Lego Wagon

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SimonWood
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Lego Wagon

Post by SimonWood » Tue Dec 15, 2020 6:32 pm

I've been working on a 'lego wagon' for my sister's children. I bought them the Tesco 'Caterpillar' trainset last Christmas as a cheap way to try to get them into garden railways, with a couple of open coaches for Playmobile people made from The Works boxes to combine it with their existing toys. In which spirit, I thought I'd make them flatbed wagons this Christmas, with a Lego top, so they could build their own superstructure, and my 3D printer arrived a just the right time!

I think I can use the sole bars from Rik's Southwold van for the wagons to save me designing those (thanks Rik!)
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Initially I thought they might be too breakable for the youngsters, given the nice details, but they are suitably robust!

However I needed to create custom buffer beams - with couplings compatible with the Lego train... For this I started using TinkerCAD which has a remarkably intuitive interface for a 3D drawing package.
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Unfortunately due to the dratted virus I cannot go and check whether the rather sketchy notes I made about the Tesco couplings are accurate...but fortunately I will be able to reprint them if the kids tell me they're too high or too low.
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But of course the main feature is having a 'Lego' surface to the wagon, so I've been playing with Lego from Thingiverse, which has lead me into discovering parametric 3D designs...

Thingiverse has a 'Customiser' which allows you to specify exactly what brick you would like (I'll have a 4x1 or a 2x2 or whatever) and then generates it, based on SCAD files rather than STL files. Unfortunately, the customiser does not appear to work... It just put my requests in a queue where they remain unprocessed. Fortunately, it appears you can do the customising on your own computer - by downloading OpenSCAD, the programme for making the SCAD files, and using the customiser within that. Pretty soon I'd exported and printed some bricks, and figured out that a plate of 10 x 18 would be a good width (80mm) and a good match for the length of the solebars...
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Unfortunately my Lego bricks were something of a wash out. They didn't clip on to each other, and worse the plate was uneven with a poor finish. One of the pips even broke off...
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...and if that happens when I'm handling it, it won't stand up to the kids. By the look of it, the whole thing moved during printing (poor adhesion?) but it takes a while to print, and given the brick quality, I've lost some confidence. So I've hastily ordered some real Lego, if necessary I will incorporate it into the wagon. As I understand it, it is ABS and so should bond quite well with an ABS-printed frame...

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Re: Lego Wagon

Post by Trevor Thompson » Wed Dec 16, 2020 8:15 pm

Just some thoughts on your lego prints. What you are trying to achieve seems to me to be pretty advanced. No criticism intended - just trying to analyse why it hasn't worked.

The potential forces on lego bricks are probably pretty high.

So some things to try:

In the print dialog box of Flashprint there are lots of options. This is the print dialog box:
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I clicked the more options button.

Now the options include:
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Shells - this is about how many solid layers are on the top, bottom and the sides. Phillip has suggested that it can take 10 solid layers. I wonder if it needs to go even higher to make the pips solid - 20?

Now the infil option:
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You will see that I am using 40% as my standard infil rather than the default 25%. You might want to go higher - to increase strength.

Bear in mind that filament printed "things" are always weakest along the level layers where they are printed. One way of increasing the bond between the print layers is to wash the surface with acetone (if you are printing in ABS which I am convinced you are).

You hinted at the possibility of bed adhesion problems. I think if the movement is not in the first layer of the print then that is not the particular problem you are suffering. Assuming that the print jumped somewhere while printing the pips it isn't adhesion. Something has caused the printer to lose its zero settings. I have found that can happen if something hits the extruder - why that might happen - don't know. I have had it happen. One thing to look at is the way it prints. When you have generated the print file (.gx) you get this screen:

You can see what is going to print by moving the slider on the left up and down in the following view.
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moving that slider lets you see just what it thinks it is going to print. It can reveal surprises!
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Bed adhesion. I can be a problem with ABS. I have suffered it! You will know you have it when the corners of prints come off the bed. So in the case of this wagon frame printed up side down the top surface would be curved. The first thing to do if it happens is to clean the bed surface with alcohol (meths). If that isn't enough clean with Acetone - but careful we are getting into an area where getting the print free becomes an issue. If all else fails mix some ABS offcuts into a small bottle of Acetone shake it up until it has dissolved and clean the surface with this. Beware - you will have problems getting the print off the surface if you do this.

I don't know if you are using a raft - but I do find it gives the best results with large items like the bed of a wagon (lego or otherwise) even if it is wasteful. Using a raft is less wasteful than keep trying to print without one.

Hope some of this helps.

Trevor

PS for everyone else it seems a bit printer specific but it might still be of interest!

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Re: Lego Wagon

Post by SimonWood » Wed Dec 16, 2020 9:23 pm

Trevor Thompson wrote: Wed Dec 16, 2020 8:15 pm Just some thoughts on your lego prints. What you are trying to achieve seems to me to be pretty advanced. No criticism intended - just trying to analyse why it hasn't worked.
This was the conclusion I had reached! The beginner's problem - not realising what is easy and what is hard. When I did realise what I was doing was probably a bit ambitious I ordered the bits of lego from eBay, I wasn't giving up on the printer, just re-evaluating my chances of me being able to figure out how to print something workable in time. I will have a go with fiddling with the settings, and your directions above are going to be extremely helpful - my first concern will not be the strength, though, but getting the accuracy of the blocks to the point where they function as buildable Lego blocks.

I have always used a raft so far, by the way.

It's very reassuring you mention the curling issue. I had that quite badly, and had already got as far as cleaning the bed with IPA. This has made an improvement to the situation - but I do still get curling albeit only very close the semi-circle where you pull the bed out - near the gap in the heating plate... It's a bit dispiriting after the first few prints all went so smoothly. I hadn't thought of cleaning with acetone or an ABS slurry... those will be my next steps.

Oh, and the tip with the slider - brilliant! I will do that with every print from now on, should save some heartache...

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Re: Lego Wagon

Post by ge_rik » Wed Dec 16, 2020 10:51 pm

SimonWood wrote: Tue Dec 15, 2020 6:32 pm I think I can use the sole bars from Rik's Southwold van for the wagons to save me designing those (thanks Rik!)
I can give you access to the original TinkerCAD drawings if you want, Simon. Just drop me a PM.
You could then copy and paste my drawings into new designs of your own - and then change the dimensions, remove or add parts as you wish. You can also see how I went about the making all the bits (by ungrouping the various components).

I tend to over-engineer the parts I draw - firstly to make them more robust in the rough and tumble of the PLR, but also to make them easier to print. For example, rather than a thin bar floating above the solebar and W irons, you'll notice that the brake lever descends all the way down to the print bed. I reckon that will hardly be visible when it's on the track, but it makes it far less susceptible to damage.

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Re: Lego Wagon

Post by ge_rik » Wed Dec 16, 2020 10:56 pm

SimonWood wrote: Wed Dec 16, 2020 9:23 pm It's very reassuring you mention the curling issue. I had that quite badly, and had already got as far as cleaning the bed with IPA. This has made an improvement to the situation - but I do still get curling albeit only very close the semi-circle where you pull the bed out - near the gap in the heating plate...
I found using a brim solved that problem for me. In Cura, the default is a brim of 20 rows, but I've reduced that to 8 rows to save filament. I've no idea if that will work on your printer but it works on both of mine (most of the time)

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Re: Lego Wagon

Post by philipy » Thu Dec 17, 2020 6:22 am

Certainly I've found a brim better than a raft, ( quicker, cheaper and easier to separate) but these days I rarely use either. Most things seem to stick quite happily, and only occasionally do I get a corner lift which I suspect that is due to uneven heating of the bed coinciding with where the corner of the print is positioned. I agree that 20 rows seems excessive for the raft but mine works in mm width not rows and I normally go for 4 or 8mm. The number of rows will then depend on the layer size I guess.
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Re: Lego Wagon

Post by SimonWood » Thu Dec 17, 2020 9:02 am

ge_rik wrote: Wed Dec 16, 2020 10:51 pm I can give you access to the original TinkerCAD drawings if you want, Simon. Just drop me a PM.
You could then copy and paste my drawings into new designs of your own - and then change the dimensions, remove or add parts as you wish. You can also see how I went about the making all the bits (by ungrouping the various components).
Yes please - will do!
I tend to over-engineer the parts I draw - firstly to make them more robust in the rough and tumble of the PLR, but also to make them easier to print. For example, rather than a thin bar floating above the solebar and W irons, you'll notice that the brake lever descends all the way down to the print bed. I reckon that will hardly be visible when it's on the track, but it makes it far less susceptible to damage.
Yes, seeing the brake lever I thought it was something the kids would easily break off. In reality, with your design, I think it will be safe in their hands. (Well maybe not the 2 year old's!)
philipy wrote: Thu Dec 17, 2020 6:22 am Certainly I've found a brim better than a raft, ( quicker, cheaper and easier to separate) but these days I rarely use either. Most things seem to stick quite happily, and only occasionally do I get a corner lift which I suspect that is due to uneven heating of the bed coinciding with where the corner of the print is positioned.
Ok, all this brim stuff is new to me, and I can't see an obvious option for it in Flashprint - but I think that maybe because the raft is actually the levelling mechanism on the Adventurer 3 (there's no way to level the bed I think). But Trevor will know, I'm sure, if there's a brim option and I've missed it!

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Re: Lego Wagon

Post by Andrew » Thu Dec 17, 2020 11:49 am

Hello all,

I don't know much (or indeed anything, yet!) about 3D printing, but I know a bit about Lego, in my capacity as chief sticker-putter-onner and lost-piece-finder for the ten years or so that my son's Lego obsession lasted. It really is remarkable stuff - whatever their secret plastic formula is, it's so good that 40 year-old pieces still click together as well as they did when they were made. That's the main difference between real Lego and the cheap knock-off stuff, like the "Blox" they sell in Wilco and others - the geometry's identical, but it simply doesn't stick together nearly as well.

For that reason, I reckon your "use real Lego" approach is probably the right one for this particular project - I think anything else might risk disappointment.

Incidentally, I don't know if you saw it on my (WH)WHR Rolling Stock thread, but last year I found that the right size roller bearings could be used with the "holey" Lego bricks to create very free-running axleboxes. For me it was a way to build vaguely accurate representations of the distinctive NWNGR axleboxes, but our test wagon showed the potential for Lego-based fun!

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Good luck with your project!

Andrew.

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Re: Lego Wagon

Post by SimonWood » Thu Dec 17, 2020 1:59 pm

Andrew wrote: Thu Dec 17, 2020 11:49 am Incidentally, I don't know if you saw it on my (WH)WHR Rolling Stock thread, but last year I found that the right size roller bearings could be used with the "holey" Lego bricks to create very free-running axleboxes. For me it was a way to build vaguely accurate representations of the distinctive NWNGR axleboxes, but our test wagon showed the potential for Lego-based fun!
I've seen the thread but somehow missed that post - wow, that is an awesome Lego wagon. The Lego axle boxes are brilliant, simple and effective way to make compatible running gear... Maybe the next stage will be to give them some kind of Lego wagon kit, including wheels and axles as well as Lego including the "holey" bricks, and see what they build from it!

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Re: Lego Wagon

Post by Trevor Thompson » Thu Dec 17, 2020 3:35 pm

Hi Simon

WRT brims and rafts. I think you are correct about the raft acting to level the bed. Certainly I have successfully printed with rafts brims and without anything. The key seems to be that if the print takes most of the bed area and has any height to it it’s more likely to work with a raft.
You can use a raft. Disable the raft in the print dialog box. Underneath on the right you will see the word brim and a box to click on. Click on it. You will print with a brim. I don’t think we can change the size of either the brim or raft.

Perhaps it would be interesting to see if we could create a usable Lego brick at some stage - but I think we all agree that Lego do it best. Amazing stuff! Our attic has a large hoard of it awaiting the appearance of grandchildren.

Trevor

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Re: Lego Wagon

Post by SimonWood » Thu Dec 17, 2020 4:02 pm

Thanks Trevor - I should have spotted the 'brim' check-box. I will give that a try...
Trevor Thompson wrote: Thu Dec 17, 2020 3:35 pm Perhaps it would be interesting to see if we could create a usable Lego brick at some stage - but I think we all agree that Lego do it best. Amazing stuff! Our attic has a large hoard of it awaiting the appearance of grandchildren.
It's funny, we adults stashed away the Lego until the nephews and nieces showed up. But every time it came out, we were still sitting on the floor building things with it long after the kids had grown bored and wandered on to the next thing...

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Re: Lego Wagon

Post by ge_rik » Thu Dec 17, 2020 4:33 pm

Quite a few years ago .... doesn't time fly ...... I worked on a primary teacher training programme and helped set up a new Technology course (when Technology was a brand spanking new National Curriculum subject). We bought loads of Lego Technik plus Lego computer interfaces to teach the student teachers how to make models and put them under computer control.

I was actually paid to play with Lego all day ......

A pity that Technology has now more or less disappeared from the curriculum and what is left is little more than basic craft work - if it is taught at all.

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Re: Lego Wagon

Post by Jimmyb » Thu Dec 17, 2020 4:39 pm

ge_rik wrote: Thu Dec 17, 2020 4:33 pm Quite a few years ago .... doesn't time fly ...... I worked on a primary teacher training programme and helped set up a new Technology course (when Technology was a brand spanking new National Curriculum subject). We bought loads of Lego Technik plus Lego computer interfaces to teach the student teachers how to make models and put them under computer control.

I was actually paid to play with Lego all day ......

A pity that Technology has now more or less disappeared from the curriculum and what is left is little more than basic craft work - if it is taught at all.

Rik
It would seem that "Craft Work" has gone through many changes, Woodwork, Metalwork and Technical Drawing when I was at skool, my sons did Craft Design & Technology (CDT), but it lacked any real "grounding", and I am at loss to think what my grandchildren are doing!!

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Re: Lego Wagon

Post by SimonWood » Mon Dec 21, 2020 10:43 am

Caught the last post!

Thanks everyone for the advice here - especially confirmation that incorporating a real Lego plate was the way to go...
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(Unfortunately the Duplo plate did not turn up in time, so the youngest gets his late... but since he's too young to have serious expectations of Christmas - last one was a third of a lifetime ago! - I expect he won't notice...)

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Re: Lego Wagon

Post by Trevor Thompson » Tue Dec 22, 2020 9:19 pm

Simon

They look very nice. I hope someone will be pleased!

Trevor

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Re: Lego Wagon

Post by ge_rik » Wed Dec 23, 2020 9:42 am

Looks good, Simon. It'll be interesting to see what appears on top of the build plates when their imaginations run wild.

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Re: Lego Wagon

Post by SimonWood » Wed Dec 23, 2020 11:05 am

Trevor Thompson wrote: Tue Dec 22, 2020 9:19 pm They look very nice. I hope someone will be pleased!
Thanks Trevor! Hope so! I've really no idea if the couplings will work well with the Tesco ones, my drawings were very sketchy, it would be frustrating if they cannot be hooked up as part of their train!
ge_rik wrote: Wed Dec 23, 2020 9:42 am Looks good, Simon. It'll be interesting to see what appears on top of the build plates when their imaginations run wild.
Thanks Rik! I don't think I could have done it in the time - even with a very basic solebar without the head start yours gave me! I look forward to seeing what they will build too, I only wish I could be with them to see it in person... hopefully before long I will.

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Re: Lego Wagon

Post by SimonWood » Sun Dec 27, 2020 6:26 pm

The Lego wagons arrived in time for Christmas and have formed the basis for some smart new coaches already...

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Whilst the wagons with their short wheelbase run well on the Tesco track, and couple to each other without issue, they don't play well with the Tesco train. The reason for this is that the Tesco wagons have a long wheelbase, and to compensate for this, although they are 4-wheelers, their axles are mounted in... can we call them bogies if they are a single axle? Or are they 'trucks' (like on a skateboard?) Anyway, the coupling is fixed to these bogies, designed so that the coupler pulls the wheels in on the curves... But coupled to my wagons, with the fixed couplings protruding from the buffer beam, the coupling is held out and the wheels are unable to follow the curve causing binding and if not derailment then loco wheel-slip.

So I need to design a new swivelling coupling...

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Re: Lego Wagon

Post by philipy » Sun Dec 27, 2020 6:35 pm

I'm sure a man of your perspicacity can sort a swivelling coupling without too much trouble!
In the meanwhile it looks as though the kids are following after their uncle, well done.
Philip

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Re: Lego Wagon

Post by Andrew » Sun Dec 27, 2020 7:26 pm

That looks like classic 80s Lego to me! Very nice, I'm glad they like it, hope you can get the couplings sorted - until you do, would the good old bent paperclip solve the problem?

All the best,

Andrew.

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