[REVIEW] 8043 - Excavator

[Milan]

tomacwhite said...

Slewing

Incredibly slow and a loud draining sound from the motor as it struggles to rotate. Movement is slow

Left track

Works OK

Right track

Incredibly slow and laggy, with a draining sound from the motor

Main arm (dual actuators)

Raising: So slow it virtually doesn't move. You have to help it with your hand, then it works perfectly.

Lowering: Works OK

Central arm

Raising: Again, incredibly slow with a loud draining noise coming from the motor as it struggles to lift the arm

Lowering: OK

Bucket

Fine in both directions

I built the same size excavator, with same, M motor powering this function, and it works flawlesly, It has enough power to push or pull the entire 3kg excavator on a kitchen table.

M Motor is connected directly to the LA, it doesn't have any gears between them, so maybe there could be a problem.

Also important, I am using new 7.2V 8878 battery.

For the main arm, again direct connection between 2 Ms and 2 LAs, and I guess it works perfect..it can lift 430gr leather slipper (then M's started to slow down a bit) and on a half way starts tipping the whole body over.

Ok...I am using 2 Ms, instead of one, but my arm is much heavier, and it can lift good amount of weight.

Just trying to help comparing these two similar excavators.

Edited August 11, 2010 by Milan

[Jetro]

Did you guys think of changing the both 20 tooth idle gears, so they face the same direction? Right now when the LA's rotate through the idle gear's axle, one LA slightly shifts one way, and the other reverse way, because the 20 tooth idle gears are not facing same direction. This amy cause the LA's to lock up...Try moving one idle gear in the contr position, so they both face same direction.

It has been brought up: http://www.eurobricks.com/forum/index.php?showtopic=43895&view=findpost&p=789069 but doesn't seem to be the definitive solution.

[jason-l]

For those folks who have already built their own Lego 8043 Motorized Excavator:

How does your own 8043 perform (and sound) relative to ssugawara1955's in this YouTube video? There doesn't APPEAR to be anything wrong with that one:

Much faster main arm operation than my now-disassembled Excavator (enjoying the B-model at them moment). Mine could barely move if the arm was fully extended and horizontal, thus applying maximum leverage. I also had slewing to the right due to extra friction on the right tracks' drive path.

But... one of the reasons for dismantling was to take on the rewarding challenge of ironing-out these issues when rebuilding I agree with others' comments that it's much more than a shelf ornament. It would be boring for AFOLs if it worked too easily, and the complexity of the gearbox is wonderfully complex and satisfying to understand

[Jonas83]

Hello!

I am new to this site and have just build the Lego 8043 excavator, and unfortunately mine is suffering from the exact same problems as described here.

I have build many Technic sets over time and this is by far the most troublesome.

This was not to be expected and is very dissapointing by Lego.

The problems with mine are:

Main boom arm:

Mine can almost not move up or even down at all, the motor barely rotates and is clearly overloaded.

I have checked that the double actuaters are aligned and also tried realigning them, but with no change.

Clutch switching function:

works very bad too. The motor has big trouble switching the cluthes and i often have to push the lever manually before it engages them.

Right track:

moves very slow and struggles compared to the left one that works ok.

Middle boom arm:

Moves acceptable but struggles alot when moving to upper position.

Bucket:

Works fine both up and down.

Slewing:

Rotates really well and effortless.

Fresh alkaline batteries was used.

I have sent a complaint to Lego customer service but i have not heard from them yet.

[Conchas]

David sent me a mail that raised my attention to this topic, so I'd like to make a few comments.

At this point I'm still not convinced this is a topic for Costumer Service or even requiring the Technic Designers attention.

It looks we are simply at the limits of what can be built with ABS elements and driven by 11N.cm 9V motors.

I might test again my Excavator this night, when getting back at home.

When I first built it for the review at TBs it worked smoothly, despite it became more than evident that the boom raises quite slowly.

I was not surprised as the torque is quite high for a M-motor. Furthermore it has so many gearing in front of it...

As I've always tested my 8043 with rechargeable batteries, I imagined it would perform better with fresh Alkalines. Will test it now with the 9V regulator to see whether it improves or not.

As for the Linear Actuators and the ABS wearing into dust, I don't think it applies in this case with ease.

As you may see here, The LA internals are made of a metallic screw spinning inside a Teflon white part. These should not wear that easy. The screw is also quite short to minimize friction.

Linear Actuators are not supplied with any kind of lubricant, and I won't recommend to lubricate yours either.

Eventual small misalignments of the LAs as discussed previously, should not increase stress noticeably also.

Whether the excavator arm is fully open or retracted will certainly also make some difference, as the torque or force over the boom LAs, should change noticeably.

So IMO it is expectable the boom to raise slowly, which shouldn't be much different from a real excavator.

However if some are experiencing extreme issues like those reported by tomacwhite, it would be interesting to see them documented into a video, just to see how different they are from others experience.

Also I have the idea that with Alkaline or Rechargeable batteries, this model drains batteries quite fast. So the performance should decrease also fast.

When playing with mine, I had always to frequently replace the batteries (rechargeable ones) by another fully charged set.

Another thing that came to my mind is a problem I also experienced when building my model and which I've described here.

I had plenty of problems with the switching mechanism, till I found that it was probably related with an under-rated M-motor supplied with my unit. Replaced it and finally everything went fine.

Wonder if this couldn't be also the problem of tomacwhite ???

As I said before, later today I'll try some different power sources and do some voltage and current measurements to see if I could get into some further conclusions.

[rgbrown]

An idea: I'm not at home this month, so I can't test it, but it would be relatively easy to devise a test system to see whether linear actuators are deteriorating (or variable in performance). The idea is to apply a constant load and constant torque to the actuator and then to time how long it takes to extend or retract. Constant torque can be provided by coiling a string around a wheel-hub.

If the theory that the LAs are deteriorating is correct, the extend/retract time should be longer for a used one than for a new one. I don't know off-hand how big the weights should be, but it should be pretty easy to sort it out by experimentation.

Alternatively you could measure the torque required to make the LA move, and compare.

I've attached a picture of how you might do it to measure the retract time. You'd need to change the LA orientation to upwards to measure extension time.

Edited August 11, 2010 by rgbrown

[Jetro]

I had plenty of problems with the switching mechanism, till I found that it was probably related with an under-rated M-motor supplied with my unit. Replaced it and finally everything went fine.

Are you saying you had a 'broken' motor?

[tomacwhite]

It's great to have lots of feedback here, thank you guys.

I will take a short video of my model tonight and post it onto Youtube (and the link here of course). It will be probably be done on my iPhone 3GS so wont be amazing quality, but will at least show what problems my model has.

I'll do it for later tonight (UK time).

Also, if you had a defected motor, perhaps I have problems with mine too. However the "Main Arm" motor spins freely when there is no linear actuator attached to it.

Edited August 11, 2010 by tomacwhite

[Blakbird]

It kind of works. It stabilizes the the whole arm a bit. Raising the arm goes quite a bit faster! Even on batteriers that are not fresh!

Fun detail: By adding these rubber bands (Which are actually pulling back the arm.)lowering the arm goes a lot faster.

This is a cool idea which I like very much. By taking some of the load off the actuators, we can solve most of the problem. As you can see in the previously posted picture from 8851 in Technicopedia, the black rubber bands deteriorate and crack if left extended over a long period of time. However the silicon bands in this picture do not have that problem. By the way, nice job picking colored bands that match.

Another tact to take on this same potential fix is to use one (or two) of the long stroke (10.5L) shock absorbers instead of rubber bands. If a little mechanism was employed to have them help lift the boom while still staying within the limits of their stroke, I think that could be a big help.

In this picture, you can see a black bushing in between the two linear actuators. A shock absorber could be put in here and attached to a different point on the boom to help push it up. It would not be a huge change in lift, but it may not take much to make a big difference.

[JunkstyleGio]

@ Conchas:

Thanks for your lengthy reply.

Building a big and complex model like the 8043 is a hard job. With so many parts that need to be placed just right and running freely a building mistake by the builder has major consequences. Testing the model on and on during the building-process is not only evident but highly recommended.

For me most of the problems are solved now to my satisfaction.

* Allingment of the 2 LA's in the arm is good now. With the two free-running-gears in the same position the tension on the LA's is almost gone.

* Lowering and lifting speed is acceptable now.

* Jimmy's rubberband sollution is working for me. The model keeps running at acceptable speed. Even with highly-worn batteries.

* One should realise that no PF-motor is exactly the same and so some minor speed differences can hapen.

* The turntable-effect is a known and almost unsolvable problem, so i can live with it!

Again.

This IS the best looking and complex Technic model TLC has ever designed! And i'm one of the satisfied and proud owners.

[CP5670]

Some great observations here. It does seem that the LAs have a lot of additional friction when they move under load, even if the load is fairly moderate. I've noticed the same thing on the 8265 Front Loader. As for the LAs wearing out with use, they have been around for a while now, so I would think someone would have noticed it earlier if it was a big problem. If the issue is simply that the motors are not powerful enough, they just need more gear reduction, although it may be difficult to find a place to fit that into the model.

You connect one of these train regulators (which outputs 9V at a good current) to one of these PF extension wires which lets you connect it to the old 9V system. Sadly, this requires you to tether the excavator to a wire.

I end up doing this with most of my models. The wire is a bit inconvenient but it's better than dealing with the inconsistent voltage outputs you tend to get with batteries.

[Conchas]

Are you saying you had a 'broken' motor?

Not totally broken, but at least it is sub-performant.

As result it was not suitable for the function and I had to exchange it with one of the other motors. Hopefully it didn't end driving the boom... Something that I'll check also later.

...Meanwhile my wife arranged for a dinner outside, so lets see if can still do it today.

[shimon]

just got mine today and built it..

the turntable works great for me but the right track is very weak and both actuators aren't doing a good job either

i thought of some solutions: as mentioned before there needs to be a counter weight to help get the arm up and i just thought of a possibility to put the battery box behind the arm (i tried lifting the model up to 90 degrees and the function works perfectly raises\lowers

and also in the place of the battery box we may come up with sariel's idea for tracked vehicles : 1 motor make it run\other - steer

so maybe we think somehow to put an XL motor in the place of the battery box and try modify the whole thing to that mechanism it will be hard but that way it will run perfectly + require less gears + be synchronized

what do you think?

Edited August 11, 2010 by shimon

[Alasdair Ryan]

it seems that this excavator has its problems as i i am building a custom one of my own i don't think i will rush to buy it

Edited August 11, 2010 by Alasdair Ryan

[tomacwhite]

Just uploading the video to You Tube now. Wont be long :)

[Fyredog]

Mine works fine - although Mine is all direct drive not through a bunch of shared gears: My TLG 8043 seems to work fine, in fact I really haven't had too many problems with it

[tomacwhite]

OK video is now online. It's available here:

[Fyredog]

And those are fresh batteries? what kind ? I just pulled my TLG 8043 out and has the original batteries in it and has been played with by kids and adults, and still works good. My red 8043 uses the smaller rechargeable, and shows no sign of difficulty.

[tomacwhite]

Yep out of the packet AA Everyready Energizers.

[Jurgen Krooshoop]

OK video is now online. It's available here:

Yours doesn't seem to work as well as mine. And I'm using the 8878 rechargeable battery wchich gives only 7,4 V instead of 9 V.

Edited August 12, 2010 by Jurgen Krooshoop

[jason-l]

OK video is now online. It's available here:

Yours works noticeably BETTER than mine did with brand new Duracell Ultras. I'm sorry I didn't video it before disassembly now. The main arm on mine would barely lift from horizontal with the arm fully extended, applying max leverage. I was unhappy with the straining of the motor. I also noticed your gear change is very crisp and fully engages. Mine often needed 2 or 3 attempts to get full travel thus fully engaging the clutches. Wondering now if I have a batch of sub-standard motors?

As always, I was very careful during the build to ensure all gears turned freely/loosely on their axles.

[Jurgen Krooshoop]

Yours works noticeably BETTER than mine did with brand new Duracell Ultras. I'm sorry I didn't video it before disassembly now. The main arm on mine would barely lift from horizontal with the arm fully extended, applying max leverage. I was unhappy with the straining of the motor. I also noticed your gear change is very crisp and fully engages. Mine often needed 2 or 3 attempts to get full travel thus fully engaging the clutches. Wondering now if I have a batch of sub-standard motors?

As always, I was very careful during the build to ensure all gears turned freely/loosely on their axles.

You can improve the switching by changing the gears. See the video in post above for the details and read here.

[Marckeyh]

You can improve the switching by changing the gears. See the video in post above for the details and read here.

Shame about some models that don't work as intended. Nobody should be making any alterations, it should work 100% fine for everyone!

Does TLG ever revise a model during its production, anyone know?

[jason-l]

You can improve the switching by changing the gears. See the video in post above for the details and read here.

Thank you, Jurgen. I read your new thread after I posted. I will be improving the mechanical advantage as you suggest when I rebuild

[Blakbird]

Shame about some models that don't work as intended. Nobody should be making any alterations, it should work 100% fine for everyone!

Does TLG ever revise a model during its production, anyone know?

Yes, it has been known to happen. See the page on the old 851 tractor, for example.