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Wednesday 28 May 2014

GBL Black 5 - Almost Motorisable

In two minds about obtaining this locomotive display model because it is not of Southern origin. However, the BR standard Class 5MT was developed from the Black 5 and some were allocated to BR(S). In fact the only outward difference I have read about is 'the running board on the BR 5MT is higher, revealing almost all of the wheels, the locomotive’s whistle is directly behind the chimney, and the cab sides are not square, but have one corner "cut off’. All this seems achievable by modification of a Black 5 model.

The Class 5 allocations to BR(S) were 73110-19 and 73080-89. They carried the names previously allocated to the King Arthur N15 class.

With favourable reports about the GBL model quality I decided to buy one. This time from Asda, which seems to be consistent in retailing the entire series to date (3 on the shelf when I visited on the day of publication).

It is a really good model and surprisingly heavy, which is due to the chassis and fixed driving wheels being a solid metal casting. The front bogie wheel/axle set are separate mouldings and turn!. The tender wheels do not turn.

Both the locomotive chassis and tender chassis are removable leaving hollow body shells, which means either a motorised tender or locomotive chassis might fit.

Even if I do not convert this model looking at it revives memories of a wonderful excursion behind 44932.

The most frustrating aspects of the GBL series models for the modeller is:

1. Differing assembly techniques - some have separate chassis making motorisation easier and some have moulded in chassis making conversion more difficult. (I know they are not intended for modeller conversion, which is surely a missed marketing opportunity).

2. Inconsistent manufacturing quality across the range.

Nevertheless I look forward to future Southern models, especially the Bulleid West Country, due in July I believe.

Friday 23 May 2014

My Dapol M7 derails on Peco N gauge setrack points

I struggled with this problem and judging by comments on other websites so have many others. The problem manifests when travelling bunker first through the curved side of the turnout. It either derails at the switch blade, or at the frog, or both.

When the bogie wheel meets the switch blade it rides up onto the top and falls off the other side (derail) and if it did not derail there then when it approaches the frog the wheel misses the guide rail taking the engine towards the other route through the frog (derail).

The cause does not lie with the turnout but with the M7 trailing bogie but, the solution requires modification to the turnout and M7.

There is some discussion elsewhere about the bogie swivel action being impeded by the electrical pick ups (this will not mean much to anyone who is unfamiliar with model) and/or insufficient weight over the bogie. But the truth is the bogie will go where the wheels take it.

The main causes are small wheel flange (does not always catch the guide rail), rocking motion of the axle (pivots on a spring that encourages the wheel to ride up any obstacle) and back to back wheel dimension.


1. Reset the back to back dimension of the bogie wheel set to 0.275" (7mm) or thereabouts. This is narrower than the standard for N gauge but the wide tread of the M7 ensures the engine stays on the track and passes through the turnout.

2. Ensure the electrical pick ups for the wheels stick out equally each side of the bogie chassis so that the axles sit central when installed.

3. Reduce the rocking motion of the axle with a slither of plastic the width of the slot and place between the axle and pivot spring. It still needs to rock a little or the axle rotation will cease up.

4. Stick a thin strip of plasticard 1 mm tall to the top of the guide rail on the curved side of the turnout. On the underside of the M7 next to the  inside face of the large driving wheels shave a little off the plastic bits that rise from the chassis there. Run the engine through the turnout by hand and file down the raised guide rail until there is no interference. Leave at least 0.5 mm of the raised portion. Photo shows the modification.

On one of the turnouts I had to add a new guide rail positioned just before the switch blade on the curved rail side.

5. Check the M7 and other rolling stock traverse the turnout without derailing or sticking. Adjust as necessary.

The M7 will now be much more reliable but the occasional derail may still occur as the light weight of the engine comes into play.

Monday 12 May 2014

My motor won't switch Peco N gauge turnout

I find this is a common problem for 00 and N gauge. If you build a capacitive discharge unit* to drive the point motor the usual remedy is to increase the charging capacitance, but that does not always work. After trying that I then made a serious error of judgement by increasing the input voltage, which blew the drive transistor!

The correct solution was to weaken the spring tension in the Peco turnout. On examining the N gauge turnout I could not see any built in method to achieve this. What needed to be done was to space out the two spring fixing points by sliding the sleepers on one side slightly away.

There is a web that joins the sleepers either side of the tie bar. Simply cut this where shown by the red arrow in the photo (both rails) and slide the sleepers on the right hand side away until the motor can move the switch blades fully home in both directions. The cut and adjustment can be done with the turnout in place.

Now that the sleepers are free they may need fixing with glue or pins to stop movement due to the remaining spring tension pushing them out further when the motor operates.

* search for circuit designs on the web or in electronics magazines.
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