"Free to Caster (FTC) leaning reverse trike

[purplepeopledesign]

I have been doing some experiments with FTC and have discovered that the low speed problems are due to uneven weight distribution fore and aft of the inclined axis of the fork. i.e. the wheel leans disproportionately because gravity is the dominant force, dragging the heavier side down. If the weights are equalised, then the effects of gravity are neutralised and the steer to lean ratio remains constant.

That explains part of it of the cause. I was pointing out the net effect of the characteristic. Any automobile can do a minimum radius turn in both forward or reverse at less than walking speed with the steering at full lock. FTC cannot do this without forcing the rider to deal with an uncomfortable tilt angle without the corresponding lateral G force.

ensen.

 

[chaster]

*EDIT - actually, I do know of an FTC vehicle that is only 2 wheels: the Dirtsurfer (an offroad skateboard which has a FTC front wheel). Google it to see some cool videos.

hmmm, a dirtsurfer is very similar to no hand bike riding, (see also bike surfing)
a negative head angle with lots of trail.

the reviews i read is that dirtsurfers are bad for tight turns.
I seen videos of them going around tight corners, very awkward.

Look, I understand your skepticism, but it's not a good example for FTC for a forced tilt vehicle since it's only 2 wheels (singletrack). As I distinctly pointed out, two wheels FTC is not the same as 3 or more wheel FTC. FTC on two wheels is OBVIOUSLY going have difficulties turning at slow speeds *because you have to balance a two wheel vehicle*.

EDITED to be a little less inflammatory..

 

[chaster]

I have been doing some experiments with FTC and have discovered that the low speed problems are due to uneven weight distribution fore and aft of the inclined axis of the fork. i.e. the wheel leans disproportionately because gravity is the dominant force, dragging the heavier side down. If the weights are equalised, then the effects of gravity are neutralised and the steer to lean ratio remains constant.

That explains part of it of the cause. I was pointing out the net effect of the characteristic. Any automobile can do a minimum radius turn in both forward or reverse at less than walking speed with the steering at full lock. FTC cannot do this without forcing the rider to deal with an uncomfortable tilt angle without the corresponding lateral G force.

ensen.

*EDIT* I was confusing authors of posts. Apologies.

Every system has it's own set of strengths and weaknesses. An FTC vehicle must take low speed maneuverability issues into account. Yes. But there are many solutions to this "obstacle". A far greater obstacle is high speed stability, simplicity, and safety - and FTC excels in all of these areas. How many other systems can claim the same?

The purpose of FTC is to make narrow multi-track tilting vehicles stable at high speeds & all non-catastrophic dynamic conditions, provide simple steering, high speed responsiveness and maneuverability, and mechanically simple yet robust implementation. Put another way, FTC fixes the weaknesses of two-wheel single track transportation. An FTC vehicle allows you to enjoy the benefits of tilt dynamics (stability in a narrow vehicle) but it eliminates dynamic weaknesses of single track vehicles (need to balance the vehicle, manual countersteer training, low sides, high sides, tank slappers, etc.). And it does it all without having to resort to sophisticated (and failure prone) electronics. You might not share my opinion about the cost/benefit ratio of FTC, but I think it's quite favorable.

I said it before, and I'll say it again - there are numerous ways to address the low speed steering in FTC. If you don't want to consider them, fine. But dismissing the whole idea of FTC because you don't/won't consider anything more than an overly simplistic implementation is a bit close-minded, IMHO.

I think that's about it for me. I leave the rest of the discussion as an exercise for all of you guys to explore on your own. There's a lot of info out there if you're willing to go look for it and actually investigate...

Eric

 

[oatnet]

Wow, FTC Is slick!

-JD

 

[sk8norcal]

The key to FTC is that you are reversing the dynamics of control. Instead of steering first to drive the tilting, FTC uses tilting first to drive the steering. On a bicycle this isn't a good comparison because it's a vehicle that depends on balancing. Yes, you can "drive" a bicycle without hands on the handlebars, but it's not quite the same as a multi-track vehicle forcing tilt. All the FTC vehicles I know of are at least 3 wheel, and they utilize the outboard wheels to drive (push) tilt.

this is the part I am not seeing.
someone needs to draw up a simple wire frame cad drawing for FTC.

Every system has it's own set of strengths and weaknesses. An FTC vehicle must take low speed maneuverability issues into account. Yes. But there are many solutions to this "obstacle". A far greater obstacle is high speed stability, simplicity, and safety - and FTC excels in all of these areas. How many other systems can claim the same?

MP3? from the videos I have seen for Piaggio MP3. the mechanism looks very simple, seems to do high speed fine, corners great and probably safer than a 2 wheeler.
I am not seeing how FTC is gonna be much better than this...

anyways, good info,
gonna do some digging..

 

[sk8norcal]

I like the 4MC,
its skid pad performance on wet oil is impressive..

here's my list of leaning 4 wheelers
http://tiltingvehicles.blogspot.com/search/label/Motorized%20-%204%20wheels

 

[sk8norcal]

thx, Marvin.
I was inspired to start that blog after seeing the Maxmatic site a long time ago,
it's a great site but he stopped updating it years back.

I just posted three more,

check out the highside video..
http://tiltingvehicles.blogspot.com/2010/09/university-of-padua.html

interesting videos,
http://tiltingvehicles.blogspot.com/2010/09/university-of-minnesota.html

another electric tilter,
http://tiltingvehicles.blogspot.com/2010/09/e-snake.html

 

[chaster]

MP3? from the videos I have seen for Piaggio MP3. the mechanism looks very simple, seems to do high speed fine, corners great and probably safer than a 2 wheeler.
I am not seeing how FTC is gonna be much better than this...

anyways, good info,
gonna do some digging..

You'll have to do the investigation yourself, but I'll try to give you some additional info to perhaps direct your line of query...

Regarding the MP3. I agree, the MP3 is a definite improvement (safety-wise) compared to a motorcycle. The Piaggio MP3 is basically a motorcycle with two front wheels. Nothing wrong with that. It's definitely an improvement. But, it's just an incremental improvement. The extra front wheel provides additional traction and allows the vehicle to stay upright at a stop without the driver necessarily putting his feet down.

However, what it doesn't do (that FTC does do) is the following:

1) Eliminate the need to countersteer. You still need to know how to "drive" a motorcycle, which means training your brain to countersteer. This is nonintuitive. That's okay, but nonintuitive controls are dangerous in emergency situations. If a car suddenly pulls out in front of you, and you need to swerve left, your brain needs to remember to briefly countersteer *right* in order to go left. Even if your brain remembers this, often times, it can cause a slight hesitation, which can be fatal when the difference of a fraction of a second means crashing or not crashing. Of course, people can make the (valid) argument that "expert" motorcycle riders will countersteer without the slightest thought or hesitation. However, how many of these expert motorcycle riders are out there compared to car drivers? How many motorcycle drivers drive their motorcycles only on occasion and drive cars most of the time? The basic fact is, people are accustomed to car-style steering (aka "simple steer") as opposed to motorcycle-style steering (aka "manual counter steering"). FTC eliminates this extra layer of complexity - to go left, turn left. To go right, turn right.

2) Provide real dynamic stability - anyone who has driven a motorcycle for a while knows that low-side crashes (where you lose traction in a turn and the bike slides out from under you) and high-side crashes (when you try to turn too sharply at a given speed, and your CG moves outboard of the balance line) are always a danger. The MP3 improves on this situation by enlarging the traction foot print and enlarging the balance line into a balance triangle. However, it does not eliminate these dangers. It is still possible to low-side (difficult) or high-side (not very difficult) an MP3. FTC *eliminates* these dangers. If traction is lost in an FTC vehicle, the FTC wheels immediately re-orient to instantly (and I do mean *instantly*) regain grip. Low-sides due to traction loss are literally impossible (again, this is assuming a multi-track FTC vehicle). Likewise, in a potential high-side situation, because the driver is controlling the TILT of the vehicle, the FTC wheels are forced to accommodate the desired tilt by orienting themselves to match the physics dictated requirements for that tilt angle. In a high-side situation, the vehicle will not high side, it will follow a larger radius arc than the driver desires. Consequently, the driver's own senses will tell him/her to slow down - bringing the vehicle back to the desired line of curve. In essence, FTC provides "free" dynamic stability control - without any sensor, computers, or complex electronics.

Eric

 

[purplepeopledesign]

I said it before, and I'll say it again - there are numerous ways to address the low speed steering in FTC. If you don't want to consider them, fine. But dismissing the whole idea of FTC because you don't/won't consider anything more than an overly simplistic implementation is a bit close-minded, IMHO.

Who said I was dismissing FTC? I like it, but it has this issue with practicality. Now, I can't see a way to implement low speed control without getting more complicated and actually over-riding the "free" part of FTC... IOW, actively controlled steering angles, but maybe you can elaborate for those of us with little to no experience in tilting vehicles.

ensen.

 

[sk8norcal]

You'll have to do the investigation yourself, but I'll try to give you some additional info to perhaps direct your line of query...

thx Eric, please do.

I see the two points you mentioned, simple steer and lowside/highside proof.

so have you ridden any FTC vehicle?

you mentioned some experimentation for the Xenopi project.
any pics?

Tilting Mechanism: FTC (Free To Castor) with PHACS (Passive Hydraulic Automatic Counter Steer) enhancement

I am assuming this is not FTC..

 

[sk8norcal]

hey Marvin,

here's a leaning 4 wheel scooter that I own,
used to be called the Quadcarver, now Fusion.
the inventor is a skater that I met through slalom skating.

http://wackyboards.blogspot.com/2009/07/fuzion-quadcarver.html

I think he is now involved with the Zuumer
http://wackyboards.blogspot.com/2010/04/zuumer.html



Eric,
now would this K2 scooter be considered FTC ?
no direct steer, lean to steer.
both wheels are linked together with a centering spring.
http://2.bp.blogspot.com/_Q1dyW07vBRo/St1kLS-pnYI/AAAAAAAABaI/FFOU4dpx7fw/s1600-h/k2+kickboard.gif

 

[chaster]

I said it before, and I'll say it again - there are numerous ways to address the low speed steering in FTC. If you don't want to consider them, fine. But dismissing the whole idea of FTC because you don't/won't consider anything more than an overly simplistic implementation is a bit close-minded, IMHO.

Who said I was dismissing FTC? I like it, but it has this issue with practicality. Now, I can't see a way to implement low speed control without getting more complicated and actually over-riding the "free" part of FTC... IOW, actively controlled steering angles, but maybe you can elaborate for those of us with little to no experience in tilting vehicles.

ensen.

I'm just telling you it works. You seem to want proof that it works at low speeds. The first (pre-SPARC) prototype had an optional FTC system in place, and it worked - even at low speeds. Tom Blackburn's system is completely FTC *at all speeds* and he not only reports there is no problem with low speed maneuvering, he posted a video showing proof (he maneuvers out of his garage, around his driveway, over gravel, down mountain roads, on high speed roads (getting up to 80 mph), backs up, 3 point turns, etc. etc. etc.). If you can't believe a live video, then obviously you aren't going to believe anything I tell you in text in a forum.

Eric

*EDITED for clarity

 

[chaster]

You'll have to do the investigation yourself, but I'll try to give you some additional info to perhaps direct your line of query...

thx Eric, please do.

I see the two points you mentioned, simple steer and lowside/highside proof.

so have you ridden any FTC vehicle?

Yes, I have. Back in college - the downhill soap box derby racer we built was FTC. That gave me enough confidence to believe in the FTC idea in general. True, it was "just" a soapbox derby racer, but it got up probably over 30 mph in some parts, and it worked fine. And that was a bunch of junk put together by a buncha college dorks who weren't even paying attention to things like castor or rake or ackermann or suspension travel. We were just having fun. =)

you mentioned some experimentation for the Xenopi project.
any pics?

Tilting Mechanism: FTC (Free To Castor) with PHACS (Passive Hydraulic Automatic Counter Steer) enhancement

I am assuming this is not FTC..

Actually, Yes and No. :lol:

That's prototype #2 (it's actually a 2 seater). I've dubbed it the "SPARC". It is designed to convert from regular car-style steering to FTC steering by removing a pin that joins the handlebars to the steering crank, and adding a pin to tie the handlebars to the shock balancer (the semi-triangular shaped structure that the two front shocks are tied to). However, at this point, the vehicle has not been changed to FTC because it still needs to have the drive components (motor, battery pack, controller, etc.) installed, and I want to get it licensed and tagged with just standard steering to avoid any objections from DMV (as I'm not sure how they will respond to seeing a design where the driver does not have a direct mechanical connection to steer the front wheels).

I really need to update the blog on the SPARC. Many things to blog about, but my day job deadlines are killing all my discretionary time (along with lots and lots of home projects).

 

[chaster]

Eric,
now would this K2 scooter be considered FTC ?
no direct steer, lean to steer.
both wheels are linked together with a centering spring.
http://2.bp.blogspot.com/_Q1dyW07vBRo/St1kLS-pnYI/AAAAAAAABaI/FFOU4dpx7fw/s1600-h/k2+kickboard.gif

Hard to tell from the picture. Can the wheels steer independently of the tilt? If not, then it's a skateboard, not FTC. Traditional Skateboards aren't FTC - the wheels on a skateboard have a fixed steer/tilt ratio. FTC requires the steering wheels be allowed to adjust steering for both speed and tilt.

Eric

 

[sk8norcal]

Yes, I have. Back in college - the downhill soap box derby racer we built was FTC.

yes, you mentioned that, got picture?

also, in the early 90's, I vaguely remembed at ASME HPV a FTC (2 wheels rear), a wobbly ride if I recalled...

Actually, Yes and No.

that's interesting your SPARC could be easily converted...

 

[sk8norcal]

Hard to tell from the picture. Can the wheels steer independently of the tilt? If not, then it's a skateboard, not FTC. Traditional Skateboards aren't FTC - the wheels on a skateboard have a fixed steer/tilt ratio. FTC requires the steering wheels be allowed to adjust steering for both speed and tilt.

Eric

this steering system is pretty unique,
(in real test, it doesn't ride that good)
it was originally invented by Ciro
http://wackyboards.blogspot.com/2009/07/ciro.html
(i guess its not a real FTC)

 

[chaster]

Yes, I have. Back in college - the downhill soap box derby racer we built was FTC.

yes, you mentioned that, got picture?

Sadly, no. I really need to get in the habit of taking more pictures of my "projects"... I just never feel like documenting... :?

also, in the early 90's, I vaguely remembed at ASME HPV a FTC (2 wheels rear), a wobbly ride if I recalled...

Actually, Yes and No.

that's interesting your SPARC could be easily converted...

Well, it was a compromise. The frame builder wanted to re-purpose the frame design as a kit for non-tilting trikes. He has since sold at least one version to another EV guy that I know (Nap Pepin of Lithium Ion BugE fame). Unfortunately, that compromise has turned out to be quite a headache in some ways, but I can't say I haven't learned a lot...

Eric

 

[sk8norcal]

http://tiltingvehicles.blogspot.com/2010/09/quadro.html

[youtube]v2OJa-vWEaE[/youtube]

 

[michaelplogue]

That Quadro is pretty darn cool! Unfortunatly, I think you would have a hard time getting it licensed/registered, as most places consider any vehicle with four wheels on the ground as a car - not a motorcycle. And since it wouldn't meet the safety standards of a car, they would not allow it on public roads.

 

[sk8norcal]

hopefully, the laws will be made to allow these vehicles.

how about GG Quadster?
http://www.motorcycle.com/manufacturer/2008-gg-quadster-review-80257.html

Quadro have a 3 wheeler also,

[youtube]9mUYA6F8xWk[/youtube]

 

[PedalingBiped]

I really like the Quad, so stable.
As far as laws, I don't have any knowledge other then yours about 3wheel or 4 wheel.
But, I would like to think that restricted wheel base, in-line passenger sitting or not having a cockpit or cab would help define it as a motorcycle.

 

[amberwolf]

Unfortunately at least some, perhaps many laws define bicycles *and* motorcycles as vehicles "having no more than three wheels in contact with the ground", or similar wording; they can have more wheels but they can't all touch the ground at the same time (training wheels, for instance, or other stabilizers, that don't both touch the ground at the same time as both regular wheels on a bike).

 

[chaster]

It's unfortunate that the US state laws define anything with 4 wheels as cars (unlike most European markets - where they have a 4 wheel motorcycle category). It would really be nice to have the quad cycle here with dual wheel drive for lightly snowy roads

Eric

 

[sk8norcal]

[youtube]CUT3imO17qE[/youtube]

 

[sk8norcal]

http://tiltingvehicles.blogspot.com/2010/10/trecolith.html

[youtube]espjJmF5IJM[/youtube]