Version 4

Version 4 of the On3- Long Hood top. This is a Road Engine.Another revision. Version 3 had some problems .. the ‘wagon top’ .. the curved top .. simply don’t print that well on a FDM printer leaving very obvious layer steps.

I got to thinking about this and realized that there is really no reason that I have to stick with the curved top – a flat top would work as well and actually makes more sense to me for a narrow gauge engine hood.

I added a hole for the sand filler tube in addition to holes for the fans and exhaust.

Version 4 of the On3- Long Hood top. This is a Road Engine.The alignment recesses on either end are for the front nose and cab connector. The alignment tabs are for aligning and fitting the sides. The support groove is for an internal support/frame/bulkhead to strengthen the hood.

V4 Test Print

The V4 Test Print came out pretty well. The only area that I have any major stepping is on the curved corners .. which I expected.

This was printed with a .4mm nozzle and at .15mm layer height. I can reduce that layering a lot by using a .25mm nozzle and .1mm layer height .. but that would used once I was happy with everything .. for now this works well as a draft mode.

Printed pretty well .. but the tabs were weak and broke off too easily. In a way that doesn’t matter .. or shouldn’t since they are simply guide tabs and meant to be glued to the sides and at that time would be hid. Still .. no real reason to keep them relatively weak .. slightly beefing up won’t cost anything but a little plastic and time.

Test Print V4a

Made the changes pointed out above. I used adaptive layering in Cura – this changes the layer height depending on the amount of curve in a model.

I made the tabs etc. thicker and modified the cab coupling a bit to make the tab slot deeper.

I printed jigs off as shown. They hold the top and sides tightly and precisely together for cementing – with a slot over the area where the top will cement to the sides .. hopefully so I don’t get wicking of the cement onto the jigs.

It was at this point that looking at the print I realized I had some more changes to work on. I need to add some tabs to locate the hoods on the BB section .. and also need to do something similar to locate the ends of the hoods. That requires reworking the BB-section of the model .. sooo .. time to take a deep breath and think about everything.




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