Material for a planet gear carrier in an epicyclic gearbox

[Mike DonnerstagParticipant @mikedonnerstag]

I have a jeweller’s rolling mill with an epicyclic gearbox. However, the cast iron planet gear carrier (link: https://durston.com/product/cast-iron-carrier-for-gearbox-agile-110-drm-100/) is shattered. I was wondering why this would be made from cast iron and whether it would be worth me making one from steel?

The reason I ask is that I recently purchased the machine second-hand and I don’t know whether there are any other parts of the machine that need to be replaced, as these very quickly exceed the cost of a new machine. I’d be very interested in whether anyone thinks it would be worth making the part in steel so that I can at least test that the rest of the machine is good before purchasing expensive parts.

Looking forward to your wisdom,

Mike

[BazyleParticipant @bazyle]

It was only made form CI as that gave the shape easily and cheaply. Sometimes CI is used because it makes a good bearing but not necessary here. Look at the remains you have and see if there are wear marks on the CI surface from the pinions. If so provide washers as appropriate.

[DC31kParticipant @dc31k]

As above, for that shape, cast iron is cheap in production quantities.

Have a good look at where it fits as a simple circular shape is a lot less work to make. Look at its function; do not slavishly copy its form.

If it does need to be that tri-lobed shape, maybe a laser or plasma cut blank would be a good place to start. Make a dimensioned pencil sketch of it and someone would turn it into a dxf file that could be sent to a cutter. All you would have to do is drill and ream for the three pins and bore and keyway the centre.

[Michael GilliganParticipant @michaelgilligan61133]

I can see no need to use cast iron for a replica of that part … anything that locates/maintains the three pins in their required positions is surely fit for the purpose.

MichaelG.

[FulmenParticipant @fulmen]

I agree, mild steel should work fine.

[Ian PParticipant @ianp]

If you have the facilities to make one out of steel, go for it, don’t forget the keyway though.

Steel is a far more suitable material for this part which has to transmit considerable torque. A solid disk rather than any fancy shape would be easier to make. Probably bad design siting the keyway adjacent to a pin (hole) as I suspect that is where the shattering originated.

Ian P

[DiogenesParticipant @diogenes]

..looks a lot like the 3 pin-holes and three longer slots could be on a common radius – visit to the rotary-table and a bit of cutting away & rounding-off.

Can/will you re-use the original pins? ..they might need some consideration if not..

 

[David George 1Participant @davidgeorge1]

I have recently used my rolling mill, ( a cheeper version with a simple gear box) for rolling a piece of gold for a friend, to form a section for a ring and I was suprised by the force needed to roll the gold which needed anealing after each pass as the gold work hardened so easy. I have until this time only used silver which is so much easier to form.

David

[Ian P]

On Ian P Said:

[…] Steel is a far more suitable material for this part which has to transmit considerable torque. A solid disk rather than any fancy shape would be easier to make. Probably bad design siting the keyway adjacent to a pin (hole) as I suspect that is where the shattering originated.

Agreed, Ian

… In fact, although I have no evidence at all for this: I suspect that [historically] the component might have been drop-forged
”continuous product improvement” has a lot to answer-for

MichaelG.

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