[HELP] Generic Building Help Topic

[doug72]

55 minutes ago, Leo12 said:

It’s not that I want it to rotate in one direction, I just want to make sure that the output can’t drive the input.

Is the input rotatind one way all the time or is ir reversable  ?
Can you post an image or a diagram of what you want to achieve ?

[ukbajadave]

9 hours ago, Leo12 said:

...I need something that can only be driven one way...

I like it when I have something to occupy my mind  So:

One input and one output.

Should not allow backdriving.

Any gearing up/down needed?

Does input/output need to rotate in both directions?

How much torque? (Would a linear clutch on the output be sufficient?)

[Leo12]

9 minutes ago, ukbajadave said:

I like it when I have something to occupy my mind  So:

One input and one output.

Should not allow backdriving.

Any gearing up/down needed?

Does input/output need to rotate in both directions?

How much torque? (Would a linear clutch on the output be sufficient?)

Yes, that’s what I’m looking for. Ideally it would have very little change in gear ratio, but definitely not too much gearing down(unlike a worm gear). Both sides should be able to rotate in both directions, and it needs to be fairly torque resistant. If it helps, I’m using it for a three speed differential gearbox. I need to make sure the axle from the differential can’t back drive when the driving ring is disengaged.

Edited June 17, 2020 by Leo12

[ukbajadave]

First attempt, Yellow is input, red is output. Turning yellow axle turns red axle freely. Forcing red axle results in skipping teeth between differential and tan 20z.

[Leo12]

2 hours ago, ukbajadave said:

First attempt, Yellow is input, red is output. Turning yellow axle turns red axle freely. Forcing red axle results in skipping teeth between differential and tan 20z.

I like this solution. Thanks for the help!

[aeh5040]

On 6/17/2020 at 5:22 PM, ukbajadave said:

First attempt, Yellow is input, red is output. Turning yellow axle turns red axle freely. Forcing red axle results in skipping teeth between differential and tan 20z.

That's quite amazing.  I was going to reply that I thought it was impossible without a worm...

Do you understand why it works?

Edited June 19, 2020 by aeh5040

[ukbajadave]

1 hour ago, aeh5040 said:

Do you understand why it works?

In a word no 

I think when you drive the yellow input both diff outputs (black axle, red axle) turn in the same direction. When you turn the red axle the black wants to rotate in the opposite direction?

I'm not even sure it isn't some weird friction type thing. If someone else wants to build and confirm it works (or doesn't?)

My instinct is that a worm gear solution exists but I haven't found it yet. 

 

Edited June 19, 2020 by ukbajadave

[aeh5040]

I think it must involve friction somehow - even a worm does.  But it's very surprising.  I will indeed try building it (or a variant)...

Edited June 19, 2020 by aeh5040

[ukbajadave]

Help needed please with Linear Actuator geometry. Pictured below is what I have so far. The problem is that when the tipper is flat the LA is almost horizontal. When I start to tip the LA pushes the bed back before it starts to lift with a jerk. Is there an optimum spacing that gets me lots of range with a smoother motion? The less rebuilding needed the better 

All comments gratefully received.

[Jeroen Ottens]

Either lower the attachment point in the tractor or mount it higher on the dumpbed. One stud on either side makes a world of difference.

[Jundis]

Hi guys! I am currently tinkering around the idea of building a mobile rescue crane with a lot of PU-functions. The real one has different steering modes, the three I want to replicate are the following:

 

In the Claas Xerion, they did this well with a sliding connector. With my intended axle width of 11, and way less space above the axles (and my intended suspension), it seem unlikely to fit in. Another solution is a gearbox, engaging the different axles and changing the angle according to gear ratio. This however will need to always return to a neutral point to engage the gears in the right manner. Also it will be a bit flimsy, since when in neutral, axles not engaged can move in whatever direction possible, not be fixed in place.

 Is there another solution for this?

Edited June 26, 2020 by Jundis

[MikeTwo9398]

You could try this (not tested just an idea).

https://bricksafe.com/files/MikeTwo9398/steering/Steering_option.jpg/800x450.jpg

Servo 1: select steering mode

Servo 2: Both axles rotate in the same direction

Servo 3: Both axles rotate opposite

If no mode is selected with servo 1 then funny things might happen

 

Edited June 27, 2020 by MikeTwo9398
Added picture to flickr (don't know how to add pics from Bricksafe)

[Jundis]

Thx @MikeTwo9398

The thing is, this solution only powers 2 axles, I need 4. Also ideally, one motor should be steering and the other one steering mode (both are PU L-Motors). Also in your solution as you said, funny things happen as the wheels can go evry direction^^

My solution would rather be, that the first axle is directly coupled to the steering motor, then the same axle goes into the gearbox. The second axle only has to be selected for full steering (crab speed) or half steering (other modes). And so on for the other 2 axles. The locking in place is hard to do here... *stillthinking*

[pleegwat]

A possibility for 3 axles would be to have 1 servo control the front wheels, a second servo control the rear wheels, and the central axle controlled by a differential which connects both. That could then scale to 5 axles by averaging the front/rear and central axle for the 2nd and 4th axle. I'm not sure how you'd scale that for 4 axles - maybe use the 5 axle setup I sketched then omit the middle axle?

[Jundis]

Hmm for 5 axles (and even 4 axles), this would be problematic as the second and fourth have different angles in the steering modes. Maybe I drop the crab steer completely and just go for one or two modes.

[Jeroen Ottens]

30 minutes ago, Jundis said:

Hmm for 5 axles (and even 4 axles), this would be problematic as the second and fourth have different angles in the steering modes. Maybe I drop the crab steer completely and just go for one or two modes.

I made a two mode steering in my Liebherr LTM11200. I explained how I did it in the original topic here on Eurobricks. However, you want to have three mode steering, the only way I see that happening is using a Control+ motor per axle and then hope that SBrick Pro gets released soon (or that LEGO comes with their own programming suite). With these motors (and the associated programming) you can get any steeringmode you want. Not very interesting from a mechanical point of view, but more like real-life vehicles in a way since these are also individually computer steered axles nowadays.

[MP LEGO Technic creations]

Hello everybody! 

I'd like to ask, how to make a parts list in Stud.io?

I didn't find any Stud.io discussion so I posted it here.

Thank you.

[suffocation]

@Jundis This isn't exactly what you're looking for, but it might help. (I believe it's by @Superkoala)

 

[Jundis]

Thanx @suffocation  ! This so far is the best mechanism I have seen. I'll let it sink in and try if it will fit :-)

Different gear sizes with a selector will also work, although they different heights of gear racks are needed.

Others like this are just way to big to implement in my moc (and overcomplicated).

[hawkwind]

So I'm wanting to start working on advanced Lego Technic builds, and am wondering where to start. I already have a reciever, controller, battery pack and a fair understanding of how cars and suspension work, and want to know 1. What is the best thing to start trying and learning about and 2. If I am mainly interested in making off road type rc vehicles to start, want to just buy power functions and am not really interested in buying the powered up powered parts, where is the best place to spend my first 200-250 USD on Technic parts?

[Jurss]

Then buy lego rc motor and other necessary parts.

Bur remember, Lego never will be same as real rc car.

[Touc4nx]

I would say, the best place to spend your money depends on the parts you need...
If you want some specific ones then use Bricklink, but depending on the part it might be expensive.
If you want some thecnic parts, you can check this store : https://www.ebay.co.uk/str/bagsobricks (there are some interesting parts pack)
If you have more time, and don't necessary want new/recent lego, I would suggest you to go in the bric a brac sale near you, it's definitely the cheapest way to buy lego.

[onzenuub]

9 hours ago, hawkwind said:

where is the best place to spend my first 200-250 USD on Technic parts?

Brickowl.com and for nice off road MOCs have a look at rebrickable.com

[Erik Leppen]

On 6/26/2020 at 5:50 PM, Jundis said:

Hi guys! I am currently tinkering around the idea of building a mobile rescue crane with a lot of PU-functions. The real one has different steering modes, the three I want to replicate are the following:

In the Claas Xerion, they did this well with a sliding connector. With my intended axle width of 11, and way less space above the axles (and my intended suspension), it seem unlikely to fit in. Another solution is a gearbox, engaging the different axles and changing the angle according to gear ratio. This however will need to always return to a neutral point to engage the gears in the right manner. Also it will be a bit flimsy, since when in neutral, axles not engaged can move in whatever direction possible, not be fixed in place.

 Is there another solution for this?

One solution is to control the first and last axle independently, and use a beam to interpolate the intermediate axles. Works like a charm on small models. On large models, probably needs a stronger way to do this.

 

[Lipko]

33 minutes ago, Erik Leppen said:

One solution is to control the first and last axle independently, and use a beam to interpolate the intermediate axles. Works like a charm on small models. On large models, probably needs a stronger way to do this.

 

That's simply genoius.