[WJM]

Originally Posted by jedwards

It's always nice to hear more people wanting our stuff.

Now, just to clarify one misconception:

The "Coleman" box (SC-C925) was never discontinued by the manufacturer. In fact not only does Global Cooling still sell the unit but even Coleman Japan still sells it.

Ah yes, never claimed that Twinbird stopped making them; it's just that Japan is one of the least 'overseas-customer-friendly' countries to deal with, even excluding the issue of shipping cost (which, by itself, is adding insult to injury....even ordering rare/exotic offroad literature is a pest). Never got a good insight in the Coleman conglomerate/policies either....already send a note to Coleman Holland, to see if they might have had some of these boxes, if only for testing/sampling....it only takes one freak high in the foodchain to get them across the border/pond....) Btw, perhaps you should interpret my earlier 'heartbroken' also in particular Dutch context, having missed such a nice bargain....) (even though shipping USA->NL wouldn't have been cheap either (not since USPS cancelled the option economy/sea) (my usual approach, trying to find exotic hardware only as used/surplus (gotta love the military btw....), would fail in this case anyway, just because there never were any large-scale sales, not even for more than a few years, and those who bought one knew and know darn well what they have, and probably will even clutch them with their nails when entering the grave....)

The main reason for Coleman US to stop selling, was not because of slow sales. Shortly after they took their first delivery of Stirling Coolboxes, their parent company, Sunbeam, declared bankruptcy. The new management decided not to continue the project for "internal" reasons. As you know the demand for the SC-C925 has never really fallen since it release and we are always looking for distribution outlets in new markets.

Okay, good to hear....but I also must conclude that there is no active (consumer) marketing/distribution in Holland, of all places/subsidiairies, either? Nor in any European country? (there isn't much of that for most of the compressor boxes in NL either, only in the truck-segment (and even those for decades sourced abroad, while on international trips)....market is completely different in Germany/Italy)

Now, to answer your questions:

1) As I have mentioned in earlier posts, the angular restriction is a function of the CO2 thermosiphon. This device is used to transport heat from the cold chamber and is completely independant of the FPSC (Free-Piston Stirling Cooler). THe two units are simply 'bolted' together. The FPSC itself couldn't care less what angle it is running. Horizontal, vertical, inverted or anywhere in between. The Stirling will never "quit running" even if the cooler is upside down but that is the crux of the problem. Without a load on the FPSC (remember that the thermosiphon is what tranports the heat from the chamber to the FPSC) the temperature on the cold head will plummet to as low as -100 deg C. This can cause the CO2 in the thermosiphon the freeze solid and block the flow of heat to the cold head, for a while, even if you turn the cooler back over. Short duration (a few minutes) inversion is unlikely to cause noticable problems and off camber operation will only decrease the amount of heat being transported to the FPSC decreasing efficiency. The flow reduction in off camber situations is because of weakened forces (rememeber your trigonmetry) drawing the more dense, liquid, CO2 to its proper location. Once the unit is righted the CO2 plug will eventually 'defrost' and the untit will work as if nothing had happened. In extreme instances, you may have to remove power to the cooler for a short time to allow the cold head of the FPSC to 'warm' up to more reasonable temperatures to encourage the frozen CO2 to defrost. Again, as I mentioned in earlier posts, in some orientations, the thermosiphon will operate, with no degradation at all, even when the unit is rotated 90 degrees (mechanical side up, with the door out like an upright refrigerator).

Okay, temporarily suspended cooling isn't bad at all....only relevant worst-case offroad scenario left is tipping over sideways, without having eutectic elements to take over the cooling process (doesn't have to be serious damage either, sliding slowly into a ditch/rut and hours of extraction attempts is enough to kill some good food....)

2) As for vibration, the FPSC itself is virtually immune to the effect of external vibration. a close cousin to the unit in the SC-C925 was the only cooling technology to ever be operational during the launch of the Space Shuttle.

Just for fun, something I learned only recently: the Kissman TR825(EN) box (their oldest design, starting in 1964(!!), with proprietary/half-hermetic compressor was the only one ever *onboard* of a shuttle....being oilless, and orientation-independant, it was the only one NASA could use (at least at that time, not sure exactly which year(s) this was)....and this gravity-deprived application would be a no-go for a gravity-operating Twinbird too of course....)

Unless the FPSC in the SC-C925 is subjected to a continuous and high amplitude, steady, axial vibration of 79.1Hz

Good to know, for any future problem-analysis....) (I believe there are very basic (mechanical) instruments that can detect the typical/main frequency of a vibration, so this would even be rather easy trouble-shooting....) (or even dash-mounted, when rattling over washboard desert roads....adjust vehicle speed accordingly....)

it will not likely even have to throttle back from full capacity (assuming that is has to operate there anyway) to minmize the slight risk of contacting its internal bump-stops. In fact steady random vibration will enhance the performance of the thermosiphon by 'jiggling' the liquid CO2 down the slope to where it can pick up more heat.

In the earlier context of compressor fridges and off-camber sensitivity (btw, they completely fail/break/seize-up in such a scenario, due to lack of oil/cooling, overheating, more than just quit functioning!), I had already pondered about some exotic overengineered cardanic suspension, at least for the compressor itself (of course, that would require flexible hoses too)....) Btw, checking your previously posted pricelist: there is a rather steep price-jump for the most expensive (deepest-freezing/-70C) 25L box ULH-025, between 1 unit and 6 units....just because there is hardly any stock of those, and production being so much more efficient with 6 than with 1? (perhaps it is in the highest-end VIP-panels too?)