P87 : What will it take to successfully promo?

[Prof Klyzlr]

No-one is doubting that model locos can be sprung... but can they be sprung so as to replicate that wonderful slow side-to-side swaying that locos do on badly maintained track, as demonstrated on several You-Tube clips of such Railroads as the Maumee & Western, that we're all familiar with?

The short answer is 'no'.

Dear Jordan,

 

Not sure I buy that: 

 

- we can "scale" the distances involved,

(distance of axle spring, distance of track deflection, distance of rock),

 

and indeed, when we think "scale model railroading", it's primarily (only) the measurable distances we concern ourselves with...

 

- we can "scale" the speed of the loco + cars travelling over the section

(which, bearing in mind speed is simply distance-over-time, is a direct and automatic relationship to "scaling distance" as above)

 

- we can adjust the mass of the loco within limits

(modellers have been adding weight to locos for years,

adding the weight at appropriate places to achieve desired balance and weight distribution is just a part of the process...)

 

- and we can adjust the spring dynamics (replace common "soo strong as to effectively be solid" springs with suitable units,

a la NWSL "wimpy" or repurposed Kadee springs)

 

 

Maybe I guess I'd feel more comfy saying:

 

- The short answer is no,

 

- the slightly longer and more-complete answer is "Yes, if one is willing to put the required work in..."

(funnily enough, just like many facets of this wonderful hobby ;-) ).

 

Happy Modelling,

Aim to Improve,

Prof Klyzlr

[Prof Klyzlr]

Dear Andy,

 

 

The only modification is the same as the one shown here. Adding a "gimbal" bearing to one of the truck bolsters of each loco and car. So the car can roll over less even track.

 

 

...and for those of us who are maybe more impatient than advisable, would loosing one of the truck screws (IE configuring a car with one truck "just swivelling" and the other "able to rock in all axis") the quick-n-dirty equivalent?

 

Happy Modelling,
Aim to Improve,
Prof Klyzlr

[Prof Klyzlr]

Dear Andy, Outside-looking-in curious,

 

OK, after re-reading the posts, and reading this

 

 

I'm pretty much convinced, ,,, that handlaying track the "traditional" US modelling way is instant death for proto:87....

 

I have to ask:

 

Is it possible to seperate

 

- "P87-level detailing of track", (esp turnouts)

 

and

 

- adoption of full-blown mechanical "P87 Track/wheel" specs

 

as independent issues/missions/approaches???

 

Happy Modelling,
Aim to Improve,
Prof Klyzlr

[Andy Reichert]

Dear Andy, Outside-looking-in curious,

 

OK, after re-reading the posts, and reading this

 

 

I have to ask:

 

Is it possible to seperate

 

- "P87-level detailing of track", (esp turnouts)

 

and

 

- adoption of full-blown mechanical "P87 Track/wheel" specs

 

as independent issues/missions/approaches???

 

Happy Modelling,

Aim to Improve,

Prof Klyzlr

 

Yes, I treat them that way. You'll find two sets of template diagrams on the website. One for HO and one for Proto:87. Apart from the frog and guard rail postions, the only other difference is the non-scale offsetting of the point hinges towards the frog for HO, in order to give the needed greater hinge flangeway clearance. The three special tie plates in that area get shuffled around to allow for that.

 

Andy

[Andy Reichert]

Dear Andy,

 

 

...and for those of us who are maybe more impatient than advisable, would loosing one of the truck screws (IE configuring a car with one truck "just swivelling" and the other "able to rock in all axis") the quick-n-dirty equivalent?

 

Happy Modelling,

Aim to Improve,

Prof Klyzlr

 

That works for HO, but is a bit iffy for P:87. The bolster top and underside of the king pin are both flat. So as the loosened truck rolls from one tilted side to the other, it first rolls towards being flat using (say) the LH edge of the king pin as its roll fulcrum, then suddenly is halted as the bolster jolts flat against the king pin, then has to lift the car from a differnt point, as the fulcrum instantly changes to the RH of the king pin. So you get a double impulse to the car body.

 

You can often see that effect as a shudder of the car body as the car traverses a one sided track dip or rise, when the energy of the ose two jolts are absorbed by the body, and turned into a rocking oscillation. The "knife edge" of the stabilizers removes the cause of both jolts completely.

 

Andy

[Andy Reichert]

No-one is doubting that model locos can be sprung... but can they be sprung so as to replicate that wonderful slow side-to-side swaying that locos do on badly maintained track, as demonstrated on several You-Tube clips of such Railroads as the Maumee & Western, that we're all familiar with?

The short answer is 'no'.

 

I agree, as we are dealing with a similar (but not equivalent) situation to a clock pendulum. If it's 1/87th as long, it's gonna swing 87 times faster. The real cars are rocking with massive mass over the pivot and the relatively weak, but fairly linear restoring force of the springs of both sideframes trying to achieve equilibrium. The side restoring forces are going to have to be vanishly weak to only rock a very light HO body at the same speed/frequency.

 

That's partly why I'm such a fan of equalization as the primary stabilizing system for HO. It doesn't require "micro-springing" forces and their necessary balancing, and doesn't introduce the "87 times faster-sort of" very fast rolling motion that is so common on models if they are displaced. CSB's do have the low forces and overall stability, but are fundamentally highly non-linear in their response, so shouldn't be able to reproduce a slow sway.

 

Equalization can reproduce a slow sway if it's built into the track as a rolling motion profile that the car can follow.

 

Andy

[Prof Klyzlr]

Dear Andy, Jordan,

 

so, if

 

 

Equalization can reproduce a slow sway if it's built into the track as a rolling motion profile that the car can follow.

 

 

why don't we do that? It really feels like most modelling missions:
- define the problem/requirement
- nut out a solution (Thanks Andy!)
- deploy, and enjoy the results...

 

Again, not "no, it cannot be achieved",
but rather "it may not be out-of-a-box RTR easy, but if you really want it, you'll find a way..." ;-)

 

Happy Modelling,
Aim to Improve,
Prof Klyzlr

[Glorious NSE]

why don't we do that?

 

<Devils advocate...>

 

Wouldn't all cars sway exactly the same if you did that, unlike the prototype where each car would likely have different mass and slightly different suspension responses?

[burgundy]

Oddly enough, you already have a partial answer, as parts are already available for 21mm gauge, also known as P4/Irish 5'3".....

Good point, well made .

However, I don't think any Irish railways had the taste for stub points that early US railroads demonstrated.  Have a look at the arrangement in the foreground of the linked photo, which at first sight appears to be a diamond crossing. On closer inspection, it looks like two stub points, end to end, so that it effectively creates a double slip. Then note that there appears to be only one switch lever, so it must have had three positions on one of the switches with the other one static. Not something that you can recreate from sectional track - and quite an interesting challenge in Templot.

Given the very obvious differences of early trackwork in the US, and the need to build it pretty much from scratch, you might as well go the whole way and follow P87 standards. 

Best wishes

Eric

[Miss Prism]

Concerning the frequency of side-to-side wobble on coaches, some video experiments on 4mm scale 160g coaches* a few years ago showed that such a frequency for vehicles with secondary springing was several times less (ISTR the factor was about 4 or 5) than was present with otherwise-identical vehicles with solid bolster mounts. Although the frequency for the sprung model vehicles was still many times greater than the prototype of course, the most significant improvement in the characteristic of the oscillation was the dramatic increase in damping showed by the sprung vehicles.

 

* The ubiquitous Bachmann Mk1

 

 

[meil]

I agree, as we are dealing with a similar (but not equivalent) situation to a clock pendulum. If it's 1/87th as long, it's gonna swing 87 times faster.

 

Andy

Er no. It will swing at root (87) times faster. That's because the time period T = 2*Pi*sqrt(L/g) where L is length and g = gravity.

[CVSNE]

Good point, well made .

However, I don't think any Irish railways had the taste for stub points that early US railroads demonstrated.  Have a look at the arrangement in the foreground of the linked photo, which at first sight appears to be a diamond crossing. On closer inspection, it looks like two stub points, end to end, so that it effectively creates a double slip. Then note that there appears to be only one switch lever, so it must have had three positions on one of the switches with the other one static. Not something that you can recreate from sectional track - and quite an interesting challenge in Templot.

 

Bernie Kempinski built that very arrangement (using the photo from the Archives you linked to) on his Aquia Landing branch. I've watched dozens of people operate on Bernie's layout - without exception every one of them derails at that section of the layout the first time they try to negotiate it. It's just not all that intuative, but great fun!

[dave1905]

Personally I would say the thing that would prompt more people to improve their track is those little sports video cameras.  If you want to "convert" somebody, put one of those cameras on a flat car and shove it around the layout.  Nothing makes model track look hideous than a track level view.

 

It may drive me to changing from "small" to "micro" spikes.

[Pacific231G]

It is only a more sensible place if you regard the track gauge as the one sacrosanct dimension. Not everyone agrees. If you use over-width RTR wheels, logic dictates reducing the track gauge so that wheelsets still fit within scale-width models -- behind cylinders, valve gear, axleboxes, bogie sideframes, and inside splashers. Mixing vastly overscale wheel profiles with an exact-scale track gauge, as the rest of the world does in H0, is just crazy. Why insist on one being to scale if not the other? 00 gauge is not as daft as it's made out.

 

It's puzzling that modellers have this preoccupation that the distance between the rails must be correct, even when hardly anything else is.

 

Martin.

Hi Martin

I can see the argument for some gauge reduction in order to avoid wheel sets becoming too wide with the wider tyres needed for practical model curves. I just think that was taken to an absurd degree in 00 to accommodate the sort of traction engine tyres required to allow toy trains to negotiate twelve inch curves. 

 

To get a feel for this I compared the standards for HO and Proto-87. They both of course use the same track gauge and the difference in outside wheel set width was just over a millimetre. This accomodates "standard" HO tyres of 2.74mm-I assume that's RP25-110 against Proto-87 tyres 1.62 mm wide. On that basis, if you wanted to keep the outer faces of wheel sets from being any wider at all than scale you'd need a gauge reduction of about 1mm which is about 6%.  In 00 the actual gauge reduction is more than double that at about 2.4mm which is about 15%.

 

On plain track I can't actually see the difference in gauge between EM and P4 either in the track itself or in the end profile of rolling stock and it's the fineness of the crossing and guard rail clearances rather than the actual gauge that to my eyes makes P4 track look more realistic. The difference between scale or EM and 00 track IS noticeable. To my eyes 00 track does look narrow and requires compromises in sleeper dimensions, platform clearances and the six foot  that we've discussed elsewhere.

 

It's interesting that the BRMSB recommended a gauge of 18mm for "fine scale" 00, against some who argued for 19mm, on the basis that some gauge narrowing was desirable and that would be practical for most modellers. I tend to think that modelling in HO is similar in terms of closeness to scale to modelling in EM except that the compromise is in the wheelsets rather than the track gauge.

 

Because for HO the jump from RTR to true scale is that much less than it is from 00 to either EM or P4 I suspect that Proto-87 will always be more of a niche. If EM gauge HAD been generally adopted for 4mm/ft scale I wonder how many British modellers would have gone for P4.

[highpeak]

The OO compromise changes the track gauge. The HO compromise affects the rolling stock. If I look head-on at my model of a USRA light 2-8-2 I can see that the cylinders stick out by about a scale foot beyond the running board. A photograph of the real thing from the same angle shows they should be in line.

[Andy Reichert]

Er no. It will swing at root (87) times faster. That's because the time period T = 2*Pi*sqrt(L/g) where L is length and g = gravity.

 

Mea Culpa. You are absolutely correct for a gravity pendulum.

 

Andy

[Andy Reichert]

Concerning the frequency of side-to-side wobble on coaches, some video experiments on 4mm scale 160g coaches* a few years ago showed that such a frequency for vehicles with secondary springing was several times less (ISTR the factor was about 4 or 5) than was present with otherwise-identical vehicles with solid bolster mounts. Although the frequency for the sprung model vehicles was still many times greater than the prototype of course, the most significant improvement in the characteristic of the oscillation was the dramatic increase in damping showed by the sprung vehicles.

 

* The ubiquitous Bachmann Mk1

 

Agreed. However, I don't know if those results would be different if the support points of secondary springing were placed as close to the car centre axis as the edges of the king pin surface. That's where the bogie rocking normally has its twin fulcrums.

 

Another benefit of secondary springing is that the car behaves symmetrically, regardless of the direction of travel. And off center forces from pushing body mounted couplers of the US type, can be problematic if using mere 3 point body support. So CLAG members in particular are not supportive of my proposing the single gimbal approach, although the purposes here, it does improve the track holding over track twists for proto flanges so much better than unmodified twin rigid bolsters.

 

One other factor that I suspect significantly affects both proto suspension trackholding and car side wobble/sway rate is the weight of the car. Although the NMRA has done practical testing to back up their recommended weighting tables, it seems to me that more weight is needed to make model suspensions systems function as desired. The ratio between unsprung weight and sprung weight is so close in our lightweight RTR models, that the car body tends to be flung about while the suspension system is still trying to adapt to absorb just the wheel movement.

 

I have given some though to possible practical methods full (symmetrical) body equalization, but need to try prototyping any designs out, before expounding any futher.

 

Thanks for introducing this aspect.

 

Andy

[highpeak]

This paper provides an overview of the factors that create the prototype phenomenon known as harmonic rock, a problem on poorly maintained stick rail track [url=http://www.transportationu.com/articles/hrr_01.html As you would expect, it is a fairly complex set of interactions which may or may not scale down.

[F-UnitMad]

Er no. It will swing at root (87) times faster. That's because the time period T = 2*Pi*sqrt(L/g) where L is length and g = gravity.

oh heck... big sums!! Time for me to exit stage left, I think...

[Andy Reichert]

oh heck... big sums!! Time for me to exit stage left, I think...

 

It gets worse if you consider that the car body is a pendulum upside down and the springs are the restoring force, which may not be linear due to them having up and down stops, while gravity is working to displace it even more. 

 

That's when I'm going to look for a young enthusiastic intern. . . .

 

Andy

[Pacific231G]

The OO compromise changes the track gauge. The HO compromise affects the rolling stock. If I look head-on at my model of a USRA light 2-8-2 I can see that the cylinders stick out by about a scale foot beyond the running board. A photograph of the real thing from the same angle shows they should be in line.

 

I think that's more than just the effect of compromising on tyre width. That alone shouldn't cause a widening of more than about 0.5mm each side which is a scale two inches. I'd  suspect that the cylinders have been moved out 3 mm or so to enable the pony truck to negotiate tighter curves. 

[highpeak]

Oh it's absolutely more than required by the wheel standard, though the wheel standard alone would force the cylinders out. The extra width is to allow enough slop to get round tight curves to be honest. There is a very generous amount of side play on the second axle and a pretty thick spacer between the connecting rod and the coupling rods to afford the clearance for that side play. I don't know what the manufacturer says for a minimum radius, but I suspect it's probably tight enough for the engine to look a bit comical negotiating it.

[trisonic]

Personally I would say the thing that would prompt more people to improve their track is those little sports video cameras.  If you want to "convert" somebody, put one of those cameras on a flat car and shove it around the layout.  Nothing makes model track look hideous than a track level view.

 

It may drive me to changing from "small" to "micro" spikes.

At normal viewing distance spikes are so unobtrusive as to be almost non-existent.

 

A photo I took at a Shortline in New Hope PA:

 

 

This is quite a close up but look at the spikes on the left hand running rail.

 

Best, Pete.

[trisonic]

Extreme close up of a rail joint:

 

 

Same location as above. The spikeheads are smaller than the boltheads. The only time they are very noticeable is if you lay your head along the rail and squint down the track ala "The Perils of Pauline" (which coincidently was filmed on this very same line - which was a branch of the Reading), however I do not recommend this course of action....

 

Best, Pete.

[dave1905]

Almost 40 years ago when I was still in college, a buddy of mine was a member of the Buckingham Valley Trolley Museum which operated on the NH&I during the McHugh Bros operation.  I used to help out occasionally on that line.  I have actually tamped track on the NH&I and have run a trolley on that line.  The trolley was powered by a truck with the rear end up on blocks and a generator in place of the pumpkin (it still had the cab on the truck). 

 

The one steam trip I took on that line had an injector failure and they had to drop the fires and have a diesel come out and rescue the train.

 

Every year a local socialite would rent the train and they would make a run up and down the line with a hundred or so of his friends then stop behind his house, and they would all go to his house to continue the party.  The socialite was gay, my friend (who was not gay ) thought that he threw a great party on the train, but the fireman kept a steam line handy to repel boarders.  8-)

 

The NH&I had actual revenue customers, my buddy was working as a brakeman on a run one winter day.  There was a snowmobiler riding down the ROW.  The train gently eased up behind him (the noise of the snowmobile was louder than a DS-4-4-1000 just idling along) and when the engine was about  100 ft behind him, they leaned on the horn.  The snowmobiler looked back, saw the train, gunned the snowmobile and veered off the right of way.  The last they saw of the guy was the snowmobile heading off in one direction through the woods and the snowmobilier flying off in another.