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Hammer71
| | Posted on Tuesday, March 06, 2007 - 05:44 pm: | 
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Fritz, when we doin that TPS reset? |
Saintly
| | Posted on Thursday, March 08, 2007 - 08:03 pm: |
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Tonight I decided to get a definitive answer as to the fender clearance issue.
I toyed with a few ideas on how to go about it, but finally decided that the only way was to stroke the fork tube to the full extent of its travel while the fender was mounted to it.
I removed and disassembled the entire right fork leg assembly and then re-assembled it without the fork spring.
I re-installed the leg and mounted the fender to it. With the spring omitted, I was able to push up on the tube/fender assembly and simulate a FULL compression condition.
To my dismay, the fender touched the damper long before it was out of travel!
I decided to see how much clearance I needed, so I removed the damper from the bike and re-tested by pushing the tube up.
I could not believe that the fender now touched the 3/8" hex extension of my isolator bolt before the tube had fully compressed!
Next, I removed the isolator bolt. The third test revealed something even more shocking! The fender will strike the lower triple tree BEFORE the forks reach the fully compressed position!
There is approximately 1/2" of travel remaining before the forks "bottom out" at the point where the fender strikes the tree. See pics below:
Fully extended:
Fender hitting tree before fully compressed:
Remaining compression travel at point of interference:
So what gives?
Do I need to go back to the drawing board?
Is the isolator mount method completely flawed?
Do XB's simply not strike their own fender because nobody has weighed enough or hit a big enough dip in the road to ever reach full compression?
Help. |
Old_man
| | Posted on Thursday, March 08, 2007 - 10:23 pm: |
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Perhaps, with the spring installed the forks will not compress to this extent.
The fully compressed spring may prevent complete travel.
I weigh around 250 lbs. with gear.
The front spring preload is set for a soft setting.
I lowered the forks in my standard suspension XB9S 3/8 inch.
I see no evidence that the front fender has ever contacted the damper connection.
In any case I would recommend lowering the forks when installing this type damper. |
Tattoodnscrewd
| | Posted on Thursday, March 08, 2007 - 11:21 pm: |
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There should be no reason the forks should bottom out .. if they do while assembled, your suspension may need to be looked at. While you do want as much travel as possible - you don't really want to get within 1/4" of bottoming out while riding at your absolute hardest. (As explained to me by Dan Bilansky)
So I don't know if I'd go with the test done without springs. Maybe with the springs out - set the fork tubes within 1/4" to 3/8" of bottoming and see where that puts you. It will be a bit more telling in a real world situation.
(Message edited by tattoodnscrewd on March 08, 2007) |
Gentleman_jon
| | Posted on Friday, March 09, 2007 - 06:29 am: |
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Fritz, we all certainly do admire your dedication, that's for sure.
Am I right, my brothers?
Now that we have both had a chance to sleep on it, I shoouldn't be at all surprised if you came to the conclusion that removing the springs was likely inappropriate, methodology wise.
Perhaps it would be a good idea to re-install the springs,
set up the suspension normally, and then put some zip ties around the front fork legs with the suspension extended, ie: totally unloaded.
Then go for a bit of a canter, with the goal of compressing the suspension as fully as possible without doing oneself a mischief.
Shall we say a hard landing off a wheelie, but not TOO hard a landing if you see what I mean.
Returning to the barn, the zip ties will indicate the extent of maximum compression. I shouldn't be surprised if it were rather less than the amount shown in your latest photographs.
Then I might jack up the bike, and with the strap you normally use to compress the forks whilst removing the spring, restore the forks to their max compression point as indicated by aforementioned zip tie, with the springs installed, and see what clearance issues remain.
Kindly report back.
I do hope you slept well.
(Message edited by gentleman_jon on March 09, 2007) |
Mikexlr650
| | Posted on Friday, March 09, 2007 - 07:52 am: |
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i use the zip tie method to track travel used. the spring does limit travel, the ties never reach the outer tube (yes i am sure i have bottomed the front end).
fritz, look up the travel listed for the front end and measure from the bottom up. should provide a reasonably accurate stop point for the bottom slider. |
Bake
| | Posted on Friday, March 09, 2007 - 09:05 am: |
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Fritz, we all certainly do admire your dedication, that's for sure.
Am I right, my brothers?
Ya, I have been reading intently! |
Bomber
| | Posted on Friday, March 09, 2007 - 09:22 am: |
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concur -- without springs, your forks will compress a great deal more than with -- I've also used the zip tie method of measuring suspension movement, and, while I HAVE bottomed the forks, they never approached the degree of compression they could without springs installed.
I'm thinkin your scoot will be fine, and exhibit no parts interference with your forks assembled with springs |
Saintly
| | Posted on Friday, March 09, 2007 - 12:36 pm: |
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the ties never reach the outer tube (yes i am sure i have bottomed the front end).
Mike (or anyone for that matter), how far did the tie end up?
Anybody got a measurement or a photo? |
New12r
| | Posted on Friday, March 09, 2007 - 02:26 pm: |
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My zip ties are about an inch off the bottom after a track day or wheelie/stoppie etc.. |
Saintly
| | Posted on Saturday, March 10, 2007 - 12:18 am: |
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Ok, I believe you guys may be correct when you state that the test without springs is not accurate.
I thought about it and I convinced myself that there must be some other limiting factor in the fork compression travel. The conclusion that I drew, was that when the springs are in place, they must "coil bind" prior to the tube traveling all the way up and into the leg. This must govern the travel limit and thus prevent any "interference".
So, I then decided that I needed to know exactly how long the springs were at the point where they coil bind and cease all compression travel. If I knew how long they were at "bind", then I could determine the exact point where the forks truly bottom out. I started by measuring the "free length" of my fork spring. It was exactly 14.25" in length.
Now, the stock XB fork spring is a "uniformly wound" spring rather than a "progressively wound" spring. This makes my job easier, as I can estimate "coil bind" length by subtracting the space occupied by the "gaps" between the coils. I measured five or six of these gaps, and found that they all were the same width. That width was .255" which I rounded off to 1/4" for simplicity.
There were a total of thirty gaps between thirty-one coils. 30 X 1/4" = 7.5" When I subtract 7.5" from my free length of 14.25 I get 6.75"
This should be the length of the spring at coil bind. (ie. when the spring can compress no more, it will be 6.75 inches long)
I decided to test my estimation by actually compressing the spring until it reached "bind" and then measuring it. Out in the shop, I put the spring in my press and fabricated a "safety scatter shield" from two pieces of PVC tube. The tubes were both 6.25 inches in length and I slit one lengthwise to get it to fit inside of the other one "telescopically" If my theory held, the PVC would telescopically collapse into one another and still allow 1/2" inch of spring to be exposed so that I could visually confirm "coil bind".
I pumped the ram until it would go no more. This was a little scary, as the thought of that spring shooting out to the side under all that pressure was constantly on my mind. For you kids watching this: Don't try this at home! I am a trained professional and have years of experience of doing stupid shit! Anyway, a quick look at the exposed spring confirmed that it was indeed coil bound.
When I got out the tape measure, I could not believe my eyes. 6.75 inches exactly!! Damn I'm good huh?
I released the spring from the press, and promptly fashioned a 6.75" piece of PVC to use in place of the spring. This should accurately show me the travel of the fork tube when the spring is COMPLETELY
compressed.
I re-asembled the fork leg with the PVC, and proceeded to collapse it.
.
.
.
.
.
It still travels all the way up!
.
.
.
.
.
. I have no choice but to conclude that given enough downward force, an XB WILL collapse it's fork enough to strike its own fender on the lower triple OR whatever gets in its way first!
In my case, the "whatever" will be my isolator mounted damper.
It is now my firm belief that the isolator mount method is flawed and dangerous. If the damper ever struck the fender it could at the very least cause an unsafe slick coating of the front tire like Tx05xb12s experienced, or worse it could cause the tire to momentarily stop/skid causing a wipe-out.
I will be re-designing my damper to mount elsewhere. To those of you currently running an isolator mounted damper assembly: Good luck and be careful!
Fritz
(Message edited by saintly on March 10, 2007) |
Gentleman_jon
| | Posted on Saturday, March 10, 2007 - 01:36 am: |
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OUTSTANDING post!
Simply one of the best of all time!!!
Am I right, my brothers?
I simply can not recall a more thorough, and yet, more entirely amusing post on Bad Web, can you?
A great service to the community and an example to all of us who, if not pushing the envelope as Saintly does, occasionally might give it a slight shove.
I hope all will join me in offering Fritz a hearty:
WELL DONE, FRITZ !!
PS - That being said, I still remain to be conviced that there just possibly might not be some methodological malfunction here, as I would be somewhat surprised if anyone has ever had their front fender hit their lower triple.
Has anyone experienced this?
(Message edited by gentleman_jon on March 10, 2007) |
Tattoodnscrewd
| | Posted on Saturday, March 10, 2007 - 06:06 am: |
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I have to throw this comment in again ... but first - yes, Saintly, very good post .. however, and I am going to go on the guy's word who told me this (Dan Bilansky - I think he'd have some experience here) ... if you/anyone are bottoming the forks, you need to look at the suspension.
Based on rider size/weight and the aggressiveness at which you ride .. you may need one of 2 things if you are bottoming the forks - new springs( read - different spring rate), or a bit more fork oil (not heavier) because your forks should have full range of motion without bottoming even under the hardest conditions .. because of that- I would say you should have no worry of the fender getting that close to the bottom tree.
Saintly, are you german ? (fine if you are -as I am) but German's are known for over-engineering things .. might be borderline to being at that point...  |
Saintly
| | Posted on Saturday, March 10, 2007 - 07:02 am: |
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I'm not currently, nor have I ever(to my knowledge) having an issue with my fender striking the tree. I'm just saying that it could happen.
Knowing now as I do, that the XB forks will continue to compress past the point where where fender clearance exists, I cannot and will not risk putting anything into the path of possible travel.
Yeah it may never occur on my bike, but what if it does? If I put one upward facing nail in my driveway, I may never run over it, but when I do I'm going to be screwed.
Looking at the big picture, I certainly cant condone the isolator mount method now. What if someone else read this post and saw that I did it this way, so they do it also. Then if their forks had weak springs, or they weighed a lot more than me, or they came down hard from a wheelie, or .........
It's possible and so it's cause for concern. I said earlier in this post that I was going to thoroughly test my design before just hap-hazzardly throwing it on the bike and riding.
Fear not, in a few days I'll have "Homemade (cheap) XB steering damper part II" with a completely different and safe mounting system.
p.S. Yeah, I'm 50% German. |
Tdiddy
| | Posted on Saturday, March 10, 2007 - 07:14 am: |
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What if you reassembled your fork and compress it with some straps? |
Saintly
| | Posted on Saturday, March 10, 2007 - 07:39 am: |
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What if you reassembled your fork and compress it with some straps?
Like this?
(fully assembled w/springs, It will go a bit more but my ratchet straps are making weird "tearing fabric" sounds and I'm getting nervous) |
Mikexlr650
| | Posted on Saturday, March 10, 2007 - 07:51 am: |
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fritz, is it possible the fluid (oil) affects overall travel(i'm obviously assuming these forks are sans oil)? |
Glitch
| | Posted on Saturday, March 10, 2007 - 08:51 am: |
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I'm thinking that if you bottom the forks (with suspension set up proper) so far as to hit whatever comes first, you're in trouble regardless. |
Glitch
| | Posted on Saturday, March 10, 2007 - 08:51 am: |
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Excellent post by the way.
I'll be moving it to the KV after activity stops. |
Mikexlr650
| | Posted on Saturday, March 10, 2007 - 09:45 am: |
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is it possible that the amount of force required to compress the fork to spring-bind would exceed the maximum speed at which the fluid can travel through the oriface in the damper rod? in otherwords hydraulic lockup occurs first. in addition the amount of time an impact lasts is very short. cool post fritz!
thinking of my dirt bikes, i can often get tire rub marks on the bottom of my fenders after landing large jumps. of course this situation would be low speed/long duration force compared to street riding which would generally see high speed /short duration force. of course street can produce long duration force during hard front braking. here we are limited by traction first then the strength of the front wheel/tire assembly. again maybe the force required to create the situation would exceed some parameter where the forks are not the weakest link. again, cool post fritz. fun stuff to think about, kinda like reading kevin cameron in cycle world.
hmmmm??? |
Trac95ker
| | Posted on Saturday, March 10, 2007 - 06:33 pm: |
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I can remember a time when I was riding with the H.V. guys and someone stood it straight up, almost flipped it and came down real hard. Mike, do you remember seeing the sparks coming off his muffler? If the fender hit the triple tree, the muffler would be flat as a pancake. Can't wait for more antics at MB4  |
Etennuly
| | Posted on Saturday, March 10, 2007 - 07:04 pm: |
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How could it be that it would rub when it was so completely tested by the two guys that set the world record stoppie on an XB with one of them hanging off the front end?
Sorry I don't know how to bring the link in. |
Mikexlr650
| | Posted on Saturday, March 10, 2007 - 08:00 pm: |
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i think it was fritz who landed that hard, and yes i remember the sparks. can the rubber mounted motor have moved down from the impact enough to cause the contact? i know on my dyna it's possible for the motor to hit the ground quite hard in a g-out. hard enough to grind the fins off the bottom of it, ouch! |
Mikexlr650
| | Posted on Saturday, March 10, 2007 - 08:02 pm: |
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this is why dyna's shouldn't chase buells! nasty scars they are indeed. |
Hammer71
| | Posted on Sunday, March 11, 2007 - 09:01 am: |
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I think I remember that one LOL. I also remember a Black Bolt jumping a set of Railroad tracks (Mike) and not compressing that much. Go figure. |
Mikexlr650
| | Posted on Sunday, March 11, 2007 - 09:09 am: |
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i was testing the future buell dirt bike theory, or sumthin like that!
but youre right, if the forks didn't compress to spring-bind landing from a jump then something is definetly stopping them short of fritz's finding's??? |
Sokota
| | Posted on Monday, March 12, 2007 - 12:16 pm: |
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The things that make you go hmmm..... out to the shed , front wheel off the ground , if all of the claimed 4.72" travel of 05 CityX is consumed , for sure isolater bolt will impact fender. Isolater bolt approx. 4.52" from fender on a parallel plane. I am using up 4.18" on a regular basis. |
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