My 7mm dabblings

Discussion in 'Area 51' started by mickoo, 2 December 2012.

  1. Mudhen

    Mudhen Western Thunderer

    Richard/Mick
    On my JLTRT class 40 I used Slaters wheels which I turned to pretty well near scale thickness and then found, as you mention, that the bosses need a lot removing from them; I took-off about 0.5mm. The big difficulty then was the thickness of the sideframes, this took a lot of work with a coarse file to provide clearance and caused concern about damaging the sideframes in the process. It was eventually successful and now I'm trying to ensure the pony truck works consistently, I've used wire springs attached to the outside of the frames resting on top of the pony truck bearings; getting the correct amount of downward pressure is the big issue.
    Richard, after working on the Slaters wheels I had exactly the same idea as you; why not turn them from mild steel bar. I've produced LNER tender wheels this way and can't imagine why I didn't think to do the same for the 40.

    Here a couple of poor pictures of the spring arrangement

    New_1_DSCF0561.JPG

    New_1_DSCF0565.JPG

    Tim
     
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  2. AndyB

    AndyB Western Thunderer

    Sorry - don't get a lot of time to actually type anything with a 4-month old that needs looking after.....

    That is grid snap. Use object snap (there is a setting for how close you need to be to select an object, but that doesn't affect the actual snap point)

    No - PPD will create that for you. What they do is to copy & mirror your black area, then mirror the blue layers and the tabs, then turn the blue layers white and the tabs black . This, when printed gives the back mask.
    For the front, they turn the other red layers (front half-etch and text) white, then print this with the black (non-mirrored), giving the front mask.
    Try it yourself on a small test design - then it makes sense (hopefully!!).

    For people who have only ever done the whole thing on 2 layers (especially on simple designs), I can see why they don't 'get' this way of working. But I found it really useful on my G3 kit, which was a very full A3-sized etch. That was my first ever etch design.
    Andy
     
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  3. mickoo

    mickoo Western Thunderer

    Andy, LOL, know how your feeling with little mouths etc, they sure make a lot of noise for something so small, actually it doesn't get any better the older they get, two teenagers and a six year old, if it's not one, it'll sure as eggs be another!

    I kinda follow whats supposed to happen LOL, so to summise:

    Black layer is the main part with an unbroken moat all the way around it and white etched all the way through.

    Red layer is only the parts you want half etched on the front (half tabs etc).

    Blue layer is just the parts you want half etched on the rear.

    That's basically what PPD show on their site, what's thrown me is that some people are making what looks like the combined layers you describe before it gets to PPD I.E. with a whole lot more red on it than mine, in which case does it alter the tool pricing significantly?

    Nice.....but big etch LOL, if your the same Andy, I'm still waiting patiently for your Britannia etch to re-appear:thumbs:
     
  4. mickoo

    mickoo Western Thunderer

    Tim,

    The problem with the JLTRT bogie is that it's inside face is much much too narrow, the tail beam measures only 39.8mm and that sits in a recess in the side frame so at a guess you're looking at a gap between frames of around 39.5mm. The real deal is 5', 10¼" between side frame faces which is 41mm so you're already on a loser in S7 with the JLTRT bogies out of the box.

    Thinned Slaters wheels should give you 37.62mm over tyre and 38.6mm over boss, clearly the boss is the offending area, standard width Slaters profiled to S7 would be 38.9mm and 41.2mm

    I've allowed mine to be 41mm between faces so should comfortably accommodate thinned Slaters, but as mentioned before, just in case, I'm also going to open out holes where the bosses are and make recesses in the back of the resin axle boxes.

    The front pony is going to be a bit of a head scratcher LOL but your solution looks interesting.
     
  5. Mudhen

    Mudhen Western Thunderer

    Mick
    I see what you're saying but by pushing the sideframes out to an inside spacing of 41mm they will be much too wide over their outer extremities. The JLTR sideframes have been made far to thick, isn't the frame thickness on the real thing something like 30mm; thats why I spent time trying to thin the supplied frames to give wheel clearance. I guess the best solution would be to make new sideframes out of brass or nickel and try to reuse the components salvaged from the resin sides.
    Tim
     
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  6. mickoo

    mickoo Western Thunderer

    Now the pennies dropping :thumbs: and you can see why I'm going down the etching route myself not just to refit my JLTRT but for more scratch built ones to follow. To reuse the JLTRT axle boxes might be a bit of a faff, probably easier to whizz some up in 3D CAD and print them off, or pick the best from a run of say 4 and then cast yourself in resin, I also don't want cast coil springs, but other than that and a few other construction get rounds, the JLTRT axle boxes are quite well represented. I've also got to work out how to make a net of those coil spring upper cups so that they can be folded up from etch for the coil spring to fit inside.

    Your right, moving the JLTRT side frames to have the correct inside face dimension will make them waaay too wide so your trick of beating them with the big file is about the only practical solution. Yours works (I've seen it) mine is just a bunch of scribbles on a screen ATM LOL.

    My drawing doesn't quite show the frame thickness but looks like 1½" so yes in the region of 30mm, of which 0.375mm NS is too thin, but thicker will make the rest of the etch wrong and I really don't want to go with two sheets of differing thickness.
     
  7. Mudhen

    Mudhen Western Thunderer

    All good fun Mick, keeps us all of the streets.
    Tim
     
  8. richard carr

    richard carr Western Thunderer

    Mick

    My next one built 40 will almost certainly be another JLTRT one, I think the kit is excellent the nose ends really do capture the look. I can live with the fact that the inside distance between the frames is too small, that is just because you can't make them the bogie frames that thin from resin.

    Do you know how thick a class 40 wheel is ?

    Richard
     
  9. richard carr

    richard carr Western Thunderer


    Andy

    I'm confused, I don't understand what you are saying at all, I would like to as it sounds like a much easier way to do tabs.

    Does this effect the price that PPD charge, I ask as normally I haven't done any hatching on the drawings I send them, which they never queried but on the last one they said it would cost me £20 for them to do the hatching .

    So what eactly do you send them, can you show us any screen shots ?

    Richard
     
  10. richard carr

    richard carr Western Thunderer


    Tim

    Do not use mild steel bar, it rusts very easily, cast iron resists rust much better, is generally a bit softer (although you can get the odd hard spot) and so easier to to work, it can be a bit messy to some people I much prefer it.
    I don't think its any more expensive but its a while since I bought any.


    Richard
     
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  11. mickoo

    mickoo Western Thunderer

    Richard,

    I spoke on the Phone yesterday about what is required and they take anything and convert it as part of their process.

    For simplicity they advise you follow the instructions on their site and they do the rest so to summarise.

    Black layer: Boundary and object in black with an unbroken moat all around it (unless you want full thickness tabs).

    Red layer: Only the parts you want half etched from the front.

    Blue layer: Only the parts you want half etched from the rear.

    They will then combine the layers or combination of layers, invert, mirror and whatever to get the photo tool. They prefer this method as a: it fits their work flow, it's what they are used too....and they're good at it, b: there's less chance of the author I.E. us oiks, mucking things up by trying to be cute and be clever and produce front and rear tools and getting it wrong. That's not to say you can't do that if you're comfortable doing it but for us dabblers on the fringe stick to the simple rules above, whether that's more expensive or not they didn't say, nor did I get time to ask.

    Hatching is only flood filling so I'd be surprised if they were asking £20 for a 20 second operation, unless your outlines were not completely closed and the fill was leaking out, then they would have to go through the whole drawing and find the holes, that's why I work to snap and then join all the single faces in a shape into one piece which becomes one continuous line around it when selected.

    Image2.jpg

    The bogie side frame outline is one piece, when you hover the cursor over it the whole shape goes dotted, the dummy box above is not continuous but made up of four edges, when you select it on the face you selected changes. Making your parts continuous allows much easier flood filling (hatching) and shows holes up (leakage) much easier. Note in the above, not all of the half etches have been flood filled yet.
     
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  12. mickoo

    mickoo Western Thunderer

    Yes the JLTRT nose is as good as close to perfect I think, thats why I bought one :thumbs: , to measure the radius of corners and bonnet tops, roofs etc LOL, it's pretty close to the one I measured at NRM, those areas that I could measure from ground level!
     
  13. djparkins

    djparkins Western Thunderer

    Mick,

    I agree - you have their guidance and if its a hobby/part time business you probably don't mind that they 'own' & keep the photo-tool. This is standard practise.

    For us it is very important that we own our photo-tools outright [with around 700 in production] and can move them from etcher to etcher if required, so I do all the separation/reversal/step & repeat here and then get them plotted straight to film - all in positive [none of this parts being black stuff] - by an outside provder. They then come back to us ready to go the the etcher. But obviously if there is an error it is down to us - as is the cost of a re-plot! We do the same with casting moulds - we pay for and insist on outright ownership of them. It can be very important not to be locked into just one supplier when it is your livelihood, especially these days!

    I have to say I recognise very few of the stages you and others describe in the prep. of the artwork - it is totally different to the way I work. Everything ends up black on a clear film in the end anyway - just a question of what is on the back & what is on the front!

    Regards,

    DJP/MMP
     
  14. mickoo

    mickoo Western Thunderer

    David, fully agree, business is business, hobby is a different thing altogether and if in business I'd go the same way as yourselves and other business and make sure you have ownership of as many stages as you can, if not all.

    You're right they do all end up as black and white and to be fair, PPD would accept that format too truth be told and that's the format they use to send to their tool editors. But I think they prefer red and blue layers for hobbyists who may struggle with two layers of black and white and then they sort it for you....for a small fee...which is understandable and agreeable (personally).

    Jims samples earlier with the large fills of red and blue are but one step away from conversion to black and white and would be the easiest files for PPD to work from and I may end up doing it that way once I get more familiar with the whole process.
     
  15. mickoo

    mickoo Western Thunderer

    All done and off to PPD for the first test etches, will have to see what they look like when they come back :thumbs: Doubt I'll get much time to look at them as they will probably arrive just as I'm going out the bloody door for three weeks LOL. It'll be interesting to see if the current format they suggested elicits a large preparation fee, if so then I'll take them back and make a front and back black and white etch to reduce that fee.

    Image4.jpg

    Image2.jpg

    What's next? not sure, time for some R&R and in true WT scattergun blast away at something at opposite poles to my current work bench (BR), this little foray into Autocad and etching has certainly opened a few doors for projects I was stalled on, namely GP15, MP15AC, GP38 and a fast snoot SD40-2, hell might even go mad with a SD70M or Centennial, but I think the fast 40 or GP15 will win....or will it....blast, so hard picking a new project to begin with LOL. Whatever it is will almost certainly arrive in Armour Yellow and Harbormist Grey, maybe pumpkin green and orange or Warbonnet blue and yellow.

    One of the beauties of the EMD range is the common part philosophy most cabs are very similar so once on etch is made up it can be used across several models....I hope, bonnet doors are another example of common user parts.

    Ironically I spotted some cast Blombergs on the GoG bring and buy at Kettering...and stupidly put them back, thinking the EMD anorak was well secured, how wrong was I and have nominated myself gold medal in the self arse kicking race! Hopefully I can pick up some side frames from one of the US suppliers like Atlas etc?

    I might be gone awhile :thumbs:
     
  16. ZiderHead

    ZiderHead Western Thunderer

    fascinating thread, especially the development of the Class 40 bogie etches :thumbs:

    what springing/compensation method will you be using on these?

    Jon
     
  17. mickoo

    mickoo Western Thunderer

    Thank you,

    I'll be using CSB with Slaters axle boxes but not the guides, the slots in the inner chassis provide fore and aft tolerances and the CBS tube with the wire in provides anti rotational forces, quite a loose arrangement and very un-S7 LOL but for diesels it's passable but for wheels with connecting rods not so advisable. I'm going to use the tube and spring wire already bought for the 08 and weight accordingly to give the required deflection.

    The inner chassis will form another etch which I'll cover later once I get Stephs intermediate gearboxes so I can fiddle and come up with a workable arrangement. I may go with a body mounted motor and cardan shaft down to the intermediate driven axle and then another shaft to the leading driven axle, or fixed motor within the inner bogie and cardan shafts to intermediate gearboxes.
     
  18. mickoo

    mickoo Western Thunderer

    Steph, Pugsley, much obliged, will look them out and see what gives :thumbs:
     
  19. mickoo

    mickoo Western Thunderer

    In further news on the S7 front, PPD accepted the etches with minimal alterations, the only thing I have to do is add a few extra layers with the outlines on, for example, the red half etch I had made with outlines on and then flood filled, that needs to be two layers, one with the outlines and one with the fills, not quite sure how that is achieved, I.E. how do you fill/hatch an area on a layer below the one you are working on?, but then I have noticed Autocad do some odd things when working with layers, they seem almost transparent and pick up qualities and boundaries from layers above and below.

    So 90% pass on the first run, quite happy about that TBH, ohh and the cost? No brainer cheap, just silly cheap, they advised I fill up the remaining sheet with further copies of each artwork sent....at no extra cost....but all useless if the first run if out somewhere. That will be the acid test and I fully expect to have to adjust something somewhere and resend new artwork to be tooled up. Both bogies and doors topped out at £29 each sheet + VAT + P&P which of course opens out possibilities for my other thread.
     
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  20. S-Club-7

    S-Club-7 Western Thunderer

    Easy. Anything drawn in AutoCad is created on the current layer. So draw the outlines first, then change the current layer before creating your flood fill. The "Layer Properties Manager" dialog and the LAYER command are your friends here.

    If you're at the S7 meet at Brightwell-cum-Sotwell tomorrow then I'll be happy to give you a quick demo/tutorial. And if I can't help then I'm sure Len Newman of Exactoscale C&L will be able to as he worked for Autodesk for a number of years.

    Or Sudbury at the end of the month?