CNCing About.... Part 1

Hello :o)

A few years ago I went into a sort of partnership with a guy called Steve from the Oxford 2mm group. The deal was that he provided the milling machine in the form of a Proxxon MF70 and I would supply the CNC conversion kit. I purchased a conversion kit from a company called USOVO and the mill was duly converted by Steve. It was then passed onto me to finish off the conversion and get the thing working.

Roll on a couple of years and after not touching it I decided to get it out of the cupboard and try to get it working as it seemed too good to hide away unused. This is where another guy called Robert stepped in as I just couldnt get my head around the electrical connections and configuring the Mach3 control software. Robert took the mill and promptly got it working in about an hour and it was then back to me to finalise a few settings and tweak it until it was happy.

Anyway, its all up and working now and I am one happy bunny. Even better I found a plugin for Autodesk inventor which creates G Code based on my 3D models. It even does a nice little preview so I can check to see if everything works how it should.

Even with this preview, it still took a bit of 'tweaking' to get the machine cutting right though..

Eventually it all came together..

And now I have four chassis sideframes for my PECO 22xx collett engines on my 'to do' list..

Thank you goes to Steve and Robert in helping get the machine to this stage. The trouble is now what can I do with it next....




Julia :o)

All Change

Hello.

Well, its been a long time since I have posted on this blog but thats about to change...

For various reasons, all of which I am not going to go into publicly, I have decided not to continue posting details of my modelling on RMWeb but instead focus my posting on this blog instead. As I said, I am not going to go into details on my reasons for this but instead if anyone is mildly interested then request that you contact me directly where I will explain in more detail.

So, if you are interested (for some weird reason) in what I am doing, then please bookmark this blog and you will be able to keep track of what I have been upto.

Regards.

Julia :o)

January 2013

Hello.

Modelling has slowed down a bit recently but thankfully not stopped. The most notable thing recently was I finally managed to get another test etch done which has a few revised bits and bobs on it.

One of them was the remaining bits I needed for Highcleres yard crane based on a standard GWR 6 ton design. The majority of the bits were already drawn and were etched last year but I ran out of time to complete it so they had to wait until the next...

I am pleased with the way its turned out, the assembly went not too bad at all (for me thats quite surprising!). The next step is to paint the crane, I want to do this before I add the chain as I have some nice blackened chain which doesnt require painting. Also I need to build the hook and pulley once again, I have already done it once but cannot find it! Luckily there is a spare on the etch!

Secondly City of Truro was also included on this etch. The first time I found quite a few mistakes with it so I was looking forward to trying out my revised design...

This time I got a bit further but sadly there are still a few design issues to work out. This is my first ever engine kit after all so the next attempt should be a little better.

Julia :)

Peckett Part 1

Hello.

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 :)

Gears - A Useful Tip

Hello.

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

Therefore:

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

Therefore:

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

Therefore:

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 :)

Sipping from the Shapeways Cup of Fail

Hello.

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...

and...

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..

Julia.

Virtual Model Stuff

Hello.

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 :)