Re: Rolling Stock for Banavie Road

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

Banavie Road will need some coaching stock and I wanted a rake of the Drummond four wheel suburban stock. In S scale that usually means scratchbuilding unless you can find an etch kit that you can get re-scaled and are willing to pay the price. :'( I had got original drawings from the NRM last year and had made my own drawings from them. So I reckoned to start scratchbuilding using Plastikard as I've done before, and using the late David Jenkinson's methods.

So I made a start - actually as a demonstrator on the S scale stand at Railwells last year. The results were not all that great but i never expect all that much on demo efforts since you are normally being distracted all the time, if not by members of the public at least by your fellow demonstrators. :) Later in the year I junked the Railwells efforts and started afresh, only to find that my efforts were still not very good. Maybe it's just advancing age, or maybe I'm just getting more pernickity in my old age, but the results didn't look all that good to me. So that put me in a bit of a quandary. I needed panelled stock on the layout - if not the wee Drummond four wheelers, at least some McIntosh bogie stock. Was I going to have to go down the etched brass road however I did it, or was there another way.

I just happen to have a CNC milling machine - got for another purpose - and I wondered about using that, I had heard that milling styrene was a no-no since the heat in the cutter started melting the styrene and making a mess of any cut. But I had picked up on the Internet that using carbide cutters got round this problem, so I did a bit more digging around on Google and came up with a contact in the G1MRA who had milled some freight sides from Plastikard. So I dug up his email address and we had a fruitful exchange of information and I set up to try out the method on panelled sides.

The Drummond stock has panelling on the lower sides of the body - rather like Gresley teak stock. So I decided to deal with a side as an upper and a lower part to cut down the milling required. I've been doing a fair bit of messing around, experimenting with various combinations of feed and speed with the cutters, and also working out the best way of setting up the project so that it takes the shortest time. My first attempt at complete set of coach sides would have taken well over twelve hours to complete - for a small 28' 6" coach. :) I'm now getting times down into the one to two hour bracket, but there is still a fair bit of experimentation going on.

Here's a test that I did today - one side of a one compartment test coach side. ;)

milling03.jpg

The lower side fits on the lip on the bottom of the upper side. The rough edge on the right side of the drop light is where I have pushed things just a bit. I decided to incorporate a drop light at teh last moment and made it about five thou thick and at that thickness it looks as though the cutter has started picking at the edge and distorting it. It looks as though I will need to increase the thickness of the drop light by a thou or two to avoid this. However, the rest looks good - certainly a lot better than my earlier manual attempts.

Here's the setup

milling01.jpg

The mill is a Seig KX1 and it is controlled by Mach 3 software on a pretty basic PC running WinXP. The work table on the mill is a piece of Contiboard bolted onto the table to give a smooth surface for double sided tape.

milling02.jpg

A closer shot of the milling head with the 1mm diameter cutter at work, These cutters are a bit fragile hence the experimentation to find feed and speed settings which don't break the cutter. :)

I'll now set up to do a full set of sides - two of each of the upper parts and the lower parts.

Jim.
 

Dikitriki

Flying Squad
Plastikard Coaches for Banavie Road

Hi Jim

Fantastic!

It seems to me that you've cracked it, subject to the thickness of the droplights. It looks extremely neat, and very professional indeed - as I would expect from something (anything) emanating from your workshop.

I'm just trying to think of some Heyside applications.

Regards

Richard
 

28ten

Guv'nor
Plastikard Coaches for Banavie Road

Interesting stuff :thumbs: Being totally cack handed I found the Jenkinson method didn't work for me and I experimented with milling styrene myself and as you have shown it certainly has possibilities. A kx1 or kx3 is on my wish list and I seriously considered one before buying my laser cutter, but I felt that the laser would get more use. Have you tried milling Rowmark? it is a bit harder than plasticard but I found it responded better to milling, the only downside being that it doesnt glue with mek, but I suspect it is far more stable in the longer term.
Are you 3d modelling the sides before doing the cam?
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

28ten said:
Interesting stuff :thumbs: Being totally cack handed I found the Jenkinson method didn't work for me and I experimented with milling styrene myself and as you have shown it certainly has possibilities. A kx1 or kx3 is on my wish list and I seriously considered one before buying my laser cutter, but I felt that the laser would get more use.

The primary use for the mill is supposed to be gear making and wheel making,  but I haven't got round to that yet.  I had looked at laser cutters, but the price was a bit too much for me.


28ten said:
Have you tried milling Rowmark? it is a bit harder than plasticard but I found it responded better to milling, the only downside being that it doesnt glue with mek, but I suspect it is far more stable in the longer term.

I hadn't heard about this material but I've just found their web site and I'll have a longer look around.  The first quick look shows a lot to be interested in.

The other material I am going to use for wheels and gears is wax.  Basically,  I will machine a master in wax and that can be used to make wax masters for casting,  or the original wax can be used directly for lost wax casting.  I haven't proceeded too far down this road at the moment since I need to make some fittings in my main workshop and that has been out of commision for a few months until I could get the ceiling repaired.

28ten said:
Are you 3d modelling the sides before doing the cam?

For these coach sides I've used my original 2D drawings in AutoCAD LT and created a DXF to import into Cut2D.  This program lets me generate the Gcode for pockets or profiles for panelling and openings.  It is a bit laborious for the full side of a coach but it is a time saver if all the original, accurate dimensional work has been done already in 2D.    Cut2D also lets me arrange tool changes quite easily.  At the moment I use three cutter sizes to do this coach side to suit the panel radii and to give the quickest results.  Things are all a bit empirical at the moment as I try and work out what the optimum speeds and feeds are for the carbide cutters, and it could be that I finish up using the smallest cutter for everything if I can drive it hard enough without breaking.

I use Rhino3D for 3D work and I import the results into Cut3D to generate Gcode.  I have done a part of a coach side in 3D and will probably look further at this method if I have to make new drawings of coaches and use Rhino instead of ACAD LT.

I'm also getting a bit adventurous and I'm hacking the Gcode files for speed instead of going back into the CAM software to do the amendments.    However,  Mach lets me preview my moves just in case I drop a clanger with the hacking.  ;)

Jim.
 

28ten

Guv'nor
Plastikard Coaches for Banavie Road

The main supplier of Rowmark is just down the road in Brizzle http://www.identify.co.uk/ well worth experimenting with, it is also  plastic of choice of lasering because it withstands the heat, which makes it better for milling with a faster feed rate.
I saw John Stevenson give a demo of the KX3 where he milled a wheel from solid in a couple of hours, very impressive for a hobby machine.
I do find that time spent 3d modelling saves mistakes in the long run, I use a combination of Autocad LT and Solidworks with a bit of Sketchup thrown in for good measure :) Strangely I couldnt get on with Rhino the interface confused me  :scratch:. It is many years since I have worked with Gcode, but direct editing is so much quicker and you never quite know what computer generated code will end up doing  :headbang:
 

Steph Dale

Western Thunderer
Plastikard Coaches for Banavie Road

Fascinating thread this.  It strikes me that this is about the only method that would allow the correct profiles to all the beading; I s'pose that engraving might be simpler and the cutters are simpler to make to the profile.  As far as I'm concerned it's the same technology anyway...

I've got good results out of Jenkinson's methods and my first coach is nearing completion now.  The second and third are planned and I'm starting to collect parts for their construction now.  What you're talking about here represents the opportunity to productionise such techniques.

Of course, the next stage is to mill out the negative of the part and use a hot plate or moulding technique to get your parts.  With panelled stock this approach works well - Ian Kirk coaches give the right sort of idea with the repeated elements being moulded seperately.

Just a couple o' thoughts!  I look forward to seeing how you get on!

Steph
 

Jordan

Mid-Western Thunderer
Plastikard Coaches for Banavie Road

JimG said:
Here's a test that I did today - one side of a one compartment test coach side.  ;)

[attachimg=3]

From here at the Back of the Class all this Engineering stuff just looks amazing! Puts my bodging right down at the bottom of the heap!! :))
Hope no-one minds if I just stand quietly at the side of this thread and  :drool: :drool: :drool: and  :bowdown: :bowdown: :bowdown: as things unfold....  :thumbs:
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

28ten said:
The main supplier of Rowmark is just down the road in Brizzle http://www.identify.co.uk/ well worth experimenting with, it is also  plastic of choice of lasering because it withstands the heat, which makes it better for milling with a faster feed rate.

If they are down the road in Bristol,  I might pop down and see the materials on offer first hand.  There's a huge amount of product available and it's a bit mind-blowing at the moment.  ;)

28ten said:
I saw John Stevenson give a demo of the KX3 where he milled a wheel from solid in a couple of hours, very impressive for a hobby machine.

John Stevenson has been very involved in the development of the Seig CNC machines and he actually supplies the front line support for the KX1 and KX3.  I've also seen his gear cutting demo at the Midlands Model Engineering show using Gearotic software to generate the code and I'm looking at doing some of my own gear cutting using the same setup.

28ten said:
I do find that time spent 3d modelling saves mistakes in the long run, I use a combination of Autocad LT and Solidworks with a bit of Sketchup thrown in for good measure :) Strangely I couldnt get on with Rhino the interface confused me  :scratch:. It is many years since I have worked with Gcode, but direct editing is so much quicker and you never quite know what computer generated code will end up doing  :headbang:

I persisted with Rhino and I can now produce reasonable results in a reasonable time.  But I've often wondered if I would get on better with other packages.  I did have a go with the free Sketchup but couldn't find a way of doing what I wanted - like the complex shapes of wheel spokes.  But the learning curve in 3D is near vertical - maybe even an overhang.  ;)

Jim.
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

Steph Dale said:
Fascinating thread this.  It strikes me that this is about the only method that would allow the correct profiles to all the beading; I s'pose that engraving might be simpler and the cutters are simpler to make to the profile.  As far as I'm concerned it's the same technology anyway...

The CNC software will reproduce a lot of profiles depending on the shape of the cutter.  For most complex shaping,  something like a ball ended cutter will produce most shapes with the software calculating the tool path to do it.  Concave curves are obviously limited by the radius of a ball ended cutter but you can get these cutters down to quite small sizes - I've got some 0.4mm ball ended and I have seen smaller sizes on offer.  The major problem is that they are very fragile and very expensive.  ;)

Steph Dale said:
I've got good results out of Jenkinson's methods and my first coach is nearing completion now.  The second and third are planned and I'm starting to collect parts for their construction now.  What you're talking about here represents the opportunity to productionise such techniques.

I used to get good results out of DJ's methods - the problem is mine not the method.  :D

Steph Dale said:
Of course, the next stage is to mill out the negative of the part and use a hot plate or moulding technique to get your parts.  With panelled stock this approach works well - Ian Kirk coaches give the right sort of idea with the repeated elements being moulded seperately.

In my case I will probably just produce what sides I need by milling.  The layout isn't that large and the stock requirements will be relatively small,  so the work of producing moulds for mass production would not gain much advantage.

If you really want high detail moulds then you might want to consider spark erosion machines working on metal masters,  which do give extremely high quality.  I can't afford them either.  ;)

Jim.
 

28ten

Guv'nor
Plastikard Coaches for Banavie Road

JimG said:
John Stevenson has been very involved in the development of the Seig CNC machines and he actually supplies the front line support for the KX1 and KX3.  I've also seen his gear cutting demo at the Midlands Model Engineering show using Gearotic software to generate the code and I'm looking at doing some of my own gear cutting using the same setup.

I persisted with Rhino and I can now produce reasonable results in a reasonable time.  But I've often wondered if I would get on better with other packages.  I did have a go with the free Sketchup but couldn't find a way of doing what I wanted - like the complex shapes of wheel spokes.  But the learning curve in 3D is near vertical - maybe even an overhang.  ;)

Jim.
I agree that Sketchup isnt ideal for things like wheel spokes, I use it literally to sketch ideas this took me about three hours and there is no way I would have been that quick in any other program
[attachimg=1]
this wheel was done very quickly in Solidworks
[attachimg=2]

Have you looked at alibre? http://www.alibre.com/ it is not as easy to use as Solidworks, but then the home version only costs £99 !

It is amazing really that we can now do so much of this stuff in our own homes, when I started playing with racing cars 25 years ago CNC machines were really the new wonder - in goes billet, out comes wheel  :))
 

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T

Tinsnips

Guest
Plastikard Coaches for Banavie Road

Thats amazing!.  I have a small milling machine but its not a CNC one. I use it to true up loco frames etc but most of the time I use it as a table for my coffee cup!.
On the BBC Points West the other night , engineers in Bristol built a bicycle from nylon powder using 3D diagrams and a highly sophisticated machine that is used to make aircraft parts. Amazing.
Most impressed with the coach sides and look forward to seeing the finished vehicle.
rgds
Graham Powell
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

28ten said:
I agree that Sketchup isnt ideal for things like wheel spokes, I use it literally to sketch ideas this took me about three hours and there is no way I would have been that quick in any other program

this wheel was done very quickly in Solidworks

Here's my attempts at the centre for a Britannia bogie wheel in Rhino

CoarseBogie.jpg

BritBogieWheel.jpg

The two attempts are trying out different widths of spokes. I don't have an accurate drawing of the wheel and I'm going by a few good photographs and trying to get it looking like the pictures. I aim to cut this in wax and get lost wax castings made which I will then turn up and fit a steel tyre to.

28ten said:
Have you looked at alibre? http://www.alibre.com/ it is not as easy to use as Solidworks, but then the home version only costs £99 !

I've had a look at Alibre but decided to stick with my rather old copy of Rhino which I picked up quite a few years ago. I might re-visit Alibre. The current version of Rhino is just under £1000 which is a bit hefty. I might try enrolling at the Open UNiversity and see if I can get a student version. :D

28ten said:
It is amazing really that we can now do so much of this stuff in our own homes, when I started playing with racing cars 25 years ago CNC machines were really the new wonder - in goes billet, out comes wheel :))

I'm sure it is all down to the Internet where people can get information and the ability to purchase equipment which they might never have known about before Google. ;) And as soon as there is a market for lower priced products, then we jump in. My problem nowadays is not getting waylaid by an information overload from the web. :D

Jim.
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

Just a bit further down the road and milling the full side for the four compartment first coach.

milling04.jpg

This is the 2mm diameter mill on the run to cut out the panelling level, and also to cut through the sheet to the finished size. There are a lot of small bits of Plastikard about. :D I sweep them off the cutting surface with a stiffish paintbrush.

And now the finished sides with the top two held together with the tape, and the bottom two separate.

Coachside01.jpg

Apologies for not cleaning them off properly. I thought I had but just noticed the odd bits as I was composing this message. :)

It took just over 3 1/2 hours to cut this out, so it is not a quick operation. I could do it quicker since I am still being conservative with feeds and speeds and some accidental experience I've had has shown that the cutters can do a bit more (forgetting to zero the 1.5mm cutter and finding that it could cut through 30 thou Plastikard, plus the plastic surface of the Contiboard and a bit of the chipboard underneath, and not break :D :D )

I'll move on and do the brake third and the five compartment third

Jim.
 

28ten

Guv'nor
Plastikard Coaches for Banavie Road

Good work  :thumbs: you could attach a blow pipe to keep the cutter free of swarf, it might also have the side effect of keeping the surface a little cooler and reducing the danger of meltdown
 

Steph Dale

Western Thunderer
Plastikard Coaches for Banavie Road

Jim,

These sides look good - I think I would perhaps take a little longer to cut them out by hand if my test sections are anything to go by.

Take care with the longitudinal joint; I wouldn't recommend using solvent for this if you're using a Jenkinson-type structure behind it.  Or, more to the point; make sure it's well supported and braced.  My 'Continental' coach has a pretty-much full-length longitudinal joint between the matchboarding and sheeted upper side.  Over time the solvent continued to evaporate out of the joint which then shrank and I ended up with a flat side, rather than having a gentle 'set' it in.

All sorted now though:
 

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28ten

Guv'nor
Plastikard Coaches for Banavie Road

Steph Dale said:
Cynric,
Would a vacuum be better - rather than blowing highly-charged plastic dust around the 'shop...?  :shit: ;D

Steph
fair point 8)  :))
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

28ten said:
fair point 8)  :))

I was thinking the same as Steph - that Plastikard swarf gets everywhere - and sticks.  :D  I have been looking at small vacuum cleaners to convert for the purpose but I'm not sure how many of the small ones are continuously rated when some of my more complex runs are nearly an hour long.

There's now a bit of a hold up at the moment.  The third class panelling needs a 0.5mm cutter, which I don't have, so it will be early next week before I can order one and get it.

Jim.
 

JimG

Western Thunderer
Plastikard Coaches for Banavie Road

Steph Dale said:
These sides look good - I think I would perhaps take a little longer to cut them out by hand if my test sections are anything to go by.

I'm not too worried about the time.    Just as long as I can get good sides.  I'm just plucking up nthe courage to walk away and leave the machine running.  Sitting watching it is getting close to watching paint dry.  I have allowed some swarf to remain on the piece to see if the cutter fouls up,  but it seems to manage to cut through loose swarf without clogging.  However,  some sort of vacuum cleaner would be advanrageous.  The one problem which might come up on unattended runs is when the cutter breaks through to the double sided tape and picks up the adhesive,  when the swarf starts forming a ball on the cutter.  I've been knocking the ball off with a cocktail stick but I might try a test to destruction to see what happens when I leave it to its own devices.    I did leave the 1mm cutter uncleaned on its last three apertures and its ball seemed to start breaking up and flaking off.  However,  earlier on the 2mm cutter,  the ball grew quite quickly and didn't seem to show any tendency to break off.

Take care with the longitudinal joint; I wouldn't recommend using solvent for this if you're using a Jenkinson-type structure behind it.  Or, more to the point; make sure it's well supported and braced.  My 'Continental' coach has a pretty-much full-length longitudinal joint between the matchboarding and sheeted upper side.  Over time the solvent continued to evaporate out of the joint which then shrank and I ended up with a flat side, rather than having a gentle 'set' it in.

All sorted now though:

I've had problems with Plastikard over the years and I am expecting some on mounting these sides - especially now that the glazing will probably have to be put in from the top and it might prove difficult keeping the top of the sides straight if I can't attach them to the Jenkinson inner box.  Since I'm waiting on cutters to do the 3rd class stock,  I might start on the coach sides I've done and use them as a test bed to see what transpires.  I also want to build a coach in any case to work out exactly how I deal with the ends before I go much further.

Jim.
 

Steph Dale

Western Thunderer
Plastikard Coaches for Banavie Road

JimG said:
I've had problems with Plastikard over the years and I am expecting some on mounting these sides - especially now that the glazing will probably have to be put in from the top and it might prove difficult keeping the top of the sides straight if I can't attach them to the Jenkinson inner box.  Since I'm waiting on cutters to do the 3rd class stock,  I might start on the coach sides I've done and use them as a test bed to see what transpires.  I also want to build a coach in any case to work out exactly how I deal with the ends before I go much further.

Jim.

Jim,

I'm not a fan of the loose roof approach on any of my coaches - whether brass, moulded styrene or plasticard.  It's a absolute bu88er of a joint to hide if it's not perfect and the roof adds a lot of strength to the cantrail area of a coach.

In the Continental the internal structure isn't too obvious and it'll be better still on the next vehicle.  Now I've got the sides stable I've decided to use real glass for the glazing, which will drop in from behind, using a little canopy adhesive to just hold it in place (if I use microscope cover slips), or possibly a crystal epoxy (if I use microscope slides).

One other thought is to choose what solvent you're using.  I have Plasticweld and Slater's Mek on the bench at the moment.  Mek is certainly less agressive than the Plasticweld but is certainly adequate for assembling the body shell itself.  I did use Plasticweld on the roof and floor assemblies as it helps with the strength of the load-bearing parts.

It's also worth looking at the ZAP range of superglues.  These seem to be the favoured means of construction for model aircraft builders these days, they're plastic compatible and have worked well when I've needed to use them in my coach.

And test-builds?  Yes, very worthwhile.  The vehicle I chose is a one-off on the layout as it's Eastern Section (ex-SECR lines) and I model the ex-LSWR area.  It's either that or I'd be making a set of ten of them!  So producing a test build in a vehicle that's a one-off for your company/period/area might be the way to go?  You can then enter series production where you need many similar vehicles with some confidence.  Certainly despite it's problems the Continental has been a great confidence booster for me.

Steph
 
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