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What’s the REAL minimum radius of locomotives and rolling stock?

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Posted by ricktrains4824 on Monday, February 26, 2018 10:11 PM

gdelmoro

Now here are some impressive 18” curves 

https://m.youtube.com/watch?v=QeyaV_ubu7Q

 

This guy knows how to have fun.

Now if he can just make his little people not suffer from so much motion sickness while commuting to their jobs.... Laugh

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Posted by DigitalGriffin on Tuesday, February 27, 2018 3:52 PM

I can get Athearn Heavyweights and Bachmann Heavyweights to run R18's all day and night as long as I'm not balls out on the throttle.

Don - Specializing in layout DC->DCC conversions

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Posted by rrinker on Tuesday, February 27, 2018 7:16 PM

ricktrains4824

 

 
gdelmoro

Now here are some impressive 18” curves 

https://m.youtube.com/watch?v=QeyaV_ubu7Q

 

 

 

This guy knows how to have fun.

Now if he can just make his little people not suffer from so much motion sickness while commuting to their jobs.... Laugh

 

After watching a few of the videos that come up as auto play after that one, I can't believe so many people thing the stuff they show as a 'problem' would have ever worked. One guy has 18" radius curves and turns back on itself in a full S curve and wonders why a long bulkhead flat is pushed right off the rails. And another is sub-18" radius, or at least it looks that way, and the guy wonders why his diesels wouldn't make it. I realize everyone starts somewhere but even most beginner books tell you not to form S curves.

                                     --Randy

 


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Posted by gdelmoro on Wednesday, February 28, 2018 5:57 AM

rrinker

 

 
ricktrains4824

 

 
gdelmoro

Now here are some impressive 18” curves 

https://m.youtube.com/watch?v=QeyaV_ubu7Q

 

 

 

This guy knows how to have fun.

Now if he can just make his little people not suffer from so much motion sickness while commuting to their jobs.... Laugh

 

 

 

After watching a few of the videos that come up as auto play after that one, I can't believe so many people thing the stuff they show as a 'problem' would have ever worked. One guy has 18" radius curves and turns back on itself in a full S curve and wonders why a long bulkhead flat is pushed right off the rails. And another is sub-18" radius, or at least it looks that way, and the guy wonders why his diesels wouldn't make it. I realize everyone starts somewhere but even most beginner books tell you not to form S curves.

                                     --Randy

 

 

I would agree, but I still don’t understand how the trains in the first video I posted (the one where the track is all bent and deformed) and the last (where there are about 5 S curves in a row) don’t derail.

It kind of goes against everything we know.

Gary

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Posted by rrinker on Wednesday, February 28, 2018 12:24 PM

I can;t imagine those are typical Walther 85 foot passenger cars in the one where each piece of track alternates direction. The standard couplers wouldn;t have that much swing. They must have extra long shank couplers applied. They also seem shorter than 85 foot card.

                               --Randy


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Posted by gdelmoro on Wednesday, February 28, 2018 4:26 PM

rrinker

I can;t imagine those are typical Walther 85 foot passenger cars in the one where each piece of track alternates direction. The standard couplers wouldn;t have that much swing. They must have extra long shank couplers applied. They also seem shorter than 85 foot card.

                               --Randy

 

Well that would explain the 18” S curves. But still don’t understand the horrible track that didn’t cause derailments. 

 

Gary

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Posted by rrinker on Wednesday, February 28, 2018 5:03 PM

 That one was far less horrible than it looked, AND the trainw as going pretty slow. And it never said how many takes that was to get the whole video with no derailments. Those videos of real trains rocking like they are about to fall over? They DO derail at times. Or get stuck one way or another. I happened to witness it happen once, as the REALLY bad siding sunk into the dirt far enough to tip the cars being shoved back in right over to lean on the cars left standing on the main. Both sets of cars were stuck, crew couldn;t move anything, so (the train was operated with a loco at each end since there were no turning facilities and precious few runarounds) they climbed in to the loco that faced back to the terminal end of the run and motored off, returning the next day with a couple of cranes to life the cars upright and get the train unstuck.

                                        --Randy

 


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Posted by gdelmoro on Wednesday, February 28, 2018 6:24 PM

rrinker

 That one was far less horrible than it looked, AND the trainw as going pretty slow. And it never said how many takes that was to get the whole video with no derailments. Those videos of real trains rocking like they are about to fall over? They DO derail at times. Or get stuck one way or another. I happened to witness it happen once, as the REALLY bad siding sunk into the dirt far enough to tip the cars being shoved back in right over to lean on the cars left standing on the main. Both sets of cars were stuck, crew couldn;t move anything, so (the train was operated with a loco at each end since there were no turning facilities and precious few runarounds) they climbed in to the loco that faced back to the terminal end of the run and motored off, returning the next day with a couple of cranes to life the cars upright and get the train unstuck.

                                        --Randy

 

 

Ah so photoshop and editing, that makes more sense. As you know I’ve had to correct very slight humps and off level track to prevent derails. This video mad me mad!  Angry  Couldn’t understand how such horrible trackwork could run trains :) 

Gary

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Posted by rrinker on Thursday, March 1, 2018 11:44 AM

But it did run trains - just not likely reliably. It's all in the way you play the physics. A hump would eb bad, especially with a 6 axle loco - the outboard wheel will end up with the flanges compeltely above the wheels. IF it comes down perfectly straight, it will land between the wheels - heck I took some train set level Tyco stuff and made it jump a sizable gap once - as in, the track ramped up and made a jump. Sometimes it actually landed with both trucks on the rails. The dip is a little more forgiving - the CENTER axle may end up suspended above the rails, but the lead and trailign axles will both be on the rails and it's nearly impossible for the center axle to not pick up the rails again. At least on straight track.The limit is, it can;t dip down so much that the lead axle going into the dip tilts the truck so much the trailing axle rubs the frame, or it jams the drive mechanism. Rolling stock set up for 3 point suspension can handle it, one truck can swivel and tilt, the other truck can swivel but generally not tilt. When the free motion truck rolls through, it can tilt to the side but not tip the whole car, when the other truck rolsl through, the car tips but now the other truck is past the bad section and on level track so the carbody tilts around that truck which stays firmly planted.

 Where you can;t have dips and humps is where the wheel HAS to stay within the track guage, like at turnout frogs. If the wheel is lifted there, there's nothing else to guide it, and it just skips over the frog and derails. Or curves. You can't have the lead axle lifted to the flanges are above the railhead and expect it to follow a curve, especially a tight radius curve. Specifically created sloppy looking trackwork can work, it just has to be in cherry picked locations. Take, say, a length of flex track and puut a slight vertical kink right in the middle, but fasten the entire thing so that it is dead nuts straight, not the slightest wiggle. At least 9 times out of 10, most locos will handle it at anything short of warp speed. But curve one end, and 9 times out of 10, when a loco heads from the straight towards the curve, it will derail at that vertical hump. Going from the curve into the straight part? Probably not as much.

 The best thing to do is always make sure you don't have such dips, humps, and kinks. That's the only way to be sure. Most of the time, the human eye is good enough to see this, combined with the sense of touch - you should be able to run your finger of rail joints and not worry about snagging and slicing yourself open. I always sight down along the track looking for unintended wiggles. I also have some trucks fitted with the same metal wheels I used on most all of my rollin stock that I both roll slowly while pressing, feeling for unwanted sharp clicks at jints, and deliberately twist, trying to catch the flanges on solder joints or misalinged rails. I also fling this truck through at warp speed. And run some locos as I go - part of the reason my progress in building is so slow, as I go I hook power up and start running trains to make sure the completed track is working. They I start running trains instead of building more layout.

                                          --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by railandsail on Thursday, March 8, 2018 4:22 PM

rrinker
...excerpt

On my old layout, it's a good thing I tested first. Walthers 85 foot cars would not pass one another when the inner radius was 30" and the outher was 32". I had to open the spacing on the curves to allow them to work. If there are problems at 30 and 32, expecting them to work on 18 is IMO unreasonable.

Just reading thru this subject thread with the idea of posting some photos and experiments I made recently.

If you had opened up the CL to CL distance from 2" to 2.5" you would have no side swaping of those cars. Here is 31" outer radius and 28.5" inner radius.

Santa Fe 85 footers on 31", 28.5". & 24" Radius

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Posted by railandsail on Thursday, March 8, 2018 4:31 PM

Here are some PRR passenger cars on those 31" and 28.5" curves

 

and a GG1 with those PRR cars

Those outer pencil lines are 1" from the centerlines of the tracks.

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Posted by railandsail on Thursday, March 8, 2018 4:39 PM

BRAKIE

Everybody isn't lucky to have a full basement for a layout nor the funds to build a special layout building or join a super nice club with a super layout. These modelers make do on what the space allows.

hear hear, I suspect a whole lot of modelers don't have that space for expansive curves,...as nice as it would be

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Posted by railandsail on Thursday, March 8, 2018 4:45 PM

rrinker

I didn't go back and update the track plan, so I don't knoww aht I ended up using. There are some shots on my web site of the old layout, all the way at the bottom, where you cna see the center spacing widen out for the curves. It was enough to clear the actual rolling stock that was going to run - I tried lots of combos until I found the absolute worst case - one of them was one of those huge hi-cube cars, the wheels are well set back on those so they have a huge overhang.

 Best advice I can say is to mock it up and try it - either tack some flex with pins, or print full size if using CAD and set the cars on - I pinned down some actual track and tried various combinations of inside car overtaking the outside car and outside car overtaking the inside car, lining up the worse inside overhang with the worst outside overhang, etc. Was it an extra 1/2", for a 2.5" center spacing? Or was it an extra 3/4"? I don't remember, that was 14 years ago. I know it worked - never had an issue no matter what was run, including some Walthers cars purchased AFTER the testing was done and track in place. I'd think at 30" radius for the inner helix track I wouldn't go below 32.5" on the outer track. But agian, test it with what you intend to run. I had no locos with excessive overhang like a Big Boy or anything so i didn't test locos. The various long cars were worse on overhang than the biggest loco, a 4-8-4.

                                      --Randy

 

What I just found in my testing of long cars and steam locos is that the rear cab portion of the big articulated locos are the worst offenders. I have some photos I will post

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Posted by railandsail on Thursday, March 8, 2018 8:10 PM

Long Passenger Cars & the GG1

I did some testing out on my 'outdoor test bench' . As I have mentioned before I feel I can easily fit a helix into my plans that will have 2 parallel tracks,...
Outer radius 31 inches
Inner radius 28.5 inches

I decided to glue some track down on my 'bench' in those 2 dimensions. I chose the 2.5" between tracks dimension after reading a great number of postings indicating that this seems to be adequate for basic curved tracks at these sort of radiuses.
So here are my 2 tracks that also have penciled in lines located 1" outboard of them (1" either side of the track's centerline)

 

 

That is a newer Walthers 85' heavyweight passenger car on the inner track. It's obivious that its forward end is just shy of that 1" clearance from the C/L.

What is not so obivious is how much does the center of this car project from the C/L of the track. Regretable my camera angle (too close to subject) hides this detail. Let me say that it appears as though the center of this long passenger car requires a FULL 1" clearance on its inboard side on this 28.5 radius curve.

How about two of those passenger cars passing one another on my helix. No problem according to this photo. )and here you can see the center overhang of that upper car barely touches the 1" clearance line at its inboard side)

 

 

 

Since  I'm dealing with PRR passenger cars here. i wanted to see if a GG1 could get by, (an IHC one i have).

 

This photo would appear to have everything OK,...but as it turns out there is considerable 'play' in its trucks that allow it to extend past that 1" clearance line. From these 2 photos we can tell that this loco requires at least 1.25" clearance on its outboard front side.

Its inboard side does NOT seem to present any problems with overhang.

And Interestingly, it still has plenty of clearance to negoiate the helix with 2.5" seperation of the 2 tracks.

 

...to be continued

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Posted by railandsail on Thursday, March 8, 2018 8:12 PM

Santa Fe Passenger Cars

Decided to pick out a few of my Walthers streamline Santa Fe 85' passenger cars, since I plan on running these quite often behind a good selection of Santa Fe diesels I have.
1) On the 31" radius curve
.....everything appears to run fine. It does appear that there needs to be minimum of 1" additional 'outer clearance' for the ends of the cars, and a minimum of 1" of 'inner clearance' for the middle girth of the car.

Outer radius here is 31". Next in is 28.5".  The inner one with the autoracks on it is a testing minimum of 24"

 

 

 

 

2) On the 28.5" radius curve
...it appears to be very similar to the same requirement for the 31" curve above

 

 

 

3) On the 24" radius curve
...I wanted to see if these cars could negotiate a 24" radius as these tight curves might be encountered in some staging access, some yards, or a few other misc locations on my relatively small layout.

It does appear as though they can make it around these curves with those very good coupler designs provided by Walthers. It also appears as though the ends of the cars, and the middle of the car requires a wider clearance dimensions, As can be seen via that 'clearance bracket' this needs to be a minimum of 1+1/8" .

 

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Posted by ATLANTIC CENTRAL on Thursday, March 8, 2018 8:46 PM

Brian, it appears from those photos that when on straight track, the diaphragms on those passenger cars are not touching and the gap between the cars is rather large?

No offense, but that is one reason I have not invested in any expensive RTR passenger cars, and it is also the reason I still run mostly 72' passenger cars even on my 36" and larger curves.

I prefer this appearance:

These cars, with their working, always touching diaphragms are coupled at nearly prototype car spacing.

They will handle 30" radius, but I don't have any 30" radius......

And I don't have to widen my track spacing on curves.

I understand not everyone has the room for large curves, but we all make choices. If I did not have the room for large curves, I think my choices would not include long cars......

Sheldon   

    

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Posted by railandsail on Thursday, March 8, 2018 10:05 PM

Well Type Container Cars on 24" Radius

 

For briefity I just put a couple of those well type containers cars on the 24" radius track.
Looks like they fall barely within the 1" boundry lines I drew on either side of the CL of the track, certainly at their mid-girth.

 

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Posted by rrinker on Friday, March 9, 2018 7:28 AM

ATLANTIC CENTRAL

I understand not everyone has the room for large curves, but we all make choices. If I did not have the room for large curves, I think my choices would not include long cars......

Sheldon   

 

Exactly. No, not everyone has room for 36" radius curves. So they make do with the space they have. But then you also have to not expect to be able to run giant articulated locos and 85' cars. It's not an appearance issue, it's not an issue of elitism. It's physics.

                                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by railandsail on Friday, March 9, 2018 8:11 AM

Heavy Duty Depressed Center Flat Car with Transformer Load

 

Tried this one out on the 28.5" radius and was pleasantly surprised that it did not overhang too much at either the ends, nor mid-girth.

 

(sorry for that one out of focus photo,...my camera acting up)

Didn't have 24" curve installed at the time, so I will have to come back and add that photo once I shoot it.

 

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Posted by riogrande5761 on Friday, March 9, 2018 8:43 AM

It looks like you have gone above and beyond with testing for radius.  Seems sufficient now - just don't succumb to the peralysis of analysis.

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Posted by Big Four Lines on Friday, March 9, 2018 9:34 AM

gdelmoro

Ever purchase a locomotive or 85’ passenger car advertised by the manufacturer to run on 18” curves only to find it regularly derails on 20, 24 or even 26” curves? 

It’s happened to me. So the question is what’s a produt’s real minimum radius? How do manufacturers come up with the number?

 

 

Getting back to answering your original question,based on 50+ years of experience and lots of testing. I get trouble-free operation on my mainline with a minimum 30" radius curve. I run full scale 80-85 ft passenger (Walters,BLI,Soho) equiment with diaphrams and body mounted Kadee couplers. I operate at scale speeds 79-110 smph with no issues. I agree with many that track is the problem 80-90% of the time. 

Lastly, From my experience, 24" radius is the absolute reliable minimum for HO operation. The 18" and 22" radius curves are artifacts from the early days of HO in the 50's. Most of the early rolling stock was basically tinplate slide ruled down to 1/87. 

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Posted by railandsail on Friday, March 9, 2018 10:40 PM

Depressed Center Flat Car with Load

 

Went back to storage trailer and picked up that transformer car again so I could put it onto my new 24" radius test track.

 

 

 

 

 

 

Just for the heck of it I decided to put it on a piece of Bachmann 18" track I happen to have setting around. This car could negotiate this track...


 

 

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Posted by railandsail on Saturday, March 10, 2018 7:51 AM

Playing with a Loooong Transformer Car

 When I was down draging out of storage that previous transformer car yesterday, I ran across another one I had, that I had almost forgotten about. It was a loooong car I had found at a train show years ago. Actually I found 2, and sold one of them off.

May have to replace those 'cookie-cutter' wheel sets if i ever try to run this car. But perhaps its just one of those cars that needs to sit in a powerplant scene.

It could negotiate some of my curves,...

 

 

 

even here on 24" radius curves!

 

 

 

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Posted by railandsail on Saturday, March 10, 2018 8:13 AM

Speaking of long cars, how about a Whale Body Tank Car. Just saw a photo posted, and recalled that I have an unfinished kit for one of these. Guess I will have to post a photo of that some day,...

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Posted by ROBERT PETRICK on Saturday, March 10, 2018 9:01 AM

This topic is all very beguiling, but suppose it was established that specifications explicitly stated that the minimum radius was 72 inches. You can bet that someone somewhere would try to shoehorn in a 60-inch radius, and then endlessly complain about derailings and whatnot. Geez!

Robert

LINK to SNSR Blog


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Posted by railandsail on Saturday, March 10, 2018 11:39 AM

Remember I'm saying that these minimum radius will work for all of this rolling stock, as I have not accounded for 'wobble' we experience, nor pushing forces that cause other problems as well. I was just looking to determine a bare minimum fit.

Steam engines are coming soon.

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Posted by ATLANTIC CENTRAL on Saturday, March 10, 2018 12:36 PM

Brian, what about coupler swing, pulling forces, transitions in and out of curves, coupler offset when coupled to equipment of a different length, and the list goes on........

Sheldon

    

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Posted by railandsail on Saturday, March 10, 2018 7:15 PM

Beyond the scope of what I have time for at this moment. As i said I was seeking the BARE MIMIMUM of clearances needed to get the cars and locos (coming) thru.

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Posted by GraniteRailroader on Saturday, March 10, 2018 8:58 PM

railandsail

Beyond the scope of what I have time for at this moment. As i said I was seeking the BARE MIMIMUM of clearances needed to get the cars and locos (coming) thru.

You've identified the overhang (side to side) clearance but have not identified the bare minimum clearances needed to get cars and locos through.
 
Until you can actually push/pull a set of cars through it, your measurements simply identify the over hang. Forces imparted at coupler height will absolutely impact these minimums. 
 
You're halfway there... You need to actually run equipment through those curves to identify what the minimum is. Adding grades will impact this as well.

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Posted by TheWizard on Monday, March 12, 2018 12:22 AM

rrinker

 

 
ATLANTIC CENTRAL

I understand not everyone has the room for large curves, but we all make choices. If I did not have the room for large curves, I think my choices would not include long cars......

Sheldon   

 

 

 

Exactly. No, not everyone has room for 36" radius curves. So they make do with the space they have. But then you also have to not expect to be able to run giant articulated locos and 85' cars. It's not an appearance issue, it's not an issue of elitism. It's physics.

                                    --Randy

Kato makes Superliners and P42's that negotiate 15" curves. It's only physics until you overcome it, as the Japanese have. Then it's just laziness on a manufacturers' part.

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