AdamR28 Posted July 28, 2008 Report Share Posted July 28, 2008 Rusevelt, that quote from me is regarding Atomz forks by the way, NOT Trialtech forks. You can see how those forks are constructed here: http://tartybikes.co.uk/product.php?produc...;category_id=40 Quote Link to comment Share on other sites More sharing options...
eskimo Posted July 28, 2008 Report Share Posted July 28, 2008 It should at least have maximum 2.3in clearance for those that want slightly more front end grip. how is the steerer tube joined to the crown, bonded, welded, or something totally different?They say it's changed slightly to improve it as some guy listed on page 1 bent his Atomz's. So maybe still 1 piece like the Atomz/ Viz style.I did read that they have an 'advanced' built in top cap. How is that advanced? Quote Link to comment Share on other sites More sharing options...
Rusevelt Posted July 28, 2008 Report Share Posted July 28, 2008 (edited) Silly me :$ adam i missed that bit totally would be nice if the offset is the same as Koxx Forxx to improve steering and trackstand control. Edited July 28, 2008 by Rusevelt Quote Link to comment Share on other sites More sharing options...
Mark W Posted July 28, 2008 Report Share Posted July 28, 2008 I did read that they have an 'advanced' built in top cap. How is that advanced? Slightly more advanced than hammering a funny shaped nut thing into your steerer tube? Have Dave's recent explorations into the BMX parts world opened his eyes to a few design hints 'n' tips? Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 28, 2008 Report Share Posted July 28, 2008 Does the top cap screw into the inside of the fork steerer? I'd expect a few nasty fatigue failures if this is the case - not as bad as externally threading the steerer of course... Quote Link to comment Share on other sites More sharing options...
Mark W Posted July 28, 2008 Report Share Posted July 28, 2008 Does the top cap screw into the inside of the fork steerer? I'd expect a few nasty fatigue failures if this is the caseHaven't heard on any in the BMX world, and bearing in mind how frighteningly light BMX forks are getting...e.g. Full-on steel Primo Strand forks, with top cap, weigh almost 100g less than the Zoo Python forks do with a star-fangled nut and no cap. Quote Link to comment Share on other sites More sharing options...
AdamR28 Posted July 28, 2008 Report Share Posted July 28, 2008 I'd expect a few nasty fatigue failures if this is the caseWhy's that? (The thread is entirely inside the depth of the stem clamp by the way...) Quote Link to comment Share on other sites More sharing options...
Rusevelt Posted July 28, 2008 Report Share Posted July 28, 2008 Does the top cap screw into the inside of the fork steerer? I'd expect a few nasty fatigue failures if this is the case - not as bad as externally threading the steerer of course...Maybe to keep the headset more secure to the stem steerer tube clamping area, thus less chance of headset play esspecially when turning the bars 90 degree. but like you stated, could pose stress and fatigue problems from doing frontwheel pivot moves and hooks. Quote Link to comment Share on other sites More sharing options...
ben_travis Posted July 28, 2008 Report Share Posted July 28, 2008 Why's that? (The thread is entirely inside the depth of the stem clamp by the way...)just cos your cheeky Quote Link to comment Share on other sites More sharing options...
Mark W Posted July 28, 2008 Report Share Posted July 28, 2008 Maybe to keep the headset more secure to the stem steerer tube clamping area, thus less chance of headset play esspecially when turning the bars 90 degree.Assuming your steerer tube and headtube aren't turbof**ked, there shouldn't be any difference in headset tightness no matter what the angle of your forks is? The preload cap will still be in the same position, relative to the headset? Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted July 28, 2008 Report Share Posted July 28, 2008 Does the top cap screw into the inside of the fork steerer? I'd expect a few nasty fatigue failures if this is the case - not as bad as externally threading the steerer of course...nah seriosly its a fine system, ive had no problem with mine on the atomz so far, but when i cut the steerer down abit, i had to file the burr away which worried me around the threads, but it went on alright so all good Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 28, 2008 Report Share Posted July 28, 2008 If the thread is within the height of the stem clamp then it's not an issue - if it's threaded past the bottom of the stem, the bending between the stem and the headset will lead to fatigue cracking a lot quicker than with a constant cross section tube of the same material (Even if the thinnest point in both tubes is the same thickness). If the thread is rolled rather than cut or the surface is shot peened after cutting it will last better than if it's left smooth too.Only having the thread go 40mm ish down the fork steerer will cause people who want to cut the steerer shorter to fit their frames problems fitting the top cap though. As for a threaded top cap loading the headset better, once the stem has been clamped into position you can take the top cap off and it will have no effect on the load on the headset bearings as the stem does all the work in keeping the headset tight. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted July 28, 2008 Report Share Posted July 28, 2008 i lost interest reading what you said, but the threads dont go that deep maybe 2cm and the top cap has a chamffered bottom so you can cut them down abit without a problem Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 28, 2008 Report Share Posted July 28, 2008 20mm of thread kind of limits the amount you can cut the steerer down by then... Though trials frames probably have nothing like the headtube length range you see in XC/DH bikes, so it may not be a limiting factor, though 200mm seems a little long to be within 20mm of what most frames need... Quote Link to comment Share on other sites More sharing options...
JonMack Posted July 28, 2008 Report Share Posted July 28, 2008 F*ck knows what you're on about but as Mark said, it's been fine in the BMX world for the last 5+ years? Infact I'd rather run an internally threaded steerer than a stupid top-cap system. Quote Link to comment Share on other sites More sharing options...
Tom Booth Posted July 28, 2008 Report Share Posted July 28, 2008 Aren't Onza Smart guy forks the exact same? Quote Link to comment Share on other sites More sharing options...
JonMack Posted July 28, 2008 Report Share Posted July 28, 2008 (edited) Looks strong enough to me... Edited July 28, 2008 by Mark King Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted July 28, 2008 Report Share Posted July 28, 2008 Aren't Onza Smart guy forks the exact same?Yeah, they use a one piece threaded topcap which bolts straight into the top of the forks. Nice and neat . Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 28, 2008 Report Share Posted July 28, 2008 Provided the threads don't extend to anywhere on the steerer that's stressed in bending (If the threads end within the stem clamp, which appears to be the case with the forks being discussed) there's no issue. If they do then fatigue cracking is extremely likely at the root of the thread where the bending moment in the steerer is at its peak. Quote Link to comment Share on other sites More sharing options...
The Duck Posted July 28, 2008 Report Share Posted July 28, 2008 Light bikes and "Lines" are uncool, thats what makes the rest of the mountainbike world see trials as shitttt.Hahaha utter wank. Get out. Quote Link to comment Share on other sites More sharing options...
OD404 Posted July 28, 2008 Report Share Posted July 28, 2008 Provided the threads don't extend to anywhere on the steerer that's stressed in bending (If the threads end within the stem clamp, which appears to be the case with the forks being discussed) there's no issue. If they do then fatigue cracking is extremely likely at the root of the thread where the bending moment in the steerer is at its peak.The thread depth isn't so much of an issue in my eyes, more the position of the Last Engaged Thread (LET). LET is basically the last thread which is engaged with the top cap. The presence of the top cap induces larger bending moments in the thread directly below it, leading to higher stress. In just about every fork case the LET is so high in the clamp that it barely moves anyway so no issue there.But let's face it, most joining methods between the fork and steerer are weaker than a steel/ali tube with a thread cut in it and are likely to develop cracks first. Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 28, 2008 Report Share Posted July 28, 2008 (edited) The loading on the threads from the top cap and the location of the last engaged thread is almost totally irrelevant to the failure I'm talking about. What is relevant is the increase in the stress concentration at the root of the thread cut into the steerer caused by the geometry of the material. I'm not sure if you're familiar with threaded headsets, but the two most common failure locations on forks with threaded headsets was within the threaded area or within 20-30mm of the top of the fork crown as these are the highest stress areas in the fork (Peak bending is at the lower headset cup, but that's usually reinforced enough that peak stress occurs either at the root of the threads or just above the reinforced area near the fork crown - peak stress is where an overload failure will occur or where fatigue cracking will begin. Fatigue cracks need tensile stress, while overload failure stresses can be tensile or compressive). Fatigue type failure was most common at the threaded area, while overload or fatigue would cause the failure near the crown. The threads being cut on the inside rather than the outside of the steerer tube will reduce the stress somewhat (Peak strain (And stress) will always occur at the outside of a structure loaded in bending) compared to cutting them on the outside, but I wouldn't trust an internally threaded aluminium steerer unless the threaded area sees no bending stress - i.e. is well within the area clamped by the stem. The failures I've seen were all in steel as aluminium isn't hard enough to allow threaded headsets with standard threads to be reliable AFAIK. Steel has much better resistance to fatigue failure than Al in the first place too.And as for most joining methods between the fork and steerer being weaker than a steel/Al tube with a thread cut in it - that would be almost exactly wrong... Star nuts, while they create scratches in the steerer, will remove less material and unless you use a very long bolt, remain within the area clamped by the stem, which doesn't allow bending to be felt by the headtube the stem has clamped as well as superimposing compressive stress on the headtube, further reducing the peak tensile stress in that area. Headlock type systems create no extra stress anywhere on the steerer and are the best solution unless you're desperately worried about saving weight. Edited July 28, 2008 by psycholist Quote Link to comment Share on other sites More sharing options...
OD404 Posted July 28, 2008 Report Share Posted July 28, 2008 The loading on the threads from the top cap and the location of the last engaged thread is almost totally irrelevant to the failure I'm talking about. What is relevant is the increase in the stress concentration at the root of the thread cut into the steerer caused by the geometry of the material. I'm not sure if you're familiar with threaded headsets, but the two most common failure locations on forks with threaded headsets was within the threaded area or within 20-30mm of the top of the fork crown as these are the highest stress areas in the fork (Peak bending is at the lower headset cup, but that's usually reinforced enough that peak stress occurs either at the root of the threads or just above the reinforced area near the fork crown - peak stress is where an overload failure will occur or where fatigue cracking will begin. Fatigue cracks need tensile stress, while overload failure stresses can be tensile or compressive). Fatigue type failure was most common at the threaded area, while overload or fatigue would cause the failure near the crown. The threads being cut on the inside rather than the outside of the steerer tube will reduce the stress somewhat (Peak strain (And stress) will always occur at the outside of a structure loaded in bending) compared to cutting them on the outside, but I wouldn't trust an internally threaded aluminium steerer unless the threaded area sees no bending stress - i.e. is well within the area clamped by the stem. The failures I've seen were all in steel as aluminium isn't hard enough to allow threaded headsets with standard threads to be reliable AFAIK. Steel has much better resistance to fatigue failure than Al in the first place too.All very correct, I'm not debating the fatigue failure mechanism for a bar with a thread in it. Though you obviously have more experience with bike components than I do. My comments were born from experience with engine main bearing caps where the entire hole (pilot and threaded regions) where in bending and the failure occurs at the last engaged thread, irrelevant of the position of peak bending in relation to the cut thread. Though I did say (contradicting myself somewhat) that an LET wasn't all that likely (given the stem clamping round the outside of the steerer). My fault with that one it would seem. And as for most joining methods between the fork and steerer being weaker than a steel/Al tube with a thread cut in it - that would be almost exactly wrong... Star nuts, while they create scratches in the steerer, will remove less material and unless you use a very long bolt, remain within the area clamped by the stem, which doesn't allow bending to be felt by the headtube the stem has clamped as well as superimposing compressive stress on the headtube, further reducing the peak tensile stress in that area. Headlock type systems create no extra stress anywhere on the steerer and are the best solution unless you're desperately worried about saving weight.I think you have misunderstood the area I was refering to. I was refering to the join at the bottom of the steerer tube where the fork legs are, which is probably a more common failure location in the grand scheme of things (from what I've seen of broken forks anyway).I guess the question that really needs to be asked (of any fork to some extent) is what's going to bend more, the legs or the steerer? As that will dictate heavily the peak stress points and areas of low fatigue life. Quote Link to comment Share on other sites More sharing options...
Adam-Griffin Posted July 28, 2008 Report Share Posted July 28, 2008 Havn't read the whole topic but i assume it would be akward to use these forks with a monty stem ? Quote Link to comment Share on other sites More sharing options...
Tony Harrison Posted July 28, 2008 Report Share Posted July 28, 2008 told u i didnt read what u put, i couldnt give 2 flying shits what u think of me LOL.lots of love.MatxMan, people like you give spastics a bad name. I'm seriously considering not renewing my monthly Scope donation agreement. Quote Link to comment Share on other sites More sharing options...
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