Landracing Forum
Tech Information => Technical Discussion => Topic started by: isiahstites on February 14, 2008, 11:18:53 PM
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I am getting ready to stretch, lower and rake the neck on my bike and was curious as to your thoughts on trail. I have not take all of the measurments yet, however from the info I do know I am thinking my trail number is going to be high. I know the number should be around 4-6 inches and was curious what kind of handling quality can I expect if it is above 6? I have done plenty of research over the years while building bikes on the subject, but do not have first hand experience in changing the steering neck.
Scott
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i run 52 degrees of rake about 14 inches of pos. trail i dont think thats for everyone and i know this will start an arguement but rake and trail are your friend at high speed --all the rules that apply to cars have nothing to do with bikes because when you turn your wheels to the left on a car you will turn left --when you turn the front wheel left on a bike you will turn to the right yes thats right RIGHT --depending on the tube and stem offset i would run 34 to 38 degrees of rake --i would run the smallest lightest front wheel and tire i could find and i would run no rear suspension make sure that the front and rear wheel line up vertically and you should be good to go and remember that steering must be limited to 15 degrees right and 15 degrees left 30 degrees total with very sturdy steering stops and a good steering damper (dampener) willie buchta
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:-D but if you don't turn your bars back to the right pretty quick you're gonna be on your ass...Eventually your bike is gonna go where your front wheel is pointing... Ya mean counter steer. :? From what I've seen in one year, which is not a lot I agree. But, what I have always considered optimum frame set up, ie dirt track or MX, is completely different here.
So Scott, get it where you like it, make it straight and blow the hood off... Mines 39 deg. and if I remember right about 4" trail and runs straight as an arrow. But I only have half the motor you do. :-D
Larry....... Yours to speed
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i.........................(dampener) willie buchta
Willie a little off topic, but just curious as to why you don't log in under your user name, but under Sheri's?? Maybe a desire to be 50 again :evil: :?
c ya,
Sum
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Sum....don't ask Willie......ask "Landracing Jon"
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sum sheri is on the computer most of the time but if it makes a differance i will log in --did you get your aluminum and how is the body coming havnt heard willie buchta
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hay i still remember my password willie buchta
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hay i still remember my password willie buchta
That's better, now I can sleep nights 8-).
Yep got the aluminum with 3 of the 4 corners bent under. I just today filed a damage claim against UPS Freight. They called when it got to New Mexico and told me 2 corners were bent under and from there to here the driver managed to bend one more under.
I haven't started on the body yet, but maybe in a few weeks. I want to finish up some other stuff first. I'm welding up an aluminum fuel tank now. Aren't TIG's the greatest??
c ya and you can still sneak in here under Sheri's name if you really want to :lol:,
Sum
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with that much rake and trail what will happen is the bike will go straight ....really straight.....so if you get blown slightly off course and are heading straight for a mile marker....your bike wont turn.... when you start counter steering the bike will start leaning in at the top but it wont turn.....so after you blow through the mile marker go back to the shop and pull it back....scott, there is no holy grail... you are racing a bike on slippery surface...dont kill your bike with silly numbers....do exactly as randy tells you to do....
kent
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Ummmm Scott or Kent......
For those of us keeping score at home, what did / does Randy tell you to do about the rake and trail?
Thanks
Mark
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that is pretty common --tell them a horror story to keep them from doing the right thing --heard them all my life dont pay any attention im speaking from 46 years of motorcycle riding experience --ive ridden and built just about everything on 2 wheels some 3 wheeled stuff also and at 63 i still ride last year riding 41620 miles we have all had this discussion before to no agreement --and will probibly have it again --my best advise is actually talk to 4 people who ride and pick something in the middle that way you will be in a safe zone im probibly on the top of the scale at 50 something degrees if i were running a 2 wheel bike i would probibly keep the rake about 34 to 38 degrees just some thoughts and what works for some dont work for others --if you want to see a horror story google RON COOK look close and you will see a bike with to little rake although thats not the only problem willie buchta
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250+mph Hayabusa's are running 28 degrees rake and 90mm of trail.
Willie,
At what rake does the front wheel want to flop?
Is there a point where too much rake causes the bike to be unstable?
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Check out the rake and trail on Denis Mannings
Lucky-7 liner (with Telly-forks)................stable at
350+ mph
Those numbers, are the ones I would choose!!!!!!
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Wheeler runs 28 in his liner I ran 26..whan I ran 35 it wouldn’t steer…. Now on a sit up bike you can run lots of rake cuz you can compensate by leaning off the bike to make it turn….in a liner you don’t have the ability of body english to use… that’s why I know for a fact that anything more than 35 is useless…There have been tons of studies and papers done like the "Roland and Sharp" study on front fork oscillation done in the 60's... Willie I understand you have been riding for 46 years but you really need to get off your soap box on frame geometry before someone gets hurt from your unfounded advise… Harley Davidson has been building bikes for over 100 years and they don’t put 50 deg on anything... theirs absolutely no reason to use anymore than 38...over that a telescopic fork ceases to function properly due to weird angles…willie have someone use about 6 ratchet tie down straps and get yourself strapped down tight on your bike so you cant move anything but your arms and then try to ride your bike…you’ll be singing a different tune real fast
kent
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But it's so easy:
(http://upload.wikimedia.org/math/a/c/5/ac5d019ff17ad50dcde47aa5c1462a43.png)
Where Rw wheel radius, Ah is the head angle measured clock-wise from the horizontal and Of is the fork offset or rake.
Yeah, that's it!
(http://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/Chopper_with_long_rake.JPG/180px-Chopper_with_long_rake.JPG)
Jason has the right numbers. Numbers in that region allow good stability at speed and still miss the mile markers.
I'm with Kent that 52/14 gives you the straight line stability but won't turn if you really need it.
Oh, and for the challenged: 90mm = 3.54 in. = 0.0000559234073013601 mi.
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Kent is pretty close for a kid, a fast learner about learning how and why things go fast. :wink:
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kent i never advised anyone to use 50 degrees of rake i just said i do --there you go with the horror storys again now it involves death --i wish that you would at least come up with facts because if im in danger i would like for you to show me not just make up another horror story --prove what you say i dont think you can --we all have our own opinion and i think thats all it is im from missouri show me i dont think you can willie buchta
i said 34 to 38 degrees on a ridgid frame go back and read the post
as far as flop goes we are limited to 15 degrees of steering from straight ahead no flop at 52.2 degrees of rake (measured it today)
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Evry now and then there's a poster on this website that's kind of a "burr under the saddle" to the rest of us!
If yer ridin' bare back the pain is more personal !
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just say the word anyone and i wont post here again thanks willie buchta
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Evry now and then there's a poster on this website that's kind of a "burr under the saddle" to the rest of us!
If yer ridin' bare back the pain is more personal !
Yea at one time or another about everyone has offended someone or everyone,
Advise to all,
IT'S A FORUM...
Keep Posting Your Opinions and what is working for you.
IT'S A FORUM.
Keep Posting your opposing view to what someone else says works for them
IT'S A FORUM.
At times gang mentality may rule, but a forum is where we can talk openly. If you think it works, say so, if you think it won't, you can say that too... IT'S A FORUM.
:|
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Oh, come on now people.......lets agree to disagree.......I don't claim to be a expert on M/C
chassis.........I have only been at it for over 55 years, and still learning. Back in the 1970's
Harley Davidson liked our roadrace chassis and so did Honda and "Fast Freddy" had high praise
for our stuff. This kind of input has certainly
helped me in my way of thinking of what works.
One person, who in my opinion. really knew what made M/C frames work, was the late Ray Hensley
of "Trackmaster" fame. I had the pleasure in working and consulting with the "master" for many years. Building frames for "dirt track"
and making them work well is a special art.........
and Ray knew the "art"..........Right Ack..............
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Oh, come on now people.......lets agree to disagree.......I don't claim to be a expert on M/C
chassis.........I have only been at it for over 55 years, and still learning. Back in the 1970's
Harley Davidson liked our roadrace chassis and so did Honda and "Fast Freddy" had high praise
for our stuff. This kind of input has certainly
helped me in my way of thinking of what works.
One person, who in my opinion. really knew what made M/C frames work, was the late Ray Hensley
of "Trackmaster" fame. I had the pleasure in working and consulting with the "master" for many years. Building frames for "dirt track"
and making them work well is a special art.........
and Ray knew the "art"..........Right Ack..............
So in your 55 years of experience what is your view on this rake and trail topic?
Scott
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Ummmm Scott or Kent......
For those of us keeping score at home, what did / does Randy tell you to do about the rake and trail?
Thanks
Mark
Randy likes the number 35 for rake and has told me I could go as far as 40 but that he would not go any further. He runs some of the drag bikes at 40. He has been pretty busy at the shop and I have "tried" to leave him alone. Monday I will ask him about the trail portion because I am at that point before I move any further I need to know what it is going to be at the different rake angles.
I will post any thing worth mentioning Monday evening , if this thread is still going.
Scott
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If you are interested in all things motorcycle chassis then IMHO one of the leading experts in this field is a bloke by the name of Tony Foale , lay your hands on is books, read and start to be educated ,I was :-), he has academic training (phd in mech& elec engineering) has been a lifelong racer/rider ,and has designed and fabricated some exceptional motorcycles ,he also conducted some remarkable practical experiments on 'rake & trail'
cheers
Gary
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Straight line solo bike.....no less than 28degrees
.....no more than 32degrees......3.50inches of trail
Or better yet....leave it alone......
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see what i mean everyone has a different openion me included --i have a hard time putting my thoughts on paper there is probibly some fancy name for it --but let me say this as long as we just get on this site and voice our openions loudly and argue none of us are going to learn anything and i thought that was what this site was all about --i think we are all in the same boat er lake everyone on this site knows something that could save someone else a lot of work--someone told me a long time ago that all of the knowlege of mankind was written on a piece of paper somewhere true maybe but i dont read so good so sometimes i rely on this site for an answer to my question so far it and everyone has been a great help but please dont try to scare me with horror stories it didnt work when i was a kid and it wont work now --i have built a lot of contraptions in my life i always ride what i build before any one else does --i wouldnt build anyone anything that i thought they would get hurt on because of me no matter how much money was offered and i wouldnt give anyone advice on anything unless i had some experince on the subject--this is the most ive ever typed i think ill take a nap willie buchta
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couldnt sleep look guys i really need some help here there is a lot of things that i know nothing about one is aerodynamics (or spelling) im getting ready to build a new bike for bonneville 08 of course a sidecar does anyone familiar with the sidecar rules have any suggestions thanks willie buchta
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For the singular purpose of going really fast on a natural surface, Kent explained it the best and Tony explains it the most.
Lack of directional stability due to tire spin, frame flex, inconsistent surface, and wind forces, require a little different consideration than anything you might experience any other place.
Many modern street bikes are actually pretty good and represent a lot of development on the part of the OEM that must consider a lot more than one might imagine. :wink:
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Oh, come on now people.......lets agree to disagree.......I don't claim to be a expert on M/C
chassis.........I have only been at it for over 55 years, and still learning. Back in the 1970's
Harley Davidson liked our roadrace chassis and so did Honda and "Fast Freddy" had high praise
for our stuff. This kind of input has certainly
helped me in my way of thinking of what works.
One person, who in my opinion. really knew what made M/C frames work, was the late Ray Hensley
of "Trackmaster" fame. I had the pleasure in working and consulting with the "master" for many years. Building frames for "dirt track"
and making them work well is a special art.........
and Ray knew the "art"..........Right Ack..............
Straight line solo bike.....no less than 28degrees
.....no more than 32degrees......3.50inches of trail
Or better yet....leave it alone......
For the singular purpose of going really fast on a natural surface, Kent explained it the best and Tony explains it the most.
Lack of directional stability due to tire spin, frame flex, inconsistent surface, and wind forces, require a little different consideration than anything you might experience any other place.
Many modern street bikes are actually pretty good and represent a lot of development on the part of the OEM that must consider a lot more than one might imagine. :wink:
Listen to your elders.
Besides any one old enough to know Ray and is not being fed purred peas and remains somewhat coherent deserves some respect.
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Thanks Ack, (I think) you have a gift with words.
As Jack noted, a lot of time and money is spend by the manufacture on developing their new
chassis and frames. And many are not developed in house........they are sub-contracted
to so called outside "experts". The new BMW and also the Harley V-Rod come to mind. Some
"heavy" thinking has gone into the new Rotax
powered Buell chassis......again with some outside
help. Thus my point "better yet leave it alone"
We have some very fast "busa's" running with
stock rake and trail and they appear to be fairly
stable.
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Much of the early work regarding increased rake angle (with trail following as consequence) was simply an attempt to cure wandering and head-shaking at speed due to lack of stiffness at the steering head. It was a crutch, and when they finally figured out how much 3-dimensional area was needed to insure sufficient rigidity, the rake requirement went down.
Testing an early (and many current) drag bike by inserting a bar through the steering head, and another through the swing-arm pivot would show that the bars can be rotated by far less effort than your nerves can stand.
Foale (paraphrasing) views trail as more important, but the large numbers frequently seen are not necessary if, again, the frame works. Not an accident that 200 mph road racers do quite well with 24° & 3".
Regarding "flop": in order to reduce flop to zero (viz., where the front wheel will not "fall over" to either side under vertical load) the rake angle must be zero. With any caster angle at all, the axle at 0° steering angle is elevated above its vertical position at any other angle. The axle climbs when the wheel is centered.
The relevant question is, IMHO, "how much angle produces sufficient axle drop (at a steering angle that will be in use) that stability is compromised?". I don't know the answer, and this is more complex that it may appear since large diameter wheels are less affected.
More comments: http://victorylibrary.com/brit/chassis.htm
I have a related question: omitting the effect on frontal area and streamlining in general, I'm puzzled about the effect of CG height in a bike.
A low CG is normally considered a good thing for most purposes, but in terms of degrees of camber needed to transfer weight for steering correction isn't a high CG an advantage here? A bike with a CG at ground level would need to incline to horizontal to make any corrections.
It seems to me that the less disturbance to the camber angle the more stable the bike will be?
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Thus my point "better yet leave it alone" We have some very fast "busa's" running with
stock rake and trail and they appear to be fairly stable.
I think we will find most of the fast fast Busas are running an extra 5 degrees. I wish I was smart enough to know what was best... :| But as I read all this stuff, I am following links and learning, and that is what if fun here. Glad we have a lot of old farts to learn from... :-D :roll:
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"For every bit of straight you want in a bike, you have to remove a bit of nimble, build it like that and make sure it stays that way." (me)
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Thanks for all of the info to this point! This is what I was looking for to better educate me on the subject and along with my own research it has done just that, so thank you.
A lot of people have stated to leave it alone because of the R&D done by the big name companys. My thoughts are that have done a lot of R&D, however is it not mainly for the use of street applications? Most LSR bikes never see the pavement and will never see the twisties where good handling would be of the utmost importance.
I decided to change mine for several reasons, I wanted to decrease frontal area, more stability due to the chassis being a few inches longer and to allow me to be more comfortable on th bike instead of balled up when in the riding position.
Here are a few pics of the old neck, downtubes and backbone and what will be the new. I have not figured the number yet but I left the backbone long until I decide hom much stretch I want.
Scott
Old
(http://i142.photobucket.com/albums/r98/isiahstites/Buell%20re-build/100_2180.jpg)
New
(http://i142.photobucket.com/albums/r98/isiahstites/Buell%20re-build/100_2204.jpg)
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Thanks to everyones help on this. I finished up the backbone and neck today and came out with 38 degrees of rake with 7.5" of positive trail.
Scott
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what made you decide on that willie buchta
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what made you decide on that willie buchta
Based on the info I have found during my research and the different trail lengths above 38 degrees were not where I wanted to be. I talked it over with Randy and we agreed that what I came up with would work well.
I could of went with less rake and it would of been fine, however I did not want to purchase or modify my forks, by kicking it out a few degrees it will allow me to use the exisitng front end.
Scott
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good choice willie buchta
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Here is a site that has control and stability papers:
http://www3.imperial.ac.uk/controlandpower/research/portfoliopartnership/projects/motorcycles/publications
The guys that wrote them do work for Ducati on their factory road racing bikes, and are motorcycle riders themselves including a Suzuki GSX 1000. They said that the papers are oriented toward academic types so they are not the easiest for non-techs to understand or wade through. One paper is on steering dampers, where the rest are on handling. Handling is complex - there is no easy solution except to get it rigid to start with, then work from there. For example, steering dampers can cause wobbles in some circumstances, and excess trail is bad. Study and have experts give you advice. Too bad I don't know much or I'd help.
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It looks like a lot of those papers were authored by Sharp...the guy I mentioned earlier… he’s is world renowned and has been at it for a long time...not as well known as Fole but more analytical… he mostly does analysis study of design in accident cases...Willie that means he was hired to analyze the cause of an accident… the after fact of poor design…. no horror stories, just the scientific answer of what killed the rider...Any one who is involved in accident reconstruction like Randy Nelson, Rus Odaily, Jon Mckibben, even Scott Guthrie have read at least one Sharp report….good reading...dry, but good info… I wish whom ever authorized the new rule that limits our steering lock to 15deg had read some of sharps papers, he would have realized that limiting steering lock would not prevent or reduce tank slappers... I voted no….Sharp also wrote a nice paper about chassis oscillations and steering dampers...maybe someone should do a compilation of his work into a book...
Kent
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"he would have realized that limiting steering lock would not prevent or reduce tank slappers"
Please, please tell me that was not offered as the reason...?
If anything, bouncing off a stop at full velocity may make it worse, with none of the self-centering that trail might add.
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As is the case with many of the LSR rules, they reflect a lack of understanding on the part of the authors, and allowable participation by a number of people that know better . :-(
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panic...oh yes.... you should have heard my eyes roll at the meeting.... passed anyhow...
kent
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The Wizzzzard srikes again. :?
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eric ross and i were informed about the rules committee meeting about the time it started --we were also told that we could go but had to be quiet-which we did--maybe its just me but every meeting i have attended seems like everyone is in a big hurry to get out of there except the drivers meeting and that one seems like it lasts forever just some thoughts and i think a lot of you are confusing road racing with land speed racing when it comes to the set ups on your bikes willie buchta
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you should have heard my eyes roll at the meeting
Is eye rolling all that is allowed, or is there another reason for this meeting?
Todd
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In days past when a MC common interest meeting was open to all at Bonneville on a well publicized evening, it was very well attended and productive.
It featured participation from every back ground, type of entry, and experience level.
Sadly, those days are out the door, as will be the whole of the MC program at Speedweek if it continues along the path it has been reduced to. :x
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So who's brilliant idea was it and were you the only no vote Kent?
YA GOTTA WONDER....
Jack, maybe the object of the exercise is to eliminate the bikes...
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When push comes to shove, guess who is most likely to fall off the end of the earth. :-(
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oh,oh,oh,...i know the answer to that one...me.!..... :roll:
stainless i wasnt the only no.!...
willie, that last meeting actually went pretty smooth...their usually filled with a lot of petty bitching, complaints, and rule chage proposals that have self serving adjendas...a lot of waisted time for volinteers and racers who would rather be working on their own stuff....i think it went smoothly cuz we stuck to only items that were presented for discussion before the meeting... and when the item went to the floor for discussion the sg of arms (me) had the unfortunate job of smacking down drunkin ramblers (Noonan :-D ) so we wound up with a pretty efficient meeting... if we used this format to the old speedweek and Sept elmo meetings we could probably tweek the book so most of everyone would be happy...
what i would really like to do is to get Mr Dolan back involved....but he is too busy playing behind the key board shit stirer...really Jack you have a tremendous anount of knowledge and history that is important to us.... remember you were the guy i came to when i rewrote the PS rule and you told me the over head thing originaly came about when Flanders busted Tom Evans fairing on his harley...that information was critical when i needed to know how, why and when the rule originated so i could understand the intent and then cane up with a clear definition...jack you really need to come out and play with us again...
love ya
kent
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Sorry, still not getting it.
"they reflect a lack of understanding on the part of the authors"
Without completely dispensing with modesty, I'm fairly smart. I have some experience with chassis design, built some primitive engines, have a narrow history of motorcycle racing, some basic physics, civil law.
Until I began visiting here, I would never have presumed to impose an opinion - my presumption being that the rules were the result of much painstaking work by people better than myself.
Some of what I've read here matches the Mississippi State legislature "deciding" that Pi = 4.
I'll just sum this up, and then stop.
What qualifies them to make this stuff up?
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A review of my activities with respect to LSR, indicates to me that I am not a "Shrinking Violet", nor am I hiding anonymously " behind a keyboard".
My intent is to share, provoke some thought, and then measure the reaction.
From that might grow some thoughts from others, but when you stick to the facts, it doesn't generate much argument.
When the whole thing is reduced to politricks, I am most unkind. :wink:
NOTE: I think Panic gets it.