This is the python clone
built by the friend of mine, that got me going on my own version. This
is a rough progress report and brief explanation of how he built it.
This is a shot of the bent just
after its first test ride, which was a complete success. As
mine was ready to test ride a little earlier than his, he quickly
learned how to ride mine. When his was ready, he got on
it and rode off. Worked like a charm. The seat is
the same one that was on mine (complete with seat fabric repairs
:)) as I decided to give it to him because it felt a little too
short in the mid-back section for me. I'll build a new one
that is slightly longer and should fit me better. As it
sits in the picture, it weighs 27lbs. It's missing front
brakes, gear shifters, brake levers, small handle bars of some
type (undecided as of yet) and most likely fenders. We were
discussing some form of either fibreglass or CF front guard/fender.
Water bottle mount(s) and some form of saddle bags/tailbox
would also likely be added.
It's a little shorter and definitely
lighter than mine, and he said his was a little easier and smoother
to ride. It might be due to the slightly different ergonomics,
due to the fact he isn't stretching as much to ride this one,
or maybe just owner pride :) Either way, it's rideable, and that's
The front end is made out of
essentially the same material as mine. 2" x ½"
x .064" steel box tube with a scavenged MTB BB, and an old
kid's bike BB for the pivot. His front section is a bit
"cleaner" because he has fewer sections and he angled
the front half of the chain stays down a few degrees to keep his
BB lower. It's also a little shorter than mine as he wanted
to keep the front end as short as possible because his inseam
isn't as long as mine. He also wanted to keep it as short
as possible without causing too many chain-line issues and he
succeeded except for not being able to be on the big ring on the
front and big cog on the back at the same time. Minor, as
he rarely rides in those ranges on the road, and he is more than
experienced enough to manage that small problem with proper gear
selection. Even with all his efforts, he was still fairly
tight on the inseam length and had wheel size, crank length and
front derailleur/tire clearance issues to juggle. In the
end, he went with an E-type front derailleur that mounts on his
BB instead of the derailleur post, so he could cut the post down
very low, and that solved one issue. With the E-type derailleurs,
you are limited to about 42 teeth on the big ring, but the 152mm
cranks he's going to use are 24/34/42 so that solves both his
crank length and chainring size issues in one shot. That
also gives him an extra inch of inseam clearance by changing to
the 152's instead of the 175's which are on it now, so that means
he doesn't need to switch to a 24" front wheel.
The front derailleur cable runs
down just behind the BB shell, in between the chain stays, and
will route along the bottom left and run back to the handle bars.
He has a 9 spd direct mount XT derailleur mounted on the
bottom of the chainstays, with the drop outs on top and a SRAM
9spd 11-34 cassette. His reason for a top mount was to keep
the chainstays, and in turn, the BB, low. He is undecided
on where he wants to mount the front brake yet and claims "brakes
are only for people who are afraid of vicious wipe-outs".
He's an animal :)
I think the pivot deserves a
little explanation as it is a unique application of a BB. Certainly
one I would never have considered or attempted. First, he
used a complete BB and shell off of a kids bike that had a one
piece crank. After cutting all the tubes off the BB shell,
he then cut the crank arms off and left stubs sticking out.
He started by welding the crank
(#1) into a hole in a piece of 3/16" mild steel (#2)
that is about 1¼" wide x 2" long. Then,
he welded steel flat stock (#2) to the top of a piece of
1" CroMo bike tube (#3) and drilled a 3/8" hole
in the top of the plate that was in line with the center of the
CroMo tube. The CroMo tube is welded at a 70 degree angle
to another piece of 1" bike tube that forms the backbone
of the frame and runs back to the rear wheel. Another identical
piece of steel flatstock (#4) has a ~3/4" hole drilled
near one end for the other end of the BB to go through, and the
plate has a 3/8" hole drilled near the other end that lines
up with the center of the bike tube (#3) and the hole in
the top plate. There is a small section of bike tube welded
to the top of the lower plate (#4) that slides up inside
the 70 degree angle bike tube (#3) that acts as a stiffener
and guide and stops the bottom plate from moving. Once the
bottom plate is slide into the end of the angled pipe, and over
the end of the BB, the BB nut secures one end of the plate, and
a long 3/8" bolt squeezes the other end together, and makes
a very rigid pivot assembly riding on ball bearings. He
added a gusset on the bottom rear of the pivot assembly to help
strengthen the joint. In the end, the complete front end
can be removed by undoing the BB nut on the bottom, and the 3/8"
nut on the bottom, the bottom plate slides down and off, and you
can remove the front.
The seat mount is simple 1"
x 1/8" steel tabs and has no adjustment as it was built only
rear end consists of a standard salvaged CroMo 26" MTB fork
welded into the end of some more 1" CroMo bike tube. The
angle of the main backbone is about 16 degrees which leaves the
main section running parallel to the ground, about 3½"
off the deck. The rear seat mount is the same type of 1"
x 1/8" steel tabs that were used on the front, and the seat
post length will be finalized when the seat angle range is decided
upon. While the main frame might look pretty light, he is
a light rider at around the 160 lb range, and while riding it, there
is very little to no flex in the frame, and no twist at the rear
wheel at all. He's smooth on the pedals, so I think he'll
probably be ok with the frame. He's also planning to add another
gusset, I think, where the frame has the 16 degree angle bend to
stiffen up the welded joint, just in case. The rear fork has
cantilever brakes on it right now, but it will take V-brakes as
well. Tabs might be added at a couple frame locations towards
the rear to mount the saddle bags/rear rack/tail fairing.
| It's rideable the
way it is and I'm not sure what part he's working on next, but he'll
be getting the 24/34/42 chainrings with the 152mm cranks shortly
and likely working on where he wants to put the handle bars.
| He mounted mountain bike bar
ends directly onto the end of his seat to put the brakes and friction
shifters within easy reach. He made himself a small fiberglass
fender to protect his legs, and bolted an old plastic fender to
the top of his fiberglass one, and ran it all the way forward. This
shows the slight downward angle of the chain stays which he laid
out on a wood jig that he made.
| Left side view of his python.
Very clean and minimalist, built out of mainly recycled CroMo
bike tubing and spray painted silver. He uses an old backpack
that fits perfectly and slings underneath his seat. He still
needs a rear fender though.
| A couple pictures of both the
pythons together. Marcel's is a little longer wheelbase than
mine now, but his still handles a little nicer for some reason.
His also accomodates a shorter rider than mine does.
14 Jan 06
We took an old skate blade and
made a T-mount that slides into the dropouts, with a stabilizing
tube going forward and bolting to the rear brake mount hole. The
main down tube is made of 1" box, with a hollow axle welded
to the top of it and a skewer going through it to mount to the
drop outs. The tube running forward to secure the assembly to
the brake mount is 3/4" box tube with a small piece of angle
iron on the end. We switched out the 26" wheel and
put in a 24" with screws because Marcel was concerned there
wouldn't be frame clearance. We took the opportunity to
lower the frame a little so total ground clearance in "ice
mode" is about 1.5". The skate blade pivots up
and down so it can compensate for any ice irregularity. With
a 7/16" wrench you can switch between the ice adapter and
the standard 26" rear wheel in about 2 minutes.
On initial testing, the python
is rideable but there needs to be more screws in the front tire
for better power transfer and higher speed cornering. Also,
we're not sure if a normal grind on the skate blade will bite
the ice enough, or whether a sharper 45 or 60 degree point is
required. We'll also make a small adapter to temporarily
mount a front rim brake. We'll do some mods and see what
the results are.
6 Feb 06
I took some final pictures of
Marcel's ice python after the ice races on Feb 5th. Here's
a list of the mods that converted it to an ice racer . . .
- 24" front wheel and a 1½" tire was swapped
in so there would be frame clearance when the tire had screws
- we welded up a 7075 aluminum fender as the tire was NASTY
with the original small fibreglass fender and would grab pant
legs and thigh skin and tear both out with great ease
- dual front rim brakes were installed in accordance to the
ice racing regulations. One at the front of the wheel
behind the BB on the underside of the chainstays, and one at
the rear in front of the pivot, on top of the chainstays.
- front derailleur and shifter were removed to save a little
weight as he wouldn't get going fast enough to need to change
the chainring gearing anyway
- a skate blade mount was built that bolted to the rear brake
caliper mount in the forks, and slipped into the dropouts with
a quick release. Marcel could get up enough speed that
the blade holder frame would hit the ground while cornering
hard with a normal skate blade, so we made a new blade out of
steel that was 1" taller than a regular skate blade, and
a couple inches shorter. It also had a fairly aggressive
~60 degree point ground on the blade edge vs the standard skate
- lastly, Marcel drilled eighteen 1½" and 1¼"
holes in both chainstays to further lighten the python. I
think it looked pretty cool, but more importantly, I was very
interested in seeing what effect the holes had on the chainstay
stiffness. After riding it, he said he noticed no difference,
but he's a fair bit lighter rider than I am. I think I'll
drill the holes in mine too just to see what happens. As
pictured, with about 200 screws and washers in the tire, the
python weighs just under 30 lbs, or about 13.6 kg.
So, how well did it work? Well,
as you can see in the picture, he appears to be zipping along
fairly well as he's setting himself up to go into the corner.
In fact he went extremely well, and generally faster than
most of the three wheelers there. Traction on the front
wheel was great and the only problem he had was not being able
to get enough bite with his rear blade, even though it had a pretty
wicked edge ground on it, and polished with a whet stone. In
the 2 man pursuit races, he got so much speed in his first heat,
that the rear end slid out on a corner unfortunately, and he went
down. In the slaloms, his masterful riding control enabled
him to whip the python around the cones by sliding out the rear
end slightly, and he beat all but the fastest two or three trikes.
In the 10 minute criterium race, he was cruising around,
and lapping other riders, and well on his way to a podium finish
when one of his tire screws somehow managed to cause a flat and
he momentarily lost control and hit the boards pretty hard. He
got right up and back on, and finished out the race on a flat
for the last few minutes and still managed a 4th overall (I think).
Overall, it was an amazing effort for such an extreme bent
and the biggest part of the success was due to Marcel's riding
As for the traction issues on
the rear end, I think that was due to two reasons. I think
the largest part of the problem is how the python turns. On
a normal bike, the rear wheel gets pulled through the corner and
follows a line inside the front wheel's track, and has a fair
bit of weight on it - likely close to 50%. The python rear
end doesn't follow, but rather it "turns" through the
corner on its own path and as a result, I don't think it puts
down nearly the same force as a normally steered bike does. I
know that Marcel and I could easily slide the rear wheel out on
dry pavement by turning hard and at speed. Now take that
same force, and try to turn hard with a blade on ice that can
chip away under heavy loading, and I think that is part of why
the python rear end was weak at fast cornering. Add to that,
the fact that as the ice got chewed up from the racing, the blade
was tracking across rough ice on the corners and further minimizing
its traction every time it encounterd crossing multiple ice grooves,
and it lost even more traction. Even though the rear end
would start sliding, Marcel quickly mastered the art of letting
the rear end do a power slide, while he kept the power on and
deftly used his left hand as an outrigger on the hard turns. It
was amazing to watch him rip up the corners right on the edge
of disaster, lap after lap, after lap :)
Anyway, the ice python did an
excellent job at the ice races, and I think it would definitely
be tough to beat on larger tracks with larger radius corners.
In the mean time, it'll get converted back to a "normal"
python, and he was talking about possibly selling it.
11 Apr 2006
A couple weeks ago, Marcel decided
to do a few final mods to his python after the ice racing was
done. The old modified BB that was used for the pivot was
cut off. In it's place, a bicycle fork had the legs cut
off, the steerer tube shortened, and it was flipped upside down.
The rear frame of the python was welded onto the large section
of the steerer tube where the fork legs used to be mounted. Aluminum
race adapters were made to reduce the size of the old pivot shell,
down so the bearing cups would fit tight. The steer tube
nuts are mounted upside down, and screwed up from the bottom.
The rear frame was flipped over and a 16" wheel with
a 110 psi Maxxis was installed. With the old pivot being
cut off and a 16" wheel being installed, both the wheelbase
and the length are smaller now. The 7075 fender was modified
slightly and a 26" disc wheel was mounted with a 1"
high pressure tire. We fabricated a disc caliper mount and
routed the cabling through the frame lightening holes back to
the seat. The seat angle was changed and leaned back a little
bit more than it was as well. A handle bar stem was shoved
down inside the steerer tube, and the front of the seat mounts
to the pinch section where the handle bars would normally go.
The front of the seat is now adjustable fore and aft, and
up and down so the seat angle can be changed in conjunction with
shortening the rear seat support as well. New specs are
26 July 2006
A fair amount of time has passed
by, and Marcel has done the final, final mods on his python .
. . we think. A few tweaks here and there and he slotted
his fender (to be like me, I think :)) for both the weight saving
and to reduce the "sail" effect from strong side winds.
He rides it up to 50 km a day on his commute to and from
work. I think it's a great looking bent because it is so
"clean" and minimal. A few shots from different
The specs are the following:
||26½" to top of fender
||25" to top of seat/wheel
||13" - handlebars will be added later
||2" under pivot nuts
|| 27 lbs so far . . .
||26 lbs (11.8 kg)
||26" AL, VRB-182 26 x 1.25 tire, 9 spd
||26" AL, VRB-182 26 x 1.25 tire, 9 spd
||26" AL, VRB-182 26 x 1.25 tire
||16" steel, Maxxis Hookworm 16" x 1.95"
|| ~18.4" - 99.27" with the 24/34/42 chainrings
||39" - 99.27" with the 42/34 chainrings