Involute Spline Crowning 1

[Tamgear]

I am modifying profile of 2.5/5 ANSI 92.1 Std spline to take 1 degree misalignment. There is bending and torsional load on this spline coupler. I would like to Crown the spline flanks and OD to avoid end loading during misalignment.

Shall I use std Hob cutter for hobbing this spline or should i need to use protuberance hob for having releif between TIF and root radius. Please direct me for the resources on this issue. If the protruberance hob is required, will it be special tool or readily available for ANSI splines .I prefer Shaving operation for crowning.

-Tam

 

[Tamgear]

Some more details on this spline, 2.5/5 Pitch, 12 Teeth external, 30 Degree Pressure angle, Flat root side fit, 35mm Face width, 1 degree misalignment. 350 HP @1000 Rpm.

 

[gearcutter]

You won't need to use a protuberance hob to generate a crowned spline profile.
Clearance is created by the change in the depth of cut over the length of the crown.
Other than a change in tooth thickness, the correct profile is generated.
Make sure you allow for the crowning in your load calculations.
IMHO, shaving would be an unnecessary added cost.
If shaving; then you'll need to use a pre-shave hob which will add even more cost as it will require the manufacture of a special hob.
My 'gut feeling' tells me that a 35mm face width, for the power you intend to transmit, seems too small.


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[Tamgear]

I will go with regular spline Hob cutter. Thanks for the input.

For load calculations with Crowning, I will be using the equations from Machinery's handbook, which checks compressive stress on the sides. If you have any other source of equations, please let me know.

Should i need to have full crown till the cenre of the face width on the spline flank(Complete radius) or shall i have some flat profile for some length like in some gears. Will it make kind of line contact if i have full profile only at the centre, since the mating Internal coupler has regular straight std teeth?.

 

[tbuelna]

Tamgear,

With your 35mm face width and 1deg angular misalignment, you'll need a fair amount of crown drop (>.25mm?). So a full crown (no flat) would be best.

I would also agree with gearcutter's last comment. I did a quick check of your flank contact stress with a full crown and it looks to be in excess of 20ksi. This contact stress level would usually call for case hardening of the teeth to get a long, fret-free spline life.

Hope that helps.
Terry

 

[dinjin]

You could also put a low angle chamfer on each side of the od unless crowning on the full od is not that much of a problem.

 

[Tamgear]

Thanks for your inputs.

I have modified the numbers as follows.

Dia. Pitch P 2.5
Number of Teeth N 12
Pitch Dia D 4.8 in
Face Width F 1.65 in (42mm)
Crown Height A 0.0072 in(Misalignment 0.5degrees)

I am getting 15.5 ksi compressive stress. Little fretting possible.

Material: Will use 8620 Case Hardened steel 58-63 HRc.

I am using matting internal splined coupler with 46mm face width (2mm per side longer than matting coupler). On OD, will have chamfer as dinjin said.

These couplings will be running dry (expected hours 3500). Since there is no lubrication, I wonder whether wearing material will oxidise and accelerate the wear process.

Please pass on your comments. I have attached the compressive stess cal. sheet.

-Tamgear

 

[Tamgear]

Mating part Material : 1045 Steel, Induction hardened to 50 HRc
-Tamgear

 

[gearcutter]

You are going to end up with quite a bit of distortion due to the heat treatment processes you have chosen.
Tooth to tooth indexing errors would be my greatest cause for concern.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[Tamgear]

gearcutter,

Thanks for your reply. Even I was wondering about the same.

Please let me know, If you have any other material and HT process in mind.

Shall I use the Class 5 tolerances for the ANSI spline for crowned external spline and straight matting spline ( Both flat root side fit).

-Tamgear

 

[gearcutter]

I think it might be wise if you consider engaging a gear consultant to verify your design.
It sounds like it's an important application so having the design verified is well worth it particular if there is no R&D allowed for in the project.
I've lost count of the failed initial designs I've come across.
Although as a manufacturer, failed attempts can be a good source of income


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181