Monday, 15 February 2016

Boxpoking about

Hello.

So what have I been upto since my last post I hear you all ask. Well, I have been mostly CNCing stuff.

I have a Dapol Q1 which has been treated to a conversion a while ago. For those of you who remember it I ended up writing an article for the Model Railway Journal which ended up in issue 211. The problem was that I was never happy with the results. While the engine did run it wasn't upto my standards as the wheels were a kind of hybrid of dapol and 2mmSA.


As with many things in life, the older you get, the more knowledgeable you get and this is a classic case. Since my last attempt at conversion I have rethought an approach to producing the wheels for another attempt at getting something I am happy with. This time armed with a CNC mill I made a start...





This is how the wheel started off. A 3D model of a scale wheel with a 2mmSA rim attached, from this I can generate a CNC programme. In my previous post I showed how I turned up the blanks from Paxolin and added the association rims.

The wheel blanks were clamped in a rotary table and clocked with a dial test indicator to ensure they were centred correctly. I had a frustrating time getting the DTI to fit the milling machine because of the depth on the Z axis wasn't enough. This meant I had to make a little bracket (seen clamped to the mill chuck) which was a pain.
Once the wheel was centred the programme was then run. The milling cutter is a 0.5mm slot drill which conveniently was suitable for all the milling and drilling operations. The programme took about an hour per wheel. It seemed to take forever to do all 7 (6+1 spare) spread over a number of evenings.
And these are the result to date. The backs need tidying up a bit on the lathe but other than that the next step is cutting some axles and fitting them to the chassis.

Am I happy with them? Definitely, they look like Boxpok wheels and fingers crossed they are an improvement on the previous attempt.

Julia.



5 comments:

  1. Seriously clever stuff.....

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  2. Very nice Julia. Let's hope that they run as good as they look :-)

    Ian

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  3. Hello Julia, they look great. Looking forward to seeing the reborn Q1.

    Alex.

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  4. With pedant-mode 'on', I should point out that these are not Boxpok wheels but Bulleid Firth Brown (BFB) wheels. The American Boxbok wheel was made of sections fitted together, whereas Bulleid's design was a single casting. See https://en.wikipedia.org/wiki/Bulleid_Firth_Brown for more info.

    Whatever the name, that's a wonderful bit of small-scale milling that you've done :)

    Mike

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