[MOC] Rocky 42099 B model

[amorti]

Thanks didumos for your work!

I used to love Lego as a boy, but my last big Christmas set before 42099 was 8868, so now you know about me.

The Rocky is far more capable than the original model. If anyone is here wondering whether to pay 15e for the plans, stop wondering and just do it.

I've been out this evening driving it on some terrain the original wouldn't have a hope on. It's a shame to bang up the motors as they're the lowest point now, but it's fun doing it - I can't believe this is Lego :D

Suggestion: if you swap two of the 3-long pin/bushes from inside the doors and use them to hold the bottom L beam of the chassis, it becomes a flip open cover for the battery box. Muuuch easier to swap batteries that way!

I've been using an open front and closed rear differential so far, by I think I'll try it with both closed. The extra traction should be worth any tyre skipping.

The one thing I wish for is a bit more steering lock. I dropped the parts locking the front wishbones as noted above and it does help, although in one crash/flip that did allow the whole steering knuckle to pop out of the wishbones. There's some more angle available on the CV shafts, but the steering rack isn't long enough. I can't see any way to do it without a ground up redesign which not to mention being outside my comfort zone, would definitely need parts not included by Lego, so I think it's best just to live with it.

Guys, what RC tyres could you use on this model? For a bit more grip and/or "suspension".

[amorti]

 

[scooper22]

On 2/8/2020 at 11:18 PM, amorti said:

Suggestion: if you swap two of the 3-long pin/bushes from inside the doors and use them to hold the bottom L beam of the chassis, it becomes a flip open cover for the battery box. Muuuch easier to swap batteries that way!

I agree - this is the single most important mod to Rocky. It makes swapping batteries so much easier: just pull both bushed pins, open the bottom flap by rotating it forward and pull out the battery pack.

That way the box can be incorporated even more sturdy and permanent into the chassis as it does not need to be removed anyore and stay inside - with the batteries accessible from the underside.

What a great idea, amorti!

[Philo]

On 2/8/2020 at 11:18 PM, amorti said:

Suggestion: if you swap two of the 3-long pin/bushes from inside the doors and use them to hold the bottom L beam of the chassis, it becomes a flip open cover for the battery box. Muuuch easier to swap batteries that way!

I like it too! IMHO, it also requires to turn the hub 180°, or the battery retainer latches remain very difficult to operate. This can be done easily, but the button is now on the back, so the cable taming needs to be done a bit differently to keep accessibility.

[amorti]

If you don't bite your nails it's tricky but quite possible, but yes if you've not built Rocky yet you could flip the battery box for an even bigger usability gain.

Wouldn't that mess with the angle sensor though, make it think it's going downhill when it's going uphill? I really liked how didumos kept that functionality, and especially how the steering drives the front of the rack to keep that correct.

Actually I might pull it apart and build it again, with that in mind. And use normal pins from my stash where didumos had to use 1.5 pins within the constraints of a B model. I'll put some silicon grease in the turntables at the same time.

Any tips what's safe on Lego? I have a little red grease used on rubber brake seals (car) and some dielectric (silicon) grease usually used for plastic and rubber parts. The dielectric grease is much thinner/lighter so would seem a better choice.

Edited February 10, 2020 by amorti

[Philo]

Just now, amorti said:

Rocky yet you could flip the battery box for an even bigger usability gain

I just did that on an assembled Rocky ;)

Just now, amorti said:

The dielectric grease is much thinner/lighter so would seem a better choice.

Not so sure. Thinner might also mean more solvents, potentially harmful...

[amorti]

Just now, Philo said:

I just did that on an assembled Rocky ;)

Not so sure. Thinner might also mean more solvents, potentially harmful...

Does the angle sensor still work right?

No idea, guess I'll have to look if it has ingredients listed. I saw wd40 PTFE spray recommended, but haven't spotted any locally. Will keep hunting.

[Didumos69]

Thanks @amorti and @Philo for the suggestions. It would help me and probably also others if you could illustrate your modifications with some pictures.

[scooper22]

If the flap could be made to open to the rear it would be easier to open the battery box but it works anyway.

Rotating the box would also work but will probably mess up the sensors' orientations.

The bushed pins come from the inside of the doors, where there are plenty. The blue half-pins from the angled Technic L-beam are not needed anymore; those are currently stored by me in the Technic L-beam and you can see them in the pictures.

Edited February 10, 2020 by scooper22
embedding images

[Philo]

13 minutes ago, Didumos69 said:

It would help me and probably also others if you could illustrate your modifications with some pictures.

The same photos as @amorti, but with flipped hub ;)
https://photos.app.goo.gl/NhfpzreuJ3wigBQ67

24 minutes ago, amorti said:

Does the angle sensor still work right? 

Didn't thought about that... Well, the icons are inverted, but that's not really annoying (the value and warning remain meaningful).

[amorti]

Yes, it's just what I meant. I did use two pairs of pin/bushes but it's the same.

Wouldn't want to invert the hub myself, but there's probably a way to invert the frame of it right at the start of construction.

Technic function same, toy function improved :)

Edited February 10, 2020 by amorti

[Didumos69]

Thanks @scooper22, @amorti and @Philo. I will try to incorporate this in the instructions, using stock parts only, but that won't be soon. First need to finish my TC17 entry.

[Philo]

Just now, Didumos69 said:

First need to finish my TC17 entry.

...and maybe the BIs of TC17 in 42099 B-model version? :D

[Didumos69]

16 minutes ago, Philo said:

...and maybe the BIs of TC17 in 42099 B-model version? :D

Almost forgot about that. Need to find time for that too 

[amorti]

If it's a democracy, I'll take instructions for 42099C before incorporating these mods ?

[amorti]

On 10/21/2019 at 6:57 PM, Didumos69 said:

Thanks @Jim!

Here is a video showing how the front and rear axles communicate and how the center module averages between them.

I think once you've committed to making the locked differential variant, you can swap those 2x red 2-links employed as spacers for bevel gears. The 2-links can get caught up on the uneven surface of the frame, the bevel gears don't have that problem. Does mean the bevel gears are no longer available if you decide you chose wrong, but having tried crawling on both open and closed diffs, I don't see a need for the open diff version unless you're driving around on a high grip surface, otherwise just let the tyres skip.

[Didumos69]

1 hour ago, amorti said:

The 2-links can get caught up on the uneven surface of the frame, the bevel gears don't have that problem.

I appreciate your efforts to further improve this model, but in this case I doubt if this is an actual improvement. I can't imagine the 2L thin levers would actually touch the surface of the frame, not even under stress. The round end of the lever has radius smaller than 0.5L (0.45L to be exactly), so the axle would need to bend quite a lot to make the levers touch the frame. The depth of the smaller levers on the other hand, is exactly 0.5L and the depth of the thin bevel gears is slightly smaller than that (because they need to run smooth even when they have only 0.5L space). So imo using the thin bevel gears instead of the thin levers would slightly increase the chances of slipping gears inside the body differential.

[amorti]

Of course you're right - it can't hit the inside edges of the frame. There was maybe a little surface drag against the uneven face, but it wasn't the problem.

I have been working on the problem of excess friction in the bodywork differential, and I am pleased to say I have solved it. With the following solution you can literally pick up the model by the middle, and use light pressure from one finger to rotate the bodywork as the designer intended.

Here's how:

https://photos.app.goo.gl/Z8L35pHVhkRgDXtD9 (Not sure if possible to embed Google photos?)

You can bench test the two solutions shown in this picture, and even unloaded mine has noticeably less friction/jerkiness but the difference comes when it's all loaded with the weight of three motors twisting around.

The pieces remain all from the original kit:

1. 4x black pins can come from the yellow "coat hangers" on the front wishbones. They are there to stop the wishbones separating and the steering knuckle coming out, they don't need those pins.
2. Swap 2x 3L axles without end stops into the coathangers (the end stops aren't really needed here), then from there 2x 4L with end stops inside tie rod construction, giving you back 2x 3L axles with end stops. These stop the gears falling into the gearbox, which makes friction (try it!)
3. The 12T bevel gears are already available assuming you're building the locked differential version of the model.

It's not so easy to assemble the 4 gears inside the frame, but you can do it with patience. Put the side gears in at the same time, one from the top, one from the bottom. Check it has very low friction when finished, if not then you may have one of the gears a tooth high or low; just keep trying til it all moves easy.

Good news is you can now skip the alignment procedure in the instructions, just ensure both turntables are 100% perpendicular when you put the second of their tan driving gears on.

A good part of the benefit is because I've also lubricated the two turntables, which had a fair bit of plastic dust inside them, with this:

https://www.granvilleoil.com/prodInfo?pID=170

I happened to have it in the house, from my dad who's an electrician. He has it as it's safe to use on electrical wires, it doesn't eat the insulation like mineral oil does. I've looked at the specification sheet on the website, it contains no solvents but an "inert thickener". No guarantees of plastic-safety here, but I'm happy to give it a try.

Of course everything has a compromise. You now have to use a flex tube (from the original kit works well) to access the "connect" button on the hub.

I'd also point out there is a little wear evident on my CV joints. Considering what I've been doing with the model (see video above) and on locked differentials, I am not upset by it. Just know that if you do the locked diff version, there are no Cardan joints to snap, but there will be wear on some pieces.

Edited February 15, 2020 by amorti

[amorti]

I've rebuilt Rocky 1 today and although what I've mostly learned is that @Didumos69 was really efficient with reusing what he had, I had a couple more good ideas which can just about be done without digging in the spares bucket. Although life certainly gets a whole lot easier if you allow yourself a few spares, particularly black pins!

I don't run the front wishbone braces as they limit steering when there's already not much available, so I've had the front wishbones pop open and spill hub parts everywhere when I've rolled the model. I wanted to brace them, but without obstructing the steering.

If you do the centre diff like this: https://photos.google.com/share/AF1QipNvZCQJ9GVaAh7FA7hXvMxItw6mlmMteoQtOVxBAepjQ1m919fbYeOWllQHTYhfCg?key=MUFmNkF5akpWSElrcU9tVG9LTUY0eU1HVXRFWGRn

using 4x black pins from the wishbone reinforcements (which I guess most people took off for extra steering angle) you get the two red 2L beams back. 

Now do step 37 like this: https://photos.google.com/share/AF1QipNC-cJT1jpAPQo1AIIj7WlffChVvc0UJTSapb6oLspNBzRxmF0TUWuDV5mYDQBA2w?key=M1ZGUWF3NjNOQTJqTE9PUnFmQ3JqMjlncGxFZVZn

So you get the two 5 liftarms back. The extra two half pins were spare (could also use the non-friction half-pins, and/or there will also be 2 pin-axles available), the bush-pin is swapped from inside the doors. This is neater if you have a couple of 11L liftarms spare.

Now you can make the front like this:

https://photos.google.com/share/AF1QipNkY8Nsg8MBKgFK1slIcYnQNcOBmNtwu1njSA8k1oUj66b6W0vTq6bo8vdIuzJsqQ?key=Z2dJbXZmQmNBS3VTanRSOXBDb09PcWlwX1ZVSUFB

Which braces the wishbones together, without obstructing the steering.

You do need those 4x black 2-links from the steering knuckles (I hid the red ones inside the diffs) to make it work. I'm not sure if they're essential or could just be taken? In any case I replaced them with orange 2L liftarms which are freed up in the next stage. I reached into the spares and grabbed 4x black pins but you could use 4x half-pins which are spares.

Next, I wanted to get a solid stop on the rotating suspension. If the vehicle is rolled, the suspension would often get past the existing stop which is bad for the motor wires.

In the end it looks like this, and works great. https://photos.google.com/share/AF1QipPg3WVC8pUAP-RgVAj87tOKXJSkrDx70jdLXy7Dtz0shWX8mMEZwrbdjniQF14bRQ?key=QmVGa195UG54dGR5NnFoeDRoaVNCUDFYN09KYmlR

You also have an option to add a more restrictive stop if you prefer, e.g. a 2-axle and 2 half axle bushes, but this would need your own spares to make. Don't go with a 3L and two bushes, it'll just push the spring holders off their pins.

In step 52, slide the 10 axle through spacer 18654, then T piece 63869, then spacer 18654. This gives slightly better support to the central axle but more importantly it gives somewhere to pin (using some imaginary black pins - that Didumos doesn't waste any!) another T piece 63869 with the axle connector facing downwards. It also freed up two of those orange beams for use in the steering.

To free up those 2x T pieces 63869 you just used (assuming you can't/don't want to take them from spares):

- In step 59, do the same for the front differential axle but use a black 42003 which was freed up by not doing step 339 as the axle no longer reaches the button anyway. You might need to put the 2x red 42003 holding the springs the other way up to make space, I'm not sure as I just used a 6536 from spares.

- In step 113/122, use 2x green 3-beams in the front lower wishbones to free up 2x T piece 63869 (I used white in my picture because I had them and it was less ugly than green)
- In step 286, use 2x connectors 48989 in the rear lower wishbones. This also frees up 4x 3L pins which should allow you to get some black pins back, somewhere!

Edited March 13, 2020 by amorti

[mic8per]

Amazing!

[amorti]

I do think the grease makes a big difference. Without grease the weight all hangs at the bottom point if each turntable and there will be white plastic powder there when you open it up. Don't use mineral grease only silicon grease!

[amorti]

4 minutes ago, LegoIstanbul1907 said:

thank you for your reply. because i have done your adjustment with very big difficulties but finally achieved to do. now its time to apply silicon grease. do you have any advise for this model ? for example to achive batery box easily ?

There are posts above regarding making the battery box much more accessible.

If you've already got the model built, you'll have to torture a few pieces but it's still possible to make the modification at this point.

To note: rechargable batteries are heavier than regular batteries. Ofc we should be using rechargable cells because of the environment, but the performance of the model does suffer from the extra weight.

[amorti]

I do like the idea of a lipo battery, very nice. The lower weight will be a big help in getting up hills that Lego models should never have tried 

I think I'll wait for Lego to come with that tech though. 3D printing and sourcing my own battery and charger etc is a bit further than I'm willing to get involved.

If you could take a 3S battery and regulate it down to 10.4v to suit the electronics... Now that would be something.

[Philo]

35 minutes ago, LegoIstanbul1907 said:

You have wrote about the 2 speed gear box with another motor ? Is it possible to do this. (everything is possible ofcourse with you and experienced other friends)

Hi @LegoIstanbul1907,
Sorry, I haven't got further on this (actually I'm not such a great builder )

[gregorski904]