Although not Free you can trial Alibre for free and that will give you an idea of what can be done, If we could post .pdf files here I could post something for you to move around.

**LINK**

I also use Alibre. When I bought my copy I went for the top of the range, as I needed the sheet metal facility, but as Jason says there are cheaper versions available. The software does have some irritating features and limitations, but that is true of all CAD software. I've just finished a project where an outside company designed an injection moulded case using Solidworks. They spent most of the meetings thumping the computer and cursing the software. One big limitation of Alibre is that it is not good at free form surfaces, but that is unlikely to be a problem for steam engines.

Here's an assembly of parts for the motion work on my traction engine. So far it has proved that the paper drawings are a complete fantasy, almost none of the parts fitted together as drawn. And the valve gear appears to be wrong too.

On the assembly I can rotate the crankshaft and see how all the parts move in sympathy. PM me an email address if you want a PDF of the above which you can pan, zoom and rotate.

Dimensions are inherent to the creation of the 3D model. Alibre is also parametric, which means that the dimesions can be equations. I am designing the traction engine in imperial so I can enter 7/32 in the dimension box instead of working out the decimal equivalent. I have had to make changes in the design as some material is only available in metric sizes. So if I need to take 6mm off a dimension I could type, for instance, 7/8-6/25.4 in the dimension box. Finally for a square I could dimension one side with a number and it would be allocated a name, say D1. Then for the second side I enter D1 as the dimension instead of a number. Then, if I change the size of the first side, the second side changes automatically.

Using a 3D CAD system requires a very different mindset to a 2D CAD system. If you can think in 3D and see how parts are built up from simple 3D shapes it helps enormously.

Regards,

Andrew

Andrew, you can also enter that dimension as 7/8" – 6mm and it will come out the same so no need to express the metric as a fraction.

Stuart,

I have used TurboCad, not v15 though, and it is 3D, but you need to be in model space not paper space. As I am not near a PC with it on I can't give precise details on how to switch the view. If they have removed the 3D options I would not be happy.

A quick google shows this which might help.

**LINK**

Baldric

I pride myself on being able to use most software without botheruing with the manual. I have Turbocad 16 deluxe 2D/3D and it scares the **** out of me. I must persevere – doing drawings in Corel 10 is not sustainable…

Neil

Stuart,

Here is a link to the relevent page: **LINK**

Chris C

I've been using Google Sketchup which is a 3D drawing program thats free.

I find it easy to use and has free tutorials, but I've only used it for fairly simple engineering

designs. There's no way to export the design in .dxf format etc though.

Best idea is to try a few of the proper engineering programs and see which one you get

on with the best. Most have free versions with limited functionality to get a feel for them.

It will take a while to get really familiar with a given program and some are more user friendly than

others. MEW has had some suggestions on drawing packages in the past which would be worth digging out.

Cheers.

Sketchup has no true circle or arc capability though.

Martin.