Dog Bone Pin Orientation

[Steve B in Vegas]

Greetings all,

I have seen that some companies like Tekno and AE have their dog bones with pins on the same plane, while others like ARRMA pins are on perpendicular planes. Is this a timing issue? I was under the impression that dog bones, unlike U joints, don't have speed fluctuation issues.

Is there a reason to have a dog bone one way or the other?

s

 

[Billl DeLong]

Can you provide an illustration of the difference, not following what you are asking.

There is a big difference between CVD's and Universals where CVD's are better suited for smooth tracks and Universals are better for rough bumpy tracks.

 

[Steve B in Vegas]

Can you provide an illustration of the difference, not following what you are asking.

There is a big difference between CVD's and Universals where CVD's are better suited for smooth tracks and Universals are better for rough bumpy tracks.

If you see here, the Tekno drive shaft has pins on the same plane, where as ARRMA has them opposite.

Why? I can't find this answer anywhere.

 

[Billl DeLong]

I have never heard anyone mention this as a tuning option anywhere, I can't see any possible way that this would effect anything other than possibly how the part was manufactured that ARRMA might have a method to improve the "process" of the construction of the part that makes it easier when the opposing end is rotated by 90°, but from a functional point in use, I don't see how this makes any difference.

 

[Billl DeLong]

I did find an interesting discussion here which talks about the "planes of rotation" which is probably what you are interested in learning more about, though along the center shaft, any concern about this concept would be moot because there is no significant angle that is more applicable for moving steering spindles:
https://www.tamiyaclub.com/forum/index.php?/topic/85670-cvd-worse-than-dog-bones/

 

[Steve B in Vegas]

Bill,

I've read quite a bit on this topic, or rather read quite a bit that does not answer this topic. I did look over that link. What I find interesting is that I am also in manufacturing ( firearms ), and ever single step in production is purposeful. There are no random elements to our design.

With this, it's all about fixtures and process, but I can't see a way where rotating the driveshaft 90 degrees to drill the pin hole would make things faster or more efficient. It's at least one extra step on the machine and a few lines of code.

If they are being done manually, in that the holes are being drilled after the dog bone is made, in some kind of fixture, it would require two fixtures and more than likely two machines ( it's faster to set up multiple drill presses with a dedicated fixture than to swap them.

If it's automated, then it's another step, more code, and more chance for error.

My point is that I can't see this being random; there has to be a reason to make them like ARRMA. The version that Tekno / AE uses strikes me as first evolution of dogbone design, and the ARRMA as second evolution, all other things being the same. I would really like to know why.

s

 

[Skynet5]

Is it a flex thing? With them on the same plane with major flex they are more likely able to pop out. At opposing planes, less so?

 

[Steve B in Vegas]

Possibly. I think that's one idea to consider.

s

 

[Nicochau]

Check the Double Cardan shaft section:
https://en.wikipedia.org/wiki/Universal_joint

The Tekno dog bone is “in phase“ and the Arrma is “out of phase”. In movement there is more than a stable rotational movement and there seems to be a sinusoidal component that creates vibrations and possible stress or wear. The 90 deg “out of phase” configuration is supposed to reduce those vibrations.

In theory the Arrma dog bone is a better design. Considering the fact that the center drive shaft is more or less always at no angle, that sinusoïdal rotation speed should be minimized.

I’m in my bed now and too lazy to check the drive shafts. But I bet you the Tekno axles are out of phase too since they see a lot more angle due to the work of the suspension.

 

[Billl DeLong]

...I bet you the Tekno axles are out of phase too since they see a lot more angle due to the work of the suspension.

Yes, all CVD's are made to be out of phase which was shown in link #5 above, though I'm not sure these vibrations are relevant for center drive shafts when there are no moving angles like there are for independent suspension systems.

 

[Nicochau]

Yes, all CVD's are made to be out of phase which was shown in link #5 above, though I'm not sure these vibrations are relevant for center drive shafts when there are no moving angles like there are for independent suspension systems.

They shouldn’t for electric vehicle with a flat & centered driveline. Unless chassis flex is considered as introducing enough angle to matter, but I doubt it and Tekno designers seem too.

Some nitro buggies on the other hand have non-centered drivelines, in that case it may matter to reduce them. Arrma may have just inherited parts from other vehicles without too much rethinking the need.

 

[Steve B in Vegas]

So after digging around more, there are two ideas which seem most likely; one as you guys mentioned is the stability of the part when rotating.

The other which I also found interested is that ARRMA might be using this design to accommodate chassis flex. Having the pins "out of phase" would prevent binding on both ends of the shaft when the chassis flexes. Since ARRMA has an eye towards bashers, maybe the found that the drive shafts had less wear and damage with this design.

I'm running an ARRMA drive shaft in my Nomad DB-8, which comes standard with "phased" drive shafts. I want to be absolutely sure these work before I tell other people who read my Nomad page that the shafts work as a replacement. You can't find the factory AE drive shafts for this vehicle, and I consider that a critical part to have on had. I stumbled across the ARRMA shafts that work, and I hope the do, but this phase issue has been a real stumbling block.

I appreciate the comments and ideas. I ran the Nomad hard last night with 3 packs, and will inspect later today.

 

[Steve B in Vegas]

Check the Double Cardan shaft section:
https://en.wikipedia.org/wiki/Universal_joint

The Tekno dog bone is “in phase“ and the Arrma is “out of phase”. In movement there is more than a stable rotational movement and there seems to be a sinusoidal component that creates vibrations and possible stress or wear. The 90 deg “out of phase” configuration is supposed to reduce those vibrations.

In theory the Arrma dog bone is a better design. Considering the fact that the center drive shaft is more or less always at no angle, that sinusoïdal rotation speed should be minimized.

I’m in my bed now and too lazy to check the drive shafts. But I bet you the Tekno axles are out of phase too since they see a lot more angle due to the work of the suspension.

I just checked the Tekno axles, and they are a dog bone / CVA setup.

 

[Billl DeLong]

It is worth noting that the EB48 2.0 has made the rear center shaft a Universal Joint with the main pin out of phase, perhaps this is because the rear diff is slightly out of alignment, I have noticed that shaft tends to wear faster than any other shaft on my SCT410.3 and I typically replace the pins (on the rear-center shaft) about every 50 battery packs (on average) to prevent excessive wear on the out drives:

Pin Replacement Tools

I would be very much interested in learning if the wear on the pin is significantly reduced after the 2.0 upgrade, I will start to ask some of the team drivers in my area who are running the 2.0 buggy to see if they have noticed any difference since upgrading from the .4 version of the buggy.

 

[Steve B in Vegas]

Very interesting.

Question; where can I get high-quality 3mm drive shaft pins? I used some pins from our shop supply and I ate them up in 3 packs, so I think they are the wrong alloy. What are you using Bill?

s

 

[Billl DeLong]

Follow the link I provided above in post #14, in that thread I link to RC Renew which offers "hardened" pins, that's all I use these days for all my cars, I even use them in the CVD barrel pins for my PR Racing cars too!

 

[Steve B in Vegas]

Awesome. Got some on the way! Thanks Bill.

s

 

[Matthew_Armeni]

It is worth noting that the EB48 2.0 has made the rear center shaft a Universal Joint with the main pin out of phase, perhaps this is because the rear diff is slightly out of alignment, I have noticed that shaft tends to wear faster than any other shaft on my SCT410.3 and I typically replace the pins (on the rear-center shaft) about every 50 battery packs (on average) to prevent excessive wear on the out drives:

Pin Replacement Tools

I would be very much interested in learning if the wear on the pin is significantly reduced after the 2.0 upgrade, I will start to ask some of the team drivers in my area who are running the 2.0 buggy to see if they have noticed any difference since upgrading from the .4 version of the buggy.

Honestly the main reason for running the little uni is that if we used a dogbone the 2 drive cups would hit each other with the smallest amount of chassis flex.