Intentded weak or flexible connections in large and heavy models?

[Void_S]

Hello everyone.

I have a question to TLG, or, if it has already answered or discussed I would apologize and ask to merge the topics, as there was a topic with questions to TLG designers (a-la "questions to TLG"), but unfortunately, I can't believe I didn't find it.

The question that can't leave my mind is either TLG designers intentionally make some weak or flexible points after righty (or maybe even some crash) tests to minimize the risk of the parts broke by controllable deformation or expectedly un-assembling the model?

The great example of 100% rigidness are Didumos69's MOC: they are just rock-solid (I really like them, by the way) and possibly just can't be broken, but on other hand they contain a lot of parts.

There is another story for TLG sets: they contains less parts (yes, the marketing, pricing and other things, but it's not a topic here) but enough to provide some specific balance between rigidity and flexibility.

For instance, I spend some time on modifying the 9398/41999 axles (I'll share the results once, it became just a monster buggy with the less possible changes) and I thought that the steering racks and arms are the weak point of the construction: bumping into some obstacle at the full speed may broke them easily (just a single axle+hole connection, plus very fragile 6536 connector), so I reinforced it by hard (I thought) but when I accidentally bumped it into the table leg, all the stress came to the portal hub and broke its mounting holes.

I repaired the holes with a soldering-iron and restored the original TLG's construction (but replaced the 6536 connector with just a coupe of more strong parts), and I was surprised how perfectly it handles the bumps just bending a bit the 8L axle even when the whole model crashed at the full RC motors speed. Rigid enough to steer with a minimal backslash, and flex enough to absorb such crashes.

I found the similar places in other models (the only thing that bothers me is 42070's crane arm that bends too much) so I believe that it's a kind of specific idea, especially for large and heavy enough modes that comes nowadays to safe their parts against being easily broken under such workload.

[Jeroen Ottens]

I know that we had to redesign the Power puller after the test department came back and showed we could churn gears by running it into a wall (that's the reason there is a gear on a lever in the drivetrain that will disengage when the model is topped while the motors are still running). So yes, I would think they will still redesign the model if they find that parts get broken when running models into obstacles.

[letsbuild]

Interesting concept. It makes sense to do add weak points to stress-heavy parts of the model.

[Void_S]

6 hours ago, Jeroen Ottens said:

I know that we had to redesign the Power puller after the test department came back and showed we could churn gears by running it into a wall (that's the reason there is a gear on a lever in the drivetrain that will disengage when the model is topped while the motors are still running). So yes, I would think they will still redesign the model if they find that parts get broken when running models into obstacles.

Yes, it's certainly the thing I'm talking about: self-unmounting pins that disengage the steering arm and rack after a hard bump and save the wheel hubs and suspension arms like in 42029 and 42037, self-disengageable gears that saves the drivetrain (some models even have "torque-slip" clutch gears) and other similar examples when some assembly consumes the stress load and easily blows off protecting the parts when it's going to broke them.

Thank you for proving my speculation 

[allanp]

The disengaging gear in the power puller is interesting but I though it was there to stop damage occuring when the model is pushed forward by hand or when its carried forward under its own momentum when the motor is stopped, like the rotors in the large helicopter.

[Jeroen Ottens]

6 hours ago, allanp said:

The disengaging gear in the power puller is interesting but I though it was there to stop damage occuring when the model is pushed forward by hand or when its carried forward under its own momentum when the motor is stopped, like the rotors in the large helicopter.

No it really was the drive-against-the-wall-test. It was actually quite a hit in the office for a week or so. There is something strangely atractive about grinding gears to powder 

[gate]

Pretty sure that TLG did not design every single special "weak" or "vulnerable" spots in the models. Simply because not every set was designed by one man. There certainly are some places that seem to be planned. I feel like it is a flaw of some mechanisms that lead to this topic theme, like u-joints, cv-joints, bending of beams etc. It is plastic after all and it has limits. It all comes down to what function this or that part is fulfilling, and bear in mind that TLG respects all ages of users - this is where such failsafe mechanisms and disengaging gears as mentioned above come into play.

Overall I think it is a very good thing they exist. It gives us space for improvement.

[allanp]

2 hours ago, Jeroen Ottens said:

No it really was the drive-against-the-wall-test. It was actually quite a hit in the office for a week or so. There is something strangely atractive about grinding gears to powder 

Ah I see. Im always facsinated reading your posts about the inner workings of the Technic team