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  • How to match grease(base oil viscosity,thicken)er) for manual gears?

    Discussion in 'The main mechanical design forum' started by xchcui, Mar 9, 2015.

    1. xchcui

      xchcui Member

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      Hi.

      I recently repaired my manual window regulator in my car(the one that lift the window)(attached photo)while i apply to the gears new grease.
      The window regulator operate manually(no motor)and has metal drive gear and plastic driven gear(attached photos).
      Since there was a plastic driven gear i used a synthetic grease(silicone based oil(150 Cst)+lithium complex thickener(NLGI-2).
      My question is not about the type of the grease that i should apply to the gears(mineral,PAO,silicon etc)
      My question is how should i match the viscosity of the base oil of the grease and the thickener to the application?
      In my case,since the gears operate manual,what should be the viscosity of the base oil and the thickener and if the plastic driven gear was,also,made of metal,was it matter?(i refer to the viscosity and the thickener,not the type of the oil/thickener)

      Thanks in advance.[​IMG][​IMG][​IMG][​IMG]
       
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    3. Robo-dog

      Robo-dog Member

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      Please refer to your car manual to determine on manufacturing recommendation.
       
    4. xchcui

      xchcui Member

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      Hi Robo-dog.
      Thanks for your reply,but this is So unprofessional answer,no offense.
      I opened this thread in order to understand what is the rules that determine what should be the viscosity of the based oil of the grease?what is the factors that i need to take into a count when i choose the viscosity of the based oil to apply on gears and you direct me to the manual?:)you could,also,send me to the mechanic,couldn't you?:)
      My purpose of my question is to understand in general:what is the rule of thumb when i want to match a grease to gears?and i refer only to the viscosity of the based oil of the grease and the NLGI of the thickener.
      I took for example my window regulator,IT IS ONLY EXAMPLE,something to begin with,because the question arise while i changed the grease of it and i would like to start the explanation with it.I used the grease with the spec. that i mention before(since that what i had,while i don't really sure if it is the best match).I mentioned the viscosity of the based oil of the grease in order that the answer to the question will start with that.
      I mean someone will response if the viscosity of the based oil that i applied is good or bad to that specific application and why?
      what is the right viscosity of the based oil(and the thickener)that i should apply to that gears and i what is the factors that made him to determine that.and finally,what is the rule of thumb of determine what viscosity of based oil and thickener to match the gears?

      Thanks in advance.
       
    5. Robo-dog

      Robo-dog Member

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      It's pretty obvious. Do you want your grease to drip or not to drip? The viscosity really has nothing to do with gears in application to grease. It's just to prevent it from getting rusted because there can be moisture trapped in there and can ruin the metals!

      When you have a ball bearing, THEN you would want to consider the thickness of the grease because of the torque value you are trying to accomplish.

      I direct you to the manual becuase they are going to tell you what type of grease you should use, regardless of it's viscosity. Beside, it changes when temperature is applied, so...what's the point? If it gets really hot, it will soften it up, and can drip, then you just lost it's grease application.

      So you ask what type of grease should you apply....I say GO to the manual, to get the manufacture's recommendation. Problem solved!
       
    6. xchcui

      xchcui Member

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      From your answer,i assume that you don't have the knowledge to answer my question and that is,probably,the reason why you are missing my main point.But this is ok.I always appreciate any help,so thank you again for trying.:)
      I believe that the thickener is more responsible to the dripping issue while the viscosity of the based oil is determined regard to the speed of the gear and the pressure on them.
      I hope that one of the professional members in this forum could help me with my question.
      Again, the window regulator gear was just an EXAMPLE to begin with an answer and my purpose is to understand how to match a based oil viscosity to the gear and not just to know what to apply.
      That window regulator gear operate manually by hand so it is probably consider low speed(maybe it considered higher speed,i don't really know)it,also,operate with the power of the hand,so i assume it considers light or medium load.based on that,what should be the viscosity of the based oil?68Cst?100Cst?150Cst1000Cst...and follow by that example,what is ,in general,the rule of thumb to determine the viscosity of the based oil grease to gears?

      I will very appreciate for an answer from professional member.
       
      Last edited: Mar 10, 2015
    7. Robo-dog

      Robo-dog Member

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      I've seen other threads that you've posted, and nobody knows what you're talking about. But I can tell you this, the higher the gear speed is, the lower viscosity you'll need. ONCE AGAIN, REFER TO YOUR CAR MANUAL FOR THIS SELECTION.

      I'm an Engineer. I've designed the 787 Section 41 Dreamliner, I've done static and dynamic testing for Adam Aircraft, I have knowledge in this. The Engineer will determine the best grease used, then will tell the technical writer who prepares the manual, will put that information in there.

      Your application is low function, and you have other factors at play there that nobody can really answer your question unless they know what factors are at play. You have Transmitted Power play, You have Surface Finish play, you have Loading Play....and so on. Then you have the material type at play as well. So I'm telling you to go refer to your car manual which will recommend the type of grease needed for that application.

      You're not accepting my answer because you're not listening. The Engineer who designed a product will tell you the best recommendation, because they know all the factors that will determine the best results.
       
    8. Robo-dog

      Robo-dog Member

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    9. xchcui

      xchcui Member

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      Thanks Robo-dog,but you didn't help me with nothing.
      I had already read that link once before,but it is refer to oils and no to grease.
      please,lets give to someone else to try and help with my question,one of the expert of this forum.
      Although,i am the one who asking the question,there will be a lot of surfing that maybe see this thread and will prefer a better answer than "go to your car manual".(as if you telling something new).Why do you think that i asked this question in that forum?Do you think that i didn't try to find the answer at the car manual?if you read carfully my question you will notice that my question is more than an answer that i can find in the manual.
      Please,don't response to that,they are rhetorical questions.
      I try to ask my question step by step.

      I attached 4 photos of the window regulator gear in my first post.At the photos you can see at close-up the drive gear and the driven gear.
      I mentioned that this is manually gear,which lift the car window with the power of the hand(no electric motor).
      All the manual window regulator gears in the cars are more or less the same idea and they use,i assume,a grease with the same based oil viscosity(more or less).
      What is the based oil viscosity of the grease that uses for this application?and why?
      a)68Cst?
      b)100Cst?
      C)900Cst?
      d)other value?
      e)all the answers are right.

      If there is an expert in this forum at this subject,he should know the answer,refer to the photos and the information that i gave.

      Thanks in advance.
       
      Last edited: Mar 11, 2015
    10. xchcui

      xchcui Member

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      Nobody in that forum know the answer?:eek:
      This is very very simple question for an expert,even for advanced amateurs.
      Where are all the experts of that forum?:confused:
       
    11. xchcui

      xchcui Member

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      More that 2000 views and no one know the answer?
      I am very disappointed from this forum.
      If nobody at this forum know what should be(more or less)the viscosity(In Cst) of the grease's based oil for such simple general gear,while it is a well known gear for mechanical experts,so i don't think that it is really"The No. 1 online community...".
      VERY DISAPPOINTED:(
       

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