[MOC] BMW 1250GS

[steph77]

 

First of all, my best wishes to everyone for this upcoming New Year! I wish you all the best and, especially, plenty of great MOCs.

Speaking of this...

BMW GS 1250

Ever since Lars Thygesen designed the 42063 set, I’ve had the idea of building my own version of it in the back of my mind.

I must say I was impressed by Lars Thygesen's design, particularly in three areas:

• The telelever suspension system
• The rear mono swingarm, which has the amazing advantage of not bending too much
• The simplified yet good-looking front panel design

Using this as inspiration, I decided to retain these three elements in my own design. Of course, since the chassis is 100% different, all mounting points and geometry have been redesigned to fit my build.

Okay, let’s move on to some pictures. We'll start with the naked chassis and follow the build to the final design.

(Sorry for the picture quality; I’m doing the best I can with my phone and the bad weather!)

As you can see, the basic structure closely resembles the real design: a lower boxer engine and gearbox with a low center of gravity.

The gearbox is the main feature of this build. It’s unique in many aspects, starting with a brand-new shifting and stepper mechanism.

I used to rely on @legotechnicmastery's design, but for this build, I wanted something original. This became a reality with the introduction of the new 45° knob gear, which is a key part of the concept.

The stepper mechanism is only spring-loaded—no rubber bands! Rubber bands are always the weak point in existing stepper designs as they’re not reliable over time.

In the picture below, you can see the principle of the stepper. The pulley wheels rotate and push a 5L axle that actuates the gray knob:

After being actuated, the pre-tensed 90° locking mechanism (as shown below) completes the movement and locks the system.

The pedal automatically returns to the neutral position, ready for the next shift. In the upper picture, you can also see the light bluish-gray indicator/limiter that prevents shifting from first gear directly to fourth.

The gearbox itself is based on a rotary catch and is much more compact than the new parts seen in 1:5 models from TLG.

It has four speeds and uses a unique configuration. Since the engine is a boxer type with two camshafts, I needed to add a complementary free wheel (16T), which is located on the transfer axle of the gearbox.

Looking from below, you’ll notice I used a special axle in the area of the swingarm fixation.

This wasn’t strictly necessary, but this solution provides 100% security, ensuring the axle never touches anything.

The overall transmission is surprisingly smooth, even in fourth gear.

Around this base, all other elements are integrated. Here they are:

As always, the next steps involved a bunch of tricky angles, improbable mounting points, and more.

This section includes the fuel tank and rear assembly—relatively easy—but fixing the front-end panels was more challenging.

I had to:

1. Secure the build by fixing a transversal beam throughout the structure
2. Find mounting points for the side panels

Here’s how it turned out:

Finally, we come to the final assembly, revealing this beast in all its glory:

You’ll notice that the mounting points for the original 42063 travel boxes are present, as well as a kickstand. The model is shown here on an external support, but this is obviously not mandatory—the bike stands perfectly fine on its kickstand.

So, So, So

That’s it for the first MOC of 2025! I hope you like it.

I’m particularly interested in hearing your thoughts and comments on this one.

Cheers,
S.

 

Edited January 2 by steph77

[NV Lego technic]

You mean Milan Reindl? If you do, it's not the admin, but @grohl.

Also, I like it's modular design!

 

[Anio]

And AFAIK, the Designer of 42063 is Lars Thygesen. :)

Nice work though. Very compact.

[steph77]

8 minutes ago, Anio said:

And AFAIK, the Designer of 42063 is Lars Thygesen. :)

Nice work though. Very compact.

Oups, i found this info on brickset....Ok i change this in the main post right now. Sorry @Milan

[JoKo]

 

I love this one! Great job with the gearbox and boxer engine. This allows the engine to be a real "boxer" with pistons moving in opposition.

I'd love to build it. Are you thinking about  making a studio model or a video to show the gearbox in action?

Also may I suggest a slight modification in order to ad a realistic detail? On every BMW boxer engine the cylinders are offset because of the boxer crankshaft. The left cylinder is ~50mm in front of the right one. Most people never notice it because it is rarely visible on pictures but when you happen to have one between your legs it is obvious.

You could add a 1/2 stud offset to your design like this:

 

Right cylinder: 

 

 

 

Left cylinder:

 

Together:

 

 

[jorgeopesi]

I like the color scheme and all the compact design, MOCs like that make me want to build bikes but I don´t how yet  .

[2GodBDGlory]

Very nice work! The split engine with the transmission in between is quite clever, and it's impressive how you got a 4-speed into a bike this small without major compromises! So you're using a round bar as a driveshaft? That's something I'd never thought of doing, but I can see it working well in tight situations without high torque loads

[steph77]

17 hours ago, JoKo said:

 

I love this one! Great job with the gearbox and boxer engine. This allows the engine to be a real "boxer" with pistons moving in opposition.

I'd love to build it. Are you thinking about  making a studio model or a video to show the gearbox in action?

Also may I suggest a slight modification in order to ad a realistic detail? On every BMW boxer engine the cylinders are offset because of the boxer crankshaft. The left cylinder is ~50mm in front of the right one. Most people never notice it because it is rarely visible on pictures but when you happen to have one between your legs it is obvious.

You could add a 1/2 stud offset to your design like this:

 

Ok, @JoKo;

I never noticed it before, but it seems logical and so i worked on your idea.

First, i designed the pistons units in this way in order to keep a good clearance vs the foot rest and  shift lever.

As this one is on the lefty side of the bike and considering the fact that on the real BMW the left side cylinder is the most forward of both, i decided to keep my original design for this one.

I so redesign, based on your idea, the right hand cylinder bloc. In order to keep a clee build, the whole bloc is now one stud longer, but the positioning of the cylinderhead has a one half stud ofset.

Here it is: Top view

 

Bottom view - Left cylindre - right cylindre:

Now, the ultimate solution would be to have one only shaft for the two cylindres, i had some ideas about it, but it first needs to be tested before saying more.

Thanks for your imput!

 

14 hours ago, 2GodBDGlory said:

Very nice work! The split engine with the transmission in between is quite clever, and it's impressive how you got a 4-speed into a bike this small without major compromises! So you're using a round bar as a driveshaft? That's something I'd never thought of doing, but I can see it working well in tight situations without high torque loads

Thanks for comment this build!,

You are spot on! This roud bar works just fine because this transmission is very smooth and the gearing is quiet kept low.

 

 

Edited January 3 by steph77

[Thirdwigg]

Very interesting design. I can't quite figure out how the changeover works, so I might have to start building it, and see if I can figure it out. Did you use shock absorber springs on the 5L axles with stops?

Also, is there a reason you used a green bar for the swingarm axle rather than an axle?

Great job again.

[steph77]

20 hours ago, Thirdwigg said:

Very interesting design. I can't quite figure out how the changeover works, so I might have to start building it, and see if I can figure it out. Did you use shock absorber springs on the 5L axles with stops?

Also, is there a reason you used a green bar for the swingarm axle rather than an axle?

Great job again.

The green bar has been used because it is a little tighter than regular axles. And it pass throughout the swing arm articulation in a inclined way .

For the shifter. Here you go. I only have one new know gear so this build is a variant for those who didn't have one. If you got one. Simple actuate the shifter directly with this one. The purpose of having two yellow know gears is only to get a 90 degree orientation as the idle point of the gear shifter is 45 degree.

 

Don't forget to add the springs. Directly on the 5l axle and only the soft ones.

 

S.

 

 

Edited January 4 by steph77

[JoKo]

On 1/3/2025 at 7:42 AM, steph77 said:

I so redesign, based on your idea

Nice! I think it's the icing on the cake. Makes your version so much better than the official 1200GS with this gearbox, acurate boxer engine and the other visual fix you made.

Thanks for the gearbox details!

[piterx]

lovely model dude!