meninspex

Remarkably similar! . The reason I am sure of the cut-off date for my engine is that my dad had to cease active aero modelling in the mid 1950s due to ill health. The only differences I can see are in the head which is less curved on my engine and the chamfer on the web behind the air inlet which has a longer flat on my engine. I've tried to take a photo at the same angle as yours for comparison but I'm a better engineer than photographer!

brokenenglish

Yes, if the two engines were side-by-side, I wouldn't mind betting that yours would be more compact, i.e. physically smaller and lighter than the production PAW.
Anyway, you have a couple of superb engines (not to mention all the others!).
What great engines these are. I started using (flying) PAWs in 1960, and I'm about to go flying this afternoon... with a PAW!
BTW, "meninspex" even sounds like Gig!

buzzard bait

Interesting photos...I've never seen a PAW like that. The production ones you get now are quite long from prop drive to back plate. I'm sure that's useful in some applications, but for scale models of the old snub nosed WWI rotary types you can't fit them under the cowl without having the prop shaft stick out in an un-scale manner. Of course, that's exactly the kind of application where you want the ability to swing a large prop. The older design would be much better suited.

Jim

Recycled Flyer

The short snout would seem to benefit control line combat with their short length models that turn incredibly tight at high speed.

74SEVEN7

Anyone want to venture an opinion as to how the crankshaft and bearings on the rear induction "Special" were fitted - it has a sealed (as cast) backplate, combined with a non-removable front end. The front induction "Special" has a screw-in backplate

brokenenglish

To state the obvious, everything must have gone in through the front. The disc valve would have to be inserted first, then the bearings and shaft could be assembled and installed in an outer tube, like a sealed bearing assembly, and this assembly could be inserted and possibly retained by the set screw on the top of the bearing. The con-rod would have to be assembled onto the crank pin just before the crank pin located in the disc valve, more or less in one operation.
In other words, I think the set screw is there to retain the bearing/shaft assembly in some way.
Gig was a very practical person and I think it's probably significant that he didn't continue using this layout!

74SEVEN7

Such a simple and commonly performed process !

brokenenglish

You can't really see from the photos, but it's possible that a reed valve was installed first, which would slightly simplify the rest of the job.
It's also possible (likely even) that Gig saw this method as a means of accurately setting up the shaft/bearings assembly first, outside the crankcase.

fiery

My Feedback: (2)

"Red Zephyr" with his PAW 1.49 R/C powered "Mills Bomb" at our local field.

Simple pleasure at its best.

https://www.youtube.com/watch?v=1qN-...aDm-zA&index=5

https://www.youtube.com/watch?v=YxLa...aDm-zA&index=3

AMB

OK all theory question I have a number of Irvine 40s which of course has the front of the crankcase carrying the crank bolts on with the 4 screws
1. If the crankcase front casting were rotated 90 degrees would it run in reverse (clockwise) ?

2. If we rotated it an other 90 degrees would in run as designed counter clockwise this would be a nice feature in a plane if mounted inverted since
carb would be on the top thx martin


WHOOPS ERROR ERROR those are irvine 40s got my Brit engines confused not PAW 40

greggles47

Hi Martin,

In case 1 above, apparently this is right. I have no first hand experience of doing this myself but have heard it said many times.
In case 2, presumably also correct, but it may cause fuel draw problems or at least affect the running when going from upright to inverted & vice versa.

AMB

thx Greg for the come back again it was a question and have no need to do this martin

Mr Cox

Just because you can rotate the front, doesn't mean that the method will work on any engine. On Enya engines they have made the intake timing "symmetric" such that if you rotate the front 90° (to get carb on the right-hand side of the plane in an uppright engine) you have exactly the same timings for the intake in reverse running. This requires a total intake opening of 180° and an intake that closes at 45° after TDC. So they have in fact compromised the intake timing in order to have this feature on their engines.

Rotate the carb another 90° and the intake timing will now be completely off, so you only have two choices: carb up or to the right-hand side.

brokenenglish

The answer to most "theoretical" questions is to just "go and try it"...

AMB

this could be an advantage on a twin left engine counter clockwise right engine clockwise??? martin

brokenenglish

I dunno but, in any case, you won't be able to do it on a PAW...

Recycled Flyer

Was under the impression that rotating the intake -90 degrees on Enyas 'closely' approximated the timing as compared to having it at 0 degrees regardless of having symmetrical intake openings or not.

(From memory "Supercool Props' had an article stating just this.)
http://www.supercoolprops.com/articles/enya.php

Are you certain that Enya deliberately designed the intakes with a possible -90 degree twist in mind?

brokenenglish

Jeez, it would be nice if we had a post just remotely related to PAW...
I don't think Gig had anything to do with Irvine design or Enya timing...
There's no PAW with a front housing that can be rotated to solve torque problems on a hypothetical multi-engine plane flown as a pusher, or even to generate clicks...

Mr Cox

I do like PAW engines too, but would still like to comment on the Enya engines...

I have only measure this in detail on the Enya 09 IV, so I haven't check if they did this on all of their engines. If you make a timing diagrame you'll see that this idea will only work perfectly if the intake opens at 45° after BDC, and closes at 45° ATDC. When the front is rotated by 90°, then 45° ABDC will now be at 45° ATDC in a reverse rotating engine (and similarly for the other timing point).

From the link earlier;
ENYA 35 - lll B shaft timing, normal configuration - With housing on the side ( reverse rotation )
Port opens at 48 deg. ABDC Port opens at 46 deg. ABDC
Port closes at 48 deg. ATDC Port closes at 50 deg. ATDC

This data doesn't add up to me, I think it is due to measurement inaccuracy and possibly a rotation that was not a full 90° rotation.

brokenenglish

Maybe you should start an Enya thread!
There's not much point in having a PAW thread to discuss obscure operating principles relating to other engines.
I intended this thread to be at least related to PAW...

Recycled Flyer

Not unless you want to delve into some of Gig's experiments ........... but anyhow I am betting that if asked for a left hand crank shaft could be ordered since these engines are all hand made anyway.
Cheers.
P.S. You will probably find that the above pictured PAW is not the first engine done by Gig and a lot of early design knowledge was commonly copied between manufacturers, so all brands are related to each other in some way, shape or form.

http://www.rcuniverse.com/forum/ever...iguration.html

Link to the same.

brokenenglish

For your first comment... You didn't read the post. Of course it's not the first engine made by Gig... but it is the first PAW, and that's what the photo states...

Your second comment that all model engines are related to each other is surprising... Either it's meaningless (so what?) or it simply negates the possibility of discussing any individual brand. We end up discussing "rotating front housings on Irvines and Enyas" on the PAW thread... and no point in having any marque-related threads at all...
Is that what we want?

Lou Crane

Mr. Cox, to your brief post on Jan 15, 2015, re: reversing rotation by turning the front end 90° on an engine with symmetrical, square bolt pattern, front end assembly...

In my limited experience - not more than a few dozen examples - shaft intake timing is usually within few enough degrees of symmetrical to at least allow reversed running.

Most sport, as opposed to specialized, high-performance, engines do have the timing gently "biased" to favor the stock direction. The duration remains the same, but the open/close times in shaft degrees, shift. The engine loses any advantage of the stock "bias" when run reversed.

I believe you took part in at least one earlier thread discussing this...

I usually describe the results in words, and appreciate your using numbers to illustrate what happens. My literal description is: - turning the front housing 90° either way shifts the port opening 90°, AND the front housing port passage meets the edge opening 90° earlier (or later, accordingly) in the opposite direction, completing the "180°-ish shift" in port-timing.. Completing the reversal, that is...

In the early 1970's, I degree-wheeled as many engines as I could get my hands on, and drew circular degree charts of the shaft and sleeve times. Didn't have diesels in the selection, regrettably. Yet, not so unfortunate... Diesels with enclosed contra-piston upper ends do not yield dependable cylinder port opening direct measurements. The adjustable contra is part of that. Scatter of measurement readings with a degree wheel for both shaft and cylinder ports killed my confidence in that method, anyway. I now prefer accurate measurements and some analytical computations. I expect bearing slack in the rod precluded consistent, accurate degree wheel readings.

There's a relationship between piston travel and shaft degree change: - If I recall correctly, for around .40 size engines it is about 0.005" per degree around the sleeve port opening range of degrees ATDC. I can work within that range of accuracy for cylinder port opening distances from TDC, and modify these times as finely as 1° for Fox 35s I use.

Well within margin of error, I still found most measured "sport" engines had close to 180° shaft port duration, with port opening 'times' in the vicinity of 45° delay past BDC and TDC. Gas inertia and the relatively small vertical piston movement in those parts of a revolution broaden tolerance of exact port opening and closing times, it seems.

I flew a rotated-front-end ENYA 29-III, back in the late 50's/early '60's (in a modified VECO Smoothie stunt model) and, later, a factory shaft LH Fox 35 in a deBolt All American, Sr., in the early 1990's.The ENYA provided plenty of power, but I didn't get it totally sorted out. Current ideas on fuel tank location and venting were not in use, then. We were still drafting young men to military service, and my number was coming up. (Didn't let them draft me; found a promising duty field and enlisted for it. It became a gratifying career!)

I campaigned the LH Fox model for several years in Old Time Stunt, happily with success commensurate to my skills. Its "manners" were as consistent as a stock RH engine, with the torque advantages that led many early USA CL fliers to fly clockwise. Power was, apparently, identical, as far as could be detected. The shaft timing may have been tweaked at the factory to secure that result, but I doubt much if any change was needed.

(The advantages? Turning the prop takes torque. This basic torque reaction on the engine mounts tends to raise the wing the upper prop blade turns towards. When flying CCW that causes a CW-engine model to tend to roll away from the center when upright - more comfortable than a tendency to roll IN, slacking the lines! Reversing prop rotation obtains the same effect while flying CCW upright - today's effective standard. I can fly CW, but it feels alien. )

So, in fine, it IS likely to work, with some -perhaps mostly theoretical- loss of advantage from factory 'biasing' the stock engine timing. CL Stunt does not require extreme RPM or power. Any penalty from losing the CCW 'bias' in timing should be easy to overcome. It was for me, more than once.

buzzard bait

Very interesting but it proves brokenengish is right...start another thread! Two advantages: first, a thread on PAWs doesn't get hijacked, and second, other people interested in Enyas and such would have better access to this discussion.

Recycled Flyer

Hi Brian,
I was running on the assumption that PAW was founded in 1941 (because that claim is on their own web site) and the your "First PAW ' picture must date from about 1950?
And Gig certainly made engines prior to that but of course PAW timelines are fraught with danger.
The picture that you show, is that an unedited factory supplied one because I see that you have others like it on Youtube?

No, the thread should remain true to its purpose but that's not what I meant.
Every thread drifts from time to time because of the commonality of design and comparisons are unavoidable in an effort to gain perspective.

Anyway, on with the show.

Cheers.