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Flashburnt
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3,886 Posts
Discussion Starter · #1 ·
I'm looking for links with figures, formulas, equations, or possibly a somewhat easy to use program to help me design a fairly easy yet trick rear suspension. If anyone has/knows of anything, post up here.
 

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Flashburnt
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3,886 Posts
Discussion Starter · #3 ·
Awesome! Glad to see I'm not the only one. Maybe we can make the sites/info a sticky when we get some. I'm looking to design a direct link or cantilever setup for my rear swinger, so that is where the knowledge will be aimed right now.

I'm sure Flint and Shift will pop in. Flint and all his girder-goodness.
 

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CAPTAIN AWESOME®
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30,619 Posts
Brian, i can send you my copy of Motorcycle Dynamics and you can copy whatever you need out of it. you have to be a rocket scientist and not have any life to read and understand the whole thing but it is bursting with design influences and the accompanying equations
 

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Newbie
Joined
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97 Posts
Brian, i can send you my copy of Motorcycle Dynamics and you can copy whatever you need out of it. you have to be a rocket scientist and not have any life to read and understand the whole thing but it is bursting with design influences and the accompanying equations
Can i have a copy of that also. My wife is/was an Aorespace engineer. So what i dont get she can help with. :D

Thanks, Clay
 

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GURU
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8,827 Posts
This is probably one of the most complicated topics the setup is some basic geometry but what happens at every point in the travel gets pretty complicated.

This stuff is mainly for bikes but i think their software(a version of it) is free.

http://www.bikechecker.com/

tony foale has one for 99euros.

http://www.tonyfoale.com/

I use cad software to set up everything and check movement. The basic principle is a 4 link setup just with a shock on one of those links so there are tons of car 4 link setup docs out there. here is a link with some math on 4 bar stuff and their mechanical advantage.

http://www.roymech.co.uk/Useful_Tabl.../Linkages.html

like i said the math gets pretty nasty. The basic principles you need to have down are sinusoidal equations and vectors. Knowing that force has an X and Y component and a resultant based on those. And knowing that your x and y travel around a circle differs with angle. There is also a point where your linkage becomes locked so you need to be aware of that.

If you notice factories are always changing their linkage setup and every new setup is the "best", then why keep changing it? There are pros and cons to different setups but the big thing you want is a nearly linear compression of the shock. You dont want your shock to have a lot of horizontal movement because you are wasting energy and essentially making a stiffer ride. Honda nearly solved this problem by mounting the shock to the swing arm rather than the frame. Other setups compress the shock from both sides or variations of different setups.

Ive played around with various setups for different users on here and uploaded a few vids.



This is that same setup rotated at a different point(dog bone different) to show how the system is mechanically locked.



Here is a setup i came up with on my airbike.



Here are some images ive made over time to answer various questions.



the "graphs" at the right are to show compression of the shock. You can see the first setup falls off in a nice gradual manner. the second falls off faster because its already cross the point of max vertical travel. The third reaches max travel(per input at the rear wheel) and then starts to decline. These are important to think about.

Here is another.

 

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Piston broke
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519 Posts
Shift,in the underslung shock drawing is there any reason to have the pivots triangulated rather than in a straight line? I'm designing an underslung mono for my 'Max.
 
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