Topics

HO Tank Car Lid


Tony Thompson
 

Claus Schlund wrote:

What Ed is trying to say is that normal atmospheric pressure is about 14.7 PSI.
Thus a PERFECT VACUUM would read at -14.7 PSI (note the minus sign).
Therefore, a "vacuum at -27psi" is not possible under any circumstance on earth

They pulled a higher vacuum with a vacuum truck. Those are usually used for sucking out clogged sewer pipes and the like and obviously exceed “full” vacuum (14.5 psig). I don’t know HOW it works, tho.

Tony Thompson




Charles Peck
 

A vacuum gauge reading minus 27 is not reading pounds per square inch.
It is reading inches of mercury that the vacuum can lift.
Chuck Peck

On Mon, Nov 23, 2020 at 5:47 PM Tony Thompson <tony@...> wrote:
Claus Schlund wrote:

What Ed is trying to say is that normal atmospheric pressure is about 14.7 PSI.
Thus a PERFECT VACUUM would read at -14.7 PSI (note the minus sign).
Therefore, a "vacuum at -27psi" is not possible under any circumstance on earth

They pulled a higher vacuum with a vacuum truck. Those are usually used for sucking out clogged sewer pipes and the like and obviously exceed “full” vacuum (14.5 psig). I don’t know HOW it works, tho.

Tony Thompson




Rufus Cone
 

The referenced youtube video misinterprets the trucks gauge (see the image at 0:43).  It reads in inches of mercury, not psi. 

With the gauge designed so that atmospheric pressure is set to read zero, a vacuum reads minus 27 inches of mercury.

Rufus Cone
Bozeman, MT


Allen Cain
 

Impressive demonstration.

If I am reading the vacuum gauge correctly it reads 15 inches of Mercury which is just over 7 PSI which is not much at all.  But spread over the entire interior service which is a lot of square inches it adds up to a lot of force.

The increase in vacuum pressure is directly related to the increase in "air" volume as the tank is emptied.

So venting a tank car filled with liquid while emptying it from the bottom valve is pretty critical.

Allen Cain


mopacfirst
 

There are formulas in ASME Section VIII of the Boiler and Pressure Vessel Code that will allow you to calculate, or at least read off a set of curves, the expected maximum external pressure a steel fabricated vessel (say, a tank car) can withstand without collapsing.  Suffice it to say that the maximum possible external pressure a vessel in free air can see is 14.7 psi absolute (psia).  This would be less, say, if you assume this tank car is on Tennessee Pass or somewhere like that.

Some of the factors in the calculation are the ratio of the wall thickness to the diameter, and any reinforcement and the distance between reinforcements.  The tank heads count.  

I think the most common way you can get a vessel like a tank car to collapse is to fill it with steam and then close the vents while it's hot.  These guys who sucked a vacuum in one with a vacuum truck were probably doing this demonstration for the purposes of showing what could happen if you didn't have a vent open, and I'd say this is not surprising, that it would collapse at -7 psig or so (about 7 or so psia).  Notice that, in the video, they taped all the couplings on their hose to prevent air from leaking inward.  My best guess is that, if you did start to drain a tank car full of oil without opening a vent, a lot of it would run out by gravity but at some point it probably would collapse before it was fully drained.

A riveted 8k or 10 tank during the period of this list could have been slightly stiffer than a modern welded one, but probably not by much.  Or maybe not.

Ron Merrick


Charles Peck
 

Now if you were to have a tank car built to the minimum required standards, you 
might be tempted to fill it full of some heavy but free flowing liquid. Something with a 
suitably low viscosity, like clipper oil.
And then, if you were to open a drain valve at the bottom of the tank, some of that 
liquid would drain out.  BUT!  What if in doing so, it sucked in some bubbles of air,
like my ketchup bottle sometimes does?  Then more such liquid could pour out the
 bottom.  And you would have a mess between the rails that your track cleaning 
car probably wouldn't be able to clean up.
BUT! If you put a hose on that drain, and ran a long hose down into a deep hole, 
like maybe the Grand Canyon,  and put a check valve on it so the bubbles couldn't 
get back up the hose, then you could maybe get yourself a mess of scrap iron out of it.
Better, if you used a sharp file to create some stress points in vulnerable places, 
you could maybe use less hose. 
Presto!  You have demonstrated why most model RR tank cars are plastic and not steel.
Chuck Peck (enjoying some wine and a few laughs)

On Mon, Nov 23, 2020 at 8:00 PM mopacfirst <ron.merrick@...> wrote:
There are formulas in ASME Section VIII of the Boiler and Pressure Vessel Code that will allow you to calculate, or at least read off a set of curves, the expected maximum external pressure a steel fabricated vessel (say, a tank car) can withstand without collapsing.  Suffice it to say that the maximum possible external pressure a vessel in free air can see is 14.7 psi absolute (psia).  This would be less, say, if you assume this tank car is on Tennessee Pass or somewhere like that.

Some of the factors in the calculation are the ratio of the wall thickness to the diameter, and any reinforcement and the distance between reinforcements.  The tank heads count.  

I think the most common way you can get a vessel like a tank car to collapse is to fill it with steam and then close the vents while it's hot.  These guys who sucked a vacuum in one with a vacuum truck were probably doing this demonstration for the purposes of showing what could happen if you didn't have a vent open, and I'd say this is not surprising, that it would collapse at -7 psig or so (about 7 or so psia).  Notice that, in the video, they taped all the couplings on their hose to prevent air from leaking inward.  My best guess is that, if you did start to drain a tank car full of oil without opening a vent, a lot of it would run out by gravity but at some point it probably would collapse before it was fully drained.

A riveted 8k or 10 tank during the period of this list could have been slightly stiffer than a modern welded one, but probably not by much.  Or maybe not.

Ron Merrick


Mark Vinski
 

At least the collapsed car with a frame could be moved to a scrapper. The frameless ones would have to be cut up on site.
Mark Vinski


Jack Mullen
 

On Mon, Nov 23, 2020 at 02:47 PM, Tony Thompson wrote:
They pulled a higher vacuum with a vacuum truck. Those are usually used for sucking out clogged sewer pipes and the like and obviously exceed “full” vacuum (14.5 psig). I don’t know HOW it works, tho.
I hope this is meant as a joke that's too subtle for me to get. There isn't any vacuum that exceeds full vacuum, which is 0 psia. No matter how you pump, you don't get less than nothing, because you can't remove more than everything.

Jack Mullen


Daniel A. Mitchell
 

Absolutely correct! Having worked on high vacuum systems I can attest to the difficulty in getting even CLOSE to a perfect vacuum (zero psi). Atmospheric pressure is usually stated as 14.7 psi (plus or minus a little due to weather). When pulling a vacuum the first 14 pounds are easy, and can be achieved with a "roughing pump” (often a sort-of an air compressor running backwards). Things like the aforementioned vacuum-trucks move a lot of air to rapidly evacuate large volumes (like a sewer), but do NOT actually pull a very high vacuum at all. Volume and pressure are NOT equivalent!

After that first 14 psi it gets VERY difficult. Elaborate machines struggle to get ever closer to the never-attained total vacuum. Drag pumps, diffusion pumps (oil or mercury), turbo pumps, cryo-pumps, ion-pumps, cold-fingers, etc. all try to get just a LITTLE closer by extracting the last few molecules of gasses from the vacuum chamber. The vacuum chamber itself (and any attached plumbing) can be baked to drive air out of the metal itself. Metals are porous. The pumps struggle against the inevitable small leaks. They may run for hours, or days, to get as low a pressure as possible … but they NEVER reach a total vacuum. Even outer space is not a total vacuum. It’s a goal that’s never quite attained.

The elusive 14.7 psi (approx.) vacuum is the best you can ever hope for, and you’ll never quite get even that.

Dan Mitchell
==========

On Nov 24, 2020, at 3:38 AM, Jack Mullen <jack.f.mullen@...> wrote:

On Mon, Nov 23, 2020 at 02:47 PM, Tony Thompson wrote:
They pulled a higher vacuum with a vacuum truck. Those are usually used for sucking out clogged sewer pipes and the like and obviously exceed “full” vacuum (14.5 psig). I don’t know HOW it works, tho.
I hope this is meant as a joke that's too subtle for me to get. There isn't any vacuum that exceeds full vacuum, which is 0 psia. No matter how you pump, you don't get less than nothing, because you can't remove more than everything.

Jack Mullen


Ray Hutchison
 

Tony, I am waiting to see your model of this puppy! 
rh


Tony Thompson
 

Ray Hutchison wrote:

Tony, I am waiting to see your model of this puppy! 

  It would certainly be an interesting challenge. Let's see, take a kit tank, heat it up until it softens -- or maybe make a new tank out of thin styrene --

Tony Thompson




Tony Thompson
 

Robert Bond wrote:

I grabbed the rod, and some .10 white plastic, and went to the kitchen. I cut a couple strips of the plastic, and fired up the oven. I placed the plastic on the rod, and let soften slowly, and once I found the right oven, (170 degs at about 10 minuntes) I was able to get a reasonably usable window insert . . .

There's your tank car collapse.

Tony Thompson




Bruce Smith
 

Folks,

Many years ago, I used a “wrecked” AC&F type 27 (IM) as a load on my Sunshine F30A. I have never been happy with that load because I wanted to portray a wrecked, burnt out tank car headed for scrap, and the soldering iron gouges just never look right. In addition, the all over rust isn’t realistic, and I’ve learned a LOT more about rusty weathering. 

Watching artistry by others with respect to wrecked cars using aluminum sheet had me thinking that I would replace part of the tank with aluminum to show the tearing rupture of the tank… but again, I worry that the rest of the tank should be deformed as well. So, the replacement of parts of the car with aluminum sheet (pie plate?) might also lend it to being crumpled, albeit from collision forces, instead of vacuum.

Regards,
Bruce 
Bruce Smith
Auburn, AL



On Nov 24, 2020, at 12:50 PM, Tony Thompson <tony@...> wrote:

Ray Hutchison wrote:

Tony, I am waiting to see your model of this puppy! 

  It would certainly be an interesting challenge. Let's see, take a kit tank, heat it up until it softens -- or maybe make a new tank out of thin styrene --

Tony Thompson





O Fenton Wells
 

Looks pretty good to me Bruce
Fenton

On Tue, Nov 24, 2020 at 2:28 PM Bruce Smith <smithbf@...> wrote:
Folks,

Many years ago, I used a “wrecked” AC&F type 27 (IM) as a load on my Sunshine F30A. I have never been happy with that load because I wanted to portray a wrecked, burnt out tank car headed for scrap, and the soldering iron gouges just never look right. In addition, the all over rust isn’t realistic, and I’ve learned a LOT more about rusty weathering. 

Watching artistry by others with respect to wrecked cars using aluminum sheet had me thinking that I would replace part of the tank with aluminum to show the tearing rupture of the tank… but again, I worry that the rest of the tank should be deformed as well. So, the replacement of parts of the car with aluminum sheet (pie plate?) might also lend it to being crumpled, albeit from collision forces, instead of vacuum.

Regards,
Bruce 
Bruce Smith
Auburn, AL



On Nov 24, 2020, at 12:50 PM, Tony Thompson <tony@...> wrote:

Ray Hutchison wrote:

Tony, I am waiting to see your model of this puppy! 

  It would certainly be an interesting challenge. Let's see, take a kit tank, heat it up until it softens -- or maybe make a new tank out of thin styrene --

Tony Thompson






--
Fenton Wells
250 Frye Rd
Pinehurst NC 28374
910-420-8106
srrfan1401@...


Robert Heninger
 

Bruce, 

I would think a tank car with much more damage than that would be scrapped on site, and would not be economically or even feasibly repairable, even given your mid-1944 timeframe. But I could be wrong. What (prototype) damaged tank car bodies I have seen as loads looked almost intact, as I recall.

Regards,
Bob Heninger 
Minot, ND


Garth Groff and Sally Sanford
 

Bruce,

An idea for you. When we have train shows again, look for an old Athearn/Globe, Thomas or Mantua steel-bodied tank. Or if you're really flush with cash, find a beat-up brass model. Then put some realistic dings into it with a tack hammer. As a bonus, you will get an underframe that probably isn't worth saving (especially the Mantua one-piece zamak casting made to fit only their weird hook-and-loop couplers). It might make a good gondola load.

I'll probably hate myself in the morning for suggesting this. I really enjoy rescuing those old metal tanks, and have saved several. They were in some ways more accurate models than their plastic replacements of the 1960s from Varney, LifeLike, Walthers, and yes, Athearn.

Yours Aye,


Garth Groff  🦆



On Tue, Nov 24, 2020 at 2:28 PM Bruce Smith <smithbf@...> wrote:
Folks,

Many years ago, I used a “wrecked” AC&F type 27 (IM) as a load on my Sunshine F30A. I have never been happy with that load because I wanted to portray a wrecked, burnt out tank car headed for scrap, and the soldering iron gouges just never look right. In addition, the all over rust isn’t realistic, and I’ve learned a LOT more about rusty weathering. 

Watching artistry by others with respect to wrecked cars using aluminum sheet had me thinking that I would replace part of the tank with aluminum to show the tearing rupture of the tank… but again, I worry that the rest of the tank should be deformed as well. So, the replacement of parts of the car with aluminum sheet (pie plate?) might also lend it to being crumpled, albeit from collision forces, instead of vacuum.

Regards,
Bruce 
Bruce Smith
Auburn, AL



On Nov 24, 2020, at 12:50 PM, Tony Thompson <tony@...> wrote:

Ray Hutchison wrote:

Tony, I am waiting to see your model of this puppy! 

  It would certainly be an interesting challenge. Let's see, take a kit tank, heat it up until it softens -- or maybe make a new tank out of thin styrene --

Tony Thompson





Bruce Smith
 

Bob,

Excellent point, however, the PRR’s Atglen and Susquehanna (A&S) and Columbia and Port Deposit (C&PD) branches, which I model, have the odd problem of being wilderness lines for much of their length, often with highly restricted access to the ROWs, and so much of the wreck cleanup that I have seen has involved shipping for scrapping. But now, you have me pondering, since I am not modeling the actual wreck, but rather the results, if a gondola full of what appear to be cut up tank car pieces wouldn’t be more appropriate…

Regards,
Bruce

On Nov 24, 2020, at 1:44 PM, Robert Heninger <gn2059@...> wrote:

Bruce, 

I would think a tank car with much more damage than that would be scrapped on site, and would not be economically or even feasibly repairable, even given your mid-1944 timeframe. But I could be wrong. What (prototype) damaged tank car bodies I have seen as loads looked almost intact, as I recall.

Regards,
Bob Heninger 
Minot, ND


Tony Thompson
 

Garth Groff wrote:

I'll probably hate myself in the morning for suggesting this. I really enjoy rescuing those old metal tanks, and have saved several. They were in some ways more accurate models than their plastic replacements of the 1960s from Varney, LifeLike, Walthers, and yes, Athearn.

Having done some of those same restorations myself, Garth, I entirely agree with you.

Tony Thompson