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#11
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![]() gerblefranklin;1169169 wrote: pedrotejada, Titanium is NOT rigid. It has a significantly lower modulous of elasticity than steel Sorry I read that around here! I must find the post, but If I'm not right, someone posted that the titanium weld is also harder cause the material is harder and if the weld is weak it will not absorve much impact as aluminium does. I must find it... Anyway both, Ti and stell are rigind materials aren't? About ti welding theres a site that teach many ways to make Ti bike frames. I think I have it bookmarked and can try to find. The proposed some realy interesting welds for low surface situations that I tought maybe would fit a flat frame. Until now I'm only designing the seatpost ![]() it ![]() Sorry about my error! that makes things clear! -- pedrotejada '*Kris Holm Unicycles*' (http://www.krisholm.com) '*Unicycle.com.br*' (http://www.unicycle.com.br/) *Brazilian Unicycling Team* ------------------------------------------------------------------------ pedrotejada's Profile: http://www.unicyclist.com/profile/14471 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
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#12
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![]() you´re talking a lot about titan - in deed what´s with the steal ![]() in my oppinion the steal of the hub (not the axle!) is not very high quality. therefor its not so difficult to build a titan hub in higher strength / lower weight. jogi PS: my TI KH - hub is about 210 gr les than my old KH Hub -- jogi municycling anarchist 26" K1 Track Monster Surly Conandrum KH36 Nightrider 24 K1 street zitat smilymarco: Es ist Knut, der kann das. Knut ist ein Tier! ------------------------------------------------------------------------ jogi's Profile: http://www.unicyclist.com/profile/14910 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#13
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![]() It's a common misconception that Titanium is "stronger" than steel, but as mentioned above it depends on how it is measured. Ti has a stronger strength to weight ratio than steel but a lower strength to volume ratio. It is also 60% heavier (by volume) than aluminum and has elastic properties that work well in bike frames but are not advantageous for a uni frame. It's also a lot more expensive, obviously. The lesson is that no material is perfect but some are better than others for certain applications, and the challenge is to use the best material for the right location. On a uni, my opinion is that Ti offers only marginal advantage for a frame because the flex issue requires Ti tubing with sufficient rigidity that it is only marginally lighter at huge expense. In the case of the hub, we are of course replacing CrMo so there is significant weight savings. Since the volume of an ISIS axle is constrained by geometry, a Ti axle is slightly weaker than a CrMo axle. But while flange strength has been an issue, broken ISIS axles on a uni hub are incredibly rare so functionally they can be considered similar. Consequently the weight savings makes Ti, in my opinion, a very good material for the hub. The elastic properties of Ti make it good for the flanges and the Ti flanges are also thicker than the CrMo flanges. So far there has been only one broken Ti flange that I know of, and it appears to have been faulty welding subject to warranty. So in summary the Ti Moment hub is functionally similar in strength to the CrMo hub but significantly lighter. Kris -- danger_uni ------------------------------------------------------------------------ danger_uni's Profile: http://www.unicyclist.com/profile/21 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#14
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![]() danger_uni;1169299 wrote: It's a common misconception that Titanium is "stronger" than steel, but as mentioned above it depends on how it is measured. Ti has a stronger strength to weight ratio than steel but a lower strength to volume ratio. It is also 60% heavier (by volume) than aluminum and has elastic properties that work well in bike frames but are not advantageous for a uni frame. It's also a lot more expensive, obviously. The lesson is that no material is perfect but some are better than others for certain applications, and the challenge is to use the best material for the right location. On a uni, my opinion is that Ti offers only marginal advantage for a frame because the flex issue requires Ti tubing with sufficient rigidity that it is only marginally lighter at huge expense. In the case of the hub, we are of course replacing CrMo so there is significant weight savings. Since the volume of an ISIS axle is constrained by geometry, a Ti axle is slightly weaker than a CrMo axle. But while flange strength has been an issue, broken ISIS axles on a uni hub are incredibly rare so functionally they can be considered similar. Consequently the weight savings makes Ti, in my opinion, a very good material for the hub. The elastic properties of Ti make it good for the flanges and the Ti flanges are also thicker than the CrMo flanges. So far there has been only one broken Ti flange that I know of, and it appears to have been faulty welding subject to warranty. So in summary the Ti Moment hub is functionally similar in strength to the CrMo hub but significantly lighter. Kris There are a couple of other advantages you of Ti you haven't pointed out: -It's expensive ![]() slightly better at getting you from A to B. You buy it because not every Tom, Joe and Mary has one. -It looks cool -No need to paint it (saves more weight and scratches) As for the hub, why aren't there any aluminium hubs? Most good bike hubs I know are aluminium, and they're pretty strong and light. -- GizmoDuck The Induni Unicycle Tour 2009. Unicycle Tour of India. Email me for details. www.induni.adventureunicyclist.com The Uninam Tour 2008.....Hanoi to Saigon!!! www.uninam.net The SINZ Unicycle Tour 2007....South Island, New Zealand www.sinzuni.org ------------------------------------------------------------------------ GizmoDuck's Profile: http://www.unicyclist.com/profile/794 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#15
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![]() GizmoDuck;1169301 wrote: As for the hub, why aren't there any aluminium hubs? Most good bike hubs I know are aluminium, and they're pretty strong and light. You cant compare bike to unis here. Bikes do not come close to the amount of torque and stress which is required from a unicycle hub. -- agentQ --- 'Uneed Films' (http://www.uneedfilms.com) ------------------------------------------------------------------------ agentQ's Profile: http://www.unicyclist.com/profile/13021 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#16
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![]() agentQ;1169310 wrote: You cant compare bike to unis here. Bikes do not come close to the amount of torque and stress which is required from a unicycle hub. Maybe, but I ride road and XC, not trials ![]() Every single ISIS hub available to me right now except for the KH Ti is too heavy and too strong for what I use it for. -- GizmoDuck The Induni Unicycle Tour 2009. Unicycle Tour of India. Email me for details. www.induni.adventureunicyclist.com The Uninam Tour 2008.....Hanoi to Saigon!!! www.uninam.net The SINZ Unicycle Tour 2007....South Island, New Zealand www.sinzuni.org ------------------------------------------------------------------------ GizmoDuck's Profile: http://www.unicyclist.com/profile/794 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#17
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![]() If you did the Hub from Aluminium, from what material you plan to do the Cranks then ? Aluminium Cranks mounted on an Aluminium ISIS Hub could result in some trouble I think. Did you think you will feel the difference from 100 gramm maybe on a 36" or 29" while riding ? Didn't the tire itself influence it much more ? I also see to many Bike parts (which are very light mostly) brake week by week in the Hall where we do training. I love to have a trusted feeling in my hub and parts while riding a vehicle (mono, bike, moto...) -- olarf 'unicycle.tv' (http://www.unicycle.tv) 'gunf.org' (http://www.gunf.org) 'e-u-c.info' (http://www.e-u-c.info) 'IUF' (http://unicycling.org/iuf/) ------------------------------------------------------------------------ olarf's Profile: http://www.unicyclist.com/profile/10588 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#18
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![]() Good point. ISIS was never intended for an aluminum axle. Weight savings can come from using a bigger hole through the axle (M15 axle bolt instead of an M12 bolt), but I've never offered an M15 option because the market is very small, weight savings are not that noticeable in the overall scheme of things, and it is really hard to predict what people will do with a product once it's sold. I'd rather have something a few grams heavier that is versatile for everything. Making flanges and hub body from aluminum instead of CrMo doesn't save much if any weight because the flanges and hub body use thicker material; however it could provide a better flange surface and angle for the spokes. I'm working on something in that regard but won't have anything to release just yet. Kris -- danger_uni ------------------------------------------------------------------------ danger_uni's Profile: http://www.unicyclist.com/profile/21 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#19
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![]() GizmoDuck;1169301 wrote: There are a couple of other advantages of Ti you haven't pointed out: -It's expensive ![]() slightly better at getting you from A to B. You buy it because not every Tom, Joe and Mary has one. Lol, unicycle elitism. You buy it because there are not enough Titanium hubs for everyone and you are one of the few with enough money. Very typical Ken! -- Rowan ------------------------------------------------------------------------ Rowan's Profile: http://www.unicyclist.com/profile/3772 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
#20
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![]() gerblefranklin;1169169 wrote: The amount of misinformation in the cycling/RC anything/Motosports communities is ridiculous. Any thread like this is a fine example. pedrotejada, Titanium is NOT rigid. It has a significantly lower modulous of elasticity than steel ( http://tinyurl.com/8z68xw ), making it far flexier. I seem to remember talking to Kris about this issue when discussing whether titanium muni frames are worth the trouble. Also, since the design of the steel and titanium hubs is essentially identical, we can compare strength and make reasonable predictions. But you are right to say good design work should account for material choice therein. Skorbro, your post makes it sound like you've never picked up a big chunk of titanium while expecting it to be steel. It is a dramatic experience to notice how light it is. And my source for the density and strengths of materials is _Machinery's_Handbook,_27th_Edition_. Go buy yourself a copy if you don't believe me. The density of titanium is, according to my copy of _Machinery's_Handbook,_27th_Edition_, 0.163 lb/in^3, while steel is 0.25 lb/in^3. So titanium is about 35% less dense. In a situation where strength is the ultimate issue, and the dimensions of the part are fixed (we can't make bigger ISIS splines), what matters are the strength to volume ratios. 6Al-4V titanium, the alloy which I believe Kris uses in the hubs, has a (0.5% ?) yield strength ranging from 120-160 ksi, depending on heat treatment. While 4130/4140 steel, depending on heat treat, has a 0.2% yield strength of 100-155 ksi. 4130 steel can be made much harder than 6Al-4V titanium. So if the titanium hub is fabricated perfectly, it can be of comparable strength to the steel hub, but it is unlikely to ever exceed the steel hub's strength. I am ignoring spline hardness, by the way, since I assume no rider is regularly changing cranks. Now, factor in the issues with the difficulty of welding titanium, and quality control thereof, and the titanium hub's strength is an issue. Hence the fact that a much smaller sample of riders has already broken a titanium hub, while I, at least, have never seen a broken steel hub. If the titanium hub were machined from solid (prohibitively expensive), I would have more faith in its durability. You would not be wrong to argue that the softer titanium hub builds a stronger wheel by conforming to the spokes better, but I don't think that's where a hub will be failing. I hope this clears things up. And the answer to the original question is, the titanium hub is ONLY worth getting if you aren't breaking the steel hub. If you are, you should either switch to profile, or get a custom built hub/crankset with a larger splined interface. P.S. Rowan, you are right. I did mean Joe Dyson. i have not dealt much at all with titanium, but i knew there was misinformation in the posts, so i was hoping that i would draw out a post like yours faster, and alert everyone to the misinformation. its all good now. interesting stuff... -- skrobo Unicycle For Christ 'MY VIDEOS' (http://www.youtube.com/profile?user=skroboskim) 'World Record' (http://www.youtube.com/watch?v=oig5IEq-v4Y) 94cm Highest Hop (rolling) 308cm Longest Hop (10 feet) 210cm Static Flat Gap ------------------------------------------------------------------------ skrobo's Profile: http://www.unicyclist.com/profile/12272 View this thread: http://www.unicyclist.com/thread/75414 Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- http://www.usenet.com |
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