Part 2 – Bolting it together

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September ’09


With a set of frames put together, it was time to start test-fitting all the components that had been made. Here the Maxitrax coupler is fitted on with ten bolts- no chance of that falling off then! Also shown are the lifting hooks, but on the model these will be excellent for the securing of safety coupling chains. These bolts have been replaced by sockethead capscrews, using a socket or spanner proved very awkward due to the small size of these components.


Brackets had to be made up to fit the chassis frames together, here’s one we made earlier!

The height of the batteries required that the battery cradle be lowered by about 40mm down below the running plates in order to retain the low bonnet profile. A slight modification was made to those “L” shaped brackets (shortened) and a bit of angle iron dropped into place each side so it could accommodate two 85 A/hr leisure batteries. It was also imperative that there was adequate clearance remaining above the wheels (with the springs fully compressed) without being able to foul the
underside of the batteries or cradle.


Our theoretical wheel tread diameter worked out at 127mm, however the nearest option of available CNC cut wheels was 120mm, however when these arrived they were found to be just 117mm diameter. This now meant that other critical dimensions had to be checked and revised in light of this problem. Maintaining working/operating clearances needed extra detail.


The tops of the batteries also needed clearance under the cab windows to avoid touching the metal body work. The bonnet roof required the roof hoops to allow just enough clearance to avoid any potential nasty burns from inadvertently grounding out of the battery terminals! be warned!

(The inside of the bonnet tops will have 1.5mm plastic floor tiles affixed to give insulation of the metalwork).


Laser cut frame spaces, designed to also help support the battery cradle.


The completed battery cradle, seen far end of the loco. A coat of primer has been applied in this shot to stop any rusting.

With the frames together and battery cradles sorted, its time to look at installing the wheels and gearing to check that it all fits together as planned. Below is a shot of a bearing unit with spring installed; to the side are the laser cut packing strips which are yet to be drilled and bolted to the support hole above them. They are held at the bottom by a sockethead capscrew, not shown, which also retains the bearing.


When installed, the springs are compressed a few millimetres; this gives the setup a degree of rigidity- it cannot be too springy or the loco may re-bound off the track on any bumpy bits. In the photo above, it became clear that the compression would be too much, so a bit of trimming was required.


A Bosch 750w motor was borrowed from one of Mike’s Class 04 projects to check out the gearing alignment. It all fitted in nicely, almost!

The frames needed a bit welding on at the top for the upright bearing, which holds the first driveshaft and the first set of reduction gears – this is fixed at the bottom and the top will be able to move an inch in a slot cut in the frame. This allows both chains – one to the motor, one to the jackshaft axle – to be tensioned, and then the bearing bolted up tight to the frame to keep the tension.

xtra_adjustable bearings

Motor mounting blocks were made from more scrap sports equipment, that large box section again. The moveable bearings can be seen poking above the frames in this photo.


A bit of grey paint has been applied by the time this photo was taken and that little piece needed for the moveable bearing had been welded on and is seen here on test, the moving bit is held temporarily by a large crossheaded screw. The arc’d slot needed for the movement has been extended slightly since this shot was taken. Below, the bushes made for these adjustable bearings – also my first lathe exercise! Quite pleased I am…


The motor mountings are also adjustable, and can be slid forward or back to suit. Total movement is about 1 inch, this should help with keeping chains taut.


Bit dark but in this shot you can see all the gear and motor arrangement.

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