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Riveted Oil Tanks in 2mm Scale





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#1 D869

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Posted 07 July 2015 - 12:18

Not quite the right way up, but here's the first cut of a major bit for a project that I'm working on.

 

Fullscreen capture 07072015 130857.jpg

It's intended to be part of a 2mm scale model of a 10T class B tank as built by Hurst Nelson from circa 1907 at least until the 1920s.

The general idea is to do something similar to the Octel chlorine tanks (also from Hurst Nelson as it happens) that I built last year, namely an etched kit for the chassis and other ironwork and 3d printing for the tank and wooden packing.

Most of this project will be covering familiar territory, but there are two potential differences. Firstly and obviously the rivets - the Octel tanks were welded and didn't even have any visible seams whereas these tanks have very obvious rivets facing along all three axes. Secondly, this prototype is potentially of interest to more people so it would be nice to figure out how to make it available to others.

Rivets... my experience with FUD tells me that I will need to rub down the printed tanks in order to remove the stepping marks and evidence of the support wax. My current plan is to leave most of the rivets off the final print and then add them using Archer transfers after rubbing down.

Maybe Shapeways and FUD are not the only options?

  • There have been some nice results shown on here using stereolithography but as far as I can see that needs a subject with a flat base... which probably rules out tank wagons.
  • FXD has become available since my last order from Shapeways. This may help but as far as I can see only offers an improvement on one of the three axes

Basically... is there any way (today) to get an acceptable 3d print including the rivets?

 

FYI, the tank will be around 35mm long and a little over 11mm diameter.

Assuming that the hurdle of producing one acceptable tank with rivets can be overcome, I'm also pondering the question of resin casting clones from it. This is something that I've never done before. A couple of questions spring immediately to mind...

  • is it reasonable to think that I could DIY resin cast something like this?
  • alternatively, would a specialised caster be able to use a master made of (say) FUD which had Archer transfers plus some layers of paint or varnish?
  • what effect would the rivets have on the practicality of resin casting, either DIY or otherwise?

If resin casting proves too difficult or expensive then making the model available using 3d printed parts would be another option but this will most likely mean that every model built will need to have Archer rivets applied by the builder.

Your thoughts on the above questions would be appreciated.



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#2 richbrummitt

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Posted 07 July 2015 - 12:44

These are my thoughts:

 

it's entirely curved so will need likely need cleaning up because of layer effects. The higher the resolution of the printer the smaller the effect, but it will still be there. 

 

As you suggest cleaning up and keeping the rivet detail will be difficult. I had this predicament with the Mink F I was working on. There I had the benefit that most of the rivets were on strapping (raised areas) and I therefore had an edge to work up to and against when smoothing.

 

For one, or a few off, with the smoothest net finish I would consider an alternative approach - turn the body (or better still find bar of the correct diameter if available) to form the shape of tank(s) and then make a series of overlays for the curved panels. The rivets could be added either afterwards with transfers, or embossed into the overlays. The latter would work better in my opinion.

 

 

I'd like to do some resin casting myself but haven't plucked up the courage to spend the c.£35 to try it out/make a hash of it. Everything that I understand about resin casting tells me the rivets shouldn't be a problem. I'll be interested in other peoples responses on the related questions you posed.

 

I'm not sure my thoughts help significantly with the answers to any of your questions.



#3 D869

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Posted 07 July 2015 - 16:15

Thanks Rich - that's helpful. I think that your views on what's achievable with 3d printing are similar to mine.

I talked to Bob Jones a few weeks back to pick his brains about how he did the masters for the Association riveted Air Minstry tanks. He told me that he did an etched wrapper with the rivets on. If he told me what he wrapped it around then I've forgotten but the question of heat sinking springs immediately to mind if a metal inner is involved.

Doing this with an etched wrapper remains a possibility but that'll be another etch in a different thickness from the chassis so another complication to hold up proceedings. I thought that it was better to just get on and have a go with one possible option rather than do my usual thing of spending ages weighing up multiple possibilities.

I also lack a lathe, so turning anything would involve asking for favours (again!).

One further thought that I had since posting the original question... a mould would need to be in two halves so splitting the master down the middle might not be a terrible idea... which makes stereolitography a possibility. Would stereolithography be accurate enough to produce two separate halves that have good enough alignment where they meet?

Regards, Andy



#4 richbrummitt

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Posted 21 July 2015 - 13:05

Sorry, this thread slipped off my radar.

 

Would stereolithography be accurate enough to produce two separate halves that have good enough alignment where they meet?

 

I wouldn't expect to have any bigger issues than the usual when joining two semi-cylindrical parts together. If they are made at the same time they ought to be the same size. I'm sure that what shapeways call FUD is stereolithography of sorts



#5 D869

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Posted 21 July 2015 - 18:01

Sorry, this thread slipped off my radar.

 

 

I wouldn't expect to have any bigger issues than the usual when joining two semi-cylindrical parts together. If they are made at the same time they ought to be the same size. I'm sure that what shapeways call FUD is stereolithography of sorts

 

Hi Rich. No worries. This project is tied up (for the usual reasons of sharing photo tool and P&P costs) with several others so it is currently waiting for the others to catch up a bit.

 

Maybe I've got my terms wrong or the wrong end of the stick altogether but I'd been looking at another post on here regarding stereolithography. I think this is the type of printer that builds things on the surface of a pool of liquid and requires supports to be built on one side of the print. As such it's not an immediate choice for making a cylindrical object with no places to hide but splitting the thing in two might offer a way around that.

 

It seems (on the face of it) to be able to produce smoother surfaces (less visible stepping?) than Shapeways FUD but most providers only offer a relatively low resolution. This outfit in Telford seem to be able to do better but I doubt whether they see our hobby (and therefore us) as their core market.

 

At the moment FUD plus Archers rivets will probably be my first port of call.

 

Regards, Andy



#6 richbrummitt

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Posted 22 July 2015 - 12:50

Andy,

 

Granny knows how to suck an egg but a layered process is not the most obvious choice for anything that is cylindrical. 

 

From what I know (based on a phone call) Telford have only recently been set up with their additive machines, and so I presume that the parts in the linked thread were made at the US facility. The good thing about Protolabs is that their servers will almost certainly quote you. Expect to have a sales call on the back of the enquiry though! Shapeways business model seems more suited to a lower price that we might prefer. There are other suppliers that also do RTV moulding from 'printed' masters. Depending on how many you would like to make and how deep your pockets are this might be an option to explore. However the monetary cost is going to be higher than learning to do it yourself and you would not necessarily be in control of the mould replicated surface finish.



#7 richbrummitt

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Posted 22 July 2015 - 12:52

Update:

 

I've checked the UK site and they don't have the micro option listed.

In the high resolution for a beetle cattle box stl the first part was £99 and each subsequent part £19. Shapeways made them for a lower price, but that was a few years ago.



#8 D869

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Posted 22 July 2015 - 20:57

Thanks for the info Rich.

 

I think that the price for the second and subsequent prints would rule that option out as a way to produce multiple copies, so resin casting sounds like the way to go.

 

I guess that I'm keen to avoid the assumption that Shapeways FUD is the only option. That doesn't mean 'money no object' though but if there is a better option for producing riveted cylindrical objects then I'd be prepared to pay a bit extra, particularly if the cost can be spread over multiple resin castings using the 3d print as a master.

 

At the moment though I think there are rather too many 'ifs and buts' around both the 3d printing and the resin casting so I think that I'll stick with the lower financial outlay route (FUD and Archers rivets). If that doesn't produce a good enough result then it will be time for a re-think.

 

Regards, Andy









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