Testing "Camber Thrust" With Camber

I've read articles explaining "Camber thrust" theory but never seen any real world evidence of the effects of camber on a bike in a similar way that Bill Milliken did with his MX1 "Camber Car". Often wondered how to do that but couldn't think of an easy way until the 2WS Demo Bike construction was almost done. Replacing the 2WS Demo Bike forks with 30 degree cambered forks, but with only one wheel steering, was fairly easy.

The cambered tire contact patches had to go in precisely the same place relative to the steering axis and with identical ride height. The constant radius (26mm) of the Maxxis Hookworm tread profile was very helpful with getting the geometry right in the jig and for maintaining contact patch symmetry.

So why bother? Every single explanation I've read (Or watched on YouTube) was analogous hot air, markerboards, cone shaped objects, inappropriate tires, etc... NO tests with camber on bike tires. The science of single track vehicle dynamics shouldn't depend on tenets of faith and devotion.

A 3D bike tire surface interacting with a stationary 2D road surface does . . . what? Bike tire diameter differential at the contact patch is fixed for any given tire, yet it will track with no otherwise different input over an infinite variety of corner radii and lean angles. And if it rolls straight because of equal diameter on either side of the contact patch, it shouldn't go straight gracefully when bike tires are cambered.

Not all single track vehicles have tires yet steer and handle the same - single track vehicles have been ridden with large round sawblades and ice skate blades - NO camber thrust there. The most basic single track vehicle is a simple disc with a sharp edge - roll it across a hard surface and watch roll along gracefully until it turns gracefully in decreasing circles as it slows until, fully depleted of grace, it falls down - NO camber thrust involved, is there? 

Yes, it really messes with your head at first when you look down and see the front wheel in action - that must do something different, right? What is different: Tire scrub (Which was expected) and lateral displacement on bump (Not expected but easily figured out). Rolling resistance increased even more with right turns. Rolling resistance decreased a lot with left turns. As it rolls, the tire's leading surface moves to the left before it makes contact: Step shaped bumps would move each end of the bike over to the right. Wave shaped bumps would move each end of the bike in a right/left motion. 

Otherwise, completely normal. The steering and handling was exactly the same. NO tendency to veer, dart, shimmy, weave, careen, squirm, yaw, crab, etc... Braking either/both wheels and acceleration was normal. It tracked effortlessly and predictably, turning either direction or straight ahead. 

Ergo: NO camber thrust. 

While this is obviously not an SAE level technical publication or doctorate level dissertation, the methods and results are clearly reproducible. As always, it is very satisfying to roll something finished out of the shop, test something unproven, and have an awful lot of fun doing it. 

PS: Inquisitive of moto-heresy? Bike and associated components are for sale - email me if you're interested...

2WS And Lean Angle...

Took a little time away from the new racer project and made a cheap and easy to build electric 2WS demonstration bike. I've known about the effect of 2WS on lean angle for decades, but never effectively demonstrated it. The end of the video has frame grabs that illustrate the 2WS effects on lean angle and front wheel steering angle.

Numbers: 

• Weight with battery 62 pounds. 
• Wheelbase 53 inches. 
• Head tube angle at both ends 0 degrees. 
• Trail at both ends 1.4 inches. 
• Weight distribution with rider 60% F | 40% R. 
• RWS settings 0%, 50%, and 66%. 
• Hubmotor 48V 1000W. 
• Battery capacity 20 Ah.
• Top speed 24 MPH.

I've never tested 2WS beyond 50% RWS - was afraid it might become unstable past that point. But not knowing something is supposed to be good motivation to learn something rather than rationalize FUD - do the research! At 66% RWS, it worked far better than I expected - it never did anything evil, even if it felt weird at first. While good low speed behavior doesn't always correlate with good high speed behavior, good research results encourage development work. 

The rear hubmotor was sold as a front hubmotor for an electric bicycle "Pedal Assist" system - it won't go unless the rider is pedaling. No crank means no pedaling, so the sensor trigger ring was chucked in the lathe, bored out, and pressed onto the hubmotor bearing boss. The sensor bracket was cut down and welded to the fork dropout. It works very well - not sure how legal that is! The 3 speed settings give a maximum indicated 14, 19, and 24 MPH. After the motor controller is turned on and bike is rolled forward a few inches, it takes off from stops with just the throttle.

I wanted the steering ratios to be as accurate as possible. A simple jig that clamped around the fork crown made that easy. It only takes a few seconds to change the RWS settings by repositioning the link's rod ends on different bracket holes. Careful bracket placement made wheel realignment unnecessary.

The initial plan for observing changes in lean angles was to use a common digital speedometer and an old JVC action camera aimed to the outside of the turn and bolted to a welded-on frame bracket - low risk of inconsistent results with a consistent and repeatable perspective. But then the idea of using a Speedangle Apex lap timer (With lean angle indicator, GPS speedometer, and data logger!) sounded like an even better idea. Experience ended up proving otherwise - the Speedangle unit gave very inaccurate readings with 2WS engaged - even worse at 66% than 50%. It is otherwise a very nice unit, but obviously not developed for unconventional motion analysis. So back we went to the first layout: Consistent speed (15 MPH) over a consistent radius (42 feet) gave the consistent results needed. I can't tell you the lean angle difference measurements, but those differences are obvious. 

While this is obviously not an SAE level technical publication or doctorate level dissertation, the methods and results are clearly reproducible. There's enough information and breakthrough potential here to get really excited about it all if you can comprehend the possibilities. Meanwhile, it was very satisfying to roll something finished out of the shop, test something unproven with better than expected results, and actually ride. 

Connected Dots

Made enough progress with the frame to install the upper A-arms and dummy shocks (Half travel length). Next steps: Finish the frame with some triangulation and finish the steering system. The lower suspension arm (Left side) is laterally located by Watt's linkages (Not installed but on hand) to the right-side lower tube. 19th century bicycle technology won't work.

Another minute and a half of fame - wasn't involved with the production of this one, either - still glad to see enthusiasm for it out there. Lots of fun comments and the usual stupid comments:

Next one should be a lot more fun in the real world when it's done.

Milestones...

Finally got to that stage of frame fabrication where I could prop it up and fit check it. It's a fun moment to shoot and share - that picture is also a valuable ergonomic reference. That moment is also an important milestone - it's no longer just endless work toward an impossibly distant abstraction - it's strong motivation to see it roll for the first time (Next milestone) and first test ride (Last milestone). 

Normally, I tack weld the entire frame assembly together, fit check it during some stage of that, then finish weld it (Including capping open tube ends) when there's nothing left to add. This time, some tubes had to be trimmed, capped, and finish welded before continuing on with the next operations. So off the bench it came, work was done, and, well, there it is.

The primary frame structure is done now - time to finish connecting the dots. According to the scale, this frame looks like it will weigh just over half of the last one. The suspension is already done - still have to make the steering system before I have a finished roller. I have no idea when I'll reach that milestone, but it is that much closer to getting there.

It's been too long since I've worn that helmet - this feels like it is going to be a lot of fun....

8 More Minutes...

Well, this was a fun surprise - I had no part in this video's production: 

Lots of fun comments and the usual stupid comments.

This is the original production:

More motivation to get the next racer done and tested in the real world - the only place that matters...

Latest on the first one....

Hanging over my desk, for many years now, was my first 2WS/2WD experimental electric recumbent bike. While leaning back in my chair and staring up at it recently, I wondered why a video wasn't produced as soon as it was done. Then it hit me: It was built and ridden about 3 years before YouTube was launched! It was designed and built almost a quarter century ago! It also hasn't been ridden in 8 years - time to take it down, dust it off, and give it a fresh set of tires and batteries! The paint exhibits some age along with wear and tear, but, well, so do I:

Inspiration behind this concept was written almost a third of a century ago - articles by Kevin Cameron about breakthroughs that could overcome performance limitations of conventional race bike design: Beyond Telescopic Forks, Cycle, January 1987 and Two-Wheel Steering, Cycle World, February 1992. And absolutely nothing since then:

It isn't just theory anymore - in practice, 2WS offers far more than the theory suggested - implementation was also easier than expected. And it is a lot of fun to ride.

But I'm expecting the next racer to be far more fun - off to the museum with the first one. It is in good company at the St. Francis Motorcycle Museum in St. Francis, KS. Ask the staff there - they'll gladly show you how the steering system works...

Going from 0 to 3D...

 The 2WS/2WD system for the next racer is assembled and on the bench! This is the first bike project of mine where the frame wasn't built first. Now the frame designs itself and gets built next. 

The engine is out of the donor bike. It is smaller in every dimension, 5 lbs. lighter, and over twice the horsepower of the EX500 engine in the last racer.

The engine goes up on the bench as soon as the left side gets cut down - have to make room for the front wheel drive belt. Started by milling down a gently used cover:

Speaking of engine weights, a number of engines have gone across my shop scale over the years:

Kawasaki KX500 - 60 lbs.

Kawasaki EX500 - 126 lbs.

Ducati 999S - 153 lbs.

H-D 883 4 speed - 185 lbs.

H-D 1340 Evo 5 speed - 215 lbs.

Honda CBX - 215 lbs.

KTM 890 - 121 lbs.

Getting to this point took a lot longer than expected - a combination of a serious workplace injury last summer (Off work for 4 months - they took care of me at their expense) and fading enthusiasm the rest of last year stalled progress for too long. 

 After a hard day at work, the last thing I wanted to do for fun when I got home was even more work. So why not take the night off and just crank up the Bluetooth speaker and relax out in the shop? Over There, staring me down, is the domineering markerboard. Yeah, the mill table should have been cleaned off last night - turning  the lights out on a messy mill table just isn't done. While we're at it, lets get the vise squared up and bolted down. Why not load the first part, stick the probe in the spindle, and zero out the DRO while everything is clean? Since we know where we are now, there's nothing to stop us from drilling the pilot hole. Loading the boring head in the spindle and setting the boring bit now should get the job done sooner. Hey, I'll bet that first cut will go really smooth - now's a good time to find out! The calculator says only 9.137 more passes will finish the job - the playlist on the speaker is nowhere near done and I forgot how much I liked that group - I hope the neighbors are enjoying it as well. Lets load the identical part that goes on the other end of the racer (Identical front and rear suspension has its benefits...) and give it a head start for tomorrow. Oh look - it's done already and I never noticed that the playlist must have ended a half hour ago and now the shop is deafeningly silent. On the way out the door, I get to erase that nagging line off of the markerboard and look back before turning out the lights with renewed enthusiasm. I'll clean the mill table off first thing tomorrow, after work...

One step closer answering that question "I wonder what it's like to go faster?" There's only one way to find out...

First thoughts and stupid comments....

 When the decision was made to build the last racer, the first 3 thoughts went through my head:

• This is going to be a lot of work.
• This is going to be a lot of fun to ride.
• This is going to generate a lot of stupid comments.
  

It was. And it was worth it!
It was. More fun than anybody else knows!!

Far less than I expected in the real world - none at the track!!!

But then there's the internet:

1. It's just the Akira bike!
2. It's just a Gurney Alligator!
3. It's just a two wheeled car!
4. It's just a scooter!
5. It's just a Quasar!
6. You'll die if you crash or run into something!
7. All those ball joints and rods kill steering feel!
8. Can't see where you're going on the track!
   
9. Can't steer properly if you can't move your body!
10. Can't stand on the pegs while riding over bumps!
11. Why don't I see them racing in GP or the IoM TT?
12. Low CG motorcycles are hard to balance!
13. Low CG motorcycles are hard to countersteer!
14. Driving a steered wheel requires negative trail! 
15. Two wheel steering is pointless and stupid!
16. There's no rake at the front end!
17. It needs streamlined bodywork!
18. If it was a good idea, (Fanboi Brand) would be doing it already!
19. (Insert vapid cliché here.)
20. It's too low for traffic!
21. Where's my lady supposed to sit? 
22. It looks hard to put your feet down at stop signs!
23. Where do I put my luggage?
24. That riding position is no good! 
25. Too many parts!
26. They're supposed to be simple!
27. Why won't you do it my way?
28. The rear wheel is steered the wrong direction!
29. Send me the drawings of your latest project.

1) OK - Akira references really are fun! A friend made me really cool race team logo from "Bartkira" many years ago. I had a bit of fun composing an Akira poster parody photo shoot using a forklift in an industrial park back in 2016. 

The movie bike is wonderful art for fictional anime/manga, but, sadly, terrible design for the real world. But unlike the dragged out for decades Akira "Projects", my previous racer was finished, tested, raced, and it worked. 

No, Mr. Otomo did not invent the recumbent motorcycle. See also: #5, below.

2) Considering the liquid cooled twin cylinder engine, 2 wheel steering, no steering head, virtual hub center steering front suspension, remote mount handlebar, and reclined seat and rider position, there are more differences than similarities. That said, comparisons are understandable; the 'Gator was the only recumbent motorcycle to get any decent coverage in this country from the legacy motorcycle media this century. 

No, Mr. Gurney did not invent the recumbent motorcycle. See also: #5, below.

3) I'm really happy to hear it isn't just another outdated two wheeled horse. 

While a bicycle with an engine is understood to be a "Motorcycle", a recumbent bicycle with an engine is somehow a "Car":

See also: #5, below.

4) If you can't tell the difference between a recumbent motorcycle and a scooter, then clearly this subject matter is way beyond your comprehension.

See also: #5, below.

5) That comes from Dunning-Kruger disordered dimbulbs and/or sociopaths with cognitive disorders exhibiting their trivialization tendencies on the internet. Difficult to discern, as the results are the same: The phrase "It's just a ...." consistently precedes stupid comments, regardless of subject matter.

No, Mr. Newell did not invent the recumbent motorcycle.

6) Crashed at medium speed early 2013 - crashed at high speed later 2014 - didn't die either time, as far as I can remember. Still have the helmet from both crashes - not a scratch on it. If you are colliding with stationary objects at the track, well, you don't belong out there.

Yeah, crumplezone face (Go ahead - click on that - I dare you) is far more desirable. 

7) No, they do not. Or at least they don't if Teflon lined rod ends are kept out of the system. Even quite  a bit of play is better than a little bit of binding - the play will only be noticeable when parked - while cornering, there is a load on the handlebars (That's where feedback comes from!) taking up any play that might exist, leaving that crucial front end feel completely intact.

Front end feel comes from changes in the steering load - a little change means a lot. NOTHING kills that feel more than having the rider's weight on the handlebars while trail braking. With a recumbent motorcycle, the handlebars are just that - bars for the hands - the level of feedback from the front end is amazing if there is enough trail to provide it. Hub center steered front ends often need less trail for stability, which also makes the steering lighter, but that also reduces front end feel - something too often blamed on "All those linkages". 

Another change in perception comes from the effects of stiction - a binding telescopic fork (There is no other kind) feels rigid and "Transmits" feedback very clearly. A binding suspension also loses traction very easily. What too many perceive as "Signal" from the front end is actually "Noise". It is too easy to confuse the absence of noise with a loss of signal; the lowest level signals were lost under a high noise threshold all along. Confidence in the front end shouldn't come from noise, but apparently, it does. 

Speaking of feel: Nothing else provides a better level of feedback than a riding position that spans the wheelbase - any change in traction and/or yaw shift is immediately felt. 

No, you won't read or hear any of that from the moto-infotainment outlets. They have no experience with the subject, nor do they want any. 

8) Yes, my line of sight while riding straight and level is quite a bit lower than usual - yes, that changes one's perspective quite a bit - one gets over it very quickly with some seat time. But when leaned over, my line of sight is no lower than usual - look at how high the rider's helmet is from the track when he's dragging his elbows. If you ever need to sit up higher to see where you're going on the track, again, you don't belong out there.

9) WRONG! Calisthenics are part of the operation of current racing binary unicycles, but single track vehicles designed to use both wheels full time are steered with the handlebars. 

If you really want to find out how effective "Body english" is for stabilizing a bike, run a pin through the steering head of a bicycle so it can't steer. Now hop on it and ride it using all of that body english that "Worked" before. 

Didn't work, did it? 

10) Adequate suspension works far better than standing on the pegs - or at least it does on paved racetracks. That reclined seat and rider position makes tailbone impacts nearly impossible anyway.

Look at the driver's position of a modern F1 car - now compare it to mine. Ever see an F1 driver stand up for a bump? Ever see anyone in any 4 wheeled vehicle with seat backs (Including race karts) stand up for a bump? Are motorcyclists really that stupid about what suspensions do and how real seats (As opposed to saddles) work? The answer to that, it seems, is both obvious and pathetic.

11) They are cleverly banned by the ACU without overtly stating so - read "Road Racing Standing Regulations 2022", section 15.6.7 . 

The FIM rejected Morbidelli's request to race one in the Grand Prix classes.

That leaves USA club racing and track days - I'm more than happy with that.

12) Motorcycles, at operating speed, are not balanced by the rider - they don't fall down on their own. There are plenty of videos out there of riderless roadracing motorcycles rolling right along without anybody balancing them. Sure, at low speeds, such as waiting in line for tech, stopping at the grid, or heading back to your pit, the rider has to balance the bike. But at operating speed, a single track vehicle is a dynamically stabilized system, NOT an "Inverted pendulum" or static unstable object like a short broom handle. Static unstable objects like a short broom handle can fall in any direction - a single track vehicle can only fall in one of two directions. 

Back in 2005, I still wasn't sure that a recumbent motorcycle with a low and laid back seat would be a viable road racing vehicle - could the rider effectively operate the bike in a competitive environment? Finding the answer seemed like a wise idea before building a 2WS racer. So I modified a stand-up gas scooter and took it to the kart track in Calhan. 

Steering was perfectly calm and predictable to the point of easily dragging the seat at a 42 degree lean angle. At least a dozen others rode it - ages ranging from pre-teen to middle aged - they all had a blast on it. It would go just over 40 mph on level ground. Mission accomplished: It was restored back to its original configuration and sold so I could build a 2WS scooter based mini-moto racer. In 2006, I did - with an even lower seat:

It was even easier to steer and balance. No such thing as "Too low" for stability and control. Sufficient lean angle clearance is another matter. Weight transfer IS NOT an issue for a long wheelbase 2 wheel drive/2 wheel steering motorcycle. 

13) One of the most idiotic misconceptions I hear about single track vehicle dynamics is that, if the CG is low enough, the side force from countersteering moves the CG sideways instead of rolling it. That is impossible - inertial physics isn't affected by scale. The closer the CG (And roll axis) is to the contact patch, the less it has to move to attain and maintain any given lean angle. 

What DOES negatively affect countersteering is a high polar moment about the roll axis: The greater the distance between heavy components, (Rider, engine, full fuel tank, battery, etc...) and the contact patch, the slower the roll response. That's where a recumbent configuration excels - the distance from the roll axis of those component CGs can be a LOT less than a conventional configuration. That's also why the rider does not need to move around the bike: the rider's CG isn't otherwise having a massive effect on weight transfer. Mass centralization is a good thing - it's even better when it includes the biggest mass of all: The rider.

Physics says so. Testing says so. Social media's loud-mouthed dumb kids will still say otherwise...

14) No, it does not. A driven wheel does not behave through the trail moment arm the same way a braked wheel does. Why? Simple: The driving force is always inline with the trail moment - NO side force applied - any stabilizing side forces otherwise acting on the trail moment have the same effect regardless of the driving force. Physics says so. Testing says so. Yet the Facebook pseudointellectuals "Know" otherwise...

15) 2WS has been extensively tested here, but you'll never know it if you only read the legacy motorcycle media. The quality of the consumer comments says a lot about the quality of information they're given to consume:

MORE intellectualized ignorance about 2WS from the Facebook moto-gossipers!:

What a profound declaration of intellectualized ignorance: 

Discover something through research in the real world! Earn opposition from moto-gossipers! Here's your meme:

16) That comes up a LOT - easy to understand why - it sure looks that way! But the steering axis runs down through the upright's top ball joint (Obvious) to a virtual pivot point 1.7" ahead of the front axle (Not obvious) at a 12 degree angle, with just over 4" of trail. That geometry works perfectly well on this machine - NO weird behavior at any speed or lean angle. A far higher level of pitch stability tolerates much faster steering geometry than normal. And with remote steering, ergonomics doesn't dictate steering geometry anymore.

17) Yes, indeed it does. Beautiful and effective bodywork would be wonderful! But if I can go fast and have fun on a motorcycle without extensive bodywork, then I'm not sufficiently motivated to do that much more work. The next racer will have as little bodywork as I can get away with: Seat, tank, belly pan, number plates, airbox, and . . . nothing else. 

18) Brand supremacists are both annoying and stupid.

19) If you want to prove that you can't compose an intelligent thought, just stay on the couch, and post one or more of these, preferably under the influence of alcohol:

• Just because you can doesn't mean you should!
• An answer to a question nobody asked!
• A solution looking for a problem!
• It's been done before!
• Reticulated [sic]!
• Incumbent [sic]!
• Nothing new!
• Death trap!
• Fugly [sic]!
• Gay!

Stupidity and illiteracy are a natural fit:

Stupidity and illiteracy and FUD are an even better fit:

Stupidity and illiteracy and FUD and too much time on the couch and alcohol:

Help yourself to the passive-aggressive word salad bar:

Go back for another helping:

20-23) Irrelevant on a race bike - ought to be obvious, really. The worst grasp of the obvious combined with best grasp of FUD (I.e., "Peak Stupid"), at the time of this edit, is on ADVRider 

24) Roadracing motorcycles are the only high-performance motorized vehicles that don't use that position. Or at least not yet. Land speed record motorcycle racers have been using that position for well over half a century. Air racers and formula car racers operate in that position just fine. That position is safer, faster, and vastly more comfortable than the archaic horseback riding position. 

25) Every single performance breakthrough since the bicycle was further complicated with the installation of an engine has increased weight, cost, and whining from the elderly. The elderly die off and breakthroughs live on. There's potential for a lot more performance, all of which will be the result of further complication. 

Then there's another idiotic misconception: Parts = failure points. A single inadequately designed and/or fabricated part can fail in numerous modes and misapplications. Adequately designed and fabricated parts won't fail - parts count is irrelevant. 

The #5 set (See above) seeks solace in FUD and whines about the number of rod ends I use but never counts the number of roller or ball bearings used in a "Simple" conventional steering head. Aren't all of those heavily loaded tiny bearing elements also "Failure points and unnecessary complication"? FUD isn't synonymous with critical thought.

26) They're supposed to be faster and, therefore, more fun. Simpler is seldom faster. Slower isn't more fun.

27) Here's your opportunity: Build and race it yourself! Prove what a visionary you are!

Didn't think so: Opportunity is too much work and costs way too much time and money.

28) Steering the rear wheel in the opposite direction from the front makes feet-on-the-ground maneuvering easy, but it turns evil when the speed increases - it makes countersteering much less effective (Only the front half wants to cooperate) and eventually degenerates into terminal weave. All of that has come from experience. 

All of this came from ignorance, among other unfortunate causes, I suspect: 

After getting way too many stupid "But 4WS cars..." lectures from the #5 set (See above), I changed my "Cringe every time you log in." setting on YouTube:

29) No! I will not publish/share unfinished/untested project drawings. 

As long as the supply of stupid exceeds demand, this post will remain a work in progress.

5th image: Screenshot from http://npbka.com/morbidelli-project.htm