a question about suspension design
 

Now i was thinking, this'll probably end up with a million reasons why it wouldn't work, but what if you had a rear suspension design that pushed on the shock from both sides? Would that be feasable?

Wouldn't do a thing.

Yes it would. It would push on the shock from both sides. I'm so sick of you guys that know it all.............I'm going camping!:D

That it would but the benefits of suspension would be null and void. Unless the suspension design is like a linkage actuaded design like Giant's VT series was.

i ask because i had an idea for a suspension design floating around in my head and i was doing it with the shock being pushed on from one side and i realized it go either way, my design i have is sort of rube goldberg-esque but i think it has possibilities, I'll try to get a scan of one of philosophy class notebook renderings

Even if it would work, there would be a hideous amount of chain growth.

All shocks get pushed on from both sides. There's a force being applied to one end, and an opposing force on the other end. If one of those forces is missing, it's because your shock has nothing attached to it at one end. Now, what I think you really mean is that both ends are attached to parts of the suspension that pivot, perhaps a 5-bar linkage of some sort? The shock would act as a loaded frame member, or it could be leveraged by two separate arms or walking beams. I can see something like a three-shock system, where twin shocks [or one spring and one damper, or two dampers] above the rear axles compress, allowing a scissor-action on a third shock in front of the seat tube or whatever you would use for a pivot point. This abomination would give that third shock the squeeze for sure. Christ, that's ****ing ugly.

If all else fails (or better yet, as a starting point), use a free body diagram. I for one, can't figure out quite what you're talking about, but it sounds to my slightly (or seriously) inebriated mind that you're suggesting a linkage that connects to both ends of the shock simultaneously, and I'm not seeing something feasible in my mind's eye. How about a sketch?

ok, it's about time to post a desgin sketch it seems none of you can read my mind, darn you all

I think I might have an inkling of what you are getting at, but I could be way off base. The first attempt at suspension on a bicycle I ever saw was on a BMX bike in the early '70s. It compressed the shock 'at both ends' in that it basically put the pivot in the bottom bracket and had a motorcycle shock between the seat tube and the head tube as the top tube. Very inefficient - - every stroke of the crank would have compressed the frame. Post your design sketches though . . . I'm always interested in seeing new (or creatively recycled) ideas.

this is what i have in mind.

kind of a rough sketch, should show the basic functioning of the design

Very interesting. It shows the potential to let the shock 'float' inside the frame and give a lot of movement with a short stroke. I have two reservations about the design: the leverage ratio on a short shock; and it looks like the wheelbase may actually shorten as the suspension cycles through its travel.

Have you tried a cardboard mockup yet to check the rear wheel path? Use some chipboard and put a paper fasterner (or paper brad) at each pivot. Pin the 'frame to a cork board and cycle the design thru its travel and see if it acts the way you want it to.

Also, be sure to get the conversation going in the framebuilding forum. There's bound to be a lot of experience over there that can give you good pointers.

I'm not positive, but I think it has too much freedom so that the suspension could move without compressing the shock. Try the cardboard mockup, though. I know that Santa Cruz, and probably other companies do the same thing.

my original design was the same as posted except with out the linkage from the upper arm in the rear to the shock. I just saw that making a sketch and wondered if it would work, I will make a couple cardboard mock ups of both and report back tell ya'll whats up

Looks to me as though the scissor action of the design would slack the chain, If I'm getting the design right. Course I could be wrong!;)

draw it up in Linage www.bikechecker.com and let us know how it goes

that initially looks like the shock would just move forward when the motion starts, but that might just be crazy enough to work...if you make a rough free body diagram of the system it seems to work out- the forces are definately opposing on either end of the shock. the angles are a little goofy on that bottom section probably, which messes with ur head i think.

what if the shock was somehow fixed in place?

Just my $.02! i could be miles away though!

do you mean like fixed but still have push from both sides
my initial design was the same except onlf pushing from one side

yeah like have it mounted there, doubt that would work though

I think it would work like it is.

i had to do some redesigning on it, after making a cardboard mock up the scissor action in the front severly limited travel so I'll post my new design soon