Ox_Wagon

Have not seen an 29 speed yet. 27 or 30 speed is the closest. I am also still waiting to see a GF 29er in the flesh or one of the new Trek 69ers (26" rear wheel and 29" frontwheel).

I think you mean 29" wheeled bikes.

It is called FUD. They try to create Fear, Uncertainty and Doubt. It is an old Microsoft strategy.

There aren?t a lot of full sus 29er frames out there especially if you on a tight budget.

On B grade items, I was looking at buy in a set of American Classic AM420 wheels so I checked Road bike Review. There was a bunch of people having problems with these wheel sets which seamed to originate from a third party that bought hubs and rims from AM then build up by them and sold as the real deal. <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> BUT with that type of service I will go with Mr Bornman advice and stick to standard components that you can get from different sources. I usually check that if a suspension frame or hubs uses sealed bearings that it is standard sizes so that you can get them from any Bearingman etc. Not like me that had to buy a new Campy hub to get new cones and bearings for my current wheel.

TitusTI, would you recommend a 29er hardtail?<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Edman, I fully agree with you. The other problems with all models are if you don?t set up the model as close as possible to reality all that you get, as you said previously, is a nice wallpapers. <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Some comments and questions on your constraints: 1) What do you mean by ?The spokes are constrained to have zero displacements, but free rotation at the hub?. It sound like you are fixing the hub and that no torsion load can be transferred to the hub by the spokes. If so it sounds good. 2)?They are rigidly connected to the rim.? This unfortunately does not reflect reality. I know you did not agree with my constraint but we can discus it. Check the campy pic and do the rim and spoke test. You could get away with it if you apply pre-tension to the spokes and insure that the pre-tension is high enough to insure that even after applying the 100N force to that rim that all the spokes are still in tension. According to Mister Bornman?s experiment and your reverence, a pre-tension that gives you a top spoke tension that stays the same before and after the force is applied should do the job. 3) ?There is no pretension applied?. This plus the rigidly connection of the spokes to the rim is the thing that is causing most of the problems. It means that the moment you have ANY deflection on the rim the spokes would be in compression. This is shown in your pic (2500x) 4) ?A 100N force is applied to the rim between the bottom three spokes?. I assume that you fixing the hub displacement as mentioned in your first point. 5) ?it does not model buckling?. The net guy also used this assumption. IF your spokes are always in tension this is a valid assumption. Have a think about it. I looking forward to your comment on my comments. PS: Enjoy the festive season. I am almost out of here. Ox_Wagon2007-12-21 03:58:41

Hi, my name is Ox_wagon and my LBS build up my wheels with strait gauge DT spoke and spoke WASHERS <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Hi, Ox_wagoooooon. Ok, with the Spoke Washer Anonymous (SWA) group session in full swing I have to add that I haven?t had any problems with the wheels again. They previously had sapim dubble butted spokes which is as far as I know also very good spokes. The impression that I got from the LBS was that the washer, being very soft, would deform and give you a better fit between underside of the spoke head and side of the hub flange that isn?t properly aligned. Mister Bornman?s explanation about the washer being used to correct too long J-bends also makes a lot of sense. Ox_Wagon2007-12-21 02:53:26

I am glad it had some entertainment value.<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

BigH, it is either you or me or maybe both us? Who cares <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> ManWithnoName, do we get any clue who your talking about? Hub name maybe? Sounds like someone I may know. BMC, this thread has been so solidly hijack that if it was a car it would already been in <?:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Nigeriaon>, makes you think does?t it . We all now who is in Nigeria,on> I can see a conspiracy there. Maybe it is all a 416(?) scam. Ox_Wagon2007-12-20 09:22:14

I that case I will remove my statement about rider weight. I personally think if one is a bit heavier (>80kg) it is better stick to a custom build wheels with higher spoke count (32-36). I know some shops tend to recommend the DRC ST17 rims. So far I have not picked up any problems with mine. At this moment I would not even consider a flashy light weight wheel set because it is stupid to me to spend R3000 plus on a wheel set to save 500g while I am 20kg plus overweight which I most probably will damage because I am too heavy. <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Coooool

Agreed Greatwhite, shame on us . Back to the original problem.This bit . At my weight I would typically stay away from anything exotic like that. I must say when I lost a number of my spoke on my current wheel set I ask my LBS to build them like tandem wheels. Since then I haven?t had any problems.<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Ox_Wagon2007-12-20 07:57:45

More semantics: "with only the spokes directly under the hub decreasing their tension" <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> It does not state: "with only the spokes directly under the hub being in compression" As show in the FEM pic. The area below the hub is the unloaded zone and not the loaded zone.

Edman, thanks for your inputs, please don't put too much effort into it is only for interest sake. I would not even now where to start. It would be a major problem to model the unloading of nipple as it lifts of the rim. I think that is why all the internet FEM analysis takes the short cut to rigidly fix the spoke to the rim.<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Mister Borman, I agree that a lot of the info on the Mavic site may be marketing hype especially if you look at R-sys rear wheel and see that they use a normal spoke system on the drive side precisely where you would like to increase lateral stiffness. On the ox_wagon wheels it is rather appropriate. I am heavy and I am slow. That is precisely why I choose the login name. I agree that they have no way of handling tension and you can see how bulky and heavy the spokes are (Generation One Wheels, Refer back to the Mavic different generations of wheels, sorry I could not help my self). The same way the ox_wagon spoke can only take compression so a ?Modern? generation two wheel can only take tension. If we can agree on that we have made major progress. Talking of experiments, try this one. Insert a single spoke in to a rim with its nipple in place. Now pull on it, cool it can take tension. Now push on it, oops it can?t take any compression. That is if you haven?t installed the rim strip yet On the twange test. Funny enough after a lot of thinking, you may have noticed I am a bit slow, looking at what other people say, Edman quote out of the bike book I agree with the result of your experiment. That the tension in the top spoke may be close to the tension of the top spoke with the weight of the rider on it. So doing giving the same amount of ?Twang? Simply put, the deformation of the rim on the bottom of the rim reduces the pre-tension of the bottom spoke. If the pre-tension is large in comparison to the weight place on the wheel, which seams to be the case with most wheels, you can get the situation, with a bit of tweaking, where the reduction in tension due to the deformation of the wheel equals the weight now placed on the wheel. The end result is that the tension in the top spoke stays approximately the same. Here is where most argument derails. The popular argument goes, that because ?nothing? happens in the top spoke all the magic is in the bottom spoke which means that the reduction in tension is the thing keeping the hub in the air. BUT if we have a look at <?:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Newton?s law we see that all the forces should equal zero. Which gives us: Tension in the top spoke = Now reduced tension in the bottom spoke + The weight placed on the wheel. The fact that this new tension in the top suspending the hub is almost the same as the pre-tension in the top spoke is the thing that causes the problems. Ox_Wagon2007-12-20 05:52:14

Sound right

Ok more specific: Page 1: Verbatim quoted:<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> ?A particle is in a state of equilibrium if the resultant forces and moment acting on it are zero, and hence according to Newton?s law of motion it will not have no acceleration and will be at rest ? Page 1, Formula 1.1 Σ Fx = 0 Σ Fy = 0 Σ Fz= 0 So the sum of the forces equals zero if the object(hub) is stationary. Which means that the forces experience in the top spoke is opposite and equal to the force in the bottom spoke plus the weight of the rider. In short the weight is supported by the top spoke as show in my previous pics Edman, I been trawling the internet to try to understand the problem better and it seams everybody is revering to the same FEM model. As previously stated the model is flawed in that it assumes that the bottom spoke can transfer a compression force. In the expensive and pretty picture you can see the bottom spoke buckling, this is only possible if they are in compression. They should have absolutely no load on them exept if they are pressing against the rim liner or inner tube. The only spokes wheels that can handle compression is Mavic?s new R-sys wheels http://www.mavic.com/r-sys/ If you don?t want to believe me go check out their website. Please note the design changes that they had to make to get a spoke(slender beam) to take an compression force. I agree with you that the elongation of the spokes and the deformation of the wheel make it more complex. I think that is precisely what causing the confusion. I would like to know why you say I am constraining the bottom spoke wrongly. Here is a pic I posted in a previous thread that shows the internals of a campy aero rim. There is no way that you can put a compression force on it. I would be interested to see how the FEM looks like if it is properly constrained. If it is your model would you be so kind and humor me and run it with the spokes constained that they can only take a tension force. Pleaseeeeee Ox_Wagon2007-12-20 03:52:34

Not prejudice, I am just regurgitating engineering principals. <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> I recommend any first year engineering textbook that on mechanical of materials. The basic static force systems are usually discussed in the first few pages. You forced me to go dig op my old textbook: Mechanics of Engineering Materials P. P. Benham & R.j. Crawford ISDN : 0582286409 I hope this info may be of help.

It is a bit unclear with out a pic but sounds promising. Again, not to put words in your mouth, is ?sound if? you agree with me that BigH weight is SUSPENDED from the top in the same way that the hub is suspended from the top spokes. I agree with you about loss of lateral stiffness if the tension reduces too much in the bottom spoke. This is precisely the reason that Mavic develop the new R-sys wheelset (http://www.mavic.com/r-sys/). <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> My turn with a few pics Let assume Shimano/Campy/Alex/Fucrum/etc brings out a new super wheelset in response to Mavic?s new R-sys uses unobtainium to make a super stiff rim that only needs 4 spokes with very little rim deflection. Unobtainium is also used for the spokes which means there is very little elogation of the spoke under tension. Which means one can reduce the problem to a very simplified two spoke system shown in the figure A. Figure B shows the effect of the pre-tension on the Hub (Node) with no weight on the hub. Figure C shows the effect of a portion of the rider weight plus the bottom spoke pre-tension on the tension on the top spoke. Lastly let?s look at the collapsing wheel scenario. Lets again look at the simplified two spoke wheel. Firstly let?s cut the bottom spoke. The wheel(hub) is unride able but it does not collapse. Now lets look what happens when we cut the top spoke. The wheel(hub) collapses. Ox_Wagon2007-12-19 08:35:25

So at least you agree that the above mentioned finite element analysis is flawed. But if you agree that the all the spokes are ALWAYS in tension and no compression force can be transferred how does the hub press on the road with out effecting the tension of the top spokes? <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> On the "twang", I haven?t heard of the unit before nor have I seen any standard (SABS, DIN , ASME etc) on it nor instruments that measure it. What is the conversion factor between "twang" and Force? As such I have difficulty excepting any ?experiment? where the "twang" is used as the only measurable to prove a theory that is not supported by engineering theory. Lastly why on earth would a wheel collapse if it loses tension in ?the? bottom spoke or even the bottom 3 or 4 spokes? The rim may be damages but it would not collapse.

Here we go again........ <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> This guy did a finite element analysis of a bicycle wheel is fundamentally flawed in that it assumes: 1) No buckling of slender beams (Spokes) 2) It is possible to transfer a compression force from the spoke to the rim. NOT! http://www.astounding.org.uk/ian/wheel/index.html So it is only possible for a rim to stand on the bottom spoke IF 1) You glue the nipple to the rim 2) Use REALY strong rim tape 3) Have a really strong inner tube, the Tubeless guys has a problem Check the following tread: https://www.bikehub.co.za/forum_posts.asp?TID=16361&KW=&PID=251045#251045 IanJ, your correct. The top spokes sees the combined weight of the rider plus the tension of the bottom spokes, this elongates the top spokes a bit which in turns shortens the bottom spokes reducing the tension. Ox_Wagon2007-12-19 03:54:27

In <?:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Pretoria I would recommend Run Away Sport and Running In. NB is the best value for money. NB and Asics (top seller) are also available in different widths which are good as ZA feet tend to be wider. Nike is good but tends to be narrow. <?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> BUT as previously said, it is more important to get the right type of shoe than the brand.

Joss, from someone that sells bikes/frames from a doormat?

Wild

Yip, Jan left middle of the year. But the rest of the guys there have done multiple Ironmans. They also stock Tri wetsuits and other Tri stuff which is hard to find in PTA/JHB area.