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Author Topic: Nieuport 11 Bebe - Build  (Read 24227 times)
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billdennis747
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« Reply #375 on: February 18, 2017, 02:16:37 AM »

When I have thought about rotating motors I have wondered about putting some unobtrusive vanes in between and behind the cylinders to allow the engine to windmill and give the effect without using power from the rubber...
That's how Pete McDermott rotated his engines on his World Champs RC Snipes and Triplane. I don't think it even needed vanes. It just ran on bearings on the engine, turned by the airflow, although there would be more airflow from a Laser engine than a rubber prop
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Andrew Darby
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« Reply #376 on: February 18, 2017, 04:04:38 AM »

Super work Rich.  Until I read your thread properly I thought you had made those pipes from copper tube that had been curved and squished at the ends, so they looked very convincing to me!  The whole thing looks so realistic.

Wonderful.

Andrew
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Rich Moore
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« Reply #377 on: February 18, 2017, 07:54:19 AM »

I was playing with copper. I got some copper brake pipe that was the correct diameter and some spring benders to prevent kinking. It wasn't too difficult to make a convincing part, but it was thick walled which made it way too heavy, even for me. I tried thin walled copper tube but couldn't bend it tightly enough without it kinking. And still too heavy. When I gave in and made a balsa one and painted it, I felt a bit foolish for trying. Got to love balsa wood and a bit of paint.
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daveh
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« Reply #378 on: February 18, 2017, 02:35:38 PM »

Pete Iliffe gets rotary engines to rotate simply by making them a sliding fit on an extended prop shaft and letting friction do the rest. Seems to work a treat.

Dave
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Rich Moore
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« Reply #379 on: February 18, 2017, 03:14:29 PM »

OK, so either the engine is fixed on the prop shaft (as currently planned), or it is a loose fit. The advantage of the loose fit, I guess, is that more of the initial power will be transferred to the prop for the initial climb out before the engine catches up. I don't think the engine being fixed to the prop shaft on the Dr.1 gives any problems though, so I'm inclined to do the same, although this engine is bigger and heavier.

Having said that, my thinking a while ago was around a loose fit which would give me the option to constrain the engine and fly with no rotation. I hadn't thought about the 'half-way' option of letting it spin under friction. So I think I'll revert to that thinking, which will give me 3 options :-

 1. Engine rotating, fixed to prop shaft (grub screw)
 2. Engine rotating, loosen grub screrw so engine loose on prop shaft, but allow friction of bearing to turn engine
 3. Engine constrained, loose fit on prop shaft but engine prevented from turning. Some kind of restraining pin through engine to cowling/ firewall/ somewhere appropriate

Mmmm...

Anyway, currently adding a few missing bits of carbon to upper wing T/E's, and balsa reinforcement to wing roots - got cyano on all finger tips, so can't feel the typewriter. Nothing exciting.
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Prosper
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« Reply #380 on: February 18, 2017, 04:46:11 PM »

Quote from: Rich Moore
Mmmm...
This reads like an 'O' Level Physics question. The candidate would reject 3) realizing that a rotary engine is not a radial engine and must rotate as a basic condition. S/he would then have to rack its brain to see whether 1) or 2) caused most energy loss.  My instinct says have it fixed to the propshaft, however heavy it is. Bearing friction is lost energy, lost to heat and noise. If the engine is fixed to the propshaft yes the rubber motor's 'torque burst' has to spin the engine up, but once going it's a flywheel, absorbing relatively little energy - and can even deliver that energy back to the propshaft (minus what it's lost in its thrust bearing arrangement, and air drag as it rotates).

Having passed my 'O' level rather a long time ago I'm more than able to take it if my (cough) 'instinct' is utterly wrong - better get a second opinion Rich but that's how I see it.

When I saw your engine photos I thought you'd ditched the rubber power and were going for a working miniature rotary IC engine. Fantastico!

Stephen.
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Rich Moore
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« Reply #381 on: February 18, 2017, 05:07:12 PM »

Hi Stephen. My instinct says fixed as well, especially as it worked fine last time. But, I may as well have the ability to slacken the grub screw and let it lag along if it doesn't complicate matters, although I'm not sure what it would really achieve. I'm not really interested in it not spinning, as you say, it ain't a radial, but it would be easy to jam it with this arrangement. It does sound like an indecisive, non-committal option. In reality, I don't know what I'll do until I actually do it. 
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F F modeller
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« Reply #382 on: February 18, 2017, 05:14:47 PM »

How about a 'reverse lawnmower clutch' that engages more as the torque decreases?
Might be overthinking this now!  Roll Eyes
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Rich Moore
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« Reply #383 on: February 18, 2017, 05:43:25 PM »

Aaargh! I'm not going to think about it anymore. I'll just stick the bloody thing on.

Anyway, talking about committing, I've just epoxied in my lower wing dihedral/ sweep-back keepers. These are 1/16" lengths of piano wire, bent to the combined dihedral/ sweep-back angle, that insert in the wing spars. These needed to be epoxied to a tube attachment on the fuselage, but getting the correct dihedral and the correct sweep-back simultaneously has given me a headache. Rotating these metal dowels gives more or less sweep, but obviously the dihedral changes as well and very little change makes a big difference to both. It is difficult to 'eye-in' the sweep-back to be parallel with the upper wing, because the upper wing does not have dihedral (versus the lower wings which do) and the apparent parallel-ness depends on your perspective. Anyway, in the end I just stuck 'em in the best I could, checking using a metal straight edge to project the sweep back and a bit of fine eye-balling. Close enough. That's another job I'd been putting off...
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« Reply #384 on: February 18, 2017, 07:25:07 PM »

Glad to hear that you are sticking to your sticking!
I'm sure you'll make it work.
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Rich Moore
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« Reply #385 on: February 23, 2017, 06:40:27 PM »

This is the nose-block. It is really a nose-block in a nose-block. The whole cowling assembly will be attached to the fuselage in a conventional manner via a large square plug into a big square hole in the fuselage, aided by 4x 6mm neodyminiuminny magnets. This may be overkill because these magnets are really quite strong, but this nose-block is very heavy and I can always reduce the number.

Attached to the 'firewall' of the main nose-block is a small nose-block assembly which allows for thrust-line adjustments of the motor shaft. The three 2mm threaded screws can be slackened off from the rear and spacers inserted, as they would in a conventional nose-block, to achieve an angled thrust line as required. Over-sized holes in the front face allow lateral adjustment so that I can keep things visibly central despite any necessary thrust adjustments. It works quite well - there is enough clearance between the engine and the cowling to get a good few degrees in any direction. If I need more room, I can reduce the supporting column and move the engine backwards which will allow more angled adjustment.

The engine is hollow which allows the thrust race to be as far forward as possible - I didn't want the propeller to be 'out on a limb' too far from the thrust race. The free-wheel is from Mike's build pages (ZK-AUD) and, being at the back of the prop, will allow the prop to be removeable. This allows different props to be tried and, importantly, a scale one for static judging. A pivoting wire dog attached to the rear of the flyng prop will engage between the two protuberances (nice word) on the brass disc. This is my first real attempt at soldering things to important thrusty bits. It went well first time around, but as so much solder ended up all over the brass disc when it should have been going between the brass tube and the piano wire shaft, I didn't trust it. I dismantled to find it was perfect and had to clean everything up and do it again. Not so tidy second time around, but it seems to be structurally sound as far as I can tell. The picture below with the clean brass parts are before any soldering!

I have given the rotary it's own brass bushing, so it is free to rotate around the main motor shaft. The last photo shows the hole in the extended engine bushing that allows me to clamp it securely to the motor shaft with a 2mm grub screw, or not, as I wish.

I am happy with the soldering, although not entirely trusting that it won't all fail on me and smash everything to pieces, but I'll have to trust it.
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« Reply #386 on: February 23, 2017, 07:00:55 PM »

You create solutions .... you are a creator as much as a modeller  Smiley
Always look forward to what you come up with next.
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Pete Fardell
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« Reply #387 on: February 23, 2017, 07:13:17 PM »

Great stuff, Rich! That's proper model engineering like I wish I could do. I really like the way everything- real cowling, thrust-line adjuster, rotating engine , freewheel, removable prop, the lot- has all been so well integrated, tailor made and thought through.

As a lowly bodger who still just wedges in unsightly plywood shims to adjust thrustlines (and then usually fails to notice when they fall out) I am in awe!
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OZPAF
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« Reply #388 on: February 23, 2017, 10:26:47 PM »

Very clever Rich and neat. I enjoy seeing innovative solutions that you and Mike(ZK AUD) display on your models. Great stuff.

john
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Andrew Darby
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« Reply #389 on: February 24, 2017, 02:40:53 AM »

Some very nice model engineering there Rich... Grin

Andrew
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Rich Moore
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« Reply #390 on: February 24, 2017, 03:05:32 AM »

Quote
You create solutions .... you are a creator as much as a modeller

Thanks Russ, I really appreciate that comment. Of course, I'm really good at creating the problems to start with...

Quote
As a lowly bodger

Bodging is engineering in my book. I very much believe in bodging. And the number of times I have said to myself "That's proper model engineering like I wish I could do"...
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Mark Braunlich
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« Reply #391 on: February 24, 2017, 10:04:10 AM »

Impressing the ladies too no doubt!   Looks good from here Rich.
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daveh
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« Reply #392 on: February 24, 2017, 04:35:41 PM »

Beeeeeyootifulllll...........

Fantastic model engineering Rich.

Dave
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Rich Moore
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« Reply #393 on: February 28, 2017, 01:33:29 PM »

Doesn't look like much but these struts have taken me a while to put together. 1/32" one piece ply core clad in balsa parts and then stained and varnished. Strong but with a bit of flexibilty. One of the few things remaining to be done before I can start covering is installing the slots in the wings to take the ends of the struts/ provide something to stick the covering to. The ply cores extend and clip to the spars. These will quickly wear out, so a friction fit into a slot that will release on impact seems a sensible way to go. There are 3 tapes to be wrapped around the struts yet, which will help hold them together.
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billdennis747
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« Reply #394 on: February 28, 2017, 03:06:28 PM »

Anything that involves sweepback, differential dihedral and funny struts gives me a headache!
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Rich Moore
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« Reply #395 on: February 28, 2017, 03:21:51 PM »

I made them by building mock-ups first. To make my life easier, I made a mock strut out of two separate pieces of balsa - one from the lower spar to upper rear spar and one from lower spar to upper front spar. I positioned them side by side and when happy, added a drop of cyano. This fixed them into the 'squashed V' and became a template for a second mock strut, and also the two final ones.
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Andrew Darby
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« Reply #396 on: February 28, 2017, 04:59:24 PM »

Anything that involves sweepback, differential dihedral and funny struts gives me a headache!

You will have problems with a Tiger Moth then!  It gave me a real headache!  Cheesy Grin

Andrew
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« Reply #397 on: February 28, 2017, 06:45:38 PM »

Anything that involves sweepback, differential dihedral and funny struts gives me a headache!

You will have problems with a Tiger Moth then!  It gave me a real headache!  Cheesy Grin

Andrew

Probably why he builds so many Puss Moths......
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Pat D
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« Reply #398 on: March 01, 2017, 04:36:02 AM »

Hi Rich

What do you use to stain the struts ? it comes out very nice !

Pat


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Rich Moore
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« Reply #399 on: March 01, 2017, 12:55:55 PM »

Hi Pat - it is furniture wax! An old tin of Colron furniture wax 'for pale wood' that I've had for years. It'll probably last me forever as I only use it for things like this. I find it makes balsa look more grown up! These struts have also had a coat of clear gloss acrylic varnish.
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