Taking all the good features of each plow and combining them will
produce a unit with the following features:
- Scooter wheels and steel front.
- Vee shape to reduce chances of catching in cracks.
- Folds up for transport.
- Higher profile to get snow up out of trough.
- Wings to shape sides of trough and fling snow farther out.
- Ability to be pushed by hand in deep snow.
- Not too heavy.
- Room for a bucket if additional weight is needed.
- Simplified construction.
See the comments below about my
experience with this plow in January 2005.
The (almost but not
(Or, it seemed like a good idea at
view with wings folded Wings out
looking toward front
By having a 60 degree cut angle on the plywood and a square nose corner
on the base, most of the other assembly angles come out to be 45, 90,
60 or 30. The only tricky angle is the bevel on the edge of the
2x4 that reinforces the bottom of the front. It is 54.7 degrees
from horizontal. One can avoid having to cut this angle by using
thinner wood, such as plywood, and building up the bevel in
layers. There is probably no reason why the reinforcing wood has
to match the angle of the plywood perfectly. Caulk or expandable
foam might help fill in the voids. I had actually considered
building the whole unit out of Styrofoam and then gluing on a thin
plywood or aluminum skin. (Amazingly strong and light model
airplane wings can be made out of foam with a balsa skin.)
I made the sides out of one piece of plywood but decided to hinge them
since the tip to tip spread was a bit wide for most doorways and I
didn't want to catch a tip while the plow was up on the rear
rack. The hinge line is parallel to the nose line so the plow
cuts vertical sides when the wings are folded. This makes the new
plow compatible with deep sided troughs made by the old model seen on
the previous page.
The platform is large enough to match the rearmost extent of the wing
tips. A longer wheelbase might help reduce fishtailing.
This also makes the wing braces simple and provides room for a
bucket. The bucket could hold a few pounds of snow to provide
additional downward force so the nose doesn't ride up. When done
plowing the snow can be dumped out of the bucket so riding with the
plow stowed is not too much work.
The platform will also be outfitted with a brace to hold the tip of a
shovel or the end of the tee handle from the walking push plow so this
unit can be used as a walking push plow when the snow is too deep to
pull it behind the bike.
The axles rest against the bottom of the platform and are captured in
notches in the surrounding blocks of wood.
Plywood - A 24" x 48" piece of 1/4"
exterior grade should be enough. Thicker would be stronger but
heavier. The two sides can be cut from one 12" x 44-3/4"
piece. The bottom uses two pieces cut from one 8-1/2" x 36-1/2"
piece. The leftover plywood is used for diagonal bracing and the
top "splash" panels.
Scooter wheels - the exact size is not
critical as long as they are all the same size and have nice
bearings. You will need three. I used the standard 100 mm
Steel rod - Axel for the scooter wheels. Mine uses 5/16".
Check your wheels. Can be smooth or threaded. One 3 foot piece
should be more than enough.
Steel Flat with holes - 1 piece of 36" x 1-3/8" x (I think) 0.070"
galvanized with 3/8" holes every 3/4".
Steel Flat - 1 piece of 36" x 2" x 1/8". Should be in the same
bin as the strapping. This is for the front cutting edge of the
blade. You could use another piece of strapping or even aluminum
depending on how you want to trade off weight and durability.
Assorted wood - A 2x4 for the nose. 2x2 is good for connecting blocks
and the hitch. 1x2 or similar for the hinge mounting. 1x1 or base
shoe for the edges.
Deck screws - I like the square drive heads. I have boxes of
3/4", 1-5/8", 2" and 3". Make sure they are good exterior grade.
Plastic or other slippery material for the surface. You'll need
about 4 square feet. Should be fairly sturdy but flexible enough
to make curves of a few inch radius. Or if you don't mind the
angles then the wood can just be painted or stained.
Bolts - 3/8" (galvanized or stainless if you don't like rust) 2" or
2-1/2" long. I think four should be enough.
Nuts - Pozi-Lok (tm) or other nylon insert jamming nuts for the
bolts. Get one for each bolt.
Hinges - If you want the wings to fold out of the way you will need
four hinges. 2" or so is a good size.
Clevis pin - 3/8" to use in place of a bolt if you want the hitch to
pivot for transport.
There are probably a few other small items but this will get you just
about fully outfitted.
The Hitch on the Bike
I decided to try making a hitch that
would center the forces and give some symmetry to the installation.
It needs to pivot horizontally, vertically and rotate (not that this
bike ever tips over).
The conduit clamps are joined by a 1/4"-20 bolt with a nylon insert
lock nut. The bolt is tight enough to minimize rattling but loose
enough to allow rotation.
with plow up Hitch
with plow down
The aluminum angles are held against the seat
stays by hose clamps. The aluminum tubing is reinforced by a wooden
dowel inside. The tubes can be loosened so the bottom tips
swing up to provide more ground clearance.
A clevis pin in the small conduit clamp allows for quick release of the
The wooden box on the left side of the bike rack is the shovel holder.
A Really Simple Plow
For those of you needing something
quick and simple. This won't drag you down yet will still get
the snow out of your track.
Scraps of 2x8 will make a plow 10" wide.
Plow Top View
of a Simple Plow
This plow works well to clear enough snow out of the way so the next
bike pulling the main plow can get good traction.
January 2005 started off with about
8" of wet snow arriving over the course of 24 hours. It started
snowing during the day and was about as deep as I could handle (maybe
very wet snow) and still maintain riding speed on my way home from
work. Another 6" fell overnight. Attempting to plow in the
morning revealed a flaw in the design
of the new plow: It works too well! The wet base was now icy and
packed and the nose of the new design cuts right down to the
pavement. Even walking I could not make much progress against the
ice and heavy snow. I was the first one out in the snow that
morning but by noon dozens of walkers had been out and the trail was
getting packed down. Even the push
plow made little progress in the hard packed snow.
The next morning I reverted to the good ol' blue plow
(shown on the
previous page). The scooter wheel ahead of the blade gives it the
advantage of riding up on the hard packed snow and skimming only the
lighter loose snow off the top. The aggressive cutting feature of
the new design may still prove useful when dealing with ice or soft
Later in January we received about
8" of fairly light snow over a Friday night into Saturday
morning. I got out early Saturday and the push plow cut through
very nicely. That afternoon and into the night the winds picked
up and the snow drifted deeply in some of the open areas. Drifted
snow can be very difficult to cut through. By Sunday afternoon
there was a hard packed base, a few inches of power and then a crusty
top. The push plow could not make much progress since the snow
was as deep as the body of the plow and thus the wings were not rolling
the snow out but just jamming like a cork in a bottle.
I decided I needed a plow that would have the following features:
- Two wheels to allow me to tilt the blade to cut or skim depending on
- Shallow angle for maximum lifting force.
- 16" total lift height.
- 17" front blade tapering out to about a 32" total width.
- Short enough (4 feet) to fit in the trunk of the car.
I really liked the blue plastic roll-up toboggan that I used on the
original bike plow. I had been looking for more of those or
something similar to cover the plow and provide a slippery
surface. I was considering using the inexpensive self-stick vinyl
flooring tiles when I stumbled upon the ideal material. It is a
0.060" thick white
plastic wall covering intended for bathrooms and kitchens. It
comes in a 4' x 8' sheet for about $14 at the local building supply
Here is what I ended up building:
view. Note the handle from the Push Plow
The main frame is 2x4s with plywood in the front to hold the steel
cutting blade and on the bottom to provide a sledding action when the
unit is tilted up.
Some pine 1x10 across the rear support the pocket for the Tee
handle. 1x2s are used for the truncated tetrahedral frame.
The plastic sheeting is screwed on almost like upholstery.
Scooter wheels are used again. They are placed about 12" back
from the front so the blade touches the pavement at about a 20 degree
Initial tests show it works well. The variable blade angle is
handy for getting over the ice that would be too hard to cut otherwise.
An unusually snowy 2008 has prompted
me to do some modifications. Last year I added a vertical cutting
blade to separate clumps of wet snow and some plastic angle to help
encourage the snow to move off the sides.
Clumps of snow tended to fall under the plow so I added a
"skirt". This seems to greatly reduce the roll back and helps
form the trough shape.
The skirt pivots near the
the plow. It slides along the ground while still allowing the
tilt up and down to follow the terrain.
skirt with the plow fully down.
raised a bit. Plow
tilted way up.
In Feb. 2009 I added an extra spreading blade to roll the deep snow off
the top and also to push the sides of the trough out so the bike plow
fling the snow out.
Drift Spreader unit
With the heavy snows of 2005, I
decided actually spend some time thinking more about the optimal shape
of the plow. It seems intuitive that a sharper plow would be
easier to pull but I wanted to calculate some values, even if they were
just relative. Here are some results:
Think first of the low speed case or the action when one is using a
regular shovel. Obviously some work is involved and it is mostly
just moving the snow against the force of gravity to get it up and
out. Good old m·g·h.
The high speed case is typical of the action of the plow in thin
snow. If you believe in conservation of energy then one can determine
the work involved. Assume the plow is easy to pull and the plow surface
is frictionless (generally not the case). Assume the snow is just
resting on the pavement and not stuck (again, this is often a bad
assumption). The plow is a
shape where the nose has a half angle of theta relative to the
direction of travel.
Assume the plow does not collect any snow so
all the snow encountered must exit the plow. The exit speed, Vexit, of the snow is just tan(theta) times
the speed of the plow.
The energy of the exiting snow is
So the power required goes like tan(theta)2 and like the
cube of the
speed (as it should).
The tan(theta) assumption seems valid for snow that exits the plow in a
laminar fashion. It is apparent that even a flat plate (i.e 90º half angle) will push snow out of the
way but the mound of snow
ahead of the plate forms some natural angle of shear.
Experience shows the following assumptions are generally true:
- All the snow encountered must exit the plow.
- The snow is compressible and the collision with the plow face is
- The snow might even stick to the plow, be carried along for a bit
and then fall off.
In the simple case where the plow picks up a blob of snow and
carries it along at V, the energy of the snow is
0.5 * msnow
As the plow moves along it is constantly encountering new snow
that gets picked up, carried along and dropped off to the side.
Power = energy
the power required to pull
the plow goes like
0.5 * msnow
/ time * V2
Again, the mass of snow encountered per unit time is proportional to
the speed of the plow so the power required goes like the cube of the
speed (as it should).
One can plug in some numbers for typical snow density, plow angle, bike
speed, etc. Ballpark calculations show the power required
to pull the 45º plow 6 MPH in 6" of wet snow is about
watts. This does not include the difficulty of riding a bike in
6" of wet snow.
- These simple calculations do
not account for the adhesion of the snow to the pavement. This
seems to be a major source of drag in slushy snow.
- The friction of the steel
blade against pavement is large, especially when the plow is loaded
- Different types of snow have
different natural shearing angles. A plow that is more blunt than
the shearing angle seems to just collect a huge blob until enough snow
is available to shear.
For more detailed information about Snow
Army Cold Regions Research and Engineering Laboratory
The SNOW Interest Group at http://snow.usace.army.mil/snow_mainpage2.html
This paper has some interesting information about blade angle
performance of full sized snow plows:
An Improved Displacement Snowplow
Kynric M. Pell
The Department of Mechanical Engineering
University of Wyoming
A Sharp Plow
Any engineer likes to have
constraints on the problem. I figured the plow should be as long
as possible but not so long as to make stowing unwieldy. A
20 degree half angle makes the sides about 24"
long which is convenient
for using standard materials. It is also 24" from the bike hitch
bar to the top of the rear rack
I incorporated some of the latest materials and ideas:
1) Although plywood was handy for the structure, it is heavy and
difficult to work with. The new design uses more pine.
2) The sheet plastic used on the drift cutter is great and rigid enough
that no superstructure seems to be needed.
3) The longer plow requires a different rack holder. When stowed
for transport the plow bottom now faces the rear tire.
Sharp Plow, top left
(Click on any picture to see a larger version.)
Start by cutting a 45 degree bevel on one edge the whole length of the
The key to construction is the 2x4 in the middle. I first cut the
20 degree sides then beveled those edges 45 degrees along the cut
line. This gave me the base for attaching the 1x4 sides. I
attached one side piece and did a vertical cut for the nose. I
then removed that piece and attached the other piece and cut it.
This procedure was much simpler than trying to figure out the wacky
angles and setting the saw for the cuts.
I then added the reinforcing blocks for the rear axle. These are
beveled 2x4s. It works out nicely that the scooter wheels give
the bottom of the plow just about the right ground clearance when the
axle sits on top of a 2x4. The wheel spacing is maintained by
washers on each side of the wheel bearings and an 8" piece of 3/4" PVC
on the axle. The axle is captured in holes in the 1x4 and
retained by wood screws to plug the outside openings of the through
A 1x2 rear brace seems like a good idea.
The nose of the plow is cut to accept a 2x4. The front wheel is
supported by aluminum plates on each side of the 2x4. The hitch
bar is captured by the 5/16" axle bolt.
The 1x4 sides get a vertical cut to trim them to the 17" final
width. Then the plastic sheet is applied and then the metal
edging. I used 22" long 16 Ga. galvanized deck strapping.
Update: This plow did not have enough lateral velocity to clear
the snow far enough out of the cut. It has since been modified to
have a nose half-angle of 30°.
The sharp plow modified to have a 30° blade half angle and a 45° exit angle.
Also note that
the hitch arm has been moved up above the front wheel. This is an
attempt to put the arm more in line with the attachment point on the
bike and reduce the lifting of the nose of the plow.
It looks like a disadvantage is the plow tends to oscillate more.
I think this might be due to the high arm being more rigid than the
previous attachments and also not "steering" the front wheel of the
plow. The old blue plow tracks well and steers a bit due to the
slop in the axle bolt holes.
Modifications for 2008 include adding a box for a standard 1 gallon
plastic milk jug and reinforcing the plow so another biker can rest
their front wheel on the plow while they walk behind and use their bike
to help push.
Filling the jug with water adds enough mass to damp some of the
oscillations and also forces the front wheel down. The scooter
wheels are narrower than my knobby bike tires so the 8 lbs. gets the
plow to cut into the snow at about the right level. Cut
too deep and it is like tossing out an anchor. Don't cut deep
enough and the next bike sinks in.
front view Rear view
The Rack Holder
This just uses a piece of pine "base" molding and
two 1x2s. The thin pine is wedged between the bike bag and the
rear rack. The gap between the 1x2s captures the PVC axle tube.
The 1x2s just
fit between the plow wheels to keep the plow from sliding side to side.
stowed for transport. Note that the hitch allows the plow to
rotate so the bottom can face the bike's wheel. This is perhaps
my most notable innovation so far!
A "New" Bike and Bracket
In fall 2006 I needed to get my own bike since my daughter was taking
hers to college. I found a 1988 Trek 820 for $35.
1"x1" Aluminum angle makes a bracket for the plow hitch.
The extreme hard packed snow and ice
of 2008 have prompted me to get studded tires. The Nokia W160
(26") have quickly shown to be well worth the investment. I now
must remind myself to not panic on glaze ice. The only times I
slipped are when I stopped pedaling and tried to walk.
I have never enjoyed falling off my bike. Falling in snow doesn't
hurt too much but pavement rips my jacket, ice is dangerously hard and
slush is cold and wet.
(Studded tires cost $30-$100 each depending on the manufacturer and
model. A trip to the hospital involves at least a $75 emergency
A Better Cutting Plow
For the 2007-2008 season, I decided to revisit the dynamics of the plow
in heavy wet snow. The Drift Cutter works so well in all kinds of
snow, I wanted to see if a similar shape would work behind the
Some observations of the behavior of wet snow led me to reconsider the
shape. As mentioned above, a problem with the Sharp Plow is
oscillation, especially when clearing a bit of lumpy snow or slush in
an already well established but packed trough. The plow does not
have enough mass to force the blade to cut the snow. Rather, the
snow pushes the plow to the side until it hits the wall, then the
opposite blade bites into the snow and swings the plow back the other
A much more aggressive angle (large Theta) would cut into the snow and
slush and have less lateral force to push the plow off course. Since
wet snow does not "fling" off the plow very well in any case, I thought
it might not matter too much what the initial contact angle was.
Top view of the plow with a 70 degree attack angle.
The lifting angle is 45°. This seems to be a bit too
steep. The snow and slush tend to clump and not slide up or out
A plow with a lifting angle of about 25°
has been tested. (Photos coming soon.)
Although the more aggressive angle
of attack cuts lumps better and does not oscillate as much, the shape
of the plow does not seem to move the snow to the side very well.
Snow builds up, the metal digs in and the drag goes way up. This
shape is great for the cleanup runs but I don't like to use it if there
is any more than about an inch of new snow.
The 30° model is still
the best plow for most situations.
A Snow Grooming Unit
New in January of 2009 is the Snow Groomer.
Snow Groomer stowed.
Snow Groomer deployed.
The Snow Groomer is a simple sled with 1/4" grid galvanized
hardware wire across most of the bottom and a shaving blade near the
It was used to smooth compacted snow that was too difficult to remove
from the trail even with a shovel.
The next improvement will be to add a small Vee-plow blade near the
rear to move the newly cut powder off to the sides.
Movies of the Plow in operation
Here are a couple of short movies showing the 30° plow in action as viewed
from the rear rack of the bike.
The first one shows the plow in about 3" of medium density new
snow. The second one shows the plow transitioning from uniform
new snow to the previously plowed track. Note the slight
oscillation of the unconstrained plow.
Back to Page 1.
Created by Dave
Original: February 26, 2004
Updated: January 10, 2005, Feb. 2, 2005 with drift cutter. Feb.11, 2005
with Physics and the Sharp Plow. January 29, 2007 with modified sharp
plow and new bike. January 28, 2008 with a better cutting plow.
Feb. 19, 2008 More plow photos, comments on physics and notes about
studded tires. Feb. 26, 2009 added links to other snow technical
information, added Snow Groomer and Movies. Jan 12, 2010 added Drift
Bicycle pulling snow plow, Bike path plowing, Shoveling the bike path,
A plow behind a bike, Bike Snow Plow, Clearing snow from bike
path. Snow Plow Physics. A Sharp Plow.