Counterweights suspended or on rails

[Raidzero]

Hello,

I have a question for mechanical engineers out there. While being one myself, I did not work in this field for 20 years, and I forgot all the formulas :)
The problem I have: a horizontal beam is attached to a pair of vertical rubber conveyor belts, one on each end of the beam. The beam has to move up and down. Since it's pretty heavy, there are some counterweights attached to the belts as well.
Now, the question is: would it be OK to use have the beam on one side of the belt and the counterweight hanging on the other side, or have the counterweight on a rail that only allows it to move up and down, and never sideways?
I believe that having the counterweights move freely, not on a rail, simplifies the design, the only concern is them moving sideways when the beam decelerates because of elasticity in the conveyor belt.
The beam has about 30 pounds and has to travel for about 8 feet. The two counterweights are about 15 pounds each.
Thank you.

 

[Mech_Engineer]

There's no problem with constraining the system to only the degrees of freedom you desire. It makes good engineering sense to do so.

 

[Raidzero]

That's what I wanted to know, thank you very much.