SAR 600 Class Steam Locomotive - LDD WIP

[ummester]

I've decided on a steam Loco to include with my Australian themed LEGO train builds and have been working on a model in LDD. I probably wont complete this one in bricks for a while yet, as the diesel loco has swallowed up my immediate funding.

I saw this pic on a train forum and I really liked the look of it. I think the design was based on the USRA Light Pacific.

It's currently designed with the motor in the middle of the tender and those wheels static on the tender, with the 3 large wheels static on the loco. All other wheels turn on large plates - will this accommodate LEGO track turns?

[Srbandrews]

Very nice looking loco and nicely accurate.

I'm not sure what you mean about turning on large plates. Do you have a picture of just the chassis and articulation points? For the engine, I would suggest having a look at the emerald night instructions. I has the same wheel arrangement and, for all its faults, the articulation at least works as intended. As for the tender, not sure if that will work, you might be better off putting the motor at one end as a bogie and making another bogie of the other two axles. Really, you just need to experiment with this stuff in real bricks.

[lightningtiger]

AWESOME engine design.....leaves my poor old SAR 501 MOC behind......wouldn't have the .xlf file handy.....I might want to try and build it ?

Brick On LDD On 'ummester' !

[ummester]

I wanted to make the motor in the front bogie Srbandrews but I couldn't make the front low enough for accuracy with it there. The rear loco Bogie only has a single axle - here is a link to the plans plans http://sarplans.stea...ingstock_03.gif

By large plate I meant the large round ones with a 4x4 turntable. Here is a pic of the underside of the loco with the turning bogies removed and flipped over:

I have seen videos of people running the EN with the tender motorized - they just take all the gears out of the 3 larger wheels to reduce friction and it seems to roll fine.

I try to operate with a minimum amount of actual LEGO for neatness, space and budget and have generally become proficient enough at LDD that my designs have the required build integrity to function as planned - with trains I cant test turning circles in LDD. The length of the 600 Class desgn above is quite similar to the EN - it just has different turning mechanisms for the loco bogies.

LXF file attached in this post - hope it works.

SAR 600 Class Steam Locomotive.lxf

Edited March 1, 2015 by ummester

[ummester]

I looked at the 500 Class lightnigtiger - I wanted to try 508 Sir Lancelot Stirling, just for the name :D But I also wanted to limit myself to 3 large wheels.

Oh, here is the car I designed for it - the build techniques are based on the EN car but the color scheme is distinctly South and West Australian - they still run the cars in these colors on some of the old steamers.

Edited March 1, 2015 by ummester

[Srbandrews]

Ah, I see what you mean. I don't think those turntables are likely to work as they don't allow any lateral movement. As the loco goes around a corner, the wheels need not only to rotate but also displace sideways. The front bogie will ideally need two points of articulation to allow the bogie to move sideways AND rotate to the right angle for the track. The trailing axle will need to pivot from a point not directly above the axle, but somewhere further forward so that the wheels move sideways around the radius when they turn.

You'll have the same problem with the tender because, for the front and rear axles, simply turning isn't enough, they need to move laterally or they will lock against the rails. When I suggested the motor as a bogey at the front, I meant at the front of the tender; you wouldn't have evenly spaced wheels but you could get it to negotiate curves that way.

There are other solutions, but this chassis shot of a 2-6-2T of mine shows how pivoting the axles closer to the drivers allows them to better follow the shape of a curve:

http://flic.kr/p/rguZiN

Edited March 1, 2015 by Srbandrews

[ummester]

Ok, I checked out the EN LDD file - I see what you mean Srbandrews - the pivot needs to be closer to the central wheels for all the bogies, so that the wheels can form a tighter curve as a group. It's what gives the EN that really daft look when I see it going around corners in videos. I really don't like that look and was hoping to avoid it - the bogies on actual trains don't slide out to the side, do they? Perhaps the rear bogie on steam locos a little bit - but the front bogie?

Edited March 1, 2015 by ummester

[jtlan]

Ok, I checked out the EN LDD file - I see what you mean Srbandrews - the pivot needs to be closer to the central wheels for all the bogies, so that the wheels can form a tighter curve as a group. It's what gives the EN that really daft look when I see it going around corners in videos. I really don't like that look and was hoping to avoid it - the bogies on actual trains don't slide out to the side, do they? Perhaps the rear bogie on steam locos a little bit - but the front bogie?

Due to the tight curve of the Lego track there's not really much of a choice when it comes to large locomotives -- overhang is inevitable. You can reduce the amount of overhang at the ends by not fixing the boiler rigidly to the drivers (so that the drivers slide under the boiler), instead fixing the body to different pivot points on the frame. However, this is much harder, and you will have to experiment with real bricks to see what arrangements work.

Also, you'll probably want to switch to Big Ben Bricks XL drivers -- the current ones you're using look a bit small.

[LEGO Train 12 Volts]

Wow this is an amazing project!

I love your CAD work ...very impressive and accurate! :wub:

[ummester]

Due to the tight curve of the Lego track there's not really much of a choice when it comes to large locomotives -- overhang is inevitable. You can reduce the amount of overhang at the ends by not fixing the boiler rigidly to the drivers (so that the drivers slide under the boiler), instead fixing the body to different pivot points on the frame. However, this is much harder, and you will have to experiment with real bricks to see what arrangements work.

Also, you'll probably want to switch to Big Ben Bricks XL drivers -- the current ones you're using look a bit small.

I could increase the length of the tender by 2 studs and put 2 bogies (one motorized) on a small train base - this would deal with any turning issues for the tender.

I don't mind (or see any problems) putting the rear bogie of the loco on a different pivot. Changing the pivot on the front bogie means changing the size of the piston housing (I did originally design it smaller) but this is an issue I see with many LEGO steam locos - the piston housing is just not big enough.

I had a look at Big Ben's drivers - petty there aren't any 2 color ones. Some black drivers with silver rims would be really nice.

Also thinking about zephyr's custom steam rods.

Just a thought - what if the drivers are static but only 1 (the rear one) is flanged. If the rear bogie was on long pivot (like Srbandrews here https://www.flickr.com/photos/93540898@N06/16584322556/) linked to a flanged driver which controls the steam rod motion over 2 more blind drivers, the front bogie should then work on a standard pivot and the boiler hold a tigher line around curves. The tender will probably need more wiggle room though.

Edited March 1, 2015 by ummester

[ScotNick]

I could increase the length of the tender by 2 studs and put 2 bogies (one motorized) on a small train base - this would deal with any turning issues for the tender.

I don't mind (or see any problems) putting the rear bogie of the loco on a different pivot. Changing the pivot on the front bogie means changing the size of the piston housing (I did originally design it smaller) but this is an issue I see with many LEGO steam locos - the piston housing is just not big enough.

I had a look at Big Ben's drivers - petty there aren't any 2 color ones. Some black drivers with silver rims would be really nice.

Also thinking about zephyr's custom steam rods.

Just a thought - what if the drivers are static but only 1 (the rear one) is flanged. If the rear bogie was on long pivot (like Srbandrews here https://www.flickr.c...06/16584322556/) linked to a flanged driver which controls the steam rod motion over 2 more blind drivers, the front bogie should then work on a standard pivot and the boiler hold a tigher line around curves. The tender will probably need more wiggle room though.

I think the tender looks good, and regarding the power functions motor: you could keep in the middle (which I think looks better) if you do it like Andrew Harvey did it for his LNER Tornado:

And regarding 2 coloured wheels: as Big Ben produces blind drivers, why not put rims on those? We'd just need someone to produce metal rims to put over those blind drivers. That way power pick-ups for the 9V rails would be possible without the 9V motor

[jtlan]

Just a thought - what if the drivers are static but only 1 (the rear one) is flanged. If the rear bogie was on long pivot (like Srbandrews here https://www.flickr.c...06/16584322556/) linked to a flanged driver which controls the steam rod motion over 2 more blind drivers, the front bogie should then work on a standard pivot and the boiler hold a tigher line around curves. The tender will probably need more wiggle room though.

Not sure I'm understanding you correctly? Are you suggesting something like sekiyama's design here? If so, I doubt it will work with the last driver being the flanged one, as the pivot arm would be too long.

[ummester]

Not sure I'm understanding you correctly? Are you suggesting something like sekiyama's design here? If so, I doubt it will work with the last driver being the flanged one, as the pivot arm would be too long.

Similar - but not the middle driver being flanged - the one closest to the cab and the front 2 blind.

The only pivot would be from the single flanged driver to the rear bogie - the front bogie would just pivot by itself - almost as if the bogies worked like a long diesel loco - with 2 blind drivers in the middle just for show

I'd have to work out a pivot mechanism for the rear loco bogie, on a technic rod, similar to Srbandrews.

Edited March 2, 2015 by ummester

[jtlan]

The only pivot would be from the single flanged driver to the rear bogie - the front bogie would just pivot by itself - almost as if the bogies worked like a long diesel loco - with 2 blind drivers in the middle just for show

I'd have to work out a pivot mechanism for the rear loco bogie, on a technic rod, similar to Srbandrews.

As I mentioned, this might work, but I'd be concerned about the long distance from the turntable on the front truck to the flanged driver. You may have better luck if you move the turntable on the front truck more towards the rear of the locomotive.

Also, what's keeping the 1x5 half-beam (the "piston rod") from flopping down? It looks like there might be a few too many degrees of freedom in the entire connecting rod assembly.

[jamesed_1971]

A great looking Steam Locomotive, just beautiful, are you planning to build for real.

[cgarison]

Super nice LDD design. The only thing of note is that you may want to attach the front bogey in a manner more like that of the Lone Ranger Constitution train or the Emerald Night rather than attempting to use a turntable as a point of axis for the wheel set. I learned this lesson last year when I was building my 4-4-0 locomotive with a double pivot that did not survive running on a layout for an extended period of time very well so I converted it to front bogey that moved similar to Emerald Night and then upgraded the train to much larger 4-6-0 style locomotive. Also, I used flanged drivers on the first and last axles and put the blind drivers in the middle. I have to admit that I had issues when I tried to use the blind drivers on the first axles as it caused the train to derail in the turns.

I probably wont complete this one in bricks for a while yet, as the diesel loco has swallowed up my immediate funding.

Yea... You have that right. My current sci-fi themed project is slowly turning into a money pit, but that is the cost of building a great model.

[zephyr1934]

Hey, that looks like a great start. I do not like the sharp right angles of the tile on the rods though, could you get away with just technic half beams?

Meanwhile, you definitely want to start building up a working physical model of the mechanism. When I say building up the the physical mechanism, I mean just that- get the moving parts where you want them and any potential conflict point (e.g., the base of the cab and the base of the tender), don't worry about color, substitute parts if need be, and do not worry about any detailing, boiler, or anything else that is not directly related to the mechanicals at this stage. You want to be able to make (relatively) quick modifications to make sure it all works. Whenever I start a new steam engine design I have one idea in mind and I shake out the final version in this manner to catch all of the errors I made in the cad build.

I suspect there are several things that you will run into as you transition to real bricks. Looking at the image below, it looks like your wheels are not quartered (the wheels should be 90 degrees out of phase on one side of the locomotive with respect to the other side). I THINK that the last technic beam in your rod assembly (left most in the image) will flop around and not work right. Instead, remove that and use the pin in the currently middle segment to run between the bars representing the crosshead.

[vedosololego]

Very good work ummester, similar to the real one.