Lego Train Suspension

[Carefree_Dude]

Recently, I decided I wanted to do a complete overhaul on my Big Boy. One of the things I wanted to do was add suspension. 

I saw Jayhurst had done this with his big boy, using technic springs and a cv joint, as well as several technic bricks. 

I first tried mimicking this; I was successful in recreating it, but ran into many problems

-The bricks came apart when the suspension was used
-I ran the idea by the Technic forum, and they criticized the use of thin gears with XL motors
-CV joint was a point of weakness
-I had difficulty keeping everything together in general in the main model. 
-Only 4 studs connected the wheels to the train, causing it to disconnect while running occasionally. 
-was very difficult making everything work in a 4 stud space

Here you can see my initial attempt. 

 

So, taking the above problems to heart, I decide dI should do the whole thing using Technic parts.

For starters, I gave myself a 5 stud space instead of a 4 stud space, giving me a lot more room to work. 

Then rather than using technic bricks, I created a frame entirely out of technic beams. 

I also used thicker gears instead of the thinner ones. 

Thanks to the use of technic parts, I could lock everything in place so the only thing that will make it come apart is parts breaking. 

Lastly, rather than depending on a lego system turntable and stud clutch strength to hold parts together, I used a small technic turntable for attaching the wheels to the train. (Still designing wheelset, but it looks fairly straight forward.

Below is what I've come up with, with some parts removed so you see inside. The suspension gives it a full stud of travel! Sadly I cannot figure out a way to do this without the CV joint. The reason the CV joint is needed is because it has no grip on the axel, allowing it to freely go up and down. 

 

 

Let me know what you thin. I imagine this could be done on a smaller scale with smaller motors as well, I just really wanted a big boy with 4 XL motors in it. I've already built two of these gearboxes, and will use more technic parts to attach these together to make it even more solid. 

 

[bricks n bolts]

That's cool! So does this mean you can do tight bends at speed?

[zephyr1934]

Wow! That's amazing!

12 hours ago, Carefree_Dude said:

-I ran the idea by the Technic forum, and they criticized the use of thin gears with XL motors

That's hilarious but makes total sense

[Henry 991]

Very interesting, good job!

I also would have wanted to have suspension in my Big Boy and Challenger, but could figure it out. It would have limited both engines to two XL engines at max, and/or had limited structural rigidity. 

Have you would a way install the boiler panels yet? The Big Boys boiler diameter is 107 inches or 7.1 studs in 1:48.

 

 

[Carefree_Dude]

1 hour ago, Henry 991 said:

Very interesting, good job!

I also would have wanted to have suspension in my Big Boy and Challenger, but could figure it out. It would have limited both engines to two XL engines at max, and/or had limited structural rigidity. 

Have you would a way install the boiler panels yet? The Big Boys boiler diameter is 107 inches or 7.1 studs in 1:48.

 

 

 

Yeah, installing the boiler panels is easy. See the gap between the two springs? Bricks with holes go between those. From there you can have plates go along the body of the train. The front of the boiler has bricks with studs on side, as does the center area between the two gearbox/motor assemblies, and at the very back. Here are some preliminary photos, but keep in mind it is still a work in progress. The wheels look funny because they are the wrong size, and I have some BBB XL Drivers on their way.  Also, when the train is sitting on the wheels, the suspension compresses by about a plate. Right now, the bottom of the boiler is empty, and three of the four motors are fully exposed on the bottom. I still need to add the various tubing and pipes that go between the boiler and the wheels, as well as round out the bottom. I have some concern about how visible the blue and red pins will be, and I may need to swap those out for black ones. 

[Trekkie99]

Suspension??? Damn that's cool.

[Roadmonkeytj]

You could always (gasp) paint the pins with a black paint pen.

I'm liking the idea of suspension but wonder what is the actual advantage.  Regardless of it's advantage its cool.

[Carefree_Dude]

On 1/18/2020 at 4:27 PM, Roadmonkeytj said:

You could always (gasp) paint the pins with a black paint pen.

I'm liking the idea of suspension but wonder what is the actual advantage.  Regardless of it's advantage its cool.

 

The Big Boy is a very long train, with two sets of drive wheels. 

Say you are going to lego show like brick con. There is a train layout, and it is made of dozens of folding tables. The tables are uneven. This often causes minor slopes and inclines. Most trains don't care about this, as they are so minor that all driving wheels will remain on the track. This becomes an issue with long trains with multiple sets of driving wheels. A long train on uneven track may cause one set of driving wheels to lift off the track, causing that set of driving wheels to no longer be able to move the train. This can easily cut what the train is able to pull in half. 

With suspension, it allows the wheels to move up and down, allowing all driving wheels to be on the track in normal conditions so you will always have all the drive wheels pressed against the track. 

 

In a perfect system where the tables are 100% flat the suspension would be unneeded. 

[The Brick Boss]

Great Job @Carefree_Dude!!!!! I look forward to seeing how your Big Boy moc turns out. I'm sure it'll be awesome. 

[Roadmonkeytj]

4 hours ago, Carefree_Dude said:

In a perfect system where the tables are 100% flat the suspension would be unneeded.

I see we try to level our tables with shims and adjustable legs.  Anything over a plate difference will upset my long engines.  Guess I never thought about the suspension working to keep multiple drive wheels in place over rough track.

[Carefree_Dude]

1 hour ago, Roadmonkeytj said:

I see we try to level our tables with shims and adjustable legs.  Anything over a plate difference will upset my long engines.  Guess I never thought about the suspension working to keep multiple drive wheels in place over rough track.

Its very nice when places level their tables, but you can't always depend on it. The big tradeoff however is trying to fit the suspension, and the CV joint. I haven't put it under a full load yet, but I am very concerned the CV joint is going to break. 

[baard]

This is really cool and totally encompass what I love about this hobby. How do you make mechanics work in a constrained space with bulky parts.

I would like to see a video of your finished Big boy over bumpy tracks 

[Carefree_Dude]

Even with the Big Ben wheels, the locomotive sat a little high. I went back to the drawing board, and found a way to lower it while working in the same space for the gearboxes. Rather than using 4 springs, I reduced it down to only 2.  Then I had the springs "Cross" from one side of the other so they were kind of like a big "X" inside the gearbox. This allowed me to make the wheels roughly a stud and a plate closer to the boiler. 

I've been able to do some test runs and for the most part it works pretty well. The main issue I have is the rear drive wheel set has the wheels farthest from the gears popping upwards and derailing. I need to find a way to force those down. 

[Roadmonkeytj]

On 1/20/2020 at 6:51 PM, Carefree_Dude said:

Its very nice when places level their tables, but you can't always depend on it. The big tradeoff however is trying to fit the suspension, and the CV joint. I haven't put it under a full load yet, but I am very concerned the CV joint is going to break. 

Oh we bring our own leveling shims lol sometimes convention tables gave a twist lol.   

I found my issues is the pony trucks and the trailing trucks causing the center of the train (drivers) to lift off the track. 

To combat this I had to make them pivot not only left to right but up and down.  This means they are actually 1 plate away when level 

[jrathfon]

I remember an old part with a spring that was like the 2x2 tile with pin in the center. My BL search skills aren't amazing, but maybe invert that to push up against the bottom of your drive wheel "skid plates". Hopefully somebody else actually knows this part, I remember it being part of airplane landing gear.

[Carefree_Dude]

4 minutes ago, Roadmonkeytj said:

Oh we bring our own leveling shims lol sometimes convention tables gave a twist lol.   

I found my issues is the pony trucks and the trailing trucks causing the center of the train (drivers) to lift off the track. 

To combat this I had to make them pivot not only left to right but up and down.  This means they are actually 1 plate away when level 

Yup, my leading and trailing trucks go up and down as well. its crazy how much articulation you need to make happen. 

 

 

[zephyr1934]

9 hours ago, Roadmonkeytj said:

Oh we bring our own leveling shims lol sometimes convention tables gave a twist lol.   

 I found my issues is the pony trucks and the trailing trucks causing the center of the train (drivers) to lift off the track. 

To combat this I had to make them pivot not only left to right but up and down.  This means they are actually 1 plate away when level 

Unless you bring your own tables shims can only go so far. Warped tables are quite popular at venues. Of course my club is not so good either what with standing on the tables to assemble skyscrapers. I've had to resort to some serious suspension.

9 hours ago, jrathfon said:

I remember an old part with a spring that was like the 2x2 tile with pin in the center. My BL search skills aren't amazing, but maybe invert that to push up against the bottom of your drive wheel "skid plates". Hopefully somebody else actually knows this part, I remember it being part of airplane landing gear.

Oh, those things are great, I've used them for suspension on unpowered drivers.

 

 

On 1/20/2020 at 6:51 PM, Carefree_Dude said:

Its very nice when places level their tables, but you can't always depend on it. The big tradeoff however is trying to fit the suspension, and the CV joint. I haven't put it under a full load yet, but I am very concerned the CV joint is going to break. 

What about mounting the motors to the drivers and let the motors float inside the boiler? That way you could do away with the CV joint. Several people have done that for powered trucks.

[jrathfon]

Or maybe using this as a "skid plate" between truck and frame?

https://www.bricklink.com/v2/catalog/catalogitem.page?P=2484c01#T=C&C=5

Edited January 29, 2020 by jrathfon
include pic link

[Toastie]

On 1/27/2020 at 6:42 PM, Carefree_Dude said:

I need to find a way to force those down. 

I believe this is a very delicate problem.

It reminds me of the force required to push the center drivers in an out on Ben Beneke's BR 23. He used a split axle.

I don't believe a purist solution will do. But who knows.

A skid plate, as suggested by @jrathfon may do; you may need to adjust the force by using a leaf spring type piece. Very thin though.

Good luck!
Thorsten 

[viktor_kovacs]

I would like to add my 2 cents. Imho when it's too complex to transmit force through a moving link between the motors and the powered 'bogies', then many times it's easier to just make the whole wheel-motor assembly float in the shell. If the bogie could rotate around the motor assembly horizonally, then the motor assembly only have to pivot back and forth in the shell. In case of the Big Boy this would result in the two main driving wheel assemblies acting like bogies, while the front and back trailer trucks are beging pushed and pulled by the nearest powered bogie and normally not touching the shell. The shell would act like the baseplate of a locomotive. The actual vertical pivot point for these power bogies would be somewhere on top of the motor assembly. The shell could block the motors from rotating horizonally. The top pivots could be anything from a simple 2x2 tile to a 2x2 plate with a vertical pin (this could with a top technic plate actually stop the two motor-bogie asemblies from falling out when the shell is lifted). The benefit of this solution is that all traction components could be fixed together and only two rotational points would be needed for each assembly, one horizontal for the bogies (that are needed anyway even in a more rigid construction for the curves) and the two back and forth pivot points on top of the motors, preferably above the main downward axle. Then these bogie-motor assemblies could gimbal back and forth. I would like add that the horizonal drive from the motors down to the bogies could be as simple as an axle going through a 4x4 turntable, with the bottom fixed to the bogie and the top to the motor assembly (a fully sot assembly). The classic variant of this solution is having one vertical XL motor fixed to a bogie and the motor rotating together with the bogie. By using a tilting but non rotating motor assembly and a rotating bogie it's possible to have two horizontal motors driving one vertical axle. The only con i can think of is that on uneven terrain the shell will now tilt back and forth on the two motor assemblies, very much how a normal long passenger car or a two bogie locomotive would, but this will keep the full weight of it on the motor assemblies and on the driving wheels. The only thing that has to be avoided is the bottom of the shell touching the top of one of the trailer trucks as that would decrease the traction weight.

[Carefree_Dude]

Just an update,  this is how it currently looks. Still have a ways to go though. It runs well so far. Ultimately I'll be putting a buzzwizz in for power but I don't have one yet.