6" Burrell Gold Medal Tractor

CAD

I have been intimately involved with CAD for a long time and seen the tremendous benefit it has brought to industry and want to harness its power to my model engineering activities. It has become my practice not to make anything in my workshop without first producing a CAD model on my computer. Rather than cost me time I believe it has saved time by enabling me to, understand the design, correct any errors present in published designs and produce workshop drawings that suit my way of working.

Full CAD is much more than 2 D design on steroids. The aim is to fully describe the product to the computer to enable the computer to do much of the work with the minimum effort on my part. For example if two parts fit together I define only one and tell the computer to make the other fit.

How far this can be taken depends on the power of the CAD program available. With most advanced programs it would be possible to test the strength of the design for example stress analysis of the boiler or even run the engine on simulated steam. My use is more modest for example "does it fit". A unique application to Model Engineering is that when a part has been incorrectly machined the design can be interorgated to see if the mistake can be accommodated and if so what compensating changes are necessary.

Cost is a major stumbling block for the model engineer wanting to use full 3D CAD. Systems such as ProEnginner, CATIA & Solidworks are unaffordable to the Model Engineer. In round figures industry pays about £10,000 per "Seat" for a modern CAD system which is small change compared to the potential savings. Another feature of the market is that substantial yearly maintenance (10%-20% of initial cost) is payable.. Some vendors have educational versions of their programs but I, as a model engineer, do not qualify for them.

With such a price barrier illegal cracked downloads of the high end CAD programs may be available. I have always been reluctant to follow this path and now with so much E-crime I wonder what nasty programs are download alongside the application.

Alibre
I downloaded the trial version of Alibre a couple of years ago and did not get on with it. This would have been it had I not had a conversation with Mike from Station Road Steam. He told me that he was using Alibre to design a new loco currently in preparation and he was finding that Alibre was comparable to the high end CAD programs but at an affordable price. With this fresh stimulus I again downloaded the trial version of Alibre and persevered until I had mastered its idiosynchrosies. Over a period of days I did most of the available tutorials. This was recommended me by Mike and I now endorse his recommendation. This was a very intense period since after 30 days Ailbre would downgrade from Professional to the much more basic Express version. While I describe Alibre as affordable at around £1K Alibre would be a significant investment for me and I needed to be sure.

It is now several months since I acquired Alibre and I have become proficient in its use. I have found that it offers many of the facilities of the high end CAD programs but has one serious problem:- Alibre is not very reliable. It is at its most frustrating when it crashes particularly when I have not saved for some time. More frequently some aspect stops working correctly and Alibre has to be restarted to resume normal operation. Version 12 is due out shortly and I hope effort has been employed to improve stability rather then add endless bell and whistles.

CAD and GMT
I shall be developing a full CAD model for the GMT. This is an on going activity and my initial efforts have been directed towards the parts I intend to make first, namely the wheels. Here I should mention my involvement with Edward. Currently (May 09) Little Samson Models do not have a complete set of drawings to the 6" GMT. Through Edward I have obtained copies of many of the works drawings and provisional copies of the Little Samson Drawings and have been busy producing Alibre CAD drawings. Todate I have drawn the front end of the GMT and passed the back to Edward and a contribution towards the official drawing set. I have also made a start on the Boiler, Hornplates and back wheels.

As an example of the sort of detail drawings that can be produced here is an example of a detailed drawing produced using Alibre. Wheel drawing pdf

It addition to conventional drawings such as the GA shown above Alibre enables me to publish 3D models of the GMT. The screen shot belows links to a standard PDP file containing the 3D model. Once the PDF has been opened in the reader click on the picture and a tool bar that enables the model to be turned appears. If that is too complicated just try dragging the picture with your mouse - it will turn! It is well worthwhile exploring the many option available from the toolbar. You can even see inside the engine.

Be patient the linked 3D PDP is 6Mb

While I have not yet decided on my policy for distribution my 3D models and drawings derived from them I wish to make it clear that I have no intention of making a freely available complete downloadable drawing set for the GMT.

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