Locomotive design-Help

[Spitfire2865]

Hello,
Im looking to design and build a loco but there are a few key areas Im unsure about.
Obviously the first thing to nail down would be the chassis. Now Im thinking of building a Neilson 0-4-0 tank so going around corners isnt going to be very difficult.
However, what do all of you tend to use for chassis thickness, distance over chassis, chassis construction, hornguides, etc?
I unfortunately dont have machining facilities available to me, so Ill need a lot of components to be ready to use.
Can anyone offer assistance?
Thanks!

 

[Mike W]

Trevor,

You could get the frames pantograph milled from a set of plastikard patterns twice full size. Or you could get them laser cut from steel, using a CAD drawing which is probably more your thing. With adequate crossmembers for such a small engine I suggest a thickness of around 1.5mm – a bit overscale but not a lot.

Consider what you want to do about crossmembers. You could use brass bar, cut to length, drilled and tapped, like they do in the smaller scales, or you could laser cut them too, and with slot and tab solder the whole frame together. My Manning Wardle is made like that, as is Geoff’s J65. You could make the motion plate correctly shaped as one of the spacers.

Hornguides. If you laser cut the frames, then laser cut these two, align using laser cut holes with rivets as dowels and solder them up too. The frame now starts to be a strong lump. After soldering lightly clean up the inner faces with a large file (shock, horror – but it works!). But consider what commercial axleboxes you will be using so you get the width between horns correct.

What will you do for wheels? Slaters might be OK, but I suspect you would appreciate the detail in a Mark Wood wheel. Or, 3D CAD it, get solid printed yourself and use as a pattern for casting in iron as I did for the LNWR Cauliflower.

If you need any assistance, I am sure the G3 community here will rally round and get over any hurdles you may come across.

 

[Spitfire2865]

[QUOTE="Mike W, post: 161938, member: .[/QUOTE]
Id definitely be looking to have the frames lasercut, and tab and slot construction would be useful. Though I might consider a means of bolting it together with brackets to avoid soldering so I can use steel.
Hornblocks, do you know of commercial ones for slaters 1/4" axles? Ive looked around but cant find any. Slaters looks like they do one but they dont have a photo so Im unsure.
Wheels, slaters has a 3'6" wheel for a class 02, but Im not sure if the balance weight is cast with the wheel or not. Its 2 extra spokes but Im not too bothered by that.
As I have no machining tools, know no one with them, nor want to commission them from a professional for cost reasons, Slaters looks like my only source.
Ill have a go tonight drawing up the frame profiles from my drawing.
If I am correct, Slaters G3 wheels have a rear boss that I have to consider with frame width. I dont want to make it too wide or too narrow.

-Trevor

 

[Mike W]

You can solder steel Trevor. In fact it solders really well. I use an 80w iron, lead/tin plumbers' solder and Bakers Fluid. I can hear howls of woe from here and I know that's an old fashioned method, but if you clean up straight away it makes a good strong joint.

However, I can understand the wish to be able to dismantle it at a later date .... I think?

Am sure another G3 builder will be along in a minute with his J65 to discuss widths.

I have some axleboxes. Will dig them out and drop you a line.

If you saw Mark Wood wheels turned by a professional here, you would LOVE them! Mark sells a G3 form tool, so that shows there are people turning them. But your own CAD would be better still.

Mike

 

[geoff_nicholls]

Yep, here's the other G3 builder. I don't like soldering, and hate soldering steel, but Bakers Fluid seems to work. I cleaned the metal first with very fine wet and dry. And wash it thoroughly afterwards.
I found a combination of vertical and horizontal cross pieces in the frames meant I could assemble it dry and hold it in my (gloved) hand while tack soldering it. You can see the results in my E22/J65 Thread.
Mark Wood does have Neilson wheels in his catalogue, I've just checked. If you specify electrically insulated wheels, the insulation sticks out the back by about half a millimetre. If Mark only supplies the wheels as blanks, then Walsall can machine them for you. Either will ask you what you want to do about crank pins.
I recommend Mike's sprung hornblocks/axleboxes. NB the axleboxes stick out about 0.5mm fro the outsides of the frames
I'm happy with the frame overall width of 55mm measurement for my 0-6-0, you should be okay with 56mm, but bear in mind the comments above.

 

[jamiepage]

Trevor,
The only thing I might add is that, unless you prefer steel, (and if so, 1.2mm thick would be fine), then nickel silver or brass should be perfectly ok for the chassis, I would have thought?

A small G3 loco can be significantly smaller than a large O gauge loco.

Here's a link to a small G3 electric loco; a different prototype to your Neilsen but similarish size I would imagine.

G3 Hellingly Hospital Loco

The chassis was built up from .036in NS, soft soldered.
(.036 was used partly because it was to hand, but also because 3/4in seemed not unreasonable for the prototype frame thickness.)

I'm impressed with Geoff's 55/56mm over outside of frames, and will take that on board for future models.
I have to date only used 54mm outside, (inside frames dimension varies with frame thickness), using home- grown axleboxes with 1.5- 1.6mm flanges (and 1.9mm for fixed axles).
Even on my small live steam locos, it does seem unnecessarily blacksmithy, so I will definitely fine that down a bit in the future. I like that.

ps The Slaters wheels used on the Hellingly Hospital loco had no 'raised' centre boss on their rear face. The rear was dished, but centre boss and flange all sat on the same plane. I suspect (but don't know) that their other wheels might be similar - but worth checking with them first.

Best of luck.
Yours
Jamie

 

[Spitfire2865]

Well, Ive taken Geoff's 55mm over frames with a 1.5mm frame thickness.
The Mark Wood wheels are tempting. Ill have to inquire about costs.

Anyway, Here is what I have so far.

The framework with chassis, footplate, bufferbeams, and spacers. The forward spacer is designed to cradle the smokebox and interlock with it. Everything would slot together and it might actually hold itself together without much clamping while soldering.

And the superstructure so far. Smokebox, tank, and firebox are all separate pieces which would be 3D printed.


All Id need to do is add the hornguides to the chassis plates. Id expect 1mm travel on each axle to be more than adequate on such a short wheelbase. If I decide I cant be bothered with hornguides, I might be able to do 3 point suspension with the front axle rocking, though I would prefer proper hornguides.

You may rip it apart if youd like. Ive most certainly forgotten something important.

 

[geoff_nicholls]

Is it designed to be RC or two-rail powered? I think last time I measured this loco, you could fit twelve AA batteries in the tank. Walsall Model Industries produce castings of piston rods and guides, originally intended for gauge 1, which may be suitable.

 

[Spitfire2865]

Is it designed to be RC or two-rail powered? I think last time I measured this loco, you could fit twelve AA batteries in the tank. Walsall Model Industries produce castings of piston rods and guides, originally intended for gauge 1, which may be suitable.

I was hoping for RC, but I realize fitting it all will be difficult.
I was going to 3D print as much as possible, but castings for piston rods etc would be useful.

 

[unklian]

Can I start a queue for a set of bits too please ?

 

[Mike W]

I agree with Jamie that brass would be fine for the frames. The reason I suggested steel is that many laser cutters won't cut brass. They cut steel all day long, so know the machine settings, but anything else is new to them.

 

[Mike W]

One more thought, again to raise eyebrows among some - with such a short wheelbase I think you would get away without springing or compensation and just make it solid, though it could thump over joints a bit more. For me, the main reason for springing is to ensure all wheels are on the track at all times, but I think it would be OK.

 

[Spitfire2865]

Can I start a queue for a set of bits too please ?

As with my work over in my workbench thread, I am more than happy to provide all designs I make to anyone for their own use. Though for this, Id like to build it first before putting anyone in a position of an "unbuildable kit"! I dont trust myself to not make a stupid error. I did recently figure 1.5 + 3 =3.5 in some calculations.

One more thought, again to raise eyebrows among some - with such a short wheelbase I think you would get away without springing or compensation and just make it solid, though it could thump over joints a bit more. For me, the main reason for springing is to ensure all wheels are on the track at all times, but I think it would be OK.

I considered it, but as its my first and probably only loco for a good while, Id like as much experience as I can get. And I dont very much trust my chassis building skills, even if I design it to fall together.

 

[geoff_nicholls]

An alternative for the chassis might be etched brass. Two layers of 0.7mm thick brass. That way you can include folded up hornblocks which are compatible with Mike's sprung axleboxes. I used this on my (as yet untested) ECR 2-2-2WT. And there's plenty of room on the brass sheet for any other parts you might need.

 

[Spitfire2865]

An alternative for the chassis might be etched brass. Two layers of 0.7mm thick brass. That way you can include folded up hornblocks which are compatible with Mike's sprung axleboxes. I used this on my (as yet untested) ECR 2-2-2WT. And there's plenty of room on the brass sheet for any other parts you might need.

Brass is nice to work with, but Id expect it to cost me a lot more than lasercutting from the companies I use. The laser company actually has really reasonable rates. For reference, the last order from them, a w iron cost me £0.84. So Id estimate a whole chassis somewhere around £90 unless theres another factor Im missing.

 

[unklian]

Do you have access to Model Railways magazine for August 1972 ? As there is a good article on these loco's in it . Would a scan be any use ? . It does show that only the earliest versions had the cast iron t spoke wheels . Others had 10 spoke steel centred wheels, so the Slaters wheels could be OK if they are without balance weights .

 

[Spitfire2865]

Do you have access to Model Railways magazine for August 1972 ? As there is a good article on these loco's in it . Would a scan be any use ? . It does show that only the earliest versions had the cast iron t spoke wheels . Others had 10 spoke steel centred wheels, so the Slaters wheels could be OK if they are without balance weights .

I dont have access to the article. A scan would be most welcome.

 

[John D]

Do you have access to Model Railways magazine for August 1972 ? As there is a good article on these loco's in it . Would a scan be any use ? . It does show that only the earliest versions had the cast iron t spoke wheels . Others had 10 spoke steel centred wheels, so the Slaters wheels could be OK if they are without balance weights .

Or.....a drawing can be downloaded at nominal cost from the Great Eastern Society's website.......HTH

John

 

[Spitfire2865]

Or.....a drawing can be downloaded at nominal cost from the Great Eastern Society's website.......HTH

John

I already have a drawing of the loco, but I dont have written articles about the loco, nor many photos of them.

 

[unklian]

So here's a teaser ! where would you like the other 7 pages sir ? Alternatively there are copies of the mag for sale on e-bay at nominal prices .