JESSOP & APPLEBY STEAM CRANE PROJECT

Part two by Tony Sprent

Work is progressing with the undercarriage chassis which is nearly complete. The four main I-beams, and the two intermediate beams were fabricated from 1.2mm brass sheet and 0.9mm strips folded to form angle section.

Silver solder was used to fix these rather than rivets which would have been a major job. Given the amount of solder used and the cleaning up required, I was tempted to use a two-part metal epoxy adhesive to fix the angle section. I used some on the main ring gear to fix a mistake I made with the holding down lugs. It seems a good product which I will be using in future.

I’m using ¼” chain for the drive. It scales very well for the project. I’d chosen a ratio of 10 to 17 teeth however it was not possible to fit the chain on the model given the joining of the links and the spacing of the sprockets as it was either too loose or too tight. I have ordered two 12 teeth sprockets to overcome this. 

It is interesting that the original crane has the chain drive to the left-hand rear bogie and to the right-hand front bogie. In fact, they should probably be the same, either to front or back, as it is possible to have a situation where both could slip.  I found this out when I was checking the level of the under-carriage frame.

I am using M3 and M2.5 hexagonal headed nuts and bolts for the construction. I have managed to get a good supply. Julius has specified M2 in other situations as well. However, with my eyesight and large fingers these are too small.

I find it very difficult to position nuts, particularly in confined locations while screwing them on to the bolts. I’ve found the best way is to attach the nut to a thin strip of brass with super glue and hold this while I screw the bolt. The brass strip can be bent to shape to hold the nut in the correct position.

The 6061 aluminium ring gear teeth were waterjet cut as a complete circle by a local workshop here in Hobart which save a large amount of time. It would have been very difficult for me to make with my equipment. 

The bevel bearing surface was machined and the holding down lugs cut out by bandsaw and finished by hand.  The original gear was made in eight sectors which were bolted together.

Once the undercarriage is complete, I will be starting on the upper framework.  Much of this will be fabricated from brass section, either silver soldered or glued and/or screwed together rather than having castings made.

Because of my interest in the crane, the local City Council and Port Authority asked me if I could give talks about the crane at a “Waterfront Weekend”, highlighting the Hobart waterfront. They built a viewing platform alongside the crane at working level so that the public could see the engine, controls and gear system at close range. I also had the model and some of the drawings on view. There was considerable interest in the display.

Photos below are:

Undercarriage frame

Undercarriage

Machining the ring gear.


Part one here

Drawings start here

https://www.sarikhobbies.com/model-engineer-builder/

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