Locomotion Models Improved Precedent P4 Conversion
Posted: 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.
Opening the box I decided to take a look at the engine first so put the tender to one side.
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.
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.
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.
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.
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.
Finally after testing the clearances I refitted the body to the chassis.
Next instalment will be the tender conversion.
Opening the box I decided to take a look at the engine first so put the tender to one side.
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.
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.
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.
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.
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.
Finally after testing the clearances I refitted the body to the chassis.
Next instalment will be the tender conversion.