I only saw a few class 81s on a couple of visits to Euston but I’ve always liked the original AC electrics and have wanted to model an 81 alongside my RTR 85, 86 and 87 models. I found that CMAC make a 3D print of the 81 (amongst others) that can be purchased via eBay. I used this with a donor Bachmann class 85 to make a working class 81. This blog summarises how I did it.
What you get in the kit, with the key parts from the donor 85 alongside:
The chassis block needs openings for the working bogies. These were opened out by chain drilling and then filing to match the profile of the class 85 chassis. This was then attached to the chassis block using bolts and epoxy glue, having fitted the motor into the block first.
The 3D printed bogie sides come with a centre bearing. This was removed and the centre was opened out to be a good fit to the bachmann bogie gear towers. The gear towers were then attached to the chassis block, with the cardan shafts connected to the motor. With the chassis upside down the sides were glued with epoxy to the gear towers and spacers were placed to ensure they dried in the right location.
The mechanism was tested at various stages through this process. Once the sides were dry and everything was working and wired back up plasticard was used to add some basic protection to the bottom of the gears. With the chassis completed the body was cleaned up and painted. BR blue is a fairly simple livery to do. The lights were drilled out to accept LEDs. The marker lights are with hindsight a little too large.
With the body painted and wired it was time to put the body and chassis back together. The cab interiors fitted well, held in place with some black tack. However there was a lug each side of the chassis block designed to support the cabs that stuck out too far and clashed with the new body. All 4 of these lugs had to be cut back with a dremel. It’s a shame I didn’t spot this earlier, as it required some disassembly to do it.
Glazing is a mixture of clear plastic and re-using the class 85 windows. The pantograph is from the class 85. The body and chassis are held together with black tack and spot of Evostick. Final details were added and the loco went into service after running in.
Conclusion: It runs well and looks like a class 81, giving me an unusual model not available elsewhere. I don’t like the fine lines you get with 3D printing and even after several goes at filing, sanding and priming they are still visible if you look closely, but from normal viewing distances it’s a good looking model of an 81. I should have used smaller LEDs for the red marker lights instead of the 2mm ones I had in stock.