Project - Repair my Class 128 using 3D printed parts

[Railsnail]

So the issue here is to repair a Heljan OO Class 128 with two broken 'suspension bridge' components following the receipt of a used loco from an eBay seller which was dropped/mishandled in transit.

 

For those unfamiliar with those parts, they are two plastic parts, (one for each bogie), that attach the two bogies to the chassis casting. They allow the bogies to swing horizontally and vertically.

 

My options were to buy replacement parts from Gaugemaster or attempt to 3D print my own. So, I decided to do both meaning that if I failed in my component printing experiment, then I could use 'real' replacements.

 

As I had the broken parts and they could be sized with my trusty digital calipers, I proceeded to attempt to create a drawing of them in Sketchup. I must add that I am very new to the whole 3D printing side of things, so I wasn't sure how this would all play out.

 

After some time, forum searching and much trial and error I arrived at my model in Sketchup. Not as rounded and aesthetic as the original, but hopefully all the critical parts were correct and it would do the job. 

 

It looked right, but could I print it and would it work?

 

I downloaded the STL file (from Sketchup) imported it into Cura, and all looked good. I decided to print with 100% infill using the 'Normal' profile on my recently acquired Neptune 2 printer.

For those interested, I printed it with white eSun brand PLA. Extruder temperature 210 deg C, plate temp 50 deg C. I reduced the print speed to 25mm per sec and printed with 'tree' supports. Other parameters were defaults.

 

Cura calculated a print time of 10 minutes, so I wouldn't have to wait very long to see the finished article.

 

Sure enough, around 10 minutes later I had this...

 

Pictured just as printed, still attached to the printing plate. After detaching it and trimming the supports with a craft knife, it appeared to resemble the Heljan part, and checking with my calipers, all appeared to be okay with dimensions. But as they say, the proof is in the pudding.

 

I checked that the little pivot parts fitted nicely into the top bogie clip (see the pivot point inserted into the Heljan top bogie clip in the following picture).

 

 

 

 

 

 

 

 

They fitted without recourse to a lump hammer 🤨, but were a little tight. I was happy with this as I didn't want play in this pivot point, but then I didn't want excess resistance either.

So after a little whittling of excess support material with the craft knife, I was happy with clearances.

 

Similarly I checked the chassis pivot clearances and with a few more seconds whittling I was able to turn the component freely in the chassis without there being too much slop and play . 

 

 

 

 

 

 

This picture shows the component inserted into the two holes in the chassis sides in its horizontal position. If anyone has ever disassembled these, they will know that this is the orientation required to remove/replace it from the chassis.

 

The component is then rotated 90 degrees so that the top/bottom pivot points are in the correct position, the bogie halves are split slightly to allow the bottom pivot point to be inserted. The drive shaft is inserted into the drive coupler (which goes through the central hole) being careful with alignment so as not to damage the drive splines. 

 

 

 

 

Finally, the top clip was added... (located on the top pivot point), clips engaged and press down carefully but firmly.

 

 

 

 

 

 

 

 

 

The final result

 

Next check that the bogie is free to rotate and tilt freely without too much play. Repeat for the other end, and job was done ready to test on the track.

 

Track testing was a success, so I can declare my 3D printer repair project a success - and the Heljan spares will be spare when they eventually arrive.

 

 

Edited July 4, 2022 by Railsnail
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[5D_Stoke]

Many thanks, a clear and concise walk-through how 3D printing can replicate parts. What's your next challenge?

[Phil Bullock]

Great job. The Heljan bogie suspension system is just a little fiddly…

[Railsnail]

On 31/08/2021 at 15:43, 5D_Stoke said:

Many thanks, a clear and concise walk-through how 3D printing can replicate parts. What's your next challenge?

 

Thanks.

 

As I mentioned, I am very new to CAD/3D so this was more an exercise in replicating a smallish component, getting to grips with Sketchup and tinkering with 3D printer settings with the ultimate aim of repairing the broken suspension parts on my Class 128.  

 

I doubt I'll be making other replacement parts unless I have a specific requirement.

 

My other 3D printed object is a much larger enclosure for my DCC++ Ex Bluetooth Controller project. I may get around to documenting it some time as it has been tremendous fun, involving some electronics assembly/enclosure design and 3D printing. 

 

Here is the latest version of the 3D printed DCC++ enclosure. 

 

Edited July 4, 2022 by Railsnail
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[Railsnail]

3 hours ago, Phil Bullock said:

Great job. The Heljan bogie suspension system is just a little fiddly…

Indeed, very fiddly. There was much muttering as the final part of the re-assembly took place!

Edited August 31, 2021 by Railsnail

[JimFin]

For small engineering components like that, it would be worth getting a small sample roll of ePLA which has engineering strength similar to ABS once it has been annealed after printing.   https://www.filamentive.com/product-category/epla/

Edited September 5, 2021 by JimFin

[Railsnail]

On 05/09/2021 at 09:42, JimFin said:

For small engineering components like that, it would be worth getting a small sample roll of ePLA which has engineering strength similar to ABS once it has been annealed after printing.   https://www.filamentive.com/product-category/epla/

I was unaware of ePLA. Thanks for the information.

 

It will be interesting to see how robust ordinary PLA works out in the longer term. The parts, once printed, appeared to be up to the job. Time will tell I guess, but I would certainly try ePLA if I have a future requirement.