old man emu

18 minutes ago, jackc said:

The maintenance of 24 reg aircraft relies on factory certified parts, thanks to Australia’s regulators rulings.  

There appears to be several car engines available that have been set up for operation in aircraft. OEM spare parts for them are available from the car people. How does that work under the Regs?

27 minutes ago, turboplanner said:

OK you two experts, what are your thoughts on Double Road trains on the narrow lane freeways of our cities, and distributing coupled into our industrial streets, given the converter dollies?

 

I feel sorry for the poor drivers of those juggernauts who have to get them through tight roundabouts while dealing with the impatient "me first" motorists.

1 hour ago, BrendAn said:

All these threads seem to get sidetracked but does it really matter.  

Has your enquiry been answered? That's important. If it has, then we can go waffling off on this side track without upsetting you.

Not having done any tests myself, but referring to some published figures, the Coefficient of Friction of steel on steel ranges from 0.5 to 0.8. The CofF between wood and metal was given as 0.2 to 0.6.

Basically that says that there is likely to be more sliding of steel on wood that simply steel on steel.

Just to clear things up, the Coefficient of Friction is the ratio of the downward force generated by an object due to the acceleration due to gravity and the force required to move that object in a direction other than down.

Initially when you start to move one object over the surface of the other the microscopic lumps and bumps on both surfaces interlock, making it necessary to use more force to move the object you want to move. That friction is called static friction, and is the highest value you will get in your test results. Once the object you want to move gets going, the force required to keep it going is less. That's kinetic friction (kinetic = moving). I'll use this graph simply to illustrate the shape you get if you graph the instantaneous CofF  over time. Only look at the red and black lines and think of the label on the  bottom being Time.

Initially the CofF is high (static friction), then it decreases. In the example of the steel, once the steel gets moving it's easier to move it. Remember pushing a car? Similar thing.

6 hours ago, 440032 said:

Perhaps clarify for the readers, you're only talking about a different tyre, nothing else?

 

I read it s putting on Tundra tyres.

10 hours ago, Old Koreelah said:

Another aspect is engines overheating  while takeoffs are delayed- a big issue where small batches of planes are marshalled to backtrack before TO. When it’s happened to me, all I needed was enough space to pull out of the line for a cool-off period.

Thanks for that comment. I will have to take that into consideration when organising departures. I won't be doing all the planning myself. I'll  have CFI's to give input, and people who have competed in similar events to give me a debrief. Don't forget I've just started this planning process so I don't have all the answered. Heck! I don't think I know all the problems.

Here's one to mull over: The event is open to persons with a current permission to fly from a licensing authority . CASA says 15 years old to fly solo on a student licence and 16 for what I'll call a go anywhere pilot's licence. CASA does not specify an age for a commercial licence. It is usual for race rules to require that an entrant who is under 18 years of age to provide written permission from a parent or guardian to participate in the event.  Should the rules exclude a 17 years 6 months old licensed pilot without the permission to participate? The kid can legally drive to the airport without permission. I'm the one who is making the rules for the event.

The reason I ask is that I want to invite the Scouts Aviation Activities to participate. There could be other Young People too who are not in that mob.

15 hours ago, APenNameAndThatA said:

Turbulence is caused by variation in air velocity, not variation in air density. It might be that that misunderstanding would be decreased if people stopped talking about air pockets.  

 

If aircraft sank when they flew into less dense air, then they would sink when they flew into thermals of rising air. Air in thermals is hotter and therefore less dense than surrounding air. 

Well, that's got me gob-smacked. I don't even know how to reply.

BUT:

After correct torqueing, may be necessary to turn the nut again up to 30 degrees (in either direction) to locate the hole. With six notches spaced at 60-degree intervals, the castellated nut can only be locked where a notch corresponds to the hole. As fine-tuning the torque is not possible, castellated nuts are better suited to low-torque applications. 

Is it usual to have a specified torque value for bolting a prop to a hub?

We might know nuthin', but Pprune fellas know f all.

2 minutes ago, facthunter said:

Ther's NO such thing as an airpocket.

Well, what do you call it when you are flying along, fat; dumb, and happy and your aircraft suddenly drops 50 ft then jumps back to where it started?  Or same fat; dumb, and happiness and your aircraft suddenly lifts or drops?

When everyone gets the gist of what is being discussed, can't we use layman's terms for the sake of brevity? Or do we have to go through the minutiae of the endochronic properties of resublimated Thiotimoline ?

1 hour ago, Bruce Tuncks said:

The variations in rotational speed come primarily from the pulsations from the power strokes.

I missed that source of vibration. I was thinking of the propeller producing Lift longitudinally. All other things being equal, the amount of Lift is dependent on air density. What happens when a plane flies through an "air pocket"? Air density decreases; Lift decreases and the plane moves away from its steady state path. Then it flies out of the "air pocket", air becomes denser and Lift increases. 

Apply that thought to the propeller at the same time. It seems logical that going through the changes in air density would result in changes in the Lift (i.e. Thrust) forces it creates. Surely that must induce fore and aft vibration that expresses itself at the Boss/hub interface as rubbing. And rubbing induces heat.

Support from CASA ??? You velly funny man.

CASA say this https://www.casa.gov.au/sites/default/files/2022-06/interim-air-display-administration-procedures-manual.pdf.

It's got more hoops than an ante bellum Southern ballroom.

5 hours ago, APenNameAndThatA said:

That sounds ludicrous, but it you can provide a reference of some sort I’ll stand corrected. 

Isaiah 55:8-9

1 hour ago, Thruster88 said:

Because the prop flange on a rotax has M8 METRIC, YES METRIC THREADS IN THE FLANGE. do keep up.

Not relevant to what I was saying. I was replying to a comment about castellated nuts being retained by cotter pins, but that the cotter pins only stop a loose nut falling off. By the time the cotter pin has saves the nut, the clamping function of the nut/bolt combination has gone with the wind. I was suggesting that if one was to use bolts with drilled heads and shank holes as well as nuts with corner drilled jam nuts, then safety wired the heads of the bolts and the nuts at the other side  you would be doubly secure, hence "belt and braces"

Like I said. This would be a fun event to have, until the bloody ambulance chasers got wind of it. You should see the hoops I have to jump through simply to submit an application to CASA to organise the event.

I'm sorry to say it, but I've got a few years of life to enjoy and I don't think dealing with vast tomes of rules, regulations and what-ifs? is going to add to that enjoyment.

Maybe the best thing to do is say, "here's my phone number. If you want to stop for break at my local aerodrome, give me a call and I'll arrange ground transport"

1 hour ago, turboplanner said:

The normal procedure is for the promoter to take out a PL policy for the event, to cover risks

That's about it. Aircraft owners will have to insure their property against causing injury through its operation, and the organisers will have to insure against the usual trips and falls. Do the ladies of the CWA insure against their cakes causing toe-and-mane poisoning?

The whole idea might go to pot if CASA says, "No". I contacted them this morning and they said to send what information I have and they will see if the event can go ahead. Can you all please give a donation of Luck, 'cause I reckon I'll need lots to get past CASA? They even want to charge a fee for assessing the application!

3 minutes ago, facthunter said:

The drive hub of a prop can get quite hot.

Stands to reason. The bolts are pulling the prop boss and hub together by creating forces acting in a longitudinal direction. At the same time there is that transverse force created by the rotation of the propellers matter. Over the length of time that the engine is running, per flight, minor variations in the speed of rotation can cause microscopic amounts of movement between the propeller boss and the hub. That little bit of "rubbing" creates the heat that facthunter has mentioned.

1 hour ago, walrus said:

What does the propeller manual say? As far as regulations are concerned you require "approved data". That is a hierarchy starting with manufacturers instructions followed by engine manual, airframe manufacturer, POH, etc. on downwards to AC43-13b.

 

No argument there. But it's good on internet forums to go wandering down the "Why is it so?" path. If BrenDan is doing work on his own aircraft, then wouldn't it be nice for him to have some background understanding of the hardware available to do the job it is doing?

In order to cut out any need for en-route refuelling, I've redesigned the route, and calculated some indicative times for point-to-point flights. Now it is down to about 2 hours' flight time and about 140 NM. Now the route really does get you Winging down the Castlereagh. Hopefully I can arrange a supply of Mogas at Tooraweenah.

It starts at Tooraweenah and goes in a clockwise direction. That will bring aircraft back to Tooraweenah so they overfly and descend to join on the crosswind leg. I think that would be safer than the earlier route which had the potential for straight-in approaches.

Indicative Times Route 2.docx

22 minutes ago, Bruce Tuncks said:

If you use cotter pins and castellated nuts, you have to live with the thought that these items do nothing until the bolt has come loose a bit.

That is quite correct.

If you want to go the "belts and braces" approach, why not use an ANH7-xx  with one NAS509-8 nut with AN970-8 washers, then safety wire the heads and nuts?

7 hours ago, Thruster88 said:

For anyone not familiar with the Rotax prop flange it has metric M8 threads.

 

AN hardware including metal loc nuts CAN NOT BE USED.

I can see that prohibition being associated with the certification of the components for use in aircraft. Fair enough. But if someone wanted to go down a long an dank passage, they could get an Engineering Order to us Imperial-sized hardware. At least that way owners could get hold of hardware that had certification of quality and traceability.

As for differences in raw materials, a bit of metal rod of known tensile and shear strength doesn't know if it is going to be machined to make something to metric or imperial specifications.

Be careful when using the descriptor "AN" when ordering hardware. There are several other descriptors for aerospace hardware. These other ones post-date the AN descriptors in most cases simply for commercial reasons, nothing to do with the specifications of the item. https://www.flywithspa.com/docs/pbm/toc453317738.html

Certified General Aviation aircraft many times uses the old part number as that is what the aircraft was certified with, and experimental aircraft typically follows the old numbers because the certified ones do.  Various hardware supply companies will ship the hardware with different numbers from what you order on the website.  Aircraft Spruce will list AN365 in the catalogue, but ship it in bags labelled MS21044. You can't tell your AN from your MS.

I believe that Nylocs are a no-no forward of the firewall. If you want to use locking nuts, go full metal. 

An M8 bolt should have an 8mm diameter, a 5/16 (dash 5) imperial bolt has a diameter of 7.9375 mm. That's about a poofteenth's difference. If you use a good old AN5- bolt with MS21045-08 nuts. Or you could go the close tolerance route an use AN175-5 close tolerance bolts.

So $100 would be fair for RAAus aircraft, and cheap for anything bigger?

I'm hoping to get some flying schools to fill a 4-seater so that more students get some nav practice. It's perfectly within the scope of the event for a crew of four (instructor + 3) to land along the way and swap pilots. All they would have to do is account for the time taken to land, swap seats and flock off. In fact, I might include a prize for the best pilot swap crew. Anything to make the event more fun and valuable to the contestants.

Before you go crazy, step back and consider what the bolt, or any fastener, is doing.

In the picture above, the bolts are clamping the propeller boss to the crankshaft end plate. 

Why 6 bolts? To balance the forces generated by the rotational forces created by the movement of the propeller. Leave just one bolt out  and the prop will shimmy like a jelly on a plate.

What is the most important type of force in this situation, tension or shear?

This is failure in shear   causing the bolt to split across its diameter, and this is failure in tension  where the bolt stretches.

You are trying to keep the surfaces of two objects together along the longitudinal axis of the bolt. You are employing tension forces which are trying to stretch the bolt longer. 

The rotational forces produced by the spinning prop will create some shear force to the bolts, but each bolt in this case only has to deal with 1/6th of the total shear force. For a particular prop, the rotational force  F = m v² / r    is limited by the weight of the prop, the location of the centre of mass in relation to the radius of the prop, and prop RPM. A decent M8 bolt should have a shear strength on its grip length of 39 kN and on the fine threaded section about 19 kN. You wouldn't be worrying about shear strength unless you don't use an even number of bolts

Wot! No cup holders !!!!

I like the double redundant fans to keep the pilot cool if the big fans stop spinning.