Steering damper/stabilizer

[RojoRacing]

Also, a DF has the amazing ability to catapult you over the handlebars so you can get a nice bite of the tarmac.

Jason says he stiffens his grip as he goes over bumps. Cruzbike front wheel is between two long levers - the bars and the BB. So it is immune to unscheduled steering. Do MTB people have wide bars for extra leverage? Cruzbike has lots of leverage. My Silvio has no steering effects when I hang shopping on the bars.

You choose what you want. Does Jason need slow speed handling on the way down Mt Diablo?

No you have it wrong kind of. The reason I stiffen my legs and grip over a bump is because if you don't you'll be surprised with massive unscheduled steering. We run wider bars on the mtb because it does give us a bit more leverage against unwanted steering inputs when slamming through a rock garden but also because it slows down our overall steering inputs for more stability when the rider is on board. Tiller aside wider bars on the V20 has the same effect as on the mtb which is why I don't go for narrow bars like Larry, it would make steering inputs too sensitive for descending rough mountain roads.

 

[bladderhead]

I meant that if you stiffen your arms and legs you can hold the steering in one position.

 

[dtseng]

After reading the above discussions, it dawns on me that raising the head tube angle (A) is the way to go. I am aware that changing a bike's parameter will also affect the others. Therefore, the construction of a bike, albeit so simple, involves compromise/optimization of parameters to achieve the goal. Just as Balor says: we cannot have "too much of a good thing". Let's take a look at this head tube angle thing: I would suggest using the "right-hand rule" to help us visualize what I am going to say. Let the thumb pointing along the line of the steering axis; the rest of the four fingers indicate the direction of rotation. When turning the handlebar to the left, the thumb is pointing upward; and for right turn, the thumb is pointing downward. When the head tube angle A=90 degrees, I would say this is the most ideal situation, for you turn the handlebar and you make a "pure" turn of the front wheel. When A is less than 90, the turn has two components: turn + tilt. If steering axis is horizontal, i.e. A=0, you no longer can turn, only tilt. When making a turn at low speed on a bike with slack head tube angle, the rider may need to tilt toward the outside of the curve because there is not enough centrifugal pull to justify the tilt of the bike. Therefore, I would relegate this tilting to the rider rather than build-in the steering mechanism. This indicates higher head tube angle is desirable; it also reduces front wheel flop. I will try to make a prototype with head tube angle in the range 78 - 80 degrees and trail 60 - 70 mm.

 

[Balor]

Yea, Zimin's configuration is already tested with thousands of miles (by him).
90deg steering is better, but imply negative offset that makes "leg-wheel" conflicts possible AND makes entire fork structure more prone to bending under strong impacts, unless you really beef it up (or add suspension). Looks weird too, which *I* cannot care less about, but more "conscious" people might be put off

 

[RojoRacing]

I meant that if you stiffen your arms and legs you can hold the steering in one position.

I meant the part where you claimed the "Cruzbike front wheel is between two long levers - the bars and the BB. So it is immune to unscheduled steering." It's the opposite because having your leg weight hanging between those two points and not in the same position due to them being offset with the pedals makes for rather unpredictable steering inputs from your legs being bounced. The weight is a double edged sword in this case.

 

[Black Hawk Down]

sadly you can't have your cake and eat it too, as I'm sure you're aware...

As a matter of fact, today, I had some cake and did, indeed, eat it. Tech continues to improve, new materials and ideas may lead to breakthroughs that are not anticipated. If Cruzebike comes up with a better, more stable design, I'll buy it. Until then, my V20 is the best bike I know of, even if it's a little frightening flying down a rutty, potholed American grade. Or, God forbid, I get a puncture while on said grade, yikes! I once had a front tire blowout while doing 40 mph down San Marcos pass in Santa Barbara on my DF. A sharp turn was right in front of me. I thought this is the end. But, I was able to bring it to a controlled stop while negotiating the curve. I have no such confidence of doing the same with my V20. I expect that this is how it will end for me.

 

[Leif]

I once had a front tire blowout while doing 40 mph down San Marcos pass in Santa Barbara

Love that ride. I have a pic of the painted cave section for my cell phone's screen saver.

 

[Black Hawk Down]

Love that ride. I have a pic of the painted cave section for my cell phone's screen saver.
View attachment 7571

I used to ride up Old San Marcos and Painted cave. In fact, it was a part of the UCSB double metric century. I miss those days...

 

[John Crawford]

I am also a bit concerned at the "sporty-ness" of my vendetta at high speed. It seems to get pretty frisky at about 45mph. In an attempt to improve this, I figured that I would bite the bullet and fit up a Cane Creek viscoset headset. It was a bit of a challenge as it is not compatible with the headset used in the Vendetta, but with a little help from my lathe, I was able to whip up an adapter and make it work.

So, results... drum roll please... I found that it's effects were quite noticeable at low speeds. It seemed to improve my low speed wobbles some, but really had no noticeable effect on the high speed stability. The inbly way to describe the feel is to compare it to running a much fatter tire at lower pressure. I usually run 28mm tires at about 90 psi. The viscoset headset made them feel much like my 32mm softies at 60psi.

 

[Andrew Wilson]

Good write up John. Thanks for taking the effort to test and report.

 

[Balor]

Well, at high speeds requirement for control over the bars goes up dramatically, and reliable way of increasing control at high speeds is more trail - Patterson recommends no less than 10 cm for MBB for instance. Combined with a damper, it should improve high speed stability (while damper deals with increased flop) - and barring modification to front triangle to decrease wheel offset that would require experimenting with rear wheel diameter.

Minimising steering inertia (which is real cause of feeling of twichiness at high speed - because you lack total control over the bars, and it is very easy to 'overshoot' the steering and go down) is an ultimate solution, but on a Cruzbike (especially if you are a larger person) this is rather limited, because seat is fixed, and you cannot move the boom in to decrease steering axis-BB distance without impacting your seat to pedal distance, and this distance increase steering inertia by a square of radius basically.

Of course, you may eventually learn to 'leg steer', effectively removing leg mass (largest contributor to inertia) out of equation, as well as develop further techniques of dealing with inertia, but extent of this adaptation is vary from person to person.

 

[Balor]

I am also a bit concerned at the "sporty-ness" of my vendetta at high speed. It seems to get pretty frisky at about 45mph. In an attempt to improve this, I figured that I would bite the bullet and fit up a Cane Creek viscoset headset. It was a bit of a challenge as it is not compatible with the headset used in the Vendetta, but with a little help from my lathe, I was able to whip up an adapter and make it work.

So, results... drum roll please... I found that it's effects were quite noticeable at low speeds. It seemed to improve my low speed wobbles some, but really had no noticeable effect on the high speed stability. The inbly way to describe the feel is to compare it to running a much fatter tire at lower pressure. I usually run 28mm tires at about 90 psi. The viscoset headset made them feel much like my 32mm softies at 60psi.

Btw, did you experiment with damping strength? What you describe does not sound like much at all.

 

[John Crawford]

Btw, did you experiment with damping strength? What you describe does not sound like much at all.

Yes, I tried several different damping settings. Controlled by how tightly you compress the stacked discs. As suggested by others, it did improve the low speed flop response, but had little to no effect on the high speed stability.

I've put several thousand miles on my vendetta with this Viscoset. My standard training ride has a couple of long fast descents so I have a fair number of repeatable tests with just about any configuration you can think of. I've tried various tires, wheels, pressures, and hand positions all to no avail. I don't really see myself as needing to go over 50mph on my bike, but it would be nice to know I could!

 

[benphyr]

...I don't really see myself as needing to go over 50mph on my bike, but it would be nice to know I could!

Hi @John Crawford,
Are you actually getting a speed wobble or does it a feeling of less stable, less controllable, or is it that inputs are twitchy? My read of the Cane Creek website is that it is trying to absorb oscillations so that you don't get a harmonic oscillation that multiplies and gets out of control. And that it is not designed to absorb large inputs that you give as a shock absorber would. That is, a speed wobble is when you have a wiggle that goes 1.1mm*1.1mm*1.1*1.1*1.1 etc. 60 times and now you have a wobble that is 304mm=12inches and you lose control and flip over the handlebars or off the bike. The viscoset is designed to dull the additive effect so that you might get input of 1.1*1.1... but that is smoothed down to 1.0 or 0.9 which next oscillation is then 1.0 or 0.81 so that they don't add up to greater oscillations.

I'm probably not understanding the concept quite right but that is what I got out of it.

If you are not getting a speed wobble then the viscoset may be a good thing and something that you want just not addressing the particular problem you were hoping it would help with. My read between the lines is that you want something that is better at high speed stability - predictability, self-righting, confidence building, lessening the affect of pedal steer. That is when you get way out of my depth of bicycle mechanics but certainly my touring bike is much easier to ride no hands than my Qx100. But as I ride more and more, the Q becomes much stabler at any speed because my legs seem to be getting much more accustomed and provide much less surprises (=pedal steer / (over) reaction surprises). Not sure if that is just long term adjustment that is required on the platform or if there is better setup that can address these things though comparison between models and model years may tell a story.

Anyway, I am getting far afield of the topic. Your testing and report is definitely appreciated. I didn't even know such a thing exists before you posted! Thank you.

 

[John Crawford]

Hi @John Crawford,
Are you actually getting a speed wobble or does it a feeling of less stable, less controllable, or is it that inputs are twitchy? My read of the Cane Creek website is that it is trying to absorb oscillations so that you don't get a harmonic oscillation that multiplies and gets out of control. And that it is not designed to absorb large inputs that you give as a shock absorber would. That is, a speed wobble is when you have a wiggle that goes 1.1mm*1.1mm*1.1*1.1*1.1 etc. 60 times and now you have a wobble that is 304mm=12inches and you lose control and flip over the handlebars or off the bike. The viscoset is designed to dull the additive effect so that you might get input of 1.1*1.1... but that is smoothed down to 1.0 or 0.9 which next oscillation is then 1.0 or 0.81 so that they don't add up to greater oscillations.

I'm probably not understanding the concept quite right but that is what I got out of it.

If you are not getting a speed wobble then the viscoset may be a good thing and something that you want just not addressing the particular problem you were hoping it would help with. My read between the lines is that you want something that is better at high speed stability - predictability, self-righting, confidence building, lessening the affect of pedal steer. That is when you get way out of my depth of bicycle mechanics but certainly my touring bike is much easier to ride no hands than my Qx100. But as I ride more and more, the Q becomes much stabler at any speed because my legs seem to be getting much more accustomed and provide much less surprises (=pedal steer / (over) reaction surprises). Not sure if that is just long term adjustment that is required on the platform or if there is better setup that can address these things though comparison between models and model years may tell a story.

Anyway, I am getting far afield of the topic. Your testing and report is definitely appreciated. I didn't even know such a thing exists before you posted! Thank you.

I'm familiar with speed wobbles from my motorcycle days. What I'm experiencing is not a resonant sort of wobble but rather a high speed instability where a slight bump or crosswind will bounce me across the road and cause me to ruin a perfectly good pair of underwear. I seems like the front wheel gets lighter and twitchier as the speed increases. I'm not discounting the possibility that it's some sort of rider input causing this (perhaps it's me that gets twitchy lol) , but I've ridden my DF bike as well as my other recumbent to much higher speeds without encountering this sort of issue.

I do agree that while the steering damper did not necessarily solve my high speed issues, I do like the smoothing effects at lower speeds and plan to continue using it.

I'd also like to point out that I'm certainly not trying to be critical of my Vendetta, it is by far my favorite bike to ride.

 

[RojoRacing]

I'm familiar with speed wobbles from my motorcycle days. What I'm experiencing is not a resonant sort of wobble but rather a high speed instability where a slight bump or crosswind will bounce me across the road and cause me to ruin a perfectly good pair of underwear. I seems like the front wheel gets lighter and twitchier as the speed increases. I'm not discounting the possibility that it's some sort of rider input causing this (perhaps it's me that gets twitchy lol) , but I've ridden my DF bike as well as my other recumbent to much higher speeds without encountering this sort of issue.

I do agree that while the steering damper did not necessarily solve my high speed issues, I do like the smoothing effects at lower speeds and plan to continue using it.

You are right that it is 100% rider input but unfortunatly it's involuntary rider input. The faster you go the more minor the needed steering inputs become to move across a lane of road but an unexpected bump in the road is going to toss the weight of your legs twice as hard at those speeds to the unwanted steering input is 4 or even 6 times as effective at messing with your stability. I'd say it's pretty safe to say no one descends as fast as I do on a bent so I'm most experienced with what you're talking about and even more so at even greater speeds. The bike isn't unstable, but the design of the bike adds a stability liability in how the rider affects it with steering inputs. It's like I tell people, it's like driving a Formula one car, the performance is there but at race speeds if you ham fist the controls you'll end up in a wall real fast. It's a machine that given the right rider has the ability to exceed other machines but only if that rider has exceptional skill.

 

[Balor]

What I'm experiencing is not a resonant sort of wobble but rather a high speed instability where a slight bump or crosswind will bounce me across the road and cause me to ruin a perfectly good pair of underwear. I seems like the front wheel gets lighter and twitchier as the speed increases.

It does not get lighter, obviously - it is trail self-centering force failing to keep up with increased speed and providing you with enough control over the bars (like Jason said) given steering inertia of your particular Cruzbike configuration (longer legged riders get more) and your level of ability.

DF bikes (especially MTBs) are much more stable at speed because they have lots of trail, very low steering inertia AND you don't have to rely on steering alone to keep balance - you can use body English.
Heavier motobikes also don't accept too much body english, but they have tons of trail and tire grip - which translates into much more trail forces that help you control the bike at high speeds. Trail force, however, is based on tire friction and hence deducted from your speed (increases rolling resistance, which is pretty abysmal on motos). No idea how much quantitatively, though... likely not *much*.

All in all, it comes to your own strength and dexterity - VERY few bicycle designs are 'truly' unrideable, even RWS with negative trail. It just takes superhuman dexterity to ride one .
Still, 'conventional' MBB design does exclude a non-negligible part of populace if my own experience and feedback I've seen is of any indication. My first MBB (65 deg steering, 40mm trail, about 40cm steering axis-bb distance) was 'dangerously frisky' (leading to a few near pant-soiling experiences and a few outrights falls) even at 40 mph, but eliminating flop by 90 deg steering angle, increasing trail and reducing boom length allowed me hit 45 mph descents while pedalling furiously (160 RPM) and feeling totally in control.

Again, since you've already dealt with low-speed flop by a damper, why not experiment by increasing trail by installing, say, a 26" wheel with a narrow tire in the rear? On the plus side, it will make you a bit more aero as well . Gripper, lower pressure front tire will help too (it was suggested many times in other threads as well). It will not help *much*, but might be just enough (especially combined with a damper) for you to feel in control.

It's like I tell people, it's like driving a Formula one car, the performance is there but at race speeds if you ham fist the controls you'll end up in a wall real fast.

Admittedly, steering inertia is a 100% liability that does not contribute ANYTHING useful to performance and should be minimised by any means possible.
Other means of adding control at high speed - dampers, more trail, more wheelbase - indeed have downsides when it comes to performance, but reducing inertia is 100% beneficial.

 

[bladderhead]

I have a Silvio, which may be a bit easier than a V. I am a mid-footer, so my effective x-seam is short. I cut the boom. I have a single chainwheel so my BB is lighter than usual. So I have decreased the steering inertia a bit. But I do not experience any wobbles or twitchiness. From 0mph to 45mph. What Balor says sounds right. With the BB waving about on the end of a long pole it is like the tail wagging the dog. But I do not notice any effect. It seems more stable at high speed than the Grasshopper. I think this is because of leg-steer. I think that a better term for it would be hip-steer. And at low speed I can lean forward and give it some body-English.

And when you steer you do not change the angle very fast anyway.

Balor mentions tyre-grip. There is only one way to test that. That is what worries me, especially after my "two bangs" experience.

 

[Balor]

And when you steer you do not change the angle very fast anyway.

That's not how it actually is. Any steering correction involve two cycles, countersteering and only then steering. It happens pretty fast - so fast, in fact, that most people don't just never notice this, but will actively deny doing it at all! Yet, you cannot manage a singletrack vehicle without countersteering, because you have to start any turn with a lean INTO the turn, otherwise you'll instantly tip OUT of the turn and crash - and barring 'body english' you can only do this by countersteering.
It is managed by autonomous systems, and when they detect insufficient control over the bars - they trigger panic response as described in messages above (I fully agree with description, I had exactly same experience, if at slower speeds because my first MBB was inferior to Cruzbike in design)

MAYBE, it is a question of hyperactive 'panic response' and not really lack of control. Yet, given how many times I've actually crashed my first MBB (many times) and how many times I've crashed my lastest MBB (once - run out of grip on rear tire on wet asphalt) - you ignore your subconscious system (that do most of balancing for you!) at your own peril.

And since those mechanisms are subconscious, if they fail to 'get' dealing with steering inertia, there is nothing *you* can do, except riding more and hoping that they eventually will. (After about 5k miles, I thought enough is enough and build my own MBB).

Or, maybe, you can - find a Flevobike or a Python, that simply cannot be ridden without leg-steering, and try to at least learn to ride one. That might 'kickstart' some of your systems to learn leg steering patterns - provided it is indeed 'leg steer' that 'makes or breaks' MBBs with significant steering axis to BB distance.
Pythons, though, will NEVER be stable at speed due to considerable negative trail, and I think Flevobikes are no longer sold.

 

[bladderhead]

You are right, I do not notice myself countersteering. But I still do not understand why, if steering inertia is such a problem, it is not a problem for me. I wish I could try a Balor-type bike, just to feel the difference.