With all my recent time being focused on my C-855 project, several of the smaller jobs have been overshadowed, but not forgotten. So in the next few posts I’m going to share with you some of some of the small 3D printed parts that I have been asked to do over the last few months.
To start with in this week’s post we have some replacement N Gauge bolster pins for Graham Farish coaches and bogied wagons. The bolster pin, sometimes refered to as a truck pin or bogie pin, holds the truck or bogie onto the chassis. The pin allows it to rotate and navigate corners. The pin has to be a tight fit into the chassis so it won’t fall out but still allow the truck or bogie to rotate freely. This is achieved through the hole in the chassis being exactly the same size as the pin. This creates a friction grip as the pin is pushed into the hole. The friction grip is a stronger force than normal gravity and vibration can provide to remove it.
As always, I start with a 3D computer model. This model is simple but it was important to get the measurements accurate so the peg won’t be too tight or too loose in the chassis hole.
Because these will be printed in Shapeways’ Black Strong & Flexible material and they charge by the part, I have arranged twenty pegs all connected to one sprue.
The printed parts came out as expected; I had already removed two before I remembered to take a photo.
Below are a pair of the injection molded pegs as supplied by Graham Farish.
And here is a photo of one of my 3D printed pegs next to an original.
The Black Strong & Flexible material does have a grainy finish but this is of little consequence as the pin is never seen once the rolling stock is on the track. The material is also fairly flexible, as the name suggests, and this helps with ensuring a good fit into the chassis hole.
As a test, the pegs on a standard Graham Farish Mk1 coach were swapped out for the new 3D printed ones, which fitted perfectly.
The injection molded original has the same finish as the truck; as you can see below.
The 3D printed peg, apart from the finish, is exactly the same. You can see from the shadow there is a slight gap between the bogie or truck and the head of the peg. It’s the gap that allows the bogie or truck to move. If you look closely you can see that the couplings have also been replaced with my 3D printed short Rapido replacements.
The pack of 20 replacement Graham Farish bolster pins are available here.
In next week’s post I will have a replacement 3D printed part to share with you for one of Rio Grande Southern’s more famous pieces of rolling stock.