D-tub Towing
As
a 25mph EV, I plan on towing the tub to most locations, and doing so
without endangering myself is one of my highest priorites. I have
a tow braking system that actuates the power brakes on the Chevy truck
whenever I start to decelerate in the tow vehicle (a 1998 GMC Savana
full-size van), and a tow bar that can safely tow 7500 lbs.
Tow Brakes
Tow Brake Selection
Tow Bar
Tow Electrical
Tow Brakes
I'm
using the US Gear Unified Tow Brake, which can be actuated
manually from inside the towing vehicle, with varying force, and uses
an accelerometer for automatic braking from the towed vehicle. It
is actuated by a recessed cylinder w/pulley to pedal, so the brake
pedal can be used even while the tub is being towed , a nice safety
feature.
installation manual Holidays magazine article
Here's the installation diagram:
Tow Brake Selection (in case you're curious)
All of the 4-wheels-on-the-ground braking systems are
designed for RV'ers towing a secondary vehicle, which is usually called
the dinghy or the toad.
Although trailer (or towed vehicle) brakes are required for towing
anything over 1500 lbs in California (3000 in most states), these
brakes don't have to work very well. That's the only reason I can
figure that most of the trailer brake systems do not use the power
brakes
of the towed vehicle. To be sure, with a 15,000 lb motorhome
towing a 3,000 lb car isn't that big of a deal. In my case,
though, an 7500 lb van (which includes 1500 lbs of gear, about right
including my tools) towing a 7500 lb vehicle (the max I can tow, and
my design weight), the brakes on the towed vehicle will make a
huge difference.
For an overview of braking systems, check this out this long-running thread detailing different towed braking systems.
Only three brake systems were considered that utilize the power
brakes on the hot tub vehicle. All other systems on the market
crank up the power applied to the pedal because the pedal is "dead",
ie, unassisted.
Power braking is necessary for the tub because I
want to be able to have a driver in the driver's seat to be able to
brake the system with power brakes, as well as in the tub, with the idea that two brakes are better than one
The
M&G Engineering system was discarded because the
brakes in the towed vehicle can't be applied independently of the
brakes in the towing vehicle, making it impossible to have both a
driver's seat driver and a hot tub driver simultaneously (or, at least,
allow both of them to brake). The Blue Ox ToadStop does not have
a manual brake from the towing vehicle, but otherwise appears very
similar to the US Gear system. Here's a thread discussing the pros and cons of these two systems (nice to know others have also winnowed the list down to these two), and the definitive winner is the US Gear system.
Tow Bar
The tow bar is what
connects the towing vehicle to the hot tub. With a d-tub design
weight of 7500 lbs, I need a class IV tow bar.
All the class IV hitches that I've seen do not swivel
on a tow ball: rather, they have their own swiveling system. From
what I've read, towed vehicles popping off the tow ball are the most
common severe failure with towed vehicles.
It's in such high
demand from RV'ers, I'm not seeing much of a discount on ebay (which is
really turning into a sellers market!). Craigslist has been turning up
some listings, but only a handful are for such a heavy toad vehicle.
I'm thinking I'll buy the Aventa II tow bar, but then fabricate my own
base plate, which will integrate into the bumper on the hot tub.
aventa II: class IV, 10k lbs (according to manual, but some
stickers say 7500lbs?), pin swivel mount (not hitch ball mount or
spherical joint)
need both bars & base plate
$399: http://www.pplmotorhomes.com/parts/rv-tow-bars-dollies/tow-bars-blue-ox-aventa.htm
$299: base plate at
http://www.rvupgradestore.com/index.asp?PageAction=VIEWPROD&ProdID=202
tow bar manual base plate manual
Tow Electrical
tow lights: need isolating diode system $25: http://www.etrailer.com/pc-TBELE~118158.htm
perhaps twin blinkers/running lights for 24V operation