[HELP] Generic Building Help Topic

[StudWorks]

@2GodBDGlory and @Jurss thanks for the advice, I found a solution similar to 2GodBDGlory's that worked out perfectly.

Now on my EV3 car I'm having an issue with driving, the CV-joints connected to the differential are dislocating and being damaged to the point where they're no longer usable.

I found a possible solution using fresh undamaged CV-joints and bushes, so the CV-joint could be held on tight...

...but I'm concerned that the dislocating will continue and the undamaged CV-joints will become damaged.

Any 1:8 car builders who found a way to prevent CV-joint dislocation and damage? I tried seeing what other motorized 1:8 scale Technic car builders did to prevent this, but I can't find any good images.

Edited December 31, 2021 by StudWorks

[2GodBDGlory]

3 hours ago, StudWorks said:

@2GodBDGlory and @Jurss thanks for the advice, I found a solution similar to 2GodBDGlory's that worked out perfectly.

Now on my EV3 car I'm having an issue with driving, the CV-joints connected to the differential are dislocating and being damaged to the point where they're no longer usable.

I found a possible solution using fresh undamaged CV-joints and bushes, so the CV-joint could be held on tight...

 

...but I'm concerned that the dislocating will continue and the undamaged CV-joints will become damaged.

Any 1:8 car builders who found a way to prevent CV-joint dislocation and damage? I tried seeing what other motorized 1:8 scale Technic car builders did to prevent this, but I can't find any good images.

Hmm, I've got three thoughts about that:

1. I personally usually use universal joints on the top half of the half-shaft, since they can't come apart. New HD CV joints would work well, too, if they fit.

2. If you want to fine-tune the length of the axle further to keep it tight, you could try using some of the old toothed half-bushes in various combinations, because two of them meshed with each other are a little less than a stud in length.

3. Likely this is just a trick of the eyes, but when I look at your suspension setup, it kind of looks like your upper suspension link is a half-stud above the CV joint rather than a full stud. If this is correct, causing the CV joint axle to not (always) be parallel with the suspension links, it's length could be changing throughout the suspension travel, giving it opportunities to fall apart.

Hopefully something here helps!

[StudWorks]

@2GodBDGlory Thanks for the reply, I found the main issue:

When operating under high torque, the CV-joint light grey piece bends and grinds into the dark grey piece, diminishing the two pieces' binding ability (I broke this fresh new CV-joint just to test this).

I see builds all the time of 1:8 scale vehicles using the new BuWizz motor and I never hear of them destroying CV-joints like my 1:8 scale car currently does. Still looking for a solution.

[Zerobricks]

I suggest you use the stronger CV joints which came out with 42099. I have yet to break any.

[StudWorks]

37 minutes ago, Zerobricks said:

I suggest you use the stronger CV joints which came out with 42099. I have yet to break any.

Thanks, they don't fit in the suspension/wheel hubs I'm using currently though. You had a big role in the record-breaking Spania BuWizz supercar, right? I'm curious if you used the small CV-joints in that build. I also tried seeing what Lox Lego uses in his creations (without buying instructions) to transmit power from diff to wheel hub, but I couldn't find anything.

[Zerobricks]

2 minutes ago, StudWorks said:

Thanks, they don't fit in the suspension/wheel hubs I'm using currently though. You had a big role in the record-breaking Spania BuWizz supercar, right? I'm curious if you used the small CV-joints in that build. I also tried seeing what Lox Lego uses in his creations (without buying instructions) to transmit power from diff to wheel hub, but I couldn't find anything.

I used the big CV joints for the drive as anything else would fail instantly with such a heavy model and so much power.

[allanp]

42 minutes ago, StudWorks said:

@2GodBDGlory Thanks for the reply, I found the main issue:

When operating under high torque, the CV-joint light grey piece bends and grinds into the dark grey piece, diminishing the two pieces' binding ability (I broke this fresh new CV-joint just to test this).

I see builds all the time of 1:8 scale vehicles using the new BuWizz motor and I never hear of them destroying CV-joints like my 1:8 scale car currently does. Still looking for a solution.

@Zerobricks is right, try using the 42099 CV joints. As for others not having this issue, it's hard to tell for sure but @2GodBDGlory may be right with your positioning of the CV joint being half a stud off (that's how it looks to me also), meaning the drive shaft will want to move in and out as the suspension moves. Yes you have s frictionless CV joint which should allow for that, however it's only really frictionless when there isn't any torque going through the shaft. Others might also be employing some other tricks, such as fine tuning the length with shims of paper, or just not admitting to any breaks.

[StudWorks]

@Zerobricks I would buy some on BrickLink right away, but I wanted to try something.

I remember I saw someone ( @Didumos69 maybe?) use a 3x3 fork piece in their MOC's suspension arms to prevent clicking/damage, I really want to see the original image I got this idea from so I could implement it into my MOC.

[Didumos69]

1 hour ago, StudWorks said:

I remember I saw someone ( @Didumos69 maybe?) use a 3x3 fork piece in their MOC's suspension arms to prevent clicking/damage, I really want to see the original image I got this idea from so I could implement it into my MOC.

I believe that was in a post by @PorkyMonster.

These days you could also use something like:

Btw, for the new CV-joints it might be useful to know that you can work with parts around the CV-joint on a diagonal grid:

 

Edited January 1, 2022 by Didumos69

[StudWorks]

@Didumos69 Thanks for the reply. I did what you showed on your second picture, but the clicking/CV-joint grinding still occurs under high torque.

I'm questioning whether I should get the new CV-joints or, what I prefer, doing what people have been doing for years before the new CV-joint was released.

If there's no solution I'll just have to live with this. BTW the car is driven by two EV3 large motors driving a knob gear. There could be the possibility the knob gears are causing the extreme torque required to damage CV-joints.

[Didumos69]

5 minutes ago, StudWorks said:

@Didumos69 Thanks for the reply. I did what you showed on your second picture, but the clicking/CV-joint grinding still occurs under high torque.

The way the 5L beams that brace the male part of the CV-joint could be mounted to the 5x7-frame better. Right now this relies on the pins with pinholes, which may be pulled out a little. These pins with pinholes are friction locked, not form locked. It would be better if you can somehow use vertically placed 3L pin with pinholes (the same piece you use to connect the 5L beams and hold the drive axle) and mount them to the 5x7-frame such that the structure relies on pulling pins sideways instead of lengthwise.

15 minutes ago, StudWorks said:

I'm questioning whether I should get the new CV-joints or, what I prefer, doing what people have been doing for years before the new CV-joint was released.

The issue you're running into is not new. Many people have had problems with combining CV-joints with RC, even with plain PF parts.

I don't know your build, but as a rule of thumb I would say: If your model is about speed, I would keep the old CV-joints, lower torque and increase RPM by gearing up the output of the motors. If your model is about trial or crawling, I would use the new CV-joints and the new portal hubs. And also in this case, you probably want to increase RPM by gearing up the output of the motors. That will reduce torque in your drivetrain and somewhat compensate for the gear reduction in the portal hubs.

For increased RPM and lower torque in your drivetrain to be an option, it's important to have a drivetrain with low friction. Maybe those knob wheels are a source of friction, I don't know. You could try with different gears and check what happens.

[Hrafn]

@StudWorks instead of the pins-with-hole, try the piece I use as a profile pic - it can be locked to the 5x7 frame with 2L axles.

[StudWorks]

@Didumos69 and @Hrafn I tried Hrafn's solution and the popping still occured.

I discovered that it doesn't matter how much I reinforce the CV-joint, the popping will always occur under torque.

And Didumos, I can't gear up the motor output because having a speed gear ratio over 1:1 results in failure to drive in big PF/Buwizz RC cars and the model is pretty heavy (little heavier than the Sian set) and the motors have a problem even moving. Are you sure about gearing up with something like a 20 teeth gear moving a 12 teeth half-gear? (I worry about the half gear clicking/breaking)

The chassis is based off @Jeroen Ottens's DB11, which doesn't have PF/Buwizz RC.

Thanks for your time, again.

Edited January 2, 2022 by StudWorks

[Didumos69]

8 hours ago, StudWorks said:

@Didumos69 and @Hrafn I tried Hrafn's solution and the popping still occured.

I discovered that it doesn't matter how much I reinforce the CV-joint, the popping will always occur under torque.

And Didumos, I can't gear up the motor output because having a speed gear ratio over 1:1 results in failure to drive in big PF/Buwizz RC cars and the model is pretty heavy (little heavier than the Sian set) and the motors have a problem even moving. Are you sure about gearing up with something like a 20 teeth gear moving a 12 teeth half-gear? (I worry about the half gear clicking/breaking)

The chassis is based off @Jeroen Ottens's DB11, which doesn't have PF/Buwizz RC.

Thanks for your time, again.

I fear your model is either too heavy or there is some friction going on somewhere between the motors and the wheels.

I used a 90 degree thin 12t gear vs thin 12t gear mesh in my recent 42129 b model without problems, also with a 1:1 drive ratio (the bracing had to be perfect to make that work). But that was with PU parts.

[StudWorks]

@Didumos69 That's interesting... after reinforcing gears that were clicking I found you're probably right. Is the model too heavy?

The car will be almost 6 pounds when completed. It's powered by one EV3 brick and two large EV3 motors.

I'm going to try gearing down the input from the motors.

Edited January 6, 2022 by StudWorks
More information

[Fluwoeb]

I have a question, is it possible to use a PF extension cord to connect to PF battery boxes and effectively double or connect the voltage of the boxes?

[pleegwat]

@Fluwoeb IIRC you need to involve old 9V components to put the batteries in series. This is not a good idea, since the resulting voltage is likely to burn out your motors.

Edited January 7, 2022 by pleegwat

[2GodBDGlory]

Take a look at this thread; it should have plenty of info for you!

 

[Fluwoeb]

Thank you @pleegwat and @2GodBDGlory! I will look into the post you linked and yes, it will double the voltage if I connect battery boxes using the old 9V components.

[Jurss]

Is it possible in LDD or Studio to change extension of linear actuator? I tried, but didn't managed. In LDD it is halfway extended. In Studio in shortest position.

[Zerobricks]

4 minutes ago, Jurss said:

Is it possible in LDD or Studio to change extension of linear actuator? I tried, but didn't managed. In LDD it is halfway extended. In Studio in shortest position.

Yes if you use the community updated version.

[Jurss]

1 minute ago, Zerobricks said:

Yes

Studio or LDD?

Interesting, when I imported in Studio that small lienear actuator from LDD in extended position, it is also extended in Studio.

[Zerobricks]

Just now, Jurss said:

Studio or LDD?

Interesting, when I imported in Studio that small lienear actuator from LDD in extended position, it is also extended in Studio.

LDD, please check here:

 

[Jurss]

2 minutes ago, Zerobricks said:

please check here

Thank You!

[Jurss]

@Zerobricks it is sufficient to download latest pack?