LONG tube for a Packard ?

[ridax]

I have a large 4"-opening Packard shutter that works great, and I'm going to purchase a really long rubber tubing for it. But high quality silicone rubber tube is not very cheap, and besides I have to buy oversears and pay for the shipment too as I was unable to find a black one locally. And therefore I guess I'd better not buy any more then I could actually use. So, my question is,

how long a tube is still OK to reliably open and close a Packard that size? What about a 100 feet? 200 feet? even more...? Any practical experience is welcome.

(I don't want to switch to an electrical release type shutter.)

Thanks!

 

[michaelbsc]

I don\'t have a quantitative answer, but I can tell you that as the tube gets longer you will begin to have trouble compressing enough air with a small bulb to raise the pressure enough to operate the shutter.



You need X psi/kPa on the base of the operating cylinder to push the shutter. Your bulb has a fixed volume that you will \"compress away\" when you squeeze the bulb. If the volume inside the tube is substantially larger than the volume you compress away you won\'t get much pressure increase.



MB

 

[richard ide]

From a practical standpoint; I do not think that a rubber tube is suitable. When squeezing the bulb, there will be a lot of air volume used up in expansion of the tube to build up pressure. I think you would be far better served with a piece of nylon or polyethylene tube which would eliminate this problem. The tubing would be far more economical as well.

 

[michaelbsc]

This is a good idea. Poly tube is cheap and availabe most places, but not sure about the OP's location.

And one could use a compression bellows like comes with an air mattress to get more volume in the bulb end. Then a small section of rubber hose at the end with the Packard to form a light trap would be all that is required.

 

[ridax]

Any PRACTICAL experience is still welcome.

 

[michaelbsc]

Any PRACTICAL experience is still welcome.

Well, I have a lot of practical experience with pneumatic control lines, some hundreds of meters long. But we usually use either copper tubing or stainless steel depending on location to corrosives. If it's a fixed installation, then metal tube will be far superior. It you want to take it places metal tube will be a real PITA. And my Packard has only about 4 feet or rubber hose.

I'm not sure where you are, but I'd try a 100 foot spool of Poly tubing with a bellows like this Dead Link Removed instead of a squeeze bulb.

 

[jonw]

For tubing, I have used fuel line or wiper blade tubing you can get at an auto parts store. It works fine. Jon

 

[ridax]

Well, after several day's research I see I have to buy a lot of different things and spend a lot of time to try them all in different combinations as the problem seems to be somewhat more complicated then I initially hoped.... too many variables at work!

Many thanks for the pump link (I didn't know a footpump was able to suck the air back, too, and so was about to ignore them all!) and also for the different tubing ideas. May be I'd also try an old almost perfectly air-tight high-polished glass-and-stainless-steel medical syringe instead of the standard Packard piston....

Anyway, I'll post my results later - but no faster then in a couple of months I guess! Going to call and visit a lot of local stores and make purchases online and wait for the parcels to get to my place and etc., and etc....

Just one more preliminary question remains; should I try a tube somewhat thinner than the standard Packard one? The less the inside diameter, the less volume I have to pump into the tube but if it's too small it's too hard to pump the air through... what could be a possible optimum for the diameter?

Again, many thanks!

 

[michaelbsc]

Well, after several day's research I see I have to buy a lot of different things and spend a lot of time to try them all in different combinations as the problem seems to be somewhat more complicated then I initially hoped.... too many variables at work!

Many thanks for the pump link (I didn't know a footpump was able to suck the air back, too, and so was about to ignore them all!) and also for the different tubing ideas. May be I'd also try an old almost perfectly air-tight high-polished glass-and-stainless-steel medical syringe instead of the standard Packard piston....

Anyway, I'll post my results later - but no faster then in a couple of months I guess! Going to call and visit a lot of local stores and make purchases online and wait for the parcels to get to my place and etc., and etc....

Just one more preliminary question remains; should I try a tube somewhat thinner than the standard Packard one? The less the inside diameter, the less volume I have to pump into the tube but if it's too small it's too hard to pump the air through... what could be a possible optimum for the diameter?

Again, many thanks!

I can't say for sure, but I expect 1/4 inch I about the best bet.

1/8 inch may take too long to vent to relieve pressure on the operating cylinder.

But truthfully you'll have to experiment. Even 1/4 may be too small. But perhaps not.

MB

 

[ridax]

Thank you!

 

[ridax]

Success Report: -

The shutter: 4 inch opening (7.5 inch housing) #6 Packard.

The rubber bulb: total inside volume = 40 ml (it is for a blood pressure measuring device, and I guess it is smaller than the genuine Packard one). Price: US$ 3.00.

The tubing: 5 mm inside diameter, 7 mm outside diameter, 1 mm wall thickness black silicone rubber. Price (from a medical supplier): US$ 2.68 per meter (= US$ 0.82 per foot).

Tubing length: 46 meters (151 feet).

Tube inside volume = 900 ml (yes 22.5 times the volume of the bulb - which of course does not give out ALL the air when pressed!).

THE PACKARD WORKS.

In the BULB mode, it opens and closes perfectly (though somewhat slower then via the standard 4 feet tubing).

The shutter's instantaneous mode is not available as it requires MUCH more pressure. With the instantaneous mode pin inserted, the shutter just works the same way as on "B". That suits me, as I don't want short exposures usually.


So, glory to the 19th century engineering masterpiece named Packard. No messing with batteries needed! I only wish my computer was THAT reliable....


P.S.: Tried the Intex® Bellows Air Pump (see the e-bay link above). Surely a real pump should work.... but this Chinese beach toy does NOT. To close the Packard, I had to take the would-be footpump (set to deflating) in both hands and pull it really hard and fast. The usual rubber bulb is much much better....

 

[michaelbsc]

Woo-Hoo!

Good report. I was actually wondering about this recently.

Thanks for the details, too.

Michael

 

[ridax]

I forgot to mention I'm also able to operate the 46-meters-far-away Packard comfortably enough without any bulb at all, by just putting the tube end into my mouth. And no, I am not a diver nor an opera singer - nothing above average really....