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Discussion Starter · #1 ·
I've spent some time track laying over the last week and a question occurs to me that I've never seen discussed.

I'm using Code 100 Peco track and I've included a 6ft x 4ft 6ins contiuous run oval, for the benefit of my two grandsons, as part of my layout. I have tested the completed oval with the following results:-

Using a Bachmann Collet goods with Manor 6 wheel tender and a Bachmann 7 plank PO wagon, I've completed the following circuits without derailment
1) 34 circuits "flat out" before derailment
2) 51 circuits at medium scale-like speed (about 1/2 of above) before derailment
3) 48 minutes continuous run at slowest speed possible with no problems

Both derailments were in the same curve, but at different points .. one where the flexi track joined a set of points.

So the question is ... would you be happy with this? Is this an acceptable tolerance?


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2,202 Posts
for a 'home only' layout this seems acceptable...however, the crux is...for whom the oval is really intended?

I have built a layout for my young son to enjoy..Thomas, Henry and James not withstanding!

The only real modification done on his insistance was the addition of a Peco turntable.....

I attempted to avoid strict 'trainset' is 'expandable' in a scenic manner, with tunneled portion,etc....and uses Peco setrack points,plus flex track, code100...(setrack doesn't seem to be available in code75!]

HOWEVER...the main criteria I imposed was, the trackwork, etc, had to be as near as possible, totally reliable.

same with the choice of locos he could rely on.

so, even though the odd curve was less than 1st [or is it 3rd?] radius..and Bachmann coaches needed their solebars relieving as the bogies were on 'full swing'' at certain parts.....this has proven to be the case...even over the part where the baseboard 'joins (it splits in half, folded)......using pCB panels with the rail soldered on..

I went to great lengths to achieve this there is nothing more liable to make a youngster 'lose interest' in a model train, than its continual sticking and needing a push...or derailing.

I would take a closer look at that curve if i were you....eyeball from rail level if possible....maybe use a small hand mirror?

look for abrupt changes in direction from straight to curve......also, kinks which create a tight radius spot.
plus, make sure you haven't introduced a slight adverse camber?

derailing on a curve can also be caused by gauge tightening...i try and 'push flex track into the curved alignment rather than 'pulling'....

\another problem to eyeball for is 'twisting' of the track on the curve.

all these may not be the slightest bit apparent from a general overview the loco and wagon at slow speed, look for wobbling, or slight jumping, etc....and find out why?

for young kids and trains, one loco I definately would avoid is the Hornby 'Thomas' and those locos that share it's (for the time, marvellous) chassis.
reason is, its traction tyres on the centre drivers.

young kids sometimes like to push the loco along a bit, rather than 'controlling' it...the traction tyre sets up so much resistance to pushing, it strains the wheel to axle joint, and can dislodge/shear the crankpin.
one broken Thomas!

for kids and reliability, I dont think anyone can beat the Hornby J94.
It is short wheelbase, doesn't stall easily on insulated point crossings...has all wheel pickup, no tyres, runs real slow, smoothly, and can be obtained in a number of liveries and shapes.

warning...the Bachmann 158 DMU my son bought 'me' for my birthday, sometimes snags its exhausts on the trailer coach on his tight curves...but he doesn't care!

If real young kids are involved, I suggest a simple controller...(we use the Gaugemaster one)...I have drilled the knob at right angles to the axis.....[opposite its fixing screw, as it happens]and inserted an L-shaped piece of coat hanger wire....about an inch long....then I drilled [carefully] a hole on hte face of the controller, and inserted a bit of wire covered in plastic (so it doesn't stab anyone] that the L shaped wire stops when it limits how much the knob can rotate.

this limits the MAX voltage to track..thus loco speeds....hence, increases reliability of running...and reduces silly but expensive crashes.

by drilling a series of holes on the face of the control box...or by adjusting the clamping screw on the knob, max desired voltage can be selected.....especially to suit a reluctant engine.

incidentally, the Bachmann Thomas is far superior...we have one, and a james, which uses the same chassis....their eyes move!

These are not available new in the UK for copywrite reasons, but can be had off titernet.

the green tank from bachmann [same loco, no eyeballs] would make an excellent industrial or freelance loco.

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10,720 Posts
I have just spent some time running a train flat out on my own layout to see what I would tolerate. The answer is "not a lot" but maybe I am a bit picky. I have had problems with derailments where curves (flexi track) went straight into points. I came to the conclusion that this was a bad idea since the curve track always tended to straighten leaving a slight kink at the join. By allowing a 3 or 4 inch straight section before the curve starts (ignoring transition curves - I'm still greedy for space), you can more or less guarantee a kink free join between the point and the flexi track. This will probably eliminate your derailment problem.

In my own running session, the derailment I suffered was due to the locomotive (Hornby class 29) losing contact at full speed over an electrofrog double slip which has not yet had the crossings wired up, so it is actually a very long dead frog. The sudden loss of power gave such a jolt that the 7 coach train (5 Bachmann Mk1s and 2 Hornby Pullmans (the long lit ones)) succeeded in leaving the rails as their momentum carried them into each other. The problem was alleviated once the two wheels picking up on each side were more thoroughly cleaned with Isopropanol.


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303 Posts
For tight radius curves, it is better to use set track than flexitrack, as the setrack by design allows for a little bit of gauge widening on the curves and ensures that the radius of curvature is constant and good rail joints without gaps or sudden transitions in radii.

I suspect that the derailment problem may have something to do with the gauge narrowing that arises when you bend flexi-track through too tight a radius. Also with flexitrack you have to very careful to ensure that you do not introduce any slight kinks in the curve. Derailments occur when one of the wheel flanges finds a place where it can climb out from between the rails. This could be anywhere that there is a rail joint or a sudden change of rail height.

Perhaps this needs a bit more explanation. Consider a set of wheels standing on a piece of straight track. The flanges are not in tight contact with the inside edge of the rail and as they move they stay parallel to the inside rail edge. The coning on the flat part of the wheel tread (present on good wheel sets) ensures that gravity keeps the wheel in the centre of the track and it should not hunt from side to side. In theory there should be no derailments at all.

Now consider a pair of wheels travelling on a curved piece of track. There is a lateral force seeking to push the wheel set towards the outside of the curve. At reasonable speeds this is balanced to a greater or lesser extent by the gravitational effects of the tread coning, and a state of equilibrium exists. If there are no sudden increases in the radius of curvature, the flanges are kept away from the edge of the rail. With tighter curves and at greater speeds, the flange leading edge is forced against the edge of the rail more often and hunts back and forth..

Whenever the leading edge of the flange is forced against the inside edge of the rail and there is a rail joint present with enough roughness or gap to give the flange edge a purchase, the wheel may climb out of the four foot and you get a derailment. I mentioned that the wheels may hunt from side to side when travelling too fast. This explains why the derailment does not always occur in the same place. The laws of chance indicate that the right conditions for a derailment will only occur from time to time, all we can do is ensure that these can occur as infrequently as possible, by laying smooth long radius curves, with transition and ensuring that the back to back of the wheelsets, the squareness of our chassis, the freedom of movement of bogie pivots and so on are all at the optimum.

Using set track helps with sharper radii as the gauge widening helps to keep the flange leading edge off the edge of the rail.

Child Psychology: A child will soon lose interest if the running is unreliable. Yes, but they will also lose interest if everything runs smoothly all the time. They will want to run the locos flat out or connect all the stock up to the locos in a double header. Often the intention may be to create a derailment and get adults attention.

I hope this helps.


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2,202 Posts

we got ours over ebay from US of A.....quite good value, even with postage, compared to hornby.

themech is a bit cheapo.....and I really think they are more 'scaled' towards HO.....since they are quite compact.......but......they emulate the films better.

James could be larger/longer....and Hornby's Henry is very good considering......

but the bachman 'moving eyes' really do the business.....a trick Hornby could well emulate? [they shift from side to side as the loco moves.......maybe with DCC they could be made to watch you whilst stationary?.............DCC smiles too????
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