reduced project.

[meccanicamg]

the speech of the oil is a little particular because there are always some discrepancies.

basic know that for industrial mechanical gearboxes is used iso vg 220. depending on the temperature of the reducer or rotation systems, however, the same viscosity will be on average even if slightly different.

What do you mean you need some viscosity? How did you calculate it?
bearings must last millions of hours or what is believed by experience or by skf table.
normally a reducer is sized for 5000/10000 hours.

it is absolutely not advisable to use two different oils.

 

[ale_.93]

we have been asked to design everything with the bearings that last 25 000 hours (and other infinite-life components).
However regarding viscosity, there are two charts on the catalog:

graph. 1) enters with medium bearing up to the rotation speed, then read the required kinematic viscosity

graf. 2) enter with the viscosity just found and choose the type of oil (iso 68, iso220, iso 1000) according to the operating temperature prescribed to project.

 

[meccanicamg]

with tool skf you can really see how viscosity really lasts the bearing because you correct with askf

 

[ale_.93]

Yes, that's what I obviously thought.
I had come doubts because somewhere I read that you try to stay with k (required viscosity report on actual) between 1 and 4. so doing comes to eye 5-6 on the primary; about 0.5 on the tertiary.

 

[meccanicamg]

I don't give how much you're turning, but it's not much like viscosity.
keep in mind that normally using vg 220 you have the international viscosity value at 40 and 100 centigrade degrees. about these values you have the operating range.
normally industrial gearboxes reach 75 degrees centigrade and the most lame ones at 95 degrees. if you climb further is because you are doing very special applications and also all seals must be in viton.

bearings at 25000 hours are several unless the application requires it, as much as the organs to infinite life. In reality we never do so and always put a limit on everything, especially if the application is not really continuous full load.

 

[meccanicamg]

to give you an idea look here http://www.acoma-oil.it/schede-tecniche/a262.pdffind some data on the characteristics of oils that are normally used in industry. minerals or synthetics are often used without too many claims. in particular cases polyglycol is used but obviously there should not be bronze gears otherwise you eat them corrosion.

the value of 4 if a teacher must be invented.

nsk for example says more than 13 mm2/s for radial ball bearings or cylindrical rollers.
more than 20 conical or adjustable rollers and more than 32 roller-adjustable axles

 

[ale_.93]

Okay, thank you.
the speech is: the primary requires a certain viscosity (relatively low). Putting a single oil, he gets a viscosity higher than the minimum required, so he automatically finds himself working "overhauled".
then you go back, you choose a bearing that lasts less hours, but that however arrives at 25000 thanks to the askf value that rises considerably.
Right?

 

[meccanicamg]

Of course it is. therefore it is necessary to understand when designing real gearboxes if you want to compare to the old way or to the new one with askf that makes it last a lot in more undersized bearings of the old way

 

[ale_.93]

perfect. thank you so much for clarity and patience especially!

 

[ale_.93]

I wanted to ask one more question: When I mount x-ray conical roller bearings, I thought I would mount them the same on both sides, trying to balance the two radial forces so as to balance their duration.
However, the catalogue shows this table where it asks to do that verification on the ka, which obviously does not return if it balances the two radial loads on the bearings.
If I have to respect that last line I should mount two pretty different bearings (so that they last about the same number of hours), which I don't like very much

 

[ale_.93]

I mean, more than anything else, I don't understand the difference between 2a, 2b, 2c.

 

[meccanicamg]

If that's true, what you're saying would not exist the various couplings of "or" bearings or "x" or "tandem".
see here http://www.skf.com/it/products/bear...ller-bearings/designs-and-variants/index.html in the bearing section attached.
also the forces to check are here http://www.skf.com/it/products/bear...-row-tapered-roller-bearings/loads/index.html.


the three cases described are based on the value fr/y and depending on what is worth different calculations.
read the formulas well and try to reason again.

 

[ale_.93]

Yeah, I got it. while in the sizing of the tab, is the maximum permissible pressure considered to be 200 mpa? I can't find an exact value.
use the 17 crnimo6

 

[meccanicamg]

for the tab the material is c45 reclaimed and I would say it could go well 200 mpa at specific pressure even if I would do rp0,2/1.5