Hitchmaster Q (1 Viewer)

[juane]

The company does not recommend mounting their D035 under the drawbar.
But I can't see what difference it would make in terms of stress.
The trailer pulls fine with the under mount.
By mounting the hitch under the bar I gain necessary clearance for my spare tire swing out and it helps to level the trailer.
The trailer weighs maybe 1500 pounds loaded. I'm guessing the tongue weight is a couple hundred pounds.
What am I missing?

 

[80t0ylc]

I would say, the only valid explanation for their recommendation would come from Hitchmaster. Any one else would be guessing. I agree with your analysis about stress. It shouldn't matter.

 

[clrussell]

I run one of these on my expo trailer.

It is mounted under for clearance. Mine also weighs roughly 1500lb and tongue weight is close to yours.

It’s been 10,000 miles and zero issue. I love the hitch.

 

[juane]

Just the info I was looking for.
Thanks gents.

 

[ntsqd]

By putting it under rather than over you're reversing which bolts are in tension and which are in compression (although it's more of a bending thing than a compression thing). The way that the mfg suggests puts the longer bolts in tension. Putting it under means that the shorter bolts are in tension. Why this matters is because short bolts can not elastically stretch as far as longer bolts can. Say that either bolt will stretch .001" per inch of length at some impulse loading that is far above the actual trailer tongue weight. If that impulse is high enough the shorter bolts will exceed their elastic limit and snap. The longer bolts won't snap until an even larger impulse is experienced.

Is this going to matter? I doubt it.

Now knowing what the failure mode could be, if it bothers you the simple solution is to make some solid spacers where the two short bolts are located and use two more bolts of the same length as the longer pair of bolts.

 

[juane]

By putting it under rather than over you're reversing which bolts are in tension and which are in compression (although it's more of a bending thing than a compression thing). The way that the mfg suggests puts the longer bolts in tension. Putting it under means that the shorter bolts are in tension. Why this matters is because short bolts can not elastically stretch as far as longer bolts can. Say that either bolt will stretch .001" per inch of length at some impulse loading that is far above the actual trailer tongue weight. If that impulse is high enough the shorter bolts will exceed their elastic limit and snap. The longer bolts won't snap until an even larger impulse is experienced.

Is this going to matter? I doubt it.

Now knowing what the failure mode could be, if it bothers you the simple solution is to make some solid spacers where the two short bolts are located and use two more bolts of the same length as the longer pair of bolts.

Woa! I get it. Your explanation makes perfect sense. Thanks for taking the time.