[TC25] 8109 Flatbed Truck

[SaperPL]

After doing some research, I decided to go with 8109 Flatbed Truck because of colour scheme which should be easy to replicate without hunting for exotic parts in specific colours as well as the fact that I wanted to do something slightly different.

FINAL MODEL:

 Full Size Photo Original Model

 Full Size Photo Original Model

 Full Size Photo Original Model

 Full Size Photo

Instructions on Rebrickable: https://rebrickable.com/mocs/MOC-155661

ORIGINAL POST:

 

It is also a set without a fake piston engine so I don't have to fight to squeeze in the drive train and the engine in this scale.

What I like in this set is in particular the kneeling/lowering of the rear of the truck alongside raising end extending the flatbed, which is a pretty cool mechanism to try and make more compact: Lego Technic 8109 Flatbed Truck Speed Build - AustrianBrickFan

The extension of a tow wheel holder is really cool as well, but I don't think I'll be able to fit such mechanism at my scale, because the bed pivots over last axle and cuts corner this way in the original model.

I managed to make an initial prototype for the bed and kneeling geometry, but I'm not yet sure about whether I should use the single linear actuator like this, or make it two so there's room in the middle between them to drive the tow wheel holder extension there.

So far good enough, but I don't like how far up front is the knob for this function. I didn't check the proportions/spacing between front and rear axles, so the whole thing might be long enough already and the knob would not be where the original model had the controls.

Edited August 9, 2023 by SaperPL

[2GodBDGlory]

Wow, I never realized how impressive the functions in that set were! I might have to  build it some time.

Good work replicating them at a smaller scale!

[artemisovsky]

I didn't think it was possible to use such a mechanism in this little scale, looks awesome. This is another interesting project that I will observe in this contest.

[SaperPL]

Sculpted a bit to see how feasible it is to achieve the looks:

 

Fitting controls for mechanisation side by side seems doable although it might have a weak connection...

The bigger problem is how to implement the tray extension - not much room to do anything reasonable here. I might need to figure out something completely different than linear actuator, maybe just a sliding mechanism with some sticking out lever

[SaperPL]

A few iterations later...

I managed to improve the layout to have some room at the back for towing tray. Also after multiple attempts, I dropped the idea of having the knob for the bed raising at the sides under the opening/tilting panel like the original placement of gearbox switch because turning the knob that more than a flush in with sides, the bed above and panel below are sticking out for 1 stud more than the knob/12T gear that is inside. I will place the input(s) for the functions on top of the cab. Thanks to not having to make 90 degree turn in the pivot of linear actuator, I will be able to pass the second input below. The problem is that I have very little amount of space at the back and between rear wheels...

For now, I managed to make a simplistic manual ^2 tow tray with rubber band loaded opening:

I'm not satisfied with this for two reasons: because it has to be put together back in a cumbersome way, as well as it's not placed as in the original model where vertically it was in line with axles. Not sure though if I'll be able to fix the latter as there's really no space at the back because of two moving L-liftarms which define the tilt angle for the platform being attached at the very end down there.

[lcvisser]

I also never realized this set had such  interesting mechanisms hidden inside. Good progress so far, impressive hope you managed to replicate it at such small scale! This contest is producing all kinds of interesting mechanisms!

[SaperPL]

3 minutes ago, lcvisser said:

I also never realized this set had such  interesting mechanisms hidden inside.

I didn't even know about the existence of this set before the contest. I just wen through the all sets historically and decided that I don't want to go for a mobile crane or other construction equipment because it'd get pretty generic quickly. Also I didn't want to make something with knuckle boom crane or excavator in a way that it'd have a knob for linear actuator at each joint rather than routing inputs to one place, so for me it was either something in the middle between simply cars and some industrial equipment and then I found this set which is awesome for me because of colors used.

Btw I also tried figuring out whether I could make a supercar with suspension and a gearbox using the ball based friction CVT design, but it quickly came to a point where I realised i'll end up with something looking like a complete mess from the outside.

10 minutes ago, lcvisser said:

Good progress so far, impressive hope you managed to replicate it at such small scale!

Thanks!

9 minutes ago, lcvisser said:

This contest is producing all kinds of interesting mechanisms!

Yeah, like most of the contests that were about small scale models. I come back often to take a look at the cars in TC18 - that ones was really interesting, but I missed that.

I like the challenge of of 9 stud wide and even 7 stud wide like others are doing, but for me it's not something that's going to be instruction worthy, so I prefer going with 11 stud wide models because steering and frames are fitting this scale well without special shenanigans.

[Paul B Technic]

You have done really well to get this down so small.

 

[TechnicMOCer]

I love how the Stud.io model looks, but I think you can add red hose as wheel arch. The bed elevation works very well too. I'm not sure about tow bar - isn't it too weak to tow some car/truck? As well as mirrors are oversized in my opinion.

Edited July 2, 2023 by TechnicMOCer

[SaperPL]

2 hours ago, TechnicMOCer said:

I love how the Stud.io model looks, but I think you can add red hose as wheel arch.

 

2 hours ago, TechnicMOCer said:

As well as mirrors are oversized in my opinion.

I've taken the big chunk of the cabin from my semi truck model just to figure out where how long the whole thing would be and how tall the cabin should be for reference when building the bed, so whole thing wouldn't be weirdly stretched. Probably the front needs to be remade as it's something mostly built with system pieces and model team approach is not okay for the contest. I can ask about this, but first I'll try to do something in Technic.

2 hours ago, TechnicMOCer said:

I'm not sure about tow bar - isn't it too weak to tow some car/truck?

Surprisingly despite it being a 11 stud long flip flop beam/liftarm holding by two 15100 pins onto an axle which it's sliding on, this thing can pull up whole model around the last axle when pressed down. It's not the problem here. The problem is that it's too high and the wheel wells on the tow bar are pretty smal and tilted, and of course the mechanism itself is something I'd like to replicate more as the original one.

5 hours ago, TangersTechnic said:

You have done really well to get this down so small.

Thanks!

[SaperPL]

Updated the studio model to current version of the bed raising mechanism:

Hopefully it's clear enough to understand how it works: the 12L axles and that one 4L L-liftarm are fixed together in the platform and the platform is sliding with those 12L axle on the four pin holes over the rear axles.

Sides and front axle structure (just to figure out the spacing)

And finally the platform and the cab (still quickly mashed together placeholder) on top of it:

I didn't realise it before, but if I want to put multiple control inputs on the roof of the cab, I might have another challenge in the cab where I need to angle those control inputs by 90 degree in tight spot between the end of the platform and front axle.

Right now there's a lot of space used for the sake of using those half stud shifted steering pivot arms, but I'm not even sure that's not going to collide with front of the cab/bumper area. One thing they are doing is that they are going only half stud down below the level of the axle, which means I can have full clearance underneath the truck without anything sticking out more than the side skirts. The other approach is to use the new 2393 connector.

Still, need to figure out what to do about the tow bar/tow tray mechanism.

[GerritvdG]

Fantastic progress here, keep up the good work! The mirrors are a little big though....

[SaperPL]

8 hours ago, GerritvdG said:

Fantastic progress here, keep up the good work!

Thanks!

8 hours ago, GerritvdG said:

The mirrors are a little big though....

Once again - the cab is a copy-over placeholder from another project just to match scale. Didn't do much there yet, will get there once I have the layout of control inputs inside the cab.

 

Meanwhile - I figured out the mechanism of extending the tow bar/tow tray:

 

Fits where I want it to fit, but I don't like that the angle limiter takes whole stud because when extended it sits on the floor/ground. The tow bar is strong enough when extended to hold something, but the amount of extension is limited by how much linear actuator extends, so a small corresponding size model has hard time fitting its wheels so close to the edge fo the platform on this tow bar. More like for towing something slightly smaller scale without the front bumper sticking out much.

Anyone has ideas on how to reduce the size of that angle limiter to half stud? is there anything that holds onto axle but is not full 2 studs long and can hold something else to limit the tilt angle?

[TechnicMOCer]

Now seems to work very well! I think I'll make mini (3x smaller) 8110 Unimog though. As your question why, I've had to low front suspension. Then front wheels turned inside that when you turn left, right wheel turns too much, that makes steering and driving at the same time uncomfortable. Real motor vehicles have such a thing, but when you turn left, left wheel turns more (and not so much, it can be counted - depends from that how long and wide is vehicle). In Lego there is the same turn on both wheels, so it is simplified but perfectly sufficient (unless you will make steering linkage in different way).

[SaperPL]

11 minutes ago, TechnicMOCer said:

I think I'll make mini (3x smaller) 8110 Unimog though. As your question why, I've had to low front suspension. Then front wheels turned inside that when you turn left, right wheel turns too much, that makes steering and driving at the same time uncomfortable. Real motor vehicles have such a thing, but when you turn left, left wheel turns more (and not so much, it can be counted - depends from that how long and wide is vehicle). In Lego there is the same turn on both wheels, so it is simplified but perfectly sufficient (unless you will make steering linkage in different way).

I think you wrote this in the wrong topic :P

[TechnicMOCer]

31 minutes ago, SaperPL said:

I think you wrote this in the wrong topic :P

Eh, probably. 

[SaperPL]

I don't like cranking the knob a lot, so I experimented a bit with the no linear actuator approach:

I'm not really sure whether to go this route or get back to cranking the linear actuator with some gearing to speed things up a bit. This one without gears is too fast and also affects the connection between the chassis and it takes ton of space to implement the lever that is perpendicular in two directions... And overall that's a messy build because of that.

I also don't know if a car owner would like to see his towed car do an instant whoop when the tow truck bed is retracting this fast xD

[arijitdas]

9 hours ago, SaperPL said:

I'm not really sure whether to go this route or get back to cranking the linear actuator with some gearing to speed things up a bit. This one without gears is too fast and also affects the connection between the chassis and it takes ton of space to implement the lever that is perpendicular in two directions... And overall that's a messy build because of that.

I think the LA solution you had implemented earlier looked better and more realistic.

[XTN]

9 hours ago, SaperPL said:

I don't like cranking the knob a lot, so I experimented a bit with the no linear actuator approach:

[...]

I'm not really sure whether to go this route or get back to cranking the linear actuator with some gearing to speed things up a bit. This one without gears is too fast and also affects the connection between the chassis and it takes ton of space to implement the lever that is perpendicular in two directions... And overall that's a messy build because of that.

I also don't know if a car owner would like to see his towed car do an instant whoop when the tow truck bed is retracting this fast xD

Impressive progress so far!
In my eyes both variants are like black magic. 

The speed of moving the platform via linear actuator is absolutely okay. It's not too slow, compared to real life rollback trucks.
So if you are looking for other people's opinion, I am in team LA.

Btw I instantly fell in love with the way u use those panels at the rear edge of the platform. After seeing it on your truck, it seems so obvious now...

[SaperPL]

30 minutes ago, arijitdas said:

I think the LA solution you had implemented earlier looked better and more realistic.

 

2 minutes ago, XTN said:

In my eyes both variants are like black magic. 

The speed of moving the platform via linear actuator is absolutely okay. It's not too slow, compared to real life rollback trucks.
 So if you are looking for other people's opinion, I am in team LA.

Note that in previous gifs I cut down 75% of frames so the gif wouldn't be too big and too slow, so the linear actuator version here is sped up 4x. That's why it looks like black magic. But I should be able to get close to that speed with some gearing because all gifs were made without any gearing before linear actuator input, and I've tested the double gearing already and it's working okay.

6 minutes ago, XTN said:

Btw I instantly fell in love with the way u use those panels at the rear edge of the platform. After seeing it on your truck, it seems so obvious now...

Yeah, before this panel, having a ramp connection with ground was a pain to build cleanly at this scale and required using bionicle eye/claw piece:

Anyway, I will probably get back to linear actuator implementation, but with gearing, mostly because the construction is messy now, but also as you guys said, slow raising seems more realistic.

[SaperPL]

Worked on the input structure some more and figured out some initial approach how to do this with a fake battery box encapsulating the universal joint + CV joint shift of the steering input to where it was in the original model:

I is however still 1 stud too high when comparing it to original model as it will be seen from the top and in the set it was beneath the roof top level. The problem is that if I were to go lower, I would need to figure out what to attach gears for linear actuator input to, and change CV joint to universal joint and also the knob for platform raising would go lower which wouldn't be at the same height as the knob for winch on the platform. Now they are aligned so this should look better than if I were to move it down.

Started working on a cab and there's a lot of different tricky places I need to figure out how to tackle because those small panels have barely any attachment points...

I need to figure out how to tackle the front... Might want to check with Jim if studded front like in my truck and above studio model is okay or not for the competition. The original model had the studded grill and lights only.

Still a lot to figure out about the cab, but at least I have some idea of how to tackle the steering inputs alerady.

[TechnicMOCer]

7 hours ago, SaperPL said:

Worked on the input structure some more and figured out some initial approach how to do this with a fake battery box encapsulating the universal joint + CV joint shift of the steering input to where it was in the original model:

I is however still 1 stud too high when comparing it to original model as it will be seen from the top and in the set it was beneath the roof top level. The problem is that if I were to go lower, I would need to figure out what to attach gears for linear actuator input to, and change CV joint to universal joint and also the knob for platform raising would go lower which wouldn't be at the same height as the knob for winch on the platform. Now they are aligned so this should look better than if I were to move it down.

Started working on a cab and there's a lot of different tricky places I need to figure out how to tackle because those small panels have barely any attachment points...

I need to figure out how to tackle the front... Might want to check with Jim if studded front like in my truck and above studio model is okay or not for the competition. The original model had the studded grill and lights only.

Still a lot to figure out about the cab, but at least I have some idea of how to tackle the steering inputs alerady.

What about changing cab's front corners to small 2x3 panels fairings #7 and #8 to make wider grill so it would be more accurate to original set.

 

Isn't it possible to make HOG without joints, just with axles? Whole truck is long so HOG placed a bit more on the front wouldn't be problem.

 

Also I'd recommend for you make mudguards with axle and pin connectors or hose, to make model more neat and again, more accurate to original set.

Edited July 8, 2023 by TechnicMOCer

[Timewhatistime]

On 7/2/2023 at 11:39 PM, SaperPL said:

Anyone has ideas on how to reduce the size of that angle limiter to half stud? is there anything that holds onto axle but is not full 2 studs long and can hold something else to limit the tilt angle?

I suggest to replace both of the grey 2L liftarms (the +o ones) by two of these parts (1x1 brick wiht axle hole): 

https://www.bricklink.com/catalogItemIn.asp?P=73230&in=S

After that connect both with a simple 1x3 plate (a 1x3 tile will fit your requirement of ground clearance even better) to get an angle limiter. 

Just try which orientation will serve your purposes in a better way: There is the choice of mounting it underneath the long liftarm - so it will be under the chassis while driving and above the chassis after extension... or you could flip it over (which will result in less ground clearance after extension, but no obstacles for the picked vehicle located on the boom).

It may be a bit weak because of the stud-based connection, but I hope it will be strong enough for your application. One could improve it by using two of the 1x1 bricks on each side; the connection could be done by this part (which will sit very tightly on the studs)

https://www.bricklink.com/v2/catalog/catalogitem.page?id=197#T=C

Another possibilty would be a 1x6 tile placed centered (i.e. with a half stud offset). Not sure if there is a 1x5 tile...

 

My favourite suggestion in terms of rigidity an ground clearance would be the connection of two 1x1 bricks on each side by a flat 1x5 liftarm; it's holes will sit very tightly on the studs. The connection relying on four studs in four holes should be quite safe and sturdy.

You will figure it out!

 

Btw, nice choice! I really like the 8109 mechanisms too.

One can only wonder why the usage of the new 3x1 panels for the ramp's rear end wasn't discovered earlier. I believe we will see them more often in the future at these and similar places.

Edited July 9, 2023 by Timewhatistime
Parts added

[SaperPL]

53 minutes ago, Timewhatistime said:

I suggest to replace both of the grey 2L liftarms (the +o ones) by two of these parts (1x1 brick wiht axle hole): 

https://www.bricklink.com/catalogItemIn.asp?P=73230&in=S

After that connect both with a simple 1x3 plate (a 1x3 tile will fit your requirement of ground clearance even better) to get an angle limiter.

Thanks, but I doubt this is a valid solution as it'll probably easily fall apart under any load. 

 

58 minutes ago, Timewhatistime said:

One can only wonder why the usage of the new 3x1 panels for the ramp's rear end wasn't discovered earlier. I believe we will see them more often in the future at these and similar places.

I didn't think that would be something that noone did before. But yeah, I didn't see it. Apart from this, those panels are neat for assembling things with half stud shift.

[Timewhatistime]

Maybe my alternative suggestions will be more adequate.

I started by sticking as close as possible to your original draft. The alternative suggestions maybe will require some changes in your constructions which are not visible on the provided pictures, so I cannot be sure about that.

Edited July 9, 2023 by Timewhatistime
Mistake