Cycle trailer mounts, pros and cons

Chalo said:

I am trying to buy, build, or adapt a bike trailer for my
electric-assist bike. It will carry 60-80 lbs. of batteries at all
times and hopefully will have room for some groceries. I expect speeds
of 25mph or more, so the trailer's handling qualities at speed are my
greatest concern. I wish to solicit input from those who have used
trailers, in order to help me narrow my choices down to one general
mounting point and pivot location. The trailers I have seen to date
fall into one of three categories:

1) seatpost mount (e.g. CycleTote)
2) left chainstay and/or seatstay mount (e.g. Burley Flatbed)
3) axle mount, rear pivot (e.g. B.O.B. Yak)

<snip>

Quoted message said:

A seatpost hitch would allow the use of a single-wheel trailer, if that
is much preferable to a two-wheeled trailer handling-wise. I had even
considered stripping down a Trail-a-Bike or the like to just the frame
and wheel, and mounting my batteries on the frame. The drawback there
is that I would be left with little or no space for cargo.

I appreciate all relevant input.

Chalo

Hi Chalo,

two suggestions:

A minor advantage of a seatpost mount is that the draw-bar is at the
right height to be used as a handle when manouvering the trailer away
from the bike - it's effectively a hand-cart.

With a single wheel, located at the read of the trailer, the weight of
the trailer (say 80lbs batteries, 30lbs trailer, 30lbs other cargo)
will be split pretty evenly between the hitch and the wheel, so
nominally 70lbs on each, and this is not really tunable (though you
could change the length of the drawbar, or move the heavier part of the
load nearer the trailer wheel).
With two wheels on the trailer, you can move the mounts back and
forward on the frame to tune the amount of weight on the hitch. This
may make handling the trailer easier when it's not attached to the
bike. Additionally, when towing a boat with a car, it's normal to move
the wheel position so that the vertical load on the hitch is about
10-12% of the weight of he trailer + load - this amount tunes out
shimmy at most common speeds. This may also be applicable in the bike
+ trailer application.

hth,

bookieb.

Chalo said:

I am trying to buy, build, or adapt a bike trailer for my
electric-assist bike. It will carry 60-80 lbs. of batteries at all
times and hopefully will have room for some groceries. I expect speeds
of 25mph or more, so the trailer's handling qualities at speed are my
greatest concern. I wish to solicit input from those who have used
trailers, in order to help me narrow my choices down to one general
mounting point and pivot location. The trailers I have seen to date
fall into one of three categories:

1) seatpost mount (e.g. CycleTote)
2) left chainstay and/or seatstay mount (e.g. Burley Flatbed)
3) axle mount, rear pivot (e.g. B.O.B. Yak)

Right up front I think it is best to eliminate trailers of the third
category, since the swinging rear-mounted pivot looks like an
invitation to chronic shimmy problems at the speeds I will be
traveling. Furthermore, I'm using a SRAM 7-speed gearhub whose right
axle nut is enclosed by the shifting mechanism and will not be a
feasible location for BOB Nutz or anything like them.

Mounting a trailer of the second type will be complicated: The bike's
stays are elliptical in cross-section and curved along their length,
and thus they present a less-than-ideal place to clamp a hitch mount.
The left side axle stub is short, and it is more or less taken up by a
thick anti-rotation washer. I would have to machine a new part that
functions both as an anti-rotation washer and as a trailer hitch if I
opt to use a trailer that attaches to the rear axle. However, to me it
looks like this mounting location might be the best one insofar as it
may impose the smallest steering forces upon the bicycle.

The least complicated prospective mounting point, mechanically
speaking, is the seatpost. It would be easy for me to make or buy a
satisfactory and secure trailer with a hitch of this type. My concern
with it is that the pivot point will be high on the bike and not
especially close to the bike's yaw axis (which I assume to be a line
passing through the rear contact patch and the rear hub). I'm curious
what effect a seatpost hitch may have on the bike's handling and
stability.

A seatpost hitch would allow the use of a single-wheel trailer, if that
is much preferable to a two-wheeled trailer handling-wise. I had even
considered stripping down a Trail-a-Bike or the like to just the frame
and wheel, and mounting my batteries on the frame. The drawback there
is that I would be left with little or no space for cargo.

I appreciate all relevant input.

Chalo

I have ridden many miles with both a BOB and a trailer-bike. I haven't
ever loaded the BOB beyond 30 lb or so, though. The trailer-bike carried
my daughter until she was a bit over the 90 lb weight limit. Although I
used both on the road, the bulk of my riding was off road, usually on
pretty challenging terrain, things like single track hiking trails and
ski slopes. I exceeded speeds of 25 mph frequently (sometimes while
airborne).

I never noticed any shimmy with either attachment. Just as with regular
bike handling, low speed balance was trickier than high speed -- in fact
I never really noticed the load except when pulling uphill. The high
mount of the trailer-bike didn't really seem to present any special
difficulty, the only flaw was the development of play in the hitch,
which caused the trailer to "flop". My daughter actually became adept at
keeping the trailer-bike flopped to on side, which turned the slop in
the hitch from a liability to an asset. This was an early model Adams
Trail-a-bike, I know they've redesigned the hitch since.

I don't know how important it is for your purposes, but I found the
single-wheeled trailers to be very agile for snaking around trees and
sharp turns. They also worked well in congested urban settings. Backing
up the combo is pretty difficult, though. Under hard braking, especially
on loose surfaces, the trailer-bike had a tendency to jackknife, I don't
know if 2-wheel trailers are superior in that aspect, I found that
modifying braking technique (using more rear brake) was adequate to
control this. I've never crashed either trailer, except the few times
when I bottomed the BOB in rocky gullies or logs (hard enough to bend
the frame). Both trailers have absorbed a lot of abuse.

As far as hitch attachments go, I don't have a strong preference, they
both seem to work. The locking pins on the BOB are a little Mickey
Mouse, I've lost a couple, but found it's easy enough to form
replacements from old spokes. I like the ability to move the BOB between
bikes just by swapping the skewer. I understand your problem with the
geared hub cable though. I suppose it would be possible to machine up an
alternate hitch aft of the axle, the BOB skewers are nothing special,
just a rotating bushing and a thru-bolt.

Quoted message said:

The least complicated prospective mounting point, mechanically
speaking, is the seatpost. It would be easy for me to make or buy a
satisfactory and secure trailer with a hitch of this type. My concern
with it is that the pivot point will be high on the bike and not
especially close to the bike's yaw axis (which I assume to be a line
passing through the rear contact patch and the rear hub). I'm curious
what effect a seatpost hitch may have on the bike's handling and
stability.

A seatpost hitch would allow the use of a single-wheel trailer, if that
is much preferable to a two-wheeled trailer handling-wise. I had even
considered stripping down a Trail-a-Bike or the like to just the frame
and wheel, and mounting my batteries on the frame. The drawback there
is that I would be left with little or no space for cargo.

I appreciate all relevant input.

Chalo

I have been using a cycletote for a few years. I use to take my dog to
the park. He weights ~55 lbs. I used it to move one time. I moved a
1.5 mi away and the trailer moved almost everything. I use it when I
do landscaping as part time job. The tongue makes a handy handle as was
mentioned by someone else. I used it the other day with 10 2cuft bags
of mulch loaded in it. The trailer has been great. I have never
experienced shimmy. never had any handling problems that I can think
of. I don't think that seat post mount creates any handling problems.
Of course someone will write to tell us otherwise. I've gone pretty
fast with my dog in the trailer with no handling problems. You've
probably thought of it but a kickstand is really nice thing to have
with a trailer.

Quoting Peter Cole <[email hidden]>:

Quoted message said:

Chalo said:

The least complicated prospective mounting point, mechanically
speaking, is the seatpost.

The obvious difficulty with seatpost mountings is that the hitch has to
clear any rear luggage rack. I bought a new trailer that did not have this
property, and eventually bolted on the hitch from my old trailer instead.

Quoted message said:

up the combo is pretty difficult, though. Under hard braking, especially
on loose surfaces, the trailer-bike had a tendency to jackknife, I don't
know if 2-wheel trailers are superior in that aspect,

2-wheel trailers are pretty hopeless on rough terrain, given their
tendency to flip on bumps - especially at speed. A 2-wheel trailer is really
suitable for pulling relatively large loads slowly on tarmac; bringing the
groceries home at 15mph, or whatever. I would always use a 1-wheel
trailer if I wanted to travel long distances and descend at speed.
--
David Damerell <[email hidden]> Kill the tomato!
Today is Tuesday, June.

Chalo said:

I am trying to buy, build, or adapt a bike trailer for my
electric-assist bike. It will carry 60-80 lbs. of batteries at all
times and hopefully will have room for some groceries. I expect speeds
of 25mph or more, so the trailer's handling qualities at speed are my
greatest concern. I wish to solicit input from those who have used
trailers, in order to help me narrow my choices down to one general
mounting point and pivot location. The trailers I have seen to date
fall into one of three categories:

1) seatpost mount (e.g. CycleTote)
2) left chainstay and/or seatstay mount (e.g. Burley Flatbed)
3) axle mount, rear pivot (e.g. B.O.B. Yak)

Right up front I think it is best to eliminate trailers of the third
category, since the swinging rear-mounted pivot looks like an
invitation to chronic shimmy problems at the speeds I will be
traveling. Furthermore, I'm using a SRAM 7-speed gearhub whose right
axle nut is enclosed by the shifting mechanism and will not be a
feasible location for BOB Nutz or anything like them.

Mounting a trailer of the second type will be complicated: The bike's
stays are elliptical in cross-section and curved along their length,
and thus they present a less-than-ideal place to clamp a hitch mount.
The left side axle stub is short, and it is more or less taken up by a
thick anti-rotation washer. I would have to machine a new part that
functions both as an anti-rotation washer and as a trailer hitch if I
opt to use a trailer that attaches to the rear axle. However, to me it
looks like this mounting location might be the best one insofar as it
may impose the smallest steering forces upon the bicycle.

The least complicated prospective mounting point, mechanically
speaking, is the seatpost. It would be easy for me to make or buy a
satisfactory and secure trailer with a hitch of this type. My concern
with it is that the pivot point will be high on the bike and not
especially close to the bike's yaw axis (which I assume to be a line
passing through the rear contact patch and the rear hub). I'm curious
what effect a seatpost hitch may have on the bike's handling and
stability.

A seatpost hitch would allow the use of a single-wheel trailer, if that
is much preferable to a two-wheeled trailer handling-wise. I had even
considered stripping down a Trail-a-Bike or the like to just the frame
and wheel, and mounting my batteries on the frame. The drawback there
is that I would be left with little or no space for cargo.

I appreciate all relevant input.

Chalo

Dear Chalo,

A trailer behind an electric bicycle at 25 mph with its own weight,
plus 60-80 pounds of batteries, plus groceries, sounds like about 100
pounds or so of trailer waiting to jack-knife both sideways and
upwards when you grab the front brake and cause a crash.

That's why heavy car trailers often feature automatic braking. You can
see them at any rental/hardware place where people buy a cubic yard of
concrete. Without the trailer's automatic brakes, customers jack-knife
at stop signs.

For ideas about connecting a heavy trailer, you might stop by a
motorcycle shop and see what they do with huge street cruisers that
tow trailers. I've seen them on highways, but never looked at the
details of how they connect.

For what it's worth, a small modern motorcycle engine may not be what
you want, but it will weigh less than 60-80 pounds of batteries, fit
in the frame, and easily produce 25 mph with groceries in panniers and
the luggage rack.

Cheers,

Carl Fogel

bookieb said:

Chalo said:

I am trying to buy, build, or adapt a bike trailer for my
electric-assist bike. It will carry 60-80 lbs. of batteries at all
times and hopefully will have room for some groceries. I expect speeds
of 25mph or more, so the trailer's handling qualities at speed are my
greatest concern. I wish to solicit input from those who have used
trailers, in order to help me narrow my choices down to one general
mounting point and pivot location. The trailers I have seen to date
fall into one of three categories:

1) seatpost mount (e.g. CycleTote)
2) left chainstay and/or seatstay mount (e.g. Burley Flatbed)
3) axle mount, rear pivot (e.g. B.O.B. Yak)

<snip>

Quoted message said:

A seatpost hitch would allow the use of a single-wheel trailer, if that
is much preferable to a two-wheeled trailer handling-wise. I had even
considered stripping down a Trail-a-Bike or the like to just the frame
and wheel, and mounting my batteries on the frame. The drawback there
is that I would be left with little or no space for cargo.

I appreciate all relevant input.

Chalo

Hi Chalo,

two suggestions:

A minor advantage of a seatpost mount is that the draw-bar is at the
right height to be used as a handle when manouvering the trailer away
from the bike - it's effectively a hand-cart.

With a single wheel, located at the read of the trailer, the weight of
the trailer (say 80lbs batteries, 30lbs trailer, 30lbs other cargo)
will be split pretty evenly between the hitch and the wheel, so
nominally 70lbs on each, and this is not really tunable (though you
could change the length of the drawbar, or move the heavier part of the
load nearer the trailer wheel).

Conventional one wheel trailers (i.e. BOB) are, as you say, minimally
tunable. With the payload of interest (batteries and groceries) and a
custom designed trailer, I think you could tune the weight distribution.
I don't know why you couldn't have the payload ahead, beside, and behind
the wheel.

Quoted message said:

Additionally, when towing a boat with a car, it's normal to move
the wheel position so that the vertical load on the hitch is about
10-12% of the weight of he trailer + load - this amount tunes out
shimmy at most common speeds. This may also be applicable in the bike
+ trailer application.

Interesting idea. I've never experienced shimmy in a bike + trailer
system, though, so I don't think it's worth the effort to optimize the
load distribution.

--
Dave
dvt at psu dot edu

joshua said:

You've
probably thought of it but a kickstand is really nice thing to have
with a trailer.

That's not a bad tip.

If you park on rough terrain (i.e. grass), you can use the trailer as a
kickstand. Rotate the bike 90° from the trailer, lean the bike against
the trailer, and use the lumps in the ground to keep the trailer from
rolling.

A lockable brake on the trailer wheel (it wouldn't have to be very
strong) would make this work on smooth pavement, too.

--
Dave
dvt at psu dot edu

Chalo said:

I am trying to buy, build, or adapt a bike trailer for my
electric-assist bike. It will carry 60-80 lbs. of batteries at all
times and hopefully will have room for some groceries. I expect speeds
of 25mph or more, so the trailer's handling qualities at speed are my
greatest concern.

I've used trailers with all three mounting types. I have found little
difference in the handling depending on the attachment point.

I have pulled a trailer with similar mass to your batteries for quite a
number of miles, and I continue to do so frequently. It has a seatpost
mount. I've pulled that trailer well over 25 mph many times (downhill,
of course). There has been no hint of shimmy.

I've noticed no tendency to jacknife. I've had to brake quite hard as I
cornered because a pedestrian stepped out in front of me. I've also
tested the brakes on a straight run. If these conditions didn't show a
tendency to jacknife, I don't think it's likely to happen.

I think a seatpost mount would work quite well for you, assuming the
bike up front could handle the combined load of the trailer and your
substantial weight.

For more authoritative info, you should head over to
http://bikesatwork.com/hauling-cargo-by-bike/bicycle-trailer-guide.html.
They think that a seatpost mount has some disadvantages for heavy loads,
but I think their definition of heavy load is quite a bit higher than
you're considering.

--
Dave
dvt at psu dot edu

carlfogel said:

A trailer behind an electric bicycle at 25 mph with its own weight,
plus 60-80 pounds of batteries, plus groceries, sounds like about 100
pounds or so of trailer waiting to jack-knife both sideways and
upwards when you grab the front brake and cause a crash.

I wonder if that would make it a better idea to hitch the trailer below
the hubs of the bicycle (easy since it has 700x60 tires) or even below
the hubs of the trailer. In that case, there would be no tendency for
the hitch to buckle upwards in compression.

Quoted message said:

That's why heavy car trailers often feature automatic braking. You can
see them at any rental/hardware place where people buy a cubic yard of
concrete. Without the trailer's automatic brakes, customers jack-knife
at stop signs.

Cycletote offers that option, at an added cost greater than that of
most entire trailers. It would be easy enough for me to make a plunger
mechanism to pull the trailer's brakes if I choose to build my own
trailer. It's probably a good idea in light of the underwhelming drum
brake on the rear of my bike.

Quoted message said:

For ideas about connecting a heavy trailer, you might stop by a
motorcycle shop and see what they do with huge street cruisers that
tow trailers. I've seen them on highways, but never looked at the
details of how they connect.

All of those I've seen mount a small ball hitch behind the rear fender,
for a pivot location similar to that of a BOB. Unlike a BOB, though,
M/C trailers are two-wheeled, which I'm sure presents a number of
operational differences.

Quoted message said:

For what it's worth, a small modern motorcycle engine may not be what
you want, but it will weigh less than 60-80 pounds of batteries, fit
in the frame, and easily produce 25 mph with groceries in panniers and
the luggage rack.

There are a number of advantages these days to electric-assist bikes.
They require no license, registration, or insurance; they are allowed
to use bicycle and pedestrian rights-of-way; and they are often allowed
indoors where ICE bikes are not. They run cool and almost silent, and
they don't stink.

I have a satisfyingly capable 1100cc motorcycle, but I haven't ridden
it in a long time. Between my pushbikes, my electric bike, and my
sweetie's vintage Benz, it seems I almost always have a more appealing
alternative for in-city travel.

Chalo

dvt said:

I have pulled a trailer with similar mass to your batteries for quite a
number of miles, and I continue to do so frequently. It has a seatpost
mount. I've pulled that trailer well over 25 mph many times (downhill,
of course). There has been no hint of shimmy.

What kind of hitch does that trailer use?

Quoted message said:

I think a seatpost mount would work quite well for you, assuming the
bike up front could handle the combined load of the trailer and your
substantial weight.

I'm not worried about this particular bike frame or seatpost (a Redline
Monocog 29er and a welded chromoly post). They are both heavy steel
and quite sturdy. I want to increase my battery capacity while
reducing the load on the rear wheel, which is mainly why I'm looking at
a trailer.

Quoted message said:

For more authoritative info, you should head over to
http://bikesatwork.com/hauling-cargo-by-bike/bicycle-trailer-guide.html.

Thanks for the link.

Chalo

David Damerell said:

The obvious difficulty with seatpost mountings is that the hitch has to
clear any rear luggage rack. I bought a new trailer that did not have this
property, and eventually bolted on the hitch from my old trailer instead.

My new frame has no furniture whatsoever for racks or fenders, so
compatibility with a rear rack is not an initial concern for me. If I
ever decide to ride the thing without its battery trailer (doubtful due
to the bike's 22 pound front hub with lots of magnetic drag), a
Carradice bag strapped to the BMX bars should handle any necessary
carrying duties.

Thanks for your input.

Chalo

Chalo said:

carlfogel wrote:

Quoted message said:

Quoted message said:

For ideas about connecting a heavy trailer, you might stop by a
motorcycle shop and see what they do with huge street cruisers that
tow trailers. I've seen them on highways, but never looked at the
details of how they connect.

All of those I've seen mount a small ball hitch behind the rear fender,
for a pivot location similar to that of a BOB. Unlike a BOB, though,
M/C trailers are two-wheeled, which I'm sure presents a number of
operational differences.

Chalo, there are indeed one-wheeled MC trailers. It makes a lot of
sense for a single-track vehicle.

http://www.uni-go.com/index.html

http://www.monogo.com/Anglais/index_Enter.php

http://www.n-line.com/trailers.htm

--
Ted Bennett

Chalo said:

carlfogel said:

That's why heavy car trailers often feature automatic braking. You can
see them at any rental/hardware place where people buy a cubic yard of
concrete. Without the trailer's automatic brakes, customers jack-knife
at stop signs.

Cycletote offers that option, at an added cost greater than that of
most entire trailers. It would be easy enough for me to make a plunger
mechanism to pull the trailer's brakes if I choose to build my own
trailer. It's probably a good idea in light of the underwhelming drum
brake on the rear of my bike.

The rear brake on your bike will be quite useful when you add the
trailer. If your drum brake is barely sufficient now, you might consider
beefing it up. A trailer brake might be the best solution, but I think
it would be much easier to use a stronger brake on the rear wheel of the
bike.

--
Dave
dvt at psu dot edu

Chalo said:

dvt said:

I have pulled a trailer with similar mass to your batteries for quite a
number of miles, and I continue to do so frequently. It has a seatpost
mount. I've pulled that trailer well over 25 mph many times (downhill,
of course). There has been no hint of shimmy.

What kind of hitch does that trailer use?

I was unable to find a photo after a few minutes of looking, so I'll try
to describe it. To the seatpost of my bike is attached a fixture with a
square rod extending aft. The trailer has a square socket that fits over
that square rod. When they are mated, a pin fits through both socket and
rod to hold them together.

Just aft of this rod 'n socket joint is a U-joint that allows the
trailer to rotate about 2 axes. The trailer can pitch and yaw
independently of my bike, but the roll of bike and trailer is fixed.

I hope that's clear.

--
Dave
dvt at psu dot edu

dvt said:

Chalo said:

What kind of hitch does that trailer use?

I was unable to find a photo after a few minutes of looking, so I'll try
to describe it. To the seatpost of my bike is attached a fixture with a
square rod extending aft. The trailer has a square socket that fits over
that square rod. When they are mated, a pin fits through both socket and
rod to hold them together.

Just aft of this rod 'n socket joint is a U-joint that allows the
trailer to rotate about 2 axes. The trailer can pitch and yaw
independently of my bike, but the roll of bike and trailer is fixed.

Like this?

http://sheldonbrown.com/harris/adams-trail-a-bike.html#hitch

Chalo

Chalo said:

dvt said:

Chalo said:

What kind of hitch does that trailer use?

Quoted message said:

Quoted message said:

I was unable to find a photo after a few minutes of looking, so I'll try
to describe it. To the seatpost of my bike is attached a fixture with a
square rod extending aft. The trailer has a square socket that fits over
that square rod. When they are mated, a pin fits through both socket and
rod to hold them together.

Just aft of this rod 'n socket joint is a U-joint that allows the
trailer to rotate about 2 axes. The trailer can pitch and yaw
independently of my bike, but the roll of bike and trailer is fixed.

Like this?

http://sheldonbrown.com/harris/adams-trail-a-bike.html#hitch

Yup, that looks pretty similar to mine. Sheldon, is "solider" a word? :^)

The trailer that I had which connected to the rear seat stay and chain
stay was a pain in the butt to connect/disconnect. I replaced that
connection with a skewer connection, which was much more convenient.

The current trailer, with a hitch as described above, may be slightly
less convenient than the skewer connection. The square post/socket must
be a pretty tight fit to prevent independent roll. Since it's a tight
fit, they don't always slide together easily while I'm trying to balance
the bike and the trailer. Once connected, it's a very good system.

None of that may apply to you, since you'll probably hitch up the
trailer and leave it connected most of the time.

--
Dave
dvt at psu dot edu

dvt said:

Chalo said:

dvt said:

Chalo wrote:
> What kind of hitch does that trailer use?

Quoted message said:

Quoted message said:

I was unable to find a photo after a few minutes of looking, so I'll try
to describe it. To the seatpost of my bike is attached a fixture with a
square rod extending aft. The trailer has a square socket that fits over
that square rod. When they are mated, a pin fits through both socket and
rod to hold them together.

Just aft of this rod 'n socket joint is a U-joint that allows the
trailer to rotate about 2 axes. The trailer can pitch and yaw
independently of my bike, but the roll of bike and trailer is fixed.

Like this?

http://sheldonbrown.com/harris/adams-trail-a-bike.html#hitch

Yup, that looks pretty similar to mine. Sheldon, is "solider" a word? :^)

Dear Dave,

Let us soldier on past the obvious dyslexic pun . . .

(Google for solider and you'll be surprised at our free-and-easy
orthographic attitude toward the military.)

Let us also ignore the Shakespearean word-play involved in wishing
that this too too sallied/sullied/solid flesh would melt, thaw, and
resolve itself into a dew/adieu . . .

(Hamlet talking about resolve is a nice touch, hidden in the all the
other puns.)

And remember that Sheldon provides us with enormous amounts of better,
faster, cheaper, and nicelier-indexed bicycle information than anyone
else.

(Er, more nicely-indexed.)

Cheers,

Carl Fogeler