Page History

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First, it is necessary to determine an appropriate COTS solution for the piston. Due to timeline constraints associated with the difficult task of engineering base plates (most notably, all of the required seals), it is logical to take an existing piston and modify it to meet our needs (i.e. changing the throw on the piston, making mass saving cuts, etc). We recognized from the outset that we might not be able to find a piston that meets the previously selected 0.5 in bore diameter. In this investigation, I looked at pistons between 0.5in and ~1 in bore diameter, with 1in being what I previously mentioned as a good option.

Solution No. 1: 1691T104 

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• • Rod end is internally threaded. We'd be making a new rod anyways, but there's always a question of compatibility...
  • Different port size than our current piston. Not a huge issue because we'd probably redesign our actuation system anyways.
  • Only two holes for mounting on each base plate–poor load distribution
  • Not actually a problem, but its half the size of the desired bore diameter. We still have a good factor of safety on this diameter.
    

This piston has 4 inches of throw... Assuming that everything but the bore and the tie rods are identical, it may make most sense to actually purchase a piston with much less throw, such as the 1691T69. 

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• • Again, need to machine a new bore due to increased necessary throw length as well as bore material (we want to avoid having a steel pressure vessel).
  • Correspondingly need to machine a new rod and purchase new tie rods.
  • Not actually a problem, but its way smaller diameter than the desired 1".

Again, it may make sense to go with a similar piston with less stroke length. 

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• • The square end plates fit the form factor we have already used.
  • Stroke length is exactly what we need, so it is a complete COTS solution that requires no adjustment. We could make mass saving cuts, change rod material (which is currently 303 stainless steel).
  • It's port inlet is 1/8 NPT, which for what it's worth, we already have compatible fittings for 1/8 NPT. This shouldn't be a driving factor, just a perk.
  • Saves a ton of mass due to being a reduced 3/4" bore diameter, which is pretty close to the "optimal" 1in that I previously mentioned.

Solution No. 5: 6453K153

Some disadvantages are:

• • It probably won't save us that much mass.

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This piston has a 1 1/8" bore diameter made from aluminum with a 5.5" throw length. Some notable advantages of this option are:

• • Close to the "optimal" piston diameter that I previously mentioned.
  • The square end plates fit the form factor we have already used.
  • Stroke length is exactly what we need, so it is a complete COTS solution that requires no adjustment. We could make mass saving cuts, change rod material (which is currently 303 stainless steel)

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• • .

Selected Piston Dimensions and Improvements

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Given a 4.5" coupling section, this gives us a 1" margin on separation distance.

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