Gundam Hip Assembly

[aadder]

Hello everyone, 

I'm working on a 40cm tall Gundam, and I need advice on the waist. I would LOVE to have a rotating waist, but given the size and weight, I'm worried it would be a point of failure. Given the dimensions, I'd be relying on a 4x4 turntable plate and that axel to hold the 2 halves of a giant robot together. The idea being that the hips will be built around a gearbox that is re-enforced such that it can be pulled apart vertically so that the axel and 4x4 turntable plate will attach it to the torso. The end of the axel inside the upper torso is flared and can't be pulled out from this end, so as long as the tension on the hip side holds up, the build should stay together.

The alternative is very appealing because if I go with one solid torso, I can really reenforce it with pegs, but the downside is that i will lose functionality and the torso will just kinda be a big ol' brick. 

Is there an approach that I don't know about that might help? I know Lego generally shies away from any kind of hip articulation and i assume it's for structural integrity.

The alternative-alternative might be using super glue to glue those gears onto the axel, thus ensuring it can't come apart, but i feel kind of dirty using glue on legos, even if they can be dissolved later if need be. 

Thanks for all of your help. 

 

EDIT: so apparently i don't know how to attach images? I tried to attach two images to assist but they won't display? 

 

Edited October 28, 2020 by aadder

[NathanR]

What you propose sounds ok to me, but I would worry that single technic axle is not strong enough to support the mech's body. While it won't necessarily pull apart, it might get twisted. Instead of a 4x4 turntable plate with axle through it, consider building a more heavy-duty version with a stack of 2x2 round bricks with an axle in the middle, slotted into a stack of 11833 v4x4 round plate with 22 cutout.

If the hips have a gearbox, it sounds like you are using plenty of technic - have you considered using the technic turntable parts 18938 with 18939? It can support quite a bit of weight, for example, in set 42042 Crawler Crane it is the sole linkage between the caterpillar track base and the crane super-structure.

Also, maybe have a look at the 21311 Voltron, the black lion had a great technique using the small technic turntables that allowed the arms to be attached, and gave quite a bit of friction to hold them in place.

[howitzer]

I'd also recommend using large Technic turntables here, like NathanR suggested. They are easily strong enough to support even much larger builds so you'll have no problem if you just connect the turntable properly. The only challenge here might arise from the fact that Technic parts are made for odd-sized constructs while System is built mainly for even-sized ones, but even that should be easy enough to overcome.

[aadder]

22 hours ago, NathanR said:

If the hips have a gearbox, it sounds like you are using plenty of technic - have you considered using the technic turntable parts 18938 with 18939? It can support quite a bit of weight, for example, in set 42042 Crawler Crane it is the sole linkage between the caterpillar track base and the crane super-structure.

So what i DO have is the turntable from the Crawler Crane 7632, which might actually work better for me because it has studs to interface with System parts better. Do you think that would be a good substitute? It seems to be REALLY hard to pull apart but i don't know how it compares in sturdiness to the one you suggested. 

Edited October 28, 2020 by aadder

[howitzer]

12 hours ago, aadder said:

So what i DO have is the turntable from the Crawler Crane 7632, which might actually work better for me because it has studs to interface with System parts better. Do you think that would be a good substitute? It seems to be REALLY hard to pull apart but i don't know how it compares in sturdiness to the one you suggested. 

Yes, the old turntable would work too, perhaps even better, because as you say, it has studs for connection points and it is also designed for even-sized constructs rather than odd. It probably has more friction and slack than 18938/18939 turntable though.

[aadder]

I was able to incorporate the top half into the chest of my build pretty easily; i was already using a row of pegs to attach the obliques to so this worked out well. 

What do you mean by friction and slack? 

[howitzer]

8 hours ago, aadder said:

I was able to incorporate the top half into the chest of my build pretty easily; i was already using a row of pegs to attach the obliques to so this worked out well. 

What do you mean by friction and slack? 

The old turntable simply has a higher friction, as in turning it takes more force, especially if there's a high load on it. With slack I mean how much play there is between the top and bottom half. Slack allows the halves to go out of alignment and can lead to higher friction if the load is unbalanced. In your build though, I'd guess that neither of these is a significant problem.