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Converting Your Cemflo to P4 With Mike Ainsworth

Converting Your Cemflo to P4 With Mike Ainsworth

Welcome to our latest instalment of our "Let's Get Involved" series. In this feature, Mike Ainsworth of the Scalefour Society converts one our cemflo wagons to P4! Take it away, Mike...

This tutorial is intended to run you through the steps needed to convert the Accurascale Cemflo to P4 standards.  The same approach will, I think, work equally in EM but I can’t claim to have tried it myself.  So what follows is based entirely around a conversion to P4.

It’s worth saying at the start that, because the axles usually used in P4 are a little longer than the Accurascale ones, the work involves slightly more than simply dropping out the OO wheels and clipping P4 ones in their place.  On the other hand, it’s not a difficult job and, of course, you do get a very nice P4 PCV at the end of it.

Before getting to work, a word about tools.  And the good news is that nothing very exotic is needed.  Some sort of holder is useful so that the wagon can be supported upside down without damaging the bodywork detail.  Something like the Peco loco servicing cradle will do the trick.  Beyond that, you will need nothing more than a flat needle file (preferably a reasonably coarse one, at least by needle file standards), a P4 back-to-back gauge and a small jeweller’s or electrician’s screwdriver.  You might also need two pairs of reasonably beefy pliers.  That might sound a bit alarming for what is supposed to be a finescale modelling job but we’ll come to that a little later.  Materials-wise, all you’ll need are two sets of P4 3-hole wagon wheels.  All this is illustrated in the photo below.


The first job is to remove the factory-fitted couplings.  There is no reason why they can’t be used in P4, though the replacement screw couplings supplied with the wagons certainly look better.  The original ones can be refitted later anyway if that’s your preference but, for now, having them out of the way makes the job marginally easier.  To remove them, simply insert your screwdriver between the coupling and its mounting block and prise the coupling upwards – see the photo below.  The coupling will come away easily enough.  Store it somewhere safe if you intend to reuse it later.


Turning to the wheels, the OO ones can be removed by gently bending the w-irons outwards using either the screwdriver or your thumbnail.  The wheels can then be popped out.  You’ll need to be careful at this stage not to damage any of the underframe detailing.  The brake safety loops are especially vulnerable but it isn’t a disaster if any of them should come adrift;  they can easily be reattached, though you might need to redrill one or both mounting holes with a fine drill first.

Because – obviously - the replacement wheels are spaced further apart than the Accurascale originals, we now need to create a little more room for them.  We do that by filing away the part of the inside of the W-iron that I’ve painted white in the picture below. 

It’s a simple enough job using the flat file and taking it easy.  Keep filing until you have a flat surface on the inside of the w-iron.  Handily, it’s easy to tell when you’ve gone far enough.  The underframe is painted black but is moulded in grey plastic so, once the vertical reinforcements on the back of the w-iron turn grey – see below – and you’ve given the other three w-irons the same treatment, you can put the file away. 

What you will probably find is that the axle holes are now full of plastic filings which we need to get rid of if the wheels are to run freely.  An old darning needle or a sharp cocktail stick will remove the filings but don’t be tempted to use a drill – you will almost certainly end up deepening or enlarging the hole or both.

 Now for the wheels.  Although the difference in axle length might not look much – the P4 ones are typically about a millimetre longer than Accuracale’s – that’s enough to stop them rotating freely.  And there’s no straightforward way of either deepening the bearing holes or shortening the P4 axles.  So the simplest solution is to fit the new wheels to the Accurascale axles.

That might sound like a daunting prospect but it really isn’t difficult.  The procedure is, first, to remove the OO wheels from their axles.  You might be able to twist them off using nothing more than your fingers and a bit of brute force but, if not, this is where the pliers come in.  You can afford to be pretty brutal with the wheels themselves because we won’t be needing them again.  The axles, on the other hand, are being reused so do need to be treated with a bit more respect.  Similarly, the wheels need to come off the P4 axles although in this case it’s the wheels rather than the axles that need to be handled with a bit of care.

Next, the P4 wheels need to be mounted on the Accurascale axles so thread the wheels onto the axle and check the spacing with the back to back gauge.  You need to ensure that the same length of axle protrudes at either end.  I find I can judge that as accurately by eye as by measurement.  It will look as though very little of the axle is visible on the outside of the wheels but trust me, if you filed away enough plastic earlier, it will work !

At this stage it might look as though you’ve hit a major snag.  Both Accurascale and P4 wheels are mounted on what are nominally 2mm diameter axles but manufacturing tolerances mean there is inevitably some variation.  I’ve found that this sometimes means that P4 wheels are a sliding rather than a tight fit on the Accurascale axles – which is no help at all.  Luckily, there is a simple solution if you should run into the same problem.   Apply a smear of epoxy or superglue to the inside of the wheel where it meets the axle and leave the back-to-back gauge in place while the glue as per below.


All that remains, once the glue has set, is to clip the P4 wheels back into place and check that they rotate freely.  If they don’t, the most likely cause is that the wheels are off-centre on their axles.  There isn’t much margin for error but, if there should be a problem, the good news is that it’s fairly easy to break the glue bond between wheel and axle and have another go.

Finally, weight.  As they come out of the box, the wagons weigh in at around 40g.  That’s a bit on the light side for a P4 wagon, especially one with no compensation or springing.  But weight can be added invisibly inside the tank – which, handily, can be removed from the wagon chassis quite simply.  There’s a moulded pipe which runs along the lower edge of the tank on both sides and which has a discharge valve half way along.  The valve doubles up as a clip holding the tank and chassis together.  Ease this gently away from the solebar and the tank and chassis will separate. 

It’s then a simple matter of adding as much weight as you like inside the tank.  I suggest an all-up weight of around 55 to 60g.  And the great thing is that with plenty of space to put it and the fact that it’s completely hidden once the tank is replaced, it’s a good opportunity to use up any old bits of whitemetal, lead, or any other bits you happen to have lying around.

And that’s about it.  Either the tension lock couplings can be refitted or the screw link ones substituted for them and it’s job done.  Only 29 more to go for a typical Cliffe to Uddingston train!

Thanks to Mike for an informative guide on converting our cemflos to P4! If you wish to do the same and build a train of 'Silver Queens' for your layout, you can order the cemflos here

Would you like to submit a modelling article for "Let's Get Involved" featuring some Accurascale models? email us at with your suggestions! 

Mike Ainsworth is the Secretary of the Scalefour Society

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