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Slowly getting there with the iClass - etches are almost done which I'll share a preview of before they head to the etchers. In the meantime I have been designing the inside motion. I was hoping Laurie Griffin might have something that would fit, but this loco is so tiny that I needed to start from scratch. Here are the slide bars - the rest of the components to follow. I'm hoping to learn how to animate all this in Fusion if time allows.

 

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I tried you way of printing the buffer heads. Worked first time. Far better results than using outsourcing companies that I could mention. I've also printed them in black so I don't need to paint them.

Marc

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Here's the rest of the crank motion - the benefits of 3D modelling this first is that I can check everything fits! And it seems to work so far. Valve gear next.

 

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Edited by jdb82
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Here are the first test prints for the inside motion for the Old Class i. For those of you familiar with resin 3D printing, you'll understand how critical getting settings and supports for the prints exactly correct for them to print correctly (or at all). I prefer to print in standard grey ABS-like resin first, as it tends to be the cheapest, meaning failure are less costly. The next phase in their development is to print it in a 'tough' resin (made by e-Sun). I've never used this before, so there will be a lot of experimenting with settings. I'll be interested to see how 'tough' it is, and whether it could be used as a final material for the model, or whether they will need to be cast (which is where I originally envisaged it going). Time will tell. 

 

Slide Bars

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Connecting Rods - the eagle eyed amongst you will notice that the big end needs to be in 2 parts to allow it to be fitted to the crankshaft......doh :banghead:

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Cranks

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Crosshead 

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Eccentric Sheaves

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Eccentric straps (2 printed fine, but the other 2 I tried printing in a different orientation, and didn't work). They are a bit bent - this resin isn't really strong enough to stand up to handing/sanding, as the rod is only about 1.5m thick.

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Expansion Links

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Balance weights

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One half of the motion mocked up for a picci

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54 minutes ago, Furness Wagon said:

Cheeky question I have a similar job to do what resin are you using?

Marc

 

The parts in the photos above are printed with Elegoo's standard ABS-like grey (https://www.amazon.co.uk/gp/product/B07FD84353/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1). This resin was used purely for me to play around to get the best orientation for printing, as well as to check they'll actually fit in the model,  rather than any kind of 'working' use - it just doesn't have the necessary strength or rigidity. I find I just haven't got enough experience of printing yet to automatically know what will work (best) and what won't, and I'd rather play with the cheaper(!) resin first so I don't waste the more expensive stuff.

 

Now I've gone through that step, I'll be trying out the e-Sun high-strength resin I mentioned (https://www.amazon.co.uk/gp/product/B082VRZ572/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1). This will probably have to wait until next weekend now though.

John

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Hi John,

The Elegoo ABS like resin has a hardness of 84D and the Esun a hardness of 75-81, according to pages on Amazon. So I am a bit confused. Isn't the Elegoo resin you have already printed with better than the Esun one??

Is there something else about the Esun resin that makes it better for this purpose?

Cheers Ian

 

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1 hour ago, ianmaccormac said:

Hi John,

The Elegoo ABS like resin has a hardness of 84D and the Esun a hardness of 75-81, according to pages on Amazon. So I am a bit confused. Isn't the Elegoo resin you have already printed with better than the Esun one??

Is there something else about the Esun resin that makes it better for this purpose?

Cheers Ian

 

 

Disclaimer first......I'm no scientist, so I may be completely wrong, but my understanding is that it should have a higher (tensile??) strength and therefore have a greater ability to withstand the external forces applied when in motion. I think the hardness refers more to a resistance to scratching, but I'm sure they are probably proportional to each other somehow. If it is the case that the Elegoo is stronger (as well as harder), then I shall certainly have to have them cast, as there is no way the eccentric rods are strong enough to withstand the forces using the Elegoo resin. I guess I'll find out at the weekend when I try printing them - I do like a good experiment! 

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Typically the harder something is the more brittle it is, e.g diamond very hard but hit it with a hammer and it will shatter into lots of very hard bits, when looking at mechanical properties you typically want to look at tensile or compressive strength first and then hardness, tensile strength if it is being stretched and compressive if it's being crushed, the hardness comes into play when you are looking at wear rates. Some materials can be machined and then surface treated to increase the hardness of particular areas. Hardness is often given for resin's because one does not tend to use them for moving parts that you want to last but is used a lot for very small detailed parts that may be handled a lot.

 

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That makes sense then - Elegoo's website gives the tensile strength of their ABS-like resin as 32-50mpa, and e-Sun's tough resin is 55-60. It may well be that the e-Sun resin still isn't strong enough to cope with constant motion, but I'll give it a test and see.

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  • 1 month later...

Progress has been a little slow recently.... not really anything to report on the inside motion, other than it doesn't look likely the tough resin will be up to the job of moving parts. It's strong enough for most parts, but the thin eccentric rods, which are only a millimetre or so thick, are still a bit too flexible. 

 

In the mean time, I have been teaching myself how to use Blender. This is another 3D modelling program, which I think a lot of gaming, jewellery and 'minis' creators use as it's really good for sculpting. I'm currently putting sprues together for the castings, which will be printed in a castable resin before being sent off to the casters. Fusion is brilliant for modelling the parts, but I find Blender much easier to arrange and place items on a sprue. Just one of the sprues below and I'll post some images of the others once they are done. Then I'll attempt to print them (just in grey standard resin first) to see if I can work out how to support them before moving onto the expensive castable resin. 

 

On another note, I can of course ask the casters, but if anyone knows where best to place the 'feeders' then let me know. Never having done it before, I've just gone with my best guess.

 

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  • 2 months later...

Jbd82 - this is great work.  I am in the middle of exactly the same project but in S Scale, using a mixed of etches (drawn in microsoft visio) and 3D prints using Fusion and Shapeways.

 

What drawing are you using?

Edited by Timber
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4 hours ago, Timber said:

Jbd82 - this is great work.  I am in the middle of exactly the same project but in S Scale, using a mixed of etches (drawn in microsoft visio) and 3D prints using Fusion and Shapeways.

 

What drawing are you using?

 

I'm working off a scale drawing that I've had for some time, but I'm not too sure of it's origin. It's not hugely detailed, but seems to have done the job. I've started building some of the etches and everything seems to fit quite nicely. I can send it your way if you'd like, just let me know. The Colonel Stephens Society also do scale drawings of Morus & Siddlesham which have been very useful.

 

The bits not covered by the drawing I have used a variety of photographs for, and then scaled dimensions from known measurements. Not a perfect way of producing a model, but I've not had any luck with Statfold Barn replying to emails/messages, as I believe they are in possession of the Manning Wardle GA drawings now. If you find any more, do let me know!

 

I'm going to print my detail parts in a castable resin, and then cast them in brass. I've refined some of the CAD work in Fusion, and reorganised all the sprews - they are now ready to be printed and sent to the casters. Pic below are just test prints in grey ABS - I haven't bothered cleaning them up after snipping the supports off. All this as soon as I get some time to do it! Work always gets in the way.......holidays soon though, then I'll have a blitz.

 

Would love to see some of your work :-)

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couple of my locos on the s scale section of RMWeb

 

 

I like the way you create your parts for casting....i will take a look at blender.  At the moment I print in brass via shapeways is quick and convenent.

 

I am finding the i class very hard....it is the hardest loco I have tried to build.  I have redrawn my etches and looking at the right ballance of 3D printed parts verses etched parts...short wheel base, small wheels, very little space for a motor.....argh

 

I model the Brecon and Merthyr and they had three of these engines so I am going to wrestle away with this to get it right....

 

I will pursue getting a better drawing through the CS society to see what they have.....using a drawing from the railway modeller I think.

 

Anyway - your fusion work is great.....going to keep an eye on progress.   You will put alot more detail into your model than I will into mine.

 

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These models are superb! I'll be happy if mine turn out anywhere near as nice as these. I'll be interested how my castings turn out. Hopefully I'll get time to print and send them off in a couple of weeks, and then I'll post them on here. 

Blender was easy to learn - I only used it for putting the sprews together though, and Fusion to create the parts themselves.

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  • 4 weeks later...

A couple of updates..... 

 

Having fiddled and fettled the 3D CAD work on Fusion for the Old Class i, I have got them to a point where I was happy with them. I then printed them in a castable resin. I used PowerResin Zero (mainly because it was on sale!) which has produced my best quality prints yet. Incredibly sharp and detailed, just by using the recommended settings - almost unheard of!

Just a few examples.... difficult to see the level of detail because it's black, but you get the idea. As the eagle-eyed will spot, I haven't sanded down the pips from the supports, and I did snap a couple of parts by not being careful enough.

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These have now been sent to the casters, so I should find out in a few days how well they will turn out. 

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I have also been playing with making my own wheels. I'm currently experimenting with a high tensile resin to see if it will be durable enough. I have printed a wheel centre to be a tight push fit into a steel tyre that I've had machined up by a helpful & local retired engineer. I then either file or drill a 'key' into the resin and the tyre, and fill with 2 ton epoxy. So far this method seems to keep the wheel concentric to the axel, but time will tell if the union between the wheel and the axel will be strong enough with the resin alone. 

 

My next hurdle was the crankpin - even when tapping slaters wheels for a 10BA screw, I've never had much success tapping them perfectly perpendicular to the face. So to perhaps the most over-engineered solution ever. I used the .stl from the wheel centre to create an inverted 'imprint' of the wheel into a lower 'base', and corresponding top half with a correctly sized hole to hold the tap vertical. The wheel is put in upside down in the base, and the lid put on top, preventing it from moving. This allows the hole to be tapped nice and straight. You'll all be laughing at me now as you'll use one of many ways to ensure your holes are straight, but this one seems to work for me!! The resin was a translucent water washable job, which needs using up as I don't really use it for anything.

 

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You can just about see the key at the bottom of the wheel here:

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And as per my previous post, the colour makes it hard to see the detail:

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And here are the castings literally fresh from the postie this morning. No cleaning up, and pips left on the prints from the supports still very much there. Generally very good quality and happy with them, although not without blemish - I'd set myself up thinking that they would come out as perfect as the prints, which was probably a bit unrealistic to say the least. The detail on the smaller parts is excellent, and all of the castings are better than some I've come across before - it’s the bigger parts where the most noticeable imperfections are. All being well, they will put the finishing touches to the model quite nicely. Now they are all here (apart from the one sprue I seem to have forgotten to print and therefore not cast  - it had the expansion links and the top ends of the connecting rod to fix them to the crank shaft), I can start work on construction the model itself. I have designed the frets which are back from the etchers, so I'm all good to go! I'll start a separate thread for this though 
Apologies for the number of photos that follow - but we all love photos! Also bear in mind they are VERY cruel close-ups!
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