Author Topic: Exhaust timing of an OS .46LA??? (Read 4904 times)

Steve Helmick · « **on:** July 03, 2011, 02:58:37 PM »

Anybody got exhaust timing numbers for the .46LA? Going to put one on a kit Pathfinder with an "ES" pipe.

Steve

Steve Helmick · « **Reply #1 on:** July 16, 2011, 10:54:37 PM »

Got an email from Andrew Tinsley. He got busy and checked the exhaust timing on 3 OS .46LA samples, and got 134 to 136 degrees. That's quite reasonable tolerence, if you look at difference, and finding zero, in thousandths of an inch.

Thank you, Mr. Tinsley!

Steve

rustler · « **Reply #2 on:** July 17, 2011, 01:23:17 PM »

Confess I haven't measured one but I assume a 40 would be the same.

Andrew Tinsley · « **Reply #3 on:** July 17, 2011, 02:53:02 PM »

Hello Ian,
I am afraid that I don't have an LA 40 to check out, but it wouldn't surprise me if the exhaust timing was different. It would explain why the 40 isn't as good out of the box as a 46!

Regards,

Andrew.

Chris Wilson · « **Reply #4 on:** July 18, 2011, 11:00:42 PM »

Quote from: Steve Helmick on July 03, 2011, 02:58:37 PM

Anybody got exhaust timing numbers for the .46LA? Going to put one on a kit Pathfinder with an "ES" pipe. Steve

From ALCN 70 5 -

For the number crunchers among you, the stock LA46S
weighs just over 9 ounces, has a venturi of 285 thou and
the internals clock-in at 142 degrees exhaust, 115
transfer, 41-37 shaft inlet and 10.2:1 compression.

Andrew Tinsley · « **Reply #5 on:** July 19, 2011, 03:18:43 AM »

Hello Chris,
I take it that the figures you quote are the official OS specifications. I am a bit shaken at the exhaust figure of 142 degrees. That is a sizeable difference to the figures that I measured. I was using an 8 inch diameter 360 degree protractor and a fixed marker needle that touched the back of the wheel (to minimise parallax). I also used a white light Led dropped through the plug hole, to make it easy to see when the exhaust port opened. I also averaged a number of readings on each engine. I would estimate an error of at maximum 0.5 degrees.
I will rerun my measurements and make sure that it isn't something simple like an inability to subtract! Mind you I did measure three engines and found a difference of 2 degrees between two of them. Makes me wonder what is going on here?

Regards,

Andrew.

Steve Helmick · « **Reply #6 on:** July 19, 2011, 02:07:02 PM »

Chris....What is ALCN 70 5 ?

Steve

Chris Wilson · « **Reply #7 on:** July 19, 2011, 04:25:30 PM »

Quote from: Steve Helmick on July 19, 2011, 02:07:02 PM

Chris....What is ALCN 70 5 ? Steve

Hi Steve,
please check the sister thread next to this one 'reworking LA46' - the actual file name is ALCN 70, the '5' is the number of times I have downloaded it!
(I have learnt something here too.)

Cheers.

Andrew Tinsley · « **Reply #8 on:** July 20, 2011, 04:28:49 AM »

I have just rechecked the measurements I made on Monday, they are as I quoted. I tried a fourth LA 46 and got 138 degrees for this one!

Regards,

Andrew.

rustler · « **Reply #9 on:** July 20, 2011, 03:11:44 PM »

Andrew - Rather than using a light, how about a thin sliver of tissue paper? You can feel as it just catches at the top of the ports.
As regards the 40 timing, I would assume all other dims are the same, i.e. piston depth, port heights and positions, pin height in the piston etc. , purely from an economy of production point of view. If this is so, I think the timing would be the same.

Andrew Tinsley · « **Reply #10 on:** July 20, 2011, 03:39:59 PM »

Hello Ian,
I am willing to try any suggestion. I will nip down to my village shop and get the necessary cigarette paper. I would have thought a light inside the cylinder would have been pretty accurate, but you never know!
The thing that puzzles me is that there may be a systematic error in the way I am measuring the exhaust timing. but I am getting the same values for the engines checked, each time that I make the measurements. There does appear to be a variation of 4 degrees between the two extreme results. This does seem to be a real difference between the engines checked. Does the deck height of these engines really vary by this much to produce a difference of 4 degrees?
I remember that Len Neuman, has said that some of the OS engines do have a fair variation in deck height, so this may be what I am seeing. I will redo the measurements using fag paper as an indicator! Now what is the thickness of cigarette paper, because I suppose that I need to take that into account!

Regards,

Andrew.

Steve Helmick · « **Reply #11 on:** July 20, 2011, 05:01:14 PM »

Andrew...You could stay home, and pay a clandestine visit to the kitchen to nip a bit of aluminum foil. The sample I just miked is .0012" thick. I would be more concerned with how you find BDC...dial indicator, thumbnail or eyeball?

FWIW, GMA told me in an email that his rule of thumb was .001" = 1 deg. for most engines, but more like .0015" for bigger engines. He didn't define "bigger". I'm thinking that the stroke makes the difference, and bore would matter not? As the .46LA is the same stroke as a .40FP or .40LA, I think all would be fit the rule of thumb the same. If the bore is the factor that makes the difference, the .46 is a very large bore for a .46...same as a few .60's. This was to help translate timing into numbers to which George's Rockwell milling machine could relate.

What this tells us, is that a difference in deck height of the case or port edge of .005" (not very much!) would make about a 5 degree change. If the case was .005" to the high and the liner also .005 higher than nominal, you've got quite a change in timing, around 10 degrees. In the case of OS, I think they do a whole lot better than that. It is possible that they seperate parts into groups and put cases that are .005+ together with liners that are .005-, but I doubt if OS needs to do this. I'm sure some of the PRC makers do, if not all. That doesn't mean they're bad, but you may need to do some fitting to make replacement parts work as well as the originals. Don't feel bad about that, because Italian made ST's were much the same. Spare parts were merely a way to make use of the rejects, IMO.

Steve

Andrew Tinsley · « **Reply #12 on:** July 20, 2011, 08:17:12 PM »

Hi Steve,
I did in fact measure BDC with a dial gauge through the plug hole. As far as I am aware the exhaust period is simply the number of degrees from piston uncovering the top of the exhaust port to the point when the exhaust port is closed off again. Unless the engine has a De Saxe (Sp?) layout, then the exhaust timing has to be symmetrical about BDC, so there is no reason to find the BDC unless you are going to measure say the shaft timing, which is asymmetric as far as BDC is concerned.
As to the fag paper, don't know about the US, but over here it is a slang expression for accuracy "you couldn't get a fag paper in the gap" being typical slang usage. So using fag paper is almost de rigour! Should be interesting to see if the suggested method will reveal a systemmatic error. I am convinced that the spread between engines is real and accurate. I must do my geometry and work out how many thou a degree is for the LA 46 at approx 70 degrees up from BDC

Brett Buck · « **Reply #13 on:** July 20, 2011, 08:40:04 PM »

Quote from: Andrew Tinsley on July 20, 2011, 04:28:49 AM

I have just rechecked the measurements I made on Monday, they are as I quoted. I tried a fourth LA 46 and got 138 degrees for this one!

Just to validate your measurements, I measured one of mine and it was 138. I can routinely get the right answers on other engines so I am pretty sure that's right for the LA. Two possibilities - they changed is since the previous article, or it was wrong in the previous article.

Brett

Geoff Goodworth · « **Reply #14 on:** July 20, 2011, 09:40:32 PM »

Check out the link that Chris Wilson provided for the September 2003 Australian Control Line News in the thread on reworking the LA 46.

In his article on the LA 46, Derek Pickard quotes timing figures.

Cheers

Geoff

Don Hutchinson AMA5402 · « **Reply #15 on:** July 20, 2011, 09:52:32 PM »

My calculations show a piston travel of very close to .005" per degree of crankshaft rotation in the area between exhaust opening and bypass opening. This on an OS 40FP.

Chris Wilson · « **Reply #16 on:** July 20, 2011, 11:02:23 PM »

Quote from: Brett Buck on July 20, 2011, 08:40:04 PM

Just to validate your measurements, I measured one of mine and it was 138. I can routinely get the right answers on other engines so I am pretty sure that's right for the LA. Two possibilities - they changed is since the previous article, or it was wrong in the previous article.

Brett

Bingo! I would trust your own eyes mate and take into account that the supplied link mentions a modified engine - so when was the timing measured?

Straight from the factory or after monkeying around with it?

Andrew Tinsley · « **Reply #17 on:** July 21, 2011, 11:43:46 AM »

Thanks Brett,
I suppose I should have trusted my measurements, its nice to know that someone else is getting similar results! I have been nobbled today to do domestic duties. Derusting and painting a swing frame for my grandson, who is coming on Saturday! So I have not done the fag paper trick, nor calculated the degrees per thou for the LA46. I am afraid that the Boss is more important than toy engines!

Regards,

Andrew.

Geoff Goodworth · « **Reply #18 on:** July 21, 2011, 07:32:01 PM »

From the Derek Pickard article in ACLN:

For the number crunchers among you, the stock LA46S weighs just over 9 ounces, has a venturi of 285 thou and the internals clock-in at 142 degrees exhaust, 115 transfer, 41-37 shaft inlet and 10.2:1 compression. These are typical radio numbers and very much in line with the old FP engine specs with the big differences being the LA’s small transfer ports and the plastic backplate.

Brett Buck · « **Reply #19 on:** July 21, 2011, 09:33:24 PM »

Quote from: Geoff Goodworth on July 21, 2011, 07:32:01 PM

From the Derek Pickard article in ACLN:

For the number crunchers among you, the stock LA46S weighs just over 9 ounces, has a venturi of 285 thou and the internals clock-in at 142 degrees exhaust, 115 transfer, 41-37 shaft inlet and 10.2:1 compression. These are typical radio numbers ...

"Typical radio numbers", ay carumba! Also pretty close to an engine that has so far proven unbeatable in stunt and is the most turn-key stunt engine ever made - the OS40VF.

I would guess that the timing has changed in production since the measurement was taken.

Brett

Jim Kraft · « **Reply #20 on:** July 22, 2011, 01:42:06 PM »

Andrew; I believe your light in the cyl. should be the best way to see the opening and closing. That is the way I have always checked them anyway.

Tim Wescott · « **Reply #21 on:** July 22, 2011, 01:52:42 PM »

Quote from: Andrew Tinsley on July 21, 2011, 11:43:46 AM

Thanks Brett,
I suppose I should have trusted my measurements, its nice to know that someone else is getting similar results! I have been nobbled today to do domestic duties. Derusting and painting a swing frame for my grandson, who is coming on Saturday! So I have not done the fag paper trick, nor calculated the degrees per thou for the LA46. I am afraid that the Boss is more important than toy engines!

"Honey, I'm going into town to get some cigarette paper. And Honey? Have you seen that tin that I got from the college student the other day? You know -- the guy who had the purple car with the smiley faces all over it?"

RandySmith · « **Reply #22 on:** July 22, 2011, 03:49:02 PM »

Quote from: Brett Buck on July 21, 2011, 09:33:24 PM

"Typical radio numbers", ay carumba! Also pretty close to an engine that has so far proven unbeatable in stunt and is the most turn-key stunt engine ever made - the OS40VF.

I would guess that the timing has changed in production since the measurement was taken.

Brett

unbeatable

PA engines

Winner!
U.S.Nationals - 1994,1997,1999,2000,2001,2003,2004, 2005,2009,2010,2011
U.S. Team Trials - 1995,1997,1999,2001,2003,2007,2009
Australian Nationals - 1997,1998,2009

Many Open Sr. and Jr. NATs wins

World's ,Advanced and Open National Championships
1994 NATs Open Winner Paul Walker PA 40 RE
1997 NATs Open Winner David Fitzgerald PA 51 RE
1999 NATs Open Winner David Fitzgerald PA 61 RE
2000 NATS Open Winner TED Fancher PA 61 RE
2001 NATs Open Winner David Fitzgerald PA 61 RE
2003 NATs winner David Fitzgerald PA 61
2004 WORLD GOLD Medal winner Bill Werwage PA61
2004 WORLD GOLD Medal winner Rob Gruber PA61
2004 NATs winner David Fitzgerald PA61
2004 Senior NATs winner Rob Gruber PA61
2004 Advanced NATs winner Orestes Hernandez PA61
2004 NATS Classic winner Bob Hunt Aero 36
2005 Sr Winner Rob Gruber PA61
2006 NATs Classic Winner Bob Whitley Aero 36
2006 NATs Advance Mike McHenry PA65
2006 World's Siver Medal Winner Dave Fitzgerald PA75
2007 NATs Classic winner Jim Lynch PA 40
2008 NATs Jr. Winner Ryan Young PA 61 RE
2008 NATs Classic winner Keith Trostle PA-40 Merlin
2008 NATs Advanced winner Germanio(Alex)Becerril PA 61 RE
2008 WORLD F2B Champion David Fitzgerlald PA 75 Merlin
2009 U S NATs Classic Winner Buddy Weider AT 36 AAC
2009 U.S NATs Champion David Fitzgerald PA 75 Merlin
2009 U.S. Team winner Bill Werwage PA 61 RE
2010 U.S NATs Winner Bill Werwage PA 61 RE
2010 U.S. NATs Advanced Winner Eric Vigliuone PA 65 RE
2010 Jr. World Champion Winner Ryan Young PA 75 Merlin
2011 U.S. NATs Advaned Winner Ryan Young PA 75 Merlin
2011 U.S NATs Champion David Fitzgerald PA 75 Merlin
2011 Sr. U.S NATs Champion Ryan Young PA 75 Merlin

Sorry Brett I just could not help myself :-O

Randy

Brett Buck · « **Reply #23 on:** July 23, 2011, 10:56:11 AM »

Quote from: RandySmith on July 22, 2011, 03:49:02 PM

unbeatable

   Hmmm, how many of those were head-to-head against PW with a 40VF? We couldn't even beat him in '05 when it was 20-year-old supposedly "obsolete" technology.

   Believe me, I understand your point, and I don't run a VF any more, either, but so far we have had no answer for the original Impact with a VF, at least when it counted. I am quite amazed that you don't see the pits full of them even now, and even more amazing that the 95 NATs was not an Impact one-design contest. Just proves that the lemming effect is not as strong as you might expect and/or that no one really pays attention.

   Brett

rustler · « **Reply #24 on:** July 23, 2011, 02:10:13 PM »

For timing using tissue paper I reckon you'd only need to take the paper thickness into acount if it was totally rigid. As it is, a thin sliver when trapped at the top of the ports (gently!) will bend up into the cylinder slightly, thus minimising the thickness effect. With modern motors with a taper piston, even more so.
Might be interesting to get the paper in position and then shine the light, check any difference.

Andrew Tinsley · « **Reply #25 on:** July 23, 2011, 03:36:03 PM »

Hello Ian,
Managed to get round to repeating my measurements with both fag paper and al foil. First thing to say was I found the fag paper easier to use than the foil. Second point was there was no real difference between the measurements with the Led inside the cylinder and using the fag paper. Well the first engine I measured at 134 degrees came out as 134.5 and the other three engines were the same.
So I am no longer a believer in OS reproducibility. The four engines measured, actually spanned a range of 4 degrees difference in the exhaust timing. I now have complete confidence in the accuracy of my measurements (to within 0.5 degrees) and I do not believe there are any systematic errors in the measurements either.

Regards,

Andrew.

Peter Roberts · « **Reply #26 on:** July 23, 2011, 11:29:22 PM »

Out of interest I checked the exhaust timing on two LA46's that I have.. First engine purchased in 2001 exhaust 144 degrees transfer 116 degrees. Second engine purchased in 2006 exhaust 142 degrees transfer 118 degrees.
Comparing these figures to the ones that Andrew obtained it looks like there may have been a change in exhaust timing on more recent LA46's.

Peter.

Andrew Tinsley · « **Reply #27 on:** July 24, 2011, 06:47:36 AM »

I am confident of the figures that I obtained. I think the doubt I had was because other people were quoting 140 plus degrees. It certainly sounds as if OS did change the figures. 134 to 144 degrees is just a little too much to believe that it is simply a variation in the "manufacture" of the deck height.
Maybe this sort of variation is not uncommon. Taking two examples, the OS FP 40 seems to either run fine stock or requires some messing around to get it to run at all reliably. Same with the ST 51. People seem to find it either runs out of the box or is simply a pig. There must be some reason for this, apart from inept owners! If this sort of variation in timing is common then it could explain quite a lot that has puzzled me over the years.

Regards,

Andrew.

Steve Helmick · « **Reply #28 on:** July 30, 2011, 09:00:03 PM »

Andrew...Don't ever overlook the power of inept owners. Some can be given an exact setup...such as the legendary BBTU...and have problems. Detailed questioning will usually find that they've decided to use a different muffler, prop, fuel, venturi size or other component that is merely critical to making it work as prescribed. Hard to feel sympathetic, especially when they argue with you that it's close enough.

Steve