Is this a bad design idea? or will it work fine....

Originally posted by BioMax



What needs to happen is the cantilever arm needs to be controled by something. Typically the center mount would be stationary. That would necessitate the use of a "floating" link bar (ie. a bar with heims on each end) to connect to the rear end housing. If you attach the end of the cantilever to the rear end with a stationary mount, the center mount would need to be allowed to float. Calculating out a system that follows the rearend arc while trying to keep everything in check can get interesting. Cut up some cardboard and make some "paper dolls" to see what kind of issues you might run into. The time spent will save you hours in the long run.

Ive auctually allready gone thrgouh the cutting of wood templates of exactly everything i want, and tried cycling it through that way, and i didnt encounter an issue. But im just curious as to if there is something im not factoring in on the decision......because of shear operaton alone...its going to work fine. But im curious if anyone has some preconcieved idea on what it will do in a real life situation being moving and lifting and everything.

thanks everyone for responces. The binding issues im running into are not majior or normal ones, its manily because im running the cylinders upsidedown to normal mounting procedure, and i have no way for my cylinder to affix to my frame on a heim....lol if it were that easy it wold have allready been done.

Im pretty confident that i will be ok with the design. And if in the end it dosent work out, its just the center mount, i can change that in a flash.

taylor

I've got a solid center point on my canti. I don't think it will work because, the bag will want to arc when put under load. I know that because when I started the setup in mine, we found that if there was like 40 lbs in the bag and the suspension was working, the bag would want to sissor. We added a heim on the axle side of the dogbone to the rear end and no problems since. hope that gives you a hand with your question. later!

anyone else?

i am doing one on a frame right now although i mounted my center mount solid and added another bar on the side that pushes down to atach to the rear end so that it pivots and the center bar is not attached directly to the rear end...i think that is why you would have to make the center mount pivot if you were to attach the canti arm directly to the rear end

i got this pic from pma s web site they mounted the shock like how i was talking the canti arm is not mounted directly to the rear end instead the another bar that has pivots on each end that then mounts to the rear end

hey troy, i cant quite see what what your pointing out in the pic, its alittle small...

you know of any larger pics like that?


whats your opinion on having a setup that has a pivot at every mounting location? like pictured above....and on like the one picured above?


thanks


taylor

i am not the best artist but maybe youll get what i am saying by this

The axle is guided in its motion by the link system (4 link, 3 link etc) The lever system has to be able to lift and move with the rear. They cannot both be fixed or something will break. The motion of the rear and the lift arm wont travel through the same arc. By using a fixed pivot on one, you have to use a movable pivot on the other. In the end the bag or cylinder has to be allowed to float (guided) through the range of travel of the suspension without binding. You cant rely on the bag or the cylinder to guide the suspension, or control the movement or it will prematurely fail.

RE: your first drawing:

My statics experience says that unless the forces are equal either by loading or by ratio changes, that the center link bar will be pushed with a horizontal component of force to the weaker side.

Additionally, dynamics says that the resistance of the bag to compression will exert the force sideways as well under instantaneous forces (speedbumps, rocks in the road)

That is my opinion with education in both statics and dynamics. The real world application will encounter other variables, like friction at the bushings, and torque on the bars.

i have tried a design like this pretty close on my red austin bantam truck in my profile on the front at first. it didnt work very well. taylor i would tell you to make your center pivot solid mounted. i cant imagine any reason or circumstance you would run into that you would need it to move in my honest opinion. i would not suggest it in other words. i dont care what people have done sitting still in a shop driving down the road is a whoel differnt world. just my 2 cents