DHR B-Class project (Mainly 3d printed)

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Garethep
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DHR B-Class project (Mainly 3d printed)

Post by Garethep » Mon Oct 24, 2022 7:00 pm

Evening all,

Following encouragement in the "introductions" part of the forum (which may yet be regretted 😄) I have decided to document my 32mm DHR B-Class project.

I actually started this about 2 years ago after I acquired a 3d printer from my Brother in law who was running out of space for it. After downloading and printing random objects from the internet I decided to try and build a locomotive.

Initially I used the drawings from here https://modelengineeringwebsite.com/Dar ... ayan.html
These drawings are for a live steam "representation" of the loco but had the advantage of being fully dimensioned which made the exercise one of engineering 3d modelling rather than relying on any (non existent in my case) artistic interpretation skills. I even got as far as printing the main components of the loco as can be seen here.
Image

Unfortunately, both a slightly incorrect scaling value from the 45mm drawings to a 32mm loco (meaning the wheelsets rubbed in the frames) and drawing errors meaning the cab structure didn't fit meant a need to redo much of the work...I also became aware that the main dimensions of the loco when scaled down to 32mm gauge were far from scale but the single length frames were at the limits of my printers capacity meaning I would never have been truly happy with the result. Simultaneously, I had discovered the wonderful book by Peter Manning which include a large number of engineering drawings and 3d views.....after studying this, I realised that the separate front and rear frames of the prototype meant I could scale up to the correct size whilst still fitting the printer bed so decided to start again.

Image

Initially good progress was made and a new set of frames was printed....the above picture shows the difference in size to the rescaled 45mm loco... unfortunately, having behaved impeccably since I had acquired it, my printer then decided it didn't want to print anything for reasons seemingly only known to it and I gave up in disgust.

A year or so of significant work being needed in the house resulted in no time for.modelling but earlier this year the interest in railway modelling was rekindled when I acquired an oo9 layout and started building some resin printed loco body kits to run on it....this introduction to the magic of resin printing meant that soon I was hankering after a resin printer of my.own and before long, I was back in Fusion 360 drawing small scale locos....initially these were tram type locos using concealed chassis but I got frustrated with the lack of decent kits for a "proper" chassis.....eventually I managed to find a Backwoods Miniatures oo9 B class which, whilst really satisfying to build, was too much like watchmaking to be pleasurable. This and a long overdue leveling of our previously heavily sloped back garden got me back thinking about SM32 again. Unfortunately however it isn't as simple as just scaling up from 4mm scale.....the resin printer is truly magical but has a comparatively tiny build volume so, although much of the detailed parts can be produced this way, I still needed a way to build the frames and other large components.
With a new found determination, I spent hours tinkering with the filament printer and finally got it to at least partially behave but, whilst it would now print "square objects" to a reasonable standard, it still refused to print flat items like frames to the same standard it used to. Undeterred, and still having the frames I printed earlier, I carried on with the design of the other components and buying time to figure out how to sort the flat items later (I knew new frames were needed because of the pain of trying to quarter non removable wheelsets on the oo9 loco and I was determined to have removable wheelsets.)
Image

Having failed to find any suitable off the shelf wheels of the right diameter I decided to try printing some....my attempts at doing this in the filament printer where laughable even when the thing was working but, in resin, I was very pleased with the results...they may wear faster than steel but they will be removable and I can simply print some more info need to!.
Image

This picture shows where I have got to so far.....and give an idea of the scale of the thing (even though it's "only" an 0-4-0 it's not a small loco). Much work and rework has been done "virtually" in CAD trying to determine the best way of mounting the motor and gearbox and figuring out the best way to actually build the physical model....a real game changer has been a change to "ABS like" engineering resin....this stuff really is magic being far less brittle than the standard resin.....the highlight of my experimenting has been printing a test piece with threaded holes down to M2 which will accept a screw straight from the printer (in practice it's better to run a tap down first but it still blows my mind that this is possible!)

With this in mind I have spend a good deal of time designing the well tank in sections which can be printed in resin and joined together allowing river detail to be added at the drawing stage rather than having to painstakingly add hundreds of rivet heads by hand later!

I had almost gotten to the point of ordering a replacement filament printer to enable the frames to be properly printed when I spotted a new but second hand laser cutter for sale.....a quick check that this should cut 2mm perspex later and I now have a new toy to play with!
I haven't yet done anything useful with it but I have proved it's up to cutting the perspex (along with signing my name in Stanley Knife blades and other useless but amusing diversions 😄) but some suitable sheets of perspex are now on order so the excuses are starting to run out and I'll have to make some progress soon.

Im conscious that this has been a long and rambling first post....I hope some of you have stuck with me to the end and that it has been interesting.....more.updates when I have some.

Cheers

Gareth

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Re: DHR B-Class project (Mainly 3d printed)

Post by ge_rik » Mon Oct 24, 2022 7:18 pm

Sounds like you've had a bit of a roller coaster ride with your filament printer - and then there's the issues of the discrepancies between the 'scale' drawings!
10/10 for persistence :thumbright:

What exactly is the problem with your filament printer? Quite a few of us have run into problems at one time or another, so there's a fair bit of accumulated experience which you might be able to draw upon. Sounds like another thread in the 3D printing section might be worth a punt.

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Re: DHR B-Class project (Mainly 3d printed)

Post by philipy » Mon Oct 24, 2022 7:52 pm

I agree with what Rik has just said.
Also, what make/model is the filament printer, one of us may know it.
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Re: DHR B-Class project (Mainly 3d printed)

Post by Garethep » Mon Oct 24, 2022 7:57 pm

Thanks Rik,

The issue with the "Scale" drawings were that the loco was about the right size for 16mm scale but with 45mm gauge and, when scaled down became far too small. It was at best a "representation" which, if live steam, would have been entirely acceptable but would.have taken a lot of effort to get looking right.

I have chased down a number of faults with the printer including the bed starting to lift in one corner and the 2 z axis screws loosing sync.....having had issues with lack of adhesion, I am now having the opposite problem with prints pulling the coating of the glass bed off when removed....suspect a new bed probably needed but, for now, I will use the other tools at my disposal to go around the problem.

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Re: DHR B-Class project (Mainly 3d printed)

Post by Garethep » Mon Oct 24, 2022 7:58 pm

Hi Philip,

Its a jgaurora.....suspect it needs a new bed (or at least a new top layer)

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Re: DHR B-Class project (Mainly 3d printed)

Post by philipy » Mon Oct 24, 2022 8:29 pm

OK. Can't say I've ever heard of it, so I'm not much help I'm afraid.
Philip

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Re: DHR B-Class project (Mainly 3d printed)

Post by ge_rik » Tue Oct 25, 2022 1:05 pm

Garethep wrote: Mon Oct 24, 2022 7:57 pm Thanks Rik,

The issue with the "Scale" drawings were that the loco was about the right size for 16mm scale but with 45mm gauge and, when scaled down became far too small. It was at best a "representation" which, if live steam, would have been entirely acceptable but would.have taken a lot of effort to get looking right.

I have chased down a number of faults with the printer including the bed starting to lift in one corner and the 2 z axis screws loosing sync.....having had issues with lack of adhesion, I am now having the opposite problem with prints pulling the coating of the glass bed off when removed....suspect a new bed probably needed but, for now, I will use the other tools at my disposal to go around the problem.
Like most (if not all), I've had adhesion problems. When I started having issues with the coated glass bed on my Eryone, I turned it over so I got a plain glass surface and now use a quick coat of cheap hairspray. I also use hairspray for my cheapo printer. Since using hairspray, I've had very few adhesion problems (touch wood).

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Re: DHR B-Class project (Mainly 3d printed)

Post by Old Man Aaron » Tue Dec 06, 2022 2:15 pm

Can't wait to see more of this!
Regards,
Aaron - Scum Class Works

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Re: DHR B-Class project (Mainly 3d printed)

Post by -steves- » Tue Dec 06, 2022 6:35 pm

I only ever have over adhesion issues if I try to take the print off before it has cooled thoroughly. How long are you leaving it before removing the print after it's finished?
The buck stops here .......

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Re: DHR B-Class project (Mainly 3d printed)

Post by Garethep » Tue Dec 06, 2022 11:26 pm

That might be it Steve...I've been sidetracked with an oo9 model that has taken far longer than expected but this is next in the queue so hopefully some more progress soon

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Re: DHR B-Class project (Mainly 3d printed)

Post by Garethep » Tue Dec 06, 2022 11:26 pm

Old Man Aaron wrote: Tue Dec 06, 2022 2:15 pm Can't wait to see more of this!
Thanks Aaron...hopefully some updates soon

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