Weight Calculations

[klr650goldwing]

My son has a Dutchman (24QB)24' 4500 lb TT. He wants to haul a 300lb motorcycle on the back of the trailer. How much will that motorcycle decrease tongue weight?

[MFL]

Back of a TT??? NOPE...tell son to forget that idea! Best look at other options.

Jerry

[noteven]

Plus the added moment of inertia added to the yaw or "sway" axis.

Weight added to the ass end of a RV trailer is always A Bad Thing because they are already built like a teeter totter / weather vane with their little wheels halfway up the frame.

[Lwiddis]

Excellent analysis.

[valhalla360]

I throw some ballpark numbers around. Update them based on your specifics and you will get a fairly good approximation.

Let's say total current length is 25ft and the center of the axles is 15ft behind the hitch. The center of gravity of the bike and rack will sit 13ft behind the center of the axles. The rack will weigh 200lb.

Assuming the starting hitch weight is a healthy 15% and loaded for travel it weighs in at around 6500lb (assuming 4500 is the empty weight) results in a hitch weight of 975lb to start.

You are adding 500lb (bike and rack) should take about 433lb off the hitch leaving a hitch weight of 541lb which is around 7.7% hitch weight. That's way below the 12-15% recommended.

PS: This ignores the question if if the frame can even handle the weight. If it takes a lot of beefing up, it could easily result in the rack being 300-400lb. You also have to consider if the axles are spec'd to handle the load. In the original situation, if the weight = 6500lb with a 975lb hitch weight, the axles only have to carry 5525lb. If they put a pair 3000lb axles on that's fine. But with the bike on the back, the axles are now expected to carry 6658lb out of the now 7000lb loaded trailer. That would mean overloaded axles.

Assuming he is towing with a capable pickup, a better option would be to put the bike into the truck bed. Obviously, he would need an extra 300lb of payload but it would only require some straps/blocks to hold it in place and the trailer itself would never be compromised.

[Boomerweps]

schlep1967 wrote:
I would also question the frame strength of the camper to have that weight bouncing around back there.

Strongly concur. He’ll need some significant frame/bumper reinforcement. Best to haul the motorcycle in the truck bed, if possible.
There are many tales of bumper to frame weld breaks destroying a 3 to 4 bicycle rack load.

[Lwiddis]

Was the trailer built for an additional 300+ pounds at the rear? Tongue weight decrease isn’t the only consideration. How much weight will the rack add to the 300 pounds?

[schlep1967]

At most you are going to get some guesses on this one. To mathematically figure it out you would need exact length from the coupler to the center pivot point of the axles and from the pivot point of the axles to where the bike will be hanging on the rear. You will also need the weight of whatever apparatus will be used to hold the bike.
I would also question the frame strength of the camper to have that weight bouncing around back there.