ptwizz

When forward launching, I find it is easy to spend too long checking the wing before starting the run.

As soon as the wing gets overhead and I can feel both risers are pointing upwards, a quick glance up is all it takes to check that the wing is wing shaped and the run begins.

My technique is to run with full commitment immediately. It's only my forward speed that is keeping the wing flying.

So long as you have learnt to feel where the wing is through the risers and don't need to look up again, there's no point in trotting along at anything less than launch speed.

It is this style of quick acceleration that gets me into the air in a few paces in nil wind. I suspect it may have also led to one or two hoppy launches, as the wing tends to hang back, only to pitch forward when I leave the ground.

More piston machining.

The sides of the slipper skirt are milled, leaving 2.0mm wall thickness at the webs, 3.0mm around the gudgeon pin bosses.

The piston is then supported between a centre and a fixture which ensures true running, for the crown and grooves to be machined.

Congratulations Simon.

I trust you've held on to your bike?

Progress has been inhibited by other stuff recently, but not halted completely.

After some investigation I've found the right material for billet machined pistons (it's Aluminium 2618A-T6511 if anyone's interested).

The first piston is turned to slightly oversize, cross bored for the gudgeon pin and then the inside machined.

The first is a test piston. To verify my design, I will make this one with an O ring groove in place of the top compression ring. This will be fitted to a simple test rig (a dummy cylinder with one end capped) and hydraulically pressurised to the predicted peak cylinder pressure (50 Bar) while the piston is prevented from moving by a support at the centre of the gudgeon pin.

I will then measure elastic distortion of the skirt areas and the pin to establish whether I need to alter the design.

Sorry people. If I had less backlog of workshop stuff I would have come.

Hope you all have a good weekend.

The forecast is suggesting I might make better use of the weekend in my workshop:

I see Friday being thermic and uncomfortable for a low hours pilot such as myself.

Saturday and Sunday wet.

I'll pass.

Are the radios OK in the air with the engine off?

I've always said buy cheap buy twice..

Does that apply equally to reserve parachutes?

Hope all goes well and you recover soon and fully.

Part of my training was aborted launches.

This involved powering up and running, then shutting down and bringing the wing to the ground under control.

This was done without leaving the ground and I have to say the practise was useful as I have had to abort a launch on more than one occasion.

I'd rather not find out what happens when I power down at running speed when the wind is pulling me towards a fence, ditch etc.

For the abort excercise, I was told that if I left the ground I should fly the circuit and land normally.

I think it is quite reasonable that unqualified pilots can fly uncertified aircraft 500ft from people, property etc.

Motorised road vehicles are subject to operator licensing, mechanical certification and regular testing, compulsary insurance and near Orwellian policing.

Would anyone really be happy to have all that applied to paramotoring? Even if it was, would there be any prospect of relaxing the 500ft rule?

Keep this in perspective and don't defend those who threaten our freedoms by abusing them.

Legislators have a habit of hitting that which is abused, rather than hitting the abusers.

I had a look at the 'Supa Tuna' page....

The kit appears to be an O2 sensor. There is no reason why it would be any different to any other O2 sensor kit, so hardly a new innovation.

Tuning a paramotor engine is probably easier than most other engines, because it is under full load and our low flying speed makes little difference to the load/rpm when in flight.

The trick is not so much in knowing that the mixture is wrong, as in knowing why it is wrong.

In a 2 stroke, this could be air filter, induction plenum volume, induction tract length, reed valve restriction, transfer porting, leaks, exhaust porting, exhaust back pressure, exhaust tuned length and probably a few other factors.

If one was intent on adding an O2 sensor system to one's engine, why not close the loop and replace the carb with an injector?

Could you elaborate upon the technical term "f***ed", so that others may benefit from your experience?

Pat,

I feel we could usefully teach each other launch techniques.

I have still yet to make a single reverse launch with the motor. I always fly in light to nil wind and have barely had any problems getting the wing up and under control and getting moving.

That limp windsock says "fly now" to me.

I should probably be pushing my operating envelope to include a bit more wind speed, but first I need to get some reverse launches under my belt.

I note that all Simons 'smilie' animations show failed forward launches, none show a failed reverse launch

The fact that the mount works is testament to the design. I just cut off the bits of nylon that didn't look like your drawing.

Looking good!

Is the fast landing (or perhaps lack of brake authority) a feature of full reflex wings?

I am 125kg total on a 29.5m² wing. In nil wind, a smooth progressive flair results in a near stationary landing every time. My brake lines are well bowed in flight (see pic) and require a lot of input to generate any kind of turn rate.

Hi Pat,

My old, high hang point Bailey torque steers to the right, despite being at the limit of asymmetric adjustment on the hang points. This is something i've learned to not only live with, but use to my advantage.

I have a left hand throttle and I can fly using my left hand only with a bit of left brake to counter the torque steer. Left turns are made with more left brake, right with less.

This leaves my right hand free for camera, map, rolling fags etc.

Occasionaly, if my left arm becomes tired, I will park the brake and use asymmetric trim to counter the torque steer.

These are my own practises, not recommendations for others to follow.

Not sure you would want to do it in quite the same way as I did though lol (fill it with petrol and let it burn, tap it all out as it cools) but as I say, I would expect this is not the way it's actually done. LOL

SW

That is exactly the way it's actually done in my workshop, but to some extent this may be a reflection of my contempt for 2 strokes

If anything black were coming from the crankcase gasket of a 2 stroke, something would be very wrong.

A leak in the crankcase (gasket or crankshaft seals) will lead to poor running at idle as it sucks in air.

The spatter marks indicate a leak at the exhaust flange.

Have you checked that the exhaust is not clogged with carbon deposits? This would cause poor running at high rpm and leakage due to excess back pressure.

PatPux posted a useful guide to drive belts a while ago.

viewtopic.php?f=5&t=9330&p=67070#p67070

I have now found a local launch site, with a very friendly club, the Priory Farm Aviators. They mostly fly microlights from a strip 4 miles from my house.

I flew from their strip yesterday. It took me three attempts to get away, due to a narrow strip with light wind swinging through 180° every few minutes.

First attempt: With the light wind at 45° to strip, I set up and waited for wind to drop. In virtually nil wind, I set off, only to have a gust come in , forcing me to turn into the wind and run out of space before I could launch.

Second attempt: Wind still light at 45° to the strip, I set up facing the wind and waited for a breeze to come through. I set off again, this time the breeze dropped to zero and I ran out of ground again.

Reverting to the nil wind approach, I got away at the third attempt.

The flight was relatively uneventful. I had waited until early evening as RASPS was showing over 400fpm during the afternoon. By 7pm there was still plenty of lift about, but reasonably smooth.

I spent 40 minutes or so just surveying the local landmarks so I could find my way back. Plus a few minutes skirting the edge of Old Buck ATZ to get as close to my house as I can.

Most of the microlight types had not seen a paramotor close up before, so I was the focus of some interest. My failed launches were made in front of several cameras.

With a site closer to home, I am looking forward to many more summer evening flights.

Probably old fuel has left deposits which have blocked the jets in te carburettor.

You might get away with using carburettor cleaner without dismantling the carb.

Pete.

Not convinced this is real.

Freeze at 4:43 and it appears that the blades are simply bolted to a piece of timber with no means to drive them.

Also, try dangling anything with spinning discs attached and you'll soon find how powerful gyroscopic forces are.

There are ground based machines for this job - bigger versions of the tractor attachments used for trimming hedges. They would not take weeks to cover a few miles.

I'm guessing this is blown out again, not that I could make it this weekend anyway.

Here's to next weekend.

6kg of crankshaft assembly. Convincingly chunky.

Next - pistons. I've only made one piston for an internal combustion engine before - and that was a copy of an existing part.

For this engine, I have rejected the original four ring pistons which go with the Dnepr heads - mainly because the valve pockets are in the wrong orientation.

I have designed a slipper piston with oil control more suited to a radial, in which the pistons have to work in all orientations.