set 8002 "Destroyer Droid" reconstruction

[astyanax]

Set 8002 is from deep in my dark ages (released in 2000), and ever since returning to the hobby, I've wanted to build it -- and understand it's mechanism! Instead of hunting down the original set with possibly degraded elastic bands, I'm attempting to build it from my inventory with simple elastic bands of similar size from my local supermarket.

Since I don't have the parts in the old Brown and Dark Gray colors, I went for the following color conversion:

• Brown -> Red
• Dark Gray -> Black
• Red -> Tan (this color is used only to mark point where to grip the model)

Furthermore the following alternatives appear to work well:

• The flex cables can be replaced by common 22L ziplines
• The soft hoses in the arms can be replaced by soft rubber pneumatic hoses

======

Now, I got one problem. Using common elastic bands, all mechanisms work fine, except the rear leg.

The problem is with the elastic bands highlighted in bright blue in the rendering above. According to the instructions, a generous amount of elastic bands need to be placed here like so:

It is then these elastic bands -- and nothing else -- that should then be capable of lifting up the entire model, while the rear leg folds down, like so:

But the issue is, in my case, these elastic bands are not capable of lifting up the model to fully unfold the rear leg. And I have a hard time understanding how they could ever even do so. In the given position, I don't see how they could exert enough force anyway. Yes I'm trying this on a very smooth surface.

So my question is: Does anyone have experience with this awesome model, and previously encountered & solved the issue of the rear leg failing to make the model stand up?

[Jeroen Ottens]

I was there when it was designed. You have fold the arms and legs inwards and then roll the machine over the floor.

Once it is upside down the pin on top is pressed inwards and that triggers the unfolding of the arms and legs.

The inertia helps to unfold the rear leg. But, TBH, it was a fickle mechanism.

Fun fact: At the time we had modded versions at the design department that used springloaded shooters in the arms that were activated when the arms swung outwards. 

[Toastie]

32 minutes ago, astyanax said:

And I have a hard time understanding how they could ever even do so. In the given position, I don't see how they could exert enough force anyway. Yes I'm trying this on a very smooth surface.

Did you see this video? OK, it is in German but is fun to watch:

Now, this is also one of my ever "wanted" sets - I just recovered from my dark ages back then ... and I just learnt about the Technic series. And I certainly don't want to spend any stupid prices, given that almost all pieces are still available today. Colors mean not much to me; I bet they have painted them in every conceivable color, as the Empire had many planets to dwarf. Dune for example would favorably be worked on in camouflage other than that old dark gray

35 minutes ago, astyanax said:

I'm attempting to build it from my inventory with simple elastic bands of similar size from my local supermarket.

This is so cool ...

Good luck!!!

All the best,
Thorsten

[2GodBDGlory]

I was reading about this set on Technicopedia yesterday, and decided I wanted to try building it too! The rubber bands do sound frustrating, though.

[Gray Gear]

I have thought about building this Droid with new bricks myself. It just seems like such a cool, fascinating build. But my dislike of rubber bands has kept me from doing so until now...

It probably would have been better to use a shock absorber for the rear Leg instead, but idk how hard it would be swap one in as a MOD...

Edited June 15, 2022 by Gray Gear

[GerritvdG]

Fun project, looking forward to the end-result!

[Gray Gear]

After looking more closely at how the "real" Droideka is shaped and especially how it rolls up i realized how inaccurate this Set is. 

Especially the rear leg is off, folding completely in the wrong direction, backwards instead of forwards...

But this was probably done because it makes it much easier for the droid to stand up.

Edited June 15, 2022 by Gray Gear

[astyanax]

21 hours ago, Jeroen Ottens said:

I was there when it was designed. You have fold the arms and legs inwards and then roll the machine over the floor.

Once it is upside down the pin on top is pressed inwards and that triggers the unfolding of the arms and legs.

The inertia helps to unfold the rear leg. But, TBH, it was a fickle mechanism.

Fun fact: At the time we had modded versions at the design department that used springloaded shooters in the arms that were activated when the arms swung outwards. 

We got someone with first-hand experience, awesome! Probably nowadays something so fickle won't be approved for release. (But then again, some other recent Technic sets also got their fair share of issues...)

19 hours ago, 2GodBDGlory said:

I was reading about this set on Technicopedia yesterday, and decided I wanted to try building it too! The rubber bands do sound frustrating, though.

I don't think of it as frustrating... I set out to learn how the mechanism works, including the usage of elastic bands. Anyhow I'll share my findings when I get something resembling reliability.

13 hours ago, Gray Gear said:

It probably would have been better to use a shock absorber for the rear Leg instead, but idk how hard it would be swap one in as a MOD...

The rear leg has a large range of motion; would be hard to find a good placement for a shock absorber, without colliding with other mechanisms...

13 hours ago, GerritvdG said:

Fun project, looking forward to the end-result!

Indeed! Let me share some progress. The build is complete in terms of plastic. What remains is further tuning of the elastic bands.

Above you can see the 22L ziplines are a perfect replacement of the flex cables. Of course the ziplines can't go through the 'eyes' of the changeover catches, but the look & fit are great IMO.

I added a (yellow) elastic band on the rear leg, which helps to pull the 'lever' with against the rear leg. If this lever does not end up fully against the rear leg, the model will sag.

My main issue was with the 4x elastic bands added in step 25 (see first post). I doubled the amount. Now the rear leg does unfold fully.

The next issue that surfaced is that the front legs unfold too much. As I understand, the front legs are the first to unfold, but then the weight of the model must push down on those front legs, making them move back slightly in the folding direction. This will then trigger the release of the rear leg. In my case, the elastic bands unfolding the front legs are slightly too strong, causing the rear legs' release not to be triggered.

But if I use looser elastic bands on the front legs, they're prone to fall off during the unfolding action. So I'm still searching for the right compromise here...

[Gray Gear]

I started building this too earlier today. Idk how it will go, I dont have the 22L ziplines sadly, and my version will be mostly black. But my goal is to learn how the droid works, so i dont care about looks.

Edited June 15, 2022 by Gray Gear

[Gray Gear]

Finished mine about 2am today. Its not pretty, but that's not the problem. The droid lacks the power to raise the rear leg under its own steam. The rear leg does get triggered fine, but once it touches the ground that's it. I tried to add more rubber bands, but it didn't help, Maybe my rubber bands are too weak. So much is supposed to be moved with the rubber bands on the rear leg, the usage of a powerful shock absorber would be much better imo. But as @astyanax already said it is not an easy swap.

I built this to learn how this bot works, and i understand it now. But it is an unreliable mechanism, so I don't feel like modding the set would bear much better fruit 

[astyanax]

@Gray Gear If you look at step 25.1 depicted in the first post, you see the rubber band going from a ball-pin toward a gray bush. Try this: in addition to the rubber bands already in place, take a tight rubber band (or double-fold a larger one), and connect the ball-pin directly with the bush. Do this twice or more on each side, until the rear leg succeeds in lifting up the model.

[NathanR]

The mechanism is very temperamental, but you don't need to add or change anything to make it work out-of-the-box.

The droid did keep jamming up, failing to unfold, the first few times I built it when I was a kid. However, do you remember the picture in the instructions of a technic beam being squeezed with gears either side and looking unhappy? That's exactly what you have to avoid!

The solution is to simply make sure that you don't press the technic parts together too tightly. Check that every moving part, down to the 2L pin connectors, can spin freely. If in doubt, pull beams, bushes, liftarms, etc. apart slightly on an axle so there is a visible gap between each one. The whole mechanism should be feeling "floppy"by the time you start adding rubber bands on.

[allanp]

I remember this set as was always amazed and impressed with the mechanical design. I found you had to roll it just right, so the rear legs unfolds fully without touching the ground, it shouldn't have to lift the droid before it's fully unfolded. I remember that it would fully unfold, then the droid would drop down onto it after it had fully deployed.

[astyanax]

19 hours ago, astyanax said:

The next issue that surfaced is that the front legs unfold too much. As I understand, the front legs are the first to unfold, but then the weight of the model must push down on those front legs, making them move back slightly in the folding direction. This will then trigger the release of the rear leg. In my case, the elastic bands unfolding the front legs are slightly too strong, causing the rear legs' release not to be triggered.

But if I use looser elastic bands on the front legs, they're prone to fall off during the unfolding action. So I'm still searching for the right compromise here...

Given my supermarket-bought elastic bands, the solution for the front legs turns out to be to revert to what was apparently an earlier version of the Droideka, used for the photos in the building instructions.

According to the instructions, there should be ball-pins under the red circles, holding the elastic bands for the front legs. But by connecting them as in the photo, i.e. under the green circles, the elastic bands will be slightly weaker, as desired in my case.

Now the mechanism works as reliable as can be expected, and after practicing my throw, my Droideka unfolds perfectly every time!

=====

So I can now answer the question "Can set 8002 be built from modern parts and function using cheap elastic bands from the local supermarket?" with a definitive "Yes"!

 

[astyanax]

And here's the proof it works...

[GerritvdG]

24 minutes ago, astyanax said:

And here's the proof it works...

Nice!! 

[Toastie]

27 minutes ago, astyanax said:

And here's the proof it works...

Oh man, this is so cool and so nicely done. I also love the colors - this one is sure a chief or leader of a gang of a bunch of them (in lame gray).

Congratulations!!! And thanks for sharing - with your pictures and advice you have given here, I may actually try to make one myself ... and then for me, a dream comes true.

All the best,
Thorsten

[XG BC]

looks so good! works just like the "real" thing

[nerdsforprez]

Very neat. Thxs for sharing..

[2GodBDGlory]

I built a copy too a couple nights ago, and got it to work on one of my few tests without any tweaking. Hopefully I can make it more reliable yet!

[mla2]

What an interesting set, thanks for sharing!

[aeh5040]

Great work!  I always wondered how this set worked.

[Mechbuilds]

Somebody should make an RC version of this so it actually walks. 

[astyanax]

Thanks everyone for voicing your enthusiasm!! 

When I pull the model apart again -- probably before end of summer -- I'll post here a little "reconstruction guide" for prosperity, describing the elastic band diameters and quantities used to get it to work. (I think my supermarket-bought pack only contained bands in 2 sizes anyway...)