New differentials, are they THAT good?

[HectorMB]

Everyone liked the new differentials (65413 & 65414). The 28 tooth is great and the 5 bevel gears inside promise a lot of possibilities. They can be also locked, which is great. Nevertheless, I'm having some issues (and thoughts after them) when using them under high torque (which is the main use for these ones, I think). The thing is that when subjected to high torque, both parts partially disassemble, probably not even 1 mm, but enough for give room for the 12 tooth bevel gears inside to slip and crack. I tested several of these ones, and the issue seems consistent...

 

Has someone else experienced something similar? 

Edited October 5, 2021 by HectorMB

[Maaboo the Witch]

Strictly speaking from my own observations, I haven't noticed them performing any better than the previous versions.

[Jurss]

1 hour ago, HectorMB said:

under high torque (which is the main use for these ones, I think)

Don't forget that this is still a toy, not and specific RC car set.

[allanp]

1 hour ago, HectorMB said:

Everyone liked the new differentials (65413 & 65414). The 28 tooth is great and the 5 bevel gears inside promise a lot of possibilities. They can be also locked, which is great. Nevertheless, I'm having some issues (and thoughts after them) when using them under high torque (which is the main use for these ones, I think). The thing is that when subjected to high torque, both parts partially disassemble, probably not even 1 mm, but enough for give room for the 12 tooth bevel gears inside to slip and crack. I tested several of these ones, and the issue seems consistent...

 

Has someone else experienced something similar? 

I haven't noticed this issue. Are you using them inside the 5x7 or 5x11 frames?

[Gray Gear]

@allanp good point I think using then inside a frame (one brick, not a built frame) is crucial to stop them from expanding. Still kind of disappointing this is a problem 

[Hrafn]

1 hour ago, Gray Gear said:

@allanp good point I think using then inside a frame (one brick, not a built frame) is crucial to stop them from expanding. Still kind of disappointing this is a problem 

Disappointing but not entirely surprising.  To avoid the problem, the housing and red gear would have to be joined by radial pins or something similar that would prevent separation.  

[nerdsforprez]

2 hours ago, Gray Gear said:

@allanp good point I think using then inside a frame (one brick, not a built frame) is crucial to stop them from expanding. Still kind of disappointing this is a problem 

Not sure we have concluded this is actually a problem.  When braced properly.  Like @allanp I have not noticed a problem either.  

[pleegwat]

They also do not have gears fall out if you pull out one of the axles.

[Gray Gear]

@nerdsforprez yeah true, I meant it is disappointing the diff will try to split in the first place. But with just a click connection that has to open again it is unavoidable with enough power I guess. 

@pleegwatthat's a good point. Not that much of a bother for me, but some people might find this very helpful.

[HectorMB]

4 hours ago, allanp said:

I haven't noticed this issue. Are you using them inside the 5x7 or 5x11 frames?

They are housed in a built frame ( a 11x5 with a 9L liftarm to make the sandwich. I put a lot of effort in making it studry, but with no real improvement.

2 hours ago, Hrafn said:

Disappointing but not entirely surprising.  To avoid the problem, the housing and red gear would have to be joined by radial pins or something similar that would prevent separation.  

Not really. There are few solutions, from the tip top one, which would be a closed differential with not detachable parts, analogous to the planetary hubs, to just making the 24 bevel gear to fit way tighter than they currently do. Also, I found a custom solution which is to introduce three small plastic pieces to secure both pieces together. Nevertheless, the vibration and high torque makes them to fall out. 

1 hour ago, nerdsforprez said:

Not sure we have concluded this is actually a problem.  When braced properly.  Like @allanp I have not noticed a problem either.  

In my opinion, if the differential need to be in a 5x7 frame to be functional is not a nice alternative. There are many applications to the differential that are just incompatible with such set up. 

Besides all that, I have to say that I am also disappointed with these ones. I thought that they were made precisely to be able to take a considerable torque, but I am not sure if the fact that they are made of two pieces (plus the bevel gears) adds or takes robustness. 

[Void_S]

14 minutes ago, HectorMB said:

In my opinion, if the differential need to be in a 5x7 frame to be functional is not a nice alternative. There are many applications to the differential that are just incompatible with such set up. 

Well, I suppose all the gear connections must be embraced accordingly to handle high torque. Otherwise, they will skip and click, no matter if they are differentials, bevel-angled, or normal gears.

Have you tested the same setup but with a normal differential? I guess the "have-duty" application of the new one is to not to be damaged under the high torque, first of all, while the old one will chew its single-bevel thin crown quite easily.

[HectorMB]

1 minute ago, Void_S said:

Well, I suppose all the gear connections must be embraced accordingly to handle high torque. Otherwise, they will skip and click, no matter if they are differentials, bevel-angled, or normal gears.

Have you tested the same setup but with a normal differential? I guess the "have-duty" application of the new one is to not to be damaged under the high torque, first of all, while the old one will chew its single-bevel thin crown quite easily.

Yes, that's a fair point. Nevertheless, these differentials have two weak points that make them not that suitable for high torque applications; they may be dissasembled in two pieces and the axles still depend on the attachment to the 12-tooth bevel gears. 

At the end, they are what they are. After this experience, for me, they are just other differential, with some small improvements respecting the previous diffs, but lacking a true significant improvement (such, for example, what the planetary hubs have done). 

Regarding the use of other diffs. This is indeed one of my possible future approaches, but I wanted to exploit the 24 bevel gear...

[Void_S]

I just tested some assemblies and the crown and holder parts start moving (slightly) only when the axle which rotates it, was about to be twist-broken.

Just wanted to highlight that my "new heavy-duty" differentials keep the parts assembled so hard, so I think I can't disassemble them with no screwdriver or other tools (like PF or PU motor cases). May I propose that yours can be disassembled even manually, e.g. lost its "connection strength"?

[HectorMB]

1 minute ago, Void_S said:

I just tested some assemblies and the crown and holder parts start moving (slightly) only when the axle which rotates it, was about to be twist-broken.

Just wanted to highlight that my "new heavy-duty" differentials keep the parts assembled so hard, so I think I can't disassemble them with no screwdriver or other tools (like PF or PU motor cases). May I propose that yours can be disassembled even manually, e.g. lost its "connection strength"?

It might be, but they are brand new...

 

[MinusAndy]

I don’t like the fact that you can’t see the workings when it’s working. The point of technic is to see the workings and if a kid doesn’t know how a diff works, the new ones are basically witchcraft.

[HectorMB]

Well, is true that you see "less movement", but if at least it would have come with increased robustness...

 

Ps: I edited my previous post since I misunderstood the last comment! ;)

Edited October 6, 2021 by HectorMB

[Zerobricks]

They have pros and cons IMO

Pros:

• Can be driven axially or perpendicular
• Can provide a higher gear ratio where space is tight (for example small offroaders)
• The gears don't fall out when removing the axles
• Can be locked
• The strongest differential when driven axially.

Cons:

• Not as strong as normal 28 tooth differential when driven perpendiculary with a 12 tooth bevel gear (might be better when driven by a 20, 28 or 36 tooth beverl gear)
• Because of the design of the 12 tooth gears, the axles are very prone to sliding out and slipping causing the diff to fail

 

[HectorMB]

1 minute ago, Zerobricks said:

They have pros and cons IMO

Pros:

• Can be driven axially or perpendicular
• Can provide a higher gear ratio where space is tight (for example small offroaders)
• The gears don't fall out when removing the axles
• Can be locked
• The strongest differential when driven axially.

Cons:

• Not as strong as normal 28 tooth differential when driven perpendiculary with a 12 tooth bevel gear (might be better when driven by a 20, 28 or 36 tooth beverl gear)
• Because of the design of the 12 tooth gears, the axles are very prone to sliding out and slipping causing the diff to fail

 

Couldn't be a better summary! 

[allanp]

Although not perfect due mostly to the design of the 12t single bevel gears, I have found the new diff to be much stronger than the older 28t gear when driven perpendicularly.

[HectorMB]

This partially solved the issue and the pieces are holding together under high torque. As the gearing inside is made by 1 to 3 to 1 bevel gears, they can take such torque. 

It is a pitty that given the gearing inside, the diff fails at holding together while it can take higher loads.

 

 

Also, removing part of the Y axis insitde of the diff will make place for a better axle insertion, reducing the chances of the axles sliding out. 

Edited October 7, 2021 by HectorMB

[allanp]

@HectorMB Yeah I wonder what the reason is for the Y piece inside the diff. Without it you could mount the bevel gears onto axles with stop. Maybe they did it to stop you inserting the axles too far? But if you was to use axles with stop you could put a 1M beam between the bevel gears to stop them going in any further.

[HectorMB]

7 minutes ago, allanp said:

@HectorMB Yeah I wonder what the reason is for the Y piece inside the diff. Without it you could mount the bevel gears onto axles with stop. Maybe they did it to stop you inserting the axles too far? But if you was to use axles with stop you could put a 1M beam between the bevel gears to stop them going in any further.

That was exactly my thought

[pleegwat]

Diffs are commonly inside a 5x7 frame, and it is not possible to mount the diff if you have already fitted it with axles protruding from it.

[HectorMB]

@pleegwat, as you said, "commonly". Central axle differential, motor coupling, or differential-based gearboxes are few examples on which you may not use a 5x7 frame to house a such piece.

 

For me, the point is what the central Y axis makes for the differential performance. And then, if it's absence makes possible additional uses of the piece. Moreover, bigger room inside of the differential will allow better attaching with regular (non-stopped) axles, reducing the chances of slipping away. 

Edited October 7, 2021 by HectorMB

[Zerobricks]

I agree regarding having no axle center stop. You could put axles deeper, thereby preventing slippage AND use the differential itself as 28 clutch gear for gearboxes and such.

EDIT: You can already the new differential as a gearbox, I will post pictures shortly

Edited October 7, 2021 by Zerobricks