daifly
Western Thunderer
Thanks Ian. I'll bet good money that I'm not the only one who appreciates it while following this useful and interesting thread!
Cheers
Dave
Ian_C's workbench - P4 and S7 allsorts
- Thread starter Ian_C
- Start date
Cheers
Dave
adrian
Flying Squad
You won't get good odds on that - it is much easier when the full images are embedded but then I'm lucky in having high speed broadband. However I think the smaller images help those on a slower connection as they don't have to download the large images if they are not interested.
daifly
Western Thunderer
So will those who keep telling the newbies that the currency here is lots of photos please change their mantra to 'lots of little photos in case some people aren't interested or still on dial up'. I think not!
The forum file size limit looks after things quite nicely and I have a (relatively) slow connection at my flat which copes more than adequately with big pics on here. I would imagine that most users have a similar experience.
The forum file size limit looks after things quite nicely and I have a (relatively) slow connection at my flat which copes more than adequately with big pics on here. I would imagine that most users have a similar experience.
adrian
Flying Squad
That's not what I meant - I was just trying to point out an alternative point of view and I suppose in some way I'm trying vainly to please all of the people all of the time.
adrian
Flying Squad
You're probably right.
but I prefer to be that side of the fence to the other side of not trying enough!One of a various company training courses I got sent on covered "logic bubbles". It tried to explain that everyone acts on logic but they have a bubble of what they see as a logical course of action. Unfortunately what your logic bubble is may differ to what someone else's logic bubble is , so what you see as a logical course of action or response is not the same as others as they are operating in a different "logic bubble". So now when I see things I don't understand I try to work out what "logic bubble" is at play to drive people to take the stance that they do.
Chassis jig
Ian_C
Western Thunderer
After much distraction and diversion the chassis parts got dropped onto the jig and soldered up. After all the planning and preparation it all went together without fuss and took about 15 mins to complete. I was pleasantly surprised to find that the chassis axle centres matched the jig exactly. Design, artwork and etching spot on again- congratulations MOK!
One other advantage of using a hefty slab of aluminium for the jig...you can turn it on its side to complete the soldering from above and below.
I must say, the tab-slot-twist construction on the chassis works very well, although filing off the projecting tabs after soldering is somewhat of a chore.
Finally for this posting, a mystery part...
It gets a mention as a part to remove from the etch when building the ashpan / frame x-member sub-assy. It doesn't feature in any diagrams and never gets mentioned again elsewhere in the 'structions. It looks to me like the front lower firebox plate riveted to the foundation ring but I'm damned if I can figure out how it fits in that location. It's not off the specific S7 etch so it may be a bit narrow, but still, I'm stumped. Suggestions?
Anyway I'm not sure you'd actually see the firebox rivets/stays on the prototype because they were covered with a layer of 'plastic magnesia' below the running plate for insulation.
One other advantage of using a hefty slab of aluminium for the jig...you can turn it on its side to complete the soldering from above and below.
I must say, the tab-slot-twist construction on the chassis works very well, although filing off the projecting tabs after soldering is somewhat of a chore.
Finally for this posting, a mystery part...
It gets a mention as a part to remove from the etch when building the ashpan / frame x-member sub-assy. It doesn't feature in any diagrams and never gets mentioned again elsewhere in the 'structions. It looks to me like the front lower firebox plate riveted to the foundation ring but I'm damned if I can figure out how it fits in that location. It's not off the specific S7 etch so it may be a bit narrow, but still, I'm stumped. Suggestions?
Anyway I'm not sure you'd actually see the firebox rivets/stays on the prototype because they were covered with a layer of 'plastic magnesia' below the running plate for insulation.
Cylinders
Ian_C
Western Thunderer
Finally some cylinders.
It was a bit of a hard work getting the slide bars aligned properly for soldering. In the end they were soldered on close to aligned and the slide bars slightly bent afterwards to get them perfectly parallel . Likewise the valve spindle guide. It probably wasn't the best plan to attempt this late on a hot and airless Saturday night. Sweaty and stressy with patience carefully rationed. Having learned the lessons, the opposite side was done in about 30 mins this morning without stress or sweat.
Some things to note...
As cast the slidebars looked a bit rough and they really need to be straight, clean edged and shiny in 7mm. I briefly considered making some replacements from a scrap of 3mm N/S plate. In the end they cleaned and polished up OK. The separate steel rod for the piston rod is a nice touch and that also will get polished before final assembly. All this heavy metal in the kit looks prototypically chunky.
Noting some advice elsewhere on this kit I took the time to get the relative positions of slide bars and valve spindle guide correct so that the combination lever passes the front of the crosshead with (hopefully) some clearance. We'll see shortly.
The holes in the rear castings for valve spindle and piston rod are undersized as cast (which is OK) and not well aligned with the axes of the cylinder and valve (which is less OK but understandable in a casting). They are also quite long so they naturally align the spindle and rod in a direction slightly different from the slide bars. It's difficult then (OK it's impossible) to get the piston rod and crosshead sliding freely over the full stroke. The simple remedy is to drill out the hole inside the casting oversize (I chose 3mm) to within a couple of millimetres of the gland. That way only the short section of hole at the gland provides any guidance for the rod and a slight clearance here provides enough accommodation to allow the crosshead and rod to be guided by the slidebars without the rod binding up. All of these little snags need clearing up in order to get a the valve gear working smoothly.
All but the early locomotives had two rectangular access covers on the top shoulders of the cylinder cladding. There's no provision for this in the kit so far as I can see so they were made from tiny rectangles of brass shim with rivets popped in the corners. I found it very difficult to make four identical covers this size so I made about twice as many as needed and chose the best matching pairs (and fed a couple to the carpet, naturally). Looking at photos (Wild Swan LMS Locomotive Profile mostly) there seems to have been some variation in size and shape, with some of them in later years being downright scrappy. So maybe you can get away with a slight lack of uniformity. The circular cover came in two different sizes; smaller for early locos and larger for later. I'm not sure which is represented by the etched detail on the kit but I elected to leave it as is.
The valve guide castings benefit from having the backs skimmed in the lathe to help them sit flat and square on the cylinder ends.
There will be some detailing of lubrication pipes using fine copper wire and there are still the the cylinder drain castings to add. They'll go on when all the mechanical assembly and fettling is done.
Motion brackets and associated clutter are the next job.
It was a bit of a hard work getting the slide bars aligned properly for soldering. In the end they were soldered on close to aligned and the slide bars slightly bent afterwards to get them perfectly parallel . Likewise the valve spindle guide. It probably wasn't the best plan to attempt this late on a hot and airless Saturday night. Sweaty and stressy with patience carefully rationed. Having learned the lessons, the opposite side was done in about 30 mins this morning without stress or sweat.
Some things to note...
As cast the slidebars looked a bit rough and they really need to be straight, clean edged and shiny in 7mm. I briefly considered making some replacements from a scrap of 3mm N/S plate. In the end they cleaned and polished up OK. The separate steel rod for the piston rod is a nice touch and that also will get polished before final assembly. All this heavy metal in the kit looks prototypically chunky.
Noting some advice elsewhere on this kit I took the time to get the relative positions of slide bars and valve spindle guide correct so that the combination lever passes the front of the crosshead with (hopefully) some clearance. We'll see shortly.
The holes in the rear castings for valve spindle and piston rod are undersized as cast (which is OK) and not well aligned with the axes of the cylinder and valve (which is less OK but understandable in a casting). They are also quite long so they naturally align the spindle and rod in a direction slightly different from the slide bars. It's difficult then (OK it's impossible) to get the piston rod and crosshead sliding freely over the full stroke. The simple remedy is to drill out the hole inside the casting oversize (I chose 3mm) to within a couple of millimetres of the gland. That way only the short section of hole at the gland provides any guidance for the rod and a slight clearance here provides enough accommodation to allow the crosshead and rod to be guided by the slidebars without the rod binding up. All of these little snags need clearing up in order to get a the valve gear working smoothly.
All but the early locomotives had two rectangular access covers on the top shoulders of the cylinder cladding. There's no provision for this in the kit so far as I can see so they were made from tiny rectangles of brass shim with rivets popped in the corners. I found it very difficult to make four identical covers this size so I made about twice as many as needed and chose the best matching pairs (and fed a couple to the carpet, naturally). Looking at photos (Wild Swan LMS Locomotive Profile mostly) there seems to have been some variation in size and shape, with some of them in later years being downright scrappy. So maybe you can get away with a slight lack of uniformity. The circular cover came in two different sizes; smaller for early locos and larger for later. I'm not sure which is represented by the etched detail on the kit but I elected to leave it as is.
The valve guide castings benefit from having the backs skimmed in the lathe to help them sit flat and square on the cylinder ends.
There will be some detailing of lubrication pipes using fine copper wire and there are still the the cylinder drain castings to add. They'll go on when all the mechanical assembly and fettling is done.
Motion brackets and associated clutter are the next job.
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Motion brackets
Ian_C
Western Thunderer
Motion brackets were a bit of faff on account of the instructions not being specific about the location of all the parts. In particular the lateral location of the reverser lift arms and crank had to be worked out from the drawings in the Wild Swan book and measurements taken from the model. The model does not correspond exactly to the prototype in this area. The differences are small but enough to make scaling directly off prototype drawings invalid. Still, a pleasant morning at the kitchen table in the sun measuring etched parts and sketching out the arrangement helped to clarify things.
I'd also add that the improved instructions for this kit by DavidinAus referred to in his thread Stanier 8F in S7 were a considerable help in working out which other parts to take off the etch for this assembly.
I think the intent of the kit is to thread the reversing shaft supports, arms and crank onto 0.8mm wire and solder them in position. Sure, you could do that and it would be relatively straightforward, but I don't think it would capture the look of the prototype well. You could argue that the area under the motion bracket is in the shadow of the footplate and difficult to see on the model but I like to photograph models from around scale eye height so it'll show up there a bit. There are a few areas where the kit can be improved if you want to spend the time on it:
The screen shot above shows the LH motion bracket assembly upside down along with a section of the adjacent chassis side plate. The etched back plate is not shown for clarity. The reverser arm should sit between the two motion bracket etches (with all the oval holes) and be equally spaced from the inside of each. Note that the four arm etches have different numbers on the fret, but they are all the same. The crank arm (dark green) is made by laminating the two etched arms together (it is the reach rod that has the forked end on the prototype), and needs to be positioned close to the fixing angle bracket (nasty violet colour) and between the two support plates (orange). It will be impossible to see the connection between the reversing reach rod and the crank so it doesn't matter if they don't eventually match up exactly. It does pay to get the crank at roughly the right angle depending how your gear is to be set. I pondered how to set the gear and decided that I'd set it in neutral since most of the photos I'll take will be of the loco at a standstill, and the driver should leave it in mid gear when parked. The downside is that when in motion the valve gear won't move the valve spindle much. Well, you can't have it all! Actually you can have it all because somebody, somewhere on WT has worked out how to operate the gear with a tiny servo and DCC. A bit beyond me though
.
The screen shot above shows the RH gear. Upside down again and showing the rear plate (brown) this time. No crank arm to complicate matters on this side.
The screen shot above shows the RH gear the right way up this time. The cosmetic support casting is shown here between the arm and the outer support plate. I modelled it up to look like the casting you can see in some photos with a view to having some 3D printed, but in the end I wanted to press on and made a pair from a turned boss and bits of scrap etch. You can see them in a later phot0, They fill a space and I think they'll pass muster in the shadowy, filthy gloom beneath the footplate.
The lifting arms were drilled through 2mm and soldered to a small turned spacer. Plenty of solder and some work with the thin end of a round file gets them looking more like a casting.
Rather than try and juggle the position of all the parts along the reverser shafts when soldering up the assembly I elected to make stepped shafts and different sized holes in some of the parts. The shafts take a little longer to make than a plain 2mm diameter pin, but the assembly then is much easier and everything ends up in the right place and square to the shaft. Having modelled up the various bits & bobs in CAD it was easy to design the shafts. If anybody's daft enough to follow suit the drawings are below.
Finally all is assembled to the chassis, alignment checked, and soldered up. A couple of minutes in the ultrasonic tank and you end up with this...
Note that the arms are not yet fixed to the shafts. That'll be done when I assemble the motion and align them with the radius rods. The reddish tint that is sometimes apparent on the cleaned nickel silver parts is due to a bit of electrochemistry going on in the hot ultrasonic bath. The hot solution and the agitation leaches some nickel or zinc from the surface leaving a coppery sheen.
Not sure what comes next. I'm waiting for Mr MOK to send me a replacement drop link casting that I'm missing, so I can't complete the motion just yet. Maybe I'll browse Stanier 8F in S7 for inspiration...
I'd also add that the improved instructions for this kit by DavidinAus referred to in his thread Stanier 8F in S7 were a considerable help in working out which other parts to take off the etch for this assembly.
I think the intent of the kit is to thread the reversing shaft supports, arms and crank onto 0.8mm wire and solder them in position. Sure, you could do that and it would be relatively straightforward, but I don't think it would capture the look of the prototype well. You could argue that the area under the motion bracket is in the shadow of the footplate and difficult to see on the model but I like to photograph models from around scale eye height so it'll show up there a bit. There are a few areas where the kit can be improved if you want to spend the time on it:
- The reverser gear shaft was quite a hefty size in real life and it scales out to about 2mm diameter, noticeably bigger than the default 0.8mm wire. So new shafts were made for the LH and RH assemblies.
- The reverser shafts were supported off the back of the motion bracket casting by substantial castings of their own. The etched plates in the kit don't represent this very well; looks too plain and empty up there. Some 'looks like' castings were fabricated from odds and ends and added to the outside of the support plates.
- The prototype lifting arms were machined forgings or castings and are not well represented by the pair of etched arms on the wire shaft. The etched arms were soldered to a spacer to make a more substantial sub-assembly.
The screen shot above shows the LH motion bracket assembly upside down along with a section of the adjacent chassis side plate. The etched back plate is not shown for clarity. The reverser arm should sit between the two motion bracket etches (with all the oval holes) and be equally spaced from the inside of each. Note that the four arm etches have different numbers on the fret, but they are all the same. The crank arm (dark green) is made by laminating the two etched arms together (it is the reach rod that has the forked end on the prototype), and needs to be positioned close to the fixing angle bracket (nasty violet colour) and between the two support plates (orange). It will be impossible to see the connection between the reversing reach rod and the crank so it doesn't matter if they don't eventually match up exactly. It does pay to get the crank at roughly the right angle depending how your gear is to be set. I pondered how to set the gear and decided that I'd set it in neutral since most of the photos I'll take will be of the loco at a standstill, and the driver should leave it in mid gear when parked. The downside is that when in motion the valve gear won't move the valve spindle much. Well, you can't have it all! Actually you can have it all because somebody, somewhere on WT has worked out how to operate the gear with a tiny servo and DCC. A bit beyond me though
.The screen shot above shows the RH gear. Upside down again and showing the rear plate (brown) this time. No crank arm to complicate matters on this side.
The screen shot above shows the RH gear the right way up this time. The cosmetic support casting is shown here between the arm and the outer support plate. I modelled it up to look like the casting you can see in some photos with a view to having some 3D printed, but in the end I wanted to press on and made a pair from a turned boss and bits of scrap etch. You can see them in a later phot0, They fill a space and I think they'll pass muster in the shadowy, filthy gloom beneath the footplate.
The lifting arms were drilled through 2mm and soldered to a small turned spacer. Plenty of solder and some work with the thin end of a round file gets them looking more like a casting.
Rather than try and juggle the position of all the parts along the reverser shafts when soldering up the assembly I elected to make stepped shafts and different sized holes in some of the parts. The shafts take a little longer to make than a plain 2mm diameter pin, but the assembly then is much easier and everything ends up in the right place and square to the shaft. Having modelled up the various bits & bobs in CAD it was easy to design the shafts. If anybody's daft enough to follow suit the drawings are below.
Finally all is assembled to the chassis, alignment checked, and soldered up. A couple of minutes in the ultrasonic tank and you end up with this...
Note that the arms are not yet fixed to the shafts. That'll be done when I assemble the motion and align them with the radius rods. The reddish tint that is sometimes apparent on the cleaned nickel silver parts is due to a bit of electrochemistry going on in the hot ultrasonic bath. The hot solution and the agitation leaches some nickel or zinc from the surface leaving a coppery sheen.
Not sure what comes next. I'm waiting for Mr MOK to send me a replacement drop link casting that I'm missing, so I can't complete the motion just yet. Maybe I'll browse Stanier 8F in S7 for inspiration...
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A couple of firsts
Ian_C
Western Thunderer
A couple of firsts this week.
The first first: in order to find some missing late-summer modelling mojo I popped the chassis on wheels, dropped the motor /gearbox in and ran it under power for the first time.
There you go - a Stanier 2-2-2-2, or a may be better described as a 1-1-1-A. No pick ups of course, it's wired directly to the controller. No rods or motion fitted so it really isn't much of a step forward. But it's alive for the first time, I get a sense of the thing and it's the first 7mm loco I've (not yet) built. Followed by 20 minutes of playing trains, just driving it up and down a few inches of test track. Actually took a few seconds of video of it, but not compelling viewing. So far so good.
Interestingly the ineradicable wobble of the wheels (earlier in the thread) isn't particularly noticeable when installed, and I guess it'll be even less noticeable when the rods and motion are on. Still some engineering issues to address with the wheels though, so still not decided what I'm going to do with them. There's a telescopic axle experiment brewing...
The second first: I actually wore out a piercing saw blade this week. That's the first time I've managed to do that. It's usually 'ping' long before blunt.
The first first: in order to find some missing late-summer modelling mojo I popped the chassis on wheels, dropped the motor /gearbox in and ran it under power for the first time.
There you go - a Stanier 2-2-2-2, or a may be better described as a 1-1-1-A. No pick ups of course, it's wired directly to the controller. No rods or motion fitted so it really isn't much of a step forward. But it's alive for the first time, I get a sense of the thing and it's the first 7mm loco I've (not yet) built. Followed by 20 minutes of playing trains, just driving it up and down a few inches of test track. Actually took a few seconds of video of it, but not compelling viewing. So far so good.
Interestingly the ineradicable wobble of the wheels (earlier in the thread) isn't particularly noticeable when installed, and I guess it'll be even less noticeable when the rods and motion are on. Still some engineering issues to address with the wheels though, so still not decided what I'm going to do with them. There's a telescopic axle experiment brewing...
The second first: I actually wore out a piercing saw blade this week. That's the first time I've managed to do that. It's usually 'ping' long before blunt.
Union links
Ian_C
Western Thunderer
The union links have been a pain and a subject much fretting. There are etched links in the kit that are to be soldered together and the ends opened up and bent to make the forked ends. I struggled with this. Couldn't make them consistent and couldn't get all the holes aligned and at the correct centres (8.8mm on most of the 8Fs). Some ineptitude on my part no doubt, and I know that others have managed it. The one thing I couldn't get my head around was the length of the link. I think the etched parts make a longer link than 8.8mm however you go about it.
Thought about other ways of making the things. What we want to end up with is this...
...and it's a very difficult item to make from scratch. The real thing scales down to quite a delicate little thing in 7mm. Because it has to match up with other kit parts that are slightly over size (limitations of sheet thickness etc) it ends up a little chunkier than true scale. I considered machining them from a lump of N/S, but couldn't work out a good way of doing that. I had a look at the Wild Swan Geoff Holt book. No real guidance there, but a close look at a photo of one of his Stanier locos suggested that he fabricated them from ickle bits. Lightbulb moment (fuzzy low wattage light bulb) and a way forward. What we're actually doing is this...
A bit of a fiddle and the important thing is to get all the holes aligned and at correct centres. The ends were cut from the parts supplied in the kit (after I'd straightened out my abortive attempts to bend them to shape). The sticks in the middle were cut from scrap etch.
Small soldering jig made by drilling 2 holes in a scrap of tufnol and using two 0.9mm drills as location pins. A good way of preventing the link parts from ending up soldered to the drill bits is to powder some pencil lead on wet & dry and rub that on the drill bits. Graphite makes a very good solder mask, better than a film of oil I find.
Thread the first layer over the pins and line them up with the tip of a scalpel. Solder the two centre parts together before placing them on the link ends...
Starts to get tricky now, and a couple of blobs of blu-tack hold the ends in the correct orientation while scalpel and soldering iron are applied...
Build up plenty of solder because it will be used to sculpt the right shape later. Then add the other ends and solder them up likewise.
And you end up with this nasty little nugget of N/S and solder...
Which is then cleaned up and sculpted to the right shape by needle file, cocktail stick and wet & dry and finally a rub with a Garryflex block to polish it up.
And the end result is a pair of passable (but not perfect) links that just need the fork ends cleaning out a little to fit the mating motion parts.
A note on soldering. I prefer to use a paste flux for this sort of thing for a number of reasons:
Thought about other ways of making the things. What we want to end up with is this...
...and it's a very difficult item to make from scratch. The real thing scales down to quite a delicate little thing in 7mm. Because it has to match up with other kit parts that are slightly over size (limitations of sheet thickness etc) it ends up a little chunkier than true scale. I considered machining them from a lump of N/S, but couldn't work out a good way of doing that. I had a look at the Wild Swan Geoff Holt book. No real guidance there, but a close look at a photo of one of his Stanier locos suggested that he fabricated them from ickle bits. Lightbulb moment (fuzzy low wattage light bulb) and a way forward. What we're actually doing is this...
A bit of a fiddle and the important thing is to get all the holes aligned and at correct centres. The ends were cut from the parts supplied in the kit (after I'd straightened out my abortive attempts to bend them to shape). The sticks in the middle were cut from scrap etch.
Small soldering jig made by drilling 2 holes in a scrap of tufnol and using two 0.9mm drills as location pins. A good way of preventing the link parts from ending up soldered to the drill bits is to powder some pencil lead on wet & dry and rub that on the drill bits. Graphite makes a very good solder mask, better than a film of oil I find.
Thread the first layer over the pins and line them up with the tip of a scalpel. Solder the two centre parts together before placing them on the link ends...
Starts to get tricky now, and a couple of blobs of blu-tack hold the ends in the correct orientation while scalpel and soldering iron are applied...
Build up plenty of solder because it will be used to sculpt the right shape later. Then add the other ends and solder them up likewise.
And you end up with this nasty little nugget of N/S and solder...
Which is then cleaned up and sculpted to the right shape by needle file, cocktail stick and wet & dry and finally a rub with a Garryflex block to polish it up.
And the end result is a pair of passable (but not perfect) links that just need the fork ends cleaning out a little to fit the mating motion parts.
A note on soldering. I prefer to use a paste flux for this sort of thing for a number of reasons:
- It 'sticks' the tiny parts together and holds them steady while you nudge them into place with a scalpel.
- It doesn't boil and spit like fluid flux when the heat is applied, so it doesn't 'rearrange' your carefully assembled parts
- If you have to linger with the iron it persists and and continues working after a fluid flux has boiled dry.
adrian
Flying Squad
The result looks great - I wouldn't like to be soldering all those bits together.
This was just filed from a solid bit of steel bar using just a couple of needle files. With it being that small it doesn't take long.
actually I don't think it's that difficult to make from scratch. This was my effort for my Ivatt Class 2.
This was just filed from a solid bit of steel bar using just a couple of needle files. With it being that small it doesn't take long.
Jon Nazareth
Western Thunderer
.......and I thought it was fiddly making clevis! Well done.
Jon
Jon
Ian_C
Western Thunderer
Blimey - no way I could have managed that from solid. Congratulations.
The axle experiment that's been brewing
Ian_C
Western Thunderer
Like learning to swim. Having read all the books and watched the instructional videos there comes a point where you just have to jump in and wave your arms about. So it is with going off piste with wheels and axles.
Some notes from my first attempt at telescopic axles for Slaters wheels in 7mm. There are WT folk better qualified then me to write a ‘how to’ on this subject , but since I’ve never seen it written up, and since it has proved to be a viable approach, I thought I’d share it.
As previously related I wasn’t delighted with the Slaters wheels for this project on account of the run out of the driving wheels and the appearance of the standard Slaters axle end. Following encouragement from eastsidepilot that it was possible to re-axle Slaters wheels I thought I’d have a go. I chose to experiment with the pony truck wheels because they don’t need quartering and they’d be the least costly to replace if it all went horribly wrong.
Some design considerations first…
The axles were turned from bright mild steel rod (because silver steel is a pain to turn in small diameters and we don't need the properties of sliver steel). The flat on the outer axle section was done on the milling machine in a tiny precision machine vice held in a much larger machine vice.
The next job was to work out how to bore out the Slaters axle insert to 3.8mm diameter and get the bore concentric with the tyre and perpendicular to it. A tool was made on the lathe with two recesses that are a gentle push fit for the wheel flanges (the other, larger, recess is for the driving wheels - ever the optimist!). Holes were tapped for clamping screws and a hole was made in the centre to provide clearance for drills, boring bars and to give the swarf another way out. The material was a slice of 50mm aluminium extruded bar left over from another project.
The 3 jaw chuck won’t centre the work perfectly but the turned recesses will be centred perfectly and the tool will stay in the chuck until all the wheels are bored through. If you can’t use the chuck for anything else for a while then, depending on how you are equipped, that might dictate a certain order of work. For example, if you had intended to turn the axles in the chuck then you’d need to do that first. In fact it is a good idea to turn the axles before you bore out the wheels so that you can use the axles to gauge the bore accurately to a gentle press fit as you open them out. As it happens I have a collet chuck that fits in the spindle so I used that to turn the axles. The position of the 3 jaw chuck is marked on the spindle nose so that it always goes back on the same way. The concentricity errors arising from exchanging the chuck and collet holder this way will be acceptably tiny.
With a wheel mounted in the tool and the tyre running true the first job is to reduce the projection of the wheel boss and insert to the prototype dimension. I’m guessing that the Slaters wheel boss projects from the face of the wheel as far as it does simply so that they can get all the axle end features into it (countersink, thread, square hole with sufficient axle engagement etc). As it stands the boss projects too far and as well as not looking quite right this also causes clearance problems in S7 on the driving wheels behind the slidebars (thanks to Davidinaus for the heads up on that one!). A tiny, pointy tool with a modest depth of cut (low cutting forces) was used to face the boss down to within 0.25mm of the face of the tyre. Easy enough.
The boring out of the insert requires some care. On the pony truck wheels the insert is brass so it won’t put up much of a fight but the features in the insert may not be concentric with the tyre or perpendicular to it (which is kind of the point of the exercise !), and some of the hole through the insert is square. I’ve no idea what the insert looks like or how it is engaged with the moulded plastic (but I’ll find out when I ruin one!) and all the machining forces have to be transmitted by the plastic spokes. Simply poking a drill through the middle might not be the best plan as it would have a tendency to centre up and follow the existing countersink, and a 2 flute drill opening out a square hole could be a bit rough. I started by gently running a sharp 3mm slot drill through the insert. Since it will cut on the end and the flutes it will find its own way through and not be particularly influenced by the existing geometry. That left a round hole through and was followed up with a 3.5mm stub drill.
A note on drills here. Most of the holes we drill are not very deep and a typical jobber type drill bit is much longer than necessary, and as a result quite flexible, which doesn’t help when trying to drill holes accurately. Often it doesn’t matter, but sometimes it does and that’s when stub drills are useful. They are essentially shorter versions of the standard drill bit and consequently less flexible and more inclined to drill in the direction you point them. There’s one other difference that’s not so obvious - quality. A lot of the drill bits available through the modelling or hobby engineering trade are very ‘reasonably priced’. They can also be of variable quality in terms of actual diameter and cutting geometry. You’ll probably have to buy stub drills from a more industrially oriented supplier. They cost more but are of much higher quality, they’ll have a more sophisticated cutting geometry and as a result they’ll cut more cleanly and accurately. I’ve accumulated a few HSS or solid carbide stub drills and I use them when I need to drill holes accurately. Recommended.
So, there’s now a 3.5mm diameter hole through the insert and there’s no turning back. I don’t have a 3.8mm drill or reamer, but I do have a tiny carbide boring bar for 3mm+ bores. It’s an amazing little thing and I came across it on eBay where Kyocera USA dispose of their surplus machine tool stock. There are even smaller ones for micro machining work. Cost a few dollars and a few dollars for shipment. Now, at last, I’ve found a use for it. Carbide tools are very hard and resistant to wear, but they’re not as tough as steel tools. I imagine that a sudden load on this tool would ‘plink’! It took some care to set the tool correctly in the 3.5mm bore and with held breath it was given a small cut and advanced through the hole. Very good result and no ‘plink’, so breathe out again. I’ve no way of accurately measuring bores this size so work proceeds by gradually opening out the bore until the axle (you’ve already made one, right?) just slides in with a bit of a push. If you make the hole too big you’re scuppered, so tiny cuts and repeat passes with no cut to clear out the tool deflection. It helps to put a tiny chamfer on the end of the axle. You can tell when the bore is close to size when the chamfer starts to nearly enter the hole. That worked out OK in the end and the second wheel was done much quicker.
The axles and wheels were thoroughly degreased and the wheels were fitted to the axle ends using Loctite 601. It is easy enough to adjust the axle projection on the face of the boss by eyeball before the Loctite gets a grip. Putting the wheel and axle halves back in a collet in the lathe showed that they were running true and concentric. Well, as true and concentric as the collet which is the pretty good and good enough to be undetectable on the model I think. Here’s the difference between the standard Slaters appearance and the modified wheel and axle. Much closer to prototype appearance I think. Very happy with that so far.
(Looking at the photo as I post this I think the prototype axle centre drilling is bigger than I have it . Easy enough to pop them in the lathe and make it a bit deeper. )
The next challenge is to set the back to back correctly and pin the two axle halves together. I don’t fancy my chances of juggling a back to back gauge (assuming I ever get to purchase one - the S7 Group stores seem to be mighty uncommunicative these days) and a small drill. Since I’ll have more of this to do (the 8F driving wheels, and you never know, I might even finish the 8F and start another S7 loco, if I live long enough) a bit of tool making seems to be required. A picture’s worth a thousand words (or possibly more in this thread) so here’s the tool I came up with.
It is essentially two back to back gauge faces with a V groove between them to hold the axle parts, some tapped holes for axle clamping strips, a hole through the middle where the taper pin drilling and reaming will take place and a couple of rebates on the bottom face to locate it in a machine vice. (The two tapped holes in the bottom are for the next part of the plan. The quartering jig). Easy enough to make if you have a milling machine. Impossible to make if you don’t. You need to take care to have the gauge faces parallel and within S7 B2B tolerance, and the groove has to be perpendicular to the gauge faces. Any geometrical errors in those respects and any little inaccuracies in assembly of the axle will tend to increase the actual B2B dimension so I chose to make to gauge distance toward the lower end of the tolerance at 31.22mm (well, that’s just where it ended up after the final cut so I left it at that). The material is aluminium, a chip off the same block that was used to make the chassis alignment jig earlier in the thread. The drawing for the tool is shown in the following post.
With the wheels and axle parts clamped in the tool (yes , I did line up the spokes by eye even though you’ll never notice on the model - OCD) and the tool clamped in the machine vice the hole for the taper pin can be drilled and reamed. Taper pins and taper reamers is new territory for me so thanks to those folk on WT who answered my questions on the subject. I ended up using imperial 1/16” taper pins with a matching 1:48 taper reamer from Tracy Tools. A point of note is that a 1/16” pin doesn’t need a 1/16” hole. The thin end of the pin measured about 1.2mm so the hole was drilled 1.2mm diameter (very, very carefully using a light touch on the fine feed) and then opened out with the reamer until the end just projected through the axle by about 1mm. The pin was gently pressed home before removing the assembled wheel set from the tool and cutting off the surplus pin. There’s about 0.5mm projecting from either side of the axle.
It took a couple of weeks of odd hours but in the end it wasn’t particularly difficult. I’d always felt there was an unwritten commandment ‘thou shalt not mess with wheels and axles because it’s a bit like engineering and you’ll probably make an expensive mistake’.
If anybody wishes to have a go the drawings for axle parts and the setting tool are attached to the entry after this (can't upload any more pics on this post).
With that out of the way I can press on and complete the pony truck.
Driving wheels next, and the challenge of quartering.
Some notes from my first attempt at telescopic axles for Slaters wheels in 7mm. There are WT folk better qualified then me to write a ‘how to’ on this subject , but since I’ve never seen it written up, and since it has proved to be a viable approach, I thought I’d share it.
As previously related I wasn’t delighted with the Slaters wheels for this project on account of the run out of the driving wheels and the appearance of the standard Slaters axle end. Following encouragement from eastsidepilot that it was possible to re-axle Slaters wheels I thought I’d have a go. I chose to experiment with the pony truck wheels because they don’t need quartering and they’d be the least costly to replace if it all went horribly wrong.
Some design considerations first…
- the diameter of the axle should reflect appearance of the prototype as it projects from the wheel boss
- the inner section of the telescopic axle has to be large enough to accept a taper pin
- the wall thickness of the outer telescopic section cannot be too thin
- the diameters of the various holes have to correspond with available drills, reamers etc
- we must be able to produce the bearing diameter to match the axle
The axles were turned from bright mild steel rod (because silver steel is a pain to turn in small diameters and we don't need the properties of sliver steel). The flat on the outer axle section was done on the milling machine in a tiny precision machine vice held in a much larger machine vice.
The next job was to work out how to bore out the Slaters axle insert to 3.8mm diameter and get the bore concentric with the tyre and perpendicular to it. A tool was made on the lathe with two recesses that are a gentle push fit for the wheel flanges (the other, larger, recess is for the driving wheels - ever the optimist!). Holes were tapped for clamping screws and a hole was made in the centre to provide clearance for drills, boring bars and to give the swarf another way out. The material was a slice of 50mm aluminium extruded bar left over from another project.
The 3 jaw chuck won’t centre the work perfectly but the turned recesses will be centred perfectly and the tool will stay in the chuck until all the wheels are bored through. If you can’t use the chuck for anything else for a while then, depending on how you are equipped, that might dictate a certain order of work. For example, if you had intended to turn the axles in the chuck then you’d need to do that first. In fact it is a good idea to turn the axles before you bore out the wheels so that you can use the axles to gauge the bore accurately to a gentle press fit as you open them out. As it happens I have a collet chuck that fits in the spindle so I used that to turn the axles. The position of the 3 jaw chuck is marked on the spindle nose so that it always goes back on the same way. The concentricity errors arising from exchanging the chuck and collet holder this way will be acceptably tiny.
With a wheel mounted in the tool and the tyre running true the first job is to reduce the projection of the wheel boss and insert to the prototype dimension. I’m guessing that the Slaters wheel boss projects from the face of the wheel as far as it does simply so that they can get all the axle end features into it (countersink, thread, square hole with sufficient axle engagement etc). As it stands the boss projects too far and as well as not looking quite right this also causes clearance problems in S7 on the driving wheels behind the slidebars (thanks to Davidinaus for the heads up on that one!). A tiny, pointy tool with a modest depth of cut (low cutting forces) was used to face the boss down to within 0.25mm of the face of the tyre. Easy enough.
The boring out of the insert requires some care. On the pony truck wheels the insert is brass so it won’t put up much of a fight but the features in the insert may not be concentric with the tyre or perpendicular to it (which is kind of the point of the exercise !), and some of the hole through the insert is square. I’ve no idea what the insert looks like or how it is engaged with the moulded plastic (but I’ll find out when I ruin one!) and all the machining forces have to be transmitted by the plastic spokes. Simply poking a drill through the middle might not be the best plan as it would have a tendency to centre up and follow the existing countersink, and a 2 flute drill opening out a square hole could be a bit rough. I started by gently running a sharp 3mm slot drill through the insert. Since it will cut on the end and the flutes it will find its own way through and not be particularly influenced by the existing geometry. That left a round hole through and was followed up with a 3.5mm stub drill.
A note on drills here. Most of the holes we drill are not very deep and a typical jobber type drill bit is much longer than necessary, and as a result quite flexible, which doesn’t help when trying to drill holes accurately. Often it doesn’t matter, but sometimes it does and that’s when stub drills are useful. They are essentially shorter versions of the standard drill bit and consequently less flexible and more inclined to drill in the direction you point them. There’s one other difference that’s not so obvious - quality. A lot of the drill bits available through the modelling or hobby engineering trade are very ‘reasonably priced’. They can also be of variable quality in terms of actual diameter and cutting geometry. You’ll probably have to buy stub drills from a more industrially oriented supplier. They cost more but are of much higher quality, they’ll have a more sophisticated cutting geometry and as a result they’ll cut more cleanly and accurately. I’ve accumulated a few HSS or solid carbide stub drills and I use them when I need to drill holes accurately. Recommended.
So, there’s now a 3.5mm diameter hole through the insert and there’s no turning back. I don’t have a 3.8mm drill or reamer, but I do have a tiny carbide boring bar for 3mm+ bores. It’s an amazing little thing and I came across it on eBay where Kyocera USA dispose of their surplus machine tool stock. There are even smaller ones for micro machining work. Cost a few dollars and a few dollars for shipment. Now, at last, I’ve found a use for it. Carbide tools are very hard and resistant to wear, but they’re not as tough as steel tools. I imagine that a sudden load on this tool would ‘plink’! It took some care to set the tool correctly in the 3.5mm bore and with held breath it was given a small cut and advanced through the hole. Very good result and no ‘plink’, so breathe out again. I’ve no way of accurately measuring bores this size so work proceeds by gradually opening out the bore until the axle (you’ve already made one, right?) just slides in with a bit of a push. If you make the hole too big you’re scuppered, so tiny cuts and repeat passes with no cut to clear out the tool deflection. It helps to put a tiny chamfer on the end of the axle. You can tell when the bore is close to size when the chamfer starts to nearly enter the hole. That worked out OK in the end and the second wheel was done much quicker.
The axles and wheels were thoroughly degreased and the wheels were fitted to the axle ends using Loctite 601. It is easy enough to adjust the axle projection on the face of the boss by eyeball before the Loctite gets a grip. Putting the wheel and axle halves back in a collet in the lathe showed that they were running true and concentric. Well, as true and concentric as the collet which is the pretty good and good enough to be undetectable on the model I think. Here’s the difference between the standard Slaters appearance and the modified wheel and axle. Much closer to prototype appearance I think. Very happy with that so far.
(Looking at the photo as I post this I think the prototype axle centre drilling is bigger than I have it . Easy enough to pop them in the lathe and make it a bit deeper. )
The next challenge is to set the back to back correctly and pin the two axle halves together. I don’t fancy my chances of juggling a back to back gauge (assuming I ever get to purchase one - the S7 Group stores seem to be mighty uncommunicative these days) and a small drill. Since I’ll have more of this to do (the 8F driving wheels, and you never know, I might even finish the 8F and start another S7 loco, if I live long enough) a bit of tool making seems to be required. A picture’s worth a thousand words (or possibly more in this thread) so here’s the tool I came up with.
It is essentially two back to back gauge faces with a V groove between them to hold the axle parts, some tapped holes for axle clamping strips, a hole through the middle where the taper pin drilling and reaming will take place and a couple of rebates on the bottom face to locate it in a machine vice. (The two tapped holes in the bottom are for the next part of the plan. The quartering jig). Easy enough to make if you have a milling machine. Impossible to make if you don’t. You need to take care to have the gauge faces parallel and within S7 B2B tolerance, and the groove has to be perpendicular to the gauge faces. Any geometrical errors in those respects and any little inaccuracies in assembly of the axle will tend to increase the actual B2B dimension so I chose to make to gauge distance toward the lower end of the tolerance at 31.22mm (well, that’s just where it ended up after the final cut so I left it at that). The material is aluminium, a chip off the same block that was used to make the chassis alignment jig earlier in the thread. The drawing for the tool is shown in the following post.
With the wheels and axle parts clamped in the tool (yes , I did line up the spokes by eye even though you’ll never notice on the model - OCD) and the tool clamped in the machine vice the hole for the taper pin can be drilled and reamed. Taper pins and taper reamers is new territory for me so thanks to those folk on WT who answered my questions on the subject. I ended up using imperial 1/16” taper pins with a matching 1:48 taper reamer from Tracy Tools. A point of note is that a 1/16” pin doesn’t need a 1/16” hole. The thin end of the pin measured about 1.2mm so the hole was drilled 1.2mm diameter (very, very carefully using a light touch on the fine feed) and then opened out with the reamer until the end just projected through the axle by about 1mm. The pin was gently pressed home before removing the assembled wheel set from the tool and cutting off the surplus pin. There’s about 0.5mm projecting from either side of the axle.
It took a couple of weeks of odd hours but in the end it wasn’t particularly difficult. I’d always felt there was an unwritten commandment ‘thou shalt not mess with wheels and axles because it’s a bit like engineering and you’ll probably make an expensive mistake’.
If anybody wishes to have a go the drawings for axle parts and the setting tool are attached to the entry after this (can't upload any more pics on this post).
With that out of the way I can press on and complete the pony truck.
Driving wheels next, and the challenge of quartering.
Last edited:
Axle and setting tool drawings
Pony truck
Ian_C
Western Thunderer
With the wheels and axle sorted out I've been able to finish the pony truck. The etched parts went together very nicely. I changed the way the axle bearings fit. The bearings supplied are meant to fit inside the frame and the spring castings are to be located on the projecting part of the bearing. A few issues with this -
With the spring castings fitted...
...wheels fitted and complete...
- It'll be too narrow for S7 anyway, and this is one part not covered in the S7 conversion etch.
- The holes in the spring castings are much bigger than the turned bearing, so not a good locating feature
- The backs of the wheels will rub on the spring castings, with bags of lateral free play in S7
- You have to file off some of the bearing flanges to fit them inside the frame
- I chose to make my own axle and it's not the same diameter as the supplied bearings
With the spring castings fitted...
...wheels fitted and complete...
Brian McKenzie
Western Thunderer
Super posts, Ian. Thanks very much.
-Brian McK.
-Brian McK.
adrian
Flying Squad
Thanks for the series of posts - it is much appreciated and very instructive.
The results look fantastic, thanks for the reminder about the stub drills I really should start collecting a few important sizes.
With respect to the fit of the taper pin, how good a surface finish is there on the ones from Tracey tools? I bought mine from Chronos and whilst they work ok I wasn't that impressed with the surface finish so I'm not entirely convinced that there is full contact of the pin in the tapered hole.
Thanks for the heads up about the pony truck bearings and width. Given how it has turned out do you think it would be worth trying to make the pony truck frames wider for Scale7?
The results look fantastic, thanks for the reminder about the stub drills I really should start collecting a few important sizes.
With respect to the fit of the taper pin, how good a surface finish is there on the ones from Tracey tools? I bought mine from Chronos and whilst they work ok I wasn't that impressed with the surface finish so I'm not entirely convinced that there is full contact of the pin in the tapered hole.
Thanks for the heads up about the pony truck bearings and width. Given how it has turned out do you think it would be worth trying to make the pony truck frames wider for Scale7?
Ian@StEnochs
Western Thunderer
Hi Ian,
Very comprehensive set of drawings and an elegant way to solve a problem.
I don't have your patience to make lovely little jigs but use this device to set wheels to back to back and drill for the taper pin.
Basically just a piece of bar, I have a stock of suitable sized brass but steel or aluminium would also be suitable, is turned and faced to 31.25 for S7 bb and drilled and reamed axle size. These ones are 3/16". The wheels are inserted with a toolmakers clamp holding them tight against the ends and a drill put through one of the holes, to suit gearbox or insulation, and drilled right through. Once removed the hole in the axles is reamed with a taper reamer. For driving wheels I put a pin through the crank hole into the end of the bar at the correct quartering position, see the holes on the one on the left. Different throws catered for by extra holes.
Ian