On Thursday 15 January 2009, Tom wrote: >Gene Heskett <gene.hesk...@...> writes: > >snip... > >> But since I'm an old biker myself, I would never install a part like that >> on my bike, I have first hand seen the results of a broken one. At about >> 45mph. At first we thought he would be in a wheelchair the rest of his >> life, but he never made it from the bed to the wheelchair. That part >> needs more mass, lots more. > >Thanks for your concern Gene. I can see you are advocating for the good > here, so I am inclined to listen carefully. > >I would like to offer a few more facts about the part: > >My customer's trike is a tried an proven design that has undergone iterative >improvements for decades. Here is the website: >http://www.lightningmotorcycles.com/specs2.html > >You can see a shot of the original tripleT here: >http://www.lightningmotorcycles.com/specs2.html
Both links point at the same page. :) >This design is my remake of the original which consisted of a .75" thick > flat plate 7075 without lightening pockets. The original design withstood a > 35 mph head-on collision without cracking, even though the forks were bent > back about 45 degrees. I know the guy who endured the crackup and he is > just fine, and drives his "replacement" whenever he can. That 7075 (T?, 6 hopefully), solid, is probably ok, although I'd prefer to see it like I see it in the whole trike pix but out of 1" stock, and maybe even 7078T6, which is harder on tools but otherwise machines nice, or has for me when I can get my hands on it. It isn't something I can access on demand at the scrap yard here in West (By God) Virginia. The last big block they had I think was 6061 at best, pretty gummy stuff. I've been working on that 40 pound block off and on for several years now with my teeny tools. >Now, I will grant you that shallow clamping area of the original design may > have tolerated greater flex without causing metal fatigue in the part - and > therefore the newer design may experience internal stresses that were never > seen by the old design. In fact, I think this will be the case. I agree, it cannot help but be worse if the fork tubes flex. But I'm not sure I would condemn the thickness of this one just for that reason alone. Besides, they aren't supposed to flex, too easy to get a tank slapper when they do. Kawasaki's turned more than one good man into flag draped coffins with their small fork tubes and lighter triple clamps. I had one once, and another clamp sitting on top of the fender helped, but that KZ-750 still wanted to shake its head when leaned over smartly & carving a slice of corner for my enjoyment. Between that, and it coming home in a pickup most of the time, costing me $200+ for the trannies countershaft and sprocket each time, plus the long tear-down to replace them, caused me to change the name on the title, so I put the next 50k miles on a Suzi, a GS-1000-G. :) >So what would it take to make you willing to put such a part on your bike. > Would you be willing to forgo the lightening pockets altogether? Well, as I went and got old (now 74) when I was having fun, I sold my last bike pushing a decade back when I realized my reflexes just weren't up to the steel shoe & teflon kneecap pads crowd anymore. So, going back to <http://www.foxpointdesign.com/cnc_stuff/ttclamp2-sm.jpg> I think I'd ask to forgo the lightening cavities entirely. I assume those bolts are grade 12's, but with the lightening cavities gone, you would have room and mass left to screw them into heli-coils, which would bring the thread strength up to what the bolts can deliver when the proverbial 1/8 turn from broke torque is applied. A hardened steel washer under the bolt head would both make the torque easier to get, and help prevent the hole from collapsing onto the bolt should the bolts have to make several trips in and out during assembly. That would be similar to lubing the bolt (which I would anyway and reduce the torque accordingly if for no other reason that to have the hole full of grease to slow the corrosion,) and I'd reduce the terminal torque some percentage to keep it from going past the 'broke' part of that old saying when the steel washer is slicker than the ALU under the bolt head. :) Those are obviously very nice trikes, and this machining is impeccably done except for the mark per loop through that piece of code that made the cavities, but I have a one legged friend I don't dare forward that link to. He keeps himself somewhat beyond broke the way it is, and he would just have to buy it (gotta have one better than the Jones's up the street you know) and you might have to come and get it when he defaults. You would I think, enjoy the trip if you "stop and smell the roses", but certainly not the cost of it. One now old farts opinion, based on 40+ years of riding, at as much as 37k miles a year. Rain, snow (18 inches of fresh powder one night when the fm transmitter went down) or shine. It ran as a chair car for me a whole lot cheaper than a 35 foot Pace Arrow could for several years. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) those damn racoons! ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
