[WIP] Longnose tow truck in 42008 scale - design question

[Erik Leppen]

I'm building a tow truck, and I'm running into a problem with the design of the functions. First, let's do an image of what we're talking about.

As you see, it's a smaller-scale version of a tow truck similar to 8285, but with an extra axle. The wheels will be those from 42024 and other sets. Because of the scale, there is probably not enough room to add PF. So right now I'm aiming to have it manual. As far as I can see now, there will be the following functions:

• steering
• main boom raising/lowering
• main boom extension
• main boom winch
• car lifter raising/lowering
• car lifter fold out/in
• outriggers

The steering is done and controlled by the gear on the roof. The car lifter fold in/out will be manual with a knob at the back. Remaining are 5 functions. The question I'm having now is, how to drive those. Of course, with the model being manual, I could just add a knob for every function. But this doesn't sound like the most technically challenging option, so I am thinking of adding some kind of switchbox. But, 5 functions is kind of an unwieldy number, ecause it requires 3 switches with 1 being half-used. Currently, the outriggers are driven by knobs on the side, and I could leave it that way and have 4 functions running from the switchbox, but this feels kind of incomplete as well. So I'm unsure about where to go from here. So I'm looking for some advice. What do you think? Are there other options? What would you do?

[Lakop]

Very nice work. I'm sure you can find a way. having two switches at either side of the truck or some switching close to roof. Those are the same issues I face all the time but practice makes perfect.

H

Edited May 17, 2017 by Horace T

[Marxpek]

I don't know if this is an option to you but maybe it is an idea, remove the linear actuators and use pneumatic there and make the car lift pneumatic as well (8285 had that).

That would leave you with 4 functions left for the gearbox.

Nice project good luck!

[Erik Leppen]

Pneumatics, I'm afraid, is not an option. I sold my pneumatic parts a few years back and I missed out on the Arocs.
Anyhow, after a looong stretch of fiddling around with MLCAD, I might have come up with a way of motorizing 4 functions. It has a few problems though, and I have to try it in real bricks to know if it even works.

• Medium green = steering
• Azure = motorization and switches
• Orange = outriggers
• Violet = main boom lift
• Purple (only that one gear) = will go to the extension
• Light green = car lift

This means the winch will still be manual, which I find to be a nice compromise, because then I can add a ratchet mechanism.

 

First, I noticed in the version on the photographs, there was empty space under the hood. I figured, what if I could put an M motor there? And could a battery box fit behind the cabin (where it often is in sets as well)? Maybe... So I started trying to fit a gearbox in the remaining space. To make this fit, I had to make the truck one stud longer. The dimensions of the truck were taken from a photo, so I didn't want to move things too much. One stud may be OK.

The possible issues with the solution are:

 

• he hood doesn't fully close anymore. So I may have to change the shape of the hood a bit.
• ll the gearing just fits. In many places there's no way to switch gears around. The 20:16 gearing from the motor can only be that or 24:12, or it won't fit. The two orange gears you see have to be 16:16, or it won't fit. The light green 16:20 can only be that or 20:16, or it won't fit. Same goes for many other places. So, if any function moves way too fast or way too slow, I'm basically screwed.
• The light green geartrain uses a lot of universal/CV joints to go around the rest, but this is a small function so I hope it won't be a problem
• The truck is 13 studs wide, and the battery box is 11 wide (I don't have any other BB's). I had planned for some nice chimneys right behind the cabin using 2x2 round bricks, but that wouldn't fit. So I will have to change the chimneys to something smaller.
• I used the old 2L driving ring, so the switches are offset a half stud.
• The sleeper cabin will be entirely filled with gearing...
• The battery box prevents me from adding a reinforcement beam straight from the top of the cabin backwards. Hopefully rigidity won't suffer too much.
• I haven't planned the cable from the BB to the motor yet

Next step is to try this with real bricks to see what works and what doesn't...

 

(By the way this is how I always work nowadays. Use MLCad and real bricks in unison, because by switching all the time, I automatically build everything multiple times, and with every build I keep finding new solutions (and with real bricks I see other things than virtually), making for a better end result.

[Thirdwigg]

I'm happy to see another project in the works, Erik. I support the project without a motor, though it seems like you are able to add it in. I think you made the right decision about the four functions in the gearbox. Working the winch and car lift separately will work well. I like what I see so far, so keep it up. I look forward to the final project.

[steph77]

+1 with Thirdwigg.

But i think (i am sure) that have it with PFS is possible.

Look at this truck i build previously:

There was 8 functions for one M motor.

So my thought , looking at your WIP, is keep it up!

Spoiler

 

EDIT

What is sure is that your inner design will look like this ;)

Edited May 17, 2017 by steph77
add inner design

[Erik Leppen]

Thing is, I like symmetry. So if i have any choice, I prefer to let things go through the middle, rather than the sides. But there's only so much middle in a model, of course. So I doubt I'd be able to design something like that, @steph77...

Anyhow, there's progress! I built my virtual design in real:

 

I left a few things out (rear wheel arches, boom) because they haven't changed. I changed the shape of the chimneys so they are less wide (they now partially fall in the slit between the battery box's connectors. The BB fits perfectly, although it just sits there loose (not connected to anything).

I had to make a few changes though. The gears from the motor are now 12:24, meaning the front grille can't be fixed there anymore, so the connection to the grille is kinda weak. Some functions are still too fast, I don't know how I can change those. Boom lift is fine. Outriggers are too fast. Car lift is a bit fast as well. Fourth function isn't implemented yet.

The bright moment I had was when I found that there was room between the outrigger drive axles to drive the outrigger system right through the center. The axle to drive the car lift had to move up one stud, so it has 4 U-joints now... By the way, I'm glad the axle 11 exists, because I needed it in a few places :)

Sleeper cabin is now filled with gearing, but I keep the openable doors, I like them. I might add something in red right above the gearbox to represent some kind of bed.

[agrof]

Great project, I love these dense builds.  The color scheme is also a very good choice, and looks well balanced. Maybe for the hood You could test something like 9397 has, in smaller scale.

[Didumos69]

This is the kind of puzzling / tinkering I love to see! And it seems to progress quite well! I'm looking forward to seeing the next steps.

Edited May 19, 2017 by Didumos69

[steph77]

ok.

Your design is on the good way it seems.

Personnaly, as I build model for my son, I always insert clutches in the system.

- Or it is placed directly at the motor output with 8T/clutch

- Or, like on my vovlvo truck, it is placed at the end of kinetics chains.

I also like your direction system ;) it generate an offset of 1/2 in vertical alignment but that will be very useful for the mudguards design ...

Keep it up!

 

[Erik Leppen]

Sorry for the long pause, but I often build with pauses. To be honest I'm losing a bit of interest (this can go rather quick with me), so I hope to finish it soon. I'm almost done though, all that remains is the car lift at the end, and figure out some way to add rear lights.

Here's the progress right now.

I changed the gearing from the M motor from 20:16 to 12:24 which reduces the speed greatly. Some functions are still too fast though, while lifting is a bit slow. It's hard to change that, there's not much room anywhere. I understand that black is not the best color on pictures, so I hope you can see what's going on. This will probably be the last update before finishing.

The white Bionicle tooth controls one of the two switchers. It is connected via some liftarms to the switcher. The reason for this is that this way, the roof is free of switches and can therefore use a large panel, viging it a cleaner look. By the way, there's a tiny red "bed"-like thing in the sleeper cabin, and its doors can open too.

The winches are connected to each other and to a ratchet mechanism using the rubber 2L beam. It is not driven by the gearbox. One little problem with the winches is that they only run in parallel if the strings are rolled the same way (and have the same length).

By the way @steph77, the steering is not my own invention. I used it in my [TC7] Enforcer (Valuable Transport) where I borrowed it from @D3K and reinforced it (which introduced the 1/2 vertical offset). This tow truck has a huuuuge turning circle though. Not surprising given its length, but the steering angle is a bit limited and it has only one steered axle.

[steph77]

Hi Erik,

You manage it in a very cool design :)

Love it !

 I actually work on a truck at the same scale and I know there is not much room inside of this kind of MOC, so I think you have made a really cool job.

Anyhow, and I didn't know if it can help you (speeking of the speed of the function), i actually work and think on the same issue with my refuse truck. One of the solution is change the medium motor to XL one as these one have a lower RPM ....maybe can be useful however it doesn't seems to have place for it

Great job!

Edited June 16, 2017 by steph77

[Jeroen Ottens]

Oh wow

This is looking really cool. You're a master at this scale (as is @steph77), please keep your interest up

[Didumos69]

Excellent work! I also really like to see your models on Rebrickable these days. I think it will give your excellent cranes much more 'reach' . So you plan for instructions for this one too?

[nerdsforprez]

On 5/17/2017 at 3:24 PM, Thirdwigg said:

I'm happy to see another project in the works, Erik. I support the project without a motor, though it seems like you are able to add it in. I think you made the right decision about the four functions in the gearbox. Working the winch and car lift separately will work well. I like what I see so far, so keep it up. I look forward to the final project.

 

4 hours ago, Didumos69 said:

Excellent work! I also really like to see your models on Rebrickable these days. I think it will give your excellent cranes much more 'reach' . So you plan for instructions for this one too?

I second the eight for possible instructions......and the plea to keep at it

I am following this project as well and would love to build it sometime. Love your builds!

[Erik Leppen]

Thanks for the kind reactions! Yes, if people are interested, I may do instructions. I keep a digital file anyway,  and it's not a huge model. Also it's a nice addition to my "portfolio" of models, I usually don't do tow trucks.

 

Edit: also, yes, I looove this new scale and wheels. In fact, I hardly use the larger 64x20 wheels nowadays :D

Edited June 18, 2017 by Erik Leppen

[Aleh]

Hey! I like your towtruck! May I advice you to add one steering axle (the second) befind the exhaust pipes?
Real truck has 2 front and 3 rear axles..

Design of the pipes is fantastic! Well done!

[Erik Leppen]

I don't think that's possible. There's a gearbox in the way.

Also, it's not needed. I based mine on this picture I found:

Thanks for the comment on the exhausts. I was quite unsure of them. They're actually a secondary solution, because the battery box had to fit between them.

[Aleh]

Erik Leppen, sure. But that is what I mean:

[Erik Leppen]

I know what you mean. But your picture is a different truck than the one I'm building. I know I have outriggers and the original doesn't. I use a bit of artistic freedom to add more technic to my models. But I based the dimensions and axle configuration off my reference picture, and I won't change that.

But your picture is definitely interesting, so I saved it for another time. Maybe some day :)

[Saberwing40k]

Regarding your issue with turning radius, could you remove the virtual pivot steering? I'm not sure if you gain anything from having it.