# NEMA 17 axial shaft load ?



## goffinette (Oct 8, 2020)

I am not an expert in robotic.
I am currently working a new prototype display window. The concept is to give a 360° vue of the displayed object. We plan on hanging the object to 2 threads that would be somehow attached to the motor in the upper part of the display.

What is the maximal load that I can hang from my motor shaft ( in the axial direction) without slowly damaging my motor? (I didn't find this info in the datasheets my motor is an OMC 17HS19-2004S1 )

Also what is good and reliable way to axially hang something to my motor shaft. I m afraid of coupleur joint as the object i going to hang is quite delicate and would break if the joint coupler small screws went to unscrewtheself. Are joint coupler reliable? 
thx


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## macardoso (Oct 8, 2020)

Motor datasheets often list this information. It will not be much load. If possible, I would create a simple bearing support with two tiny angular contact bearings back to back. This would support the thrust load of your display. The motor can then be connected to this shaft with a flexible coupling.

Similar to this graphic except with lighter duty components, and instead of a ballscrew, a small shaft to hold your display. If the load is vertical then no bottom support is needed




In this configuration, the black nut (just to the right of the orange and silver motor coupling) bears all the weight of the load. The motor is kept totally isolated. You can buy premade bearing blocks (the square black thing) or you can make your own.


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## macardoso (Oct 8, 2020)

Here in an Axial/Radial load bearing life curve for a Nema 17 motor sold by Applied Motion Products (They make nice stuff). I'd expect yours to be similar.






			https://www.applied-motion.com/sites/default/files/Stepper%20Motor%20Life%20data-110817.pdf
		


Notice your axial load limit depends on how much radial force is being used and how fast the motor is going. At 0 lbs radial force (pure hanging load) you can hang about 35 lbs from the motor shaft and expect 20,000 hours (This typically represents 10+ years of field use (8 hours / day, 5 days / week, and 50 weeks / year)) of operation at 450 rpm. This is a statistics thing, so L10 life means that 90% of motors which have been properly handled and installed will yield this life span. 10% will be outliers and fail early.






						What is L10 Life? | Rexnord
					

L10 life is a calculation to determine, with 90% reliability, how many hours a bearing will last under a given load and speed. Learn more about how to solve an L10 life equation here.




					www.rexnord.com


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## macardoso (Oct 8, 2020)

If you do intend to only use the motor, a split hub coupling will far outperform a setscrew coupling. If you're hanging the load directly from the coupling, then a flexible one is not needed.


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## macardoso (Oct 8, 2020)

Also, welcome to HM. Don't be afraid to ask any question - everyone is friendly here.


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## goffinette (Oct 8, 2020)

macardoso said:


> Motor datasheets often list this information. It will not be much load. If possible, I would create a simple bearing support with two tiny angular contact bearings back to back. This would support the thrust load of your display. The motor can then be connected to this shaft with a flexible coupling.
> 
> Similar to this graphic except with lighter duty components, and instead of a ballscrew, a small shaft to hold your display. If the load is vertical then no bottom support is needed
> 
> ...





macardoso said:


> Motor datasheets often list this information. It will not be much load. If possible, I would create a simple bearing support with two tiny angular contact bearings back to back. This would support the thrust load of your display. The motor can then be connected to this shaft with a flexible coupling.
> 
> Similar to this graphic except with lighter duty components, and instead of a ballscrew, a small shaft to hold your display. If the load is vertical then no bottom support is needed
> 
> ...


Nice proposal, thx for the solution! It looks like it can release the load from the motor efficiently.
With this solution all the weight will be holded by the small screw of the black nut (in which I insert another shaft I guess) is this reliable enough to hang 500g or is there a risk that is slips and fall on the ground overtime?
My displayed object is kind of expensive and fragile


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## macardoso (Oct 8, 2020)

goffinette said:


> Nice proposal, thx for the solution! It looks like it can release the load from the motor efficiently.
> With this solution all the weight will be holded by the small screw of the black nut (in which I insert another shaft I guess) is this reliable enough to hang 500g or is there a risk that is slips and fall on the ground overtime?
> My displayed object is kind of expensive and fragile



The shaft used in the bearing block will need to be machined. Typically this will have one end with a reduced diameter to fit the bearing inner diameter and then a thread just slightly smaller than that. The nut goes on the thread of this shaft and squeezes the bearings between the face of the nut and the shoulder between the small and large diameters of the shaft. In a vertical configuration, the nut will carry the entirely of the load axially along the shaft. As long as the nut does not come off, the load cannot come out of the bearings. A prevailing torque locknut would be a good option here, like a nylon insert locknut.









						McMaster-Carr
					

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




					www.mcmaster.com
				




The bearing block can be custom designed and machined, or they can be purchased prebuilt. I'd look for a cheap, small sized ballscrew end support personally. It will come with bearings and be an attractive block color.

Here is a cheap set from eBay. You'd only need the one end. 









						BF10 BK10 End Support Bearing Blocks for 1204 Ball Screw  | eBay
					

Locking nut and snap ring are included.



					www.ebay.com


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