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Technical pinion angle ?

Discussion in 'Traditional Hot Rods' started by johnrfray, Aug 10, 2019.

  1. X-cpe
    Joined: Mar 9, 2018
    Posts: 786

    X-cpe

    There are probably enough SAE papers written on the subject that, after you got the right engineering degree, you could spend the rest of your life on the shitter.
     
    Last edited: Aug 13, 2019
  2. Andy
    Joined: Nov 17, 2002
    Posts: 4,504

    Andy
    Member

    I thought someone would be interested in how the car companies did it. It is really interesting how the working angles of the front joints equal the rear working angle.
    I was also showing that parallel is not the only solution, just the simplest but no always the best.
     
  3. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 668

    ekimneirbo
    Member
    from Brooks Ky

    Actually some of the smartest people aren't the most educated ones or the people who can express their thoughts the best. I always get a good laugh when Jeopardy contestants can tell you that the third cousin of the 2nd Emporer was the first known human to ever have a pimple on his ass..........then can't tell you what car company produced the "Regal" or answer a simple sports question. I remember one show where they had a column devoted to the NFL.
    Not one contestant could answer even one question in the whole column and Alex Trebec even laughed about it.
    One of my favorite expressions is "Knowledge is of little use until experience has given it meaning" and there is a heck of a lot of experience on this site. The smart engineers at work were the ones who went down to the shop and talked to the experienced people before making decisions. One of the smartest guys I knew was a skinny country bumkin sounding guy. Had an inate sense for mechanical things and could fix anything. Met a lot of people in my life who could string words together but clueless about the real world. Had a young asian girl who hired into our office. She graduated magna or summa cum laude. Saw her in the parking lot with her hood up. Asked if she needed any help.
    Not wanting to admit that some old geezer might know something she didn't, she declined my offer of assistance.
    She was simply adding oil to her engine. Turns out she put the oil in her radiator. Apparently did it more than once and ruined her motor. So, to me the ability to "conjugate a verb" is of less importance on this site than the well intentioned and usually good natured sharing of experiences.

    There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves
    Will Rogers
     
    X-cpe and 427 sleeper like this.
  4. ^^^ Boy, I have a file on my computer for one liners, and today I'm getting a bunch of 'em! :D
     
  5. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,281

    Blues4U
    Member
    from So Cal

    Sorry, nice write up and all, but I disagree. If the guy can't communicate the information so it makes sense, then all his knowledge and experience doesn't amount to a hill of beans to the guy who needs help.

    Too often on this forum people offer advice that because either they don't know what they are talking about to begin with, or they are passing along bad information (old wive's tales & urban myths), or they can't formulate an sentence to save their life, or a combination of all the above, just adds confusion for the OP; they have him doing things that offer no help, and often the advice is contradicting. 1 guys tells him to do one thing, another tells him to do the exact opposite.

    If you've been around for awhile you learn to identify those guys here that know what they are talking about and who offer good advice. Some folks should lay back and allow those guys to answer the questions. Or take the time to write their posts in unambiguous language, and know what the hell they are talking about. Don't just repeat bad info you picked up from somebody else!

    On a gun site I used to frequent, the forum members were very self regulating; if someone passes along bad info (or FUD as they called it, for Fear, Uncertainty & Doubt), the other forum members would jump on the person with the bad advice and he'd be forced to back up his statements or withdraw them. The message was clear, know what you're talking about or keep quiet and stop passing bad info around. This forum could stand some of that.
     
  6. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 668

    ekimneirbo
    Member
    from Brooks Ky

    I'm not an expert, but I would disagree with that statement. The reason the pinion needs to be below the rear of the transmission is because as torque is applied the rear end has a natural tendency to rotate ONLY upwards. As long as a vehicle is operating in a range that this natural rise/rotation of the pinion only reaches or SLIGHTLY exceeds the plane of the transmission, there are generally no problems. Basically you have a small range of angular operation that gives good results.
    If you mount a rear end so that it sits above the transmission, you will place the ujoint in position that it starts out at the far end of a good operating range. As torque is applied, the pinion will still want to rotate upward and make the angle even worse. For want of a better word, I'll call it "overcenter". and binding. All of this is in relation to a rearend mounted on leaf springs......
    So my point is that there is a major difference between having the rear ends pinion lower than the back of the transmission and having it higher than the back of the transmission simply because the movement of the rear end is ALWAYS ....UP. Yep there may be extreme situations where you manage to get the rear wheels in the air or top out upward travel of your vehicle momentarily......but in general all major movement will be upward due to torque rotation or spring travel.
    3 degrees has proven to work well as a starting point for most leaf spring applications. Doesn't mean that other minor changes to that angle won't provide satisfactory results. In your description of your truck now having only a 1.5 degree driveshaft angle because you lowered it, remember that the physical angle your engine/tranny is mounted in the frame did not change. You merely changed your driveshafts angle because you rasied the pinions vertical location. I wonder if the angle of the pinion changed during lowering. Its possible that your pinions angle did not change just because you lowered the truck. The driveshaft angle is not the same as the pinion angle and the transmission angle.
     
  7. You can disagree, but you'll be wrong...
     
  8. rooman
    Joined: Sep 20, 2006
    Posts: 3,803

    rooman
    Member

    I do have just a bit of a clue about the dynamics of drivelines and what happens with various different suspension packages so I do know that the "driveshaft angle is not the same as the pinion angle and the transmission angle". I simply was noting that moving the rear end up 6" with the pinion angle staying the same resulted in very little driveshaft angle relative to the transmission output/crank centerline etc. The truck was not on flat ground so what I measured was the difference between the engine and driveshaft.

    As previously discussed it is not uncommon for a highly modified vehicle to have the driveshaft running up from the transmission to the rear end and if that vehicle has leaf springs as the sole locating device for the rear end it would probably be a good idea to have the pinion angle set at a little less than the engine angle. If the vehicle has ladder bars/truck arms etc it depends on whether the car squats or separates under hard acceleration as to which way the pinion angle should be biased. As for stating that the pinion needs to be below the transmission, if that results in wildly different u-joint angles at the opposite ends of the driveshaft the exercise is self defeating.
    And to prove that I may just possibly have a clue about chassis dynamics maybe you should check out some of the cars that I have built. They are waaayyy off topic for the HAMB but here are a couple of links:




    Roo
     
    dan31 likes this.
  9. rooman
    Joined: Sep 20, 2006
    Posts: 3,803

    rooman
    Member

    ^^^^^^ Sorry! I did not want the videos to show up--just the links :(

    Roo
     
  10. pitman
    Joined: May 14, 2006
    Posts: 4,746

    pitman
    Member
    from Hampsha

    When a thread contains wisdom, from the likes of Andy, Roo & Crazy Steve it's a good read. ;)
     
  11. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,828

    Bandit Billy
    ALLIANCE MEMBER

  12. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 668

    ekimneirbo
    Member
    from Brooks Ky

    The OP asked a question about a street driven vehicle which needs to have movement through a limited range in order keep the u joints lubricated and within an operating range that doesn't cause vibration or excessive wear. The relationship between the transmission is relative to the rear end/pinion angle. The rotation of the pinion will always be upward due to applied torque. The movement will generally be upward due to weight transfer and spring movement. Generally you aren't going to have a rearend that is higher in the chassis than the tranny because the frame and rear sheetmetal don't physically allow room for it. Even after moving the rear end in your truck upward 6", you still have a downward driveshaft when at rest.
    For general daily driven vehicles the 3 degree angle is proven and works well. If you build a specialized vehicle that is designed for different purposes....such as racing, you most likely do things differently because you are trying to extract every bit of available HP and get it through the drivetrain. The most efficient angle here would be zero and
    you would have a highly evolved suspension system. Ujoint longevity is a secondary consideration, and even a certain amount of vibration can be acceptable. You can raise the rear of the transmission instead of lowering it and place the rear higher than the transmission if needed because of larger tires. All these things can be mechanically made to function for specialized situations. Whatever you build for, you have to maintain a prestablished relationship between the trans and pinion that fits the situation you are building for. The point is that if the setup you build allows for rotational movement of the rear pinion (leaf springs) the plane of the pinion should always be lower than the plane of the transmission.....even if the trans is pointed upward. The rear can be placed above the transmission causing a downhill slant to the driveshaft but the plane of pinion operation should still be parallel to the transmission angle. If you use a properly designed 4 link adjusted to the instant center and not allowing any wrap up of the pinion, then you want zero angle and you can mount the rear as high or low as the situation dictates.
    That is not the best condition for a daily driven vehicle and most likely would only be used when a situation dictates that the builder must work around an existing condition. Dare I mention all the pneumatic and hydraulic suspended monstrosities that put driveshafts at rediculous angles. Yes, they still work, but at a cost to longivity.
    Lots of things work while racing.



     
    Last edited: Aug 12, 2019
  13. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,844

    Ebbsspeed
    ALLIANCE MEMBER

    31Vwah, you might want to re-think the comment about pinions.

    Since I'm a self-proclaimed asshole (and confirmed by many others) I like to throw in the following diagram to further confuse the issue about driveshaft angles. Note that, while the upper configuration is what we're used to in most single driveshaft automotive applications, the lower "W" configuration is also valid. Equal and same, or equal but opposite angles in a driveshaft configuration will both eliminate the cyclical pulses created when torque is transmitted through an angled U-Joint.
    Ujoint configurations.png
     
    31Vicky with a hemi and Andy like this.
  14. Total of 3 to 6 Deg over all, there are tapered rear spring shims that are used to kick the rear end snout down.
     
  15. F-ONE
    Joined: Mar 27, 2008
    Posts: 1,910

    F-ONE
    Member
    from Alabama

    The OP is talking about a '48 Mercury Truck with a pre 1973 F100 9 " rear axle.

    Has anyone bothered to take a look under one of these trucks, either a F1 or a 60s F100?

    I have just got back from looking under two examples (1950 F1 with a Dana 41 and a 1965 F100 with a 9") that are pertinent to the OPs question. What I found is rather interesting.

    1950 F1....
    [​IMG]Untitled by Travis Brown, on Flickr
    [​IMG]Untitled by Travis Brown, on Flickr
    The 1950 F1 Dana 41 as you can see, has an upward cant.
    The transmission has a slight downward cant.

    1965 F100
    [​IMG]Untitled by Travis Brown, on Flickr
    [​IMG]Untitled by Travis Brown, on Flickr
    The 9" seems to have slightly more of an upward pinion angle than the Dana41.
    The transmission yoke photo does not show the angles well.
    [​IMG]
    This cartoon is cute and it illustrates a point.
    My point is, that's not how Ford did it on these trucks.
    In 1950 and in 1965, the pinion is pointing to the transmission output. In both trucks the driveshaft is inline with the angle of the rear axle.
    Now the engine and transmission seem to be mounted like the lower or "Right" illustration with just a slight cant to the pinion but not pointing straight to it like in the "Wrong" illustration.
    1965 F100
    [​IMG]Untitled by Travis Brown, on Flickr
    1950 F1
    [​IMG]Untitled by Travis Brown, on Flickr
     
    Dusty-NZ likes this.
  16. rooman
    Joined: Sep 20, 2006
    Posts: 3,803

    rooman
    Member

    ekimneirbo,
    at no point did I suggest that the race cars that I illustrated had any direct reference to the subject being discussed. I was simply trying to prove that I have experience at engineering vehicles that operate in an extreme environment. That said, the street can be tougher on some aspects of vehicle structure and dynamics than a race track which is generally not populated with chuck holes, large bumps, etc.
    You state that "The rear can be placed above the transmission causing a downhill slant to the driveshaft but the plane of pinion operation should still be parallel to the transmission angle." I have never stated otherwise. Putting the pinion nose down relative to the transmission will help under hard acceleration if the springs wind up but the most constant condition is running down the road under relative light load so surely that is when you want the angles to be optimum. This applies no matter what the height of the pinion is relative to the trans output with the caveat that with the pinion higher than the trans the U joint angularity will increase rather than decrease under torque load/suspension travel. As long as that increase is within acceptable limits there should be no problems.

    Roo
     
  17. “ Engines don’t have pinions “
    Hummm I’ve not heard, read or seen everything
    But out of all I have heard read or seen I’ve never come across an “engine pinion”
     
  18. O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions O-pinions.:D
     
  19. Someone should draw this configuration up.
     
  20. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,865

    2OLD2FAST
    Member
    from illinois

    Just lay ' em out on the table boys , then we'll know who's is bigger !!
     
  21. No,,, last time we did that some dipshit walked in and ordered the buffet
     
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  22. X-cpe
    Joined: Mar 9, 2018
    Posts: 786

    X-cpe

    We're chasing a dynamic problem with a solution that we can only quantify statically. I call it a 99% solution because time and experience have given us a set of parameters that will work with the fewest anomalies. Of course there are cases where we can go outside those parameters and still get satisfactory results. As shown here there are extreme design and/or operating conditions where our 99% solution won't work. Those solutions generally only work within a very narrow operating range.

    As far as how articulate some posters are or are not, I found a long time ago that you have to read on a forum for a while and determine for yourself who knows what they are talking about and who should be kept away from sharp objects and not be allowed to reproduce.
     
    seb fontana and 2OLD2FAST like this.
  23. blowby
    Joined: Dec 27, 2012
    Posts: 6,188

    blowby
    Member
    from Nicasio Ca

    The Ford truck video showing rear joint angle change is enlightening. As it changes, the front joint (which we can't see) also changes, as evidenced by the angle of the shaft compared to the fuel tank seam, which I assume offers some compensation. Probably some mathematical way to figure out how much, depending on the length of the pinion and the shaft.
     
  24. Kan Kustom
    Joined: Jul 20, 2009
    Posts: 2,339

    Kan Kustom
    Member

    I hate the arguments and slams but I like all the input so I can decide for myself from all offered.
     
    X-cpe likes this.
  25. jimgoetz
    Joined: Sep 6, 2013
    Posts: 356

    jimgoetz
    Member

    Yea but what about cowl steering?
     
    Blues4U likes this.
  26. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,865

    2OLD2FAST
    Member
    from illinois

    Confrontation is what keeps you alive !!
     
  27. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,844

    Ebbsspeed
    ALLIANCE MEMBER

    My understanding is that a pinion gear is any smaller gear that drives a larger gear, so a gear drive for a cam would have a pinion gear. Lots of other "pinion" applications in engines if you go beyond the scope of a typical automobile engine.
     
  28. That’s it,
    and although some basic principles need to be followed each build will be different.
     
    Johnny Gee likes this.
  29. Ok
    Let’s pretend for a moment that you and I are building an engine and I’m your assistant. You’re about to install the timing set and would you really ask me for “the pinion” gear. ,,,,
     
  30. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,828

    Bandit Billy
    ALLIANCE MEMBER

    upload_2019-8-13_9-39-26.png
     
    31Vicky with a hemi likes this.

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