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Twin Turbo
Jet Cycle
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Preliminary 3D mock-ups of the JetCycle. I originally intended to
put my jet engine into an ordinary bicycle for lightness, but when
searching the net I came across the sport of Mini Moto racing ( 50cc
mini race replicas and dirt bikes ) and consequently a whole source of
small, cheap lightweight cycle parts! |
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Twin Turbo
Jet Cycle 2
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Improved versions of the JetCycle model including
chain, sprocket and freepower. Work still in progress. |
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Mini Moto Dirt Bike
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Examples of Mini Moto's. Jet Cycle front end based on the Mini Moto dirt bike
frame and forks using wheel from the race version. |
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Frame and Forks
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Mini Moto dirt bike frame. Frame and forks came as a
package, bought through Ebay. The frame may or may not be usable
depending on how the design of the rest of the bike pans out. |
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Forks
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Mini Moto dirt bike front forks. The forks from the
race versions don't have any suspension. These
units will come in handy! |
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Front Wheel
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Mini Moto front wheel and race slick. This wheel
does not normally fit the dirt bike forks, so they are a bit of a
squeeze, but looks cooler than the larger skinnier dirt bike front
wheel! ;o) |
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Yamaha TRX 850
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The donor bike for the rear end of the Jet Cycle.
The rear wheel, swingarm and rear brake caliper had to be from the
same bike to ensure that I could fit the parts together without
modification. |
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Rear Wheel
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Yamaha TRX 850 rear wheel. I wanted something with a
wide rim and tyre and just happened across this on Ebay. Fits the bill
nicely! |
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Swingarm
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Yamaha TRX 850 aluminium swingarm. Ebay again! |
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Rear Brake Caliper
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TRX 850 rear brake caliper, cheap and in good
condition from Ebay |
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Rear Brake Cylinder
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Rear master brake cylinder from a Suzuki GSXR1000 in
excellent condition from Ebay. It didn't really matter which cylinder
I used as long as it was from a bike of similar size. |
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Mono-Shock
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Rear shock from a Suzuki SV650. I had difficulty
obtaining a shock from a TRX850 so decided to go with this one which
fits perfectly. Again, bought cheaply through Ebay in very good
condition. |
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Jet Cycle
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Rough layout of the Jet Cycle. The finished oil/fuel
system can be seen on the ground to the left. This will eventually be
mounted above the shock between the rear wheel and fuel tank. |
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Rear Suspension
Suspension Animation
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The shock absorber can be seen poking through the swingarm
ready to be mounted. The bottom of the shock will be attached to the
rising linkage which will be pivoted to the tank. The shock top mount
will be similarly pivoted to the top of the tank The 3D images show
how it will eventually connect together. Click on the above link for
an animation showing the suspension in operation. |
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Rear Brake Unit
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I made the mounting brackets for the rear brake
cylinder from 3mm steel sheet. It will eventually be cable operated
via a lever on the handlebars. The cylinder and oil reservoir is
mounted as a single unit in a neat package. There were ready made 6mm
holes tapped in the top of the swingarm so this determined the
original mounting position.
This unit will now be changed to the other
side of the swingarm for reasons as explained below. |
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Sprocket
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91 tooth kart sprocket, chain and pinion, ratio
about 10:1 providing gearing for about 70mph. Sprocket mounted on
original cush drive. I needed to use kart sprockets to achieve the
desired reduction. Wide choice of sprocket ratios available so easy to
change gearing.
The wheel has been reversed for freepower use so
that the sprocket is on the correct side side to allow the freepower
to drive the wheel in the right direction. |
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Brake
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Rear brake also swapped over resulting in a top
mounting arrangement which I think looks better! ;o) Luckily the
original chain guard mounting lugs on the swingarm line up well with
the caliper 'stay' which I will use for securing. The brake
cylinder will also be re-mounted on this side. |
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Levers
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A couple of bicycle brake levers found in a
scrapyard for a pound! ;o) |
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Fuel Tank
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Fuel tank made from a large butane cylinder ( found
dumped near my house, lucky! ). The
tank will form the centre of the bike which is strong enough to act as
a stressed member from which all parts will be attached, so no need
for a frame. There should be enough capacity for at least 5.5 gallons
of Diesel. Swingarm mounting brackets made from 8mm steel plate
needing to be welded to the tank. The seat will be mounted on top of
the tank. |
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Fuel Tank 2
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Swinarm brackets welded on and also
the 3 mounting brackets for bolting the front end frame onto. Having everything
bolted to the tank means that the whole machine can be disassembled
into 3 main parts for easy transport in the boot of a car. |
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Fuel Filler Cap
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I wanted a low profile aircraft style filler cap so
that the seat can be mounted on top. I
found one on ebay.. |
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Jet Cycle 2
 
 
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Finally got round to making some stands and start to
position things a bit better. The stand for the rear wheel was made from the
forks from a bicycle with some paddock stand 'hooks' welded on. The
rear brake caliper is now in position, with the 'stay' ( which had to
be shortened ) fixed to a bar that bridges the original chain guard
mounting points. Hopefully this arrangement will be strong enough to
withstand the pressure..! ;o) Here the fuel tank has been elevated using a couple
of axle stands and provides the perfect height in relation to the rear
wheel so that the angle of the swingarm is correct ( at least as far
as I can make a judgement at this point in the proceedings..! ) |
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Rear Suspension
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After much agonising about the position that the swingarm
should be, taking into account the potential swingarm travel,
spring movement, etc, I finally made up some patterns out of thick
paper to allow me to best determine the shape of the brackets. These
will be made from the same 8mm steel plate that the swingarm mounting
brackets are made from. |
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Top and bottom brackets finally made and chamfered
ready to be welded to the tank ( I hate making these things, they are
always a chore and take forever with just a hacksaw and a file.. Oh,
for a plasma cutter..! ) |
 
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OK, first stage of welding. Top brackets were a bu**er
to get lined up and tacked into place. Had to weld temporary
triangular pieces across brackets to stiffen things up while
tack welding. After the third go it came good and I was able to weld
the pieces proper. This involved alternating the welding from one side
to the other in 1/3 lengths to stop the whole from getting out
of true. Will still need some minor tweaking using a couple of blow
torches, and some hammering from the inside of the tank. I always aim
for maximum of 0.25mm out.. |
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Chain Tensioner
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Originally I was to mount the engine and freepower
unit on the swingarm. After careful consideration I decided to mount
the engine and freepower unit on the frame itself, the swingarm moving
independently of the frame/engine/freepower. This created another
problem in that the chain final drive had to have some mechanism to
take up the slack as the distance from the rear sprocket and freepower
drive sprocket would be constantly changing. I was going to make up my
own chain tensioner but hit upon the idea of using a bicycle rear
derailleur. I removed the original sprockets and replaced them with
modified Rotax kart engine sprockets which are practically the same size and
running on ball races. The bearings were a fraction of a millimeter
smaller than the inner diameter of the sprockets so a bit of Loctite
638 retaining compound was used. Job done..! ;o) |
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Frame Material
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Here are some sample 180 degree pipe bends
obtainable through ebay. I will be chopping them up and using them to
build my own rear frame from scratch. |
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