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TOPIC: Blakbird's 56325 MAN TGX 26.540 Build

Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57224

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This truck marks the end of a long story. I've been coveting RC4WD's line of hydraulic construction machinery for a long time, but they are prohibitively expensive. They are also almost all RTR which takes a lot of the fun out of it for me. The lowest cost item is a hydraulic truck mounted crane which is also the only one that comes as a kit. Even then the price was a problem but RC4WD had a great holiday sale in December of 2018 so I bought one. I was somewhat intimidated by the kit and sat on it for a couple months until beginning the build in February without any truck to mount it on. I built a temporary mount on a block of wood which allowed me to set up and operate the crane. The mechanical part of the build was simple enough, but getting all the plumbing done without leaking everywhere took forever. Once I got everything working though, I found the crane incredibly capable.

It wasn't until June that I decided upon a candidate truck for the crane. I wanted a truck that would accept that crane with minimum modifications. I also wanted a truck that was otherwise fairly plain in appearance so the crane would be the main visual draw. I decided upon the MAN TGX 6x4 which had plenty of room behind the cab and a sturdy chassis. Installation of the crane required some minor mods like removing the fake side tanks and replacing them with the hydraulic reservoir and valve block. I also had to trim various fairings and spoilers to make room for outriggers.

And then there were the major changes. Tamiya cabover trucks install the steering servo on the left side of the chassis, but that space was now taken by the hydraulic valve block. I had to move the steering servo up front and make my own linkage which displaced the shift servo. This means I couldn't shift the 3-speed transmission. Another item I'd been coveting but had no use for was the CVT (Continuously Variable Transmission) from RC4WD. The lack of a working 3-speed in this model made it a good choice for this transmission but it was out of stock. It was September before I got my hands on one. The CVT weighs a ton and also generates a lot of waste heat. It was not easy to install with the crane in place either. I'd like to say that it was a rousing success, but as far as I can tell it doesn't work. The gear ratio is supposedly variable by a factor of 5 but I can't see any evidence that it is changing at all. It drives, but I wouldn't recommend it for the price.

I usually install an MFC (Multi-Function Control Unit) for lights, sound, and vibration on my tractor trucks but the place where the control panel would go was taken by the hydraulic reservoir. Instead I installed a TLU-01 based light system with 20 lights and miles more wiring.

Operating this truck requires a total of 7 channels. I need throttle and steering for the truck, and hydraulic pump with 4 valves for the crane. I wanted to operate the crane with a twin stick radio but the truck with a pistol grip, so I had to use two different radios along with their associated ESCs and receivers. Along with the light controllers that makes for a lot of electronics.

This is probably the most work I've ever put into a single model. The build spanned 7 months and multiple week long building sessions. The result is incredible though. This truck has so much to offer. Everything works well but the tremendous weight bottoms out the suspension and partially flattens the front tires. I am still searching for a way to solve this problem.

Since I've already fully documented a tractor truck build on my King Hauler page and the chassis is 90% similar, I'll be providing only a cursory overview of the build here. My cabover 6x4 Scania is even more similar.

While most tractor trucks seem to come in white boxes, a couple of the more recent releases have a black background. We still have old school hand drawn art and the typically subdivided interior though.
This chassis looks exactly like my Scania from the reverse Ackerman front steering to the side mounted servo. The only obvious difference is the shape of the side skirts. Once the body is attached as shown on the right, the differences become more obvious. I usually paint the body before installing, but I knew I would have to make modifications to this body to accommodate the crane so I installed it first. At this point there are still big gaps behind the cab where fairings should be because they don't fit around the crane.
I chose a dark brown for this build to make it stand out from my other models. I wanted something neutral that would not clash with the red anodized crane. I've assembled the front bumper and the cab completely including black accents and some minimal stickers. The interior is not installed yet because I didn't know if it would fit. It did.
I rarely get to install tractor truck interiors because the space is usually taken by a Multi-Function Control Unit. In this case I am not using an MFC because I need room for the electronics powering the crane. I used dark gray for the very nicely detailed dash panel and seats as shown. I still need to install a driver.
The completed truck looks pretty normal if you don't notice that crane peeking out behind the cab. The fifth wheel is still usable to pull a trailer only if that trailer has a very short overhang in front of the kingpin.
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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57228

Interesting build - you certainly packed a lot of electronics etc into a small pace, but ouch, the price of the crane :blink:

I mean this next bit as constructive criticism, but I have to question the realism of having a HIAB on the back of a tractor unit. As you say, it compromises the trailers it can haul, and it has no loadspace to carry anything it does lift. Trucks that pick up pallets & large loads (on a fully commercial basis at least) don't go around unhitching the cab, they have a small gas powered forklift truck on the back of the trailer.

Where you do see trucks like this (in the UK at least) is generally builder's merchants delivering pallets of bricks & cubic metre bags of aggregate etc, out of a medium of long flat bed.

How amenable is this chassis to extending? (I've never had one myself). I would hope it's "just" a matter of finding somewhere to chop it and add 200mm or so of chassis rail, extending the driveshat & making a flat bed.

I also think the brown is a little dull, and some small stripes/graphics in other autumnal colours (orange, beige, gold) would really lift it :)


ps I'd also like to see more pics of the crane, CVT & how you stuffed it all in :)

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57232

Awesome! A functional crane...
This brown merits pin stripping like said Jonny.

More details of the crane and a video working please :p

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57238

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Don't worry, plenty more information is on the way. Regarding the realism of this kind of crane on a tractor truck, I have certainly seen them but you are right that a flatbed would be more realistic. I was thinking that pulling a flatbed trailer would be a good compromise. Doing my own chassis extension is beyond the level of customization I am currently comfortable with. To be honest, this project was all about the crane and the truck is just there to hold it up! I agree that the brown is dull which was actually intentional to not detract from the crane. I also agree pin-striping would look good but I'm no good with freehand painting or designing patterns. Any recommendations for something to emulate?

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57240

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I'd never built anything quite like this crane before and was not sure what to expect. Part of my trepidation was due to the fact that this is a real hydraulic model, and part was lack of familiarity with the brand. You just never know what to expect from an unknown Chinese brand. Luckily for me, the packaging did a lot to assuage my fears. The kit comes in a very thick box with everything individually packed in foam dividers. Every single part of this is metal: aluminum, steel, or brass.
We'll start with the easy parts: the outriggers. The outriggers on this model are not hydraulically powered. Instead they are manually extended and lowered. Each foot locks into the extended position which makes it possible to support the whole truck. The unit shown is for the rear outriggers which go behind the back bumper. The two extendable arms overlap each other when retracted. There are set screws which poke into a groove in the arms to keep the arms from over extending and falling out, but one of the pre-drilled holes did not line up with the groove so the screw could not be installed. Score -1 for quality on the first step.
The front outriggers which sit right behind the truck cab are completely different. These are 3 stage telescoping units which are very long indeed. Because the arms must sit above the chassis rails, the cylinders for the feet are much longer than those in the rear. The spring that you see on the left is used to hold the foot in the retracted position when driving. The telescoping arms have no such spring though, so they tend to fly out when the truck is cornering. I added some black electrical tape to make them fit more tightly and stay in place.
Now we'll start working on the actual mechanical bits. Shown on the left are the parts for the turntable. The vertical shaft serves as a pinion gear and the horizontal shaft is a rack. You'll notice that the rack has o-rings at each end because it also serves as a piston for the slewing cylinders. The slewing cylinders are single acting (they only push) so only one side is pushing at a time to slew the boom. There is also a thrust bearing using cylindrical rollers to support the weight of the crane arm without adding too much friction to the mechanism. All of the hydraulic lines for the boom cylinders must pass through the center of the pinion gear.

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57241

Maybe decals or mask tape to help your pin stripping. I think that it exists stripping decals
Parma or other.

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57243

blakbird wrote: I'd never build anything quite like this crane before and was not sure what to expect. Part of my trepidation was due to the fact that this is a real hydraulic model, and part was lack of familiarity with the brand. You just never know what to expect from an unknown Chinese brand. Luckily for me, the packaging did a lot to assuage my fears. The kit comes in a very thick box with everything individually packed in foam dividers. Every single part of this is metal: aluminum, steel, or brass.


We'll start with the easy parts: the outriggers. The outriggers on this model are not hydraulically powered. Instead they are manually extended and lowered. Each foot locks into the extended position which makes it possible to support the whole truck. The unit shown is for the rear outriggers which go behind the back bumper. The two extendable arms overlap each other when retracted. There are set screws which poke into a groove in the arms to keep the arms from over extending and falling out, but one of the pre-drilled holes did not line up with the groove so the screw could not be installed. Score -1 for quality on the first step.
The front outriggers which sit right behind the truck cab are completely different. These are 3 stage telescoping units which are very long indeed. Because the arms must sit above the chassis rails, the cylinders for the feet are much longer than those in the rear. The spring that you see on the left is used to hold the foot in the retracted position when driving. The telescoping arms have no such spring though, so they tend to fly out when the truck is cornering. I added some black electrical tape to make them fit more tightly and stay in place.
Now we'll start working on the actual mechanical bits. Shown on the left are the parts for the turntable. The vertical shaft serves as a pinion gear and the horizontal shaft is a rack. You'll notice that the rack has o-rings at each end because it also serves as a piston for the slewing cylinders. The slewing cylinders are single acting (they only push) so only one side is pushing at a time to slew the boom. There is also a thrust bearing using cylindrical rollers to support the weight of the crane arm without adding too much friction to the mechanism. All of the hydraulic lines for the boom cylinders must pass through the center of the pinion gear.

Awesome parts.

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57244

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Shown on the left are the parts for the lower boom arm. The main structure is a sheet of thick aluminum bent into a C-channel. A series of 4 stiffeners are bolted to the side. Not all of the holes lined up properly so it was a challenge to install some of the tiny cap screws. The openings on the sides of the arm are not strictly necessary, but they do provide some visibility of the tubes that will be routed here later.
Here the lower arm has been attached to the turntable with 4 screws. This arm only rotates, it does not pivot.
On the left are the parts for the main moving boom. Again we have a C-channel main structure and bolted stiffeners. The brass pin serves as the pivot axis. The second arm has been attached to the first on the right. It's starting to get heavy.
The third arm is sometimes called the knuckle boom because it folds somewhat like a finger. In order for this arm to overlap the others it must be offset to the side. Putting one arm in a different plane causes a lot of stress so this joint has to be strong. The heavy machined aluminum fitting you see here serves are the knuckle. The dogbone links will guide the lift cylinders.
The third arm is a closed box section with no obvious seams so I assume it is extruded rather than formed. I slides over the end of the knuckle and then bolts in place.

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57246

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The final arm is a 4-stage telescoping boom, so that means three other box channels must slide inside the first. The sliding channels are all black. The first two stages are hydraulically extended by the long thin rams shown on the right. They are plumbed together back to back so they both extend or retract together. Their fixed ends are mounted to the first moving boom stage which means the whole cylinder moves outward as the boom extends. The third stage can be extended manually (not pictured) by loosening a set screw. It must be manually stowed again before the crane can be folded. This last section is seldom used, but allows for extreme reach when needed. The hook on the end is totally unpowered and can swivel on two axes.
Plumbing those telescoping cylinders together is no small feat. In fact, the whole process of installing the tubing was a royal pain in the butt. The tubing is quite stiff and the inner diameter is smaller than the fittings so you must stretch the hose over the fitting. Beyond that obvious difficulty, the fittings are tiny and very difficult to hold without using a tool that may damage them. There was much cursing and injury before I arrived at the photo on the left. Because the telescoping cylinders are plumbed in parallel, the extension and retraction lines each need to split in two before going into the actuators, and there must be enough extra length to allow the whole lot to extend with the boom without binding. On the right I've done the same for the folding cylinder and the lifting cylinder. These were somewhat easier to plumb but by the time all 6 hoses get routed through the turntable things are getting a bit confusing.
At the time I built this crane I didn't have any truck on which to install it yet but I really wanted to do a functional test so I just mounted it to a block of wood. Since the weight can be supported by the outriggers anyway, this worked just fine as a test platform. Here I've mounted the crane and outriggers but none of the hydraulic system has been installed yet.

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Blakbird's 56325 MAN TGX 26.540 Build 1 week 4 days ago #57248

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The control valve / distribution block is a thick slab of steel made up of multiple layers with 4 proportional valves and mini servos. The servos came with the kit which is good because it guarantees they will fit properly. This block has 8 outputs: one each for retraction and extension for 4 channels. There are 3 additional connections. One is the high pressure input from the pump which runs straight through to the other side and through a pressure relief valve. This adjustable valve controls the maximum pressure in the system. Too low and you won't have enough power to lift anything. Too high and you'll blow off connections. The presence of the relief valve allows the pump to run continuously even when no flow is needed because it just flows through the relief valve. The downside to this is that is churns up the fluid and you get a lot of foam. The last connection is return pressure which runs back to the reservoir. The reservoir is disguised as a fuel tank so looks great on the side of a truck. The pump runs off a dedicated brushless outrunner motor with its own 60A ESC.
Success! After troubleshooting plenty of leaks and wasting almost a liter of oil, I have a working hydraulic crane mounted to a block of wood. It has a surprisingly large capacity to lift weight even at full boom extension.
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