Six Axle Lattice Boom Truck Crane

[Southgate]

Since I'm new here, I'll cut my teeth by posting my project, this scratch built RC crane in 1/25 scale. I hope I'm in the right category, or even the right forum for that matter.

I've been working on this for years, and it has evolved all along. It still is, but I do see light at the end of the tunnel. I'll post this so far and if anyone is interested, I'll add more pix and fill in the story line. Gotta go for now! Dan

 

[Nutter]

Are you kidding me? That thing is incredible, holy cow. Insane build!

 

[Rolex]

That's absolutely beautiful! We'd love more pics and details of the mechanicals.

 

[Tunedfrog]

Very cool, I love it.

 

[cbaker65]

That's an awesome scale build ,you don't see stuff like that ,an yes ,you are very much welcomed here ,great job!....

 

[Southgate]

Welp, You asked! But first a caveat. The crane is no longer as it appears in the picture. Mainly, I'm a scale model truck builder, I started this thing years ago. Working with limited knowledge (still have plenty of that) and resources, I built it around things I could get. As it was almost complete, It came to bother me more and more it was not in scale with the rest of my 1/25 collection of built-ups.

So, a couple years ago, I measured, calculated, sketched, and decided I could bring it into proper proportion. Along the way much of the original components went by the wayside, and the craftsmanship on the replacements was cleaned up considerably. The first go round had a lot of experimentation left in it. Now look at the picture, the little guy standing there?

The bottom of the fender catches him at the lower part of the shoulder instead of over his head, about 14 -15 scale inches. the whole carrier is about 9 scale feet shorter, and about 10 scale inches narrower. All that shrinkage took a TON of work! But I am really happy with the resulting proportions now. It compares favorably with a Link Belt HC 278H and other cranes I drew on for inspiration and reference for mechanical arrangement. The work is cleaner too in areas you have to look deeper to see.

Let me add here, I LOVE the feature on this forum of drag and drop pictures! NICE!!!

Ok now, cover the young'ns eyes, we're gonna look at nekked pictures.

You can see that space is crowded under the hood. This is the right side. the left also has 3 motors. Each drum has two motor-gearheads with the shafts pointing toward each other, bound to a center hub inside the drum. Let me get another picture up...

Good. I used Tazer reversible ESCs for the 3 drum-gearheads, they work great, Later I discovered Bane-Bots ESCs, smaller, cheaper work great too. (The little yellow deally there). It runs a drum, I then put the other Tazer to an electromagnet I can use to lift any ferrous materials.
I'm not done here, but I'll post to reduce risk of losing what I have so far... More soon.

 

[Southgate]

Thank you all for your replies! I didn't know if this would be out of place here.

I edited in the correct first photo in the above post.

You can see the top of the 6 channel receiver towards the back in the above post. I had to discect the brand new 8.4v 7 cell battery to get it in there. 6 ride transversely under the machinery. the 7th floats in the rearward portion of the body. Now, the drum motors are one thing;

These are gearheads from China, great little motors. On the right are the originals used for the drums and axle drives (more on that later). They were given to me by a friend who salvaged them from machinery long before I discovered sources on line. They really are too long, But that's what I had. Recently, I swapped out for the ones on the left, making room to narrow things up. They're all low current brushed motors with steel cores, and work well with RC ESCs.

The slewing motors (rotation of the upper unit) are different. The above motors are way too fast. So I used ESCAP motor-gearheads with coreless motors. They have no idea what to do with regular ESC output. In lieu of a suitable ESC, I had to make a servo turned potentiometer and transistor (stolen from an MRC train Controller) to turn them. and a servo-thrown dpdt switch to control direction. I'm still looking for a linear reversible ESC, if they're available to replace all that junk (as posted in electronics forum) BUT, It works well!

The power switch is hidden under the air filter up top. you simply slide it forward to turn on the upper unit.

Still more to come. Again, thank you for the nice words!

 

[Southgate]

I'll finish up the basics of the upper unit here, with a few more facts. It's run with a tactic TTX850 2.4 GHz 8 channel. There is the basic boom setup as seen in the above thread's picture, but there are three 20" extensions, giving it up to 92 inches total length,191 scale feet.
With the shortest configuration, it lifted and rotated 10 pounds once. The booms are brass, the deck 1/2 in aluminum. The motor clamps are oak. The cables are silk fishing thread from the 50s or 60s, found on eBay. Super strong, if it ain't rotton! And it's woven so it doesn't have memory, like monofilaments.

There's a pic before the boom tip "horse head" extension or paint were added.
The body shells are sheet styrene. The

The drums are turned from some aluminum cylinder things I salvaged from a fiberoptics place I used to clean. I was welcome to grab anything they tossed, and a lot of it came in very handy.
The upper unit simply lifts off of the carrier, and I'm building a lowboy trailer to pose it on for "undecked" transport. It's rc system is independent from that on the carrier.

I learned early on in the project I wasn't going to get far without a lathe and vertical mill. I bought Sherline's Model 2000 mill and 4400 lathe. Above is the upper unit deck on the mill. Also very usefull is a Harbor Freight bench top drill press, and the ever handy Dremel motor tool, I like the foot-feed speed controller.

I'll probably find more details to fill in but for now that kinda covers the upper unit. Next, the carrier. Thanks for following. Dan

 

[Southgate]

OK. Home from work, I'll take ya into the carrier. I'm not going to bore you all with the whole process of downsizing this thing, but I will show why I chose to do so. These are the styrene decks, old and new. You can see by the difference in size how out of proportion that big one is to the new, unpainted one. The original cab is used, with some mods. The verdict is still out on the hood (just set on there for now).

Reducing the carriers size does not make the crane any less stable when in operation, because the foot print of the outriggers remains the same with them all extended.

The carrier as it looks now.

It will have diamond plate fenders similar to those on the original.

Guts.

That motor you see is not the drive motor. It is connected to a mechanism that lifts the counterweights into position to set on upper unit. This model is capable of self assembling like a real one. you set the weights on the carrier deck with the crane, actuate the lift, swing the upper into position, and then set the counterweights on their platform. I saw that on a real crane and HAD to make it work!

The ESC runs the six motors that also comprise the axles.

Two motors are stuffed into a bored-to-fit ABS pipe fitting, shaft out. The shaft is clamped into a hub and the rims, again from those aluminum cylinders I scrounged. wired accordingly. Those assemblies are clamped into aluminum rocker arm setups that keep the weight on all 6 axles equally and allow it to take undulations in the ground surface. The gear motor speed is "yard speed", it tops at around 10 mph maybe, but it allows for very slow creeping and positioning very smoothly.

Steering, front suspension: You guys get steering components and angles so I'll let the pix do most the talking here.

The axles and spindles were machined from brass bar, with some pieces turned from round solid brass bar. The suspension subframe is sheet brass. It is a walker beam from front to rear and equalizes over the front and rear axle. The center has enough spring added by those flat leaf springs to keep is planted on the ground. Like the rear, it can take uneven ground. Not like a rough terrain crane, but anything a 6 axle unit should be able to handle. Note in the top picture that the servo box is mounted horizontally, the arm actuates Pittman style. The 3 are linked progressively to maintain pretty close to Ackerman geometry on all 3.

Tires were a major challenge on this downsizing project. The originals were pirated from ERTL Payhauler 350 dump truck kits. 18 tires. They were really too big. Nobody makes the size I needed. I finally decided to use black ABS pipe fittings and 1/4 inch ABS sheet to scratch build them. With some trial and error, well, look: one of the 6 dually sets.

Two tires were turned into each pipe joint together for the rear duals. Later ridges were turned in the tread part to hold rubber treads cut from bicycle inner tubes for traction. You can see that in the front tires in previous pictures. The side walls were made from the sheet abs, and contoured on the lathe before inserting and gluing into the fittings. They were all made to fit the original rims, as they were already how I liked them. that saved a lot of work.

The receiver and 4 of the 7 Nimh batteries, again cut out of a new 8.4, are in that box under the frame. 2 cells are between the two forward-most rear tires, and one is in the fuel tank. Space is at a premium on the carrier too! I have to just gulp and start cutting the battery packs apart. You know what that does to the warranty

I can answer any questions you may have on any of the above if you like. The project still has a way to go, but I'm on the downhill side of it now. Thanks for following. Dan

 

[HPIguy]

That is just incredible!

 

[Rolex]

ABSOLUTELY incredible!

 

[BobP]

Fantastic job.

 

[Nutter]

The engineering involved in this project is mind blowing. Simply incredible build. Way to stick with it, i know this took a long time.

 

[cranemodel1015]

OK. Home from work, I'll take ya into the carrier. I'm not going to bore you all with the whole process of downsizing this thing, but I will show why I chose to do so. These are the styrene decks, old and new. You can see by the difference in size how out of proportion that big one is to the new, unpainted one. The original cab is used, with some mods. The verdict is still out on the hood (just set on there for now).View attachment 121624

Reducing the carriers size does not make the crane any less stable when in operation, because the foot print of the outriggers remains the same with them all extended.

The carrier as it looks now.

View attachment 121625

It will have diamond plate fenders similar to those on the original.

Guts.View attachment 121626

That motor you see is not the drive motor. It is connected to a mechanism that lifts the counterweights into position to set on upper unit. This model is capable of self assembling like a real one. you set the weights on the carrier deck with the crane, actuate the lift, swing the upper into position, and then set the counterweights on their platform. I saw that on a real crane and HAD to make it work!

The ESC runs the six motors that also comprise the axles. View attachment 121627

Two motors are stuffed into a bored-to-fit ABS pipe fitting, shaft out. The shaft is clamped into a hub and the rims, again from those aluminum cylinders I scrounged. wired accordingly. Those assemblies are clamped into aluminum rocker arm setups that keep the weight on all 6 axles equally and allow it to take undulations in the ground surface. The gear motor speed is "yard speed", it tops at around 10 mph maybe, but it allows for very slow creeping and positioning very smoothly.

Steering, front suspension: You guys get steering components and angles so I'll let the pix do most the talking here.
View attachment 121628




View attachment 121629

View attachment 121630

View attachment 121631

The axles and spindles were machined from brass bar, with some pieces turned from round solid brass bar. The suspension subframe is sheet brass. It is a walker beam from front to rear and equalizes over the front and rear axle. The center has enough spring added by those flat leaf springs to keep is planted on the ground. Like the rear, it can take uneven ground. Not like a rough terrain crane, but anything a 6 axle unit should be able to handle. Note in the top picture that the servo box is mounted horizontally, the arm actuates Pittman style. The 3 are linked progressively to maintain pretty close to Ackerman geometry on all 3.

Tires were a major challenge on this downsizing project. The originals were pirated from ERTL Payhauler 350 dump truck kits. 18 tires. They were really too big. Nobody makes the size I needed. I finally decided to use black ABS pipe fittings and 1/4 inch ABS sheet to scratch build them. With some trial and error, well, look: one of the 6 dually sets.

View attachment 121633


Two tires were turned into each pipe joint together for the rear duals. Later ridges were turned in the tread part to hold rubber treads cut from bicycle inner tubes for traction. You can see that in the front tires in previous pictures. The side walls were made from the sheet abs, and contoured on the lathe before inserting and gluing into the fittings. They were all made to fit the original rims, as they were already how I liked them. that saved a lot of work.

The receiver and 4 of the 7 Nimh batteries, again cut out of a new 8.4, are in that box under the frame. 2 cells are between the two forward-most rear tires, and one is in the fuel tank. Space is at a premium on the carrier too! I have to just gulp and start cutting the battery packs apart. You know what that does to the warranty

I can answer any questions you may have on any of the above if you like. The project still has a way to go, but I'm on the downhill side of it now. Thanks for following. Dan

Southgate,
Very, very awesome attention to detail, resourcefulness AND persistent focus on accuracy. Your creation is absolutely brilliant!

 

[FJC_GUY]

Southgate,
Very, very awesome attention to detail, resourcefulness AND persistent focus on accuracy. Your creation is absolutely brilliant!

Guys like you and @Southgate are out here building childhood dreams. Amazing stuff.

 

[cranemodel1015]

Guys like you and @Southgate are out here building childhood dreams. Amazing stuff.

Thanks FJC_GUY for your encouraging remarks! The Craftsmanship Museum in Carlsbad, CA. just published an article on my build at: https://craftsmanshipmuseum.com/artisan/thomas-garing/
that you might also enjoy.
Have a Great Day!
Tom

 

[FJC_GUY]

Thanks FJC_GUY for your encouraging remarks! The Craftsmanship Museum in Carlsbad, CA. just published an article on my build at: https://craftsmanshipmuseum.com/artisan/thomas-garing/
that you might also enjoy.
Have a Great Day!
Tom

That is awesome! Nice article and also a place I need to visit next time I'm anywhere near Carlsbad CA.

 

[cranemodel1015]

That is awesome! Nice article and also a place I need to visit next time I'm anywhere near Carlsbad CA.

✌

 

[WickedFog]

Amazing work!

 

[Jamr]

Wow, that thing is awesome. Nice work!