ptwizz

Apologies in advance if I'm pointing out the bleedin' obvious:

A possible concern would be the oscillating loads on the gearbox at low rpm.

The propeller is a large flywheel. The engine makes all its power during the combustion cycle, and accelerates the crank for that part of its rotation. During the rest of the rotation, the crank slows. Thus the engine exhibits 'torsional vibration'. This is most noticeable at low RPM.

A centrifuge clutch provides torque transmission proportional to rpm, so it can disengage or slip at low rpm (when the engine rotation contains significant torsional vibration) and prevent the load reversals which would be seen at the gearbox in a rigid drive setup.

A torsional shock absorber between the crankshaft and the gearbox would reduce the effect.

At the limit of the machines capacity, the holes for the pushrod tubes are bored into the tappet ring. Each hole is counterbored to house an O ring seal at the base of the pushrod tube and similar features will be machined into the cylinder heads. Anyone with experience of Meriden Triumph engines will understand!

Each of the 7 lugs on the inside of the ring supports a pair of the swinging tappets, whose forked ends overlap. Inlet and exhaust tappets are identical, it is the design of the tappet and the offset created by the overlapped ends which places each tappet in line with the appropriate cam.

14 billets of 2014 Aluminium, followed by a series of operations in decidedly Heath Robinson set-ups on the mill.

Result: 14 swinging tappets. Each will a needle roller cam follower fitted.

If you have a 4 stroke motor, you may find that the engine and prop noise is preferable to the wind noise.

Android?

Or is it still only for worshipers at the church of Apple?

The difficult starting with loose belt combined with the warning about running without prop would suggest that the prop is the majority of the engine's flywheel.

When starting, energy is stored in the flywheel and helps to get the engine over compression, smoothing the force on the pull cord.

Running without adequate flywheel means the crankshaft will accelerate hard during the power stroke and slow a lot during compression. This can cause excessive vibration not only of the engine as a whole, but within the crank assembly where it can cause the crankpin to move, resulting in a twisted crank. That is a bad thing.

I mis-spent too much of my youth fixing other people's 2 stroke bike engines (mainly RD's).

The Spaminator?

.... fun epics? (the engine spluttering as the tank dried, just as the landing site came into view after a tantalizing few mins of 'will I won't i')

I would categorise that scenario as poor planning, not fun epic.

I believe some have flown with basic camping gear, but you will be limited by your ability to launch with the extra weight and bulk.

With a front mounted reserve and a small 'flight deck', I find that low or nil wind launches are quite an effort.

Remember that you will be running, responding to the movements of your wing, dealing with torque and gyroscopic reactions from your motor and carrying its weight.

Add a small tent and a sleeping bag and you have a lot of stuff getting in the way of these processes.

With more wind, you can reduce the running, but you'll have more weight and bulk to manage when turning.

In short, I would say that realistically, your luggage capacity is similar to that of a unicyclist who can't carry a rucksack.

Tasteful of course, but make sure not to cover the most intimate parts of the paramotor.

T shirt request:

Paramotor Girls.

Not sure what this is intended to be. Too heavy to attach a wing and fly, and I can't see a prop driven vehicle being tolerated on the road.

Do you think the girl was told to balance on it that way, or perhaps she just has no idea how a seat works?

Back to metal hacking. The largest chunk of aluminium so far at 10-1/4" diameter and 2" thick will become a ring which is located around the cam and supports the tappets.

I've had a short break from carving large lumps of aluminium and steel. I've spent a while carving small lumps of balsa wood, resulting in this. Thanks to Nielzy.

As Simon pointed out, the 500ft rule has a specific exemption for take-off and landing, so someone hiding behind the hedge doesn't change the legal position.

In any event, whatever the letter of the law, it is the responsibility of each pilot to ensure that reasonable precautions are taken so as to avoid disturbance to the public. This is how we avoid negative press and remain largely self-regulating.

While flying from this year's PMC fly-in, I noticed traffic slowing on the A149 to watch, although I and the other pilots near the road were at 1000 to 1500ft. The same happens around the military bases scattered around Norfolk. There are some drivers who will gawp at anything and we can't be expected to fly only in remote areas to prevent them from doing so.

I have considered launching from Old Buckenham common (i.e. my doorstep). The main reason why I haven't done so is that the B1077 trunk road passes along one side of the green and I would consider the potential for distracting drivers to be unacceptable.

In these situations, I try to imagine how an incident would be reported by the gutter press:

"Beardy Bin Laden lookalike attempts genocide using paramotor to disrupt traffic"

I would have thought this would be the perfect opportunity to show off a closed loop injection system.

Quote from 'Propellorhead':

"Most aircraft fly not because of the pilots inputs, but despite them"

Timing gears. The gears were purchased as blanks (i.e. chunk of steel bar with gear teeth) then turned, drilled and bored. Lots of visual result for relatively little work.

Machining the crest radii on the cam profiles and finally boring out the surplus material left in for fixturing.

On the wall next to my mill is a sheet of paper with a long list of angles and offsets required to generate the relatively simple cam profiles.

I am amazed that I managed to do all of it without a single phuquup! I had planned in some detail how I could recover the part in the almost inevitable event of a major machining error.

Next: timing gears. A relatively simple compound planetary arrangement. For complex timing gears, look up the Bristol Centaurus - described as a 2500 horsepower Swiss watch!

It may not be written into revised air law, but common sense and good airmanship say we should fly at sufficient altitude to be able to glide clear.

This is not a good time to be perceived as creating a risk to members of the public.

Unfortunately the power / weight ratio won't be adequate for flying anything modern.

At a projected 100BHP output and 120Kg dry weight, it would just about drag a small WW1 biplane into the air.

I wouldn't be confident that it wouldn't shit out at 50ft.

One of the more challenging parts to manufacture is the cam ring.

The first picture shows the blank being turned. This a an 8kg billet of EN8 steel which will be a 1.5kg part when finished.

The second picture shows the first stage of machining the cam profiles. In this operation, the base circle is being created. I have left the inside diameter of the blank smaller than finished size so that I could drill some small holes at the centres of the various radii which form the cam profile.

The cam profile is based on the timings of the Dnepr cam (from the same engine as the heads). I have modified the profile to take advantage of the large radius cam ring and generate near constant acceleration valve motion. This reduces stress on the valve train components and permits the use of softer valve springs.

The followers will be roller type, eliminating the need to harden the cam ring beyond the properties of the EN8 material.

Never underestimate the awesome power of the shed bodger.

BODGE - Bit Of Damn Good Engineering.

Historical note - a bodger was a skilled woodturner who would fabricate a pole lathe at the site where wood was being cut and turn semi-finished parts. This process reduced the quantity of would which had to be transported back to the carpenters and left the waste in the woods where it would naturally be recycled.

Gaggle tracks flights without using a data connection.

Most 'smart' phones have GPS. Mine is a Samsung Galaxy Ace (£100 or less) and I run Gaggle and Aircub on it.

Many, many other phones with similar capabilities are available.

Might I suggest that your original choice of wing was correct and should be another incentive to lose the excess weight?

I started flying in my late 40s. At about the same time, I started putting on weight (having been a constant 75kg for the previous 25 years or so).

I set myself a limit of 80kg and have manged to stay under that weight, using my wing loading as a mental target.

I don't do 'fitness' or dieting as such. If my weight starts creeping up, or if I feel unfit I will make a few simple changes, like taking the dog for a walk instead of eating lunch for a couple of days.