hayleyearth Posted October 6, 2015 Share Please have this discussion about the stress analysis right here on the hub if you don't mind. I spent a large part of my working life on mechanical and structural design and have much more than just an interest in this topic. Would be great to see what assumptions, load cases and calculation methods comes out of this. Clearly not enough to 'thumb suck' yet... (And I thought I would not have been the only one that does this on a daily basis.... ) Link to comment Share on other sites More sharing options...
MaxTBehrens Posted October 6, 2015 Share Please have this discussion about the stress analysis right here on the hub if you don't mind. I spent a large part of my working life on mechanical and structural design and have much more than just an interest in this topic. Would be great to see what assumptions, load cases and calculation methods comes out of this.Sure! I have no problem doing so, if its fine with JKK Link to comment Share on other sites More sharing options...
JKK Posted October 6, 2015 Share Sure! I have no problem doing so, if its fine with JKK Link to comment Share on other sites More sharing options...
rudi-h Posted October 8, 2015 Share Clearly not enough to 'thumb suck' yet... (And I thought I would not have been the only one that does this on a daily basis.... ) hehe, i would have been fine with a thumb suck if I didn't crack 3 frames in the last 4 years... but then again, maybe i just suck at riding bikes Link to comment Share on other sites More sharing options...
nolipoli Posted October 8, 2015 Share hehe, i would have been fine with a thumb suck if I didn't crack 3 frames in the last 4 years... but then again, maybe i just suck at riding bikesOr maybe it means that no-one really knows what they are doing when designing bikes. So one can't really do worse. Link to comment Share on other sites More sharing options...
MaxTBehrens Posted October 8, 2015 Share I've been reading a lot about the anti-squatting designs, and reviewing the arch at which the wheel moves throughout the travel, and have realized that my concentric BB and pivot design has many flaws. Many designs compromise on the chain growth, which causes pedal feedback and reduces power, to stop or minimalise squatting. But where as, according to what I have read, squatting and bobbing from acceleration also decreases power. And obviously is annoying. So I'd like to know your opinions about this. Compromising on squatting for an isolated drive train system, or compromise on pedal feedback to stop squatting? Link to comment Share on other sites More sharing options...
MaxTBehrens Posted October 8, 2015 Share Secondly, the arch at which the rear wheel moves is not ideal for bumps. A wider arch and one higher up will have a better curvature for both small bump sensitivity as well as resisting to bottom out. Opinions? Link to comment Share on other sites More sharing options...
nolipoli Posted October 8, 2015 Share its all about getting a balance. Your ideal may be different from someone else's. Sometimes you may compromise slightly on the wheel path for the sake of simplicity, or lightness or even aesthetics.A modern air shock will have built in platform damping which will compensate for a lot of geometry inefficiencies. Also letting the back wheel move backwards when hitting sharp edges helps to smooth it out, and minimises the braking affect of the bump. Too much backwards movement will cause your chain growth issues again. Link to comment Share on other sites More sharing options...
MaxTBehrens Posted October 19, 2015 Share So I've decided I'm finished with the concentric BB and pivot thing, sort of, and have moved on to the VPP and DW-link designs. So here comes my first design in that area. Again with more or less the same style and geometry as the previous versions, but not a concentric design. The design has two rockers, one around the BB and one on the down tube. This has a maximum chain growth of just under 19mm. I quite like this design for its wheel arch as it goes through its travel, and I've placed the shock so to use shorts linkages and not to put forces perpendicular to a tube. Also the shock is placed on the down tube, which is a larger stronger tube. Here is the frame before compession And here is the frame after compression Link to comment Share on other sites More sharing options...
nolipoli Posted October 21, 2015 Share That looks really neat. Silverback uses a similar link around the BB that is quite effective. Link to comment Share on other sites More sharing options...
Huli Posted October 22, 2015 Share That is a serious bottom bracket design! I like it! Where are you sourcing your bearings from? Link to comment Share on other sites More sharing options...
MaxTBehrens Posted October 22, 2015 Share That looks really neat. Silverback uses a similar link around the BB that is quite effective.Thanks! Silverbacks design is slightly different, as it places two bearings on top of each other, after you have placed the bottom bracket in. mine uses the BB as a pivot. That is a serious bottom bracket design! I like it! Where are you sourcing your bearings from?I'm still in design stages, so no sourcing yet. But I plan on using common press fit bottom brackets. Link to comment Share on other sites More sharing options...
nolipoli Posted October 22, 2015 Share Have a look at the BLKMRKT Killswitch dirtjumper. It has a configuration similar to what you are after (I think) Link to comment Share on other sites More sharing options...
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