheel.
How bad is that, and how much varying suspension sag can help with that is to be determined, I suspect that would end up either not helping much, or unusable...

Maybe I should rethink entire concept and go for a more conventional FWD iLeaning tadpole with narrow track and controllable tilt? I can have a battery in the nose for a 'counterweight'... but that implies fully loaded small wheels and suboptimal 'multitrack' mode.

"Blimey, that redistribution of wealth is trickier than I've though!:" (c)
purplepeopledesign Posted - 02/06/2020 : 16:56:49
I'm getting about 0.36G and just under 5 kph for a 5m radius turn at 20 deg tilt angle. If that's correct, then mechanically limiting tilt to 20 deg will be easy to roll over.

That figure seems a little low to me. Would someone else double check, please?

:)ensen.



Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
Balor Posted - 02/06/2020 : 14:40:10
Horn's S'trike (and his follower Greg and his Rocket) had positive 'trail' of tilt steering... but anyway those are 'mere multitrack' vehicles anyway and indeed do no solve high speed rollover problems with narrow track that I desire, only allow for easy direct FWD.

Independent control
- Requires highly skilled operator to account for combinations and changes of corner radius and velocity
- Very high self righting force required as speeds come down to zero"


Now that is interesting... and rather ominous, because I'm anything but a 'highly skilled operator'.

However, shouldn't one simply steer like a single-track HPV and use (the) force only to correct for unwanted disturbances w/o steering input, low-speed stability and 'tilt plus' mode?
Have you tried something like Tripendo? It seems to work well, but likely too complex and a bit of an overkill for an unfaired HPV... I think it is an overkill anyway because Tripendo has pretty wide track and hence should have enough stability even w/o leaning... and I'm not sure even 'tilt plus' mode allows for 2+G turns w/o very serious (motorcycle) rubber that in turn require more than mere human power.

As for self-righting force... to 'untilt yourself' from a lean of 45 deg using one hand only and using one lever with limited throw is, indeed, pretty much impossible.
Does Tripendo implement 'power-assisted lean control' as well I wonder? It does have a rather suspicious box...

HOWEVER, my goal are relatively modest - to have a *narrow track* vehicle that has a viable means of reaching 1G of cornering, but allows for static stability and 'tilt plus' mode, as described in this article:

http://lefthandedcyclist.blogspot.com/2018/

A very limited 20 deg leaning PLUS multitrack dynamics should allow me to have a 1G of cornering force given about 2 feet of track and 20 inches high CG.



Since I will not need to have a very long lever throw to control for 20 deg of lean, have relatively wide track and low CG for a tilter (still not enough for true 1G of rollover protection though), AND iLean have unique property of reducing leverage forces have over your bars when as you lean deeper because cranks get more vertical, and as they get truly vertical at max tilt - no effort is required to make them stay there because lever is zero, a natural 'tilt limiter'.
I'll need to run numbers on that anyway... there is likely zone in the middle where forces get too great (because of overall porkyness) There should be enough leverage to control for truck suck and wing guts to be sure.

Btw, about inherent iLean wheel scrab. I think that is not actually a bad thing. Wheel scrab forces (due to increasing wheelbase) resist leaning, not forward motion and serve as 'tilt damping', giving you a wider window for steering corrections as you lean to and fro (like a higher CG).
purplepeopledesign Posted - 02/06/2020 : 10:46:06
Based on photo research you probably already know that tilting trikes come in mostly 3 types of dynamics - linked tilt steer, independently controlled tilt and steering, and free tilting. The first two also have inherent control over the maximum tilt angle. The third may or may not have an end stop for maximum angle.

Each has pros and cons. Since almost all articles and posts on the web will tout the various advantages, I will just list the disadvantages that I know of.

Linked tilt steering
- Cannot account for differing combinations of corner radius and velocity, often leading to high-side crash
- Will oscillate above the speed at which negative trail overcomes self-centering force from weight

Independent control
- Requires highly skilled operator to account for combinations and changes of corner radius and velocity
- Very high self righting force required as speeds come down to zero

Free tilting
- Tilt lock requires reversal of control inputs during transition when in motion
- Will not stay upright at zero speed

Several commercial tilting trikes. Probably the most common is Piaggio MP3. It is free tilting but actually uses rider leg strength on pedal boards to stay upright at stop. The pedal boards transfers to the ground the effect of the rider putting a foot down This is not feasible for a pedal powered trike.

The Carver trike has independent control where the tilt angle is computer controlled and hydraulically actuated. While workable, the extra weight and complexity make this very impractical for a pedal powered trike. Without being involved with any of the motorized projects, I think the weakness is that the hydraulic system cannot be made at reasonable cost to be fast enough to keep up with transitions at high speed.

:)ensen

Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
Balor Posted - 02/05/2020 : 22:51:06
Oh, Tripendo, right. And some homebuilds, too. Seems to work!
Bit complex though for a tadpole configuration, but in my case it is quite simple...

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