Hensley/ProPride Length and Tongue Weight

[dkottum]

The Hensley/Propride hitch adds about an extra foot to the effective distance of the truck receiver to the trailer axle(s), compared to a conventional hitch. It seems to me the trailer tongue weight on the truck receiver may be reduced, similar to a longer "lever" used to lift the tongue of the trailer.

I don't know if it's possible to get a comparison with a tongue weight scale, but most people have greater math skills than I. So, would the additional 12 inches distance from the truck receiver to the trailer axle(s) decrease the effective weight of the trailer tongue on the truck receiver?

The reason I ask the question is the Hensley/Propride adds about 125 lbs more to the tongue weight than most conventional hitches. Perhaps some of that extra weight is mitigated by the additional length?

doug k

[overlander63]

No, it adds about 125 pounds to the tongue weight. Since the tongue rests on it, it adds the weight to the receiver, not the tongue.

[JFScheck]

It's that added weight of the yoke assembly that results in only about 150lbs of the tongue weight being brought back upon the trailers axles.

So, you move 300lbs tongue weight back to the trailer but add the 125lbs of the yoke assembly for an overall net of 175lbs....

Of course, this is fuzzy napkin math - but I think everyone get's our point here....

The truth can only be revealed upon the scales....

[Ron Gratz]

100% of any weight added forward of the ball will be added to the vertical load on the receiver.

Approximately 90% of any weight added rearward of the ball (yoke, jacks, cross member, etc.) also will be added to the load on the receiver.
The remaining approximately 10% will be carried on the trailer's axles.

The 12" added length will place the ball about 20% farther behind the TV's rear axle.
This means the load removed from the TV's front axle, due to the trailer's tongue weight, will be increased by about 20%.

A load equal to about 50% of the added weight of the hitch also will be removed from the TV's front axle with no WD applied.

Ron

[dkottum]

Thanks Ron, you are the math genius here. And as usual with math, now I'm really confused.

So, if w.d was applied to return the front axle to it's unhitched weight, would the weight on the rear axle be increased or decreased by the additional 12" length between the tow vehicle axle and the trailer axle (not considering the additional weight of the Propride hitch).

My question boils down to: "With w.d. applied, is the entire 125 lbs additional weight of the Propride hitch added to the truck's payload, or is it altered by the fact that the trailer is now 12" further back from the truck?"

doug k

[SteveH]

Doug,

I believe it is added to the truck load, and at least that was the way I was calculating it back when I was contemplating going to a 1/2 ton truck. As a result, I could not get the 1/2 ton to come in under weight with the 31' and all the stuff we normally carry.

[Ron Gratz]

Originally Posted by dkottum

So, if w.d was applied to return the front axle to it's unhitched weight, would the weight on the rear axle be increased or decreased by the additional 12" length between the tow vehicle axle and the trailer axle (not considering the additional weight of the Propride hitch).

After application of WD to return the front to its unhitched load,
and not considering the added hitch weight,
the additional 12" length would cause the rear axle load to be increased by about 1%.
Short answer -- no significant difference.

My question boils down to: "With w.d. applied, is the entire 125 lbs additional weight of the Propride hitch added to the truck's payload, or is it altered by the fact that the trailer is now 12" further back from the truck?"

If you add 12" to the ball overhang distance
and add 125# of hitch weight
and restore the front axle to its unhitched load,
the load on the TV's rear axle will increase by about 105#.

Ron

[dkottum]

So a 225# Propride/Hensley adds about 105# more to the truck payload than a 100# conventional hitch?

doug k

[Ron Gratz]

Originally Posted by dkottum

So a 225# Propride/Hensley adds about 105# more to the truck payload than a 100# conventional hitch?

Yes, the assumed additional 125# plus the extra 12" length will add about 105#.

The actual value will depend on distance from TV rear axle to ball and distance from ball to mid-point between TT axles,
but should be in the range of 82-86% of added weight for most TV/TT combinations, when the WDH is adjusted to return the front axle to its unhitched load.

Ron

[Tomzstream]

Wow, 25% heavier and 4x more expensive than my Equal-i-zer. But what would concern me most is that extra space between the tail of the truck and the trailer. Has anybody calculated the additional aerodynamic drag that creates? I would think the closer the trailer the better the draft effect.

[dkottum]

Ron, thanks for the calculations I never dream of doing. Really appreciate it and it may be useful when looking at payload, perhaps the most limiting factor on many potential tow vehicles.

Tomzstream, having used both Equal-I-Zer and and Propride on our Airstream, if there is additional aerodynamic drag we didn't notice it. We did notice the improvement in the towing experience though. You might think things are pretty good until you use one of these and learn immediately how good towing can be.

doug k

[slowmover]

Originally Posted by Tomzstream

Wow, 25% heavier and 4x more expensive than my Equal-i-zer. But what would concern me most is that extra space between the tail of the truck and the trailer. Has anybody calculated the additional aerodynamic drag that creates? I would think the closer the trailer the better the draft effect.

If one could keep the gap to below 30" there would be an aero benefit. But no hitch arrangement/type makes this possible. Airflow off of the TV and TT frontal shape are what are in contention past side winds. A TV that cleanly sheds wind and a bullet nosed trailer with a boat-tail rear would be "best". In the meantime, low ground clearance and radused edges of 12-22 degrees are what determine TT aero, as well as an enclosed underside.

How well the TT handles all types of winds -- natural or man-made and from any direction -- not just 60-mph airflow over the length of the combined rig, is what matters overall. Wide roll center independent suspension is the icing on that cake (strong resistance to tripping hazards).

OTOH, the reduction of side-to-side movement of the TT by the PULLRITE or VPP hitch types will make for fewer steering corrections to keep the rig lane-centered in all circumstances (a measurement cited by the big truck industry as being critical to fuel economy per 100-miles of operation).

Getting WD dialled in on a certified, segmented scale is central to this no matter the actual hitch (as well as tire pressures/loads per individual wheel position). Moving TW around is no challenge overall. But pursuing best steering and handling by the combined rig (past straight-line braking) is where the action is . . literally, where the rubber meets the road.

.

[Tomzstream]

SlowMo, Not sure where you cam up with the 30 inch rule. But it seems to me the extent of benefit obtained by the trailer drafting a TV decrease exponentially with the distance from the TV, so another 25% increase in distance lets say, will result in a greater than 25% reduction in benefit.

I can only offer anecdotal evidence, but in my testing, improving the air flow off the TV does have a beneficial effect in my setup (see photos below). I use an equal-i-zer brand hitch which keeps the trailer pretty snug (as much as it can be), against the truck, and I have just enough clearance to lower the tailgate without rubbing the trailers's hitch jack (so would not want to get any closer anyway.)

Equally important is to reduce turbulence as it creates drag on the TV from behind. No need to discuss the shape of the trailer as we all know airstream was designed for good aerodynamics. My cargo box lifts air up to the height of the TT quite well (have observed from the side driving down the road in a rainstorm, much like a wind tunnel test). I get about 1-2 better MPG with the box on at hwy speeds.

Speaking of wind, I have an anemometer which I mount on the roof rack of my TV that I can use to monitor windspeed (and direction when standing still) so I can gauge my true airspeed and adjust my roadspeed accordingly.

Per the sway, I get no appreciable sway using a E brand hitch. All I know is it works well for me and I still have an extra 2K in my wallet that I would not have otherwise if I took your recommendation.

You'll note in the photos, I am not hitched up, these were taken just to give an idea as to the profile of the two vehicles relative to each other. The distance between is accurate.

[slowmover]

Nice post, Tomzstream. The pics and description are welcomed. My further comments are general, not specific to your posts.

The 30" gap is from tractor-trailer studies, and at an outer range. 24" as a maximum is preferred where gap devices are in use. The penalty climbs substantially from that point. The gap on mine is at 60". (Same source as with steering corrections per 100-miles being worthwhile to lessen for measurable FE gains).

Thus far there don't seem to be any hard & fast "fixes" to the TV-TT gap outside of what owners attempt (as you have done; or others with a canoe over the truck/topper; some others with wind deflectors). The problem is mainly one of testing (as A-B-B-A is the standard where all other things are the same). Most of us won't quite gain enough to make even this low level of rigor applicable as mechanical changes (mainly aero and gearing) won't benefit the driver not also committed to driver skill attainment.

The complementary step (in skill attainment where lowest fuel burn is desireable) is in The Trip Plan: all stops (rest, food & fuel) are planned in advance with an eye to keeping average mph at the highest level (relative to travel speed; they are different). From engine start to engine stop for the day. As most of us may travel but 300-400 miles/day this is not difficult given online resources especially where an Interstate highway is the path. This is where safety (best practice) meets low fuel consumption. A win-win.

So, to finish this line of thinking, stick with records of all gallons & all miles to determine overall average mpg (with an eye to average mph) and make notes of climate, terrain & traffic conditions (road type) for purposes of prediction. When one converts the average to fuel cost cents-per-mile has predictive capability reached a useable form. (see signature; based on $4/gl diesel).

As to how well your hitch works, one can follow your rig and video-record the instances of how the combined rig is out of alignment one with the other. It will be. A VPP hitch brings these same instances to nil. And this is in windless conditions. There is a difference -- for purposes of FE -- between sway mitigation and sway elimination per hitch operation and reduction of both steering input by number and by force exerted. The goal can be stated as: lane-centered under all conditions where the least amount of force/time/distance of driver inputs keeps the rig aligned for all circumstances.

So to take this back to the topic, where:

"If you add 12" to the ball overhang distance
and add 125# of hitch weight
and restore the front axle to its unhitched load,
the load on the TV's rear axle will increase by about 105#."

The leverage/payload "penalty" is minor, AND as the TV-TT gap is already beyond aerodynamic optimum, the sway elimination benefts of the VPP hitch are in force such that other considerations are outweighed.

For road performance -- all aspects -- the TT was the main choice. The TV is second, and some types are better than others as is true for the TT. The hitch is icing on the cake. But differences between drivers can account for more than 30% of fuel consumption all other things the same (and this among professional drivers).

The tool -- whether Airstream or Interstate -- calls for learning best use. Best tool, alone, is only part way.

.

[Tomzstream]

In terms of planning, knowing which direction the wind will be blowing and going with the flow is the best technique as far as I know, but of course this requires a lot of flexibility in your travel plans. Still I try to do just that when I can. Wind can be a real mileage killer when its out of the wrong direction. That's the primary reason I use an anemometer. I can always justify getting somewhere a little later if it means saving big bucks in gas. When without my weather tools, I look to flagpoles for an indication.

One of the nice things about my travel box is I can position it further back to close the gap somewhat, but I prefer to keep the front snug to reduce turbulence up front.

Thanks for all the background info!

[slowmover]

You're welcome. Context is all when it comes to how to use dollars to best effect.

Note here in this GM press release how the wind goes over the truck bed. "Fill in" the area under that curve for best mpg. (See also "Aerolid" for images).

While I wouldn't plan for winds, per se (our rigs are already good), it is more a matter of using the biggest road for the longest period of time even when distance is slightly more (say up to 30-miles), or, where avoiding stop-n-go is preferred (alternate routes to major metro areas; in this case time of day is worth consideration. Consider the radius to extend 100-miles in all directions as truck distribution from the center, not just commuters, is part of the traffic build-up).

And I'm glad you mentioned that wind speed device again as I meant to ask about it. I've wanted one, but am stymied by where to mount the probe on a vehicle (other than an airplane). Could you give details? Andy Inland RV used an airspeed indicator in his travels and record speed attempts more than forty years ago (search).

.

[switz]

More perhaps fuzzy math.

The trailer has a GVW of 7,300 pounds. The Shureline scales reflect 1,200 pounds tongue weight (includes the Hensley hitch head but not the stinger). So that would mean that the axles are supporting 6,100 pounds when unhitched from the truck when fully loaded, right?

When connected to the truck and loaded for our last trip, CAT scales reflected 5,880 pounds on the trailer axles. So, if I subtract 5,880 from 7,300 that leaves 1,420 pounds. Then deduct the 1,200 pound tongue weight. Would that calculation mean there was about 220 pounds of available load that could be added to the trailer?

If the 1/3 of the tongue weight when hitched to the trailer and 2/3 to the truck ratio is true, then the 5,880 CAT weight would include 400 pounds of the tongue weight and one could carry an additional 800 pounds in the trailer?

I miss a turn on the race course here. Anyone with any ideas?

I think I might acquire an eight pad portable scale to discover these actual weights as well as the left right balance. I am sure others would appreciate the opportunity to discover what is actually happening to their rig rather than blindly assuming all is well.

[ROBERT CROSS]

Switz,

A multiple run CAT scale procedure, plus the Sureline tongue weight has served me well over the years.

The Sureline gave me an accurate tongue weight for a loaded for camping trailer.
The no WD weight gave me the trailer axle weights, and the baseline unloaded TV front axle weight.
The max WD weight gave me the maximum transfer weight to the front TV axle.
Several WD adjusted weights gave me the correct settings for towing, and the loaded TV axle weights.
I base my TV/AS payload on the axle and tire ratings, not the stated factory numbers.

Our Classic has two 3500lb axles with a GVWR of 7300lbs so I'm very conscious of trailer weight, very little wiggle room their….like none, my balanced loaded trailer axle weight is 7640lbs, 340lbs over the axle rating.

BTW Airstream has seen fit to equip some of the newer units with axles of higher ratings for improved CCC. YMMV....Check to be sure.

Bob

[switz]

Our 2013 25FB Int'l Serenity came with two 3,600 pound rated axles (7,200 pounds for both) with a 7,300 pound GVW. The 15" Michelin LTX (P) 235/75R15 XL tires are rated 3,970 pounds per axle for two of them. So the axles are the limiting load factor for the suspension.

[ROBERT CROSS]

Originally Posted by switz

Our 2013 25FB Int'l Serenity came with two 3,600 pound rated axles (7,200 pounds for both) with a 7,300 pound GVW. The 15" Michelin LTX (P) 235/75R15 XL tires are rated 3,970 pounds per axle for two of them. So the axles are the limiting load factor for the suspension.

Two 3600 pounders, I really thought they did better, but at least it's an improvement.

Bob