Locomotion Models Improved Precedent P4 Conversion

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barrowroad
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Locomotion Models Improved Precedent P4 Conversion

Postby barrowroad » Wed Aug 10, 2022 2:55 pm

Locomotion Models the NRM and Bachmann produced a model of the LNWR Improved Precedent Class 2-4-0 790 'Hardwicke' a while ago and I have been asked by my good friend David Clarke if it is possible to convert it to P4.

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Opening the box I decided to take a look at the engine first so put the tender to one side.

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Looking at the instructions that come with the model I undid the various screws to remove the body from the chassis carefully placing them in a plastic takeaway box I use for safe storage of components.

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A further 4 small screws were removed and I ended up with the footplate, the smokebox/boiler/cab unit and a pair of cast weight the latter fell out from recesses behind each cab side plate.

Working on the basis of previous experience P4 wheelsets need a clearance of at least 22.00mm over the footplate and splashers so my next task was to take the appropriate measurements on this model.
The front splashers proved to be too narrow at 21.50mm whilst the rear, across the faces of the two cast metal weights, was 22.40mm.
The clearances were very tight so before carrying out any work on widening the clearance I decided to work on the chassis and swap the wheels to a set of Gibsons provided by David, For reference these are Driving wheels 6'9" 20 spoke; Leading 3'9" 10 spoke and tender 3'9" 10 spoke.

The chassis looks like this after conversion.

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To do the conversion first remove the 3 keeper plate screws and detach the plate. This is made easier with the electrical contact from the wheels pickups being made against a pcb plate contained in the base of the chassis block. Carefully remove the wheels. I also removed the paired brake blocks for safety. These are push fit onto pins on the chassis.
The axles on this model are 3mm diameter and the AG wheels provides by David were 1/8in so I had to ream out the four axle bushes. I found the easiest way to hold these bushes was to place them, one at a time into the slots in the chassis.
Next task was to remove the nylon gear wheel from the front driver axle. I do this by laying one of the wheels across the top of the jaws of my bench vice and tap out the axle from the wheels.
Next use the same procedure to tap out the axle from the gear wheel. Be sure you make a note of the orientation of the gear in relation to the gears still in the chassis. Take measurements to ensure the gear is in the correct position when fitted to the new P4 axle.
First I needed to ream out the this gearwheel to 1/8in/
The width of the chassis is 11.43mm. Back to back is 17.78mm. There is a 0.5mm boss on the rear of the wheels so I need washers to take up the space between the rear of each wheel and the chassis face. This works out at 2.5mm each side or 2 x 1mm and 1 x 0.5mm brass washers as supplied by Alan Gibson. You can see these in one of the photos.
Coupling rods are next on the list. I reused the original set inserting AG bushes and then opening out the holes to 1.65mm to fit the Gibson Crankpins on the wheels. The crankpin nuts will need to be thinned to fit behind the splashers.

Returning to the footplate a trial fit over the wheels shows that some metal needs removing along the inside edge in order to get it to fit.

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I have used a small file to gradually remove metal on the inner edge of the footplate until the width of the footplate is just under 3mm.
Note a small amount has been removed from the leading edge of each splasher to give better clearance for the crankpins.

Another trial fit of the body revealed some metal needed to be removed from the castings inside the cab in order to clear the tops of the drivers.
This was achieved by placing each casting in my vice and carefully and slowly removing material using a dremel fitted with a grinding disk.
Note please use safety googles and angle the disk away from you when doing this job.

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The pair can then be fixed in position using a dab of evostick.

The front splasher are next on the list. The clearance here is very tight. To remove them use a small srewdriver to lever off the point of attachment where the frame extension meets the base of the smokebox. Be very careful here as they are held in position by 2 x 0.8mm plastic lugs which fit into the metal behind. They might have a bit of glue as well. Once removed I decided to thin the rear of each splasher to 0.5mm to give more clearance for the front driver. This I achieved by using a scalpel to carefully scrap away plastic until the 0.5mm was achieved.

IMG_20220810_101218467.jpg


Finally after testing the clearances I refitted the body to the chassis.

IMG_20220810_125856371.jpg


Next instalment will be the tender conversion.

triumph3
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby triumph3 » Wed Aug 10, 2022 4:03 pm

Robin,
Absolutely fabulous!

David

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jon price
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby jon price » Wed Aug 10, 2022 4:50 pm

Very helpful details. I was going to approach the conversion of my own (currently Lucknow) one of these with trepidation. Now I can sail in fully confident in the knowledge that if I screw it up it is because I didn't follow your very clear information.
Connah's Quay Workshop threads: viewforum.php?f=125

triumph3
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby triumph3 » Wed Aug 10, 2022 7:51 pm

YouChoos do a specific DCC sound chip based on the sound file used on the Coal Tank chip they do for the Bachmann Coal Tank.

David

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barrowroad
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby barrowroad » Thu Aug 11, 2022 3:08 pm

Part 2 - the Tender.....

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First remove the OO wheels then the two very small screws at either side of the rear of the tender chassis. Store safely.

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You can now lift off the body from the chassis. This reveals the pcb board for a 21 pin decoder, sound or plain version. Underneath is a speaker which comes with the model. To remove the coupling unscrew the plate above it, remove and place to one side. You can now remove the coupling. Refit the plate and board.

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Now carefully remove the brake gear. I used a small screwdriver to very gently prize the three fixings away from their mounting points. Store safely.

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Now measure the distance between the pairs of holes for the three axles. You will find the distance is too narrow for P4.
The solution is to use a craft knife to pair back the raised thicker plastic until it is flush with the inside of the tender frames. This gives extra space. However with the 3'9" AG tender wheels I have used you will also need to file the front centre boss flush with the face of the tyre.
Now make up the three sets of wheels and axles.

I decided to fit pin point axles and so suitable brass bearings need to be fitted. To do this the existing bearing holes need to be opened out to fit the bearing. I used the tool I have for converting RTR wagons to P4. see photo.

IMG_20220811_120946096.jpg


Carefully file the point off the bearing to shorten the length and put a dab of evostick into the hole to secure the bearing. Do a pair at a time and use a spare pin point axle to hold them in position whilst checking the axle is square and level.
Repeat for the other two axles.


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Now fit the front and rear wheel sets and set the pickups onto the back of the wheels. To achieve this use a pair of flat nose tweezers to grip and bend the phospher bronze strip through 90deg and adjust to touch the back of each wheel tyre.

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Now refit the brake gear and temporarily fit the body.

Finally fit the middle wheels set and place on the track for a test run.

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I have not refitted the screws yet as I am waiting on delivery of a sound decoder.

Philip Hall
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby Philip Hall » Thu Aug 11, 2022 5:18 pm

Robin, this is an excellent tutorial outlining your very methodical way of conversions. As you show, taking it easily and carefully will give ways around all the inevitable complications and although I've done many different conversions, I've learned a few new things here and in your past posts.

Clearance for wheels is always the big issue, especially lately where some models just don't have the room for P4 wheelsets. On a few engines I have resolved this by reducing the width of the driving wheel tyres. For example, on the Hornby LSWR 700 class the rear splashers and cab side are (already very thin) die-castings, and I doubted I could obtain any more clearance without damage. So I took the tyres off the Gibson wheels and thinned the face down as much as I dared, and got them down to 1.8mm, just a shade under the 'scale' dimension of 1.85mm. I used the lathe to start with, but found that mounting the tyre for turning was difficult, so I took a no 6 cut 6" file and took a few strokes off the face, rotating the tyre a quarter at a time. Once I got down to about 1.85mm, which is really close to breaking through the front face of the tyre, spinning the finished wheel in the lathe whilst checking for truth polishes the front face nicely. I have to say that I only did this on the rear wheels, the front two sets had bags of clearance and you can't see the difference!

I have also turned down some Dapol B4 wheels recently to 1.7mm wide to gain clearance behind the crossheads, 1.85mm at the rear. It does work and the wheels don't drop into the flangeways. And I haven't used a Society form tool either...

Do keep up the good work.

Philip

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barrowroad
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby barrowroad » Sat Aug 13, 2022 2:06 pm

Thanks for your kind comments chaps.

A test run using dc on my layout showed an issue of shorting on curves and derailment of the front wheels of the loco.

To resolve the latter I removed the 0.25mm washers on the 2mm axle so there are now 2 x1mm washers either side. [ I forgot to mention the front axle was 2.25mm each side and the two driving axles 2.5mm ]. This seems to have cured the problem.
As for the shorting I have smeared a very thin layer of araldite on the inside edge of the footplate where I filed off metal in order to add some insulation. I also decided to further thin the two castings behind the cab sides to 0.7mm from 0.9mm. This was to give some extra clearance but also to allow me to fix a piece of black electrical tape to provide more insulation in this area.

IMG_20220813_120622214.jpg


Result.....
Now for the sound decoder to arrive...

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jon price
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby jon price » Sat Aug 13, 2022 9:17 pm

Thinning the cabside castings to a fraction of a millimeter thick seems a lot of work to be left with almost nothing. Are the cabside castings simply present to provide weight? If so can they be cut completely out of the offending areas, and weight added at other points?
Connah's Quay Workshop threads: viewforum.php?f=125

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barrowroad
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby barrowroad » Sun Aug 14, 2022 12:08 pm

Hi Jon, the weights are obviously in that position to add weight over the rear drivers so I decided to keep and thin them as there is little space to add extra weight elsewhere. The loco s fairly heavy anyway as Bachmann have filled the available space already. I was contemplating leaving them out at one point but I'm a glutton for punishment :)

Robin

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jon price
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby jon price » Sun Aug 14, 2022 1:22 pm

:lol:
Connah's Quay Workshop threads: viewforum.php?f=125

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barrowroad
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby barrowroad » Fri Aug 19, 2022 11:55 am

After some further testing I have decided to leave out the cabside weights.

The sound decoder arrived earlier in the week and is now fitted.

Here is a video of a test run of the model.


triumph3
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby triumph3 » Mon Aug 22, 2022 12:51 pm

Robin,
Excellent work, I hope it persuades other people to convert both the NRM model and the sister models by Rails of Sheffield ( 3 different versions including in LMS lined red and LMS black) into P4.

When the loco is back with me the white cab roof is being painted black, when it ran in the 1980s it had a black cab roof but since being a museum piece it has been give a white roof.

David

triumph3
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby triumph3 » Tue Aug 30, 2022 2:32 pm

Having now had Hardwick back from Robin, I have carried out a few small jobs on the loco. The most prominent being painting the white cab roof a satin black. I can find no photos showing the loco with a white roof, I think it was done when the loco (not in steam) did a tour of the UK with a set of Royal Saloons in the 1980s. I have also added front and rear couplings, but not the ones Bachmann supplied, the coup[ling hook was huge so this has been replaced by a Hornby one and I made up an old PC screw link coupling for the tender. I also added the front vac pipe. I then put real coal in the tender. having taken some photos, it needs more coal and bigger lumps! The most glaring omission is the absence of any crew, very noticeable with such an open cab.

An excellent job done by Robin, the exchange was me weathering 2 of his locos.

David
IMG_4701 (2).JPG

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Horsetan
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby Horsetan » Fri Sep 16, 2022 10:07 pm

Philip Hall wrote:....Clearance for wheels is always the big issue, especially lately where some models just don't have the room for P4 wheelsets.....


I wonder if this is deliberately done to make them impossible to mess about with?
That would be an ecumenical matter.

triumph3
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Re: Locomotion Models Improved Precedent P4 Conversion

Postby triumph3 » Sat Sep 24, 2022 2:38 pm

Spoke to Locomotion Models at Stafford Show and they said they still have stock of Hardwick, so buy now!

David


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