On Wed, 02 Apr 2008 16:33:00 GMT, Winston
wrote:
RainLover wrote:

Hey everyone,
I want to build a trailer that my motorcycle can tow.

James, my sedan is in the shop right now getting a new transmission.

See, I figured I would save a mint by towing stuff in a trailer rather than renting or
borrowing a truck.

That misapprehension will cost me U$3600 (Three thousand six hundred dollars) this afternoon.

Even at Silicon Valley prices, I could have rented and gassed a truck for over *fifty*
(50) trips for that amount of moolah. (Sad when you consider I rented trailers a total of
four (4) times.)

Please learn from my mistake.

--Winston

Picking on "Winston" section:

Enlighten us about your 'mistake', Winston - What kind of sedan,
what kind of trailer? Age, powertrain type and mileage on the car?
If it already had 150,000 miles on the typical automatic, the
transmission going out may well have been normal wear and tear, and
the trailer may not have had anything AT ALL to do with the failure.
Or you didn't know to TAKE IT EASY when towing at the ragged edge of
vehicle capacity, and killed it through abuse.

Clue: When it was my daily driver, I towed small trailers all the
time for years with a 61 Corvair - 102 HP air-cooled (fan forced) and
2-speed Powerglide. When done correctly size is not a consideration,
you just have to remember to leave plenty of room.

Did you have an auxiliary transmission cooler on the car? The one
in the radiator is not enough if you are towing.

(I had to change the transmission rear cover on the Corvair to a
Truck/Greenbrier rear cover to get the trans cooler fittings - Car
cases didn't have the fittings, just a bypass slot.)

Did the trailer you were using have brakes? Same thing, it's a
given on large trailers towed with large cars (Legally Required on any
trailer over 2,000# - 3,500# - check your state laws) but should be
installed on small ones towed by small cars. It saves both the car's
brakes and the transmission if you were downshifting too much and too
hard.

* * * * * * * * * * * *

General Design thoughts section:

Rainlover: What kind of bike do you plan to use for towing? Liquid
or air cooled? Wet or dry clutch? Can you install larger radiators
and/or fans? Aux oil cooler? Aux trans oil cooler (if it's a divided
sump)?

Can you get an oversized charging coil (alternator) for it? (They
do make them for Harleys, big Beemers and Kawasaki 1100, the extra
juice is needed to run the radios and lights on police bikes.)

They started making small trailer axles with brakes (both electric
and surge) for large tent trailers, the same brake parts can be
applied to a ~36" - ~48" wide axle for a motorcycle trailer. You call
up Dexter Axle or one of the other actual trailer axle makers and tell
them exactly what you want, give them a Credit Card, and in a week or
three a truck pulls up to your house with a big heavy box.

The usual tackle for that size trailer would be 4.80X8" tires on 8"
x 3-1/2" rims, 4 on 4" stud spacing, and they would give you 1080
pounds capacity for trailer and cargo. Using 4.80X12" tires gives you
a lot more room for brake drums (and a bit more weight capacity) but
would raise the trailer up a bit.

Those two standard size tires are available almost anywhere (Wal-
Mart etc.) if you blow one, but you still want to carry a spare.

And if you want the Center of Gravity to stay really low, they make
rubber torsion-box suspension axles (Dexter "Torflex") rather than
standard leaf springs & slippers - though you have to watch your
chassis design (and make the main rails a bit heavier) as there is a
much higher torsional load since it's one attachment point ahead of
the wheel center line.

You can even get the rubber spindle/suspension units as two separate
stubs without an axle shaft between them, and have the box/bed between
them practically on the ground - this is how they build the "Drop-bed"
utility trailers that lower onto the pavement. But that's going to
produce even higher torsional loads on the chassis rails, which will
need to be stress engineered so it won't make like a pretzel going
down the road - which is bad...

No surge brakes on something that small, I've never seen a tongue
for them that will swivel... And you really do need a way to activate
the trailer brakes by hand that surge just won't do - unless you trip
the breakaway arm, but that's a one-shot deal.

You could go with the new "Electric Hydraulic" brakes (Carlisle
"Hydrastar" or Dexter Axle "ElecDraulic") if you can take a ~20-pound
weight penalty for the electric pump unit on the trailer (and find a
place to put it) - they use hydraulic disc brakes on the trailer axle
that are a lot easier to maintain.

The electric brake controller could be a bit tricky to spec on a
motorcycle, I would NOT use a straight inertia controller - it might
mis-read the front fork dive and over-brake the trailer. And the
'Sandwich' pressure sensor that goes on top of the brake pedal is out,
it won't fit on the brake lever.

They still make the kind of electric trailer brake controller that
has a pressure sensor that tee-taps into the brake lines for a
proportional braking signal, but I'm not sure whether you would tap it
off the front or rear brake circuit on a motorcycle - your hands are
trained that when the rear of the bike gets squirrely you ease off the
back brakes, and IMO that might not be the right instinct if a trailer
started to jackknife and push the rear end around.

When a trailer starts getting squirrely behind you, you want to
apply MORE trailer brakes (up to lock-up) to get it back in line. And
if you have room you ease off the tow vehicle brakes till it quiets
down - but not if you are in a Panic Stop situation.

You might want to remote the "Panic Button" for the electric trailer
brakes "Full ON" to a thumb button (like the horn) you can stab while
keeping both hands on the grips. On a car it's a lever or a button on
the front of the brake controller under the dash, but taking a hand
off the bars in a panic situation could be a very bad idea.

-- Bruce --