Type A keyway sizing

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1

Hello everyone,

 

Despite my training in mechanical engineering, I am stuck on the sizing of a key.

After several searches on the internet, I find several different methods for calculating the matting stress. Here are my questions for the calculation of this constraint:

- Should we take the total length of the key or should we take the length L - a (see figure 1)?

- For the calculation of the mated area, what height of the key should be used? Total height, height H1 or height H2 (see Figure 2)

 

Thank you in advance for your help


dim1-clavette-copie1-300x256.jpg
2

It all depends on the shape of the key....

 

For a key of form A: Active L = Total L – a

For a key of form B: Active L = Total L

For a key of form C: Active L = Total L – (a/2)

 

For the matted surface: Sm = (b x L) / 2 with b = height of the key in mm and L = length of the key in mm.

 

+ info here:

http://edesignlab.fr/calcul-de-clavette/

3

Thank you for this quick response.

 

However, in my case, the key is 5mm in total height. The depth of the groove in the shaft is only 1mm while the key is 4mm in the hub.

So I'm not sure of the "/2" of the formula Sm = (b x L) / 2, because in my case the key doesn't sink half its height into the groove of the abre. 

 

I hope my explanation is clear.

In other words, I don't know if this formula applies regardless of the depth of the keyway?

 

Thank you

4

What is the diameter of the tree?

5

Diameter 12

 

I attach the engine spec


7833141.pdf
6

It's not a standard rig (1mm is super low).

However, I confirm that to calculate the matting, it is the total height of the key that must be taken into account, the contact surface of the shaft, as well as the bore.

 

To save time, you can use this site for calculations

http://jean.lamaison.perso.neuf.fr/clavette.php

1 Like
7

Good evening

I use these calculations here -->http://edesignlab.fr/calcul-de-clavette/ ;)

8

 

Hello

 

I contacted the supplier of the NORELEM key who also confirmed that this calculation is the right one.

--> http://edesignlab.fr/calcul-de-clavette/

 

Which confirms to me that the key seems undersized:

 

The calculation gives the following results starting from the nominal torque:

- Shear stress: 95 MPa

(Rpg = 61.25 Mpa taking Rg = 0.5 Re, Re = 490MPa)

 

- Matting stress: 190 MPa

Which is above the permissible pressure for a fixed keying (which is my case)

And these results are only obtained from the nominal torque!

So I contacted Valeo's technical support who told me that this engine is designed in Hungary and that they can't help me....

I will try to contact their design office in Blois.

 

Thank you for your help.

 

9

http://webintra.lyc-catalins.ac-grenoble.fr/public/LP/Construction_DI/Ressources/clavetage_clavette.htm

10

Thank you for your answers.

We are going to modify our system with a different engine because it may be too complicated to ask Valeo to upgrade their engine.

 

11

Hello

 

Sorry for the late answer but I came across this topic and the answers given seem ambiguous to me

 

The matting calculation is the calculation of a permissible pressure on the matted surface. So the smaller the surface, the more matting will be important. Therefore, in the event that the key is not placed symmetrically between the shaft and the hub, the smallest key height will have to be used.

 

In the case of mmarion you will have to calculate the matting with h2.

However, if you use the formula on this site: http://edesignlab.fr/calcul-de-clavette/ the mate section is no longer Sm = (b x L) / 2 but Sm = (hxL) because b/2 represents the half height of the key.

 

Here is a link for an application made in excel: http://appliexcel.wix.com/appli-excel

 

Kind regards