Re: Trailering boat with motor or not?

[johnyrude200]

You’re spot on…that flexing is physics. It’s like taking a flat piece of sheet metal and applying force to one edge (not to get heady) in a way perpendicular to the horizontal surface. Point of axis is the tires…lever is length from that to the aft of the motor…longer distance equals more force, but I would consider the rivets of the transom to the be the axis point, even though the lever is short.

The X factor is the momentum of the vehicle and flex of the vertical transom with weight. So technically the moment arm is almost nothing, perhaps 1/4-1/2 inch flex of the transom, but with such a light material and the introduction of velocity, just isn’t worth it in my opinion. There are many structural mechanics converging at once on a transom, but keep in mind the material is aluminum and generally 1/16th – 1/8th in thickness. Not that beefy.

Just imagine the way glass installers move a mirror…they carry it vertically…NEVER horizontally…because the strength is along the length/width, never the DEPTH.

A transom with a motor is the same idea…force being applied to the depth when forward movement/displacement is introduced (i.e. driving in ANY direction).

I have repaired/replaced so many stern brackets for the broken motor mounts due to customers transporting their motors to me without a transom saver. I admit, I almost constantly look at my 2014 etec (30hp on a 2001 14′ aluminum starcraft…tiller) and watch the motor ‘snapping’ back and forth every time I jump a wave or chop. I wonder how long before the rubber motor mounts snap in half. And that motor is 182lbs…not a light motor at all!

If you want to have some fun thinking about physics, think about how easy it is to lift your bow when you have all your gear in the back on a trailer. That’s a 1st class lever (pivot ponit is the trailer tires), basically the same as a see-saw. Try lifting the bow in the same situation by moving closer to the boat, away from the tongue. It will feel much heavier the closer you get.

We all use ‘cheater’ bars when trying to pull flywheels? Why? By increasing the lever arm (the longer handle), we put physics into our favor from a mathemetical standpoint. The pivot point is the center of the crank. The further distance you get from the axis point, the greater the mechanical advantage (or lower the disadvantage).