[HELP] Generic Building Help Topic

[mdemerchant]

1 hour ago, GeorgeCrecy said:

I am namely needing the bottom round area replicated

Do you mean the cam or the connecting rod end?  Either way, system parts seem like the obvious choice to do it but at least the connecting arm seems doable with technic as well.  Some things that could help would be considering that the connecting arm hole does not have to be round to make the mechanism work and that the cam could lock around the rod instead of the other way around.  Here's an idea, I don't know if it's what you had in mind or not.  You could definitely make it look nicer if you lock the rod around the cam but with a 4x4 cam I'm not sure that's possible because you need clearance to put the axle somewhere.  You could do it with 6x6 cam made out of 6x6 round plate(s).

[GeorgeCrecy]

36 minutes ago, mdemerchant said:

 

Hey there mdemerchant!

I certainly don't mind the flipping idea, but my one issue with the design is how easily one the bottom plates could pop off if the mechanism moved. 

Regarding the main axis of the crankshaft, I wouldn't be using the middle of the 4x4, and would instead connect a 2x2 to one side on top of the 4x4, and that would be the center of the crankshaft, thus leading to an offset rotation. Take a look again at the gif if I am explaining things terribly, as I am won't to do.

Edited October 7, 2022 by GeorgeCrecy

[mdemerchant]

21 hours ago, GeorgeCrecy said:

I certainly don't mind the flipping idea, but my one issue with the design is how easily one the bottom plates could pop off if the mechanism moved

Yes, I don't think I would build it like that exactly, I was just trying to show a quick idea.  It would be much stronger to use another 6x6 round plate and tiles instead but that would make it a little thicker.

If you are willing to make the cam 6x6 instead of 4x4 you can do something like this which will be nicer and stronger.  Some parts cut away to show how it's built.

Edited October 8, 2022 by mdemerchant
typo

[MKJoshA]

Question, I'm building an ocean scene using the net technique. I've got liftarms under rotating to simulate waves. But it seems to be too much for the 1 motor I have hooked up. Do I need multiple motors or is there a better way to rig this? I'm trying to keep the profile low.

[Zerobricks]

I suggest you use 16 tooth gears insetad of 24 and 8, it will run much smoother that way.

[howitzer]

Another thing to try might be replacing the worm gear with spur gears, as the worm gear tends to have high friction with significant load. Also trying the PF XL motor might help, it has highest torque of all motors (save the buggy motor) with low rpm, which means less downgearing and thus less friction.

[mdemerchant]

The suggestions above are all good and will definitely help I think but another thing you could try is connecting the various axles by linkages instead of gears since you are just trying to drive them all in sync anyway.  Then you just drive one axle directly.  This might have less friction, or not, but it could be worth a try.

[MKJoshA]

On 11/7/2022 at 2:16 PM, Zerobricks said:

I suggest you use 16 tooth gears insetad of 24 and 8, it will run much smoother that way.

Thanks, tried this and it seems to be working.

On 11/7/2022 at 3:30 PM, howitzer said:

Another thing to try might be replacing the worm gear with spur gears, as the worm gear tends to have high friction with significant load. Also trying the PF XL motor might help, it has highest torque of all motors (save the buggy motor) with low rpm, which means less downgearing and thus less friction.

I can dig my XL Motor out of the set I have it build into, but I worry that even then it would have too much power. I think I need the worm gear to ensure it doesn't rotate too fast.

On 11/8/2022 at 10:37 PM, mdemerchant said:

The suggestions above are all good and will definitely help I think but another thing you could try is connecting the various axles by linkages instead of gears since you are just trying to drive them all in sync anyway.  Then you just drive one axle directly.  This might have less friction, or not, but it could be worth a try.

Sorry, I'm kind of a technic novice. How would I use linkages to accomplish this?

[howitzer]

12 minutes ago, MKJoshA said:

I can dig my XL Motor out of the set I have it build into, but I worry that even then it would have too much power. I think I need the worm gear to ensure it doesn't rotate too fast.

Sorry, I'm kind of a technic novice. How would I use linkages to accomplish this?

The XL motor isn't very fast by itself, and you could always use spur gears to reduce the speed, I think equal reduction with them would have less friction than a worm gear. Worm gear is great when you need a lot of reduction in small space or a mechanism which can't be backdriven, but neither appears to be a problem in your build.

You can use a simple crankshaft linkage to convert rotary motion into reciprocating motion, and then it's just adding beams connected to axles which drive the pushers under your "water".

[mdemerchant]

17 hours ago, MKJoshA said:

Sorry, I'm kind of a technic novice. How would I use linkages to accomplish this?

It can be as simple as something like this.

You drive one axle with the motor and they all turn.  Or you can make a full crankshaft structure as @howitzer mentioned which would let you run multiple connecting beams off one driven axle.  What I showed above is technically a crankshaft also but it's only driving one link.  Check out the linked amination below for a more generalized case which shows four links and includes translation to back and forth linear motion (the pistons) if that is useful.

https://en.wikipedia.org/wiki/Crankshaft#/media/File:Cshaft.gif

 

[weavil]

On my helicopter, I want to put landing bars. What would be the best way as the weight is concerning.

[allanp]

2 hours ago, weavil said:

On my helicopter, I want to put landing bars. What would be the best way as the weight is concerning.

 

wouldn't regular angled axle connectors be strong enough? I guess they might sag or bend over time. Would 4*4 angled beam be good for the supports of the landing bars? The front legs won't have to be that strong but the rear ones will have most of the weight on them.

[Jurss]

For display purposes, I think, anything could work. For some playability not so easy.

[Technic tango]

How would I achieve motion like in this video:https://streamable.com/0t41k3 ? I already have a mockup on the side but i doubt it will be strong enough to lift the model, so i will likely need to get some more large linear actuators. Anyways, i would just like to know if anyone knows a way to make a linkage that can move in such a way shown in the video 

[Jundis]

@Technic tango Sadly I don't have time right now to tinker, but this motion could be done by a linkage system with 2 swing arms of different lengths. As one of my profs in technical mechanics once said: Nearly every movement can be replicated by a clever 4 linkage system.

I used this on my Transformation Vehicle also:

In your case, the links maybe should cross to gain the angle changing movement. If the caterpillar drive should lift the vehicle, you definetely need the big LAs.

[Technic tango]

15 minutes ago, Jundis said:

@Technic tango this motion could be done by a linkage system with 2 swing arms of different lengths. As one of my profs in technical mechanics once said: Nearly every movement can be replicated by a clever 4 linkage system.

 

Seeing this, this leads me to think there may be a website or program that you can plot a path and give some restraints then have the program solve the linkage lengths... im no good at this sort of math yet so ill look for my self in the mean time edit: found this, gonna try it tomorrow.https://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

 

Edited December 1, 2022 by Technic tango
Additional information

[Mpafr]

Hey all, I am looking for suggestions on how to make my car go very very fast. 

I am currently using a buggy motor connected directly to the rear differential, to reduce loses. I am powering it with 3 x 3.7V, 3400 mAH, 18650 li ion, rechargeable batteries to give it some extra juice, and controlling it with an IR RC. 

Without any load the wheels go very fast, but once I put it in the ground, it slows quite a bit because of the weight of the power pack - and that is also why I think a gear box is to the solution to make it go faster.

I feel the only path is to add more motors, but I am a bit lost on how to do that. Would adding two buggy motors in the same axle be a good idea?

Thanks a lot!

[2GodBDGlory]

48 minutes ago, Mpafr said:

Hey all, I am looking for suggestions on how to make my car go very very fast. 

I am currently using a buggy motor connected directly to the rear differential, to reduce loses. I am powering it with 3 x 3.7V, 3400 mAH, 18650 li ion, rechargeable batteries to give it some extra juice, and controlling it with an IR RC. 

Without any load the wheels go very fast, but once I put it in the ground, it slows quite a bit because of the weight of the power pack - and that is also why I think a gear box is to the solution to make it go faster.

I feel the only path is to add more motors, but I am a bit lost on how to do that. Would adding two buggy motors in the same axle be a good idea?

Thanks a lot!

Yeah, I think two buggy motors in an axle could work well!

Nice battery pack! I recently built myself one that's essentially the same, a 3S 18650 pack, which I've been using with two buggy motors, one on each rear wheel. One tip: Don't stack the buggy motor plugs, or the high current will likely melt out the plastic around the contacts!

[Carsten Svendsen]

On 12/1/2022 at 3:13 PM, Technic tango said:

How would I achieve motion like in this video:https://streamable.com/0t41k3 ? I already have a mockup on the side but i doubt it will be strong enough to lift the model, so i will likely need to get some more large linear actuators. Anyways, i would just like to know if anyone knows a way to make a linkage that can move in such a way shown in the video 

I usually search through thang's youtube for ideas in these cases: https://www.youtube.com/@thang010146/videos

Maybe something like this

 

Edited December 4, 2022 by Carsten Svendsen

[Mpafr]

10 hours ago, 2GodBDGlory said:

Yeah, I think two buggy motors in an axle could work well!

Nice battery pack! I recently built myself one that's essentially the same, a 3S 18650 pack, which I've been using with two buggy motors, one on each rear wheel. One tip: Don't stack the buggy motor plugs, or the high current will likely melt out the plastic around the contacts!

Nice!

Yes, I have experienced that problem with my PF plugs, I think 2 or 3 melted already. Changing them for more robust connectors is in my to-do list. 

1. Why did you decide to go with an independent motor per wheel? 
2. How are you controlling the motors? I am using 4 relays to isolate the control signal (low current) that comes from the IR sensor to the power signal (high corrent) that goes to the buggy.

Drive train wise, here are the desing options I can think of, but I am not sure on the (dis)advantages of each of them:

• 4WD - one buggy motor for each differential (front and rear).
• 2WD - one buggy per rear wheel
• 2WD - two buggy connected on the axle that goes to the rear or front differential

Appreciate any thoughts you have on it,

Thanks!

[2GodBDGlory]

2 hours ago, Mpafr said:

Nice!

Yes, I have experienced that problem with my PF plugs, I think 2 or 3 melted already. Changing them for more robust connectors is in my to-do list. 

1. Why did you decide to go with an independent motor per wheel? 
2. How are you controlling the motors? I am using 4 relays to isolate the control signal (low current) that comes from the IR sensor to the power signal (high corrent) that goes to the buggy.

Drive train wise, here are the desing options I can think of, but I am not sure on the (dis)advantages of each of them:

• 4WD - one buggy motor for each differential (front and rear).
• 2WD - one buggy per rear wheel
• 2WD - two buggy connected on the axle that goes to the rear or front differential

Appreciate any thoughts you have on it,

Thanks!

1. I decided to go with one independent motor per (rear) wheel because I wasn't using any differential, and having no mechanical connection between the wheels allows the inner wheel to be forced to rotate slower when steering. It's kind of a low-tech alternative to a differential that saves efficiency. I guess which drivetrain you go with will depend on your priorities for the car. If you just want it to go fast on level ground, I would probably suggest RWD with one motor per rear wheel. If you want to be able to do mild off-roading but still have lots of speed, I would go with RWD with the two rear motors hard-coupled on the axle. If you are willing to sacrifice more speed for off-road ability, then you could go with the 4WD, though if you're actually hoping to do more crawling, you might want to find a way to hard-couple both axles together, so that even if only the rear wheels have traction, they still get the torque of both motors.
2. That sounds like an interesting electric setup! Do I understand correctly that you're running a lower-voltage battery into the IR receiver, and then using relays attached to the receiver's output to control the motors from a higher-voltage battery? That's cool!
My setup is very custom and hacked-together. I've got:

1. Custom 3D-printed housing with 3 18650 cells wired in series
2. Controller board from an RC car (bought cheap from a place that sells replacement parts). It's not really a standard RC controller; it's just what came with this one car my brother had that was somewhere in between a cheap toy and an expensive hobby-grade car.
3. Two buggy motors wired through heavy-duty plugs I pulled from some old hoverboard parts
4. Controlled by the controller matching this circuit board

Then, my steering stuff is on a completely different circuit, because the 11-12V of my batteries seem to fry the servo control stuff on the control board! It has:

1. ~6V battery pack from this RC car system (Formerly 9.6V, but one of the three cells is dead)
2. Second, identical, controller board from this RC car system
3. PF L-motor connected to the positive and negative wires of the steering system
4. Position sensor from original RC car servo motor in 3D-printed case attached to steering system and the other three wires of the steering system. (This RC car had a non-standard servo system that would just read positions from a sensor and use that with a controller in the main board to tell a basic DC motor which direction to rotate)
5. Controlled by a second, identical controller, making this a two-handed job!

[Mpafr]

Thanks for the detailed reply. I will try two motors in the same axle and see where that takes me. 

5 hours ago, 2GodBDGlory said:

Do I understand correctly that you're running a lower-voltage battery into the IR receiver, and then using relays attached to the receiver's output to control the motors from a higher-voltage battery?

At first I thought I was going to need two battery packs, but in the end it worked well with just one. The power pack has two outputs, one for the IR receiver and one for the buggy. The IR receiver controls the relays that switch power to the buggy. This way the high current that is drawn by the buggy motor dont pass through the IR receiver.

Originally I had the servo motor connected directly to the IR receiver, but it started glitching too much, and it eventually burned. Having 11 V connected to it certainly did not help, but the current was kept low by the IR receiver, so I don't believe the 11 V was the root cause of the failure.

I see that you repplied to my thread asking for help with a steering solution, I will repply to you there about this part.

 

6 hours ago, 2GodBDGlory said:

My setup is very custom and hacked-together.

That is awesome! And you actually have two separate power packs! Lots of inspiration from your setup, thanks for the detailed description!

You might be able to get power from two 18650 for the steering stuff, saving the need for the secondary power pack.

[2GodBDGlory]

1 hour ago, Mpafr said:

Thanks for the detailed reply. I will try two motors in the same axle and see where that takes me. 

At first I thought I was going to need two battery packs, but in the end it worked well with just one. The power pack has two outputs, one for the IR receiver and one for the buggy. The IR receiver controls the relays that switch power to the buggy. This way the high current that is drawn by the buggy motor dont pass through the IR receiver.

Originally I had the servo motor connected directly to the IR receiver, but it started glitching too much, and it eventually burned. Having 11 V connected to it certainly did not help, but the current was kept low by the IR receiver, so I don't believe the 11 V was the root cause of the failure.

Oh, that's cool! So the receiver runs at 11V, but just low current.
Yeah, I don't think the 11V is going to kill a servo; people do that with Buwizz all the time.

1 hour ago, Mpafr said:

That is awesome! And you actually have two separate power packs! Lots of inspiration from your setup, thanks for the detailed description!

You might be able to get power from two 18650 for the steering stuff, saving the need for the secondary power pack.

Yeah, that's something to think about! The secondary pack isn't too big, but I can think about that. So far I just built one prototype buggy, and was just happy to get it all working! Though in testing it today a 3D-printed part that connects the Technic axle to the rotation sensor broke, so I'll have to reprint one (or several! It seems like an unavoidable weak point!)

[2GodBDGlory]

Now that I think about my setup more, I begin to wonder if I've made it more complicated than I need to. It might make sense to delete the whole steering circuit as I have it, and replace it with a simple PF servo + MouldKing 6.0 battery with proportional control. I could even hook up a relay to control the drive through this module as well from an external 11V battery, at the expense of proportional control for the drive.

[Mpafr]

On 12/4/2022 at 8:49 PM, 2GodBDGlory said:

Now that I think about my setup more, I begin to wonder if I've made it more complicated than I need to. It might make sense to delete the whole steering circuit as I have it, and replace it with a simple PF servo + MouldKing 6.0 battery with proportional control. I could even hook up a relay to control the drive through this module as well from an external 11V battery, at the expense of proportional control for the drive.

Can the servo motor actually work reliably? I have two here, both of them generic and new, both started to glitch in the second day of use. I have opened them, inspected the contacts, clenned (although they were not dirty).... one burned after I insisted on using it despite the glitches 

 

On 12/4/2022 at 12:35 PM, 2GodBDGlory said:

Custom 3D-printed housing with 3 18650 cells wired in series

 

The idea of having a custom made battery pack sounds awesome.

Both my power back and my relay box end up being much bulkier than needed.

I am switching all the high current circuit lego electrical connections to the ones you can below, to avoid melting more lego connectors.