[TC27] Fire truck

[Jeroen Ottens]

Hi,

It has been a long time since I joined a contest, but this one I just couldn't pass up. For a long time I wanted to build a fire truck and this was just the perfect excuse to do that. It will be a ladder truck with a double cabin. Something like this:

Not much physical building yet, but here is a first sketch of the model with a rough indication of how all the functions are routed inside:

I went back a forth a couple of times between a fully manual, a pneumatic or an electric model. I finally chose the electric functions with manual drive and steering. It should get the following functions:
- steering with HoG, last axle steers with a small angle counter to the first axle. I try to get a significant steering angle on the front to get a really tight turning radius.
- drive with fake engine (I hope to find some space for the engine, that might be tricky)
Electric functions (each operated with their own switch that switches between turning left, no drive, turning right)
- outriggers
- rotation of the ladder
- elevation of the ladder
- extension of the ladder (I hope I can devise a not too bulky version of a two (or three) segment ladder)

Next step is to design a stiff frame that leaves enough space for all the functions.

[Paul B Technic]

Good idea, I can't wait to see your progress.

[Jurss]

Looks allready good!

This kind of body provides some good space for functions and/or electronics.

[Jeroen Ottens]

There is indeed a lot of space inside... Then again, those Control+ batteryboxes are always bigger than expected
Here is a picture of the current state:

I squeezed in an extra function (winch in the back). I am not too happy how crowded the area near the winch is, so I will probably redesign the outriggers so that they are more compact. That should create one stud extra per side, which should simplify the winch significantly

[Jeroen Ottens]

This weekend I took some time to build with real bricks. Here is the result so far:

Maneuverability is very important for firetrucks (I assume) so I wanted to have an a bigger steeringlock than usual on this model. It took some tinkering to get the ratio between the front and rear steered axle right with minimal gearing in between to prevent slack. It is pretty simple now. I think the rear is steered a tad too much, but within the limits of LEGO I think it is quite OK. Next step will be working out the cabin layout and the routing of the HoG for the steering. I don't think it is possible to get a working steeringwheel unfortunately. This bigger steering angle is eating away all the space in the front. Plus the inline 6 cilinder engine is sitting right in the front, so that blocks a lot of space as well.

Here is a close up of the area below the turntable:

This will probably be the densest part of the build. There are five functions routed through a cube of 5x5x5 studs. The axles in the front sticking out drive the following functions, starting from left under:
black axle is for lifting the ladder
brown axle is for the winch in the back
yellow axle is for the outriggers behind the turntable
brown axle sticking upward is for the slewing of the ladder
grey axle is for extending the ladder

It is a very satsisfying design experience I must admit. It is a nice change from building supercars .

Edited July 15 by Jeroen Ottens
added close up of area below the turntable

[dhc6twinotter]

This is really excellent!  I love how you’ve packed so many functions in a small space.  

[Timewhatistime]

4 hours ago, Jeroen Ottens said:

Here is a close up of the area below the turntable:

This will probably be the densest part of the build. There are five functions routed through a cube of 5x5x5 studs. The axles in the front sticking out drive the following functions, starting from left under:
black axle is for lifting the ladder
brown axle is for the winch in the back
yellow axle is for the outriggers behind the turntable
brown axle sticking upward is for the slewing of the ladder
grey axle is for extending the ladder

It is a very satsisfying design experience I must admit. It is a nice change from building supercars .

I really really like this kind of image, though the hints and insights are too sparse to understand how and where all the technic happens. Maybe we'll get more information in the future. Until then the density is simply a feast for a technician's eyes.

[Erik Leppen]

Now this looks very promising indeed. Love the tight steering radius. In fact I like how the rear axle steers a bit more than would be "correct" because then it's more "visible" and I think that's an important aspect of a Lego model - that you can see the functions working.

That "thing" with all the gearing below the turntable is precisely the type of things I like about Lego Technic :)

It's funny but I just recently built a similar fire truck in a larger scale (haven't posted it yet), and I think this somewhat-smaller scale is actually cooler, because the model doesn't become unwieldily large. Even with a densely packed function box like this, it is still all sort of "manageable". Love what I see so far.

Also, yes, trucks like these are super impressive and I think too few people build fire truck MOCs :)

That said, your bodywork sketch looks like a missed opportunity to use the new vibrant yellow ;)

 

[Paul B Technic]

That level of functions is awesome :)

[Jeroen Ottens]

Thanks all for the comments

On 7/15/2024 at 6:11 PM, Erik Leppen said:

Now this looks very promising indeed. Love the tight steering radius. In fact I like how the rear axle steers a bit more than would be "correct" because then it's more "visible" and I think that's an important aspect of a Lego model - that you can see the functions working.

I did a crude geometry check and it is actually not too overarticulated. In fact, the rear inner wheel shifted off the axle when running in circles for some time, which I think means it is even not steering enough...

On 7/15/2024 at 6:11 PM, Erik Leppen said:

That "thing" with all the gearing below the turntable is precisely the type of things I like about Lego Technic :)

 

On 7/15/2024 at 2:46 PM, dhc6twinotter said:

This is really excellent!  I love how you’ve packed so many functions in a small space.  

 

On 7/15/2024 at 3:37 PM, Timewhatistime said:

I really really like this kind of image, though the hints and insights are too sparse to understand how and where all the technic happens. Maybe we'll get more information in the future. Until then the density is simply a feast for a technician's eyes.

I personally also love this supertight, dense structures. Here you can see how it unfolds further down in the structure:

So far so good, but when I mounted the bodywork and tested the functions I didn't like the proportions. I know the model will be quite boxy, but it feels the whole model is too wide:

It is a 15 stud wide body, but I cheat a little with the white stripe at the bottom, that is actually 17 studs wide. So the wheels can be 12 studs apart. It actually means that there is quite some space between the central frame and the outer shell. Which feels like waste. So I think I will redesign it to a 13 wide body. That will have some challenges of course. Especially at the front wheels that will only leave 3 studs width for the central frame... What do you think?

Another point I found is that the outriggers fall to the ground quite easily when not 'in gear'. I didn't use a wormgear to have a self-locking mechanism. So that'll have to be redesigned (the worm gear will also help in slowing down that function to the same speed as the other functions.

And finally the dual direction switch setup (where each function has a switch that can select, forward, neutral and backward, feels a bit redundant as the knob on the batterybox is almost better accessible then the switch on the sides... So I am thinking of using the function selectors to select the functions and use the switch on the batterybox for switching forward and backward. On the other hand, the switch in the back for the winch would still be a forward, neutral, backward switch... So that would make it inconsistent. Any thoughts?

 

Edited July 19 by Jeroen Ottens
clarifying note

[brickless_kiwi]

Honestly I would leave the truck 15 studs wide. I certainly prefer to put a gearbox in gear then use the battery box to control forwards and backwards. 

[Timewhatistime]

Judging by the images, I wouuld recommend to stick to the 15 L wide body. It seems to me to have correct proportions given the enormous length of the vehicle. 

The remaining space could be used for easy cable routing, which is a rarity!

 

Once you have managed to put in the direction switches by gear boxes, you should stick to them as well imho.

It's impressive technical-wise... and for me it's an advantage in terms of playability AND technically to have the choice: One can switch directions either by battery box or (and) by gear box.

[Ngoc Nguyen]

This is what Technic sets should be about. Good old generic vehicle with bidirectional switches and battery box and cool functions. If you allow it I'd volunteer to do the instruction later.

[CK28]

Great idea and some lovely progress! Seeing this i might as well you know throw the towel in the ring regarding TC27 

I agree with the rest on the width, it might feel a little boxy as of now but well these kind of vehicles just are like that and by adding the more slim components like the ladder on top that effect will be reduced. 

[Paul B Technic]

On 7/20/2024 at 4:54 PM, Ngoc Nguyen said:

This is what Technic sets should be about. Good old generic vehicle with bidirectional switches and battery box and cool functions. If you allow it I'd volunteer to do the instruction later.

I 100% agree. I love how this is coming along.

[Erik Leppen]

On 7/19/2024 at 9:29 PM, Jeroen Ottens said:

I know the model will be quite boxy, but it feels the whole model is too wide:

It is a 15 stud wide body, [...] What do you think?

I wouldn't narrow the width for the whole thing, but maybe you can reduce the boxiness a little by having some elements mounted at angles and adding a bit of greebles and detailing here and there. Some suggestions:

• Maybe the dark gray ladders at the rear can be mounted at an angle. Maybe that part of the red bodywork doesn't need to be rectangular all the ay to the rear end of the truck (I don't kjnow how much of that rear end is filled by the internal gearing/structure. But maybe make that section a bit less wide and put the ladders at an inward angle, more like "stairs".
• Also, maybe you could have some kind of rack at the rear that has a bumper and the lights and allows firefighters to climb the truck more easily.
• The rear end corner of the white bumper looks like a #6 angle connector; maye use an elbow cylinder piece to make it just slightly more "rounded".
• Also maybe you should not do everything in red, but have a few details in, for example, light gray or dark gray.
• For example, I really like how the white 7x11 frames show at the top, but the rest of the top, especially at the rear half, is almost completely a red plate. Maybe have slightly more color variation there, and continue the "gray center, then a white 1 stud stripe, and the nred on the sides" theme that you also used at hte central "engine bay". make part of this plate gray or dark gray.
• Another one could be the handles on the 5x11 panels that cover the gearbox selectors. Maybe use a black or light-gray long axle as a handle instead of those two red ball-pins. That might "break" the big red surface a bit.

 

Edited July 22 by Erik Leppen

[pleegwat]

On 7/19/2024 at 9:29 PM, Jeroen Ottens said:

It actually means that there is quite some space between the central frame and the outer shell. Which feels like waste.

Storage room. Firemen need a lot of equipment. This includes firehoses and nozzles, but there are also axes, hydraulic cutters, and many other things I'm not thinking of right now. Every nook and cranny will be stuffed with storage cabinets.

A ladder car will also have a big water pump. I'm not sure if a water tank (in case no surface water or hydrant is available) would be on the same vehicle.

[Jeroen Ottens]

On 7/20/2024 at 7:06 AM, brickless_kiwi said:

Honestly I would leave the truck 15 studs wide. I certainly prefer to put a gearbox in gear then use the battery box to control forwards and backwards. 

 

On 7/20/2024 at 8:19 AM, Timewhatistime said:

Judging by the images, I wouuld recommend to stick to the 15 L wide body. It seems to me to have correct proportions given the enormous length of the vehicle. 

It's impressive technical-wise... and for me it's an advantage in terms of playability AND technically to have the choice: One can switch directions either by battery box or (and) by gear box.

 

On 7/20/2024 at 8:54 AM, Ngoc Nguyen said:

This is what Technic sets should be about. Good old generic vehicle with bidirectional switches and battery box and cool functions. If you allow it I'd volunteer to do the instruction later.

 

On 7/21/2024 at 12:50 PM, CK28 said:

Great idea and some lovely progress! Seeing this i might as well you know throw the towel in the ring regarding TC27 

I agree with the rest on the width, it might feel a little boxy as of now but well these kind of vehicles just are like that and by adding the more slim components like the ladder on top that effect will be reduced. 

 

On 7/22/2024 at 5:26 PM, Erik Leppen said:

I wouldn't narrow the width for the whole thing, but maybe you can reduce the boxiness a little by having some elements mounted at angles and adding a bit of greebles and detailing here and there. Some suggestions:

• Maybe the dark gray ladders at the rear can be mounted at an angle. Maybe that part of the red bodywork doesn't need to be rectangular all the ay to the rear end of the truck (I don't kjnow how much of that rear end is filled by the internal gearing/structure. But maybe make that section a bit less wide and put the ladders at an inward angle, more like "stairs".
• Also, maybe you could have some kind of rack at the rear that has a bumper and the lights and allows firefighters to climb the truck more easily.
• The rear end corner of the white bumper looks like a #6 angle connector; maye use an elbow cylinder piece to make it just slightly more "rounded".
• Also maybe you should not do everything in red, but have a few details in, for example, light gray or dark gray.
• For example, I really like how the white 7x11 frames show at the top, but the rest of the top, especially at the rear half, is almost completely a red plate. Maybe have slightly more color variation there, and continue the "gray center, then a white 1 stud stripe, and the nred on the sides" theme that you also used at hte central "engine bay". make part of this plate gray or dark gray.
• Another one could be the handles on the 5x11 panels that cover the gearbox selectors. Maybe use a black or light-gray long axle as a handle instead of those two red ball-pins. That might "break" the big red surface a bit.

 

 

On 7/22/2024 at 7:13 PM, pleegwat said:

Storage room. Firemen need a lot of equipment. This includes firehoses and nozzles, but there are also axes, hydraulic cutters, and many other things I'm not thinking of right now. Every nook and cranny will be stuffed with storage cabinets.

A ladder car will also have a big water pump. I'm not sure if a water tank (in case no surface water or hydrant is available) would be on the same vehicle.

Thanks for all the comments.
I stuck to the 15 wide body. I did some work on a 13 wide body, and it is doable, but with the ladder mounted is is indeed less boxy as @CK28 predicted. I have no photos yet of the model with ladder as it is too dark now for photos.
@Erik Leppen thanks for all the suggestions to break the boxiness. The ladders must be mounted straight, also that area is pretty much filled to the brim with the gearing for the winch, but changing the colour of the openable panels is something I will give a try. The corners will become macaroni pieces, I didn't have them in my collection at the time of the photo. I am also tempted to add a stripe of neon-yellow, but also those pieces I only have a few of.

@Ngoc Nguyen: that is a very generous offer to make instructions. I'll keep that in mind.

@pleegwat: Good point, I will see if I can add some accesories or extra hatches.

Now for the update...

I did finish a first version of the whole thing and a few things really need to change:
The speed of the functions is totally unbalanced. The ladder functions are about 10x slower then the rest, so they are basically unplayable.
The bidirectional switches don't make the play experience better. In fact they make it worse as they are on both sides of the vehicle, so you can't see them all at the same time. All functions can run in parallel, but there is actually no need for that, I never felt the need to extend the outriggers and rotate the superstructure for example. And switching direction is much more natural done with the switch on the batterybox.

So I have decided to completely redesign the function selector mechanism. I use a waveselector to choose between the four main functions (rotate superstructure, raise ladder, extend ladder, deploy outriggers). I then have a second selector that is in front of the waveselector that switches the power to the waveselector functions on or off. The winch in the back has it's own DNR switch and is always powered by the motor.

Here is an early iteration of this concept:

There are now 9 functions routed through an 9x9x9 box:

red: selector to switch power to the main functions on or off
orange: selector for the 4 main functions
pink: motor output going to the back for the winch and to the first selector
dark grey: motor output going to the four main functions
black: drive to fake engine
yellow: steering axle for rear axle
light grey: raising ladder
blue: extending ladder
dark green: rotation of the superstructure
dark azure: deployment of the outriggers (going to both sides of this gearbox as the outriggers are both in front and behind the gearbox)

Unfortunately when I tested this configuration I found out that when driving the outriggers, the dark azure axle in the front rotated contrary to the pink 20T clutch gear causing a massive friction. I also didn't like that I had to move some of the dark azure gears backwards to make space for the motor that will sit on top. So back to the drawing board for iteration number thirty or so:

As you can see all the functions are now within the 11 studs length of the frames. As a bonus I was also able to squeeze in a friction clutch gear in the motor drive chain. The function speeds should be more comparable now as there is a wormgear for the turntable. The outriggers will also get a wormgear each (still to be designed) and the winch will get some downgearing along the way.

I'll post some photos in the weekend of the completed model before I take it apart to install this new gearbox.

Edited July 25 by Jeroen Ottens
completed explanation of the colours

[Erik Leppen]

1 hour ago, Jeroen Ottens said:

 

Now you're just mocking us with complexity for complexity's sake, just admit it 

 

Kidding, just kidding 

[Paul B Technic]

Awesome work, this looks really complex but you have shown it well.

[Jeroen Ottens]

16 hours ago, Erik Leppen said:

Now you're just mocking us with complexity for complexity's sake, just admit it 

 

Kidding, just kidding 

Here are the promised photos of the completed model before I take it apart to solve all the issues:

You can clearly see the problem with the outriggers not holding their position when not in gear.

The ladder is brick-built, I have contemplated to use the frames of the Liebherr crawler for the sides, but they are yellow, which I think really clashes as a colour. And I don't have them (and they are pricey). I use a chaindrive to extend the ladder. I am still doubting whether I should try to use the new 6L wormgears. I do have those lying around. At first I didn't want to use them because I feared it would be too bulky, but I actually use quite some vertical space as it is now, so that may not be that strong of an argument. It is not self-braking, that is a bigger issue, it would require another wormgear in the drivetrain to solve that...

The reach is 60 cm when fully extended, which is slightly more than the 56 cm the model is long.

[NV Lego technic]

Very cool! The fact that you have a 9 function gearbox in that compact form factor really impresses me.

[Jeroen Ottens]

Final (hopefully) update on the function selector gearbox. I was still unhappy with the previous iteration. It felt overcomplicated and too finnicky. So I made yet another set of iterations.

Advantages of this version are:
- Less gears due to simpler routing of the axles (especially the dark azure outrigger function is gone from 14 gears to 5)
- cleaner packaging with better bracing
- on the top side it is narrow enough to add the plating for the central rasied element and even cover most of it
- room for fake hose connectors on one side

Disadvantages are:
- The two selectors are now on both sides of the vehicle
- The Control+ hub has to move one stud closer to the superstructure (which is only an aesthetic change)
- The operation of the main function selector is done with a 12T bevel gear, that is close to fast spinning 16T gears, I might have to change that to prevent my fingers getting chewed off

[Thirdwigg]

This is looking very good. The ladder, specifically the reach is very well done. I'm interested to see the new worm gear option for the ladder extension, but I understand the time that may take for a full ladder rebuild.