Locos derailing

When it all comes down to it you can't beat good track and benchwork. Model locos can derail when there is an obvious fault like an oversprung pony truck or wheels out of guage. But in the end it all comes down to trackwork and benchwork. If you lay track that looks like the Himalayas then you can't honestly expect a loco doing 100kph to stay on. If lay a curve that's not a constant radius then locos are going to come off. Benchwork is another factor. If you benchwork is to lightly constructed then it'll sag or deform and your already bad tracklaying gets compounded into something really awful. Take your time and spend a few extra dollars to build good bench work and then lay good trackwork. The dividends are no derailments. My base benchwork is all 4"x3' L girders on 3'x2' legs and was initally topped by 3/4" chipboard. It was a bit of overkill and i have since revised the specs for the new layout. The L girders remain the same but I'm changing to 10mm ply cut to profile. Track, which is Peco code 75, is layed on 8mm concrete expansion jointing and has not given an moment of trouble in 5yrs. The expansion jointing is very stable and is not effected to much by heat or cold and also acts as a sound deadener. It's easy to use and is just stuck down with a stuff called Bondcrete which is a concrete sealer similar to dilute PVA glue but with additives to make it go off faster. Track is treated the same way with the Bondcrete applied to the expansion jointing and the track pressed down onto it. I usaually hold the track in place with a couple of pushpins and and a couple of bricks. The glue sets in about 20 minutes and you can ballast with the same stuff just diluted a bit as you would with normal PVA glue. If your track and benchwork is good and locos still derail then start checking the loco for wheels that are out of guage, wheel out of round, wheel centers that have shifted and this is quite common on wheels with platic centers, rims that are twisted on the wheel center and bogies that are over sprung mostly Bachmann. There are other things that can effect running but these cover most. I've come to the conclusion over the years that the words Ready to Run and Plug and Play were invented by someone with nothing better to do.

Ozzie21

QUOTE (dwb @ 21 May 2006, 04:30) <{POST_SNAPBACK}>>if it's wrong I adjust it
What percentage of stock needs adjusting and which source heads the list?

David

Well to put it mildly all of it! Every loco, every coach, every wagon is usually has it wheels out of guage. Not much and it would probably fall into that 14.5 to 14.72mm back to back that manufacturers use and this is on both sides of the atlantic. Every piece of ready to run rolling stock I've ever bought has had to have it's wheels reguaged to 15mm back to back. There's no one offender in my book as they all do it, Walthers, Athearn, P2K, Hornby, Bachmann, Kato, Atlas the list goes on. I've bought $4,000 brass engines that derailed beacause the wheels aren't guaged properly. It all depends on which of the multitude of so called "Standards" the manufacturer applies, his own, the NMRA, the BRMSB, NEM?? Once upon a time there was going to be a "Standard" for the UK but no one could decide on the width the rails were to set apart to based on the scale. HO 3.5MM is 16.5mm, OO 4mm is 18.83mm but commercial concerns were the decideing factor so we got stuck with 16.5mm and that was it. Track was made to be roughly eqivalent to NMRA recommened practices but to run European rolling stock with it's then huge flanges meant code 125 rail so everything was opened up slightly to accomodate. Now we have fine scale rolling stock that runs on set track geometry and it's going to give problems. It'll run fine for the most part on code 100 rail but as the rail gets finer, code 83, code 75, code 70, code 55, so the derailments increase because of the sloppy set track standard used to set the model up to in the first place. With diesel models it's proably not a problem due to the weight in modern diesels but steam models are a lot lighter and are more prone to derailing so you have to be vigilant and check the wheels every model you buy.

Ozzie21

QUOTE (Gofer @ 22 May 2006, 05:43) <{POST_SNAPBACK}>What's a derailment? Is that the occurance when a rail vehicle leaves the track? I wouldn't know. I don't get derailments but then again I took time to lay my track properly .

well there's always one

Ozzie21

QUOTE (dwb @ 24 May 2006, 03:30) <{POST_SNAPBACK}>>whereas with flexitrack it can be a bit out
I use "tracksetta" gauges to assist. Even using these I have had to lay curves up to 4 times to arrive at the location I want. The slightest shift and you can be out by an inch and a half.

David

Tracksettas can be quite useful if you are laying a curve off a point but they are pretty useless if you are laying a fairly large curve. What I did was get some very large tracksettas made fron 3mm MDF in the radius I most commonly use ie 36", 39", 44" and 48" . These cover 90 and 140 degrees and fit exactly the same as the Peco unit. The other thing is to mark out the curve before you lay it by using a long arm. I made mine mine from 1" square cedar with a steel point at one end drilled it, at the required distances from 30inches on out to 60 inches in one inch increments, to take a pencil at the other end. Another trick to laying flex track on curves is to allow for easements at the starrt and finish of the curve. These should be about 8 inches long and roughly two sizes up from your desired curveture ie: actual curve 30" with easements at either end of 34" or 36". This will allow the leading bogie of any vehicle an easy transition from straight to curved track. This also helps eliminate the effect of overhang on our not so scale models.

Ozzie21

QUOTE (60134 @ 25 May 2006, 22:42) <{POST_SNAPBACK}>Ensuring that these are all transition curves with the correct degree of super-elavation, naturally!

60134

Yes dumb me forgot that. Now what is the correct amount of super elevation to use I used 3inches as a guide. I used 20thou strips of Evergreen styrene under the outside rail. I'm not sure how this would work on a loco with a solid chassis as at the time I was modelling US steam and all my locos were fully sprung. The effect was good although some of the rolling stock needed some tweaking to get through.

Ozzie21

QUOTE (60134 @ 26 May 2006, 23:14) <{POST_SNAPBACK}>3" worth of styrene strip? I think that would be a leeeetle extreme, don't you?

There must be a set formula for super-elevation and transition for curves but I wouldn't know where to look. Any ideas guys?

60134
Well I did. 3inches was normal super elevation on the C&O in steam days based on 120lb per yard rail on mainlines and 90lb per yard on secondary lines. This works out to about 20thou in HO scale, the track we use. So I used Evergreen styrene strips placed under the outside edge sleepers but directly under the rail near the center of the curveture. The biggest loco I had at the time was a brass model of an H-8 Allegheny which weighed in at, in real life, around 600tons in working order or around 2 1/2lbs in model form. It didn't fall off the curve and actually was less prone to derailing after the super elevation was added than before. So it really works.

Ozzie21

QUOTE (Rail-Rider @ 28 May 2006, 07:03) <{POST_SNAPBACK}>For a slightly more technical response than my previous post, readers might like to take a peek at

Central Pacific Rail Road Photographic History Musem

There, you can see some rather nice photographs graphically demonstrating old, simple tools used to check and adjust superelevation. The Americans really do excel with this sort of site and I feel safe in suggesting that the calculations are close to universal, regardless of country of origin - maths and geometry don't change much, although specific engineering techniques can vary quite a bit!
A more austere presentation of simple track geometry is available from
"Railroad Track Standards": US Army Technical Manual # 5-628, dated 1991

If you want transitions (getting a bit complicated now), try
Trailing Edge Technology's Superelevation and Transition Spiral Web Pages

Trailing Edge provide a very handy Superelevation and Transition Spiral CALCULATOR
Unfortunately, the calculator was exhibiting a "Server Runtime Error" at the time I posted this, but might be recovered by the time anyone else tries it. Maybe after the weekend.

However, their Transition Spiral PRIMER was working just fine and is truly fascinating for the technically minded.

The whole business becomes much more complex when forced to prooduce some form of 'optimum' banking for trains travelling at quite different speeds. It's considerably simpler if the track is dedicated to one, standard type of traffic.

Yes it is. Mine was based on the fact that many of the frieght trains traversing the C&O mainline in steam days were limited to around 80mph using friction bearing stock. After the introduction of diesels and lightweight roller bearing stock in the early fifties there were many civil projects where the superelevation was changed and made larger to accomadate 100mph plus running. I would say it would have to be a trial and error project with a rigid frame model to see if it could handle 6" of superelevation used on modern tracks.

Ozzie21