KX Riders
General => In General... => Topic started by: mg82 on February 25, 2008, 11:51:27 AM
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got these extensions made from a fella who runs 4 cylinder nitro hillclimbers.
just straight line drag racing on the ice. my chains tension held it together. thank god it chain was tight or else it could of got messy.
(http://i268.photobucket.com/albums/jj12/mgolemb/DSC00187.jpg)
(http://i268.photobucket.com/albums/jj12/mgolemb/DSC00186.jpg)
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i think the box said " 80 horse and under " :|
the way i look at it ..... i got through about 6 gallons of vp so we must be pushing the envelope... :-D
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Looks like the wrong alloy to me! :x
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the old saying weakest link in the chian could be applied here,,,,wow ,,1 k5 thats right eqauls nitro 4 cylinder 4 poke$$$$$$$$$
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I'm sure the aluminum started out 6061-t6 but after welding it would be something far less then that. Judgeing by the home made look of the extensions they were not reheat treated after welding not to mention you are asking a lot of that little bar of billet. Thank god you were not hurt.
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ya i would say i am lucky.
that would not feel good to have that ice tire rip off the back at 90mph
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you might be getting twice the traction with your ice setup over the hillclimber so your putting alot more stress on it than the hillclimber. show us a pic of the other side when you get it off. maybe he undercut the weld and started the crack. BDI's right they didnt heat treat the 6061 after welding it. It has to be heat treated twice. first heated to 900+ then quenched to put it back to T-0 then second baked at 400 to get it to T-6.
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That's called "the notch effect".
Perpendicular bracing would most likely eliminate it. You'll need to address the whole pice otherwise it will break here, just past the weld. The weld acts like a gusset.
(http://i114.photobucket.com/albums/n248/Jeekinz/Misc%20Bike/swingarm.jpg)
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ya thats exactly where it broke. right along the edge of the weld. i'll get a pic of it when i get home this weekend. i just emailed the guy we'll see if he responds.
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you must be living right . the mojo good with you . could have been worse . could have broke and a honda could have won . lol. a friend of mine is an engineer and has a program you type in the metal , shape and the streesssss it will take . it shows you where it will bend and or brake at what force's. also it will show you where to add or take away . handy thing to know ahead of time .
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Look up Thomas Racing Service. I think its thomasracingservice.net or .something. He is making swingarms for multi-cylinder nitro-burning bikes for National Pro's, Amatuers and some International Customers. I personally use him for everything from plating cylinders to powder coating. He Hillclimbs everywhere, builds bikes for many competitors, and still has reasonable pricing with quick turn arounds. You don't have to take my word for it,like I am trying to sell you something. Check out his page. He can make swingarms no problem.
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FEA software can't calc welding. and don't bet your life on the results. its good at telling you how it bends and breaks but the loads are almost never right.
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just talked to the the guy who made them. super nice guy that is really apologetic. says that these were a prototype that he tried for the first time. he's machining me a new set on him. this time there will be no welds. all out of one piece.
i'll still look into thomas racing service tho.
thanks for all the input
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There's a book, I call it my Bible, called Welding Secrets that explains how common welding failures can happen. For instance on your swingarm, say you V'ed out the crack and welded it back together, the piece will crack again just past the new weld because the weld is still the "notch". You also have the points where the two pieces overlap eachother, those a re notches too. The "notch effect" can happen on pieces that arent welded too. That's why you'll want to incorporate gusssets to help spread out the stresses. It happens all the time on various things. Say you have a bolt stuck and it breaks, where does it break? Flush with the surface it was threaded into.
Gussets, and welds and joints that aren't perpendicular to the ends of the piece can eliminate fractures. You'll see some examples on your swingarm and frame. If that was one solid piece of the same design, it will still break at those two points.
Good Luck.
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I think part of the issue is the bolt up design, the bolt doesn't hold the material solid enough and will flex. If it was me I'd get a swingarm off Ebay, cut off the existing chain adjustment area, and machine the extensions to slide into the swingarm about 4-6" then you could bolt it or weld it and they'd be solid. I've built numerous sets this way with no problems, one set is on a ZX-10 bike, no issues what so ever. I was pressed for time and had a set built (KX 250), the first trip out they tore up a new sprocket and my extensions, home they went and were modified, no more problems, I still don't like them, so I bought a swingarm and am going to make another permanent set up
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I think part of the issue is the bolt up design, the bolt doesn't hold the material solid enough and will flex. If it was me I'd get a swingarm off Ebay, cut off the existing chain adjustment area, and machine the extensions to slide into the swingarm about 4-6" then you could bolt it or weld it and they'd be solid.
That's the only way I would do it other then building a whole new swing arm from scratch and having it heat treated. The fact of the matter is you are asking a piece of aluminum that is sized right to be an adjustment block to do twice the work of a normal length swingarm spare.I don't need a fancy computer program to tell me thats a bad idea, common sense will do just fine.
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Yeah, I agree BDI. The Cr's let you slip extensions into the swing arm because it is hollow at the end. The strongest way to make them for Kaws is a complete swing arm made from chromoly. I think you all would be shocked how inexpensive a custom set would be. It may be a little more than welding some off-set aluminum blocks together, but you will only have to buy chromoly swingarm once.
Js, I doubt very seriously that an Ice dragger is putting more stress on a swingarm than a 4 cylinder nitro-methane burning hillclimber injected with nitrous on a pro hill with several jumps. I can't imagine a flat surface being more stressful than that.
The thing about extensions that you need to keep in mind, that I think is being overlooked here is, a good set of stretchers are very adjustable. Depending on conditions, gearing and tread pattern, you will want to be able to make length adjustments for more or less hook-up. Usually guys have a slick set-up, dry set-up, jump set-up or drag race set-up. These may require different sprockets, length of swingarm, rear wheel and of course that all means length of chain. A good set of stretchers makes these changes quick and easy and you won't be stuck with just one set-up.
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i have seen tons of people run similar setups to this one without any issues for years. this is what i want now, only with two separate bolt holes. shorter for sand/dirt, longer for the ice.
(http://www.plasticpartsinc.com/admin/images/prodimg-463.jpg)
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Find an 89 swingarm off ebay, they are just like the Honda, the inserts will slide out and you can slide your extensions in, end of problem.
I would not use a set that relied on the existing adjuster pocket to hold the swingarm, I've seen lots of them as well, but that doesn't make them good, just easy, people tend to go easy.
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there are pictures of what the setup looked like on my bike herehttp://www.kxriders.com/forums/index.php/topic,4098.0.html (http://www.kxriders.com/forums/index.php/topic,4098.0.html)
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roll the snail cam against the allen head to adjust your chain
(http://www.kxriders.com/Users/michaelgolembiewski/Pictures/iPhoto Library/Modified/2004/Jan 1, 2004/100_0904.JPG)