Jennifer Clark's Demag AC-50 Crane

[Blakbird]

Many users of this forum, myself included, can count the models of Jennifer Clark as among those that inspired their interest in Technic as a hobby. Her models are so accurate and so dense with function and structure that they are very difficult to reproduce, though many have tried and even more have dreamed of doing so. Over the past couple of years, instructions for her JCB JS220 Excavator and her New Holland LS160 Skid Steer Loader have become available, finally making it possible to reproduce these legendary models. But the largest of her models, the Demag AC-50 All Terrain Crane, has remained elusive.

The reasons for the difficulty in reproducing this model are many and various, but chief among them are:

• No complete set of LDraw data was ever available.
• Jennifer used a pair of 4 channel R/C receivers from Hi-Technic that were never commercially available.
• Jennifer used custom lead screws and thrust bearings for the main boom lift and telescope.

Still, there has been enough interest in the model that attempts have been made. At one point, I downloaded the LDraw files which were available and attempted to fill in the gaps, but quickly realized the project would require more time and effort than I could afford to spend. Although her web site describes each of the model's many functions and even diagrams them, incorporating them into the available space in the same way she did would have required a lot of guesswork even if the custom solutions she used were available. The first attempt which I felt could be considered successful was completed by Richard Brown of the UK who had his own custom lead-screw actuator machined. He also fleshed out the gaps in the CAD file and, crucially, decided to use Power Functions I/R receivers.

We were all very impressed. Richard had to make a number of compromises to fit everything in including adding an area behind the cab. But even at this point the model could really not be reproduced by anyone else without access to a machine shop. Enter Chase Horman whose devotion to this model can only reasonably be called "obsession". Chase's goal was nothing short of complete instructions for the masses: a lofty goal indeed. Furthermore, he wanted the model to adhere as closely to Jennifer's original aesthetic as possible. He had the idea to use a commercially available linear actuator from Firgelli for luffing the boom. This offered several advantages:

• It is available for purchase
• It has a long stroke perfectly suited to the model's range of motion
• It has an integral motor which connects via a NXT connector so does not require a separate gear train.

This actuator replaced a lead screw and 9V motor. The other lead screw which had previously been used to telescope the boom was replaced by a worm screw and 32L axle along with a clever solution which makes the 2nd stage a little smaller than the opening in the 1st stage so it moves smoothly. Last, but surely not least, the 4 PF I/R receivers had to be integrated in a way that didn't change the external profile. If you know how dense the model is, you know that this is no small feat. However, with perseverance Chase eventually achieved his goal and built the model in real bricks and everything worked! He promptly sent me the LDraw file and asked what it would take to do instructions. I took one look at it and told him it would be almost impossible. The amount of deductive reasoning involved in figuring out a build order that anyone could replicate was the first hurdle, but worst of all was the miles of 4-conductor PF wiring that there was no room for. I had several other instructions projects on my plate so am ashamed to admit that I shelved the whole thing for about a year, only spending enough time to produce a render.

But the thought of this model never left my mind, so with enough time (and prodding from Chase) I finally started work on instructions. I think I spent 3 or 4 months coming up with a build order and making the necessary changes to the file. Then it finally came time to build it. This model has about 3000 parts which look like this when split into carrier and superstructure:

    

After much building, reworking, instruction editing, and building again, I finally finished it!

    

Final features are as follows:

• 7-9V motors
• 4-PF IR Receivers
• 1 set of PF LED lights
• 3-9V battery boxes
• 2-rear axles motorized with a pair of 9V motors
• Middle axle independently suspended with rubber bands
• Front axle pendular with motorized steering
• 4-Motorized, self-synchronizing outriggers
• Motorized boom luffing with Firgelli actuator
• Motorized boom extension (2 stage)
• Motorized cable drum
• Motorized 360 degree slew

Finally, I am happy to announce that instructions are in the final phase of checking and will be available shortly. In the interim, I can try to answer any questions about the model.

[Milan]

Ahh, the mighty AC50 from Jennifer Clark! That model made me back to LEGO after many years, and I thanked her for that before!

In fact, I am building ultimate mobile crane in honor of this machine.

I think I have very good and detailed model of her crane in my head, thats how much I analyzed her site and this model!

Her was the first builder to make the boom so realistic with curved bricks.

Shame that there are no suitable door, she had to cut her doors to get that lines in the cabin, she used non-lego parts, but this machine will be forever in my heart, as THE model that made me to come back! Thanks again for that!

[Alasdair Ryan]

It is really nice to see this model made in cad and good quality instructions made for it.

Roughly how much does it cost to build from scratch and are the instructions going to be more than £20?

It is a shame that the boom lift ram is not a 'Lego' solution.

Edited May 19, 2014 by Alasdair Ryan

[Milan]

LAs are not in the scale for this boom, brick built actuator would be to big, those Firgelli actuators are nice, but very expensive and as you said non-lego, but there has to be compromises. I would like more that his crane has lego LA, though.

Edited May 19, 2014 by Milan

[Alasdair Ryan]

LAs are not in the scale for this boom, brick built actuator would be to big, those Firgelli actuators are nice, but very expensive and as you said non-lego, but there has to be compromises. I would like it more if this crane has a lego LA, though.

True,I look at it and it makes me want to build and mod it....

[Blakbird]

Roughly how much does it cost to build from scratch and are the instructions going to be more than £20?

Building from scratch is hard to answer. Obviously, the 7-9V motors, the 4 IR receivers, and the Firgelli actuator alone all add up to a lot. According to Brickstore, about $700 USD at average BL prices. I don't know how much the instructions will cost, but it will be less than that. These will be billed as "for advanced builders only" because honestly there was no way I could show every wire and get every part added in the perfect order without making it 2000 pages. But it should be perfectly buildable for anyone with Technic experience.

It is a shame that the boom lift ram is not a 'Lego' solution.

Indeed, but the PF linear actuators are just way too short and weak for this kind of application. In order to replicate the stroke and power of the firgelli, you would have to use 6 PF actuators (3 series in parallel) which would look terrible. Pneumatics are right out. Since Jennifer's receivers were from Hi-Technic, I don't see this as much different. In fact, it is very common in the Mindstorms world to use aftermarket Hi-Technic sensors, for example. At least the actuator is made specifically for LEGO integration. I was dubious about it as well, but I can't argue with how well it works.

LAs are not in the scale for this boom, brick built actuator would be to big, those Firgelli actuators are nice, but very expensive and as you said non-lego, but there has to be compromises.

Considering the actuator replaces both a LA and a motor, the price is not so bad. They are also much less wobbly than PF LA's. After the 8043 redesign, the LA's have a lot of internal clearance that makes them bend a lot in the middle.

True,I look at it and it makes me want to build and mod it....

Seeing mods to make it even better would be awesome.

[Alasdair Ryan]

How heavy is the boom?

And is there any way to for me to purchase a rough cad file?

Edited May 19, 2014 by Alasdair Ryan

[Milan]

Considering the actuator replaces both a LA and a motor, the price is not so bad. They are also much less wobbly than PF LA's. After the 8043 redesign, the LA's have a lot of internal clearance that makes them bend a lot in the middle.

I know, Firgellis are great, I wanted to use them for outriggers legs (short versions of firgelli). But four of them would set me back a lot of money. If only they were a bit cheaper.

[Blakbird]

I know, Firgellis are great, I wanted to use them for outriggers legs (short versions of firgelli). But four of them would set me back a lot of money. If only they were a bit cheaper.

I think the expense is partially related to the fact that these are really servo actuators with internal position sensors for use with robots, but we just use them in "dumb" mode with no feedback.

At the moment, Firgelli has the NXT compatible actuators on sale to be replaced with the EV3 compatible units. For those of us using them with PF, there is no difference.

[Rishab N]

It's great this amazing model finally has instructions! That acuator is pretty expensive though

[nychase]

It's great this amazing model finally has instructions! That acuator is pretty expensive though

Its actually not that expensive if you think about it.

The cost for a 9V motor is 20 bucks and the cost for at least 4 actuators at 6 each would be another 24. So comparing 50 to 44 its pretty reasonable considering this has the stroke and look the was trying to be achieved.

The model is everything and more you could ever want in a lego model.

The hardest part about the redesign of the model was keeping my mouth shut for the last year!!

[okiba75]

It must have been very difficult to keep this under your collective hats :) I'm amazed at the size and level of detail of this one - I've not generally been a fan of the construction genre but the realism of this one calls out to me.

Great work by Blakbird & NYChase! :D

[Rijkvv]

The (instructions for the) models from Jennifer will make me bankrupt... these models are too awesome not to build and even if I'm not sure if I will build it (haven't build the Skid Steer loader so far) I have to get the instructions.

I consider myself a purist, but I think I can make an exception here. Some parts are simply to complete Lego, not to replace it. The same goes for the BBB train wheels for example.

[Jim]

Great effort

I have frontpaged it.

[Philo]

Excellent! I guess you found my LDraw model of Firgelli's LA? ;)

At the moment, Firgelli has the NXT compatible actuators on sale to be replaced with the EV3 compatible units.

I'd be happy to know the difference between NXT and EV3 version!?

Edit: maybe the auto-id resistor allowing EV3 software to identify properly the device used. I have to test this...

Edited May 20, 2014 by Philo

[Legogal]

This crane looks just lovely, and I have seen a lot of cranes in real life. (My dad used them in moving gigantic pieces of equipment all over the world.) The level of detail is beyond comprehension.

It is fantastic that plans are now available. Thanks for investing so much time to do this!

Does anyone know if there is anything like this crane in the Miniland at Billund? Or the other Parks? I can't remember exactly where I have seen cranes in the six Minilands, but do have photos of most of them taken during the last year. And the cranes I remember were mostly in port settings. So maybe Amsterdam, Copenhagen, or one of the other coastal builds? I regret that Dad passed away about ten years ago and cannot enjoy seeing this model. We visited many heavy equipment yards all over when he travelled with me.

Is the original model on display somewhere?

Edited May 20, 2014 by Legogal

[Kumbbl]

Final features are as follows:

• Middle axle independently suspended with rubber bands
  
• 4-Motorized, self-synchronizing outriggers
  

I have two questions:

1. Jennifer describes on her webpage a quite nifty combined suspension of the second and third axle. You just mention the middle axle as suspended. Does this mean the third axle has no suspension?

2. What does the Term self synchronized mean concerning the outriggers?

Thanks for this Hard work to blakbird and nychase!

@nychase: why do you rank this crane above some other very impressing cranes which have recently shown here some month ago? What is the real special about it?

Thank you also to Jennifer designing this beauty!

[Milan]

I have two questions:

1. Jennifer describes on her webpage a quite nifty combined suspension of the second and third axle. You just mention the middle axle as suspended. Does this mean the third axle has no suspension?

2. What does the Term self synchronized mean concerning the outriggers?

1. Yes, third axle is fixed. Since front and middle axles has suspension, crane would not have enough stability without fixed axle.

2. It means that all four outriggers are driven from one motor. BUT, motor is in the middle, and it drives two rubber bands, each for its side of the outriggers. And each side of the outriggers is synchronized, meaning that they will deploy at the same time, AND they are connected by rubber bands, so if in some case one side is not fully extended compared to another, they will get back in sync after the motor gets them in extreme position, either all the way up or down.

Edited May 20, 2014 by Milan

[Kumbbl]

Thanks for clarification! But One qestion to 1: am i right that the original crane of Jennifer has suspension on all three axles? Or have i misonterpreted the description and pictures on her website?

To the ranking: why does you rank this crane higher as e. G. That One of pipasseyoyo: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=535367

[Milan]

Thanks for clarification! But One qestion to 1: am i right that the original crane of Jennifer has suspension on all three axles? Or have i misonterpreted the description and pictures on her website?

To the ranking: why does you rank this crane higher as e. G. That One of pipasseyoyo: http://www.brickshel...ry.cgi?f=535367

No, original crane of her has suspension just on front and middle axle. Front axle is pendular type, and middle one is independed type (I am amazed how much i remembered from her site and crane )

For the ranking, I would say that there are probably better cranes than this, but many people were very influenced by her work. This crane was very ahead of its time, and it looks and performs in a very realistic manner.

[nychase]

@nychase: why do you rank this crane above some other very impressing cranes which have recently shown here some month ago? What is the real special about it?

I have built many cranes and seen many more. Its hard to explain but you have never witnessed something as dense as this model while still performing every function it was designed to perform within the scaled load capacities. It truly is a stunning model to see and to play with.

Jennifer made compromises on her original build which involved gluing parts and using metal parts to accomplish what she wanted. I was able to remove all of that leaving only the firgelli actuator as the only remaining non-lego part. And lets be honest, its specifically made for lego. I'm most proud of the conversion for the boom to all lego but in fairness the most critical part was the 3L U-joints which Jennifer didn't have access to when she built the model.

@Philo, YES, thank you for those. I had asked you about them over a year ago when I set out to modify the CAD to match my version and luckily you had them done already.

Eric didn't give himself enough credit in all of this. Along with making the instructions he was the one to put the final fit and finish on the model making all the little things work. I've seen the instructions and it should be easy to follow with how he documented everything.

With the Firgelli, if you order it make sure you ask for your gears to be swapped to the 33lb version (you can just write it in the notes to Ian). This gear set is more easily able to handle the load of the Demag without backdriving. A few months ago I was talking in a thread and mentioned a "special project" and this is what it was.

If anyone is wondering, I do not actually have the crane anymore, it was sent to Eric to help expedite his building of it. I already collected the parts to build an upcoming "mammoet" version in black and red livery (not positive if instructions will be released but they should be).

[ritztoys]

Howdy Fellow Builders

When I saw this posting, I jumped for joy, I couldn't believe that this fantastic creation by Jennifer Clark will now have BI.

I reverse engineered this model years ago, I think its' been in the 'box' for eleven years May I present mine ( not completely finished ).......................

As you can see I almost finished ( I'll need to clean off the dust too ) except the boom actuator for 'crowding' and the boom lift, now with new inspiration I'll finish this someday soon. :wub: :thumbup:

Edited May 20, 2014 by ritztoys

[Blakbird]

On 5/20/2014 at 1:42 AM, Richie said:

The (instructions for the) models from Jennifer will make me bankrupt..

Hopefully it's not the instructions that will bankrupt you, it's the parts!

On 5/20/2014 at 4:31 AM, Philo said:

Excellent! I guess you found my LDraw model of Firgelli's LA? ;)

I'd be happy to know the difference between NXT and EV3 version!?

Sorry for forgetting to acknowledge your contribution. Yes, it is true that Philo modeled the Firgelli actuator for us. I now have files for both the long and short version, bot retracted and extended. This was critical for the instructions.

I'm not entirely clear on what the difference is between the old and new actuators. I am led to believe that the new ones will work with both NXT and EV3, but the old ones only work with NXT. If you are just using 9V, then either works the same.

On 5/20/2014 at 8:27 AM, Kumbbl said:

1. Jennifer describes on her webpage a quite nifty combined suspension of the second and third axle. You just mention the middle axle as suspended. Does this mean the third axle has no suspension?

The rear axle was never suspended on Jennifer's model. Nothing has been changed here. Keep in mind that only 2 of 3 axles need to be suspended to keep all wheels on uneven ground.

Quote

2. What does the Term self synchronized mean concerning the outriggers?

Looks like this has already been answered, but I'll repeat it for clarity. Each side of the crane has outriggers geared together, so they are mechanically synchronized. Each side is driven off the same motor in parallel. Since the drive line includes belts, slippage is possible which will compensate for one side reaching end of travel before the other.

Quote

@nychase: why do you rank this crane above some other very impressing cranes which have recently shown here some month ago? What is the real special about it?

On 5/20/2014 at 8:44 AM, Kumbbl said:

To the ranking: why does you rank this crane higher as e. G. That One of pipasseyoyo: http://www.brickshel...ry.cgi?f=535367

It is hard to explain what makes this so great. I loved the model for years but did not fully appreciate it until I built it. The crane you linked is also marvelous, but for sheer realism a System shell over a Technic frame will always look more accurate and allow more detail to be captured. By way of explaining what makes this so great, maybe this will help.

[Alasdair Ryan]

I think I have found a way to add another boom section by using brackets,this would still keep the boom the same size.

I have a idea for the boom raising too but this requires testing.

[Blakbird]

I think I have found a way to add another boom section by using brackets,this would still keep the boom the same size.

I have a idea for the boom raising too but this requires testing.

I hope you succeed. One disadvantage to System building is that all that solid space is really heavy. This model weighs a ton. Raising the boom is challenging due to the weight and the small mechanical advantage at near horizontal. I look forward to seeing your solution.