Ive managed to get my hands on some copies of some Swindon drawings that have been digitalised and want to get some frames cut from some 1mm or preferably 18 swg sheet steel, my questions are;
Do they have to be physically drawn again using some form of software thats out there or can they be scanned like a photocopy and just edit out the bits you dont want to the size needed?
Can you recommend anyone out there that does this sort of thing on a regular basis and knows exactly what there doing to achieve the desired results. Accuracy is what im looking for rather that a sort of representation.
please forgive my ignorance on the subject , we are all learning , me included!
Rich
Normally the laser cutter will require a digitised drawing in the form of a .DXF or .DWG file (produced by a CAD system) - however some will do the CAD for you from your 'paper' drawings - although this will usually be at extra cost.
Model Engineers Laser (MEL) has a good reputation within ME circles and is under new management since Malcolm retired. I've used their laser cut parts and they were excellent. Other G3 Members have also had loco frames water-jet cut by SCISS. Mike W should also be able to recommend someone from his experience in this area.
Regards,
IanT
Rich,
Today there are many companies that offer laser and water jet cutting services, and as Ian says, some of them will do CAD as well (their web sites should tell you if they do), but they will charge commercial rates for the work. They are not model engineers and will not be familiar with historical railway drawings. If you are working with a GA drawing, disentangling the frame (or any other component) from everything else on the drawing is a significant task and prone to error if you are not familiar with the subject. If you decide to go this way, I suggest you do that bit yourself and produce a dimensioned sketch of each component for the CAD person to work from.
MEL is different in that it is run by a model engineer and isn't really a commercial organisation. He is worth contacting for a discussion, particularly of whether to work from the original drawing or from your sketches.
Another point that may or may not concern you. Unless your prototype comes from the early days of steam, the frame thickness is likely to be about 1¼in, a dimension that was fairly standard for much of the steam era. That scales out as 1.4mm which is a bit larger than 1mm or 18gauge (had to look that one up!). I make my frames from 1.5mm sheet, which is the nearest size readily available.
Nick
I echo Ian and Nick. The actual cutting is the easy part, but the design needs a lot of work. You mention accuracy Richard, but I suspect you will not be assembling your model frames with correct to scale crossmembers and fastenings. You will also be needing out of scale movement in the axleboxes. I personally find that laser cut crossmembers located by slot and tab make a strong unit but consider things like where the fixings for the body will be and what can be seen. I know some people prefer turned bar for spacers. What does the real engine use?
Firstly, when it come to thickness, consider how you will fix the parts together. As Nick says, many engines used 1 1/4in steel but in the era I model they were mainly 7/8in, so 20g (0.9mm) is fine for small engines. If you go to 18g it adds a lot to the strength but if you will be soldering them together that also needs a lot more heat.
Secondly, decide how far apart your frames will be. There are many factors to consider but they will probably not end up scale distance apart.
Thirdly, is the model to be electric or steam?
Also, Nick mentions waterjet cutting which gives a superbly smooth edge and doesn't harden the metal, but it has more draw, meaning the edge isn't square with the surface (laser cutting isn't either, but its better), is less common and more expensive. In my opinion laser cutting is perfect.
Sorry to say this but you have a lot of work yet designing the frames you want before you consider where to have them cut. I have no experience of MEL but I'd say speak with them and if you need more help send me a copy of the drawing and I'll give my views - NOT that I am an expert in loco design, but I'm very happy to look and see.
Mike
Richard - one further point. Ian.T will know the technical terms for this but a scanned drawing will be made of micro dots which build up an image. A laser needs point to point locations. Therefore you have to re-draw into CAD anyway.
I assume being Swindon its a "Pipe and Rod" drawing you have? Crewe called it a "General Arrangement".
Mike
Thanks people for the feedback and the words of wisdom in regards to how best to go about Laser Cutting or Water Cutting items.
The Frames are 1" thick along with the Buffer Beams for a 57xx GWR Pannier, so as i said earlier the closest im going to get is probably 18SWG if i can find it.
As you rightly say Mike , im not going to be able to replicate the width twix the frames , that is dictated by wheel btb and the need for a bit of lateral slop thrown in for good measure.
I usually use a big slab of glass to build most kits off for a true flat surface. Frame spacers will be 3/16 thick flat brass machined to the Buffer Beam depth behind the Beams and mid frame spacers probably the same thickness as the frames.
Why dont i just make up a kit from GRS i hear you ask , well all ive read about their kits is how awful they are and they dont even have any degree of quality let alone being a scale item. This will be a bigger version of an Aster Pannier , Live Steam and Spirit fired and built to scale!
The drawing is a Frame Plate Drawing and Buffer Beams along with a few other brackets as well so a sort of General Arrangement .
If i Knew how to post it here i would!
Mike's comment about frame widths surprised me - in a good way. By coincidence Christopher Valkoinen's wonderful book "Railways. A History in Drawings" recently arrived (birthdays still have their uses) so I was able to check a wide selection of drawings from multiple companies and eras and, yes, the range of frame widths is wider than I thought. I guess my remark was clouded by the more limited selection of locos I have built. Live and learn.
Mike is also correct about the drawing format. A scan is a "bitmap" or "raster" format of millions of tiny dots, whereas laser cutting (and other computer-controlled machining) requires a vector format. Fusion 360, which I use, has a neat feature that allows the user to trace a bitmap picture and produce the vector equivalent, and other CAD software probably has similar features. I've used that for my own modelling. But it is still a labour-intensive process.
My process is to trace the frame shape as described. Decide whether any modifications to the basic shape are necessary, such as increased clearances on bogie wheels to allow them to move on curves. The prototype frame will have a lot of holes for bolts and rivets where other parts are attached. Decide which of those need to go on the model, and make the hole size as necessary for the rivet, bolt, or tapped thread I intend to use. Add any additional holes (hopefully in concealled locations) for frame spacers if you are not replicating the prototype features. Consider whether dismantling of the frames will be necessary, or whether they can be fixed in place forever. Only then will I have a frame that is ready for manufacture.
Nick
Richard
I have PM you re frames
Mike