Malaxa LDM 12 / H0 Scale – part 1

LDM_12_IMG02

Been busy for some time and working very hard, so I didn’t had the time to post the works I’ve done.

3D printing has it’s limits when it comes to interlocking parts and lots more for moving parts. The grouves a printer makes are great when you do interlocking parts because they add friction and hold them in place better than their CNC couterparts. But it’s not that simple! You have to compensate for the shrinkeage you get when the part is cooled! Usually I use 200um in between! Any less and the pieces will not interlock, any more it’s ok, but alot more will mean that they will come loose and fall apart. For moving parts I add some microns to this, maybe up to half a millimeter. In this case the more you add the better they move but if you’re building models keep it under one millimeter.

Here is my Malaxa LDM 12 at HO scale. After the LDH 1250 project, I found out that is better to develop in the scale you’ll be printing than doing everything big and scale it later. You get first hand the problems (dimensions and walls) that will be impossible to make and you can correct them right there. This was the path I chose for the LDM 12: I did everything at 1:87 scale.

I want it to be able to move so I left room for a small engine and put a lid on the undercarriage in order to have access to the wheels axes. As I already mentioned, I used 200um gap for any interlocking parts as well as 200um gap to the wheels axes – in my case I will be using wheels bought from a model shop, not printed ones, so I hope they will provide the clearance I need for them to move.

After the LDH, I realised the holes that a 3D printer makes are never round, so instead of putting all those holes in the chassis I decided I will simply mark them and drill them later. It’s a manual and boring job but it’s a printer limitation you have to account for.

Also I took the time to think how to print every piece! They may look positioned correctly but some where designed from the top-down and some the bottom to the top, mimiking thier printing position. I had some surprises and had to redo some of the work but it guaranties me that the printing process will be done right.

 

Add a DCC decoder into a Roco BR 290

20160325_140711BR 290 model with the number V90 051 and code Roco 43666. The locomotive was produced in two versions, with and without DSS (meaning it’s ready for DCC but comes without a decoder). Mine is the one without the plug so I’m stuck with it’s original board. Note that this locomotive does not have much space to add decoders, the only solution is to use the cabin!

Because ESU LokPilot did not fit in the cabin I used a Romanian decoder made by TOM. Equally reliable but more little! Testing decoder to see how it fits in the cabin:

20160325_123159 20160325_123211 20160325_123241

It fits nicely so here is the complete tutorial on how to install it. Read more

Smart Block Occupancy Detection – part 1

The locomotive runs on a simple oval track with only one switch (only the external oval is used for this test) using optical sensors and distributed logic. There is no centralized controller or app, every sensors has the capability of choosing its state and acts accordingly.

The sensors are connected to a RGB led that indicates their current state:

Green = Free
Magenta = Pending
Blue = Detection

The sensors are plug & play; they don’t need any configuration and the distributed algorithm can handle any track arrangement automatically.

LDH 1250 3D printed: issues, challenges and workarounds

12764394_1054681837903931_988484404193013583_oWhen I designed the LDH 1250 I used the correct plans but I did not respect any scale. I just draw on the plans. Everything was fine in 3D and the details where great, unfortunately before printing I had to scale down my model. This posed some issues I didn’t thing trough.

Some details were lost due to scaling; when scaling, meters becomes millimeters and millimeters becomes microns. Remember that any printer has a minimum resolution, usually somewhere between 0.2 and 0.4 microns. I my case, the details in the order of millimeters scaled down to less than 0.2. So they simply vanished from the model, even though they were showing in the Cura printing application. So be ready to lose them or just make them bigger than they really are.

Another problem I’ve encountered was that the walls were too thin. So I had to add supports to them or make them thicker.

Here is the link to the previous part: LDH 1250 in FreeCAD

Eaglemoss passenger cars review and modifications

DSC_0482The Eaglemoss’s “Trenuletul electric” (en: Electric train) magazine just came out here in Romania andĀ its first number comes with an extremely cheap 1:87 (HO) passenger car. The train is a Chinese toy and it has its pros and cons but price per quality is great.

It runs smooth on the straight tracks but the wheels do not respect the NMRA standard for the HO scale. They are a little too short so the car gets thrown on the switches or by the counter-tracks. Some extra load doesn’t do the trick, the wheels must be changed :(

The worse is that is misses the decals but this can be also a good thing: I’ve designed and printed some. Below are 3 cars: one original (at the bottom), a second class and a first class that I made decals for.

DSC_0495Here is how I did it: Read more

Bring order to Atmel Studio

AtmelStudio_DependUponAtmel Studio (6.2 in my case) can easily overflow the Solution Explorer with lots of file names and this makes it hard for me to keep track of every change or manage header files. Luckily Atmel Studio is based on Microsoft’s Visual Studio, and there is a simple workaround for grouping one or more files under a parent one.

I usually group the code files (.c or .cpp) under the header files (.h) so I can easily check the function definitions rather than look inside the code. The image above shows how the Atmel Studio arranges the files and how I arrange them after the simple hack.

To do this I simply edit the project file (.cppproj), here is how to do it:

Read more

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