Sunday, 21 October 2012

Peckett Part 1


I have decided to take a bit of a break from the layout. It was getting a bit frustrating and I wasnt doing as good a job with it as I could, that plus the fact I had to remind myself that its a hobby after all and it should be enjoyable!

Refreshed with this in my head I have turned once again to my favorite side of the hobby which is designing and building engines. The latest one on my workbench right now is a little 0-4-0 Peckett saddle tank engine...

After a very useful advice from someone with regards to Shapeways and the way to send files I resubmitted the body once again for printing and the finished body this time was much, much better with it needing only a little bit of cleaning up which I will move onto once the chassis is finished.

There is still work to do on the chassis but the photos show my progress to date. The chassis is built by soldering each etched Nickel Silver sideframe onto some 0.3mm thick PCB and then filing out the shape through the etched bit to keep the profile. Both sideframe sandwiches are then soldered onto some solid 1/4" square Brass bar with gaps added for the gearbox, and then filed to suit the sideframes. The gearbox is one of my 138:1 ratio designs I did a while ago. This makes into a very rigid and strong chassis for its size, it also adds valuable weight too.

The wheels are 6mm Driving wheels using 2mm Association turned wheel rims onto 3D printed centers. The rest of the bits come from an etch I designed.

Its comming together quite well, its runs really quiet and slowly which has made me very happy! Dont forget too that the engine is just 40mm long bufferbeam to bufferbeam...

Julia :)

Sunday, 30 September 2012

Gears - A Useful Tip


Recently I have been working on a couple of bogies for my diesel railcar. The chassis is based upon bits from a TOMIX chassis, unfortunately I have been having some problems getting them to run reliably after converting the wheels to 2mm finescale standards. Below are a couple of photos showing the conversion...

The conversion consisted of two pieces of 0.5mm thick PCB glued to the sides of the TOMIX bogie with picups and the cosmetic sideframes soldered to them. Sadly though the slots I filed for the wheels and intermediate gears had too much play in them which caused them to bind when rotated in one direction. I then made the decision to rework the whole geartrain...

How to Work Out What Gears Were Used...

I needed to figure out what gears were used in the bogie, firstly so when I made a new set of sideframes I could get the gear meshing distances correct. Secondly I could them order some replacement gears to fit some new axles. The information I had for the gears were the Outside Diameter and the Number of Teeth. From this I found out the following...

The wheel axle gears 1 and 5 where identical. The idler gears 2 and 4 were also identical. Therefore:

1 & 5 Outside Diameter = 3.9mm, Number of Teeth = 11
2 & 4 Outside Diamter = 4.2mm, Number of Teeth = 12
3 Outside Diameter = 5.1mm, Number of Teeth = 15

Firstly I needed to work out what the Diametrical Pitch (DP) of the gears were, this is basically the size of the teeth and could either be in MOD (metric) or DP (imperial). The equation I used based on the information I had was:

DP = (Number of Teeth N +2) / Outside Diameter OD


DP (11t gear) = (11 + 2) / 3.9 = 3.33
DP (12t gear) = (12 + 2) / 4.2 = 3.33
DP (15t gear) = (15 + 2) / 5.1 = 3.33

To convert this from Diametrical Pitch (DP) (imperial) to MOD (metric) I used another simple equation:

MOD = Diametrical Pitch DP / Number of Teeth N


MOD (11t gear) = 3.33 / 11 =  0.3 MOD
MOD (12t gear) = 3.33 / 12 = 0.28 MOD
MOD (15t gear) = 3.33 / 15 = 0.22 MOD

Taking the average of the three = 0.27 MOD

As metric MOD gears come in standard sizes of 0.2, 0.25, 0.3, and 0.4 MOD I decided 0.3 MOD gears would be the best match for these bogies.

Finally I needed to work out the Pitch Circle Diameter (PCD) of these gears so I could work out the meshing distances.

Before I jump into yet another equation the PCD of a gear as shown above is basically the meshing diameter of a gear. Technically if you put two gears together so the PCDs touch the gears should be perfectly meshed. Of course in real life its sensible to add a little extra to the dimension to allow for tolerances and such (I usually add 0.1 to 0.2mm). So...

Pitch Circle Diameter PCD = Number of Teeth N x MOD


PCD (11t gear) = 11 x 0.3 = 3.3mm
PCD (12t gear) = 12 x 0.3 = 3.6mm
PCD (15t gear) = 15 x 0.3 = 4.5mm

At last! I had all the measurements I needed to rework the bogies. I then placed an order with Mikroantriebe for enough gears for two bogies and them opened my copy of AutoCAD and come up with this...

I then used my compound table on my mill/drilling machine to accurately drill and machine some new sideframes out of 0.5mm thick PCB once again and now the bogie looks like this...

And yes, it works fine (so far!) I hope this will be useful to others, especially if you need to get hold of a replacement gear for something...

Julia :)

Friday, 10 August 2012

Sipping from the Shapeways Cup of Fail


In my previous post I had some photos of my newly created 3D model of a Peckett tank engine. For those who cannot remember it looked something like this...


I then duly uploaded it onto the Shapeways website and promptly placed an order for one. A short while later the body turned up through the post and I excitedly opened up the package, unfortunately what I came across was rather disapointing to say the least...

The finish of the model was very rough. You have to bear in mind that the photo was taken after I had a go at cleaning up the rough areas (3), scrubbing the body with a toothbrush and washing up liquid, and primered the whole thing in Grey primer so it would be easier to photograph it. The body was printed in Shapeways classic FUD and I was expecting a small amount of cleaning up of marks like area (1) but to my surprise the saddle tank of the engine (3) looked very similar to the boiler (5) but the worst parts by far were the footplate (4), running plate, and boiler details (2) with a finish similar to course sandpaper.

I sent an email to Shapeways complaining about the quality of the model and a complaint was raised. About a week later I hadnt heard anything so I send a quick email to ask what was happening and I got this reply..

I have received a feedback about your complaint in the mean time, but I am afraid we can't arrange a reprint for this model. Quality of these supported parts were bad because of the design.

Now I am a bit peeved with this reply. Mainly because I know Shapeways can do better than what I was supplied but I feel like their reply is a bit of a 'cop-out' blaiming my design for the poor quality of the model. I know that they recommend getting bits printed separately but surely that wouldnt affect the finish that much? or is that just an excuse to charge me more for getting bits printed separately? Plus if there was a design fault then why was it printed? Who knows!

Anyway, if that is the quality of 3D printing I should expect then I think its not the solution I have been looking for and I will wait a bit longer until the technology evolves a little! That or find an alternative company...

Not a happy bunny..


Wednesday, 18 July 2012

Virtual Model Stuff


Over the past week or two things have moved away from the modelling bench onto the computer once again. I have had a few half finished projects which have been annoying me so I have been making an effort to get them completed. There is still a bit of work to do but at least there has been some progress...

1. The 3D printed wheels.

I have had the first batch printed for me by Shapeways and things look promising. For those of you who dont know the idea was to produce 3D printed wheel centers which then press into existing Steel wheel rims produced by the 2mm Scale Association. So far I have tried a few different types including the Boxpok wheels above and also a set of 9mm wheels which I have fitted to a Graham Farish Pannier Tank engine. I have a few ideas to improve them including a couple of plans to help with wheel quatering so watch this space as they say...

2. Kerosene Castle.

I have managed to spend a little more time working on this but there is still quite alot to do. The basic shape is now completed with only details now to add.

3. Peckett.

Finger crossed this is now finished and is now sitting in my Shapeways account ready for printing. It was the first engine I drew for 3D printing and so I am keen to see how it turns out. The reason why the roof and boiler look like that is because the plan is to have them removable and so they are held onto the body with sprues. The boiler also has been designed to fit one of my 137:1 gearboxes in a chassis which is etched.

4. Etch stuff.

A plan is also underway to get some more bits etched soon. As with the last lot of etches there is a collection of bits and pieces from all sorts of projects including a revised chassis for the Peckett (above), City of Truro bits, as well as some swanky bits for a fellow 2mm modeller (below)...

'Stay tuned' for more about these in time...

Julia :)

Saturday, 23 June 2012

3D Printed Wheels. A First Attempt


Today has been an interesting one. After a 'pep talk' from a fellow member of the 2mmSA Oxford Group with regards to my 3D printed wheel centers I then realised that I had enough bits to make a set of replacement wheels for a Graham Farish Pannier Tank. Below is what I managed to achieve in about 5 hours today...

Here are the ingredients for the conversion.
  1. A Graham Farish Pannier Tank Engine
  2. Some 1.5mm steel rod
  3. A couple of etched coupling rods from the 2mmSA (3-205)
  4. 6 x 3D printed spoked wheel centers.
  5. 6 x 9mm Steel wheel rims (courtesy of the 2mmSA)
  6. 6 x 2mmSA Crankpins (I used 3-106 but 3-107 would be better (I didnt have any!))
Step 1 was to press the wheel centers onto the rims. This was done simply by using (a very rusty!) machine vice and the centers were pressed into the rims until the back of the wheel was flush.

Step 2 was to cut 3 lengths of the steel rod for the wheel axles. I cut them with at least 10mm extra than I needed (for holding). I then used my rotary tool to clean up the ends and add a small chamfer to ease pressing on the wheels.

Step 3 was to press the axle onto the wheel. I used my drill press to make sure everything stayed square. I pushed the axle about 5mm through the wheel. I ended up with this...

Step 4 was to press the second wheels onto the axle. I did this by first holding the 5mm length of axle in the check and then pressing the second wheel on until it was on the axle. I then used a small length of tube which was a sliding fit over the axle and using a back-to-back gauge, pressed the wheels together until the gauge was a good fit between the wheels.

Im going to mention the gear now too. I 'salvaged' it from the original wheels as I didnt have an alternative but then found out that it had a bore of 1.6mm! Im not going into too much detail about how I got it to fit the axle (it was a bit of a cobble!) but it was pressed onto the axle of one wheelset before the second wheel was fitted in much the same way.

I then ended up with wheels like in the photo above. The pair nearest the ruler shows the next steps 5 where I cut the axle flush with the wheel (well cut it not quite flush then filed it down), then step 6 where I fitted the crankpins but pushing them through from the back with a bit of superglue to hold them in place.

Step 7 was them to paint them buy first giving the wheels a good clean in some IPA and then once dried I painted them with some Humbrol matt black.

Fitted into the chassis they look like this...

And below is how far I have got today. I still have a bit of work to do soldering the coupling rods in place but you get a good idea of the finished thing...

Julia :)

Monday, 18 June 2012

The Point Rodding Saga Continues...


One of the 'smart' ideas I had for Highclere was to add point rodding to the layout. Its something that you dont see that often on layouts, especially in 2mm Scale. Little did I know how much of a pain it would turn out to be!

Now for a little background info for those who dont know what I am on about...

The point rodding for the layout is based around two parts. The first is some 0.4mm square Nickel-Silver wire which I buy from Model Signal Engineering, it comes in a pack of 10 x 12" lengths. The second part are the 'stools' which I persuaded Ivan from Southwark Bridge Models to etch, reduced from his 4mm scale range. Trust me, it took some persuading as they are VERY small! Below is a picture on how they come.

Using a collection of jigs I then solder the stools at 12mm intervals along the length of the square wire. For each point I have used 2 lengths of wire, one for switching the point and the second for locking it in place. This is the time consuming bit as each stool is individually soldered in place, for each 12" length of 2 point rods there are roughly 75 point rodding stools. The stools are then soldered onto a small section of PCB and then glued to a similar section of plastic to represent the concrete plinths they are mounted on in real life. The picture below shows you roughly what I mean.

To me though, its worth the effort. Once its painted and on the layout it adds another little bit of detail that helps it come to life.

The thing is though I have been working on this now for what seems an eternity! I am now concentrating on the area of the layout where the majority of points are so there is quite a bit of rodding to do. Considering that currently its taking around 3-4 hours to complete a 12" length of rodding its keeping me busy!

I have tried about 5 different jigs now to assemble the rodding, the jig below I made out of cardboard which I made because as the point rodding gets closer to the signal box on the layout it gains more rodding as its passed more points.

At the moment Im working on 4 rods in parallel as the picture below shows.

The saying "practice makes perfect" is so true! I havent given up yet....

Julia :)

Saturday, 16 June 2012

Hello and Welcome...


For a while now I have wanted a home where I can post my modelling stuff. Why it has happened now I havent a clue but I am happy I have finally done it. Fingers crossed this will becomme the place where I post bits and pieces on my modelling which, right now is pretty much exclusively to 2mm:1foot. Right now things are fucused around my 2mm Finescale layout 'Highclere' based on the station just south of Newbury on the Didcot, Newbury, and Southampton Railway...

Thats just a random selection of photos, one thing Highclere is, is well documented! I am sure that these photos are not unfamiliar to many but in time, once things have settled down a little, there will be new and exciting things appearing here...

Julia :)