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Author Topic: Dapol - Class 121  (Read 36846 times)

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Offline jamespetts

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Re: Dapol - Class 121
« Reply #150 on: February 17, 2020, 11:46:47 AM »
Halfords white plastic bumper primer is my go to spray for priming

Interesting, thank you. How does it compare to modelling specific primers such as those from Phoenix Precision or Tamiya?
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Re: Dapol - Class 121
« Reply #151 on: February 17, 2020, 11:50:34 AM »
The only primers I use are the Halfords rattle can type, so I can not compare with anything else, but I have never had a problem with the Halfords stuff.
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Re: Dapol - Class 121
« Reply #152 on: February 17, 2020, 11:56:31 AM »
Modelling primers imo are just a name you pay more money for for less



Offline Sven

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Re: Dapol - Class 121
« Reply #153 on: February 17, 2020, 11:59:39 AM »
I'm also using only Halfords primers. Take note: they have small and a large cans. Take the large.
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Offline jamespetts

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Re: Dapol - Class 121
« Reply #154 on: February 19, 2020, 11:48:09 PM »
Sandpaper seems to have been effective at flattening the area to allow me to have another go at painting, this time with white rather than grey primer:

Dapol Class 121 by James Petts, on Flickr

However, testing shows that I have not eliminated the light:

Dapol Class 121 by James Petts, on Flickr

I think that I will have to disconnect it electrically. However, I have had to abandon that for this evening as the battery on my multimeter has run out, and I cannot otherwise test which wire(s) to cut.

If anyone knows which wire(s) deal only with the high intensity headlights, that would be very helpful. Also, any disassembly instructions would be most helpful, as I note that I seem to have severed the wires leading to the bogie pick-ups at one end.

My white primer has not arrived yet, so, even if it were not for the light issue, I should not have been able to progress this this evening.
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Offline Steven B

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Re: Dapol - Class 121
« Reply #155 on: February 20, 2020, 09:21:26 AM »
Can you remove the section of light-pipe that provides light to the main headlamp? If you can't cut the pipe from behind you may need to drill it out and add more filler.

Otherwise, painting over it in black before applying the white primer might work.

Steven B.

Offline jamespetts

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Re: Dapol - Class 121
« Reply #156 on: February 20, 2020, 12:21:29 PM »
Can you remove the section of light-pipe that provides light to the main headlamp? If you can't cut the pipe from behind you may need to drill it out and add more filler.

Otherwise, painting over it in black before applying the white primer might work.

Steven B.

The light pipe inside the cab is not easy to discern and is covered with a black layer, soldered wires and what looks like a diode (or possibly surface mount resistor) at one point. The whole thing looks like a specially shaped solid block. It does not appear possible to remove the light pipe specifically for the centre light. However, the centre light is brighter and less yellow than the others, so this is probably a separate LED; cutting the right wire would be the better thing to do if possible.
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Offline jamespetts

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Re: Dapol - Class 121
« Reply #157 on: February 23, 2020, 10:45:56 PM »
I disassembled the unit after some useful advice from a fellow club member, but found that the end LEDs are in a completely sealed block. There are only three wires that go to the block, so there is no wire that can be cut affecting only the high intensity LEDs.

I have, however, managed to destroy the high intensity LED by drilling further into the block. The necessary technique seems to be to keep drilling into the high-intensity headlight until it ceases to function: this needs to be tested with a DC track supply at regular intervals during the drilling. With this technique, it should not be necessary to disassemble the unit fully. This does not affect the operation of the side headlights or tail lights.

I have then masked the unit aside from the cab (masking the windows and black surrounds with Maskol) and spray painted primer and (so far) one coat of yellow. I anticipate needing another 1-2 coats of the yellow paint.

Here is a picture of it so far, although it is possibly not easy to discern the cab ends from this:

One of these things is not like the others. by James Petts, on Flickr

(This is next to some larger scale carriages for a club layout that I took the opportunity to paint whilst the Bench Vent was out).
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Offline Ted

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Re: Dapol - Class 121
« Reply #158 on: February 25, 2020, 12:55:31 PM »
Modelling primers imo are just a name you pay more money for for less

You might find this interesting!


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Re: Dapol - Class 121
« Reply #159 on: March 09, 2020, 12:18:05 AM »
More progress on this project. I have now managed to disassemble the unit and spray paint the cabs starting with a primer and then multiple coats of Railmatch yellow:

Dapol 121 backdating in progress by James Petts, on Flickr

Dapol 121 backdating in progress by James Petts, on Flickr

Getting the border between the repainted and non-repainted areas to look good was not easy:

Dapol 121 backdating in progress by James Petts, on Flickr

Dapol 121 backdating in progress by James Petts, on Flickr

The problem is that there is a difference in height of the new paint and the old layer of paint and that it is very difficult to mask with precision.

If I had not used primer, this might have been much easier, as I could have rubbed away the paint on the affected areas until I achieved a smooth transition; however, because of the primer, any rubbing away simply revealed the white underneath. I used a cocktail stick to tidy up the areas around the windows, with passable results (from a distance):

Dapol 121 ( before and after) by James Petts, on Flickr

Dapol 121 (before and after) by James Petts, on Flickr

Dapol 121 (before and after) by James Petts, on Flickr

I did have to touch up the areas where white had shown through using a brush. It does look a little better than this at normal viewing distances, but this does not really have the quality of appearance of the units from the factory.

I might be able to refine the appearance slightly with practice (although I only have two more units left to do, one already with custom decals, and these are no longer easily available), but there is now the difficult decision as to whether leaving the high intensity headlight in tact will look more or less wrong on the other units than this somewhat sub-optimal paint job.

I will have to consider this carefully before renumbering and applying decals.
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Offline njee20

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Re: Dapol - Class 121
« Reply #160 on: March 09, 2020, 07:51:23 AM »
You know how people on here and RMWeb have been telling you that using aerosols on tiny areas of N gauge models isnít ideal...? Yeah. That.

Itís another problem with yellow, because you need lots of coats, so you end up laying down lots of coats of thick paint, and end up with this effect. Itís going to be very tough to totally retrieve that, as youíd really want to strip it, rather than sanding it back, and thatíll destroy the underlying and/or body side finish.

+another vote for Halfords primer FWIW. Better, more even coverage than anything model specific.
« Last Edit: March 09, 2020, 07:52:33 AM by njee20 »

Offline Ted

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Re: Dapol - Class 121
« Reply #161 on: March 09, 2020, 08:50:45 AM »
You can get away with spray cans for primer, but they have to be used at distance in a warm environment - can heated to room temp or higher. You need as fine a mist as you can get.

Then you need an ultra fine wet n dry sand to take away the orange peel / pitting and any visible texturing of the paint. It will be there.

That said, I'd never, ever used a rattle can for actual painting!

As you've found out it will ruin your model.

It's just not designed for the job. The finish looks crap on 00, let alone N gauge.

You could try removing your paint with patience, but it will be tricky. You might be better off with very a tiny piece of fine grit (>1500) wet n dry, the work the cab surfaces smooth.

Offline jamespetts

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Re: Dapol - Class 121
« Reply #162 on: March 09, 2020, 05:41:35 PM »
Thank you for your responses. The photographs exaggerate the coarseness of the surface of the model as modified, which looks more acceptable at ordinary viewing distances, but the appearance is not ideal. I do not consider this entirely ruined, as, with some transfers, this will look passable at normal distances, but this is not as refined as the model as supplied by Dapol.

I could live with the slightly coarser texture of the paint itself, which is only really apparent on very close inspection (or close-up photographs such as these), but the real difficulty is in the boundary between this paint and the remaining areas.

This is caused by the number of layers of paint necessary to cover an area without the colour below showing through. The real problem is that, in rubbing down enough to flatten the filler, the black colour of the underlying plastic is revealed, and a single coat of primer was not sufficient to cover this such that it did not show through to darken the yellow above.

I do not imagine that airbrushing the ends rather than using an aerosol would affect this fundamental difficulty, and brush painting would give too crude a finish, so I cannot see a solution to this problem other than stripping and totally repainting the entire unit, which is further than I want to (and have the skills) to go.

The only remaining query is whether spray priming and then brushing (with multiple dilute coats) just the lower part of the central panel might give an acceptable effect.

As it stands, I may just have to live with the class 121s having high intensity headlights appended to the units in a timewarp from 1993 back to the 1989 in which my layout is set.
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