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Thread: Car Tow Dolly Build

  1. #1
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    Car Tow Dolly Build

    Needed something to tow my my rig around. so i decided to build a car dolly.
    hubs are from a 95 jeep cherokee.
    fenders and hitch from princess auto.
    Attached Thumbnails Attached Thumbnails IMG_0859.jpg   IMG_0821.jpg   IMG_0850.jpg   IMG_0800.jpg   IMG_0806.jpg  

    IMG_0843.jpg   IMG_0769.jpg  

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    id love to see alot ok pics on this build and maybe even some drawings with some dimentions and what your using for steel as this is on my list of things to build....
    If its a mechanical device i can fix it

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    some more pictures. autocad and solidwoks drawing too.
    Attached Thumbnails Attached Thumbnails IMG_0767.jpg   IMG_0798.jpg   IMG_0870.jpg   IMG_0863.jpg   IMG_0869.jpg  

    IMG_0853.jpg   IMG_0855.jpg   IMG_0865.jpg   IMG_0851.jpg  

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    The hubs are from the front of a 1995 jeep cherokee. had to use a plasma torch to cut U- joints off. ( be careful, don't let them get too hot)
    The " drums" parts of steel are all 3/8 in thikness as well as the big plate ( overkill maybe). i also used the plasma cutter for the holes that the hubs sit in.
    The hubs are bolted in with grade 12.9 bolts and torqued to 90flbs. All tubed steel is 1/4, rear piece is 2x3" and all the rest is 2x2". The four blue pieces are 1-1/4".

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    does the part where the tires sit turn? everyone i have seen in the past turns so that it handles corners and wavy roads properly, i was under the understanding that was a must for it to tow properly at all

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    The tongue has to pivot or you will be dragging the car dolly tires sideways around corners watching the hubs rip off.

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    Ya, you're missing a big part here. The platform the wheels sit on must pivot in the center or you'll run the very real risk of the car popping up and off the trailer. This works in a straight line only.

    Think of it this way; When you turn, you're going to pull the tongue sideways. Now think of a car on the trailer, and you push the tongue sideways (literally 90). The trailer will try and spit out from under the car.

    ---------- Post added at 10:02 PM ---------- Previous post was at 09:52 PM ----------

    I should add that I've seen trailers built this way and they will tow, but you cannot take sharp corners with it.

    I was just thinking of the best way to use your platform. Easiest solution would be to make a second platform that sits on a center pivot. Put some rollers where the wheels sit so the platform has support on the outer edges but can move without friction. Make sure you add your tie-downs to the movable section of the trailer. Have a look at a u-haul trailer. I took pictures of the one I rented but I can't find 'em now. It's actually pretty simple when you see it.
    ....-Noltz
    '91 Frankenheep Edition. 4.0, 4" BDS, Richmond 8.8, 35" KM2's, Titan 12k, ... gone.
    '95 4Runner SR5. Air-Lift bags, OBA & 8K Winch, DD... gone.

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    wow. ok. good thing you said something. got to re think this.

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    The only other way I can think of, and I've never seen it, is to make the wheels on the dolly steerable. Pivot the tongue, attach tie rods. When you turn, the tongue will follow the towing vehicle. Tie rods to steering knuckles on the trailer, the tongue will push/pull the tires to follow the towing vehicle. 2 problems though; You'll have to make sure the trailer isn't over-wide if you add knuckles to it, and the steering angles will have to be figured out. Too close to the pivot, and you'll get insufficient turning. Too far away, and you'll get the trailer trying to turn tighter than the towing vehicle. This is called Ackermann steering angles. You can look up tables I think, or make the "inner" tie rod position adjustable and drive it until it feels right.


    Little paint action here;

    Last edited by Noltz; 04-26-2010 at 12:35 AM.

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    i borrowed one like that once, and it towed pretty good but seemed like it woulda been alot of work to make so i never took pics of it unfortunatly

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    I wouldn't start over. You just need a central pivot and a big plate on top where the vehicle wheels will sit




    badass tj " Hey bro I would really like 2 grab tht rear end."

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    what do you use for the piviot? would a big bolt work?

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    Not sure, don't forget that's got to support a lot of g's when you hammer on the brakes as well as the pivoting wearing on it.

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    I just leave the steering unlocked on the pulled vehicle ,never had a problem .

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    if i were you i'd swap the hubs out for rebuildable/greaseable/full float d44 or larger hubs.

    dana 30 hubs shit the bed on a monthly basis from standard driving. glad to see you kept the stub shafts in at least so the hub doesn't separate

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    bruces, i tried that and for what ever reason if i turned at an intersection the wheels didnt want to straighten back out

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    i\m going to go with a pivot. its going to raise the height, but i'm not worried about it. i'm going calculate the shear stress for the pin (school taught me something).
    And yes, i had to keep the stub shafts in or the loaded bearing would separate, this is key.

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    id be interested in what you end up using for a pin and your new drawings and lots more pics!

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    If the vehicle deceleration rate is 20 fpsps, 6.1m/s^2. Max towed vehicle weight of 5000lbs, 2269.96kg. Giving a stopping force of f=13834.56N. Safety factor of 4, F=55338.24N
    Max single shear stress in plane of ISO R898 Class 10.9 bolt, grade 8 bolt; 130000psi, 896318.45 KPa. T(tau)=Force/ area; area=F/T. Area =61.74x10^-6 (m^2)
    Area(bolt)=pie/4 x D^2. D= diameter; 0.00886618 m; 8.866mm.
    Therefore minimum bolt diameter with a safety factor of 4 is 8.9mm with a grade 8 bolt.

    Probly go with 12mm grade 12.9 bolt (overkill)

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    Is that going to be sufficient for repeated sheer? Seems to me that the U-haul units were built on a hub of some sort.

    I also read that some guys were using 2 sheets of polymer that were greased between, for the slip plates. Given the light duty application (3-6 uses per year) this would probably be a lot less expensive than getting a plate of roller bearings.

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