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  1. #11
    Elite Member
    Join Date
    Oct 2004
    Posts
    2,952
    Location
    limerick pa lycoming county pa
    Tractor
    kubota bx23

    Default Re: Tandem Trailer Geometry

    When I was building my trailer I measured quite a few I came across
    To the center of the axel on single axel or center of the equilizer on tandems was from 53% to 58% of the trailer length not including tung for bumper pull's.

    Do like I did drive up to a lot on sunday and break out the tape I measured 3 or 4 different makes at different places and the all came in around that number.

    Note the Landsacper and dovetails trailers don't follow that rule bevause of the gate weight throws them off.

    tom
    If it ain't broke we will help you brake it
    If it is broke we will help you get it fixed!


    https://www.facebook.com/joseph.t.mussington

  2. #12
    Gold Member RWolf's Avatar
    Join Date
    Apr 2008
    Posts
    439
    Location
    Central Texas
    Tractor
    Current, Power King (antique), Soon to have JD 5103

    Default Re: Tandem Trailer Geometry

    When considering GN style tongue weight will increase to about 25% of total weight. That's why when you see a GN you'll see the wheels a bit farther back. I think it was something like 75/25 on my horse trailer.
    2008 5103, FEL, 6ft. HD Box Blade, 6ft. Rotory cutter. And many more to come.

  3. #13
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
    Posts
    18,922
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Tandem Trailer Geometry

    I found this site that might be of interest.

    What makes a good trailer design?
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  4. #14
    Veteran Member powerstroke444e's Avatar
    Join Date
    Jan 2008
    Posts
    1,165
    Location
    Near Springfield IL
    Tractor
    mostly orange

    Default Re: Tandem Trailer Geometry

    If you don't have enough tough weight the average joe homeowner overloads the trailer and the truck jackknifes when he hits the brakes hard because the truck don't have enough weight on the rear tires. When the trailer is 60/40 old Joe homeowner stops loading the trailer when the bumper hits the ground on his not so heavy duty SUV that don't have trailer brakes. Thus if you know what you are doing order what you need.

    This is one of the trailers we have & yes behind a 1/2 ton its easy to overload but behind a 3/4 or 1 ton we put 6 ton plus on this and it handles great.
    Attached Thumbnails Attached Thumbnails Tandem Trailer Geometry-1024081652-jpg  
    If it ain't smokin' it's broken.

  5. #15
    Elite Member
    Join Date
    Nov 2005
    Posts
    3,059

    Default Re: Tandem Trailer Geometry

    I remember a fairly extensive article from someone who had converted a single axle trailer to a tandem.
    Two things have really stuck in my mind about it.
    1) The axles should be spaced evenly forward/backward of where the original single axle was (this was a surprise to me, but he had a LOT of arithmetic to support it).
    2) The center of gravity of a tandem axle trailer is actually AHEAD of the front axle's center line.
    I doubted this too, but took a tape measure to one of my own tandem axle trailers and verified that with 11 or more percent tongue weight this is true.

    All that aside; on gooseneck or 5th wheel trailers it doesn't matter that much, put them wherever you want to to suit the load.
    On a LONG trailer you risk bellying out if they are too far back, tail dragging if they are too far forward.
    Wherever you put them distribute your load to get the right % load on the coupler.

  6. #16
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
    Posts
    19,393
    Location
    Nova Scotia, Canada

    Default Re: Tandem Trailer Geometry

    What type of Boat is that on the trailer Diamondpilot?
    Egon
    50 years behind the times
    Livin in a
    Worn out skin bag filled with rattlin bones

  7. #17
    Super Star Member Diamondpilot's Avatar
    Join Date
    Jan 2007
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    15,922
    Location
    Daleville, IN
    Tractor
    Jinma 254/284 Ford 861 Powermaster at work

    Default Re: Tandem Trailer Geometry

    2003 32' Wellcraft. It is powered by 2 5.0L Volvo engines, 270Hp each. Weighs 15,600# on the trailer full of fuel.

    Chris

  8. #18
    Veteran Member
    Join Date
    Sep 2002
    Posts
    1,033
    Location
    Ohio
    Tractor
    Mahindra 6000 4wd; IH x2; NHTC40DSS; International 1086; JD 5525

    Default Re: Tandem Trailer Geometry

    You also have to remember in the deck over trailers with the dove tail, and large wedge loading ramps like shown on the PJ trailer, you have some weight back their to balance against the front.

    Some of the manufactures now have trailers designe to haul almost as much weight, but come in on the lighter side. 8" I beams instead of 10". Mortiz has 2 series of deck over trailers. Check out their UD series trailer. Moritz International Inc. - Quality Trailers
    It comes in about 1000lbs lighter than the F-series but can haul a pretty good weight. Also, there usually is not much difference in price or weight between a 12gvw and 14gvw trailer.
    Slippy

  9. #19
    Super Star Member Diamondpilot's Avatar
    Join Date
    Jan 2007
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    15,922
    Location
    Daleville, IN
    Tractor
    Jinma 254/284 Ford 861 Powermaster at work

    Default Re: Tandem Trailer Geometry

    One other thing I was thinking of is if you have a trailer with the axles in the middle or there abouts and the load is even on the trailer within reason the tail will wag the dog. What I mean by this is a trailer loaded this way will wag the truck very easily. You have a lot of weigh back there and its a simple leverage thing. With that type of arm you dont need much push to make things rock.

    Chris

  10. #20
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
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    18,922
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Tandem Trailer Geometry

    How many of you think that a balanced load is when the load is centered over the axles. Raise your hands. Now , put them down. Sometimes it is very hard to know when the load is situated right to give the proper towing response, and that is a smooth pull, with no fishtailing, etc. No matter what kind of load you have, you have to consider the load on the tongue, and it should not be above the rated load or above what the hitch is designed for. I believe you can cheat a little if you use the equalizing hitch to get the right load on the front tires, which is where you lose proper steering. The sway bar is another accessory that is useful . Too much weight on the tongue will push the rear end down thereby raising the front wheels, causing steering problems. It does take some effort to get the trailer set up right, be it trial and error, or whatever. I have pulled different kinds of trailers, with different vehicles, and that does not make me an expert, but it is just my opinion on things. Don't forget correct air pressure. But also consider an unloaded trailer being pull a long distance will give a better pull if you let out some air to keep the wheels from hopping and bouncing.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

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