Some modification of packard shutter

[Tin Can]

Among the lot of instruments we use those in our Composites Engineering manufacturing facility. Randy, you would be in heaven exploring the products being made.

I worked in Product development most of my life and automotive during all of it. First at Crane Packing in 1972 and decades for Fel Pro. Often used MTS and Instron machines. Once a million lb MTS Load Frame at Northwestern Univ. It was huge. Electro-Motive parts. We had 2 cylinders of a locomotive, operational for live testing.

While at Fel Pro we went from Studebaker engine Dynos to 6 modern cells that became obsolete long before we stopped using them. During asbestos replacement testing I was all over the place, Detroit, San Antonio, Ann Arbor. Jack Roush racing sent us lot's of engines. We often got 6 packs of Chryslers on one big skid. Then we raced the Hell out of them using tankers of special Dyno test gas that cost way more.

I really miss the roar of 6 engines all at WOT (wide open throttle) full load for 100's of hours. Racing sitting still. Eh WOT? I can't hear you... Dyno joke.

I studied the history of Dyno testing engines which is as fascinating as old photography and occurred during the same time period. Horsepower!

[Harold_4074]

If you really snap a Packard shutter (modern design, anyway) hard enough you can break the blades, usually at the lower pivot points. This from Reno at Packard Shutter Company, who graciously repaired a nearly new shutter of mine which for some reason failed at a completely different point.

The older blades are something like phenolic-paper, which can be glued, but the current ones are apparently polypropylene or nylon, neither of which are really amenable to cementing. I think that if I really wanted to exceed the factory speed, I would look to some sort of shock absorber at each end of the stroke; the momentum of those rotating blades is considerable, and the original design makes no provision for absorbing it other than be deflection of the working parts.

[Tin Can]

If you really snap a Packard shutter (modern design, anyway) hard enough you can break the blades, usually at the lower pivot points. This from Reno at Packard Shutter Company, who graciously repaired a nearly new shutter of mine which for some reason failed at a completely different point.

The older blades are something like phenolic-paper, which can be glued, but the current ones are apparently polypropylene or nylon, neither of which are really amenable to cementing. I think that if I really wanted to exceed the factory speed, I would look to some sort of shock absorber at each end of the stroke; the momentum of those rotating blades is considerable, and the original design makes no provision for absorbing it other than be deflection of the working parts.

I think you just made the old ones more desirable.

Most that I have opened have little triangular bumpers in the bottom outside corners, which are all dried up. My so slow 5" had bits of hose in those location on metal pins. I tried new hose there and I made matters worse.

1/25 th is the factory spec and one I can now achieve after my hands started squeezing better, on 3.5 inch and smaller. The 3.5" ones work real good. I have one with metal blades.

Wish I still had access to a laser cutter...

[Harold_4074]

I don't know much of the history, but I think that we use "Packard" as a sort of generic name for shutters made by different manufacturers to varying internal designs. I have one which has to be mounted with the air cylinder horizontal, since the weight of the piston (machined from solid brass) is enough to close the shutter in the absence of air pressure. I described it to Reno, who said it was definitely not a Packard Shutter Company product. (Mounted conventionally, it is a bear to focus through....)

My guess would be that the ratio of piston travel to center-of-mass blade travel would make effective damping problematic, given the confines of the case. What you would need would be some kind of frictional damping--not elastic, like rubber---to slow down the blades gradually at the ends of the stroke. Of course, this would require more piston force for a given speed, raising the stress on the drive notch and lower pivots, just as Reno described.

Also: I usually use the pin, but how do I spec that spring?

You could consider contacting Packard Shutter, sending a picture of the shutter interior and asking if the "correct" spring can be had as a repair part. Assuming, of course, that your shutter came originally from the Packard Shutter works