khp
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Posts posted by khp
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Welcome aboard, Ian.
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Someone recently suggested I should Google "Dave Moss" and then start reading, watching, learning... I finally did and I think it's been well worthwhile. If you're curious then try for yourself; if not, well then there's nothing to see here
Could have been me. I'm a big fan of Dave Moss.
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There are several questions in this, so let's first break them apart so it's easier to understand and answer them.
First, there's the original question: Why only use the mid-stroke?
So far, we have two possible answers: A/ the air-spring gives a progressive spring rate close to bottoming out, and B/ geometry preservation (having topped/bottomed out the fork changes the rake/trail significantly).
What I have claimed that if it's really the progressiveness of the air-spring, then we could go and create a front fork without the air-spring, ie: a fully linear front fork. One problem solved, but it may bring up other problems.
During this discussion the rear linkage is brought up. As I understand Andrew Trevitt's book "Sportsbike Suspension Tuning", the linkage is there to deliberately make the rear shock action more progressive - to avoid bottoming out the rear shock under severe conditions.
The air spring featured in the front fork may actually serve exactly the same purpose, so removing it may create more problems than it solves.
Also, if we make the front fork spring truly linear, but still need to support the same force/weight, we would need a harder spring overall - which could be detrimental to the feedback from the front tyre.
I don't have particular exclusive access to Kenth Öhlin nor his engineers, but maybe less will do.Time to go the source, I think.
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Steering dampers don't have springs in them...
That doesn't matter, my dear Bullet
Hint: how is the oil damping system and the spring of the rear shock attached to each other?
Assuming a linear spring, Is the spring constant of a rear shock linear or progressive?
Why is it different from a front fork?
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The real problem (I guess) is that the damping requires movement, since it is the forcing of the suspension oil through the valves that generates the damping. But then again, if the fork doesn't move as much (due to the higher effective spring constant), who needs damping?
OK, since no one picked on this one, I'm going to answer myself: The reason we want the suspension to move is to
i think you can see from the Ducati with rossi on, it's in it's Mid third, and he's still on the brake, turning and loading the front. This isn't be accident, clearly.
Let me be clear here: I'm not arguing about whether keeping the suspension in the mid-third stroke is good or not - I'm grinding my Axe over the arguments provided.
I think it's also impossible for the vendors to make a linear stroke fork, it is of course a sealed unit, and when you compress sealed things, it's not possible to keep the pressure inside constant, hence the stroke pressure differences.
I'm sorry, but that is not correct: you can make a linear stroke front suspension. Just think of your steering damper; it's a sealed unit, but it still provides the same damping regardless of where you are in the stroke. The trick is to isolate the oil damping system from the collapse of the fork. If you've noticed the external "cartridges" on the motoGP forks, I guess they could be doing already (or have tried it and gone back to a progressive system).
Something to consider is that the bike's geometry is affected, too - compressing or extending the forks or rear shock towards the ends of their travel can change the handling characteristics of the bike. Presumably (and this is an assumption on my part) the bike is initially set up so that the best handling DURING a corner is with the suspension in the middle, and the farther away from that you get the less compliant the bike will feel.
Hotfoot, my gut feeling is that it's the geometry argument that is the real reason - that the changes in trail and rake over the stroke is the key problem. Question is, how do we figure out if this is 'it'?
Kai
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Hi both,
My counter-argument about keeping the suspension in the mid-third is that if the suspension is so useless in the outer two thirds, why didn't the manufacturer then just make a component with the 1/3rd stroke? surely that would be much less costly, have less weight, etc etc. Surely there must be a reason for the full stroke!
But let's analyze the problem and see if we can figure out together what the physical reality is behind the "friendly advice".
Let's first agree about what's involved in a suspension unit: the spring, the suspension oil/valves, and the air volume above the oil.
1) The oil is passed through 2 (different) valves to control the speed in the two directions (ie compression and rebound damping). As the oil only provides dampening when it is forced through the valve, the actual position of the fork does not matter to the oil dampening.
2) Spring. Assuming we don't hit 'coil bind' (ie the coil is compressed so it touches itself and thereby stops being a spring), the spring will exert a force that is linear to the distance/displacement from the 'free length' and the spring constant (stiffness) - displacement velocity does not matter here.
3) Air volume above oil. Works like an extra (very) soft spring, until the volume disappears - here we get "hydraulic lock" since the shock cannot collapse anymore, and the suspension does not work anymore. For the discussion, let's assume that it doesn't happen.
The combination of the 'real' spring and the air volume gives a set of progressive stroke/Force curves like the ones in the attachment (which I blatantly stole from the Öhlins Front fork kit FGK137 Mounting Instructions, since I have such a thing on my trackbike).
For convenience, I added two lines to distinguish between the three regions and labeled them according to whether it's in the top/mid/bottom of the stroke.
For reference: the recommended oil level is 160mm, which is the line that ends around 330 N. As I recall, I used the 160mm oil level (I don't have my notebook handy so I'm not sure), while a national-level racer with the same suspension used 130 or 140mm oil level, ie a more progressive spring.
If it is correct that the advice comes from the progressiveness of the air-spring, then we can ignore the oil damping and valves.
If we look at the 3 regions, then we have about 30-50N change in the top end, 50-125N in the mid-stroke, and 100-600N change in the bottom end. OK, so why is the progressiveness of the spring a problem? - having a progressive spring help you to avoid bottoming out the fork, after all
The real problem (I guess) is that the damping requires movement, since it is the forcing of the suspension oil through the valves that generates the damping. But then again, if the fork doesn't move as much (due to the higher effective spring constant), who needs damping?
What if we could engineer a fork/suspension that had a truly linear relationship between stroke and Force? - would that change the arguments for keeping the suspension in the mid-third of the stroke?
It's past midnight, so I'll leave it here for others to laugh/comment on until I have more energy to think this through.
Kai
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ha ha, nice one. Yeah, its not as exotic as the lady, but doesn't come with the bills either no doubt.
Bullet, you do know about what they say of the Italian Ladies - they're pretty, but slightly crazy and erratic HMGs (High Maintenance Girlfriends)
Kai, wondering what Bullet's missus will say
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Here's one for Balistic and other mechanically knowledgeable persons:
When I did Level 1, our classroom seminarist (Andy Ibbot) argued that we should try to keep the suspension in the mid-third stroke.
Being an engineer, I asked him why? - Andy argued that the suspension was more compliant there there and I asked again why?, because as long as we don't hit the limits of the shock (so that the spring/dampers are still working) I cannot see a reason that the shock should be less compliant in the outer parts of the stroke, than the mid-stroke.
I could see he struggled to find an explanation that would satisfy the engineer in me after the second why, so for the sake of the overall training I let it pass. I think understand what we are trying to achieve by being in the mid-stroke, but I didn't find the explanation to be well founded.
So, can anyone explain why the suspension should work better in the mid-third stroke than the outer part of the stroke (still assuming that we don't hit mechanical stops like top/bottoming out)?
Thanks,
Kai
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Thanks for all the suggestions, I'll look into the Inns in the Palmdale area mentioned.
Carey: I'll keep you guys posted, but don't hold your breath 'cause I'm not a tweeter kinda guy (not fb).
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That Sounds like a great trip Kai. And if you get the chance to do Code RACE you'll have to let us know how it goes. I am rcurious what the student experience is in that class.
Carey,
I have locked in my place at CodeRACE, I'll undoubtedly be very sore from 4 days of riding
. Flight reservation has been done, now's the time to look for rental car and accommodation.Can anyone recommend a hotel/motel near the Willows Springs racetrack?
Cobie, Hottie: where do people usually stay?
Kai
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My 1977 KZ650 runs a homemade rectifier, the only electronics on the whole machine. Does that count
So it's a diesel?
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The local organizer asked me to forward this site, for anyone interested. This school comes under the Australian Branch of the Superbike School, they will be supplying the manpower and coaches.
www.superhdmoto.com
Is the class going to be in Chinese, Taiwanese or English ? The site is entirely in Chinese so makes me wonder. .. That many Aussie or Aussie Chinese coaches to go and teach that class ?
And did you check out the pictures down below on that site you just linked to ? Are those pictures of students/teachers of the school. . If so, you might have a lot more riders stepping up to take the class there (or at least male riders
. Wow.My best guess is that the classes with be in English, since that's what happens in countries like Denmark and Sweden where the coaches get flown in from abroad.
Guess the superhdmoto guys have a race team, and they are a bit more ...uhm, westernized ... in the gridgirl department than the boothbabes I saw at the "West Taiwan Straits Auto Expo" yesterday here in the mainlands (Xiamen).
Edit: I can't to seem to find any class dates in there. The text I found only tells about Keith and the videos. I'm not even sure they'll run a CSS school from their site!
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Just to set the record straight - I did have great race results Sunday, but I wasn't riding the BMW, I was on my Moriwaki. I sing the praises of the BMW, but for sheer fun factor (and learning how to carry unreal corner speed) its hard to beat the Moriwaki, it's big fun to race.
Speaking of random bikes on the track, there was an MZ660 pitted near me - ever see one of those? Single cylinder 660cc engine.
Congrats regardless of the bike, Hotfoot!
MZ660 - was that a Yamaha engine? They used to make the SZR660 single-cylinder sportsbike, which used the XTZ660 engine (42bhp or so...), but with USD forks and all the goodies at a time when barely any 600cc supersport bikes had USD forks. I hear it was loads of fun, even though it was never a great seller (too close in cost for 600cc IL4's and not enough ponies to attract the performance oriented young males)
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I would disagree on the 7th day assertion though. I think the most stunning bike visually is the Tamburini designed MV Agusta F4. . might not be the highest performing one, but geez is that a gorgeous bike.
My vote for the Panigale was on sound alone; as for aesthetics, your choice is hard to argue with but I have always be partial to his 916/996/998 series myself; but then I am a Ducati guy what else can I say.
I've never been a Duc guy - and certainly not a V2 guy either (I am totally underwhelmed by the 'power delivery' and so-called 'power band' compared to an IL4) - but I totally agree with Rainman on the 916 design. To me, it's the most beautiful motorcycle ever design and built.
I still don't know what Ducati did to Pierre Terblanche since he had to go and inflict the 999-and-later designs on them as retaliation....
Kai (donning the flame-proof suit)
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I could be way off, but I'm thinking that maybe the tires aren't YellowDuck's problem. It could be that he's just met the "20-degree wall".
YellowDuck, from the pictures, do not seem to keep your eyes level with the horizon, and this might trick your mind. Try turning your head so you keep your eyes horizontal - I have found that this can help many riders who struggle with getting past the 20-25 degree lean angle "wall".
Note: this is primarily a mental trick, and needs to be discarded when you have progressed so far that your lean becomes limited by the "keep your eyes horizontal" trick.
Good luck,
Kai
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How about anyone else - do you find yourself dodging a bullet with your training?
Sure have. Your story reminded me of Hollywood (aka Paul) telling a similar story of digging in his knee and gassing it at Gelleraasen in 2010 when his CBR1000RR "decided to kill me" as he said.
Dang Rain, now I have to go pop a beer for you!
Kai
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I'll be making the trek over to the Willows Springs Racetrack to do the 2-day Camp on Oct 4-5 and hopefully CodeRACE the following two days (I'm on the waiting list). It would be fun to put faces on more names than the coaches, so do come over and say hello if you're there.
I'll be the tall guy (6'6") in the (slightly scuffed) Yamaha bumblebee leathers.
I'm heading over around Oct 1st. After the school days I plan to go see/photo-shoot Grand Canyon, Antelope Canyon and possibly more before heading back around Oct 13th.
Kai
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Hey Timmer.
The more I think about it, the more I'm leaning towards a changed air funnel lift profile. Yamaha definitely added a funnel lift mechanism the '08- model and the '06-'07 models for improved midrange power.
Kai
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By using the outer leg, you get better leverage. Try standing with the right side to a wall and push with the right hand. First use your right foot to push off, and then the left foot.
Kai
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I just remembered yesterday what really makes the YEC box stand out from the PC3: midrange power. With the YEC box, the R6 will do a very controlled wheelie under hard acceleration, something I've never experienced when running with the PC3 (on the same bike) - several racers I know have noticed this too about the YEC box.
Hmm...that is interesting.
One of the things I know you can do with the YEC stuff is change the fly-by-wire throttle profile. The Power Commander can't change that. That could definitely have an effect in the mid range.
Maybe this could possibly be the change you are noticing?
Clearly, the YEC loom+ECU is a complete replacement of the ECU, so they can reprogram everything, including the throttle profile.
But after thinking about this for some time, I don't think it's the throttle profile that is changed: in both cases we're talking about WOT, but the engine is not at max torque/rpm (... well, at least as I recall it. No datalogging either. Yet).
But maybe they are have a different ignition timing profile or air funnel lift, than stock. But this is guesswork, and since the bike and I are separated by around 6000miles, I have no way of testing the hypotheses we make. Your guess is likely to be better than mine
Kai
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I have a set of Chicken Hawk Tire Warmers that are about six years old. They are for a 120/180 set and the rear will not stretch to cover a 190. Now that I use Dunlop 211 GPA's (190) I am looking to replace these. I am puzzled to find some suppliers offering a 180-195 rear which doesn't sound right. Has the technology developed to allow this kind of flexibility?
Kevin,
What I have seen from vendors is that they will sell two sizes/models: one for 250GP sized tires, and one for 600/1000cc sized tires. I think it's more the height that the width of the tires that would be problematic for the warmer size.
Kai
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Gorecki,
I have the Knox Contour Race (long) too, and had the same initial concerns as you. Turns out that it was just perfect :-)
Kai
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Glad you're liking the YEC stuff. It is definitely nice to have it all in one box.
Ya know it's tough for us....we try to modularize our products because we don't if a guy wants EVERYTHING or just enough to tune his bike for the exhaust he just bought. There are definitely pros and cons for either way.
Yeah you can't really cater to all needs and desires. Well, you could ... but it wouldn't be economically viable for Dynojet to do it.
I just remembered yesterday what really makes the YEC box stand out from the PC3: midrange power. With the YEC box, the R6 will do a very controlled wheelie under hard acceleration, something I've never experienced when running with the PC3 (on the same bike) - several racers I know have noticed this too about the YEC box.
I cannot give you hard data, since this would require two dynoruns back to back with each setup (and it takes 1-2 hours to swap the wiring loom over), something I've never bothered to do. But if you really want to know why, it should be simple enough to buy a YEC box with loom and data cable and try it at Dynojet HQ
Kai
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Hey Kai,
Glad to hear the Power Commander made your roadbike run well. No worries on running the YEC stuff...I realize that there are other products out there.
I have also heard about guys running the YEC stuff with a Power Commander. Some of the AMA racers do that. They like using the PC5 and Autotune, but also want some of the features that the YEC stuff has.
Just curious....Now that you've run the YEC stuff for a while...how do you like it? What features do you like most?
I ran the YEC stuff all 2011 (about 6 days of riding due to weather and other priorities) and can't really complain - it's just been working: injection, quickshift, etc.
On the other hand, I can't say that I'm utilizing all the features the system has. It's nice that it's a single integrated system with a pruned down wiring loom, single SW package for controlling everything, and you can use a 'simple' straing-gauge quickshifter and just plug it in (€220 instead of €420).
On the downside, I was surprised that they didn't deliver connector kits for on/off switch, QS input etc in the kit which is around €1000 (wiring loom, ECU, data cable).
On the mechanical side, one of the best things I've done is to replace the original "slipper" clutch with an aftermarket slipper from Sigma. Previously the rear tire would squirm under hard braking and slamming down through the gear - now it's dead straight (until I lift the rear...). Took maybe a couple of laps to really trust this, and off you go
. Flight reservation has been done, now's the time to look for rental car and accommodation.
2012, Where We Are, What We're Doing
in School Questions/General Discussion
Posted
Where have Cobie and the guys gone lately? I feel like I haven't heard from them in a month or so.
Has the San Andreas fault finally given in at sent them into the Pacific?
Kai (too oldschool for twitter and FB. Besides, they're blocked here in CN).