Articles of Interest
The popular Two-Ten engine and its long history
written by Keith Pickersgill
The popular Two-Ten engine, known as the SOLO 210 and now the newer variant, the Hirth Aero 210, has a long, proud history.
Download 210.zip containing a detailed Exploded view diagram (GIF format) of the Two-Ten engine, with part numbers.
Some pilots have expressed a concern over whether an engine of only 210 cubic-centimeters capacity will have enough power to carry them aloft.
It is not a question of weather the 210 engine is up to it, but rather how the engine is used, the design and layout of the power pack, and VERY careful selection of propeller and reduction drive. Also, the use of a properly resonant tuned exhaust (and appropriate prop and
redrive) may almost double the available thrust, without any penalty in terms of engine reliability or durability.
We have comfortably flown our standard XPLORER as a tandem, with pilot and passenger weighing in at 170kg (370 lbs+) without any problems.
The correct wing selection is vital, as is sufficient powered paragliding flight experience when you load up this much.
The 210 and its various variations are used in over 70% of powered paragliders worldwide.
Adventure paramotors in France pioneered their usage shortly after the SOLO 210 design was changed to a Nikasil coated barrel, and it has proven itself as a formidable aviation workhorse over the years. Their very first 210 engines are still flying! Shows how reliable these engines are.
Some background info on the 210:
The design is late sixties (i.e. thirty years old!)
Over the years they included new technologies as these became
available, e.g. changed over to cast Ali alloys (with steel insert for
barrel), then hard-chromed barrel, and finally Nikasil barrel.
Also changed over to solid-state CDI ignition shortly after this was
A few cylinder-head mods were introduced as the importance of Squish
Clearance became known and improvements were developed.
Changed alloys on the conrod and on the piston.
However, the basic design and layout is still the same! This means
they still have the SAME inlet port, exhaust port, transfer ports, and
the port timing and port areas remain unchanged. Shows how far ahead
of their time they were.
In those days, there was no computers, no simulations and much less
undestanding of the finer design details, so they simply built it as
strong as they could. Nowadays engines are built to very close
tolerances, based on structural stress analysis, and computerised
forecasts on wear & tear, heat transfer, etc. Today's engines are much
more powerful and have much improved acceleration, but they simply do
NOT have the same relaibility, durability or longevity built-in.
Visualise the renowned Dakota DC3 aircraft. When it was built, they
had no idea how to calculate structural stresses in the wings, so they
simply built them as strong as their technology allowed. As it turned
out, they had overdesigned in the order of a few magnitudes. The
result was the airframe and wings far outlasted all expectations and
are still seen in regular service. Our (South African) Air Force still
has plenty DC3's being used as light transporters, though they have
seen over 10 times more airtime than intended. That's a factor of
1000% over the intended design flight service! Some are now fitted
with turbo-props and comfortably handle the increased loads and
speeds, even at their advanced age.
I tend to beleive that the 210 engine will become as legendary in
its own lifetime.
Granted, its power and torque curves leave a lot to be desired by
modern standards, but they suit our application as if purpose
designed, allowing compact reduction ratio's and perfectly suiting the
propeller diameters we need as well as perfectly suiting our low
It was originally designed for; and is still used extensively, as an
agricultural engine, expected to run for days on end. It is often
refuelled without stopping. One common usage is as a crop mister,
whereby it swings a 70cm plastic fan-blade, and atomised water is
introduced into the airstream to keep the foliage wet and cool in
arid environments or during the harsh dry season.
Many powered paragliding brands use the 210 -- Adventure, Fly, Fresh Breeze, Xplorer, Paramotor (that's a brand name, as well as being used generically), La Mouette, and probably others that I can't think of right now.
And now we are seeing the emergence of improved versions. The 210 is basically an agricultural engine as mentioned above, where it often runs for days at a constant RPM.
In aviation, and with dynamic throttle control, the engine is
expected to frequently accelerate and decelerate according to flight
needs. Furthermore, everyone wants a little extra power for safer
takeoffs, bigger pilots, tandem, utility vehicle, higher altitudes,
Many of the more powerful paramotors, such as our Xplorer, use
expansion-chamber style, tuned-exhaust systems which are resonant and effectively
"super-charge" the engine for increased hp, torque, or both. This
places additional strain on the crankshaft and conrod.
Hirth Ultralight Aviation Engines now has a Hirth Aero 210 variant with an
improved crankshaft and conrod, using special alloys.
Furthermore, the Tillotson carb (and Walbro), as often used, was designed for chainsaws and the like, i.e. good idle, good top-end, but very little inbetween. Now we are seeing much
better carbs in usage. Some are using slide-type carbs, such as the
Bing carbs seen on BMW motorcycles, and more recently, better diapragm
carbs with low, mid and high circuits, and often with a choke for
The ignition system is also being improved, with increased Wattage,
lower RPM minimum firing, improved timing arrangement, etc.
This ongoing development by so many different companies indicates the
faith the market still has for the trusty old 210 motor.
However, it must be said that simply using a 210 engine is not in
itself enough to make a good paramotor. Much modifications and
enhancements are required, plus very careful design and selection of
reduction drive and propeller combination, and an amazing amount of
R&D in the framework and mountings to minimise propeller induced
forces (Prop torque effect, Gyro precession, and ABT), as well as maximising frame strength while minimising overall weight.
Address comment to Keith Pickersgill at firstname.lastname@example.org