[PSUBS-MAILIST] SHOCK!!

[Sean T. Stevenson via Personal_Submersibles]

3-4% is very low. Guideline is 9% to 15% for tongue load, with 12% being the sweet spot, but I would try to either move the load or add additional weight forward to get it up to 9%.  Sway is a safety issue. Spring stiffness is more of a comfort / ride quality issue, which is secondary.

Sean


-------- Original Message --------
On Tuesday, 10/14/25 at 12:26 Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Speed...highway speeds, 65-70mph, 104-112kph.

Tongue weight...that's a long story.  It's a dual axle (tandom) and was originally 10% with the submarine loaded slightly forward of the front axle.  But this resulted in the equalizer (between spring sets) being offset toward the front axle, not "equal".  The result was about 6mm of clearance at the front side of the equalizer and 3-4 inches of clearance at the back side of the equalizer, causing the trailer frame to bang hard against the equalizer when going over the slightest bump.  On a long trip it wouldn't last long.  To combat this, I slid the submarine rearward until the equalizer was equally spaced from the frame on both sides which results in the submarine being positioned directly over both axles.  This solved the frame banging on the equalizer since there was now enough distance (about 2-3 inches) between both ends of the equalizer and the frame.  However, in this configuration because the submarine is directly over both axles the tongue weight is near zero (maybe 25 pounds at most).  I can literally pick up the tongue and rock the trailer up and down.  I took it this way to Michigan and the trailer still tracked very well with zero sway, but it resulted in a bumpy ride at the hitch which made for a rough ride inside the truck.  Since that trip and prior to heading south this week, I added about 250 pounds in front of the submarine but behind the hitch.  I did not measure but I'm guessing my tongue weight is now somewhere around 3-4%, still low, I know, but it was enough to result in a much smoother ride and I did not notice any lifting or bumping at the hitch.  The remaining issue is that when traveling at highway speeds and traversing a large enough pothole, or transition from road to bridge where in many cases there is a mismatch in road level (think speed bump) the energy will cause significant bouncing up and down of the trailer at the wheels.  Sometimes looks like a pogo stick in the rear view mirror.

I can't change the position of the submarine or else the equalizer between springs won't be equal and I'll risk severe banging of the equalizer parts against the frame of the trailer.  I know that will cause failure of bolts and other parts eventually.  I could add more weight at the front to get more tongue weight, but even with my original configuration that gave me 10% tongue weight (I measured it) the bouncing of the trailer was still significant over a large bump.  There's just a LOT of weight (4500) lbs concentrated in a relatively small area over the axles.

Jon




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