Hirth Coupling

[DVE]

Hello,

I am looking for any information about Design & Calculation of Hirth coupling.
(Is there some standard existing ? How are defined the teeth ? Maximum allowed torque ? Serration by bolt ?)
...
Last but not least : how are reacting Hirth coupling when the shaft is under flexion load ?

Thank you,

DVE

 

[unclesyd]

Here is one site for the Hirth coupling. We looked at the Hirth but opted for the Curvic instead due to power requirements and the design engineers familiarity with it.

http://www.transconn.com/components/hirth/index.htm

 

[smckennz]

Also try

http://www.electricity-today.com/et/Oct96/turb.htm

There is some design info near the end of the article

Cheers

Steve

 

[arnoldh]

Hi DVE,

i have made some calculations for a design study a little time ago. the spreadsheet I used must still be somewhere around. I cn have a look if I still have it and send you a copy of it (if you want)
Regards,

Arnold

 

[CouplingKing]

Hirth Gears can be bought from Matrix. Their catalogue has some good info in, but I've mislaid my copy.

Their website is

http://www.matrix-international.com

Look at the motion control bit.

CK

 

[arnoldh]

DVE,

sorry, totally forgot this thread. you should now have the file. Hopefully you will find somebody who knows some germen (although the formulas are shown as well as some sketches). Good luck (and hopefully the file isn't too late )

 

[Nickand]

You should visit this page:

http://www.tedisa-hirth.com

The webpage is a bit old but they will probably help you. I know some people who use their hirth couplings and they just told me that the accuracy and the quality was fantastic. Before he used curvic coupling but he has definetely changed to hirth coupling.

 

[Nickand]

I also think that in

http://www.tedisa-hirth.com

have some formulas to calculate and design the hirth teeth. They also have some standard coulpings, so I believe they have already been calulated to support a high torque force.

 

[DVE]

Hello Nickand,
Thank for your support (I knew already Tedisa).
Just before your post, you will see that Arnoldh has sent me a claculation sheet (in german).

 

[aamoroso]

I have personally machined several of the Hirth Couplings in the past on this page:


AMC Precision

Extreme tolerances, expensive and time consuming to make, and just as difficult to measure. We had all kinds of special procedures that most shops can't touch. I can't tell you how we held the tolerances but it was a quite a process. Off the top of my head hear are the parameters we typically held:
24 teeth Equally spaced no accumaltive tolerance allowed
Shaft face was like 83.5 concave
Teeth were 83.5 convex
Total runout was less then .0005 on face and .0002 on tooth cutting.
Diameters were about +/-.0002
Depth location was +/-.0002
Teeth profiles were 60degrees, about .1 deep, flats between teeth were about 1/32.

Fill what's empty. Empty what's full. And scratch where it itches.

 

[DynoGuy78]

Another site is Voith Turbo where they list their standard rings.

http://www.voithturbo.com

Choose "Products & Applications" - "Industry" - "Hirth Serrations" then look around.
There are also PDF documents by selecting "Current" - "Orders/Downloads" - "Publications" then sort by "Universal joint shafts & connecting...". There are two docs, a general info one (G1704) and a more technical one with some design equations (G699).

I am currently considering a Hirth or a Curvic profile but have been unable to decide which is best based on performance and economics. Any opinions?

 

[Nickand]

Hi Dynoguy68,

What is the application you would use the coupling? Anyhow, I think that hirth couplings is more accurate and much cheaper, as teeth in both pieces are the same and in curvic the profile of the grinding wheel is different in each of the pieces, fact that increases the cost of manufacturing.

I already knew the webpage of Voith. It is quiet good. However, I know a some machine tool manufacturers that used to buy Voith and they have definetely changed to Tedisa; better quality and price.

Well, I know users of these kind of couplings but all of them are machine tool builders. Do any of you know more applications for hirth couplings?

regards,

 

[aamoroso]

The applications we used to manufacture hirth couplings for was mainly Turbine machines that spun at about 64,000 rpm (balance was a priority, hence the tight tolerances).

Fill what's empty. Empty what's full. And scratch where it itches.

 

[Nickand]

And now you do not manufacture hirth couplings for turbines or you just changed your job?

Yes, I really had already heard that Siemens, for example, uses hirth couplings in it turbines, but never sawed anywhere else than in tool machines.

i think that aeronautics also uses hirth (or maybe curvic, instead of hirth) couplings, isn't it? In this application, do you know why it is used curvic coupling instead of hirth coupling?

Regards,

 

[unclesyd]

In my original post I mentioned we. We was our materials and engineering group and Pratt and Whitney engineers that did the design work the compressor in our HNO3 plant. There are series of Curvic couplings that connect the Steam Turbine to Air Compressor and to the HP expander (all combined call the plug). The total HP transferred by the couplings is 24,000 at 12,500 RPM.
Privy to only bits and pieces of the design details it was never any consideration of using anything other than a Curvic even though the Hirth Coupling was brought up several times.
The driving force in selecting the Curvic was our Rotating Equipment Guru, an ex U-Boat Captain and Turbine Engineer and the P&W people. I know that during the discussions at the time was concern over surge and the failure, unloading, of the HP Expander. There was also considerable discussion of driving the plug through though critical speed. This discussion was centered around anticipitaed axial movement in meeting I attended, unfortunately I had to leave before the movement problems were discussed.

In about thirty years of operation inspection has reveled two of Curvic couplings to be crack, through the hub crack.
We have never seen any wear on the couplings, it other word they have stayed coupled.

 

[aamoroso]

And now you do not manufacture hirth couplings for turbines or you just changed your job?

I changed jobs and careers, I have sinced moved into engineering and management from machining.

My experience with the Hirth Coupling was limited to the defined parameters of the customer, with limited knowledge to the direct applicaion. I can offer little in terms of performance and practacality other than to say it was working for sevearl of our customers. Without naming names there were a few prominant mfgs using the couplings we machined. Very tedious work, especially considering many of the parts that came to us had tens of thousands of dollars in work already performed to them, so handling alone was a specific procedure. Balanced high RPM products a just so much fun (sarcasm).

Fill what's empty. Empty what's full. And scratch where it itches.