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does anybody think this would work?

Discussion in 'The Garage' started by gambit420s, Aug 6, 2005.

  1. gambit420s

    gambit420s 1/2 ton status

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    kind of an extention on K10A'sBROinSLO's thread here
    but i thought i'd throw it out on its own to not hijack his thread anymore

    basically i'm just looking for CONSTRUCTIVE criticism on the idea; not my drawing skills, or lack of extra bearings or gussets, blah, blah ,blah.

    i could use measurments of pinion diameters in the lower(2 and 3 ratio) and upper(6 and 7 ratios) ranges for d60's i'm using ford racing 9" offerings for my base calcs, but i know d60's come in lower gears so thats what i would prefer.

    it seams like it could work, but there are limitations on gear ratio, although i'd think that if you needed that much gear you would be running 50"+ tires and this wouldnt matter. i could see this with 40"-ish tire size as i can only seem to get 4.83 with 2:1 portals. and it seems people are really wanting diff clearance using approx this tire size

    i am not an engineer, machinist, or financial advisor, and i do not currently plan on building this, i am just using this as experiment to try to understand the dynamics of a gear set, and how mutiple reductions and increases will work in an offroad situation. this is a crackpot idea, i know this. but of all the things people talk about on here, building a better/different diff is not one of them.

    i am using a low # ratio gear set (2.84) to a high #(6.86) to allow using the pinion as the drive gear, which would allow a higher case bottom. the hypoid shape of the gears would no doubt have to be custom, as the second pinion would also need to be hollow and splined to allow a shaft to pass through. so there will be a lot of things that would need to be custom fabbed, but again i'm not building this anytime soon.

    save yourself the time of pointing out my faults (bubba you listening?), there will be more bearings on the axle/pinion shaft, an input for pressurized lube, thrust adjustment on the axle/pinion shaft, and i will learn how to draw(and spell too, maybe...)

    with that said here ya go!

    if you care or just want to b/s about this call me (865)388-1890 Adam

    two pinion axle with portal and birfield and lube pump FR profile small.JPG
     
    Last edited: Aug 10, 2005
  2. gambit420s

    gambit420s 1/2 ton status

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    okk so i was thinking about this and with higher speeds the ring gears would rev something fierce and it just seemed counter productive

    but what if the axle drive(formerly ring and pinion B) were just 1:1 ?
    this would make it simpler, more effecient, and less complex and still give you more clearance than a vertical ring gear.

    anyone know about 90* geardrives? so far as load vs gear size/tooth engagement?

    three pinion axle with  lube pump FR profile small.JPG
     
  3. MoonMan

    MoonMan Registered Member

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    I have a few points of constructive criticism for you to think about:

    The first issue is the size and placement of the ring gear package shaft. Since it spans the entire height of the case it will need to be very stiff to avoid deflection under high loads. This is not an impossible task, but now you group that with the fact that it also has to avoid the axle shaft, which in your concept appears to be of a solid design. I do not know how the existing concept could be changed to prevent the ring gear shaft from interfering with the solid axle shaft. Also, if using a once piece axle shaft, with birfields on each end, how would you get it to slide through the axle tubes? I think that the best solution here is to have two separate axle shaft pinions (pinion B) that are set in place on either side of the ring gear and allow conventional splined axle shafts to slide into them. However after rethinking this comment, I realized that this would cause the axles to rotate in opposite directions :doah:

    In my opinion the pinion to ring gear interface is the weakest point of most rear end systems and your concept adds a second one. How would you setup the gears in the two pinion system? I would have to think that it would be very tedious, if not impossible, to get the correct gear lash and wear pattern. The drive axle in the axle tubes is in a stationary, non-adjustable position, therefore the axle pinion (pinion B) to ring gear (b) interface would have to be setup by varying the vertical position of the ring gear package. This is not a difficult task using shims and such. Now that the ring gear package is set in place (though that position is varied based on each individual gear set) you have to setup the input pinion to ring gear package. This will be exceeding difficult to setup since the vertical position of the ring gear package will change with each different ring gear and axle pinion.

    This system will not allow for any type of differential action, therefore dictating a fully locked front end (not undesirable for an off road only vehicle).

    This type of gear setup will create a very tall center section, like a Rockwell front. This may be a possible problem when designing the suspension system.

    The extra bearings, gears, and the like will all add parasitic losses to the drivetrain. Heat may also be a factor in this design since the number of moving parts is significantly higher.

    These are just my general comments after quickly glancing over your concept so take them as such.
     
  4. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Judging from some previous discussions about an "optimal" crawl ratio, a good rule of thumb developed that your crawl ratio should be roughly equivalent to the circumference of your tire.... resulting in a 1"/RPM type ratio.

    It's been a while since I read that thread, but I remember seeing Stephen talking about it as being fairly accurate based on his own experiences with the ORD Jimmy and some of the combinations that he'd tried with it. My own buildup will use a similar method to establish the correct final crawl ratio (something in the 140 range).




    My only comment about a fullsize truck with a 1000:1 crawl ratio is that you may actually run out of fuel before you get a chance to climb the first rock on the trail!!!! :D
     
  5. MoonMan

    MoonMan Registered Member

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    I just saw the part in your post about a crawl ratio of 1006.8:1. How did you get this number? I seem to be coming up with about 125:1, 6.46(tranny) X 4(t-case) X 4.38 (axle) = 124.8 :confused:
     
  6. gambit420s

    gambit420s 1/2 ton status

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    Very true i was also thinking of more of a carrier type spanning section to increase the load displacement
    with the first design the pinion c/l would be offset from the ring c/l but using a 1:1 in the second design would put it directly in the path i'm not sure what to do about this other than shortening the shaft and putting the end into a socket above the axle but i dont know if this would be strong enough.
    the birfields were just a thought as i had seen them around and they seem to be a good idea but i think with a solid axle you would have to use a bolton type yoke on at least one end
    i was thinking the same thing til i did a power flow type drawing... but it would turn great!! :haha:
    i was originally thinking that the spacing of the ring gears could be changed by using shims between the gears, ie: ring B would be set by adjusting the shaft height, and ring A could be spaced up with shims away from ring B, independent of shaft height. even1 now that i have refined the design to eliminate the secondary reduction, and replaced it with a 1:1, this method should still work
    this is also one of my concerns, but i was thinking that it would be easier to make space above the axle, than moving every rock you pass over. it would most def be a balance of trade offs
    the parasitic drag is a concern, but given that most people will have multiple gear reductions before the axle(trans/tc/dbl), it might be less noticable but still a concern. as far as the heat i was thinking of a lube pump, due to the horizontal mount of the ring gear. this could be plumbed through a cooler, and then ran to the gear set

    true true this was just a little math experiment, using the second design with 6.46 1st gear, 4:1 T/C and 5.13 gears its more like 132 but this could be finetuned
     
  7. gambit420s

    gambit420s 1/2 ton status

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    my math was screwy :doah: :screwy: sorry ill fix it up, plus my effective ratio formula was wrong too

    ok well since i went to the second design it just be comes a standard type formula since there is only one reduction but heres what im thinking

    formula table two pinion axle2.JPG
     
    Last edited: Aug 10, 2005
  8. Boondocks

    Boondocks 1/2 ton status

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    If the goal is to reduce the distance from the axle tubes to the bottom of the third member, how about using a front loader housing, turn it so the pinion would point straight up? Then you could bolt on a new pinion and housing assembly that is essentially a 90 degree drive into the third member.

    You could further adjust your final ratio by using different gear sets in the 90 degree drive.

    Of course there will be a lube issue to address for the 90 degree and pinion bearings.
     
  9. gambit420s

    gambit420s 1/2 ton status

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    but using this you would still have the 9"-10.5" ring gear mounted vertically thus giving you 4.5"-5.25"+housing below the c/l of the axle shaft, not much different than stock, although it would be hard to damage the pinion.
     
  10. Boondocks

    Boondocks 1/2 ton status

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    Depending on how you ratio the 90 degree, you could reduce the size of the ring gear and reduce the cover height (drop) to match.

    Question is, how small can you make the spider gear housing?
    Would it be possible to re-orient it, so the ring gear faced away from it?
    If so the ring gear could be reduced to the diameter of the housing?

    Of course this is only necessary if you want to have a limited-slip or locker.
    If not, you could use a very small ring gear.

    My thought is to reduce the complexity and maintain strength.

    It may not get you as much ground clearance, but I'm just throwing it out there as a possible alternative.
     

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