GeorgeCrecy

Need Help Replicating Historic Engine System

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Dear fellow LEGO enthusiasts,

I am in dire need of some help from you folks who are definitely more knowledgeable than I. In this case, I am needing help with the replication of the RMS Titanic's Reciprocating Engines and Turbine. I am in the midst at the moment of working on the project below, though I have not updated it in a great while due to university work. See this link here for the project thread. 

But this is a minifig scale project, with every door, every window accounted for. This means that in regards to the engines, I am also seeking to make them at least somewhat true to scale and able to work as intended. Obviously this is a big job of some top notch Edwardian-era engineering, but I am hoping that there might be some out there not as technically-challenged (pun totally intended) as I am, willing to help me get this part of the project off the ground. 

Some of the features I I am looking for include a fully air-powered system, where the air supply would come from tanks hidden in the mock-boilers, that are then funneled at somewhat high pressure to the Triple Recip. Engines, which means that the pressure would go down as it goes through each cylinder (HP, IP, then two LPs). The leftover air at a much lower pressure then goes to a junction that can either go to the Parson's Turbine at what was historically 4 psi, or can go directly to the condensers. With the latter I intend just to make the outside of it and hide inside some custom compressors like this. That would then return to the original air supply. With this I am hoping that I will have a self-supplying system with ideally no more than 5% leakage, or enough compressors that leaks are compensated for. WIth the Parson's Turbine, that can be an accurate shell with whatever is needed inside to include a working turbine, and probably with an gearbox and ascending set of gear ratios to give it the necessary torque.

These engines and turbine are meant to actually turn the propellers, perhaps even in water! Some other features would include a replica of the Brown-type reversing engine on the side of each of the Recip engines, making it so that the Stevenson-type eccentrics can change the direction of rotation. Considering the scale, the reversing engine doesn't technically have to be much more than a slightly-hidden piston that does the required job, but any more realism doesn't hurt. 

If something like this is possible, please let me know. I am really wanting to continue with this project, and this is a central part of it. But without the pieces in front of me instead of on a computer screen, what little I know of engineering definitely doesn't help without that tactile interaction. Thanks for your time, and I look forward to your replies! If it is possible, then I can follow up with the intended dimensions.

Here are some references for any that wants some:

View of turbine and condensers through wall from main engines      rotor shaft       model of port-side recip. engine      overall basic view        path of the steam of original, pressurized air for mine

Edited by GeorgeCrecy

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Building a functional pneumatic version of the engine would be impossible, as with a quick look at the scale of the engine, and some of the sizes for the pistons are rather difficult to make an external structure for. I could see a dummy version of this engine being operational with either an electric or external pneumatic engine driving it. potentially the engine could be pnuematcially controlled, though the only way I see that being possible is with some custom 3D printed parts for the cylinders, valves, and cylinder block. As lego parts aren't airtight. I could see about doing a rough layout of the engine in LDD, though I see it may be difficult to make the bores for the cylinders correct, as some parts may be too thick for scale, and will result in undersized parts as a sacrifice to the external structure. Given if you want to use 1/45th scale these would be the challenges, though If the engines were built in 1/35th scale, it would be somewhat easier to do, as the low pressure cylinders would be about 6 studs in diameter. Measurements below are in 1/50th scale, as for rounding the size of the low pressure cylinders.

800x585.jpg

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Hey there Tommy,

Thanks for getting back to me! I do hold out hope that this project is possible because of things like this by mechanicsnut on youtube, see here:

I do realize that the ubiquitous use of vacuum power would be a much different beast than pneumatic power, but I am hoping that the design can be very similar. On another note, I might question the scale you are thinking on, though I didn't give the dimensions necessary for some of your calculations, so that is my fault. So let me fix that.

Some of the dimensions we are working with are (including the base) about 22 studs wide, 72 studs long, and (give or take) 48 studs tall by my estimations using Ldraw's dimensions report, which measures height in the SNOT style. So with that in mind, the cylinders would be 10 studs wide in the largest cylinders, which is significantly more room than your original estimates. Secondly, to help with airtightness, I intend that while the outer shell is rounded, the inside should be squared off rather than be circular to aid in the ease of design. With all this in mind, I think we have some decent chances.

What do you think?

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21 minutes ago, GeorgeCrecy said:

Some of the dimensions we are working with are (including the base) about 22 studs wide, 72 studs long, and (give or take) 48 studs tall by my estimations using Ldraw's dimensions report, which measures height in the SNOT style. So with that in mind, the cylinders would be 10 studs wide in the largest cylinders, which is significantly more room than your original estimates. Secondly, to help with airtightness, I intend that while the outer shell is rounded, the inside should be squared off rather than be circular to aid in the ease of design. With all this in mind, I think we have some decent chances.

What do you think?

So based on the fact that the low pressure cylinders would be 10 studs in diameter, that means that you would be working at a scale of 1/25 correct? not minifigure scale(1/35-1/45). If so, then yes I see it being possible, though I would still prefer to use an electric motor to power it over vacuum, as this will run quieter, and you would have more chances to preserve the external structure of the engine, rather than compromise with the functionality for ducting air. Though I think it would be enough of a challenge just to get all of the valves and pistons to function correctly and maintain the external appearance, let alone making it robust enough to drive itself under load. 

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Hey Tommy,

Now what would be the fun of the project without a little challenge, eh? :wink:

As for the scaling, the ship as a whole is generally to the scale of the minifigs, and I would beware the danger of underestimating the sheer enormity of these beasties, they were each over three stories tall! But I would concede to dropping to something closer to 8 studs wide on the LPs, as the dimensions I gave are educated - but still rough - estimates. 

I did want to reiterate that this wouldn't be working off vacuum, was just using the video as an example of the mechanical possibilities. It would be using air power, which will be much quieter, and again you might be surprised at how powerful this setup can be if under load, though I don't have an exigent example to showcase. Ultimately, let us cross that bridge when we get to it. We can probably use an electric motor to help power the turning engine towards the rear that was the beginning impetus. We can also make use of some hidden gearboxes in the thrust blocks to help get more torque if need be.

Lastly, this was an awesome engine with a lot of thought put into the design, including the angles at which the pistons rested on the crankshaft and the including of an additional LP cylinder to reduce vibrations in combination with the Piston angling. On another note, I doubt there will be too much problem with ducting air as the usual tubing can be hidden in brick-made larger tubes that better match the scale, or perhaps use those large tubes introduced in the Mission to Mars line.

I'm liking the discussion, thanks for the help so far, let's keep it up!

 

Edited by GeorgeCrecy
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To continue the conversation perhaps with the danger of double posting, an idea to keep the air pressure in the cylinders comes from a comparatively simple possibility shown below:

8SO1F4K.png

The piston shaft (grey) with the technic reinforcement goes through the 4x4 round plate with a hollow center (yellow), that provides a rather seamless portal for the piston to go through without allowing air back down in the traveling. The 4x4 square plate allows other plates - or more likely tiles - to be placed inside the cylinder again without allowing gaps for air. I am sure this has been done before or is a very elementary a concept, so forgive me if this seems like preaching to a very knowledgeable choir. I am still on the learning end, especially applying engineering principles to LEGO. 

Secondly, I found an excellent cross-section of a steam engine that can be indispensable for our own designing of the cylinders to be seen here:

806px-TMW_677_-_Triple_expansion_compoun

Let me know what you think.

And one last thing to showcase, an attempt on the thrust block:

zGJklXp.png?1

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soooooo hard to make lego parts air-tight...

they are made with built in tolerances, so kids can build with them :)

 

Really great idea.. but I think you'd be best making it accurately looking+motion - both of which should be achievable with such a wide range of parts these days...

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I have been a bit busy with college over the past few days, though now that I have a break from college, I can think about this a little more. It turns out I used the wrong blueprint, and based off of the diameters of the cylinders (97",84",and 54") I think it would work if built in 1/34 scale, as the diameter in studs would be (9,8, and 5) studs. Is this scale correct, as I would like to know what scale you are building in? As I don't want to start this project in an incorrect scale.

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Hey there Tommy,

I am glad you have agreed to take this on with me! I greatly appreciate your help. I will be over with college classes next week, so I can certainly relate. But to answer you, we do want to avoid making the engines as a whole operating with an uneven width of bricks, as that will make everything else off. So if you orient your building with the LP cylinders being 10 bricks wide for the outside diameter, that would be ideal for everything else we would attempt to do. My guess would be that the other cylinder dimensions would be 8 for the IP and 6 for the IP. Also, the overall dimensions starting with the baseplate will be 22 in width, and give or take very close to 72 in length, and no more than 48 in height.

Edited by GeorgeCrecy

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Here's the current progress in designing the valve/cylinder bodies. For some of the parts I think all of the cylinders except the medium pressure cylinder will be round. Otherwise I will first tackle the exterior, and plan some of the internal structure along the process. The current scale for the model is 1/33, and it is 59 studs long.

800x417.jpg 

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Hey there Tommy,

Those are looking excellent! I might have some concern regarding their structural integrity under pressure, but moreso about the lack of holes for piping in the air, though I saw you mention this was a rough draft. I've been trying to fiddle with more brick instead of plate-built ones for both of those reasons. And taking a peek at the cross section image above I provided, it might be difficult to proceed if we don't do something more brick built. But you should continue with what you have in mind and we will see where it goes!

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I added the structure of the supports below the cylinders, it was somewhat of a challenge to get the geometry to work correctly, but this is a rough setup, and I would like to make them thinner, as they are too thick for the scale, but this is due to the technic structure below them, I may have to transition to stepped tiles as opposed to the slopes that are currently being used. the model is already over 1000 parts, I suspect the finished model will approach 2000-3000 parts.

800x417.jpg

Here's a revised version with thinner support structure. 

800x451.jpg

Edited by Tommy Styrvoky

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Hey there Tommy,

Looking very nice indeed! Will be interesting to see what you intend for the connection between the bottom and cylinders. Again, I am really appreciating your time on the project. 

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