Pneumatic bifold door cylinder help for restored trolley car.

[Trolley93]

We have come a long way restoring our 1926 St Louis Car Company trolley car and one of the things we still need to do is to come up with the proper pneumatic cylinders to make our bifold doors/steps work. (we haven't built the steps yet, but when each pair of bifold doors open the step comes down, when the doors close the step goes up). I see different cylinders on ebay that look capable, and are very reasonable in price that I think would easily turn our door support rods, and then I see company websites with similar cylinders that cost hundreds more (we'd be paying for the technical info if we bought them there...) Not knowing for sure just what strength we need to make the doors work as they should, has been a recent hurdle we have yet to clear. Figure this would be an easy question for a group that works on buses.

I am attaching pictures of what I believe are original sized pneumatic units in an original car of similar age. Also attaching pictures of our doors. There are two interior cabinets above the doors one for each bifold door and its cylinder. The door rod for each of the two bifold door sections comes up into the base of the cabinet where it would hook up to an arm attached to each cylinder. Turning the cylinder operates the door.

Any help / suggestions / specs for modern cylinders that would do the job would be appreciated.

[dan-fox]

Wow! That's a genuinely new one on us, as you might conclude from the crickets. Most folk here opt for removing the pneumatic doors entirely.

I might suggest trying a trolley museum. My favorite is the National Capital Trolley Museum (www.dctrolley.org), but that's just because it's 15 minutes from my house. Googling "trolley museum" brings up more stuff than I thought possible.

Good luck! And, if you have a website or some pictures to share, we'd love to see them.

[family wagon]

I love how that cylinder is plumbed with little tiny elbows and unions and stuff. Things are so much easier these days with nylon air brake tubing instead.

So the door is operating by applying a torque on the bar that looks gray or maybe a baby blue color in the fourth picture? The arm must belong in, but is absent from, the third picture.

Not being a pneumatics engineer, but having stayed at Holiday Inn Express once , I'd suggest doing some experiments. Install the arm on that rod and measure how much force is required to operate the door -- attach one end of a fish scale to the arm and pull the other end by hand. Note the highest reading on the scale. If for example it peaked at 45 pounds, and if your air supply is going to run 90 PSI then as a starting point you might try finding a ram with a half-square-inch cross section to operate it (90 pounds/square inch times 0.5 square inch = 45 pounds).

Alternatively, choose some arbitrary ram and stick it in there. Operate it with shop air at a low pressure and test whether it moves the door with acceptable speed. Adjust air pressure up or down until you like its performance. When you find a good pressure to use on whatever diameter ram you had on hand, you can then re-proportion it to figure out what ram diameter would be best for whatever air pressure your trolley will run. Then go shopping for a ram with the right diameter and travel.