How to size the correct Stop Tube
When do you need to consider using an internal stop tube?
Consider an internal tube stop when the stroke of the cylinder is 18″ or longer. The combination of the weight of the cylinder body and the force of the cylinder extending will cause stress on the rod bushing and rod seal. This will cause premature failure of the rod bushing and rod seal. This is only a general recommendation, when trying to decide if you need a stop tube for your application. NOTE: Note: the overall length of the cylinder will increase when adding an internal stop tube.
The other considerations are the cylinder bore size, the cylinder body material, and the piston rod diameter. A larger bore cylinder will weigh more that a smaller bore cylinder. An aluminum body cylinder versus a stainless steel cylinder, the stainless steel will weigh more.
If a stop tube is not right for your application, there are alternate solutions. A double piston design will add side load capacity to your pneumatic cylinder. The 2 piston seals will push radially on the cylinder body, so it will be an even force and not twisting the seals.
Another option is to use: clevis, pivots, swivels, and trunnions for the cylinder rod end and base mount. This will help with the twisting side load applied to the front cylinder seal, but is recommended to be used along with a stop tube or double-piston pneumatic cylinder.