[MOC] 1:5 Custom Harley-Davidson "Fat Boy"

[2GodBDGlory]

After seeing @JoKo's 1:5 Motorcycle engine and frame motorized topic, I realized that I've had my BMW M1000 RR parts sitting around for way too long, without ever really making any large-scale motorcycles with them, so I started thinking about what I could build!

I didn't really want to do a sport bike, because they looked all nasty and angly, such that they'd be challenging to model, so I looked for more of a classic American style. Looking for something that epitomizes that idea led me to the Harley-Davidson Fat Boy, which turned out to be a fortuitous choice, since my model was quite wide at 16 studs, and this motorcycle is known for its width!

Anyways, I decided that I'd rather focus on a cool look and a simple build process rather than modeling the original motorcycle super closely, so the end result is probably more of a custom bike, but I'm happy with the way it looks!

Functions:

1. Full suspension
2. Steering
3. Independent front and rear pneumatic disc brakes
4. Pneumatic clutch
5. Realistic 6-speed sequential transmission
6. Large-scale V-twin engine with moving valves, driven by a PF L-motor (Also a small pneumatic compressor attached to that motor)
7. Handlebar throttle control for that PF L-motor with a PF rechargeable battery box

Suspension:

Suspension was super simple in the front, just using the standard fork parts. The rear was also pretty simple, and just used two small, soft shocks under the rear seat. I felt that it all worked nicely!

Spoiler

Steering:

This is dead-simple on a motorcycle! Nothing really to note here, except that all the pneumatic tubes running up to it made it spring back to the center

Brakes:

I used one small pneumatic cylinder per wheel, which would rotate a 2x3 panel extender to pinch the disc between two rubber axle joiners. They weren't all that strong, but it was nice to build a brake system that actually pinched the rotor on both sides for once! The front brake was controlled by a pneumatic valve on the handlebars, while the rear was controlled by a foot pedal, just like a real motorcycle

Spoiler

 

Clutch:

The clutch was controlled by another pneumatic valve on the handlebars, and worked using a small pneumatic cylinder, assisted by rubber bands, to press a 28T gear on a pivoting beam against an old 30mm tire. The 28T gear then meshed with a 20T gear to send drive to the gearbox. Unfortunately, this system wasn't designed well enough to actually send drive to the rear wheel under most circumstances, as shown in the video. Friction-based Lego clutches are seriously hard to make!

Spoiler

6-Speed Transmission:

For this model, I really wanted to take advantage of new gearbox parts to make a realistic 6-speed transmission based on just two shafts, and I managed to succeed by putting two driving rings on one shaft, and the third one on the second shaft. The gear choices used were 8:24, 12:20, 14:20, 16:16, 20:12, and 24:8. You'll notice I'm using the "forbidden" 14T gear in here to sneak in a sixth speed that you couldn't get with only modern parts, and also that there's a very large 9X difference in speed between first and sixth! Still, I was happy to get a realistic gearbox construction with the right number of gears, and the new 2L driving rings allowed me to get the gearbox just skinny enough to work.

The more challenging part was shifting! The logic of the Yamaha shifters I was using is super complicated to figure out, but after a bunch of thinking I decided it was impossible to have it shift in order with the driving rings spread over shafts like I had. I then realized, though, that I could gear up the shifting mechanism to cause the shift rings to rotate three positions (135 degrees) for each press of the stepper, allowing me to shift from one side of a driving ring right to the other side of that ring, just like I needed. Because I was gearing up, though, it would shift through two other positions first, so it worked much better with at least a little rotation going on during shifts; and the shift positions were a little imprecise.

I used essentially the same stepper mechanism used in the Yamaha set, and it worked quite satisfactorily! It was set up in a relatively reasonable spot for foot operation, like a real bike.

Spoiler

Engine:

At 1:5 scale, I figured it would make sense to follow the example of @JoKo's bike and make a larger scale engine, with a diameter of three studs. I made it a V-twin design, as is typical for Harleys, and then started thinking about how to run some kind of valvetrain. At first I tried to make a pushrod valve setup like the original motorcycle, but I didn't think I could make it fit, or make it strong, so I ended up going to a much more basic SOHC chain-driven design. I used the new LBG 3L pins with springs over them as valves, which worked fairly nicely. It was fun to finally build something with a larger, more detailed engine! There was also a small pneumatic compressor geared to the engine, that would in principle allow for autonomous operation of the pneumatic functions. I'm too lazy to wait for something like that to pressurize, though, so I also included an old pneumatic distribution block part, which I used for its one-way valve, which allowed me to have a quick-disconnect port for an external manual pump. There was also a pneumatic air tank tucked in the front of the frame to allow for better operation of the functions, but because the white color would have stuck out horribly in the open frame, I threw some black electrical tape over it to make it blend in better.

Spoiler

Throttle:

I was quite happy to be able to include a realistic twist throttle on the handlebars! This pulled a long flex cable (made of 1.75mm 3D printer filament and cut to roughly the length of the longest such cable Lego ever manufactured), which pulled a linkage on my PF rechargeable battery box to change the speed of the PF L motor that was running the engine. It was quite a satisfying feature to include!

Spoiler

Overall, I thought this was quite an interesting model to build, and quite different from most of my previous models! It's always interesting to take on a new type of model, especially when it provides opportunity to include some interesting new features!

You can see more images at: https://bricksafe.com/pages/2GodBDGlory/harley-davidson-fat-boy

 

[allanp]

Impressive, I like all the functions you got in there. 

[JunkstyleGio]

It is an impessive model indeed.

Very nice functions. The list seems endless!

Keep up the good work!

An all black model is very cool, but looking at it is very hard. The use of some contrasting colours (like gold or silver) will let the model pop more!

Too bad, in both the picture and the movie, the lighting is kind of dark. Maybe an extra lighting point from the front will lift viewabillity up!

Please see this above mentioned points not as critisism, but as tips.

Again: very nice!

 

 

[2GodBDGlory]

1 hour ago, allanp said:

Impressive, I like all the functions you got in there. 

Thanks!

 

1 hour ago, JunkstyleGio said:

It is an impessive model indeed.

Very nice functions. The list seems endless!

Keep up the good work!

An all black model is very cool, but looking at it is very hard. The use of some contrasting colours (like gold or silver) will let the model pop more!

Too bad, in both the picture and the movie, the lighting is kind of dark. Maybe an extra lighting point from the front will lift viewabillity up!

Please see this above mentioned points not as critisism, but as tips.

Again: very nice!

Thank you!

You're right that the all-black look isn't the best for photos; I hadn't really thought about that in the build process.

That's true that it might be good to think a bit more about lighting too; I guess I usually put a pretty low effort into my photos, and it could be better

[weavil]

OMG, that's a lot of functions packed in there. Great work making it all work.

[Jurss]

I just want to add, that front fork angle looks too vertical for my taste. 

Otherway great functionality and look. 

Buy the way, try to switch on flash permanently, especially for black moc inside room.

[gyenesvi]

Very cool engineering, great functions in there! I didn't think such a huge gearbox could be fit into a motorcycle, together with a clutch system! And the brakes and throttle is a great idea as well, nice mix of pneumatics, electronics and flex system. Even though it's not a really solid thing, I'd really dig something like the engine and the gearbox/throttle/clutch as a standalone model for its educational value of how a complete drivetrain works. Could be a great showpiece model with optional motorization to see it working.

[JunkstyleGio]

14 hours ago, 2GodBDGlory said:

Thanks!

 

 

Here is a simple way to light up your models for movies and photography.

It takes a little tinkering to get the optimum lighting but you will get better result.

 

[2GodBDGlory]

8 hours ago, Jurss said:

I just want to add, that front fork angle looks too vertical for my taste. 

Otherway great functionality and look. 

Buy the way, try to switch on flash permanently, especially for black moc inside room.

Thanks! Using flash could be a pretty easy thing to try next time

4 hours ago, gyenesvi said:

Very cool engineering, great functions in there! I didn't think such a huge gearbox could be fit into a motorcycle, together with a clutch system! And the brakes and throttle is a great idea as well, nice mix of pneumatics, electronics and flex system. Even though it's not a really solid thing, I'd really dig something like the engine and the gearbox/throttle/clutch as a standalone model for its educational value of how a complete drivetrain works. Could be a great showpiece model with optional motorization to see it working.

Thank you! I was pretty happy to get the gearbox in there myself.

Yeah, a standalone drivetrain setup would be a cool display model! I've done similar stuff in the past in my Drivetrain Model series, but that's typically been models of much more complicated drivetrains, so that wouldn't be as good for education

Spoiler

 

 

 

2 hours ago, JunkstyleGio said:

Here is a simple way to light up your models for movies and photography.

It takes a little tinkering to get the optimum lighting but you will get better result.

 

Looks like a nice setup! Being a student at the moment and moving apartments regularly has made it challenging to build out a proper setup for photos, but I surely could do something more with different lights

Edited March 4 by 2GodBDGlory

[R0Sch]

As a motorcycle rider I find this MOC really impressive. You packed in everything important in terms of functions in such a tight space. Didn't think this could be done with LEGO. I really wish TLG would bring back the flex cable to Technic. Maybe now with new materials they wouldn't break so easily.

[1gor]

Fat boy is very cool model; perhaps you should use dishes to hide wheel spokes and make it like 30th aniversary model.

 

 

[2GodBDGlory]

2 hours ago, 1gor said:

Fat boy is very cool model; perhaps you should use dishes to hide wheel spokes and make it like 30th aniversary model.

That anniversary edition was a big inspiration of mine! That would have been interesting to try, but I was willing to let it just be a very custom bike

[1gor]

I see, somehow full wheels are very cool IMHO (not only on Harleys, but also on Chevy 210...), so I suggested that idea

[Lego Tom]

Very nice build! Does it have a radio you can hear three blocks away like the 1:1's do?