GAZ 66K

[Tatrovak]

1 hour ago, gyenesvi said:

No worries, there's nothing offensive here, good to have a discussion with someone who understands the trade-offs in such designs. I think you see things quite similarly how I see them, in terms of possibilities and trade-offs. I agree that a steering system is most responsive if the servo is on the axle, and that the biggest challenge about the linkage based steering when the servo is off the axle is the clearance it requires (furthermore it requires a Panhard rod as well to be stable). However, I don't quite understand why a 4-link would be less stable and less usable for a heavier truck. In my experience it can be built quite stable, especially with stronger links (built from towball arms) and using a Panhard rod. Sure it is quite a bit more complicated than using the ball joint, but it's exactly that challenge that I am looking for when building them :) Also, what I found is that when the servo is on the axle, it requires a hole in the front of the chassis, and that makes it less rigid. When the servo is in there, it can be used as a structural element as well. But I understand we have different building styles / goals.

I'm glad, I appreciate the opportunity to discuss with you. One thing is steering, the other is power transmission, and that, for me, is the weakness of the four-pin mounting of the rigid axle, because it is necessary to use at least two CV joints on the drive shaft, plus some telescopic element, and these are, in my opinion, serious weaknesses of the drive system (of course as long as we are talking about heavy models, and for an idea, this GAZ is still light by my standards). Again, these are the conclusions I came to when building my models, and I admit that rigid axles are not my comfort zone and I will try to experiment more, because, for example, exactly as you write, placing the servomotor on the axle requires a large hole in the frame, even when specifically in the case of my GAZ, the problem is rather that the buwizz has to be higher so that the servomotor has somewhere to move when the axle is sprung, and this limits the interior of the cabin, which doesn't completely correspond to the original (the engine compartment cover is too big). And to complete the idea about power transmission, with an axle with a ball joint, only one CV joint is enough (of course, we do not count the other two necessary if the axle is steered), it is additionally strengthened by the ball joint and can bear a greater load than a solo , and it is excluded that under load it will slide out of the axles where it is stored, and this is especially true if the axle does not have reduction gears in the wheels.
Another thing is the larger space required by the arms of the four-pin suspension compared to the ball joint, both sides of which can be incorporated very well into the structure. And in short, it seems to me to be a very simple and effective solution which, if you set the geometry of the axle correctly, basically has no disadvantages compared to the four-pin suspension, since the bar for transverse stabilization is necessary in both cases.

2 hours ago, gyenesvi said:

I did not know that the real one also has some negative angle, good to note. I'm actually okay with using the ball-joint in the front when it is almost horizontal or only has a minimal amount of negative angle (what I don't like is steep negative angles). And trucks are better candidates for that.

Not to talk nonsense, it is not visible on the technical drawings that are available on the Internet, but I always had the feeling when I looked at pictures and videos that the wheels of the front axle on the GAZ 66 had such a very decent negative deflection.

 

2 hours ago, muffinbrick said:

Well, using buwizz or different tires is in "legal" category for me, because it don't directly influence, how is something build, it just add more power, or more authentic look. Cutting, or 3D printing, on the other hand can change directly building process - you can build, what would be impossible by original LEGO parts. In case of those planetary hubs it's bit of gray zone for me - you can use hubs without planetary reduction, which have needed shape, or you have planetary hubs, which have different shape of connection ports. It's pitty, that LEGO don't made those planetary hubs in shape of those from Audi q-tron. It would be problem solved.

It's really a shame, and I doubt that lego will ever bring an update of wheel hubs with planetary reduction, but it doesn't matter, I don't mind moving in gray zones that much.

 

 

[gyenesvi]

20 hours ago, Tatrovak said:

because it is necessary to use at least two CV joints on the drive shaft, plus some telescopic element, and these are, in my opinion, serious weaknesses of the drive system

Of course the ball joint gives extra stability, requires less space and is easy to work with, I totally see that. However, I was never convinced that the single U-joint in it, albeit being protected by the ball joint itself, is a sturdier solution than the double U-joints. I am always using new heavy duty CV joints, and they have less slack and are stronger than a U-joint. Also, the long male part is telescopic and still holds the axle very well due to its length. So I never had a problem with those, though I never built really heavy model, just medium, but I bashed it hard with Buwizz motors. Have you had any negative experience with those?

[Tatrovak]

On 12/14/2023 at 9:06 AM, gyenesvi said:

Of course the ball joint gives extra stability, requires less space and is easy to work with, I totally see that. However, I was never convinced that the single U-joint in it, albeit being protected by the ball joint itself, is a sturdier solution than the double U-joints. I am always using new heavy duty CV joints, and they have less slack and are stronger than a U-joint. Also, the long male part is telescopic and still holds the axle very well due to its length. So I never had a problem with those, though I never built really heavy model, just medium, but I bashed it hard with Buwizz motors. Have you had any negative experience with those?

The middle part of the U-joint is not strengthened by the ball joint in any way, but the ends of the U-joint into which the axles are inserted are tightly surrounded in such, let's call it, shafts that are inside the ball joint, because those U-joints always broke for me just at the ends, they cracked there, and from there the crack always spread to the center, causing the cracked part to split in two. I base this opinion on the fact that I have never had a U-joint fall apart in a ball joint, but maybe it's just my feeling, it's hard to say.
I admit that I don't have much experience with the new version of the CV joint, so I can't judge it, and I also admit that when I wrote the previous post, I forgot that they existed, because I admit, they look like they don't fall apart that easily. Of course, I use them as part of wheel hubs with planetary reduction, but I have never used them as joints on the cardan shaft. When they were presented on set 42099, I didn't like two things about them: firstly, the female part (it's in DBG color) has an axle 3 holes long, which didn't suit me because, for example, when used in a double wishbone axle, it forces me to extend it by two holes (I know that in the 42160 set, a newer version was introduced that has an axis one hole shorter, which eliminates the problem) and secondly, the CV-joint itself is larger and requires extra free space around it, so I still got these newer CV-joints did not buy. Are you asking about my experience with Buwizz RC motors?

[gyenesvi]

2 hours ago, Tatrovak said:

The middle part of the U-joint is not strengthened by the ball joint in any way, but the ends of the U-joint into which the axles are inserted are tightly surrounded in such, let's call it, shafts that are inside the ball joint, because those U-joints always broke for me just at the ends, they cracked there, and from there the crack always spread to the center, causing the cracked part to split in two. I base this opinion on the fact that I have never had a U-joint fall apart in a ball joint, but maybe it's just my feeling, it's hard to say.

Agree that a U-joint in the ball joint is probably less prone to break than when it is not protected that way.

2 hours ago, Tatrovak said:

I admit that I don't have much experience with the new version of the CV joint, so I can't judge it, and I also admit that when I wrote the previous post, I forgot that they existed, because I admit, they look like they don't fall apart that easily. Of course, I use them as part of wheel hubs with planetary reduction, but I have never used them as joints on the cardan shaft. When they were presented on set 42099, I didn't like two things about them: firstly, the female part (it's in DBG color) has an axle 3 holes long, which didn't suit me because, for example, when used in a double wishbone axle, it forces me to extend it by two holes (I know that in the 42160 set, a newer version was introduced that has an axis one hole shorter, which eliminates the problem) and secondly, the CV-joint itself is larger and requires extra free space around it, so I still got these newer CV-joints did not buy. Are you asking about my experience with Buwizz RC motors?

No, I was asking about experience with the new CV joints, but you answered it already. So I do think it is worth trying because I have really good experience with those, pretty sturdy ones (can withstand power of two coupled Buwizz motors) and not much slack. But you are right about the major down-side; it is bigger and that's a problem in many places. Also, they are limited with the axle lengths, so harder to incorporate, even though the recent addition of a shorter version in 42160 is really good, opens up new possibilities.

[2GodBDGlory]

4 hours ago, Tatrovak said:

I base this opinion on the fact that I have never had a U-joint fall apart in a ball joint, but maybe it's just my feeling, it's hard to say.

I've managed to repeatedly break U-joints in a ball joint, but that was in a stupidly overpowered design with four PF XL motors hard-coupled, running off an unrestricted 11.1+V battery, without nearly enough gear reduction beforehand. (Fortunately, metal U-joints are available, but unfortunately, my problems moved downstream. Knob wheels and 3L axles aren't as strong as you'd think!)

Not exactly a typical situation, though!

[Tatrovak]

2 hours ago, gyenesvi said:

Nie, pýtal som sa na skúsenosti s novými kĺbmi CV, ale už ste odpovedali. Takže si myslím, že to stojí za vyskúšanie, pretože s tými mám naozaj dobré skúsenosti, sú dosť robustné (vydržia silu dvoch spojených motorov Buwizz) a nie sú príliš voľné. Ale s hlavnou nevýhodou máte pravdu; je väčší a to je na mnohých miestach problém. Sú tiež obmedzené dĺžkou náprav, takže je ťažšie ich začleniť, aj keď nedávne pridanie kratšej verzie v 42160 je naozaj dobré, otvára nové možnosti.

I am going to try to build a three-axle chassis with rigid axles, and for the rear two-axle I plan to experiment a bit with a solution other than ball joints, since this solution did not work so well for me there.

 

1 hour ago, 2GodBDGlory said:

Podarilo sa mi opakovane zlomiť U-kĺby v guľovom kĺbe, ale to bolo v hlúpo prehnanom dizajne so štyrmi motormi PF XL napevno spojenými, napájajúcimi neobmedzenú 11,1 + V batériu, bez takmer dostatočnej redukcie vopred. (Našťastie sú k dispozícii kovové U-kĺby, ale žiaľ, moje problémy sa presunuli smerom po prúde. Kotúčové kolesá a 3L nápravy nie sú také pevné, ako si myslíte!)

Nie je to však úplne typická situácia!

Were wheel reduction gears used on that model? wheel hubs with planetary or portal reductions?

[2GodBDGlory]

5 hours ago, Tatrovak said:

Were wheel reduction gears used on that model? wheel hubs with planetary or portal reductions?

Yeah, I had portal reduction in custom hubs, but it was still too much power!
This is the topic, if you're interested:
 

Spoiler

 

 

[Tatrovak]

I looked at the topic about your Lada, I like the design of your body, at first glance I recognized the Niva in it. As far as my opinion is concerned, I think you definitely did well to throw out the two-speed gearbox, I am an opponent of gearboxes, in my opinion they are just a source of unnecessary mechanical resistance, they are unreliable, increase the weight of the model and take up a lot of space, although I admit that I have this opinion because I don't know how to assemble a good gearbox. Maybe it's just a bit of a shame that you didn't stick to the original, the LADA Niva has independent suspension on the front axle, the rigid axle is only at the back. Anyway, I'm glad that someone from such a distant country as Canada knows a machine from us, from the former Eastern bloc.

[2GodBDGlory]

6 hours ago, Tatrovak said:

I looked at the topic about your Lada, I like the design of your body, at first glance I recognized the Niva in it. As far as my opinion is concerned, I think you definitely did well to throw out the two-speed gearbox, I am an opponent of gearboxes, in my opinion they are just a source of unnecessary mechanical resistance, they are unreliable, increase the weight of the model and take up a lot of space, although I admit that I have this opinion because I don't know how to assemble a good gearbox. Maybe it's just a bit of a shame that you didn't stick to the original, the LADA Niva has independent suspension on the front axle, the rigid axle is only at the back. Anyway, I'm glad that someone from such a distant country as Canada knows a machine from us, from the former Eastern bloc.

Thanks! I do like gearboxes in off-roaders to allow for decent speed but also good crawling, but they definitely do have disadvantages, and I'd agree that they're not worth it for fast, on-road vehicles.

It could have been more realistic with independent front suspension, but I didn't think I'd be able to achieve the level of off-road performance I was going for with that setup, unfortunately.

Yeah, I am far away from that Lada's homeland! Interestingly, we did have that vehicle sold here back in the day, unlike in the US, but I'm too young to remember seeing any, except for one I spotted in a junkyard a few years back.

[Tatrovak]

As far as I know, in my country at one time (mainly the turn of the 80s and 90s) there were quite a few of them, I think it was a favorite car, especially among hunters, but I know that, for example, the police also used it, but those cars have almost disappeared, and despite the fact that they are still produced with certain changes and, as far as I know, they can be bought here as new.

[Pufarine]

On 12/10/2023 at 11:20 AM, 1gor said:

I'm just looking how to make 2 studs more narrow steering axle with planetary hubs...

This one is a bit wobly...

This is my take for a front axle, for a small terain vehicle.

 

Sorry for the offtopic.

[1gor]

1 hour ago, Pufarine said:

This is my take for a front axle, for a small terain vehicle.

 

 

Sorry for the offtopic.

Thanks for help, but I'm looking how to use reduction hubs