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Home > Forums > Mechanical Engineers > Activities > Gear & Pulley engineering Forum

Crowned Spline Shaft

Read More Threads Like This One

bdk9999 (Mechanical)

1 Jun 12 17:23

I am designing a crowned spline to handle 5deg misalignment and I'm wondering if a standard hob can be used to make it or will a special hob be required? If the hob follows the face crown radius will the profile crown radius come out right?

I've attached my current spline specs that I'm considering.

Thanks
Brent

gearcutter (Industrial)

2 Jun 12 0:31

5deg is quite high as is your result for Sc.
Generally gear type couplings run at around 1-2deg.
How long do you need the coupling to last for?
I'd be re-doing the numbers and getting Sc to at least half of what you've come up with.
Standard hobs can be used but remember that a well designed gear coupling will either be tip relieved or tip chamfered. Both modifications can part of a hob design or they can be produced on a gear grinder.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181

bdk9999 (Mechanical)

4 Jun 12 10:40

I'm hoping for 1000 hr life. I've done my calculations using the Machinery Handbook recommendations for crowned splines and compressive stress limits of 20ksi for case-hardened crowned spline.

I will see if I can tweak the numbers a bit to reduce the stress. I need every bit of 5deg of misalignment if possible. A CV or other type of flexible coupling is likely not going to work for my application.

I will be able to flood the spline with oil.

Thanks,
Brent

gearcutter (Industrial)

4 Jun 12 21:12

I made a mistake with the conversion to MPa.
I should have worked out that 1 lb/in^2 = 0.00689 MPa - Sc of 19,000PSI = 131MPa
Your value for Sc is quite low so you shouldn't have a problem here.
Let us know how you go with running the coupling at 5deg.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181

EdDanzer (Mechanical)

20 Jul 12 0:14

You could look at what is done in geroter type low speed high torque hydraulic motors.

Ed Danzer
www.danzcoinc.com
www.dehyds.com

tbuelna (Aerospace)

20 Jul 12 21:28

bdk9999,

Those recommendations in Machinery's are very conservative. With case hardened teeth and a simple surface contact stress of 19ksi, your spline should have virtually unlimited life. Of course, this would also assume that the spline is lubricated properly, preferably with a recirculating oil system.

As gearcutter noted, I would also recommend that you check for tooth thinning. With a 16dp tooth, .8" face and .035" crown drop, you may end up removing some tooth tip at the ends.

Good luck.
Terry

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