mafu26 Posted January 6, 2008 Report Share Posted January 6, 2008 I will look into posting some results, if I do can you read them?I study mechanical engineering and i've started using Abaqus for FEA and also a little bit on Solidworks using cosmos. Just interested in where the stress intensity points are as i've never seen a frame being FEA'd. Cheers Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 6, 2008 Report Share Posted January 6, 2008 I study mechanical engineering and i've started using Abaqus for FEA and also a little bit on Solidworks using cosmos. Just interested in where the stress intensity points are as i've never seen a frame being FEA'd. CheersI'll see what I can come up with, as I need to run the stock though analysis. Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 6, 2008 Report Share Posted January 6, 2008 I study mechanical engineering and i've started using Abaqus for FEA and also a little bit on Solidworks using cosmos. Just interested in where the stress intensity points are as i've never seen a frame being FEA'd. CheersToday is your lucky day sunshine. Knock yourself out. These are from a couple of years back though.http://www.panpa.com/test/ECHO-HIFI-BACKWARD-1.wmvhttp://www.panpa.com/test/ECHO-HIFI-BACKWARD-2.wmvhttp://www.panpa.com/test/ECHO-HIFI-BACKWARD-3.wmvhttp://www.panpa.com/test/ECHO-HIFI-BACKWARD-4.wmvhttp://www.panpa.com/test/ECHO-HIFI-FORWARD-1.wmvhttp://www.panpa.com/test/ECHO-HIFI-FORWARD-2.wmvhttp://www.panpa.com/test/ECHO-HIFI-FORWARD-3.wmvhttp://www.panpa.com/test/ECHO-HIFI-FORWARD-4.wmvKOXX：http://www.panpa.com/test/KOXX-XTP-TEST-BACKWARD-1.wmvhttp://www.panpa.com/test/KOXX-XTP-TEST-BACKWARD-2.wmvhttp://www.panpa.com/test/KOXX-XTP-TEST-BACKWARD-3.wmvhttp://www.panpa.com/test/KOXX-XTP-TEST-FORWARD-1.wmvhttp://www.panpa.com/test/KOXX-XTP-TEST-FORWARD-2.wmvhttp://www.panpa.com/test/KOXX-XTP-TEST-FORWARD-3.wmvEDIT: Whoops they're gone now. Hold on.These are the pictures, in this topic http://www.observedtrials.net/vb/showthread.php?t=12271 Quote Link to comment Share on other sites More sharing options...
Mark W Posted January 6, 2008 Report Share Posted January 6, 2008 I really think you should look into a fastening system so the frame can be built up from different modules.That must be the way forward in trials, having frames which you can build up yourself to match your riding style and preferences.Already been mentioned in this thread and another one involving Onza - it's not a viable option.Besides, there are so many frames out now you could pretty much get one tailor-made for your riding off the shelf, or just get a custom one? Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 6, 2008 Report Share Posted January 6, 2008 (edited) That design looks alot better thn the previous 26inch design, only thing to remember when making a frame that low is whether when running a wide rim such as a koxx one that the cylinders of the magura will not catch on the cranks.Otherwise an awsome frame, have you desided whether you are going to add disc and maggy mounts?AdamHere is a shot of the drive train spacing w/ a White Industries FFW. I think it'll be good, but I need to model up a Dengura... anyone got one?... custom geo. frames! Now that's a novel idea, and something I already mentioned I would consider doing.I could see swappable dropouts being a possibility. Edited January 6, 2008 by Dang! Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 7, 2008 Report Share Posted January 7, 2008 Geometry of the Stock:I took a suggestion from both TRA and Pete Wright (sp?)1095mm wheelbase71.5 deg. head tube angle+30mm bottom bracket rise385mm chain stays26.5" cockpitBased on the Czar Long. Quote Link to comment Share on other sites More sharing options...
Walleee Posted January 7, 2008 Report Share Posted January 7, 2008 You can be forgivem this once, but Pete Wright isn't the sort of man to take advice from on anything. Quote Link to comment Share on other sites More sharing options...
mafu26 Posted January 7, 2008 Report Share Posted January 7, 2008 cool pics, cheers tomm. shame the vids don't work. its impressive how they managed to 3D model that headtube! Quote Link to comment Share on other sites More sharing options...
poopipe Posted January 7, 2008 Report Share Posted January 7, 2008 71.5 deg. head tube anglewhy do trials frames have such baggy-ass headangles? Quote Link to comment Share on other sites More sharing options...
eskimo Posted January 7, 2008 Report Share Posted January 7, 2008 why do trials frames have such baggy-ass headangles?Dunno? So they can have a longer wheelbase? Again i dunno but it works. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted January 7, 2008 Report Share Posted January 7, 2008 i think you should go with something along the lines of: 1085, +35/40, 380, 71.5 Quote Link to comment Share on other sites More sharing options...
Walleee Posted January 7, 2008 Report Share Posted January 7, 2008 why do trials frames have such baggy-ass headangles?I Thought it made rolling stuff easier, well, at least made you less likely to flip over the front. Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 7, 2008 Report Share Posted January 7, 2008 I Thought it made rolling stuff easier,And taps (less likely to hang up on the wall), and hooks I think. Quote Link to comment Share on other sites More sharing options...
Tom_ Posted January 7, 2008 Report Share Posted January 7, 2008 Geometry of the Stock:I took a suggestion from both TRA and Pete Wright (sp?)1095mm wheelbase71.5 deg. head tube angle+30mm bottom bracket rise385mm chain stays26.5" cockpitBased on the Czar Long.Sounds nice but a tad long!You can be forgivem this once, but Pete Wright isn't the sort of man to take advice from on anything.From what I remember all that time ago in NMC this statment could not be more correct.i think you should go with something along the lines of: 1085, +35/40, 380, 71.5I would agree Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 7, 2008 Report Share Posted January 7, 2008 I am all ears to suggestions about geometry and methods, in particular suggestions that have supporting information such as reason why.Both Pete and TRA mentioned the stated their thoughts on a geometry that they felt would feel right to them and why, and the information was offered separately. And though I do not know either of them personally, I felt their reasoning was sound, and interestingly similar.As far as other and future geo's I am willing to build to what the trials community wants. This also further proves my feeling that no single geo. is right for everybody. If you are rider that honestly knows and can realize the subtleties from one geo. to the next, than you may need a frame built to your specific needs. Quote Link to comment Share on other sites More sharing options...
Jamie_Neal Posted January 8, 2008 Report Share Posted January 8, 2008 Geometry of the Stock:I took a suggestion from both TRA and Pete Wright (sp?)1095mm wheelbase71.5 deg. head tube angle+30mm bottom bracket rise385mm chain stays26.5" cockpitBased on the Czar Long.Having ridden a 1090 stock with a 74 deg. head angle, I would definatly go for a steeper head angle. Same BB rise or possibly +40.Probably in the region of 72.5 to get the best of both worlds.Looks like a cool frame though - get riding it. Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 8, 2008 Report Share Posted January 8, 2008 You gotta be careful though as head angle affects the reach loads, if you keep the same wheelbase. For example, a 1095 wheelbase bike with a 74 degree head angle will 'feel' as much as 4cm longer than one with a 70 degree head angle, all other things being equal. You can do the calculations of you like, I did them a while ago and I seem to remember that a 1 degree change in head angle will change the wheelbase by about 1cm (obviously keeping everything else the same). Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 8, 2008 Report Share Posted January 8, 2008 You gotta be careful though as head angle affects the reach loads, if you keep the same wheelbase. For example, a 1095 wheelbase bike with a 74 degree head angle will 'feel' as much as 4cm longer than one with a 70 degree head angle, all other things being equal. You can do the calculations of you like, I did them a while ago and I seem to remember that a 1 degree change in head angle will change the wheelbase by about 1cm (obviously keeping everything else the same).Good point. I think another part that some might not take into consideration is the degree of rake that most forks have built into them, which effect both the wheelbase total and the feel. As I recently found out, the average rake amounts to +40mm to +45mm. So if you start with a 72 degree head tube, with a 410mm fork w/ 45mm of rake, that is an effective 66.25 degrees of realized angle. Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 8, 2008 Report Share Posted January 8, 2008 Yeah but all forks have some degree of rake. Also, pretty much all trials forks are very similar in the amount of 'trail' they have (Trail = distance between a straight line through the head tube and the front dropout), so you just need to design a frame around that. As I understand it, you're only designing frames (Feel free to correct me on that ) so you can just make your frames relative to other designs without worrying about what the forks are doing.However, If your calculations are correct, I'd be intruiged to know how a bike with a 66.25 degree head angle and completely straight fork would ride. I'm guessing the steering would be weird (which is why the the current setup has evolved) but not sure that's an issue on a trials bike. Hmmm. Quote Link to comment Share on other sites More sharing options...
poopipe Posted January 8, 2008 Report Share Posted January 8, 2008 headangle is about more than reach - you compensate for that by lengthening/shortening the front end - sharper angles mean faster steering Thats whiy im confused by the slack headangles on the czar etc - surely having more responsive steering would be a good thing for trials (isn't that the reason people like ashtons ?) . Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 8, 2008 Report Share Posted January 8, 2008 You asked that in this thread... And got an answer. Yes, steeper head angles makes for faster steering but that doesn't really make much difference when all you're doing is hopping around. Steeper head angles are better on streetier frames IMO as they're more fun for front wheel/spinny things and the disadvantages (I.e. less good for taps/hooks) are less relevant on that kind of bike. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted January 8, 2008 Report Share Posted January 8, 2008 (edited) forks at 45mm offset and 408mm length are ideal, also, with disc mounts move then +20 or 30 up the fork, o people with bb7s dont destroy them with the huge leverage created by the wide adapter. Edited January 9, 2008 by Ash-Kennard Quote Link to comment Share on other sites More sharing options...
Luke Rainbird Posted January 8, 2008 Report Share Posted January 8, 2008 forks at 45degrees offset and 408mm length are ideal, also, with disc mounts move then +20 or 30 up the fork, o people with bb7s dont destroy them with the huge leverage created by the wide adapter.Not quite sure how you mean, Ash45mm is what I'd do if I had the chance... Quote Link to comment Share on other sites More sharing options...
Dang! Posted January 9, 2008 Report Share Posted January 9, 2008 Yeah but all forks have some degree of rake. Also, pretty much all trials forks are very similar in the amount of 'trail' they have (Trail = distance between a straight line through the head tube and the front dropout), so you just need to design a frame around that. As I understand it, you're only designing frames (Feel free to correct me on that ) so you can just make your frames relative to other designs without worrying about what the forks are doing.However, If your calculations are correct, I'd be intruiged to know how a bike with a 66.25 degree head angle and completely straight fork would ride. I'm guessing the steering would be weird (which is why the the current setup has evolved) but not sure that's an issue on a trials bike. Hmmm.Trail- right. meant that... and I have included this into my frame wheelbase, and I am not designing forks...yet. :wink2: But it has to be effecting the steering in some way... but I think I am off in my thinking, it effects it in a different way... If one had a fork w/ 0mm of Trail and a 90 deg. head tube angle, they would still be able to turn the wheel, but if they had the same head tube angle and 110mm of trail they would not be able to turn the wheel.hmmmm....So what head tube angle seams the best again? Quote Link to comment Share on other sites More sharing options...
Tomm Posted January 9, 2008 Report Share Posted January 9, 2008 Depends who you talk to really. For a street frame, I reckon 74 - nice and steep. For a pure trials frame, between 70 and 72.5 I think. Quote Link to comment Share on other sites More sharing options...
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