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AEI Class 81




This post is a record of how I motorised my AEI class 81 by Atlas Editions.


I bought my model from a seller in Hong Kong ... the cost was under £20, including postage to the UK. The model is intended for static display, and comes on a plinth:


The prototype has a bogie wheelbase of 10' 6", this is quite long by British standards:


My project started with a topic on the RMWeb, where I asked about possible chassis. From a reply here I bought a Hornby class 67 as the donor model - the bogie wheelbase of a 4mm scale class 67 is spot-on for a 1:87 scale class 81.


I used only the bogies, motor and cardan shafts from the Hornby donor. I could have bought these as spare parts for much the same outlay, and really the only reason to buy a complete model was to check the feasibility of the project. It would be easier to sell on a complete model if I decided to give up.


I built a new chassis to hold the motor and the two bogies. I began with a piece of styrene sheet, cut to be a snug fit inside the bottom of the body. I cut a rectangular hole and added a panel underneath to hold the motor, this lets the two drive shafts sit fairly level:


I trimmed the drive shafts to length before taking this photo. The drive shafts are in two telescopic parts and are made from plastic, so shortening them is straightforward. The method is to attach the parts to their respective universal joints, put the bogies and motor into the chassis, and look where to trim the drive shafts. Then cut to length with a razor saw.


This chassis ran well on test - well enough to let me commit to the build. But if I was doing this project again, I would move the bogies about 2 mm closer together, that is 1 mm inwards at each end. This would make sure they cannot foul the insides of the buffer beams on sharp curves.


The body shell is almost unchanged for this project. I cut off the two cylindrical bosses (not in the photos but obvious when you dismantle a model) and  added two long strips of styrene to hold the whole moulding level on its new chassis. The strips are recessed inside the body by a distance equal to the thickness of the chassis:


So the model now looked like this:


The next stage was to swap the bogie sides from Hornby for the ones from Atlas Editions. The Hornby sides are part of the moulding holding the wheels in place. I took one of these mouldings off and wished I hadn't when I came to put it back; it is easier to do the cutting with the sides in position. I left the solid plastic cylinders on the bogie to provide somewhere to attach the new sideframes.


Similarly I cut off the Atlas sideframes flush with their bogies, this left me two prongs to fix the sideframes in place. Here are two bogies, with the old and new sideframes:


It is important to glue the new sideframes on the right way round. Everything is black and looks fairly nondescript, but the cab steps need to be on the outer ends of the bogies so they end up under the cab doors. It is good how solvent sets slowly.


There is an option with the positioning of the new sideframes. If you want to keep the Hornby sideplay (as I did), the frames need to go on about 0.5 mm outside their prototypical locations. This will make sure the wheels do not rub on the frames. Alternatively, you could add some shim washers to remove the sideplay and the fix the frames in their 'scale' locations.


I used two different methods to make up the extra millimetre. The bogie on the left has the cross-piece between the sideframes re-set 0.5 mm inboard at each end. This keeps the guard irons in line with the rails but the corners of the assembly are a bit fragile. The bogie on the right has the cross-piece cut and a scrap of 1mm styrene glued in, reinforced with styrene on the inside. This is stronger but the guard irons are now a little too far apart:


With the bogies complete I returned to the chassis and added the buffer beams from the Atlas model. I cut these to give me a tab to glue them onto the chassis, then built up the chassis to set them at the correct height and glued them on with cyanoacrylate:


One buffer beam will have a dummy 'scale' coupler and the other will have a Kadee. I attached the Kadee with a M2 screw right through the buffer beam casting and the chassis, so hopefully it is strong enough to pull a train:


There is no room to fit the usual draft gear box for a Kadee, the bogies take up too much space. Here is the chassis on my home-made jig for checking the heights of Kadees:


I added some deep sides to keep the chassis straight and flat under the weight of the motor:


These sides are angled inwards to make sure the body will still go on if I add any reinforcement outside them at their top edges.


The motor gets equal and opposite torque reactions from the two bogies, so it only needs fixings sufficiently strong to hold it if I turn the model upside down. I put a couple of tiny dabs of cyanoacrylate to hold the motor, so I can prise it out if a repair is ever needed.


The underframe details went on next. I pulled these off the Atlas model and fixed them on with Carr's Butanone. For some reason, Plastic Weld would not hold them. When you fix on the underframe parts, you have to decide which end of the model will be number 1 end and number 2 end. For a modified class 81 like this with air tanks on the roof, the air tanks are at the number 1 end, and the pantograph is at number 2 end.


I was a bit ambitious here. I had to pull some of these details off to let the model run round the radius 2 curves on my layout.


I gave the chassis a brisk undercoat of Halfords grey primer to hide the worst aspects of my model making, and then some Volvo Dark Grey for the black parts:


Then the decoder went in:


I added some weight above the bogies to give the driving wheels some extra friction to overcome. I used some pieces of sheet lead, about 45 grams in all:


Finally I put the body onto the chassis and posed the model on the scenic part of my layout:


Having done this, Matthew ('LMS_LNER_SR_GWR_fan2004') suggested the model would look better with a replacement pantograph, and I added the top part of a Sommerfeldt type 965:


The buffer heads received some paint too.


I have left the body loose on the chassis for the time being, it is quite a snug fit. I want to stop now and enjoy the model on the layout.


The engine runs really well, but the clearances between the bogies and the insides of the buffer beam castings are very tight on every curve. I wish I had put the bogies a little closer together, and I will do this if I ever make another one.


With thanks also to 'CloggyDog', 'Enterprisingwestern' and 'BernardTPM' for their help and encouragement through this project.

Edited by 47137
Edit to add entry category

  • Like 5
  • Craftsmanship/clever 4


Recommended Comments

  • RMweb Gold

That's wonderful!


Did Atlas Editions do anything else in HO? I always thought their locos were all 1:100 scale. 

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  • RMweb Gold

Ian - thank you for your kind words!


Atlas Editions have done a few British trams in H0. I saw some of these at a show a few weeks ago, but not the class 81. There are some 00 models too and they are so cheap it might be worth a try as a cut and shut sort of project. They would be good for practising painting skills. I wonder where the class 81 came from - it seems to be true to 1:87 scale. I wish they could try a class 37, this suits so many periods.

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I agree, that is amazing!


Would this model look good alongside a Hornby 86 or 87 and have you thought about adding a Sommerfeldt pantograph and working lights? Rob at express models can do a custom one for you if your interested?


Best regards, Matthew

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  • RMweb Gold

Do remember this is 1:87 scale ... so it will look too small beside a Hornby model. However a 1:76 scale or custom-made pantograph might look rather good - certainly better than the moulded original. This is the weakest part of the model.


I have decided against lights because they were "marker lights" rather than "headlights" and so rather dim; and also extremely difficult to fit because they are higher up the body than the control desks in the cabs. See http://www.rmweb.co.uk/community/index.php?/topic/138881-atlas-editions-class-81-project-187-scale/?p=3374090


I think the nicest thing about this project is the lack of any painting on the body. The only paint needed is to tidy up the black on the underframe. Painting is where I usually go wrong.

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I understand about the lights and a good pantograph would be Sommerfeldt 965. It’s 1:87 scale as well so I will look fine. I am still tempted by this though because I have a piko ho ice 3 which looks fine against my other stock. I agree with the painting though, I hate it too so it’s nice to see a project whiteout so much.


Best regards, Matthew

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Here’s another tip, if you really wanted to you could make your own legs for the pantograph using strips of plasticard and some Sommerfeldt insulators. Just a suggestion though.

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  • RMweb Gold

I've changed the photo of the pantograph to include the roof detail. The Atlas insulators are quite neatly moulded and I think it is best to keep them - I would really need to change the ones along the roof to match.

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