7mm US model dabblings

[Big Train James]

The orange beacons should be strobes. Rotating beacons are soooo 80's. Modern units equipped and intended for remote control operation are required to have the pair of orange strobes. I don't know if it is a rule that they go on the cab, but that's where I always see them. This includes road units with the spartan or safety cabs. It's also why there are so many antennae present on the roof. There will be additional equipment located in the cab for the R/C electronics as well.

I'm liking the look of the new roof. I presumed you were going to remove the old one entirely. Do you still plan to put a ceiling on the inside?

On some units, the cab vent is located on the roof instead of the cab face. However, the pictures I saw with this detail were of SP units with the high number boards. The vent may have been on the roof strictly out of necessity.

You're going from back to front. I'm the other way around.

 

[Big Train James]

I must add, I'm impressed. I don't know how you managed to file the existing roof down with any degree of uniformity.

 

[mickoo]

I must add, I'm impressed. I don't know how you managed to file the existing roof down with any degree of uniformity.

With a very BIG file, patience and much swearing

Your right, the SP number boards take up the space where the cab vent would normall go so it'd have to be moved elsewhere.

Strobes they are then

 

[Big Train James]

You may wish to take a look at the website for the Appalachian & Ohio, which is a quite well done O scale layout not far from Denver. It's currently taking shape in its second incarnation, as the website details. At any rate, there is a forum, and a somewhat common topic is comprehensive lighting for locomotives, including beacons. Bob Sobol is a member of the crew, and clearly a very handy fellow. In one of his posts, he breaks down the fabrication of new beacons for his locomotives, including base, LED, and lens. He also has some information on his Smugmug photo hosting site, a link to which can be found under the Links tab at the top of the page.

I have found all kinds of useful ideas on both sites, and will surely be trying some of the lighting ideas on my builds. As an aside, Bob has also done the radiator modifications that we both are planning on, albeit for earlier sw type switchers. He even has a couple of photos with nice closeups of the front grill work.

Have a look around, I hope you find it interesting and useful.
Jim

 

[Steph Dale]

Bingo - Thanks Jim, I'd lost the link that you just posted. Wonderful, inspiring stuff...
Steph

 

[mickoo]

Small update, the paper air filter housing.

Make one brass box.


Cut two slots (badly) and trim plastic engine cover casing underneath.


The casing sides are not parallel, they bulge out at the top shoulder

Add brass cover, check drilled holes for lifting eyes line up, they do


Sit back and ponder next stage, which is to add the three covers on top and fill in the badly cut slots. Ironically the wobbly slots do grip the brass very well and I could probably get away with out any adhesive to hold it in place. I also need to open out and thin the exhaust stack walls, they look more like 18th century clay chimney pots than thin walled steel tube

 

[Big Train James]

Looking good.

If you have a chance, could you outline how you fabricated that brass box. Everything appears just so. Nice tight corners and crisp edges. I'd like to be able to do that as well. It's one of the reasons why I like styrene sheet as much as I do. I'm more comfortable working with it given the tools and techniques I have in hand.

I will most likely be modifying my stacks as well. Why leave any stone unturned? I will most like run the back of a narrow blade, or more likely a round pointed jewelers file, around and around inside to thin out the edge. Then add some smaller diameter tubing just jutting out of the top as I see on most of the units around here. It must be a product of recent shoppings.

Jim

 

[mickoo]

Jim,

Sure, it's quite easy, actually easier than it was to cut two simple straight lines in the plastic body

I used to be a Plasticard man but I'm finding brass more tolerant to my ham fisted working and it's strength over Plasticard in the thinner sizes suits me. I didn't used to like it to be honest, but over time I've grown used to it and find myself more and more resistant to going back, in addition, when soldering, if you get it wrong you can take it off, clean it up and have another go.
With Plasticard, once it's stuck...it's stuck....well not in my case as nothing seems to stick to this model, mind my Butone solvent hasn't turned up even after ten days, I reckon the Pat and his cat are sniffing it

I'll do a quick photo tutorial tomorrow night, you only need a few basic tools, some 0.010" brass, a steel rule, scribe, skrawker, a half decent smooth flat needle file, soldering iron, some 188 °C solder with a dash of flux and some abrasive paper to clean it all up, and for a real dash of razzamataz, a fibre brush to polish it.

All the best

Michael

 

[Big Train James]

Much obliged. It's the clean cutting of parts prior to the forming that I can't seem to manage to the quality I prefer. But I'll take tips on everything from start to finish. I once tried making up a jig out of brass shapes. It was an awkward job as I couldn't get the parts right before fabrication, which made the putting together an exercise in futility. Maybe I just don't have the right tools. Agreed on strength on thinner sizes. Add to that the fact that MEK is pretty aggressive for thinner sheets. I have used one of those green scrubby pads both before and after soldering.

Looking forward to the tutorial .

 

[Dog Star]

Why leave any stone unturned?

Some of those WTers who have been building the JLTRT kit of the Western engines (Jim, known as Wessies, Wizzos, or just plain 52s) did turnover the stone and have added 7mm scale copies of newspapers on the top of the driver's desk. What are you going to do in a similar vein?

regards, Graham

 

[mickoo]

Ok another long and boring post, you have been warned.

How to make a simple brass box in 0.010" sheet, there will be many ways to do this and many techniques, but this is how I do it and understand some fundamentals. Total time along with posing for photos was around 40 mins.

There's a fair few photos so I'm going to split this into three parts, making the parts and a little soldering, soldering the rest and finally a rough idea of how skrawkers work which should help you avoid some pit falls.

Ok let's start with the basic set up and tools.


A rule, brass sheet cut to size, square, scribe, skrawker and a nice worn piece of abrasive paper, I have several pieces around the bench, each being the same grade initially but over time they get smoother, so a really worn piece ends up more like a polishing sheet.

I'm assuming the sheet was cut square and the next step is to mark the two corners where we wish to bend, in my case, 15 mm from each end, using the square make two fairly heavy scribe marks, this will help the skrawker with it's first cut and reduce it skidding off across your work.

Having made your two marks take the skrawker and make a light cut along the line.

In this instance I have made several cuts and we can see the material already beginning to bend as the thickness in the groove is reduced, to stop this binding the blade it's a good idea to gentle ease this flat every few cuts or so, or use a harder material to cut on, the blue mat is mildly soft so allows the material to flex. You'll know when you get a good cut as a small pig tail of swarf will come off the blade. I'm sure the blades can be sharpened but this is still the same blade out of the packet over two years ago and it's still cuts almost like new. There are a few tips with using a skrawker which I'll explain in part three.



A close up of the groove we have cut, if you look really closely you will see that right at the end of the material the blade has cut through the material, as your cutting the groove the blade has resistance from the material in front of it, which limits it's depth (given a constant application force) but as you near the end of the piece the material in front of the blade reduces, right at the tip there will be almost no material in front of the blade and less resistance so the blade actually starts to dig deeper.

Anyway, how deep is deep enough? The depth depends on how sharp a crease you want, the deeper it is the less material is left at the bottom, the easier it is to bend and the sharper the bend, but! The sharper the bend the more fragile it is, we'll cover that shortly. I have a picture that explains this better in part three.

Ideally you need to be looking for a pretty good mark appearing on the backside of the material.


Once the two grooves have been gouged out, bend the material until it is 90° don't bend it too much at this point, three or four bending in and out will break the joint, this is actually a very good way to cut the material in the first place, make a nice deep cut in the material and then just flex the joint between your fingers and it will snap off nice and clean...ish, you still need to dress the ends with a good file.



One thing I did do before any cutting was to make sure all the edges were cleaned up and as flat as possible, this saves working on the piece later as it will be more fragile as a box than it was when flat.

So now we have a nice square trough, but we have weak joints so we need to strengthen them. Now when soldering you can carry the solder to the joint on the tip of the iron or you can place the solder near the joint and use a lightly tinned iron to heat the work and let the solder flow, I use the latter as some solders are very free flowing and once they get on the tip just flash over and spread all over the tip, not very accurate, some other solders I have ball up on the tip and are very accurate as you can just aim the small blob right into the work.



Lots of flux, yes probably way too much but I've always added lots and this is inside and I want to make sure the solder gets right into the crease, in the middle a blob of solder.



Nice big tip to the iron and set to 300°C as we want a quick in and out, I'm using 188°C solder for strength on this joint. I approach the solder from behind and slowly (maybe two or three seconds) edge the tip toward the solder, this is pre warming the metal so when the tip touches the solder it flashes into the joint, as soon as it flashes over I then push the blob of solder toward the right hand side in a smooth action to fill the joint, once at the end I then draw the tip back and drag any excess solder with it toward the middle, past the middle and back to the far end. Some people start at one end and go in one direction from start to stop, I almost always start in the middle and do one half then draw back and do the rest as a full pass.



wipe off the excess solder that has flashed over and examine your joints, should be nice and square and nice and strong.


Ok now the end plates, mark up and cut your end plates so that they are a snug fit into your trough, it is important to make sure the edges of this plate are as smooth and flat as possible, solder works best when the gap is as small and flat as possible.


Here's one of my end pieces, it's the right width but way too long, I've marked the correct depth and given it several passes with the skrawker and made a 30° bend. There are two reasons for this, most brass sheet at some point in it's life was shipped in a roll and try as you might it will almost always have a slight curl, if I need a really flat large piece I de-stress it by running it through the rollers, first one way, flip it over and then the other way, the curling one way and then the other reduces the surface stresses and the final roll is a light one which straightens it out, I've heard warming it as well and letting it cool naturally works as well but have never tried that.

Anyway, for such a small piece all that is a faff, but there will be a slight bend in it, or it may want to bend when heated, by putting a 30° bend in one end we produce a bend that automatically straightens and strengthens the material, the second reason is much more Neanderthal, it gives me something to hold it with when using a very hot iron just a few mm away from my fingers.


Once we are happy that it fits it's a good time to clean it up, this is often where you uncover damage to the sheet, often it's not visible when the sheet has a tarnish on it but once you start to polish it shows up easily.


In this case we can see that the material has a shallow depression all down the RH side, as this is a demo I wouldn't worry but if this was a highly visible piece that was going to be painted gloss then I'd work at it until it was gone, or simply make a new piece.

Ok intermission time, Ice creams to the left, toilets to the right

 

[mickoo]

Part two, soldering in the end plate.

I start with one corner and just dab a very small amount of solder on.


In this case the joint on the right. I use the soldering tip as a level and place my small piece of solder there, by raising the end piece it will eventually hit the bottom of the tip and be the same level as the side pieces, in reality we want it a few thou below the side pieces.
Having soldered one corner we can use that as a fulcrum and move the other corner up or down by way of the large holding flap we had, sort of like a see saw. In reality it doesn't matter if the first joint is perfect the first time, only that we can flex the end piece to make sure the second joint is perfect. Once the second joint is perfect we can go back to the first, reheat and adjust it's height by using the second as the fulcrum point.

The important part about the second joint is to not have too much solder along the top edge, as this will prevent the front plate from flexing when we try and line up the other side.



In this case I had too much, but luckily the other side was pretty much lined up. If you get it wrong then you will have to bend the front plate up or down to get the third joint just right, once you have that right there may be small curve in your face plate, don't worry, just go back to the second joint along the top edge and heat it, it will ease it's self pretty flat once the solder begins to flow.



The third joint is the next corner along the work piece, again we need the face plate just below the sides, a good way to check this is to run your finger nail over the edge, if you feel a small lip then it's right, if you feel nothing then your face plate is too high and you will not get a sharp edge, but a rounded one when it's cleaned.



Finally we do the last corner, each time we use the last joint as a fulcrum to place the face plate in the right place.

Going back to the curve we see in sheet brass, we can see that the top has begun to curl, I've actually exaggerated this with a pencil underneath, the original gap being too small for the camera to pick up, using a small scrap of wood hold the top face flat against the front piece, apply your nugget of solder, flux and heat.


Once the centre is soldered then fill the rest of the joint and you should end up with something like this.


Next stage is to get all that solder off and trim the edge, use abrasive paper to get most of the solder off as it will stop it getting into your nice expensive but very smooth sharp files. When filing file from the outside in, as you take the edge down it will begin to remove what little solder is left in the small lip until it has all gone, now the two edges are one.



I still need to do a little more to the back edge as you can just still see a thin hint of solder, and the front nearest corner still has a small lip casting a small shadow.

Once it's all cleaned up it's time to remove the hand hold we left on the front face, this has been giving the part extra strength whilst we were cleaning it up, but it's purpose is fulfilled so simply bend it back and forth a few times and it will break off. This is probably where experience helps, if the groove you previously cut wasn't deep enough it will try to flex your new soldered joints, it was too deep then the joint would have been too fragile and it'd probably already have fallen off by now.



An extreme close up of the joint left by the skrawker, it has made a clean cut through about 75% of the material but the bending to fracture whats left has left a nasty jagged edge which needs dressing with a file of weapon of your choice.

Finally


Yes it is on the wonk, one side is 15.15 mm high, the other 15.85 mm, good job it's a test piece as that'd be a bin job, or cut up for spares for other smaller work required.

Advice, you will almost certainly burn your fingers, at least once, maybe twice, you will probably also stab yourself with the tip of your very expensive but sharp needle file and finally, if it fits first time, well done, chances are it might take two or three attempts to get it just right, maybe not this time, but next time or the time after Expect some wastage as you gain experience, don't fight it, accept it and learn from it. Here endeth the second sermon.

 

[mickoo]

Skrawkers, some notes, these are my own thoughts and views on how they work from practical observations and experience.

First off the end result we are trying to achieve, skrawkers can be used for two things, making a groove to make a bend in the material, making a groove to cut the material. For the second part we just keep going until the depth feels right and then fracture what's left by bending between our fingers, the deeper you go, the easier to bend and fracture, but often you don't need to go as deep as you think, especially if you use a vice or other firm holding device on one side of the joint.

The first use is more interesting, it's use as a tool for making bends and creases.

I suppose the first step is to examine what we actually need to do, I'm sure this has been done to death before by many others more learned than me but here goes.


At the top left is a diagram showing a perfect skrawker cut, depth C is the critical measurement, the shallower this is the sharper the bend will be. To achieve a good 90° bend then gap A has to be at least 1½ times the thickness of the material, you might be able to get away with a little less but not much and probably no lower than 1.25x material thickness. At lower left is the material folded up, the thin material at C has produced a nice sharp corner and the 1½ material thickness at A has left a small gap along the joint, which we will seal with solder to strengthen the joint.

On the right we see a groove that is too shallow or a gap at A that is much less than 1½ material thickness, when we bend it the gap closes up too soon and we cannot get a nice sharp bend, in reality we would probably carry on bending this and end up with an even more distorted bend as the bending would travel back from the corner to the surrounding material.

I use a Tamiya skrawker, it's blade width is 0.52 mm which means it's safe to use on material up to about 0.34 mm thickness or 0.013". I could probably push it to 0.015" which would reduce the 1.5 ratio to about 1.3 or something and still get a nice crease but for materials above that then I'd have to use a bigger skrawker, or still use the Tamiya one for the depth but open the top of the cut with a triangular needle file.

When you take your first cut, do it just inside the front edge


If you try it like the left hand view then your digging straight into the face, it'll only end up in tears, either blood or a skrawker running amok and shooting off across the work surface, once it makes a groove, it will always try to track back to that and you won't get a neat groove, not much of an issue if the groove it to split the material, but for a bend it might show in the end result.

It is far better to start just inside the edge on a nice flat surface, however that will leave the first part not cut, so to get around this we cut from either end.



In the top image we draw to the right and after two cuts will have a small area shaded blue uncut, so we reverse the cut and come back the other way, the third and fourth cuts will soon remove that lump but create there own at the other end, which cuts five and six will remove...and so on.

I mentioned before about the last part of the cut digging deeper, the third and cuts show this, greatly exaggerated of course, but as the material in front of the blade reduces then it has a tendency to dig down. One way around this is to make the material wider, make your groove and then trim back the edge to where the groove is nice and level, you will also find when you look at the material from above it will have two fingers on each side as the material has been 'pulled' out of the groove.



It's hard to see and it' is really small we are talking about here, but if you run your finger over it you'll feel it.





If we blow up a previous image you can just see the fingers and end of groove deformation, it's just something to be aware of and focus on when cleaning up for a nice neat square corner, any gaps will be filled with solder anyway so you should end up with a nice neat finish.

That's about it, hope it helps.

Right, time to hit my Flickr groups and fill up my image collection, think I'll start with BNSF first, then CSX, UP and Euro zone

Enjoy

 

[Dikitriki]

Hi Mick,

That's an excellent guide. Thank you for putting the time and effort in. I rather think a copy in 'Techniques' would be of benefit as it will eventually get lost in this thread.

Richard

 

[oldravendale]

Thanks for going to so much trouble to do this, Mick. My major use of a scrawker has been to create a groove as the basis of a break point when building up bits of scratch additions to kits. However, the step by step instructions and details of the physics involved will make preparing more complex shapes that much easier.

Brian

 

[Big Train James]

Mick,
Thanks so much for posting this. And although the end result is "on the wonk", it's a very crisp, tight wonk none the less. I'm sure it will take some practice, but it looks relatively straightforward. It's interesting how such a small bit of solder is sufficient for the length of joint.

One thing I wonder about is what seems like getting the solder to flash by actually touching it with the iron. Is this how you are doing it? My impression is that this can lead to cold joints. I wondered quite the same thing when reading through the recent silver soldering thread.

It seems the key to me is starting with well formed parts. Like hanging drywall, anyone that's done it should now know that starting with a good framing job will make finishing seams and such a breeze. The other way around, not so much.

A second question I just thought of is how do people cut shapes like brass tubes or angles, getting nice right angle ends without distorting them. I needed to do this for a gluing jig and using a rail type razor saw could never the bits right. I would have loved to use a dremel and cut-off disc but the length of tube I needed was longer than the distance from disc to dremel housing.

Sooner or later I will need to form some sheet and long solder joints for a loco frame. This tutorial plus some practice will help tremendously!

 

[BrushType4]

Great Stuff @mickoo More more!!

 

[Yorkshire Dave]

A repeat of previous comments - a very good, clear and concise tutorial .

 

[mickoo]

Jim,

Ok on the angle and tube cutting you need to be aware of the wall thickness and the teeth per inch (TPI) of the cutting implement.

For a good clean and smooth cut there must be at least three teeth in contact with the cutting surface at any one time, preferably more, the more there are the better the cut will be. Your razor saw should have a marking on it, or the packaging with the TPI.

Let's say for arguments sake it's 50 TPI, that is one tooth per 0.5 mm (roughly), using the 3 TPI figure then the thinnest material you can cut and get a good cut is 1.5 mm, I suspect though that your razor saw is designed for plastics and such and is more for ripping than sawing metals, so it's going to have a TPI around 30 or 40 which means your minimum material thickness jumps up to 2 or 3 mm thick.

Here's a very rough picture to visualize it.


On the left is a tube with a wall thickness of 1 mm and we are using a 50 TPI...ish, when we begin the cut there are plenty of teeth in contact with the material, but as we get to mid depth then it becomes less than three, now if your really good then you can count the ones the other side but normally we humans can't make a level cut and cut on one side more than the other and never get the full 5 teeth across both faces, the end result is either a broken blade or more usually a ragged rough cut.

On the right is a piece of angle about 1.8 mm thick we can get three teeth to touch the material and it will cut but it'll be a mess in reality, however if we angle the blade like we have at the top then we get more teeth in contact with the material.

Good smooth cutting is about matching the blade to the material thickness and ensuring you have more than enough teeth in contact with the material, nothing more, nothing less, either angle the blade or get a finer blade, for stuff like that I'd use a piercing saw which have tens of teeth per inch, they are marked as 2/0, 4/0, 6/0 etc in the finer grades, I always have at least 20 or so in each size but go through the 4/0 the most as they are the general size for most materials, but I use a 6/0 on thin brass sheet for a very fine cut.

http://www.guildofjewellerydesigner...cing-blade-sizes&catid=46:reference&Itemid=56

As you can see a 6/0 has 76 TPI so the thinnest material you can cut on the edge should be 1 mm, however I have no problems cutting 0.005" half tabs on etches with that blade especially if angled at 30° or so. Why piercing saw blades do not snag like large blades with the same TPI I do not know. The only downside to piercing saw blades is that they are fragile and designed for detailed work and have a very narrow blade, which makes cutting straight lines difficult. Normal saws have a deep blade and it is the blade in the material already cut that guides it in a straight line.

I'd have to see your material to advise which saw would be best.

Flashing the solder, that depends on how you use the term, I use it to vocalize the solder actually flashing along the joint (bit of Mickism creeping in there maybe?). Some might refer it to the solder just changing state, usually about the same time the flux flashes to a vapor, some don't, some paste fluxes just change state but liquid ones usually flash off.

So long as your work is clean and fluxed and you have matched your flux to the solder you are using (some are critical, others are more general and robust in which fluxes they work with) then you should be fine. Heat is also important, many people namby pamby around with an iron that is either too small or too cold, get it hot and get in fast.
Preheating your metal first helps, which is why I creep up on my blob of solder before I touch it, the tip is already in contact with the metal and heating it up, if left long enough it would melt the solder, but by then all of your flux has flashed off and you'll end up with a dry joint as the solder will not run.....that's my experience.

The size of tip helps as well, in the above I used a big tip, this really holds the heat, when you touch the tip to the work it really soaks up any heat in it and the iron has to heat that all back up which takes time. It's easy to quench a match flame with your finger tips, try and quench a burning log...no don't....but you get my point, both are as hot as each other, just that one has a bigger kick.

Regarding the amount of solder, what I used there was way way too much, in fact if that was on a loco then I'd probably use only that first blob to solder both ends in place, remember, what ever doesn't go in the joint, you have to clean off.

That's why joint preparation is important, the flatter and squarer the joint and the smaller the gap then the less solder you need. There are guys here who use even less, and some use micro torches to heat the work, again very hot, very local and very fast, mine are on order and should arrive this weekend and I'm keen to try them out.

For a soldering iron to work it needs to transfer the heat, it does this by having a very thin layer of solder already on the tip, called tinning, you can have a tip temperature of 400°C but with a dirty tip it wouldn't even melt 150°C solder, the heat will not flow through the crap on the tip, so, a good clean tip is important, however when your soldering something onto a model you rely on this tinning to transfer the heat and melt your additional solder to make the joint, unfortunately even if you just used a whiff of solder for the joint the work will still have a residue of solder, this has come from the tinning and is a residue which is hard to stop.

With a micro flame you are not touching the work at all, so no tinning residue is left, you can either directly tin the parts first and hold in place, or use a solder paste, a very fine cream of solder and flux, smear the smallest amount between the surfaces and heat with the flame, because there is no excess flux the solder will not run all over the place and only go into the joint, leaving....one hopes.....a perfect clean joint requiring virtually no effort to clean up, that's how the silver soldering guys get such a neat joint, as do the guys on here who soft solder with a micro flame.

The other way to get neat joints is with an Resistance Soldering Unit (RSU) basically you electrocute the poor little blighter, as the current passes through the work it heats it up and flashes off the paste and the solder flows, unlike the micro flame you do have to touch the work, but unlike a soldering iron you do not have to tin the tip so no solder residue left from the tinning, RSU's get very very hot very very fast and can melt small detailed parts in an instant of your not careful.

Each tool has it's place, some work with one and are forever happy, I can foresee the use for all three in my techniques.

I will close by saying that I only dabble at this lark, there are others here who positively excel with exceptionally neat clean detailed work and know considerably more than my half pot explanations above about soldering and the darker arts.

I'd be happy to be corrected if anything is wrong

 

[Big Train James]

Thanks again for all the great info! I've just taken a look at piercing saws on the internet and lo and behold I have one in my dad's old toolbox. I had no idea that's what it was though .

I really need to invest in some tools if I'm going to keep doing this sort of work. I need a pin vise and bits for sure, a bench vise and machinist's vise would both be handy, perhaps a Sherline end mill or lathe.....settle down Jim! I'll start with the piu vise and bench vise.