Jump to content
The Nth Degree

Fox Walker 0-6-0ST 2mm scale

Recommended Posts

More updates to the plans and it's slowly coming together. The wheels are now 2mmSA compliant but I'm thinking about making my own. Two things I've noticed by drawing the plans:

1. I need to make the components in two different thicknesses 0.25mm and 0.5mm

2. This is going to be immensely difficult!

 

Is it against the rules to draw up the plans and get an etching company to produce the parts so I can put it together? I see a couple people modifying existing etches but none who are getting their designs entirely produced, even if it is as a one-off piece.

post-11337-0-96474700-1333025678.jpg

Share this post


Link to post
Share on other sites

You're very kind Peter, thank you.

 

I've been studying the photo I have of this prototype tonight and have made quite a few small changes to the plan. I've also discovered that the boxes on the sides were also coal bunkers. They're called cab bunkers and supplemented the small rear bunker. Some industrial locos didn't have a rear bunker at all and relied on these cab bunkers entirely. I didn't know that.

 

When I've finished with these (I'm going to make two for my layout) I would love to make that loco in your profile pic - it is the cutest thing I've ever seen! What is it?

 

Hi the loco is a Manning and Wardle K class I think. I made it so long ago I cant remember. It is fro a Little Gem kit which was projuced by Jim Harris. It was nice to do and I modified some of it to replace castings with sheet brass. I would like another one now as this one was sold to pay for part of a holiday in Chile.

Share this post


Link to post
Share on other sites

Is it against the rules to draw up the plans and get an etching company to produce the parts so I can put it together? I see a couple people modifying existing etches but none who are getting their designs entirely produced, even if it is as a one-off piece.

 

I don't know if getting the model etched after you draw the plans yourself would break the rules (personally I don't think it should, but others may differ), but it might be worth making that sacrifice and dropping out of the competition if necessary.

 

One further comment on the plans - I noticed this potential problem earlier, but forgot to mention it. The holes for the axles look too close to the bottom of the sideframes - assuming you start with holes slightly too small, then have to open out the holes a little to allow the axles (or bearings) to fit, there doesn't seem to be enough metal there for safety, it's liable to bend or break, and at best will be a point of weakness.

 

This suggests two possible lines of development:

  1. The conventional route - just deepen the sideframes, making the process easier/safer.
  2. Use slots instead of holes for the axles, turning the problem into an opportunity. There are various options here, including :

  • using thicker frames (so you don't need bearings) and a keeper plate below them, which has the advantage that the wheels are easily removeable
  • using some form of hornblock mechanism in the slots, as Natalie is doing in her entry.

David

Share this post


Link to post
Share on other sites

Thanks for your observation David. I am aware of the axle hole problem but can't fix it until I know how I'm going to make bearings. I've got my axles sorted - 1.5mm carbon fibre rod - which should be strong enough and is electrically non-conductive. I've found carbon tube that's 3mm OD and 1.5mm ID but 3mm is quite a big hole to make, considering my wheels are only 7mm. The advantage of this approach is that I could have a small 0.25mm protrusion outside the frame to make sure the wheels don't touch the frame sides and short.

 

I don't really know what 'hornblocks' are but if you're talking about the brass sliding bits on Natalie's frame then that could indeed be a solution. One question: how do they stay in - do you solder them in or taper the hole so they push fit? I would guess 1.5mm - 2mm wide section would be enough to provide a non-cutting bearing hole and the carbon fibre should be man enough to last a fair number of hours continuous operation, provided it is lubricated. The length I have to buy it in would provide plenty of spare axle! If I've got my interpretation wrong, please fill me in.

Share this post


Link to post
Share on other sites

Hornblocks ala Natalie are slighting compensation units which aren't in of themselves isolated. BUT

 

You could use Natalie's idea of insulation and would be better than your carbon tube, probably. Nothing to stop you insulating your bearing the same way as hers but in a rigid frame.

Share this post


Link to post
Share on other sites
Guest Natalie Graham

Yes the hornblocks are the sliding brass bits on 269's chassis. They will be sprung but that is only because I fancied making a sprung chassis to see how it performs. There's no reason why you couldn't use the same method of insulating bearings that I used in a rigid frame. Of course you could follow the conventional method in 2mm of building the frame using insulating spacers from pcb or tufnol block.

Share this post


Link to post
Share on other sites

Thanks for your help, I'll have to think on this a bit more. As a 'thank you' to Natalie for her help and videos, a parcel arrived in the post today (the baldes are in the card wrapper):

post-11337-0-57815200-1333109902_thumb.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Nth Degree,

 

I'm really not sure about carbon fibre being non-conductive!!!

 

Again in my other hobby (RC Racing), the chassis of my car (and some of the other components) are made from carbon fibre, and I have experienced a short on my car in the past where the batteries have moved and come into contact with the carbon.

 

As a quick test as I write this post, I have just got my car out and put a multi-meter across the chassis to test the resistance - there is definitely conductivity going on there.

 

Ian

Share this post


Link to post
Share on other sites

Ian, thanks very much for testing that out but, ######! That's a major setback as I wanted to get things moving next week so I've ordered the rod and tube. I don't have a lot of spare time at the moment and, it seems, the time I do have is slightly wasted. I'll have to have another look at this Sunday night - I'm away for this weekend and just popped on to see what was happening.

 

There are two points of contact from the wheels; the hub/axle joint and the tube spacer that prevents the wheel touching the frame. I'm wondering if a solution can be found using the parts I've ordered? Perhaps paper or nylon insulators.

Share this post


Link to post
Share on other sites

I can see two avenues to explore for alternative solutions - others may be able to offer further alternatives.

  1. Split chassis - I don't think this would be a difficult conversion from your existing plans, it would need some insulation between chassis and body, and between the two halves of the chassis. The other disadvantage which you have already mentioned is the space occupied by the axle muffs (which would be better devoted to additional weight). The main advantage of split chassis design would be improved electrical pickup.
  2. Plastic spokes for the wheels, allowing metal rims and metal axles. Ideally plastic spokes only on one side, so that the axle is "live" to the "other" side, so you only need a pickup from one set of wheel rims. May be difficult to source the wheels - perhaps get some N gauge ones and get them turned down to 2mm standards, or it might be possible to convert some 2mm wagon wheels (though adding the holes for crankshaft pins would be a challenge).

David

Share this post


Link to post
Share on other sites

I've decided, as originally intended anyway, that this will be unpowered and a testbed for a later powered version (when I've worked out how electricity works...). I'm currently putting together an etch sheet so I can get going on it. When I'm designing it, it looks lovely and big on my screen but I have to keep reminding myself that some parts have dimensions in fractions of millimeters! Will put up my plan later tonight when I'm finished. It will be produced in 0.25mm brass sheet.

Share this post


Link to post
Share on other sites
Guest Natalie Graham

It's got a lot of wheels. An 0-30-0T? :)

  • Like 1

Share this post


Link to post
Share on other sites

Ha ha! Almost. I've had to make the wheels in layers - 4 layers per wheel plus spares. Does look confusing, and very difficult!

Share this post


Link to post
Share on other sites

Fast work! No tabs and slots? You might find them really helpful for aligning different parts.

Share this post


Link to post
Share on other sites

Thanks Rich. Prototyping in card was a good step, then I modelled the adjustments on the computer. I didn't opt for tabs and slots at this stage as I'm not entirely sure of my measurements so didn't want to restrict myself or make it harder if my measurements were out. The etch should be arriving tomorrow or Friday so we'll see how it goes!

 

This is a whole series of firsts for me, not helped by the fact I've never actually been close to a steam engine before (unless you count driving past one on Brighton sea front) so I've relied totally on my few books and this wonderful wide web.

 

Actually, I have a question: The rods that connect the wheels; are they in the same position on both sides or opposite positions, or are they offset by some other measurement? I'm guessing they would be opposite positions to take advantage of a smooth motion?

Share this post


Link to post
Share on other sites
Actually, I have a question: The rods that connect the wheels; are they in the same position on both sides or opposite positions, or are they offset by some other measurement? I'm guessing they would be opposite positions to take advantage of a smooth motion?

No - on a 2 cylinder loco the connecting rods should be set at 90 degrees i.e. a quarter of a circle to each other (referred to as 'quartered') such that as one rod is at its furthest forward or backwards position, the other is at the highest/lowest point of it's rotation. This is to prevent the possibility of the loco being stuck in the 'dead centre' position where neither cylinder is exerting any tractive force.

 

Paul

  • Like 1

Share this post


Link to post
Share on other sites

Regarding quartering, don't worry if it's slightly out. You can only see one side at a time and you don't have the 'top dead center' issue on a model.. The important thing is that the axles match each other, if they're both at (for instance) 100 degrees then that's fine, but obviously one at 89.5 and the other at 90 won't work.

Share this post


Link to post
Share on other sites

Thanks Katier. I have a very narrow margin of error on the connecting rods as I made the hole on the etch exactly the same size as the pin that holds it to the wheel, which will expand slightly (15% or so) with the etching process. The holes are also spaced at exactly the wheelbase of the frames. I hoping they will line up perfectly.

 

However, if I've made a mistake it'll be right here for all to see!

Share this post


Link to post
Share on other sites

Connecting rods often need a small amount of tweaking but the number one priority is to make sure the quartering matches per axle.

Share this post


Link to post
Share on other sites

Before the weekend my etchings arrived - only 24 hours after I approved them! Amazing service from PPD, can not fault them.

 

The price difference between getting two etchings and filling the sheet was very minimal so I opted to fill the sheet (thus providing some spares!) which has given me 6 etchings. The quality is very good and I can't wait to start building.

 

post-11337-0-34159100-1334061536_thumb.jpg

 

I've made provision for both 'John Owen' and No. 2, which were virtually identical, to be produced by any etch. I've also included smokebox door details and cab detail. The wheels are going to be very tricky to make as I have to put them together in layers which will introduce plenty of opportunity for error.

 

I'm still deciding whether to solder or glue the model together. I own an iron but I've not used it yet but it may be one too many firsts to introduce at the same time.

  • Like 2

Share this post


Link to post
Share on other sites

In my haste I forgot to add the gratuitous coin shots.

You need to include the coin shot so that all of us working in 4mm scale can go "Bl***y H*** that's small".

  • Like 2

Share this post


Link to post
Share on other sites

Curiosity got the better of me tonight. I've got way too much proper (and paid for...) work to do but I couldn't resist putting one of the wheels together from the spares on the etch. These are the component parts:

 

post-11337-0-53606300-1334085699_thumb.jpg

 

4 layers of wheel (0.25mm each of; the back flange layer, two middle fillers and the full/half etched front), the 1.5mm carbon fibre axle and the 0.3mm spindle that the connecting rods attach to. And here they are:

 

post-11337-0-10795100-1334085852_thumb.jpg

post-11337-0-55621800-1334085870_thumb.jpg

 

I haven't cleaned them up properly and they aren't fixed together but you'll hopefully be able to get an idea of what it will look like once finished. I'm hoping that once stuck together they will 'spread' out to the required tyre width - they are a bit too narrow at the moment, at only 1mm wide. If not, I've got plenty of spare middle layers to fill them out.

 

Very happy that I finally got to use my tools I've been collecting. The reamer kit was invaluable opening up those tiny holes. I've also got some very fine files which I'll use to finish the tyre surface once they've been stuck together.

  • Like 3

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.