Doubts about the operation of a clutch 2

[Galvano]

Good afternoon,
Sorry for my bad English.

At my work, there is a machine that has two reels of tape. The machine has two axes that collect the tape and wind it on one reel or another.

The coils move in one direction or another by means of a transmission with clutches. These clutches are cork.

The question I have is whether these cork clutches have the same torque in one direction as in another. They are made up of two cork discs, the transmission pinion and a spring that compresses it. The question is... Is the torque the same in one direction as in another?

Thanks

 

[3DDave]

Who designed this?

 

[Galvano]

3DDave, I don't know. The machine is like this. For the mechanism to be better, the cork should make contact with metal. Not with nylon. I have seen that there are sewing machines with cork clutches but they clutch on steel.

 

[desertfox]

Well you can try stronger springs and putting the cork against steel however without any other information it’s all trial and error, do you know the size and mass of the tapes and or the motor driving torque for the axles?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Galvano]

Yes,I can know the maximum size of the tapes and aproximately the mass. More or less the maximum diámeter of tape cylinder can be 55 mm and lenght 80 mm and weight 0,3 kg

 

[desertfox]

Hi Galvano

I assume the clutch slips when it is winding on the tape?
Let’s see if I understand correctly your last post :- the tape once wound onto one of the axles is 55mm diameter? What is the diameter of the axle prior to winding? Do you know the rpm of the axles when rotating and the torque of the motor driving the axle. I assume the axle winding on the tape is driven by a motor and the other just idles.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[3DDave]

If you don't want it to slip cut out the middle of that cork so there is only a rim contacting the gear - this will increase the leverage but it still needs a substantial metal plate to work that way.

http://www.thecartech.com/subjects/design/Automobile_clutchs.htm

noting that the clutch surface is a ring, just like it is with every other disk clutch that's ever useful. It even covers cork.

To find the friction of cork on nylon, set the nylon gear horizontal and the cork face down on top then slowly tilt the gear until the cork slips. Note the angle at which the cork slips - the tangent of that angle is the coefficient of friction.

 

[Galvano]

Dave
Yes, instead of the full disk it could be a cork ring. However, as you can see, the spring is in the central part and I don't know how it behaves.
In the old car clutches, there were springs in the middle diameter of the clutch disc and later a diaphragm.

 

[Galvano]

Hello desertfox,

Yes, the clutch does have some slip when it winds up but the spin is continuous. The problem is that sometimes it slips too much and does not roll.

The other reel motor is idle and its clutch is slipping to allow tape release.

The maximum diameter of the tape will be 55 mm and the axis without tape 20 mm

The geared motors do not know the torque now, but they have a lot of power (they cannot be stopped by hand)

In any case, I think that with some new corks it would have to work as if it were new, but it is a bad system.

As we said, increasing the outer diameter of the spring and calculating its dimensions for the same force, we would have more torque and it would be ideal, right?

 

[desertfox]

Hi Galvano

Yes if you can redesign the spring with a larger OD with the same force then yes the slipping torque would increase however what force are you going to aim for? Also the new spring might not fit in the same space envelope without the spring being over stressed which then means you have gained nothing.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Galvano]

I don't understand this.

Also the new spring might not fit in the same space envelope without the spring being over stressed which then means you have gained nothing.


The torque obtained would be greater for both axes, so later they would have to be adjusted to work in both directions.

I think this would be more effective than a spring with more strength and the same diameter, because the spring support is a larger diameter.

Anyway I think the cork must be in good condition in the first place.

 

[desertfox]

Hi Galvano

When a compression spring is designed the size the forces and the number of coils are optimised so that when the spring is operated it doesn’t get over stressed and plastically deform, if as I have seen happen many times when a spring is altered or redesigned the stress in the spring is often over looked and when the new or modified spring is fitted it doesn’t work correctly because it is compressed and plastically deforms, which then means it doesn’t give the required force it was meant to at its preloaded length.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Galvano]

I think the best thing to do would be to try new corks and if things continue to go wrong, I'll try another spring.

I tried to place two metal discs glued on the pinion but not much improvement was appreciated. Anyway I'll look at the torque of the mororreductores and the rpm and tell you.

 

[desertfox]

Hi Galvano

Okay thanks for the update .

Something else you should be aware of :- at start up of the motors the friction coefficient is the static coefficient that we have been talking about however if these clutches are slipping while operating then the coefficients of friction become dynamic coefficients of friction which is usually a lower figure than the static friction.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Galvano]

That's it. At one point he slips too much. It can start fine and then slip too much or spin on start.

In fact, they should slip when it works, but in such a way that there is a continuous transmission.

For this application I think the easiest thing would be a stronger spring or one with a larger diameter and the same force. But I don't know how much more torque it would take. Too much torque would wear out the corks soon.

 

[Galvano]

Thanks for everything. In the end, the fault of everything was basically that we did not have adequate information from the manufacturer to regulate these clutches.

Once achieved (Regular nuts properly) Everything worked. However, corks in poor condition that are not rough will be replaced by manufactured cork sheets.

Greetings.