My 7mm dabblings

[adrian]

Thanks for posting this - interesting stuff and I'm following it closely. I have been thinking about a couple of jobs which might be easier with etchings so I'm keen to see how this goes.

 

[Ian G]

With the class 40 bogies are you going to turn them into snow ploughs?

Ian G

 

[BrushType4]

With the class 40 bogies are you going to turn them into snow ploughs?

Ian G

Good idea

 

[mickoo]

With the class 40 bogies are you going to turn them into snow ploughs?

Ian G

Now there's a thought I hadn't even considered that aspect, in which case a single etch bogie etch works very well, anyone got any decent pictures or rough GA drawings?, could add the body as a separate etch, then it might be worth passing on to others at a reasonable cost?

I did suddenly think this morning, actually I had two thoughts, the primary one was 'bloody hell' this is a lot of fun, just like being back in the good old days with aircraft artwork but with choo choos instead, I'll be honest, much as I like aircraft the CAD side was mainly about the money and it was money driven I.E. what was popular and would sell well, which is not always what you like as a modeller

The second thought, and it's blindingly obvious really, was when I moved some paperwork on my desk and uncovered the WIP 1:32 Class 40, with a little effort I can scale up my masters to suit a 1:32 model etch. Going one step further they could be scaled to Gauge 3 and printed out as paper masters for applying to what ever material you need and cutting out.

Talk about an explosion of ideas that keep popping into my bonce....making if very hard to concentrate and do the actual work LOL.

Anyway not sure if these have ever been shown here, some of my previous work in 3D CAD Never finished any of them LOL (determined not to let that bad trait continue into railways!) though the F100 was sold on for completion by a'n'other company and the P-61 given away to a team to finish it as a donation ware product to support the real P-61 restoration fund.










Right back to slots, tabs and intricate plate work around the drag box!

 

[Dikitriki]

The second thought, and it's blindingly obvious really, was when I moved some paperwork on my desk and uncovered the WIP 1:32 Class 40, with a little effort I can scale up my masters to suit a 1:32 model etch.

A decent 1/32 class 40 kit Can I put my name down please I do admire your CAD skills.

Richard

 

[mickoo]

A decent 1/32 class 40 kit Can I put my name down please I do admire your CAD skills.

Richard

Richard,

Thank you, though you did say 'decent' not sure I can reach that mantle LOL, but we'll see how it all pans out

All,

OK back to CAD work and the 08 doors, looking at other peoples artwork and tabs I see they are part of the back scene (black), obviously if you want them half etch you need to add red or not red depending on your approach over the top. However the issue is how are the tabs made, some people quote no overlaying lines so all parts have to be (I believe the saying is) manifold. To produce that means exploding each part and cutting in the tabs which is time consuming as the end result with the fill is the same....and I think it's only the filled images that are used in the end anyway when the file is converted to a photo tool.

Attached below are two images with parts of two doors, on the left is a manifold door where there are no lines on top of another (left door) where as the right door has the tabs as small rectangles placed down but two line overlap the door shape and the moat exterior wall.

The second image shows the filled image, but I've left off a couple of tabs so y'all can see where they are, obviously manifold is slightly easier to fill as the fill just pours into each door and tab, the other way requires three fills, the moat wall, the door and then the tabs.






Regards

 

[JimG]

OK back to CAD work and the 08 doors, looking at other peoples artwork and tabs I see they are part of the back scene (black), obviously if you want them half etch you need to add red or not red depending on your approach over the top. However the issue is how are the tabs made, some people quote no overlaying lines so all parts have to be (I believe the saying is) manifold. To produce that means exploding each part and cutting in the tabs which is time consuming as the end result with the fill is the same....and I think it's only the filled images that are used in the end anyway when the file is converted to a photo tool.

Attached below are two images with parts of two doors, on the left is a manifold door where there are no lines on top of another (left door) where as the right door has the tabs as small rectangles placed down but two line overlap the door shape and the moat exterior wall.

The second image shows the filled image, but I've left off a couple of tabs so y'all can see where they are, obviously manifold is slightly easier to fill as the fill just pours into each door and tab, the other way requires three fills, the moat wall, the door and then the tabs.

Mick,

I see what you mean. It would look as though the right hand side, with the separate tab squares, would do the same job provided they were butted up with absolutely no space between the tabs and the rest of the etch. But I suspect that there may be problems somewhere in the etch tool making since all instructions I have seen state that the tab level, including the tabs, should be one complete part which can be filled in one operation. I suspect that a phone call to PPD will give you the horse's mouth answer. But if your right hand method is OK, then that would make life a lot easier. As you say, exploding complex poly lines to fit in a tab, then joining them up again can be a right PITA.

[Edit]After typing that last bit about PEdit, I went and looked at it in ACADLT and you can edit vertices to avoid exploding polylines.

Jim.

 

[mickoo]

Jim,

Thanks, just about what I expected really, they do say on PPD that it saves a lot of time and cost if you add the tabs yourself, if they are manifold then I can see why. I started with the explode function first but then found that break is much better, it does spit the part into two parts with a small gap where the cursor was when you asked for the break, but if it's a part that has 40 faces it ends up as two parts of 20, rather than 40 individual faces with explode....which require another 39 joins to get back as one. Once split you just then move the vertices to match the tab locations and then join all as one manifold part.

My separate tabs are very accurate as I use the snap function on a grid of 0.05mm, I'm hoping that's accurate enough! It ensures vertices are on with adjoining vertices.

Today's current job has been the drag box and webbing, all interlocking so I'm hoping my tolerances are going to be ok, generally I've added 0.1mm to most faces that abut another, going on the principle that it's easier to file back than to add a solder filler or worse throw away.

I suppose I should just send off the drag box decking and webbing as a trial as that will check all the tolerances and fits.

 

[richard carr]

Mick

I have had PPD do a bit of etching for me and to get the tabs you do need to draw in new poly lines that include the tabs, it is a bit painful but once you get used to it is fairly quick.

One of the things I did a while back was a bogie inner for for JLTRT class 40 so that you could build proper 3 beam compensation into the bogie. It works well for S7 but it won't go round much under an 8ft radius curve. If you have seen the latest heljan prototype you will see that it has a separate pony truck for the front axle, I think that is the solution thats required to get it to go round 6ft radius curves in S7.

Richard

 

[mickoo]

Richard,

Thanks, I was kinda coming round to the fact that I'll have to 'cut in' the tabs, the painfull part is that the 08 doors all need four tabs and some need six. These are half etched to represent the thinner stamping at the handles and hinges. With hindsight it may be better to have the doors and half etch 'fingers' completely separate from the carrier etch and just two or three bespoke tabs that are not retained as I currently have, will look at how hard that is to achieve, might actaully be easier to rework that way than to cut in all the current tabs.

Class 40, yes I do hope to make an inner chassis as well for CSB suspension. The front wheel on the class 40 is actually a pony truck in 1:1, it is controlled by swing links which to get the require length and thus radius are extended in front of the buffer beam to a pivot outside of the loco, these pivots are covered by those two domes at the bottom of the buffer beam, I'll dig some photos out tonight when I get home if your interested.

JLTRT use a radial sliding block, much like a Cartazzi truck, most other kits use a pony truck as you noted on the Heljan, 4 and 7mm, neither are true to the real deal. I'm not sure of the 'psuedo' radius that the real swing links give but at a guess I'd put the pivot theoretical pivot point back behind the first driver and maybe even close to the middle of the bogie.

Mine wont be prototypical either as I'm going to try some sort of bodge that uses CSB not only to contol vertical springing but also to provide lateral force as well, a sort fo free floating axle held in place simply by the two CSB wires. I found on the 08 that the thinner etch used by MMP allowed the Slaters brass axle boxes to float laterally, the application of the CSB then dampened that float and provides a nice (all be it small - 0.2/3mm) cushion.

I only have about 2mm clearance on my bogie and can now see why EE made the bogie frames kick wider around the front pony LOL, I've only got just over 1mm on the drivers between S7 and side frames which are scale width, it's amazing how tight these gaps are on the real deal!. That gap is made smaller by the side sheets of the mud guards if they are placed true to prototype, so I may need a little modellers license here to give more leeway between wheel rims and mud guards.

Hopefully another update tonight both for the 08 and 40 etches, PPD had some insight into laying out the etch to save money, long thin ones are cheaper than square ones, the longest side being 285mm or the long side of an A4 sheet, so it's best to lay your A5 sheets side by side letter box style rather than on top of each other packing box style, a picture would explain so much better LOL but lack of such basic tools here precludes that!

Kindest

 

[BrushType4]

Mick,

I came across this interesting picture and I thought you'd like it.

 

[richard carr]

Mick

What make of wheels are using for your 40 ? Slates wheels are too thick and although you can thin them a bit when reprofiling for S7 you can't really thin them enough. I turned my own from some cast iron bar, cheap, time consuming, but the right thickness, even then though there is very little space for side play and they rub on the bogie side frames.

When I build another 40 (they are my favourite diesels) I will re draw the bogie inner with a pony truck.

Richard

 

[mickoo]

Richard,

I'm using slaters and I only need take 0.25mm of the rim to meet S7 standards which looks easy enough and I've heard others do it, your problem may actually be the boss, these need quite a bit more taken off, about 0.75mm, that can be done too but I'm going to make a hole in the side of the frames where they are, theres already a draft hole there at the moment, just need to calculate final Dia. MY axle boxes will be resin of 3D printed so no shorts there and side play is limited to 1mm max, I found on the 08 that just 0.5mm is ample, though it's a shorter wheel base it still passes through trackwork with out shorts fine...even before the wheels were thinned to S7.

It may be that your frames are too close together, should be 41mm between frames in 7mm, I'll get the exact measurment from the drawings later but think it was 5'.10" and some fraction, anyway, as close as damnit to 41mm.

I'm hoping to get these etches done in the next few days and sent off, want them before I go on holiday on the 22nd so I can peruse and work out if the master tool needs editing, they are not far off completion TBH, just a few more brackets and such like and then shuffling on the sheet to get thebest layout and then adding all the tabs and such.

Have to agree the Class 40 anorak has mugged me good and proper ATM, dodgy hand injury precludes any decent model making.....cant even cut my own food properly!....so this CAD work and Class 40 research is the next best thing and advances that project on leaps and bounds. Still need a couple of rarer books but think I have most by now LOL.

Will your next build be scratch or a kit or RTR rework?

Kindest

 

[mickoo]

Mick,

I came across this interesting picture and I thought you'd like it.

View attachment 19500

Kewl!! shows some nice details of body work construction, much appreciated

 

[mickoo]

Getting there, needs some tidying up and some tabs adding as well as a few brackets and stuff. Then it's a case of generating the red and blue layers, the black one I've been doing as I go along.

Try as I might to shuffle things around, it's not going to end up in a nice neat even layout, I'd hate to waste the spare space so need to think of other bogie stuff that can be added and fitted in.

That tail beam is just so large sat out there all on its own some, it does need rotating 90° but the overall length is all but filled to meet PPD recommended 285mm for cost effective artwork. It could go up the far right if I take the drag box parts out but then they'd be strung out in a low long line across the bottom, not very efficient at all.



The idea of the drag box art work being separate (will be joined with half etch tags) is so that PPD can fold that bit over and reduce the overall length for shipping, this package will be prime suspect No.1 for Mr Pat and his cat to bend!

 

[AndyB]

this package will be prime suspect No.1 for Mr Pat and his cat to bend!

No worries about that with PPD in my experience - they always pack etches in hardboard and ply - whether it's a small single etch on 0.006" or a bulk delivery of 40 A3 sized etches in 0.018".
With the latter, there was more chance of Pat hurting his foot by dropping the package on it than bending the etches!

Regarding tabs - there is no need to split your outlines. Just make the tab a closed shape using object snap and ortho to keep it square and butting up to your outlines. Fill the tab red, then just copy it to all the locations where it is needed.
I aim to keep a common 'moat' size on all my parts in a sheet (generally 1mm for 0.018" stock), so very few 'special' tabs are needed.

Andy

 

[Osgood]

Basic question - how do you decide whether to part etch the rivets to facilitate the use of a rivet press tool, or to part etch the whole area except rivets thereby leaving rivet heads proud?

I've just collected some really Cowans Sheldon crane etchings from Dan Pinnock, and the later method produces a very neat, clean result.

I can understand that forming each rivet head may produce a better 'domed' shape but I have to say the crane etch rivets look pretty good.

I can also appreciate that you need to start with a thicker material which for large slabs like these bogie side plates (that was real steam era engineering that!) could impact on the cost considerably. Any other reasons?

 

[mickoo]

No worries about that with PPD in my experience - they always pack etches in hardboard and ply - whether it's a small single etch on 0.006" or a bulk delivery of 40 A3 sized etches in 0.018".
With the latter, there was more chance of Pat hurting his foot by dropping the package on it than bending the etches!

Regarding tabs - there is no need to split your outlines. Just make the tab a closed shape using object snap and ortho to keep it square and butting up to your outlines. Fill the tab red, then just copy it to all the locations where it is needed.
I aim to keep a common 'moat' size on all my parts in a sheet (generally 1mm for 0.018" stock), so very few 'special' tabs are needed.

Andy

Tabs....B###&*(ks....LOL having spent hours making them all manifold I wish you'd posted that a bit earlier I'd prefer them to be as you describe, much easier to work with and yes I am using snap (0.025mm) and ortho already so that's one issue avoided . Re-moat size, I've basically gone for 0.5mm as a minimum but in some cases to keep the moat as simple as possible....rather than follow the shape of the part....some tabs are a little wider. I'm not sure about the thickness of the moat around larger parts so have tended to perhaps go overkill with 2-3mm.

If you have a red half etch tab do you still need to add it in black underneath? The logic would seem yes, but practice? I have found that making the black part all manifold makes it very easy to flood fill, though you can select all and flood fill that way I suppose, I suppose it comes down to the fact that I still don't know WTF I'm doing LOL.

I'm going to ring PPD today and find out about this red layer, whether they will accept just red tabs as half etchs as shown above or require the red layer to be like the black but only show the red bits required, as shown earlier by Tony.

Thanks to all for the input, greatly appreciated.

 

[mickoo]

Basic question - how do you decide whether to part etch the rivets to facilitate the use of a rivet press tool, or to part etch the whole area except rivets thereby leaving rivet heads proud?

I've just collected some really Cowans Sheldon crane etchings from Dan Pinnock, and the later method produces a very neat, clean result.

I can understand that forming each rivet head may produce a better 'domed' shape but I have to say the crane etch rivets look pretty good.

I can also appreciate that you need to start with a thicker material which for large slabs like these bogie side plates (that was real steam era engineering that!) could impact on the cost considerably. Any other reasons?

I can see where your coming from but it depends if you have half etches on the back. To get etched rivets you basically half etch the whole front face off and on the Class 40 that'd be great as there are some rivets that are differing sizes and punching them different can be a pain. However to aid construction I also have half etches on the rear, folds and guides, these if using etched rivets will then become holes as you've effectively half etched through front and back, make sense?

Theres also a strength issue, the bogie sides are quite long and I'm aiming for 0.375 NS as the overall material, thick enough for support on large pieces and thin enough to work and bend for small fiddly brackets....I hope! If I half etch the whole bogie side then it only becomes half as thick and this quite thin for a major large part I feel. I could follow some kit manufacturers and have two parts to each side, the thick supportive layer and a thin half etch overlay.

The preference would be etched rivets on the bogie sides, but opposing half etches preclude this in this instance, but it is food for though and I'll mull it over and see if I can work something out that doesn't require punching 200 odd rivets out LOL, not that I find that an issue but no need to make work where none exists is there

 

[Osgood]

Yes , I can see it is not an easy choice - more to it than meets the eye!