The Di3.642 is part of the Di3b sub series. It was original built for the Finnish railways but taht order got cancelled. It was first leased by the NSB as 41.02 and subsequently bought in 1960 as Di3.642. The Di3b sub serie has the A1A-A1A wheel arrangement plus it is 30cm longer than the standard Di3. The Di3.642 was originally green but in the 1960's was painted brown in the colors that are known as gammel design. It stayed in these colors until 1986 was it was repainted in the new red colors (ny design).
On pictures from up to 1981 you can see the front door in the nose of cab 1 but in 1982 onwards that is gone. Also the stripe on the side of the locomotive was change in 1982. Because of this, I decided to model the Di3.642 in the version as it would be between 1982 and 1986.

The black and white photo is of the Di3.642 in 1984 in Åndalsnes and thanks to Emlio Crignola for sharing this. The color photo shows the Di3.642 on June 23th 1983 in Åndalsnes (Photo: Collection Lolke Bijlsma).

A good starting point is the Heljan model as the 623 is a long Di3 (the 602, 622, 623 and 641-643 were longer than the other models). I was able to get a shell of the Heljan Di3.622 in the gammel design color. This model was made by Heljan on behalf of NMJ in the early 2000's.
This page will describe making a model of the Di3.623 from this 622 shell.

The starting point is the Heljan model of the Di3.622. I was able to buy this second hand. This picture shows the model directly out of the box. It has all the extras already mounted so a lot of that was be removed for this project.

To remove the numbers I use Model Master thinner, as documented in other projects. Also the strip on the side door has to be removed.

The Heljan models have nose hand rails that are not painted. I decided to paint them. Also when removing the side stripe, some paint got damage. So I mask the model with just the hand rails visible as well. Also the doors are not masked. I used Tamiya TS-33 and after removing the masking tape it looks great.

The model got a new top coat using Tamiya TS-79, which gives it a satin/semi-gloss look. Just like the original Heljan model. Also visible in the picture are all the parts; buffers, hoses etc. They all got a sprayed flat black.

A Loksound 5 DCC decoder (ESU 58420) and iPhone 4S speaker are installed. An ESU Powerpack is installed in the diesel tank. For now I leave the lights as-is, eventually I will give this a LED conversion.

The end-result. A NSB Di3.642 in gammel design, as it ran from 1982 to 1986.