Balancing rear carrier in automatic transmission

[woodaaay]

Hi guys,

I'm having some trouble getting my head around how to balance the rear carrier in an AT.

I have this standard:
ISO 1940 - Mechanical vibration -- Balance quality requirements for rotors in a constant (rigid) state -- Part 1: Specification and verification of balance tolerances

Is it possible for me to assume that, for balancing purposes, the carrier is in a rigid state? It isn't supported in the same way as what the standard refers to i.e. Internal or External rotor supported by 2 bearings, as at any time it is in contact with sun gears, owc, and carrier shaft. However a preliminary and basic analysis is required.

Any help would be greatly appreciated.

 

[GregLocock]

Not knowing what a rear carrier is but it sounds like part of the diff, presumably the crown wheel assembly.

If so, yes it is rigidly mounted in their terms.




Cheers

Greg Locock


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[woodaaay]

Hi Greg,

Thanks for the response. The rear carrier I am refering to is the planetary gear carrier inside the transmission.

Cheers,

Brian.

 

[GregLocock]

Oh OK. having had a bit of a think I wouldn't really worry about terminology since the balancing process is the same. Or are you trying to set a limit for the out of balance?

Cheers

Greg Locock


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[Tmoose]

An important part of balancing is spinning the part around the same axis as when in operation.
Also having a correction method that does not weaken or otherwise compromise the part function

Selecting a tolerance in 1940 requires knowing the service speed, the part weight, and appropriate "grade" (probably 6.3).

A "machined all over" symmetrical part with concentric ID and OD (less than ISO eccentricity or gm-inch/gram value) can have pretty good balance.

 

[woodaaay]

Timoose,

I have used 6.3 for my preliminary calculations though the part is actually a welded assembly and has 6 gears within so is a far cry from a "machined all over part".

The thing I was not sure about is that it is supported by a drive shaft at one end which isnt "rigid" (it is supported elsewhere through bushes etc) and a 1-way clutch at the other (also supported by a bush), so there will always be a slight angular and radial misalignment. Whether that is an issue at service speed Im not sure.

As it is supported in two places by splines I am unsure where I should take the "bearing planes" to be. For the moment I have used the centre of each supporting spline.

Using this idealised approach of a rigid rotor the permissible unbalance at the chosen planes is acceptable as per 1940 for an "Internal" rotor.

 

[mfgenggear]

would it be possible to weight or dynamic balance the details prior to assembly?

welded then machined, may be possible to balance depending on the criteria.

just some suggestions

Mfgenggear

 

[GregLocock]

To meet automotive standards of balance you mostly have to do a post assembly balance op. The exception I can think of is the halfshafts. I must admit I can't remember if the crown wheel is balanced.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[mfgenggear]

My shop dynamic balance details prior to assembly per customer requirements.
I imagine the balance is re-checked at assy.
thats why I made the sugestion. I curious how something like a carrier assembly would be balanced.

would it similar to a cranshaft balancing method.
except bob weights are employed for crank shafts to offset the out of balance.

in carrier how is the imbalanced measured?

Mfgenggear

 

[woodaaay]

mfgenggear,

I've been told that the imbalance will be measured using an in-house balancing machine though I'm unaware of how they are going to set it up correctly.

It has been assumed that a single correction plane will be used as there is only one area by which to add or remove material within the carrier but I'm seriously doubting the assumption that balancing an assembly such as this can be achieved in a single plane.

I have been unable to find any relevant literature on balancing components within an automatic transmission (I suppose they all have their secrets and thousands of $$$ invested into their own process and standards) but any help in this regard would be greatly appreciated.