Blakbird

Thanks for the link to ditzj.de. I had never seen this site before but it is one of the best truck and crane web sites I have ever seen!

I only partly agree with this. The clip on the driving ring is in bending and therefore has a sustained tensile stress, but this does not necessarily hurt anything. Only if that stress is over a certain threshold will it cause any problem, and without specific material properties it is not possible to predict whether or not there will be long term damage. Calculating the actual bending stress is a fairly trivial matter though.

The 8295 linear actuator is indeed very hard to turn, but part of that is due to the fact that when it has the greatest load to lift (when the arm is all the way down and fully cantilevered), the mechanical advantage of the LA is almost nothing because it is nearly parallel to the boom with only a 1 stud moment arm. The mechanical advantage gets better and the boom goes up, and the load on the LA also goes down at the same time because when the boom is raised, a greater portion of the weight is taken by the pivot axle instead of the LA (the fulcrum).

Chrome plating doesn't add any strength, it is only a wear coating. Chrome is exceptionally brittle, so if put over a ductile material like ABS, nylon, or Teflon, it would simply crack and flake off as the substrate deforms.

I'm very interested to know how they "fixed" the linear actuator. As they stated, there is nothing wrong with it for normal use, but it is not suited for "heavy duty" applications. In this case, there are already 2 actuators in parallel which reduces the load on each, though the load on the motor stays the same. The fact that the blame is being placed on the LAs suggests that they are being "damaged" in some way by repeated use. Who wants to tear one of them apart and see what has happened inside? Since the new actuator will be different in some way, I wonder how LEGO will make it visually distinguishable? We'll need to be able to tell the difference between the old and the new part. Or, like the old 9V actuators, they may just make an improvement and then make all new parts to the new standard. You can tell the difference between old and new with a careful examination, but it is not immediately obvious. I also wonder if they will just send 2 new actuators to lift the boom, or whether they will replace all 4. Finally, what is the actual fix? An all metal internal design would be a huge improvement, though it would probably need to be lubricated on assembly.

If you search this forum for "instructions" you should find several, although Technic MOC instructions are pretty rare. A few I can think of off hand are from myself, Jurgen Krooshoop, and Nico71. There are also quite a few people who take photos of the construction of their MOCs and put them on Brickshelf.

Obviously style is a matter of preference. Great car builders like Arvo and Firas Abu-Jaber use System elements build with studs and then hide the studs with various techniques. Paul uses entirely Technic elements with no studs whatsoever. It is a different building aesthetic, but I personally appreciate it very much. There is no doubt with one glance at this car that it is a 1969 Camaro, and that is an amazing accomplishment with only Technic parts. As for blocky, have you ever seen a real Camaro?

Nico71, if you just provide the MPD file, then people can easily export their own parts list from MLCAD or LDView. That's what I did when I made my copy last year. Another possibility is to import the MPD file into Brickstore. This will give you a parts list which you can turn into a Bricklink wanted list. I've used this method to order parts many times. By the way, this is a really excellent MOC (which is why I decided to build one)! Very well proportioned and functional. Thank you for taking the time to do the detail instructions. Would you care to share your method for making that video? How did you make the model revolve while stepping through the building steps? Did you just do screen captures from LDGLite?

This is similar to the answer I was about to type. The further the actuator is extended, the shorter the couple between the end gland and the thread. In a real actuator, the end gland has hydraulic seals in it and you don't really want those seals supporting much side load or they will wear prematurely. You want the structural members to carry that load as much as practical. The LA doesn't have any seals, and I don't know how tight the gland fit is compared to the threads. In any case, side loading can't be helpful.

One of my daily duties is the structural analysis of threads. It is true that the root of the first thread has the highest stress because 100% of the tension stress is present at that location. However, that does not necessarily mean that the length of the threads does not matter. For a Class 3 thread (very high quality) like I use, a careful analysis will show that the first 5 threads carry all the load. The first thread transfers about 50% of the load and each subsequent thread carries less. Class 3 threads are very expensive so there's no way the LEGO LA's use them. A Class 2 thread has looser tolerances so a greater number of threads MAY carry some load. Of greater importance than the load distribution amongst threads is the behavior due to side loading. The LA force is not purely axial, there is also a side component. A short thread is very inefficient at reacting any side load and results in a very large force couple which tends to jam the thread. Only a perfectly aligned actuator and load will prevent this. For actuators like I work on, we try to make the length of an actuator thread at least as long as the diameter.

Is anybody here competent using SR3D Builder? I have now completed my LDraw file of this model which has all the gears in it. Someone could import it into SR3D and actually virtually try out all the gear systems and see how (and if) they work. I don't know if SR3D support differentials and driving rings yet though. Obviously the people who have built it have pointed out a number of serious flaws, but it would be interesting to see if the gear system at least works kinematically but there is just too much flex and gear skipping in the structure.

This is called double wishbone and uses a 4 bar linkage. Like this: This is called swing arm. Like this: Generally, only front wheel drive cars use Macpherson struts. Lots and lots of cars use double wishbone on the front wheels and many on the rear as well. Most front wheel drive cars with independent suspension use double wishbone on the rear. Older cars and trucks used leaf springs and a live axle. A few muscle cars used a trailing arm on the rear.

If it helps your confidence level, I have had many hundreds of transactions on Bricklink and have never had a single issue. Much better than eBay. LEGO buyers and sellers are generally pretty reliable, and you won't find any other kinds of people on Bricklink.

Good point. He did a huge amount of work on those modification instructions, actually duplicating the entire instruction manual not just the changed portions. Let us know what you find out when you contact him. If you get the file I'd be interested in a copy as well.

Looks very promising! I will certainly build a copy when it is ready, especially if you go to all the trouble of making instructions. Great work as usual Nico71. Yes, I think a new topic for this MOC when it is ready is a great idea. Be sure to tell us how the features work!

One thing I would like to add is that, even though these would be great improvements, Peeron is still an excellent and super useful site. When giving feedback on a web site, I think it is always important to mention the positives and Peeron has a lot of positives. I'm happy that it exists at all, but if somehow these additional features were added then it would be even better.

This is consistent with the whole problem with mechanical linear actuators in the first place. The advantage they have over pneumatics is positive absolute positioning and theoretically greater power output. The disadvantage is that getting power to remote places like a digging arm requires very complicated drive systems. Now personally, I really enjoy the complicated drive systems from a technical perspective, but from a play value perspective, the more parts and distance you add the more possibilities there are for problems. So from an engineering standpoint I call LA's a win, but from a children's toy standpoint I think they have some problems. Of course, some AFOLs have solved this issue by simply attaching an M-motor directly to each LA and only running the wires to a remote location. This works but looks bulky. The even more obvious solution is pneumatics which can be put at any distance from the source! At any rate, I like my 8043 and I'm sure I'll like the fix, whatever it is, even more. I may consider keeping both varieties for posterity depending on how different they are.

Thanks for the reply. From building the LDraw file and staring at all the gears, that's almost exactly the same conclusion I came to about it works. Almost. The pneumatic functions are obvious enough, except the complex geometry of the lift mechanism (which was REALLY hard to get right in MLCAD). There are four driving rings which shift functions simultaneously. When shifted forward, one motor drives all four wheel with 3 differentials: left, right, and center. The other motor steers. One problem I can see with the steering is that the two sides are connected together with angle connectors which are in tension. They can pull apart which makes the steering loose. This could be improved with a rigid link of some kind. In the other mode, it's true that one motor is connected to the left side and one to the right side to drive the wheels. However, from what I can tell, the left and right sides are still connected together. That means you can't really skid steer or you'll get the horrible gear cracking you described. Of course, I could be wrong since I haven't actually built it. The differential between the two sides should allow some range of unequal motion, but the ring gear on the diff will be backdriving the rest of the unpowered gear train if the two sides are not going the same speed. I would also guess that the final stage of bevel gears that goes to the wheels slips a lot. There is nothing really holding this set of gears tight together. In any case, the MOC is brilliant and I think I'll have to try it even if it is not perfect.

I would also like to have such a file, but that's a tall order. 8265 is a big complex model. Sooner or later, someone will make a file, possibly me!

I was browsing the Internet for cool Technic MOCs recently, like I do every day, and I came upon the review of a MOC on SETECHNIC by someone called Five Star Brick. It was a remote controlled pneumatic wheeled excavator with full instructions. Upon some further, I found his Brickshelf page and found that he has full instructions for another model, a remote controlled pneumatic wheeled loader. Not only are the instructions top notch, but the complexity of the models is marvelous. I started building an LDraw file of the wheel loader. You can see an image of the completed gear system below. This thing is awesome! I will be building it soon. The problem is, these instructions were posted in 2005 and the email address in them is no good. Does anyone know who Five Star Brick is? I would like to contact him/her about these models. On a side note, stare at this render and/or the instructions for a while and try to figure out how this thing works. It is a very challenging thought exercise.

If you have an existing 8043, keep it. The few copies out there prior to LEGO's modifications will be collector's items! Also, I don't think cost was the reason for not choosing XL motors. On the LEGO Education site, an M motor is $7.99 and an XL motor is $9.99. The price is not very much more. I would guess that space inside the model was a bigger reason for choosing M motors. I would guess that one of the biggest costs of whatever modification TLG makes will be the instructions. They have very large printed instructions manuals that may end up changing significantly. The cost of printing the instructions is not trivial and the old copies may be useless. If the mods are minor enough, they might be able to just put in a few addendum pages like they've done in the past.

That's an incredible set of modifications. I see that the controller now functions like Jennifer Clark's JCB JS220 excavator (and like the real thing) which makes it a pleasure to operate. Thank you very much for all your work on this.

The friction coefficient (or total tangential behavior, if you prefer) generally increases with temperature. This is why dragsters do a "burnout" to heat their tires prior to a race. Doesn't necessarily matter that the surface is smooth. The surface area of the tire which is in contact with the surface is still varying as the tire rotates, and therefore so is the total possible tangential force. However, since zblj also tried it with smooth tires and got the same result, we can conclude this is not the source of the behavior. Another possibility is a resonant stick/slip condition. Because of the difference between static and dynamic friction coefficients, sticky surfaces tend to "chatter" when you drag them while in contact, bouncing between stopped and moving. When the frequency of the bouncing tire matches the natural vibration frequency of the vehicle, you'd get more consistent contact and better traction. This theory is pretty wacky, but it's a possibility. A Psychologist decides to do an experiment on an engineer and a scientist. He puts them both in a room and places a "prize" at the other end. In the original joke it is a beautiful woman, but to keep on topic we'll say it is a MISB 8868 Airtech Claw Rig. He then says, "If you can calculate the distance to the prize, you may then move half the distance closer to it. Whoever repeats this enough to get to the prize wins it." The engineer immediately builds a ranging device from a paper clip, a laser pointer, and some pocket lint. He calculates the distance to the prize, moves half the distance, and starts repeating. The scientist just stands with his arms crossed and does nothing. This continues for a while until the Psychologist says to the scientist, "Why are you not going for the prize? Is it not appealing to you?" The scientist replies, "It is a wonderful prize. But every good scientist knows that you have provided a halflife equation. The prize will never be reached even with infinite repetitions, so the exercise is useless." "Right", says the engineer, "but I'm going to get close enough for all practical pusposes!" There are 10 kinds of people in the world, those who understand binary and those who don't.

You can only buy it in the Power Functions expansion set which also comes with a bunch of other stuff including an M-motor, LED lights, and a pole reverser. You can get just the battery box from LEGO Education or from Bricklink.

Seems like a good enough plan. Do you intend to just hook up the battery to the +/- battery terminals inside the battery box and still use the same external connection and switch on the battery box? This should work except for the fact that there is no protection circuitry for the Li-Po. Make sure not to run it too low on voltage before recharging or it will explode.