TRX250R.ORG
Workshop => Suspension and Chassis => Topic started by: troybilt on March 03, 2014, 08:12:30 AM
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Can someone measure your frame. Need the vertical and horizontal distances from the pivot to the upper shock mount and lower linkage mount on the frame. I don't have a torn down frame. I scanned the 450r swingarm I can lay this out and see what we we have. Calculate leverage ratios, shock lengths, etc..
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/0405_swingarm_zps7996a154.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/0405_swingarm_zps7996a154.jpg.html)
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Someone get this man what he's asking for!
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I can get you this when I get home. I'm sure someone has an 86-87 bare frame available.
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Measurements up to center of holes from flat and level surface the frame is sitting on:
swing arm pivot hole 4"
link hole 1 7/16"
shock hole 12 11/16"
Measurements back from center of swing arm pivot hole to hole centers:
link hole 1 3/8"
shock hole 1 7/8"
Accuracy within a 32nd of inch a 16th for sure.
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A 88 frame fyi.
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Is that a 04/5 swingarm troy?
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Awesome RK88R that's exactly what I need! I'll update this tonight with a little more info and some calculations...
Sam, yes 04-05, 18.5" long roughly center to center. (I assume that's 04/05 as my 08 is ~19")
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Awesome RK88R that's exactly what I need! I'll update this tonight with a little more info and some calculations...
Sam, yes 04-05, 18.5" long roughly center to center. (I assume that's 04/05 as my 08 is ~19")
Yes, that's a correct assumption Troy. Look forward to further developments. It would just amaze the crap out of me if we were able to come up with a long travel setup using this 450r swinger. Being that the 450rs can add a special linkage to make theirs that way, I don't see why that would be too crazy of a thought.
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i have this set up on my 87. i used all 06 componets. with the 87 stock front lonkage with the 06 450 linkage reversed it sits in perfect. with the stock 87 shock. for a long travel changing the linkage using an 05 rear linkage with an 89 front linkage should make the bike sit lower offering a longer shock option. in theory.
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Can someone get me the stock 450r dog bone length and the link length? I have a link but not sure which year it is, I think 08.
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Nevermind got the measurements... thanks!
OK, here is stock 250r frame with stock 04-05 swingarm with stock 04-05 dogbone and linkage:
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm_zpsefe9cec7.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm_zpsefe9cec7.jpg.html)
On the graph, from left to right bottom axis is full droop to full compression of the shock and the Y axis is the leverage ratio, leverage ratio is a curve not a single number, its the change in wheel travel divided by the change in shock length. I've been setting preload length at half of the travel, good or bad, its just a starting point for now. The orange curve represents stock 08 450r geometry, however, I wasn't 100% sure what parts I had at the time, so take that with a grain of salt for now.
I set the frame at 1" off the ground for full compression, and 13" off the ground for full droop. You'll see right around the 9.5" mark of shock compression the linkage nearly goes over center that is why there is issue with the curve, i.e. bad.
Dashed blue line represents the shock, the red lines represent the swingarm, dogbone, and linkage. This is at the 10" of compression you'll see the dogbone and link are nearly in a straight line so that is causing out problems.
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm-overcenter_zps12ff17ef.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm-overcenter_zps12ff17ef.jpg.html)
So lets try a few things to correct it.
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One thing I should point out, this is not what stock travel is, I'm setting it up for the ideal situation for MX.
Also I blew up a portion of the spreadsheet to look at shock lengths, etc... Also the max hang down of the linkage if that is negative means at bottoming out or full compression the linkage hangs below the bottom of the frame, also not good.
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm-overcenter2_zps1840074c.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05linkageandswingarm-overcenter2_zps1840074c.jpg.html)
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Here is the stock 250r frame, 04 dogbone, 04 swingarm, 08 link: Looking a little better more like a stock 450r with a little longer shock.
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05dogbone08link04swingarm_zpsbc7c4459.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05dogbone08link04swingarm_zpsbc7c4459.jpg.html)
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Moving in the right direction: (please note this doesn't take into account hitting the silencer or airbox...)
Little less progression, and a 17" long shock.
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05dogboneRElink0104swingarm_zps2f66cb35.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05dogboneRElink0104swingarm_zps2f66cb35.jpg.html)
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/250rwith04-05dogboneRElink0104swingarm2_zpsb1015fd1.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/250rwith04-05dogboneRElink0104swingarm2_zpsb1015fd1.jpg.html)
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This is starting to look better. I hope Andy @ Maul Tech is taking notice of this. If we could get roughly 10.5 to 11 inches of wheel travel out of this, that would be awesome. Troy, I'm sure there will be some limitations to what you will be able to safely run this set up on. I'm sure there will be others interested as well, but I know for us mx guys, the longer the shock travel the better. We need every 1/2" that can be spared. Once we get the progression optimized, maybe Andy can create a link that will accommodate this progression.
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I can make a link not a problem, I have full CNC machine shop at my disposal. The biggest issue you will have to have a shock setup for this link, which can be big $$. I don't see many, (1 or 2 guys) that will spend the money for a shock correctly setup for a long travel linkage.
Maybe Andy can help us with the shock setup and its limitations.
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I can make a link not a problem, I have full CNC machine shop at my disposal. The biggest issue you will have to have a shock setup for this link, which can be big $$. I don't see many, (1 or 2 guys) that will spend the money for a shock correctly setup for a long travel linkage.
Maybe Andy can help us with the shock setup and its limitations.
Very true, Troy. I honestly didn't mean that you couldn't make the link. I know better than that. I was hoping more so that maybe Andy could chime in about the best way to make a shock for this. Remember, even a no link and cr500 link shocks were new and unheard of once.
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The key to making this work, for the majority, is designing a link that the factory rear shock can be used.
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The key to making this work, for the majority, is designing a link that the factory rear shock can be used.
Honda already designed that linkage, LOL!.. I hear ya.
Also the CR500 and no link took months of shock development to get it right, also big $$.
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the factory 250R rear shock. I know there are no freebies and maybe this is a pipe dream.
What if a bracket was made to move the mounting point on the swingarm forward to the same measurement as the 250R?
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Any further developments?
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Not sure where to take it from here to be honest, when I start building another bike I'll do some testing on my own. I don't expect anyone to go out and drop a grand on a new shock built for my linkage for testing and I don't see the point in designing one for the stock length shock either.
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Andy, how difficult would it be to take an aftermarket shock set up for a standard link and set it up to be 17" long instead of say, 16" long?
Troy, you said that this 17" length shock could be obtained by using the 250r standard link front with an 08 TRX 450r link correct?
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I would have to work with Andy cause he would need the full compressed length and the full extended length, plus the progression ratio curves, force curves etc..
But what I calculated was with a stock 250r frame, stock 04 450r swingarm, 08 dog bone, and a new link that I designed. This is for a total length shock of 17", I can go higher but you lose progression.
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troy, how would the numbers work out if you move the mounting point on the stock 04/05 swing arm forward, I think 1" and used all 86 250R shock, linkage and dogbone measurements? If my guess is correct then it shoudl be the exact same progression rate as stock 86.
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my attempt to use a 450 swinger was met with many as saying it wont work and the geomitry is all wrong you are wasting your time. and this information was coming from some reputible and respected builders and suspension guys. as it appers on paper it would not work. i bought an 06 swinger and tried different linkage set ups till i had this. when i used an 06 swing a 87 front linkage and a 06 rear linkage i had to put the rear 06 linkage in buy spinning it a 180. it droped my ride height by 1/2 inch. this was all bench tested. i assembled this on my bike. i posted my findings with photo's of the articulation of the componets. this is posted on .com. another member who has been ridding r's tried this set up and left feed back that it performed flawlessly. to many members who buy and sell and have these componets. if someone can assemble this set up as a mock up and try swapping out the linkage parts it would be an easyier option. there were many who said the 450 front shocks made the bike sit higher and it would not work on paper. but it does work with + 2 +1 a arms and revalve the shocks. so to get the long travel set up to work on paper may prove to be difficult. try old school bolt it up and try it out. if i had a long travel shock then i would try diffrent linkage parts till it worked. note to assemble the linkage parts some mods are required as they don't just bolt right up. will need spacers and such.
Thank you
Douglas
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Sorry everyone, I've been super busy in the shop lately and haven't checked this site. You are more than welcome to send me a PM and let me know anytime you need my input and I should get the PM in my e-mail which I check once a day at least.
The way they used to figure out a setup with a new linkage design or new bike was to buy a bike or take one on loan and start playing with it. These days it's way easier. I can get you at least 90% there with simple math. We've done the testing for the valving for each spring rate so I just need you to throw a known spring rate on your shock with the linkage you want to run and give me a sag measurement. As for correcting shock lengths its also fairly easy on an aftermarket shock.
Troy, I would try to design a linkage that has the lowest starting leverage ratio possible in order to run the lightest spring rate which will give you the longest shaft travel. It will be more like the YFZ or CR500. Sometimes you will run into situations where the shock travel is too long and there's no way to get the compressed shock length short enough due to hitting the shaft up inside the body of the shock! If you get the progression where you want it you should be able to use whatever shock lengths you want by moving 1 of the holes into a different location! So I would start with a known shock (maybe a stock YFZ if the reservoir will clear)
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Can someone measure your frame. Need the vertical and horizontal distances from the pivot to the upper shock mount and lower linkage mount on the frame. I don't have a torn down frame. I scanned the 450r swingarm I can lay this out and see what we we have. Calculate leverage ratios, shock lengths, etc..
(http://i1345.photobucket.com/albums/p669/robl-engineering/250R-450r%20Swingarm%20Layout/0405_swingarm_zps7996a154.jpg) (http://s1345.photobucket.com/user/robl-engineering/media/250R-450r%20Swingarm%20Layout/0405_swingarm_zps7996a154.jpg.html)
I do know that the linkage mounting point to the frame for the 86 is different than the 87. If you would like, I have an 86 frame, bare, and can take the measurements you want. Maybe the 86, being different, is the one.....
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Not sure where to take it from here to be honest, when I start building another bike I'll do some testing on my own. I don't expect anyone to go out and drop a grand on a new shock built for my linkage for testing and I don't see the point in designing one for the stock length shock either.
All it would need is a longer shaft to make it longer but have the same compressed length.