[HELP] Generic Building Help Topic

[NoEXIST]

Hello! I would like to try my hand at building a 1:8 supercar. I have a lot of questions about model selection, drawing selection, sizing, and trade-offs to make for good appearance.

 

The main question I have is ground clearance, on most blueprints I saw it's about 2 studs in 8th scale.

What do you change in the models so that in the final model the clearance is about 1 stud and does this create a big difference from the original?

[Technic tango]

How would one create 3D pdf instructions? I saw this one moc on rebrickable Here that used adobe acrobat.  Did this person manually export a mesh for every step or is there a method to do this with blueprint or ldcad that im not aware of?

[2GodBDGlory]

7 hours ago, NoEXIST said:

Hello! I would like to try my hand at building a 1:8 supercar. I have a lot of questions about model selection, drawing selection, sizing, and trade-offs to make for good appearance.

 

The main question I have is ground clearance, on most blueprints I saw it's about 2 studs in 8th scale.

What do you change in the models so that in the final model the clearance is about 1 stud and does this create a big difference from the original?

This might not answer your question, but I'd imagine keeping two studs is worth it to have a little suspension travel.

[ukbajadave]

How would you clever people connect this motor to the horizontal beam?

The ends of the T rub on the wheel. I want a piece like this...

I'm working on a powered up Forklift. Is it worth a WIP thread to ask this sort of stuff?

[Jurss]

Use beams this way (if I understood correctly)

[ukbajadave]

22 hours ago, Jurss said:

Use beams this way (if I understood correctly)

Thank you, you understood correctly and I couldn't see this simple solution. Sometimes I wonder if I make stuff too complicated 

[Jurss]

I just don't like much, that connection with one (two) pins. Maybe try to add additional beams in middle of chassis, or on top.

[pleegwat]

I'd see if I could lengthen the black horizontal bars behind by a module or two toward the motor to get more overlap between the beams. Only one pin overlap feels iffy. I don't have it in my hands though, and it may well be fine in practice as-is.

[SJMarty]

Hello,

I'm building the 42145 Airbus H175 Rescue Helicopter.  On step 142, the instructions show inserting a red pin with axle through two narrow beams, through a wide beam, and in step 143, placing a pinion on the axle end and another pinion on the axle beneath it.  After installing both pinions, the longer axle is almost impossible to turn due to the friction from the red pin with the axle end holding the pinion above it.  Before continuing, I want to make sure this is correct as it doesn't seem right.

Thank you!

[2GodBDGlory]

28 minutes ago, SJMarty said:

Hello,

I'm building the 42145 Airbus H175 Rescue Helicopter.  On step 142, the instructions show inserting a red pin with axle through two narrow beams, through a wide beam, and in step 143, placing a pinion on the axle end and another pinion on the axle beneath it.  After installing both pinions, the longer axle is almost impossible to turn due to the friction from the red pin with the axle end holding the pinion above it.  Before continuing, I want to make sure this is correct as it doesn't seem right.

Thank you!

Welcome to Eurobricks!

I'm pretty sure that should be fine. It might be hard to rotate that long red axle right now by grabbing the axle, but if you pull on the center lever (or the other one that isn't installed at this point in the build) you should have significantly more leverage to get it moving.

That's a great set you're working on!

[SJMarty]

2 hours ago, 2GodBDGlory said:

Welcome to Eurobricks!

I'm pretty sure that should be fine. It might be hard to rotate that long red axle right now by grabbing the axle, but if you pull on the center lever (or the other one that isn't installed at this point in the build) you should have significantly more leverage to get it moving.

That's a great set you're working on!

Thanks for the quick reply.  I pushed a few steps further and I'll tell you, it still doesn't seem right.  I recently purchased the 9396 set and ironically ran into this same type of issue with the winch.  The instructions called for a friction pin with a stop bushing on one end.  This configuration prevented the reel from turning.  I ended up replacing the friction pin with an axle and this resolved that issue.  I found this posting (after-the-fact) that called for the same solution.

My hesitancy to proceed is if something similar has to be done with the Airbus, I'm afraid the whole assembly is going to have to be torn down.

[vascolp]

Don´t hesitate  ! The friction pin is there exactly to avoid the mechanism to be too loose. Otherwise the weight of the mecanism would make it return to the lower position.

Chek it in this video, for instance.

Compared with 9396 winch, this is way more complex... one of the things that makes this set amazing!

Have a nice build!

[SJMarty]

Thanks for the help and link.  Pressing on!

[anyUser]

On 1/21/2023 at 5:40 PM, SJMarty said:

After installing both pinions, the longer axle is almost impossible to turn due to the friction from the red pin with the axle end holding the pinion above it.

Hello,

I had the same impression and wrote about is some time ago.
There were a few remarks on that.

[Reisess]

Hi

I have some problem to make my car properly drive .

So I'm using 7,4V 25C LiPo package with sBrick. About gearing I'm using 2x lego 5292 (sadly not original one but replacement) on one axle, they goes through 2x 16th (so 1:1) to gearbox with 1:1 and 1,67:1 and then to differentials so 1,4:1.

The main problem is to start this stuff, cause if it even start at begining it looks like bunny jumps (I have to use 100% throttle to do this), but in most cases I only hear squeak's from engines and it won't start. Ofc If I use reverse, then forward few times it finally start ride but it should not looks like that . Also I checked if whole drivetrain move fine from finger (placed when engines are) and I don't find any issues here.

I'm not sure if problem appear cause of bad gearing, or some electric issues.

[Jurss]

If not mistaken, lego 5292  needs 9V. As there ar two, they will draw much power, so in best case there will be 7V, so it means -22% of needed voltage. That is a lot.

[2GodBDGlory]

2 hours ago, Reisess said:

Hi

I have some problem to make my car properly drive .

So I'm using 7,4V 25C LiPo package with sBrick. About gearing I'm using 2x lego 5292 (sadly not original one but replacement) on one axle, they goes through 2x 16th (so 1:1) to gearbox with 1:1 and 1,67:1 and then to differentials so 1,4:1.

The main problem is to start this stuff, cause if it even start at begining it looks like bunny jumps (I have to use 100% throttle to do this), but in most cases I only hear squeak's from engines and it won't start. Ofc If I use reverse, then forward few times it finally start ride but it should not looks like that . Also I checked if whole drivetrain move fine from finger (placed when engines are) and I don't find any issues here.

I'm not sure if problem appear cause of bad gearing, or some electric issues.

So, if I understand correctly, you're saying that trying to start the car results in either a slow, jerky start, or just stalling/power cutting?

The gearing you have sounds fairly reasonable, unless your car is fairly heavy, in which case you might want to try gearing for more torque.

Are you using only one SBrick, though? I've never used them, but most models I've seen use at least one SBrick per buggy motor, so that might be limiting your current output quite a bit.

25 minutes ago, Jurss said:

If not mistaken, lego 5292  needs 9V. As there ar two, they will draw much power, so in best case there will be 7V, so it means -22% of needed voltage. That is a lot.

Well, I wouldn't say that motor needs 9V. That's what it originally ran on in official sets (until the batteries started to die), but I've ran them at 7.4V lots of times without trouble. Also, it sounds like a torque problem, and cutting voltage affects speed a lot more than torque, if I'm not mistaken. I wouldn't be surprised if it is a current supply issue, though, because those motors require pretty beefy electronics backing them up.

[Reisess]

2 hours ago, 2GodBDGlory said:

So, if I understand correctly, you're saying that trying to start the car results in either a slow, jerky start, or just stalling/power cutting?

Yea excatly.

2 hours ago, 2GodBDGlory said:

Are you using only one SBrick, though? I've never used them, but most models I've seen use at least one SBrick per buggy motor, so that might be limiting your current output quite a bit

I unplug one of them from power and axle, and now it works like it should, so yea probably one SBrict is not enought for 2x buggy motors, that's sad cause when I was buying that SBrick I found somwhere info that it can handle both alone, well they lied to me . Thanks for help :.

[glowytheglowbug]

7 hours ago, Reisess said:

Yea excatly.

I unplug one of them from power and axle, and now it works like it should, so yea probably one SBrict is not enought for 2x buggy motors, that's sad cause when I was buying that SBrick I found somwhere info that it can handle both alone, well they lied to me . Thanks for help :.

i am pretty sure sbrick can handle a few buwizz/buggy motors its just your power source eg if you use a PF battery box the power might cut out ive seen people power their sbrick with lipos too be careful though you dont want lipo fires


Tamás Fábián said:

Hello Ray,

the absolute maximum value is 11.8 Volts. This comes from the datasheet of the integrated circuit we use for driving the outputs (DRV8833). The safe operating limit is 10.8 for the same IC.

Having said that, we managed to overvolt SBricks up to 14 volts and never damaged a single one. However, do not take this as a recommendation. It's a bit like overclocking / overvolting CPUs and memory modules in a PC. Be aware that overvolting your SBrick beyond the absolute maximum voids your warranty.

What you can do is:

• Play safe, and don't run the SBrick over 10.8V
• Accept some extra heating and reduced safety margin, and go near the absolute maximum limit of 11.8V
• Accept the chance of immediately and permanently damage or severely reduce the lifespan of your SBrick, and run it over the absolute maximum of 11.8V.
• Use a 3-cell Lithium Iron Phospate (LiFePo4) battery. With a maximum cell voltage of 3.65V it just barely goes over the recommended operating limit of 10.8V, and stays well below the absolute maximum.

Ray Simon said:

Thanks Lenard! I have a follow up question: Is it safe to connect a fully charged three-cell LiPo directly to the SBRICK Plus? I'm sure when the battery levels off to nominal voltage of 11.1V it is safe. The question is if the initial voltage of 12.6V will harm the SBRICK.

I would like to use my hobby-grade 3S LiPo batteries with the SBRICK Plus. These are standard three-cell LiPo used for RC cars, airplanes, helicopters, etc. The behavior of these batteries is that at full charge, the voltage is 12.6V without load. After load is applied and some current draw, the voltage drops and levels off to "operating" or "nominal" voltage which is 11.1V.

I have been researching other options to use my 3S LiPo batteries and you can get a DC-to-DC mini voltage regulator, but generally the output must be at least 1.5V below the input voltage, which means it would need to be set to about 9V to be safe to handle the LiPo as the voltage drops while it is discharged. This is possible but requires more complexity and equipment. It would be much simpler if we can connect the LiPo directly to the SBRICK.

Thanks for your support! (https://social.sbrick.com/forums/topic/5/max-current-rating)

Edited February 3, 2023 by glowytheglowbug

[Reisess]

8 hours ago, glowytheglowbug said:

i am pretty sure sbrick can handle a few buwizz/buggy motors its just your power source eg if you use a PF battery box the power might cut out ive seen people power their sbrick with lipos too be careful though you dont want lipo fires

Quote

So I'm using 7,4V 25C LiPo

So this one could be too weak to power that two motors? 

[2GodBDGlory]

5 hours ago, Reisess said:

So this one could be too weak to power that two motors? 

Is that from some hobby-style RC car? If so, I don't think you should be having any problem.

[Reisess]

On 2/3/2023 at 3:01 PM, 2GodBDGlory said:

Is that from some hobby-style RC car? If so, I don't think you should be having any problem.

Yea exactly. Also I borrow 3S package (so around 11,1V output) and on that package it has no chance to even start ride. So to summirize:

• 3S (11,1 v) - not even start on one/both motors
• 2S (7,4v) - start sometimes on both, start often on one motor
• Normal battery from lego box - start on both/one but with very limited power and speed

So... I have no idea wtf is wrong here 

[2GodBDGlory]

34 minutes ago, Reisess said:

Yea exactly. Also I borrow 3S package (so around 11,1V output) and on that package it has no chance to even start ride. So to summirize:

• 3S (11,1 v) - not even start on one/both motors
• 2S (7,4v) - start sometimes on both, start often on one motor
• Normal battery from lego box - start on both/one but with very limited power and speed

So... I have no idea wtf is wrong here 

I'm still thinking it's the fact that you've only got one SBrick, but that's just from judging from what I've seen others do.

[Reisess]

6 minutes ago, 2GodBDGlory said:

I'm still thinking it's the fact that you've only got one SBrick, but that's just from judging from what I've seen others do.

Yea probably I have to buy second one, but maybee somebody send here some Einstein idea 

[2GodBDGlory]

2 minutes ago, Reisess said:

Yea probably I have to buy second one, but maybee somebody send here some Einstein idea 

Well, I suppose there's always the option of abandoning Lego-style controllers like that and just using hobby-style controllers, but that gives up a lot in easy compatibility, and might not be a whole lot cheaper to get into.