Reverse Superelevation ?

Fascinating thread. Definitely support the cubist theory as first mentioned in post No 7 - and cannot support the proposal for reverse cant (it might work, but is totally unprototypical - there are better ways to handle the problem). And thanks for the last post Frank - now I have a kingsize headache! :confused:
 
Hey guys, this is getting better and better! ;-)

Now, I definitely have to leave the maths to some brainheads. If we could agree on some formulas, which I then just imply without thinking or really understanding! ;-)

Lots of good thoughts here. Looks like you guys have found the way how to do it. I assume that this EX-cludes fitting ball-bearing wheels thoughout, but IN-cludes additional weight in ALL wagons?!

However:
Still wanna share some 'detailed grief'.
- I have lots of inclines. Sadly cannot tell you the exact figure but think is high normal incline. Most locos have additional weight. Better performance but not endless.
- Hardly any wagons with metal wheels.
- Regularly have BOX-WAGONS misbehaving climbing out of even R3 curves if heavy/lots of wagons behind them.
- Worst culprits are CENTER DEPRESSED CARS. Often inner 2 axles climb out of curves/points for the slightest reason. Metal wheel fixed that to a certain degree.

BUT watching it happen in slow motion shows me how these wagons/axles do NOT behave at all like prototype.
So am frustrated cos think as long as not have R5's + no inclines + all metal wheels, this will keep happening! :angry:
(see post #5 for test pics - i.e. yellow Meindl wagon misbehaving as heavy wagons behind)
 
Aljosha said:
Hey guys, this is getting better and better! ;-)
Lots of good thoughts here. Looks like you guys have found the way how to do it. I assume that this EX-cludes fitting ball-bearing wheels thoughout, but IN-cludes additional weight in ALL wagons?!
Click to expand...
Well I think I've got the cheapest solution with the reverse super. Sounds like you have a similar problem so maybe give it a go.
We?ve certainly got away from the original reverse superelevation topic, but I like discussing this aspect too.

The idea of scale mass being a cube of the linear scale can?t be taken too exactly. Changing scale from 1:20 to the 1:24 that I model in, means the ?mass scale? goes from 1:8000 to 1:14000. So should a 50t loco weigh 6 kg or 3.5 kg ?
The prototype 3?-6? gauge Garratts I ?modelled? at 1:24, were around 70-90 tonnes so the model should weigh 5 to 6.5 kg. Mine are about half that.
(BTW, why does anyone bother with calling it 1:20.3 scale? are you accurate to 1.5% ? I?m not.)



I?ve done a lot of testing to try to measure the tractive effort of my locos and the ?drag? of my rollingstock.
I?ve even come up with a rough equation to let me approximate how many wagons any loco can haul.

If you?re not interested in the maths and like pictures, go read another thread now.

Locos
[H1][/H1] Most of my locos have an adhesion factor of around 20-30%. ie if you measure the mass of the loco and take say 25% of that figure, that is how much drag you can overcome and keep moving. (This assumes all the weight is on the drivers). Real steam locos had an adhesion of around 15%, but diesels can manage up to around 30%, so the model figure is close to the prototype.

Wagons [H1][/H1] My model measurements give drag values around 4% of the mass of the wagon (on level track). This is for plastic wheels, mainly with steel axles running in styrene or aluminium ?bearings?. Those of you with steel wheels and better bearings should have a lower figure.
(Interestingly, when I worked in the real railways, we used a first approximation that the drag was equal to a 0.5% grade. ie only a tenth of my models. )

Grades [H1][/H1] The drag due to the grade is the grade in %/100 times the mass of the train (incl locos).
ie on a 3% grade a 5kg train has a drag of 3/100*5 = 0.15 kg

Curves [H1][/H1] A VERY ROUGH approximation is: the curve drag = 0.04/curve radius in m times mass of train (incl locos)

Example [H1][/H1] So taking the derailment example I started with, of my Garratt weighing 2.5 kg and a train weighing 7 kg. The TE will be 0.25x 2.5 kg = say 620g
The wagon drag is 7kg * 0.04 = 280g.
A 4% grade drag is 0.04*(7+2.5) =380g
So on straight track we have a TE of 620g and a drag of 660g, so it shouldn?t work, but it does JUST. So my approximations are a bit on the conservative side.

Now if you want to rearrange all these equations you can determine what mass of train you can pull on what grade or curve:

Mass of wagons that can be hauled (kg) =
(0.25 * mass on loco drivers (kg)) divided by (0.04 + 0.04/rad(m) + %grade/100)


(This ignores the mass of loco on the grade to simplify it.)
Trying the example again:
The mass I should be able to haul up a straight, 4% grade = .25*2.5 / (.04+4%/100)=7.8 kg.

Those of you with steel wheels may be able to reduce the two 0.04 factors. To determine what it is for you, just take a loco and see how much mass it can haul on the level straight. You may have to put some bricks in the wagons! Then your coefficient to replace MY 0.04 will be 0.25 times loco mass divided by wagon mass.


End of lesson.
 
Teehee :thumbup: :admire:
I said this is getting better and better!
The above maths I'll gladly try out when back home!
 
Another major issue is track twist more accidents are caused by twist than other items.
This is where the high rail swops sides quicker than the length of axle spacing greater than the height of the wheel flange (28-32mm) in real money as in the picture a twist of 20mm over 1.2M.

8fa5c71d982745acbf8b1cfd612b639d.jpg


Something to check with our less than flexiable bogies.
 
coyote97 said:
Hi muns,

for all of you that havent thought about scaling down weight (or dont know about...we cant know everything..thats what forums ar for...):

22,5 x 22,5 x 22,5 would give a cube, and it stands for what is on meaning behind it, but maybe, the 22,5 cube is not suitable for explaing it.

take a cube of 10 mm x 10 mm x 10 mm. In there is a volume of 10ml and it weights 1 gramm filled with water.

if u now DOUBLE the length of the cube (scale 2: 1), u get 20mm x 20mm x 20mm.
If u imagine that in the origin 10 x 10 x 10 mm cube, the "cube10" will fit in the "cube20" 8 times
doing the same with scale 3:1 (cubelength 30mm) the "cube10" fits in the "cube30" 27 times!

so, scaling a body with factor 2 makes 8 times more volume (and therefore weigth)
scaling a body by factor 3 makes 27 times more volume.

8 = 2 x 2 x 2
27 = 3 x 3 x 3

it works the same with scaling down.

so, scaling down weigth from prototypical data means:

with a scale from 1:Y

the factor (and formula) to calculate on the prototypical weight is:

model weight = 1 / (Y x Y x Y) x prot.weight or model weight = prot.weight / (Y x Y x Y)



So, my 1:20,3 scale Railroad has a downscale divisor of 8365 (20,3 x 20,3 x 20,3). That seems much, but it fits well and is true!

All my roling stock or load can be "overcalulated" with that. And i found out that even on load, it fits well. Give the thing some time and do revival of the maths lessons:

the tankcars, the hoppers....."loading" them will nearly match the prototypical weight. I found, that both AMS and Spectrum rolling stock are quite near to the prototypical unloaded weigth.
Fitted with cadee couplers, that rolling stock allows all prototypical operations while pulled with a weightscaled loco without rubberrings.
i found out that my loco is beginning to slip before my cars are pulled out somewhere.

Greetings

Frank
Click to expand...

Ahh, thanks Frank.

I didnt "twig" that the 22.5 was relating to the scale, I thought that yoe were talking dimentions as you referenced HxWxL :)
 
As I am heavily into Rio Grande practice it is interesting, that the comments earlier in the thread, about lash-ups and helper locos in the middle of strings are systems that were used on the Grande. The Grande had many inclines and curves. Heavy rolling-stock ie. full hoppers etc. had lashups with up to 5 or 6 diesel locos at front (sometimes with one in the centre or rear) but very long strings of empty rolling-stock tended to have smaller lashups with helpers at rear or cut into the string. This would stop the stringing that might occur on sharper bends with the lighter cars. This was very prevailent in the earlier steam days when the track was not always true. The later diesel era had better track (well mostly) that could take higher tonnage and utilised much less sharp radius curves.
As I have steep grades I have used extra weight and traction tyres (yes I know!) and also have canted (super elevated) a section of track where the grade is rolling down hill. I used flexi-track with 1.5m lengths so the joins are minimal. Even so there was one join that did display the 'riding' issue and it was ground smooth and it is fine now. Also the dreaded reverse curve raised its ugly head and a lot of work on the switch was needed to bring it back into line (:bigsmile:).
This has been a thoroughly spiffing thread with a good exposition of the maths that proto lines would have had to consider as well.

toodle pip
 
Gizzy said:
The idea of a conical tire is so that the wheel flanges do not contact the rail. (When they do, you get the classic squeal that you hear on tight curves or on points in stations. And obviously the associated wear on the flanges and rails too.)
Click to expand...

Usually, the flange squeal that is heard on a tight radius is the back of the wheel flanges rubbing the check rail (safety rail in US terms) on the inside of the curve, because on 1:1 wheel profiles, the flange and profile will hardly ever prevent overriding - just take a look at them.

I only understand a little bit about this because I used to receive Railway Modeller regularly when Scalefour (now P4) was launched.

On our garden models, coarse LGB flanges will probably never override a curve, but as you go through Bachmann/Aristo, to Accucraft (AMS - not too sure about BMS) the flanges get finer - but never to real finescale standards.
 
Neil Robinson said:
PaulRhB said:
Amongst all the discussion of cubist theory have we found a way to scale down gravity to match? :bigsmile:
Click to expand...
Answers on a postcard please to Mr I Newton, Woolsthorpe Manor, Lincolnshire. :rolf:
Click to expand...

I could be wrong here, but the forces of gravity are proportional, so it automatically scales down :thinking:

Or is it that it's purely relative?.............:rolf::rolf:
 
gregh said:
(BTW, why does anyone bother with calling it 1:20.3 scale? are you accurate to 1.5% ? I?m not.)
Click to expand...

'Cos that's wot it says on the box :bigsmile:

2a0e2910614c4ebcb095158469a65e4e.jpg
 
Rhinochugger said:
Gizzy said:
The idea of a conical tire is so that the wheel flanges do not contact the rail. (When they do, you get the classic squeal that you hear on tight curves or on points in stations. And obviously the associated wear on the flanges and rails too.)
Click to expand...

So - why not use prototypical check rails on curves that are prone to causing derailments?
Mick
Click to expand...
 
trammayo said:
Gizzy said:
The idea of a conical tire is so that the wheel flanges do not contact the rail. (When they do, you get the classic squeal that you hear on tight curves or on points in stations. And obviously the associated wear on the flanges and rails too.)
Click to expand...

So - why not use prototypical check rails on curves that are prone to causing derailments?
Mick
Click to expand...

Good point - I've never had to do it, because a little bit of superelevation has always done the trick for me - it's quick and cheap.

It won't help Greg's problem with stringlining though - I think he needs to put on some weight :rolf::rolf:

Just a thought though - Greg, do you think your rail profile could be adding to the drag effect?
 
squeezes on sharp curves are often enough not from the touching of the flanges.

Railroads with problems on flanges going away uses grease to lubricate the flanges, but if u listen even on those modern cars and locos, they squeeze as well, even with lubricated flanges.

When the curves get too tight, the canting of track and wheels on track ist enough to eliminate the different ways the wheels should make.

So there is some high-frenquncy slipping on one of the wheels with a kind of "slip-dig" effect. Thats the squeezing.

On sharp curves, all cars are queezing, even when there is no safety rail.



Regarding the discussion on canting there is a solution for the "outpulled" trains. Increase the centrifugal power by "slightly" more speed....

:bigsmile:



Greetings

Frank
 
Just had one other thought - on tight curves wasn't it standard practise to widen the gauge a little to ease the passage?
Mick
 
Not sure about 1:1 stuff.

In model terms, Aristo track is better than LGB for traversing 8ft diameter, and I assume that Aristo ease the gauge more than LGB.
 
Rhinochugger said:
I could be wrong here, but the forces of gravity are proportional, so it automatically scales down :thinking:

Or is it that it's purely relative?.............:rolf::rolf:
Click to expand...

Sorry but Mr Attenborough often mentions the strength of tiny insects in comparison to humans
as they not only carry huge leaves etc but they have the proportionally larger force of grav y pressing down on them.

it
:@

Evidently it is proportional to mass not scale according to a fascinating article I just read and didn't really undestand . . .
:rolf:
 
on german standard gauge it was practice, but that was cancelled with some new rules that dont allow too sharp curves any more (what was usual in former days for many industrial connections).

the widening has another reason though.

Even trucks, but "normal" 2-axle cars for more, are holding the axles out of a line that leads to the centre of curve. The more the measurment between the axles is, the more "out of line" are the axles.
As a result, the axles dont point to the middle of the curve.

For that, the axles have a "fault-position" of some degrees, with what the flanges begin to pinch between the rails. So in very sharp curves, they just widened the track some mm.
In my hometown we had an old connection (standard gauge) with a 80m radius and therein a curved switch 100/80 meters.
The track had widenings of 25 and 20mm (what was the most allowed measurment for this).

Some construction Engineers therefore always looked for constructions for radial adaption of the axles. Mr. Klose and the famous Klien-Lindner Axles are examples for that.


Greetings


Frank
 
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