nolipoli Posted March 29, 2015 Posted March 29, 2015 I have been fiddling a bit with suspension designs, and have come to realist why so many bike brands use fairly big linkages - the smaller they are, the tighter your tolerances have to be to get accurate travel. I am going to have to start again with bigger linkages. ????
Burner Posted March 31, 2015 Author Posted March 31, 2015 makes sense....I am hoping to make use of large needle bearings and small inline linkages to make the bike look solid but not bulky. The material selection is driving me crazy . I need to get it out of the way.....metal is easier for me to fabricate, and composites can get away with a lot more shaping. I did some rough sketches to start formulating the frame design and to see how it all might come together. The rear shock placement is one of the issues because the shock will need some wizardry to fit where I want it.
nolipoli Posted March 31, 2015 Posted March 31, 2015 I have been using the Linkage X3 Demo software for the suspension. It works really well, allowing you to start with an existing design (Like Giant's NRS for example) and then modify to your heart's content. It even calculates leverage ratios and chain growth numbers. I have already finalised my new large link suspension.
Burner Posted March 31, 2015 Author Posted March 31, 2015 I have been using the Linkage X3 Demo software for the suspension. It works really well, allowing you to start with an existing design (Like Giant's NRS for example) and then modify to your heart's content. It even calculates leverage ratios and chain growth numbers. I have already finalised my new large link suspension. FS6-R4 Susp LHS.jpg wow I am loving that so bad right now!!!!! Well done! I've been toying with different floating designs but I think yours looks spot on. The key is all in the leverage which I'm sure you have tested on Linkage already. Please keep me updated on your progress, you welcome to post as many progress pics here as you want
nolipoli Posted April 1, 2015 Posted April 1, 2015 Haha cool! Sadly for me, the design stuff is what comes easily. I am still sourcing a viable frame building jig (I saw a nice idea called the Jiggernaut on Kickstarter), and then still need to purchase my steel and Aluminium for the the linkages. One thing that I am battling with is the apparent lack of 4130 steel plate for gussets etc.
Burner Posted April 1, 2015 Author Posted April 1, 2015 Haha cool! Sadly for me, the design stuff is what comes easily. I am still sourcing a viable frame building jig (I saw a nice idea called the Jiggernaut on Kickstarter), and then still need to purchase my steel and Aluminium for the the linkages. One thing that I am battling with is the apparent lack of 4130 steel plate for gussets etc.The jig is easy to build. I used to have a range of engineering equipment when I built cars. I can have it put together by a fellow engineer, but he's here in Cape Town. If you are really interested, I can arrange it for you. Are you planning to do the welding yourself?
Captain Fastbastard Mayhem Posted April 1, 2015 Posted April 1, 2015 The jig is easy to build. I used to have a range of engineering equipment when I built cars. I can have it put together by a fellow engineer, but he's here in Cape Town. If you are really interested, I can arrange it for you. Are you planning to do the welding yourself?burner - off topic, but on the topic of jigging and cars - 442 IRS design - have you any experience in it, and if so could you PM me? Shot. As for the build - really lekker to see hoiw it's progressing in the design phases. Any particular reason you went for a design where the compression is driven from both ends, as opposed to a full floater type design (trek etc) where the shock is driven from one end and the other end (chainstay extension) goes with it at a lower rate of movement?
popcorn_skollie Posted April 1, 2015 Posted April 1, 2015 burner - off topic, but on the topic of jigging and cars - 442 IRS design - have you any experience in it, and if so could you PM me? Shot. As for the build - really lekker to see hoiw it's progressing in the design phases. Any particular reason you went for a design where the compression is driven from both ends, as opposed to a full floater type design (trek etc) where the shock is driven from one end and the other end (chainstay extension) goes with it at a lower rate of movement?I'm battling to wrap my head around this too. Disclaimer: Everything I'm about to say comes from a point of pure ignorance.Still battling to understand the different systems and the pros and cons of each. Anyways if I understand you correctly you are talking about the rocker looking like its actually part of the seat stay and not pivoting off it?ie: http://i.imgur.com/M7rY2Gr.jpgSomeone needs to ELI5 this for me.Explain it like I'm 5
popcorn_skollie Posted April 1, 2015 Posted April 1, 2015 https://www.youtube.com/watch?v=9oBtM0Joqc0 https://www.youtube.com/watch?list=PL3392F0304AED1E0D&v=MvjwuynHwGI
Captain Fastbastard Mayhem Posted April 1, 2015 Posted April 1, 2015 I'm battling to wrap my head around this too. Disclaimer: Everything I'm about to say comes from a point of pure ignorance.Still battling to understand the different systems and the pros and cons of each. Anyways if I understand you correctly you are talking about the rocker looking like its actually part of the seat stay and not pivoting off it?ie: http://i.imgur.com/M7rY2Gr.jpgSomeone needs to ELI5 this for me.Explain it like I'm 5no - like the last video you posted - exactly like trek's one. pivots (well, not really, but let's call them that) all over the top linkage, but one solid chainstay piece, pivoting off the seat stay and driving downwards when the suspension compresses, with the upper rocker "chasing" it down. There needs to be a link at the top where you put "no pivot point"
Captain Fastbastard Mayhem Posted April 1, 2015 Posted April 1, 2015 https://www.youtube.com/watch?list=PL3392F0304AED1E0D&v=MvjwuynHwGIThis. SO instead of compression from both sides, one side is moving away, but the upper link is "chasing" is at a rate that is faster than the lower section can move away...
nolipoli Posted April 1, 2015 Posted April 1, 2015 burner - off topic, but on the topic of jigging and cars - 442 IRS design - have you any experience in it, and if so could you PM me? Shot. As for the build - really lekker to see hoiw it's progressing in the design phases. Any particular reason you went for a design where the compression is driven from both ends, as opposed to a full floater type design (trek etc) where the shock is driven from one end and the other end (chainstay extension) goes with it at a lower rate of movement?What I was hoping to achieve by having the shock compress at both ends is as follows: 1. Relatively long shock stroke compared to suspension travel (57mm vs. 100mm). This gives the shock better control over the suspension action. 2. The geometry of my linkages was designed to ramp up the leverage significantly which will offer a plush start and very firm finish to the suspension travel. This will resist bottoming out on bigger hits. 3. By having both bottom and top of the shock mounted to linkages instead of the frame, it avoids the requirement for more mounting plates on the front triangle, simplifying the looks as well as the manufacturing process.
nolipoli Posted April 1, 2015 Posted April 1, 2015 The jig is easy to build. I used to have a range of engineering equipment when I built cars. I can have it put together by a fellow engineer, but he's here in Cape Town. If you are really interested, I can arrange it for you. Are you planning to do the welding yourself? For me the biggest issue is time. My old man has a workshop with a manual lathe and milling machine, that I used to be quite comfortable on, and he also has a MIG and a TIG welder. My TIG welding was basic at my peak, and I am seriously concerned about whether I can actually do a decent job on this project. I suspect what I will have to do it make up the parts and then hire someone to weld them together for me. I am sure I can find a few peeps that would be interested.
nolipoli Posted April 1, 2015 Posted April 1, 2015 One more thing - That Trek "Full Floater"design is actually just a single pivot with linkages to control shock actuation. This means that the wheel path is a rigid arc around the main pivot. This does not work for me because I am running a very short chainstay for a 650b (420mm) in conjunction with a straight, uninterrupted seat tube (for when you want to jump the bike). I needed better control over where the wheel ended up.
Captain Fastbastard Mayhem Posted April 1, 2015 Posted April 1, 2015 Sweet, shot for the explanation!
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