[TC22] Mini RC Tracked Loader

[SaperPL]

So I've been contemplating what to build for the contest as the volume restrictions is something that should fall exactly in my area of expertise, but with RC allowed, it got a bit complex. To fully handle a crane or excavator you need 5 or 6 motors, so either two hubs or something like buwizz 3.0 which supports 6 motors, and I'm not really sure if I'll be able to fit all that perfectly within the specified volume while not making it a messy build. So I decided to stick to stuff that I can power with a single hub, and I love the ease of use of physical remote from CADA so I ended up deciding to go with a tracked vehicle + two mechanical functions, so after looking at multiple options I decided to pick a tracked skid-steer loader - a bobcat:

I like this one because it has an interesting geometry of the arms, which I expect to be there in order to prevent the bucket getting closer to the cab while the arms are getting raised. I yet have to test this theory.

Here's a concept / design so far:

I tested the geometry of the arm against keeping the bucket at same angle while the arm is changing its angle, assuming the lever holding liftarm over the arm has fixed angle, and it works more or less. I don't have a bucket yet, and I've got to figure out the driving connection for it that has a significant gear reduction as well as it should have some safety like clutch gear, but I'm not sure if it is a good idea considering weight of the bucket. I'm not 100% sure that I'll be able to go with the design of the arm that is supported by that liftarm to move forward/keep horizontal position of the bucket, especially because of the requirements for the bucket tilt lever connection to the motor.

Additional note here is that the tracks are shaped in a way that rear gears one exactly above each other because I couldn't achieve optimal track tension in other configurations and also I would have to make more space for the attachment of linear actuators behind the tracks and it would complicate the base structure.

Finally I might end up with arms hitting the cab, so maybe I'll have to move them by 1 stud to the sides, which would made the proportions weird, but I don't think I'll be able to shrink the cab without showing a mess of cables.

Edited May 21, 2022 by SaperPL

[Philtech]

That's a good idea. Your concept looks quite good.

[SaperPL]

5 hours ago, Philtech said:

That's a good idea. Your concept looks quite good.

Thanks!

I just checked this interesting geometry and it is really cool, but the issue is that it tilts the linear actuator a lot to shift the arms forward and the actuator would get blocked on the tracks. Probably better to keep things simple especially that I don't have any idea on how to tackle the drive connection to the tilt lever with such complex geometry...

[2GodBDGlory]

Looks like a fun little model! You mentioned that you wanted to use a CADA battery box, and while it's hard to tell, I think you've got CADA micromotors in there as well. Overall that should allow it to be very nice and compact, but I'd recommend that you get more confirmation from Jim that those are ok to use. I saw that you asked a couple times in the discussion thread, but never got an official answer as far as I can tell. I think it would be pretty cool if that stuff were allowed, but I would personally assume that they're not, especially since TLG supplies the prizes. Just thinking you might want to make sure about that before you put too much more effort in, though even if it would turn out to be ineligible, it'd still be a nice MOC.

[SaperPL]

7 minutes ago, 2GodBDGlory said:

but I'd recommend that you get more confirmation from Jim that those are ok to use. I saw that you asked a couple times in the discussion thread, but never got an official answer as far as I can tell.

Well, if @Jim didn't respond and since there are indeed smaller micro motors by Lego, discontinued however, but still, I'll take it as a yes unless he says otherwise.

9 minutes ago, 2GodBDGlory said:

Just thinking you might want to make sure about that before you put too much more effort in, though even if it would turn out to be ineligible, it'd still be a nice MOC.

Well, that's one of the reason I'm not "putting too much effort" as you said, meaning I'm doing it mostly for fun and I also don't want to overspend hoping to win. Big projects can pretty easily fail :P

[Jayden]

jim said:

''I have removed limitations on electronics and pull-back etc. ''

on the bottom of pg 1 of the discussion topic 

[2GodBDGlory]

3 hours ago, Jayden said:

jim said:

''I have removed limitations on electronics and pull-back etc. ''

on the bottom of pg 1 of the discussion topic 

Well, electronics are ok, but I think he elsewhere said that no third party stuff was allowed.

Either way, though, do go ahead with the model!

[Jayden]

16 minutes ago, 2GodBDGlory said:

elsewhere said that no third party stuff was allowed.

yes this is true but i think cada electronics would be ok

[Jundis]

Challenging model! But I think you should rescale, the whole middle part seems way to small. I even think this could tip over to the back :-/

[SaperPL]

7 hours ago, Jundis said:

Challenging model! But I think you should rescale, the whole middle part seems way to small. I even think this could tip over to the back :-/

It doesn't tip over, the battery box/hub is right in the middle and that's the most weight in the model. The back should stick out as there is potentially a weight in the bucket. I think the issue with how it looks is that those curved panels on the sides of the rear are visually increasing the size of the whole back where the real life machine doesn't have it that wide.

Anyway, I've tinkered around with arm geometry and it's a bit cumbersome, so I'm not sure if it's final or not, but I have something to show:

The bucket is being held at same travel as long as that white 24 tooth gear is locked in place. I still need to figure out the mounting of the motor for that gear, but it shows what kind of range of movement I'm thinking about. I probably need to reinforce the linear actuator attachment points at the bottom as it wobbles a lot while extending. The gif is at 2x speed - I'm planning to replace the input gearing inside the actuators from 12/12 to 24/12 so it'll be slightly slower than what it's on the video.

Driving works and has pretty cool wobble/jitter :P

[mpj]

It works really well! 

Why did you decide to have this feature (bucket at the same angle when rising boom) even if the real ones don't have it?

[SaperPL]

4 hours ago, mpj said:

It works really well! 

Thanks!

4 hours ago, mpj said:

 Why did you decide to have this feature (bucket at the same angle when rising boom) even if the real ones don't have it?

For one, at this scale attaching the linear actuators up there in the front would mean routing the input and making a lot of mess of the arms. I feel like this approach is slightly cleaner at small scale.

Secondly for a machine that can work as a forklift, I believe it should have this kind of feature - it is probably an option in the computer to control the tilt like that when raising the arms, or there should be a way for the operator to precisely control the speeds of rising the arms and bucket tilt change at the same time for the angles to even out.

Anyway:

I'm still not 100% sure if I should go with a model like this for the contest because it may be hard to beautify it without going full model team on the arms and the cab. There is still a lot of time and I can see a lot of potential in some manual models being made while pushing for RC functionality is a double edged sword when it comes to small scale models.

[Jundis]

25 minutes ago, SaperPL said:

still not 100% sure if I should go with a model like this for the contest because it may be hard to beautify it

Even if a video is attached, many vote for the look. And you can definitely do better here ;-)

[SaperPL]

21 minutes ago, Jundis said:

Even if a video is attached, many vote for the look. And you can definitely do better here ;-)

Well, my point is that it'll be hard for me to make it look really well to compete against other great entries we already see emerging, without going for model team approach on some big portions of such small model.

I know the model here is not up to the competition so far, it's just a prototype. I'm just thinking about whether I should upscale for the sake of looks, or whether I should go with a different topic/machine altogether and maybe even manual model.

[MP LEGO Technic creations]

Maybe I've missed something but is using CADA micro motors (as stated in video) allowed?

[SaperPL]

26 minutes ago, MP LEGO Technic creations said:

Maybe I've missed something but is using CADA micro motors (as stated in video) allowed?

I asked Jim that twice and didn't respond and others assumed that if general RC restrictions are lifted, those should be allowed. Also Lego had micro motors that are 1 stud shorter, so it shouldn't be that big of a problem. From my perspective, it's similar problem of buwizz 3.0 which has 6 motor outputs in compact package making it pretty competitive.

[MP LEGO Technic creations]

1 hour ago, SaperPL said:

Also Lego had micro motors that are 1 stud shorter

...significantly slower and less powerful. 

Now about the model itself - it looks pretty cute and tiny! 

The thing I like the least are probably the white technic panels #1 and #2 at the rear - couldn't those be swapped for smaller #21 and #22 ones?

I'd personally prefer all light at one place - moving turn signals towards the center instead one pair of red tiles.

But hey, it's still a WIP, so things might differ a lot from the final model.

[MangaNOID]

I wouldn’t rely on using non LEGO motors unless it’s specified ok in the rules as I can’t even use a single 9v instead of a battery pack (doubt I’m entering but very interested in all the builds)

[SaperPL]

14 minutes ago, MangaNOID said:

I wouldn’t rely on using non LEGO motors unless it’s specified ok in the rules as I can’t even use a single 9v instead of a battery pack (doubt I’m entering but very interested in all the builds)

I asked two times on the discussion topic and didn't have response from @Jim , but he stated those two things: 

On 4/8/2022 at 8:07 AM, Jim said:

• Electronics (PF elements, SBricks and Mindstorms) are permitted.

 

On 4/8/2022 at 1:05 PM, Jim said:

On 4/8/2022 at 12:55 PM, Jayden said:

I would assume buwizz 3 is allowed?

Yup, I have removed limitations on electronics and pull-back etc.

And since buwizz 3 is allowed (a small 6 motor supporting RC hub that handles both PF and PU, I believe CADA micro motors to be fair game unless Jim says otherwise.

 

21 minutes ago, MP LEGO Technic creations said:

...significantly slower and less powerful. 

Didn't knew that they are slower, but well. 

21 minutes ago, MP LEGO Technic creations said:

The thing I like the least are probably the white technic panels #1 and #2 at the rear - couldn't those be swapped for smaller #21 and #22 ones?

 I'd personally prefer all light at one place - moving turn signals towards the center instead one pair of red tiles.

Yes, I know about this. I'll be working on it as I need an attachment point at the middle of each linear actuator for them to not wobble so much. But I might need to start from scratch and re-scale/upscale it a bit as there are multiple shortcomings of going this small. It'll all depend on what I'm going to do with the arms.

[GerritvdG]

Thanks for presenting this cool little model. I think I've never seen such a small Lego RC construction vehicle, really interesting those CADA components! 

4 hours ago, SaperPL said:

Well, my point is that it'll be hard for me to make it look really well to compete against other great entries we already see emerging, without going for model team approach on some big portions of such small model.

This is indeed the weak point of this model. Going for a model team approach will is also a risk, I think we all appreciate a cool looking pure technic model the most!

And you master this art!

[Akassin]

It's incredible that such a small model is motorized. And I like your solution for holding the bucket angle!

[SaperPL]

On 4/16/2022 at 3:12 PM, GerritvdG said:

This is indeed the weak point of this model. Going for a model team approach will is also a risk, I think we all appreciate a cool looking pure technic model the most!

I've tinkered a bit with that idea, but I think that stacking two liftarms together and showing pins on the side will not look good in the end. I decided to go with simplistic approach of straight liftarm as an arm.

On 4/16/2022 at 10:09 PM, Akassin said:

It's incredible that such a small model is motorized. And I like your solution for holding the bucket angle!

Thanks! I simplified it though for the looks :)

I've finally had time and will to work on it more and I simplified the arms but to do so I had to rework the rear a lot. I'll need to figure out a way to reinforce it. Whole thing now feels like building a ship in a bottle where it comes to the rear. I'm too tired/lazy today to make the video though, I'll try to make it tomorrow...

I also finally made working doors/hatch at to front to access button and charging port:

As for the arm and bucket range of movement:

I added a big warning light on top which is spinning when the bucket is tilting.

I'm not sure about those liftarms with perpendicular pin sockets though as they are black and we don't have a white variant yet. I might go for simple straight 15L white liftarm instead. I don't think that holding the "rigid bar" in the middle is required but it's a cool detail that the bar is moving in it.

[SaperPL]

Video on the update: 

 

[GerritvdG]

On 4/30/2022 at 5:08 PM, SaperPL said:

I decided to go with simplistic approach of straight liftarm as an arm.

Yes, this is a nice solution. I'm not sure about the big warning lights and the other orange lights on the arm. I believe your version without the orange lights was more clean and realistic... just my opinion....

 

On 4/30/2022 at 5:08 PM, SaperPL said:

I might go for simple straight 15L white liftarm instead.

Sounds like a good idea, I'm curious to see how it turns out.

Nice container stacking in the video, the model seems to work really well ! 

[SaperPL]

5 minutes ago, GerritvdG said:

Sounds like a good idea, I'm curious to see how it turns out.

Ill just attach 92907 connectors around the liftarm to guide the links.

5 minutes ago, GerritvdG said:

 Nice container stacking in the video, the model seems to work really well ! 

I need to build some shelves and pallets for this. Those containers are bad because I don't have precise control over them, but it was an interesting experiment.

I think I need to rework the internals though - right now the hub and drive motors are in the middle so they are shifted half stud vs everything else, but it causes multiple issues with building some reasonable structure. I'll try to go asymmetric with the hub for it to be aligned with liftarm grid. It would be good if I managed to squeeze in the boat counterweight as well, but it's already hard to squeeze in the lift drive there.