[MOC] Flexible Articulated Mallet with Bellows-Type Connection

[Daedalus304]

"There's a prototype for everything"

I've heard that said several times in the LEGO train community since I started building, and the longer I go the more I see the truth in it.

Long boilers with crazy overhang is a problem we often run into pretty quickly in the LEGO world, but it was a problem for real-world engines as well. One solution, attemped by Baldwin in 1910, was to make the boiler of the locomotive itself flexible - using a flexible metal bellows in the middle.

Of course, they weren't so crazy as to actually put boiling hot water through these flexible bellows - the boiler itself ended just before this segment. Instead, all the hot gases used for the superheater, a water reheater, a water preheater, and more were stuffed in there. It's really an amazing idea, and I'd suggest you read up on it more here:

History of the Flexible Articulated Mallet

I've had this locomotive on my "To Build" list for a while, but never really did anything with it. I knew two things for certain, though - A) I was going to build it with a boiler that would flex in curves and only in the curves, and B) I'd never be so damn foolish as to try to get this monstrosity to go through R40, and would instead take advantage of the wide radius turns.

Enter OcTRAINber. This engine would easily be long enough to look silly through turns, and would be really fun to try to speed-build. I was set. And then, the rules came out. Must be over 70+ studs for a permanently coupled pair - it's 85 studs over the coupler, so - Check. Needs a video of a swoosh through R40 curves - Che... oh no.

The first two weeks of October were taken up trying to make this work. A reliable, flexible boiler mechanism that could make it through an R40 curve without derailing or experiencing too much friction, and a mechanism to keep the boiler bending ONLY in turns was an absolute must. 2 weeks and one incredibly lucky part discovery gave me a great solution for everything - except the bellows themselves. I tried just about every LEGO tire I could find that was the right size, but none of them could compress right and in the end I had to find a non-LEGO solution. A 3-studs long section of some Shop Vac hose became my Bellows, and I truly believe that this was the only possible solution. Either way, I was out of time.

It was also a great opportunity to try out a few new build ideas - the platform for the headlamp, a new way of building the bell, and some chassis-mounted roller bearings to help the extremely off-balance boiler pivot and turn smooth and easy. 

Whatever the outcome, this was great fun to build despite the stress. Having a full half of the contest time burnt up just trying to get the concept ironed out certainly provided some amount of worry, but in the end I've got a unique, interesting mechanism that is a whole lot of fun. I am definitely going to continue working on this engine. Just, maybe a little break first.

 

 

There are a few differences in my model from the "real thing", primarily the positioning of the bellows. The real engine had these just over the rear driver of the front engine, but because of the way the engine needed to be articulated and because of the precision needed with the boiler-flexing mechanism I had to move it back a few studs. I've slightly re-positioned a few of the other details to try to help balance this out aesthetically. 

 

This is the outside of the boiler in an R40 curve, where the pipes need to both hinge and telescope smoothly to let the boiler bend:

 

And here is the inside of the boiler in an R40 curve, showing how tight it needs to be able to pinch in:

 

Because the pivot points are so close together - the 2nd and 3rd drivers, the back half of the locomotive has a lot of hanging weight. This is supported by a couple roller bearings just in front of the firebox, above the last driver.

There are a lot more pictures in my Flickr Album, if you'd like to see more. Soon, hopefully, I will find a good way to show the mechanism inside the boiler that controls the flexing.

 

 

But, of course, pictures aren't quite the same as the real deal - the SWOOSH!!

 

 

[ALCO]

This is pretty cool! I was really impressed with the swoosh!

[deraven]

I did now know that such a thing existed, and you did a great job capturing it, both aesthetically and functionally.  Great job!  

[zephyr1934]

How do you come up with this stuff? That prototype is insane. The engineering to then get it all to work in lego is equally crazy. Great job on what one would think would be an impossible model.

[Asper]

Great MOC! And a very interesting prototype

[Steamdemon]

The bellows connection must have been tricky to put together. It's an awesome train.

[ColletArrow]

I never thought I would see such an unusual prototype in LEGO, well done. Clever engineering with the roller-bearings.

[Sven J]

!!!

I'd never thought it would be possible to model such a crazy thing.
What a tremendous piece of engineering and modelling art!
I'm very curious to see the bending mechanism inside.

[legoman666]

There are some race car thingies where you smash a bellow and the air pushes a car forward. Maybe some come in black?

[xboxtravis7992]

Wow. Bizarre prototype, and great job replicating the function in Lego. Can you imagine if this had actually worked in real life and more were made beyond the few the ATSF ordered? Maybe the UP Big Boys for all we know would have had a bellows in the middle . 

[Steamdemon]

On the topic of articulated locomotives, this would have been a nightmare to create in lego:

That's right. the Union Pacific Huge boy. A triplex, so to speak. I reckon that would need 12 blind wheels and 12 flanged wheels. and let's not get started on the tender, trailing and leading bogeys.

Thank goodness this did not get past planning in real life.

[Cale]

4 hours ago, Steamdemon said:

On the topic of articulated locomotives, this would have been a nightmare to create in lego:

That's right. the Union Pacific Huge boy. A triplex, so to speak. I reckon that would need 12 blind wheels and 12 flanged wheels. and let's not get started on the tender, trailing and leading bogeys.

Thank goodness this did not get past planning in real life.

That was never an actual planed locomotive by Union Pacific. Just some rail fan/foamer's fantasy.

Cale

[Daedalus304]

Thanks, guys! It certainly is a crazy prototype.
 

On 10/29/2017 at 8:12 AM, Tenderlok said:

!!!

I'd never thought it would be possible to model such a crazy thing.
What a tremendous piece of engineering and modelling art!
I'm very curious to see the bending mechanism inside.

Here's the basics of it:

The engine frames are actually built upside-down, and the boiler is attached to each engine by the 4x4 turntables over the 2nd and 3rd driver. If you disregard the red sections, basically what I have is two very close pivots under the boiler for the engine frames. These wheelsets can pivot freely as needed to negotiate turns, and this is not hindered or limited by the gearing (In practical application, that is. Off the rails there is indeed a point where the boiler will reach it's flexible limit and the wheelsets won't pivot any further - though that requires a lot tighter a turn than R40). The gearing is connected solidly to these engines, though, so when they rotate underneath the boiler it actuates their respective half of the flexing mechanism. Also, since the bend mechanism works in two halves like this - S-curves aren't a problem.

Getting this system smoothed out to take out all the backlash in the gears, keep everything lined up at all times, and most importantly making sure that the resistance in the Bellows mechanism didn't prohibit the drivers from getting the motion they needed to prevent derailing - that was the trick, and I'm really happy with how well this final product works. If I couldn't have gotten this mechanism right, I wouldn't have built the locomotive at all.

A lot of much more complicated systems were trialed and thrown out for various failures before I found a spare one of the Bionicle gear levers in a corner of my desk and upon closer inspection I realized that the teeth on the gear were lined up perfectly for a straight connection - which is a luxury not many other gears had. For a long time I had been working with "1 x 7 with Gear 9 Tooth Double Bevel Ends", but the teeth don't line up nicely at all with that and to get the angles straightened out took too many gears; which introduced too much backlash and so forth.

 

On 10/29/2017 at 8:33 AM, legoman666 said:

There are some race car thingies where you smash a bellow and the air pushes a car forward. Maybe some come in black?

I thought about those, and I think those would work even better than the hose segment I'm using - I just didn't have and couldn't find any in the right size. I'm definitely going to keep an eye out, though - this does work, but more efficiency is always great. :D

[Sven J]

Simple, but very clever!
Might be useful for other models, too - maybe for close-coupled cars, or a Kitson-Meyer locomotive. Thanks for the inspiration!

Strangely, building upside-down is an option that never comes to my mind...

[Man with a hat]

That's some magnificent piece of engineering. Very subtle and very intriguing. 

And apart form that it is an beautiful locomotive as well.