[HELP] Generic Building Help Topic

[vascolp]

On 8/7/2021 at 2:51 AM, Dr_Chronos said:

Please Excuse the hasty mock up, I'm trying to build a fire-spewing dragon. I'm concerned with improving how the twisty rod is pushed through. The best solution to me seemed to be a scissor lift. I figure that it will need to depend on the structure to travel straight, but I'm wondering how to have both sides of the lift move at the same time and if there is a better way to apply force that will give more torque.  I am not good at designing scissor lifts so I would appreciate any pointers. 

 

Maybe you could also take a look at set 8257 Cyber Strikers. Not exactly what you described, but the effect is very cool, maybe it could be used for fire spitting.

There are videos of it, search yt.

And in the end, please do show us what you have built. 

[npicard]

Hi all,

I'm trying to make a motorized gearbox – this is nothing new, but I have a special constraint. Due to the rest of the model, the motor changing the gears can't turn on and off. Continuous forward should change the drive shaft into first gear, continuous backwards should change into second gear.

Here is my current solution. Select gears by rotating the red 8-tooth gear clockwise or counterclockwise. Both bottom axles slide left and right together along with the catch that interacts with the driving ring.

There are a couple of problems with this build. The main issue is that I want to use the output from one or both tan gears (currently just held on with friction pins). They are turning at 1/20 the input speed, which is a really awful ratio.

Also, if there is a way to get the whole thing smaller, lower friction, or both, that would be great.

I don't think any of the above can be accomplished without a totally new mechanism – I think this one is pretty close to optimized (it's about a month of work and help from Reddit user u/Daap72).

Any ideas for a novel mechanism would be greatly appreciated! Improvements to this one are also welcome. Thanks in advance for your help.

[Keegan Pilling]

Would something like this fit the constraints of your build? Just replace the pneumatic valve with a red shift lever (or linkage to connect to one) 

Also, if you don’t have your worm gear offset by half a stud, you can replace the two pinions with 8 tooth gears, saves a lot of space and works better with Technic’s odd lengths.

Credit goes to Sariel

http://sariel.pl/2008/12/pneumatic-autovalve/

[npicard]

24 minutes ago, Keegan Pilling said:

Would something like this fit the constraints of your build? Just replace the pneumatic valve with a red shift lever (or linkage to connect to one) 

Also, if you don’t have your worm gear offset by half a stud, you can replace the two pinions with 8 tooth gears, saves a lot of space and works better with Technic’s odd lengths.

Credit goes to Sariel

http://sariel.pl/2008/12/pneumatic-autovalve/

That would likely save space, yes! Thanks for your input.

Unfortunately, it doesn't solve the issue of the slow output speed. I currently need to gear up the output from the tan gears from 1:20 back up to 1:1. The 20:1 gear-up requires 6 gears to accomplish. The solution you linked to would need either a 12:1 gear-up or 8:1 gear-up. Both of these also require a 6-gear train to achieve.

As I said, it's significantly more compact though, if I can figure out how to get the rotating liftarms to engage correctly with the red shift lever. Shouldn't be too hard.

Thank you again!

[Keegan Pilling]

Does the output from the two gears have to be in that position? If not, you could just put a 90 degree gearbox (two 12t bevels) on the end of the axle driving the worm gear.

Even if you need that output directly below the gearbox, couldn’t you just drop down the drive from the worm gear input with two or three 16t or 24t gears, and then have a 90 degree gearbox there?

[npicard]

15 hours ago, Keegan Pilling said:

Does the output from the two gears have to be in that position? If not, you could just put a 90 degree gearbox (two 12t bevels) on the end of the axle driving the worm gear.

Even if you need that output directly below the gearbox, couldn’t you just drop down the drive from the worm gear input with two or three 16t or 24t gears, and then have a 90 degree gearbox there?

The position of the output doesn't matter so much, but I need the current functionality that if the worm input is going one way, one of the tan gears rotates, and if it's going the other way, the other tan gear rotates. If I just took the input and outputted it straightforwardly, it would always be rotating in one direction or the other.

[Keegan Pilling]

8 hours ago, npicard said:

The position of the output doesn't matter so much, but I need the current functionality that if the worm input is going one way, one of the tan gears rotates, and if it's going the other way, the other tan gear rotates. If I just took the input and outputted it straightforwardly, it would always be rotating in one direction or the other.

What about one of these setups? If you want a 1:1 ratio without having to offset the red and yellow axles by 1/2 a stud, you will have to add a bar underneath the 2L liftarm, as done with the light blue mount in the second version.

https://bricksafe.com/files/Keegan_Pilling/designs/E16C9D06-B5DA-42ED-9367-5FA000851DAF.jpeg

[TheAbsoluteSt81]

Hi guys, I'm mainly a system builder but I'm interested in starting with Technic - I've only built a few sets (the blue buggy and small crane from the 2000s, and one of the early Bionicle beast sets which was made with Technic parts) so my experience so far is mainly limited to using Technic parts in system-scale MOCs for structure and mechanisms etc. Are there any short courses, social media pages (i.e. something like tipsandbricks on Instagram), videos or other content that would be useful?

[Milan]

1 hour ago, TheAbsoluteSt81 said:

Are there any short courses, social media pages (i.e. something like tipsandbricks on Instagram), videos or other content that would be useful?

Best way to learn and to improve is to just try to build something new. That way you will find what you like most and what suits you. You can always take a look at official sets for inspiration.

[Hrafn]

2 hours ago, TheAbsoluteSt81 said:

... other content that would be useful?

Welcome!

It is getting a little out of date since many useful parts have come out since it was published, but Sariel's "Unofficial Lego Technic Builder's Guide" book covers a lot of fundamentals.  I found it very helpful as a newcomer to Technic.

 

[howitzer]

10 hours ago, TheAbsoluteSt81 said:

Hi guys, I'm mainly a system builder but I'm interested in starting with Technic - I've only built a few sets (the blue buggy and small crane from the 2000s, and one of the early Bionicle beast sets which was made with Technic parts) so my experience so far is mainly limited to using Technic parts in system-scale MOCs for structure and mechanisms etc. Are there any short courses, social media pages (i.e. something like tipsandbricks on Instagram), videos or other content that would be useful?

Technicopedia is a great introduction to official sets and their functions, though it has not been updated for a long while. Still, you can learn lots of information regarding various functions and how they work there and also a get a great view on the history of Technic: http://technicopedia.com/

Brick experiment channel on Youtube shows many interesting and absurd contraptions and how they are built, and how to push Lego to its limits, very interesting stuff: https://www.youtube.com/channel/UClsFdM0HzTdF1JYoraQ0aUw

Sariel's website has some tools that help in designing MOCs, and building instructions for several interesting and useful machines, in addition to showcasing his MOCs. Also lots of technical information: http://sariel.pl/

Philo's website has tons of well-researched information on various Lego electronics and their characteristics: https://www.philohome.com/

[TheAbsoluteSt81]

On 8/18/2021 at 8:29 AM, howitzer said:

Technicopedia is a great introduction to official sets and their functions, though it has not been updated for a long while. Still, you can learn lots of information regarding various functions and how they work there and also a get a great view on the history of Technic: http://technicopedia.com/

Brick experiment channel on Youtube shows many interesting and absurd contraptions and how they are built, and how to push Lego to its limits, very interesting stuff: https://www.youtube.com/channel/UClsFdM0HzTdF1JYoraQ0aUw

Sariel's website has some tools that help in designing MOCs, and building instructions for several interesting and useful machines, in addition to showcasing his MOCs. Also lots of technical information: http://sariel.pl/

Philo's website has tons of well-researched information on various Lego electronics and their characteristics: https://www.philohome.com/

 

On 8/18/2021 at 12:26 AM, Hrafn said:

Welcome!

It is getting a little out of date since many useful parts have come out since it was published, but Sariel's "Unofficial Lego Technic Builder's Guide" book covers a lot of fundamentals.  I found it very helpful as a newcomer to Technic.

 

 

On 8/17/2021 at 11:49 PM, Milan said:

Best way to learn and to improve is to just try to build something new. That way you will find what you like most and what suits you. You can always take a look at official sets for inspiration.

Thanks guys! Will definitely order the builder's guide book and I've also found a few YouTube videos about suspension and gearboxes that have simplified them for me which have been useful.

[Hrafn]

I am building a 15-wide vehicle.  This is my prototype for the steering motor and gearing (the rack and pinion etc. are complete but not shown).  It uses a PF Medium motor geared 20/12 via two 8z gears and a 16z clutch gear used as an idler.  Return to center is done by hockey spring; the bracing for the hockey spring is notional here but I have a solid solution for it (not shown).

I am happy with the design overall but had been hoping I could also make the steering wheel rotate with the motor; the steering wheel should go in line with the bar with tow ball, or a stud to the right.  I don't think there is room to do this, but maybe you have ideas?  The motor can move up to two studs left, or be replaced with a PF Large motor and moved up to one stud left, if that helps.

https://bricksafe.com/files/Hrafn/technic-misc/20210822_225243.jpg

Edited to add: looks like I need to reinforce the structure - the PF-M tears it apart when powered by a BuWizz on Ludicrous speed.

Edited August 23, 2021 by Hrafn

[allanp]

@grohl has a few YouTube videos, like suspension for dummies for example, which you may find helpful. And also second recommendations for Technicopedia and the brick experiments YouTube channel, and also @nicjasno YouTube channel as he shows well the process of designing a MOC. You can also ask here if you are really stuck, although I also recommend just trying, failing, trying, failing, repeat until you get good. Ain't no substitute for learning how to figure things out for yourself. But of course we're happy to help 

[Scoar Sonander]

Has anybody got any prototypes ore builds for adjustable independent double-wishbone suspension? I have a setup currently using a worm gear plus an 8-tooth gear. The worm gear tends to move along the axle about a millimeter due to its shorter-than-2-studs length. Has anybody gotten around this? I don't have space to use LAs, by the way. 

[Hrafn]

35 minutes ago, Scoar Sonander said:

Has anybody got any prototypes ore builds for adjustable independent double-wishbone suspension? I have a setup currently using a worm gear plus an 8-tooth gear. The worm gear tends to move along the axle about a millimeter due to its shorter-than-2-studs length. Has anybody gotten around this? I don't have space to use LAs, by the way. 

Try the 1 stud long worm gear and a 20 tooth double bevel tooth.  The single stud worm gear does not slide the same way.

[Scoar Sonander]

1 hour ago, Hrafn said:

 Try the 1 stud long worm gear and a 20 tooth double bevel tooth.  The single stud worm gear does not slide the same way.

Thanks!

[doug72]

Improve axle connection to the centre of a Z60 Turntable

I have found it hard to get a strong connection for an axle to the rotating part of a Z60 Turntable.

This uses a Weapon Barrel p/n 6186131) which fits inside the Z60 T/T hole.

See images showing parts required and how it is achieved.

Edited September 12, 2021 by Doug72

[iLego]

16 hours ago, Doug72 said:

 

Nice idea !

Edited September 7, 2021 by iLego

[heyitsdisty]

Bit of an unusual request; any experts in physics / mechanical principles here?

Since TC11, I've been building Lego battlebots. Inspired by some videos online, I've built an axe-swinging mechanism that travels pretty fast. I've had a few people ask how the axe works, and I want to put together a video explaining the physics of the mechanism in a kid-friendly way.

Here's the problem. I'm not 100% sure I understand how it works - and I definitely don't know the right terminology to use!

Here's a video of the axe in action; please excuse the potato quality:

I've tried googling 'conservation of motion', 'inertia', 'jointed levers' etc. but I feel more confused than when I started...

Edited September 12, 2021 by heyitsdisty

[Hrafn]

@heyitsdisty, look at the physics of whips.  This appears to be a two segment whip, in essence.

[allanp]

@heyitsdisty interesting conundrum. Sorry I am no expert in physics, I could be wrong but in the slow motion video you can see that with each swing of the axe the motor accelerates twice. I could be wrong but I think this is the key. 

In a fixed axe setup you would have 1 thing happening, the motor turns on which accelerates the axe, and that's it. But you have a 2 stage thing going on. Firstly the motor turns on, and having little mechanical resistance it is able to accelerate really fast, building up lots of inertia inside the fast spinning internal motor rotor. Then the "slack" is taken up in the hinge and it is now trying to accelerate the whole arm in an instant, causing the motor to briefly almost come to a complete stop. But all that kinetic energy and inertia inside the fast spinning motor had to go somewhere, and I think it went into bending and stressing the framework and the hinge, but it is not wasted as that energy quickly rebounds, and releases itself like a spring back into the arm. It is at this moment that the arm starts moving, but also the motor can start moving again as well, so now you have a combination of that energy being released like a spring, and the motor adding energy into the system for a second time, to accelerate the arm at a faster rate than would have been if the hinge was not there. It seems that you have created a nicely balanced 2 staged system, with different forms of energy being created at different times, but being released together at the same time, combining to make a bigger wallop!

 

[howitzer]

I think the explanation from @allanp is pretty much point on. I can imagine this being really stressful to the parts, but then, broken parts are to be expected with battlebots.

[heyitsdisty]

Appreciate the insights, guys! :)

[Gray Gear]

Thank you for the explanation @allanp! I think it would be a good idea to add some rubber dampers where the arm hits the frame to prevent damage when he hammer doesn't hit anything.