NM2K

My Feedback: (14)

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If you wish to cause your four-stroke engine to backfire and lose the prop and nuts while flying, or if you want to burn it up and shorten its life way prematurely. change the prop to one with a higher loading without readjusting the needle valve.

I see so much of this behavior written today that it makes me wonder if there is some strange pride in doing such a thing? You should twist that needle valve every chance you get, until you become familiar with it and unafraid. On a glow engine, the needle valve, the size of the prop, how much nitro you are running in the fuel and the amount of cooling air available to the engine all control the engine's ignition timing.

Running with the timing too far advanced is what destroys glow engines, whether two or four-stroke. If they have a piston ring, the piston ring will lose tension and sometimes save the engine before any further damage is incurred. But I wouldn't count on this one to save your bacon.

I'm trying to help you out here, not embarrass you. Lots of folks are afraid to adjust needle valves for fear of losing their setting. The truth is, the setting changes each and every day and sometimes a couple of times during the day.

I'm on your side, honest Injun'. <G>

w8ye

My Feedback: (16)

Ed,

I was with Barry when he did the test stand run of his 72. He re-adjusted the HS needle with both props. I don't remember the RPM's though.

But your excellent statement of mixture re-adjustment for changing loads is good to have on record.

Enjoy,

Jim

William Robison

My Feedback: (3)

PL:

My FA-120 with the smaller rear bearing came with the ABC high compression cylinder and a "K" lug code. My FA-120 with the AAC cylinder (also with a "K" lug code) had the larger rear bearing. The one with the "E" code has the ABC cylinder and the large bearing. They have now been re-arranged, the AAC has the smaller bearing. This matches the two ABC engines, they are on my Cessna T-50 Bobcat, and currently are running counter-rotating.

I wont get into reversing rotation here beyond saying on that particular engine it's a trivial operation.
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Jerry:

From Boca you get a nice plastic package with a pretty printed label. From Paul at RC-Bearings you get a small zip lock bag with no label at all. I wouldn't be at all surprised to find that Boca's $80 ceramic sets are exactly the same bearings that Paul sells for $30, and made in the same factory in the same production run. In other words Boca is charging $50 for the package and label, in my opinion.

Ceramic advantage? With either steel or ceramic in place of worn bearings you will pick up a good gain in rpm, but the gain will immediately start falling. With ceramics the fall is MUCH slower than with steel, on the order of ten times slower.So the projected life of one $30 set of ceramics is equal (roughly) to $100 on steel bearings.

There's a long section in "Saito Notes" about bearing selection and life, I wont copy it here.

Bill.

Ernie Misner

Those Great Planes mounts are about as bulky and heavy, and ugly as they get, although the do work. If your model needs to save nose weight, try something like these Dave Brown or Hayes mounts at the LHS. Bring your engine with you and find a perfect fit.

http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Ernie

William Robison

My Feedback: (3)

Moon:

Quote:

ORIGINAL: moonmonster
Just one thing, discussing velocity stacks is banned! After the recommendations on here I have tried all over the UK to get two with no joy. The people who should stock them have either never heard of one being fitted or don't recommend one being fitted. Postage from the USA is $27.00 a bit too much for such a small inexpensive item

Have your LHS order part number SI50GK93 for you. Fits all Saito engines from the FA-50 up to the FA-125, except the FA-120.

In the USA the cost of the stack is low for the mid block engines, and not out of sight for the big blocks. There is no stack available for the FA-30 and FA-40, and some people in other parts of the world have trouble getting the ones that are on the market, as you said.

Guess it's time to get my tail in gear and finish the tutorial on making your own. At a much lower cost than even the mid block stacks.

Quote:

...but it would seem a sensible move by admin to give this thread it's own forum even although this is not manufacturer sponsored it could be in that forum... ...We should lobby admin somehow?

Moving into the "Support" forum brings an entirely different set of posting rules. the free and easy discussion we have here is not allowed there.

Moon, you may have noticed references to my "Saito Notes." It's mainly a compendium of my posts here and there, constantly being up dated. If you would like a copy send me your email address, can't send it through RCU.
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All:

If you want an update just ask, with your email address please. Also available for those who would like it is an Excel model for prop rpm, tip speeds, and estimated air speed at any given combination of rpm, pitch, and slippage.

Bill.

William Robison

My Feedback: (3)

New:

247 moonmonster
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Ed:

Good post on the mixture adjustment. Thanks.

Bill.

Flyboy1958

My Feedback: (1)

I have a question, not to change the subject. But I have a Saito 72 and the exhaust loosened up on me. Is there anything you guys do to keep it tight?

William Robison

My Feedback: (3)

Flyboy1958:

Loosening exhaust has been a constant problem for some, and no trouble at all for others.

I tighten mine while the engine is fully warm, and they stay. Hobbsy uses a couple turns of Teflon tape on his, and his stay tight.

So if you put a couple turns of Teflon on yours, and then tighten it while it's hot you should cure the problem.

Also, I've out you in as number 248. Welcome.

Bil.

BQuartucy

Bill R.
I would please like a copy of your excel program on props, slippage ,etc.
thanks in advance

Moderator removed the Email Address.

Kmot

My Feedback: (24)

Just thought of something for you guys who have exhaust nuts loosening. And any other nut/bolt for that matter.

Go buy an envelope of #53 drill bits. And a spool of .032 safety wire. And a "nut jig".

The jig aligns the nut and clamps it tight. The side of the jig has a hole for a #53 drill bit. It drills a hole in the very edge of the nut. Then afterwards, you can wire the nut so it cannot back off.

William Robison

My Feedback: (3)

BQuartucy:

PROP and instructions is on the way. Please go back and edit your post, remove your email address. Having it in the open is a big invitation to spammers. That's why I ask the address in a PM or email.

Bill.

William Robison

My Feedback: (3)

Tom:

I had forgotten all about those things. Please post a source, I'd like to get another.

Bill.

w8ye

My Feedback: (16)

Safety wire drill jig

http://www.eastwoodco.com/shopping/p...&keyword=11262

http://www.irvansmith.com/catalog2/p...ety_wire.shtml

http://www.aircraftspruce.com/catalo...rillingjig.php

Technique

http://www.sportrider.com/tech/146_0002_hand/

A nice $21.95 jig

http://www.skygeek.com/mt001.html

http://www.skygeek.com/mt002.html

William Robison

My Feedback: (3)

Thanks, Jim.

The Irvan-Smith site shows a plier for $30 that looks exactly like the pair I paid $85 for off the Matco tool truck.

Oh well.

Bill.

w8ye

My Feedback: (16)

The hex jobs drill across the corner of two flats

The Allen bolt jobs drill through the center of the head.

Safety wire is not very effective unless installed corectly.

enjoy,

Jim

blw

My Feedback: (3)

Ed,

I have no problems with adjusting needle valves, so I think you are getting the wrong idea from that post. I made that observation of the HS settings to convey that the engine is now stable again and runs consistently over some span of time, different temps/humidity, and with several props. If you had read about the .72 backplate issues causing the engines to run lean via the manifold leaks you would know that stability after a fix is a good sign.

Referring to the changing of props was to jostle Bill's memory of another post about a week ago on this engine, TNC tachs, etc.

I agree that some engines need closer attention than others. I usually look at my idle RPMs too for an indication. Lean and rich settings are things that do need attention, obviously. However, I disagree that all 4 strokes need needle twiddling after every flight. Case in point is my .56. Basically, set it and forget it. Yes, I know about lean conditions, etc. Thanks for the help.

Jim, I didn't adjust the needle valves when we bench ran the engine. We just fired it up and checked how it ran. The same setting didn't run lean the other day at the field when flying. I had the suspicion that I was a couple of clicks too rich later in the day, but I left the engine alone.

William Robison

My Feedback: (3)

Jim:

Been doing it for a long time.

I have been intending to ask: is that AirKnocker in your avatar yours? It's a 7AC?

Bill.

William Robison

My Feedback: (3)

Ed AND Barry;

When you have played with a particular engine for a while you know whether it needs needle diddling or not. Barry's FA-72 doesn't.

Bill.

w8ye

My Feedback: (16)

It's just a picture off the internet. But I learned to solo in 7AC's identical same color to it at Auburn University in the early 60's. I got my flight instructor's rating in a 7EC but it was white and red.
Flight report on a Champ
http://www.airbum.com/pireps/ClassicCompChamp.html
The in flight scene is identical in interior color and everything to the 7AC's I flew in except we didn't have radios. 2150 and 74 mph?

One of these days I'm going to build a model like this. There was one at Mac Hodges' 2 years ago in April but I don't know the source of the plans.

I have a Robinhood 80 that flies like one except the Robinhood has more adverse yaw. It is over powered with a OS 91 Surpass of all engines.

Here's another scene of a 7AC turning near your house....

Kmot

My Feedback: (24)

w8ye must have money to burn!

Here is a nut jig for $22 bucks:

http://www.pitposse.com/nutdrilljig.html

Here is a blurb on the proper way to wire with illustrations that looks like it was snatched right out of AC 65-13:

http://www.whizwheels.com/Tips/safetywiring.html

William Robison

My Feedback: (3)

Jim:

Your pictures and numbers bring back memories. I don't remember even seeing a Champ for 50 years or so. Everybody sees a Citabria now and then, but few believe it's the great-grandson of the 7AC.

ALL the Champs had the red flare on the fuselage with the overall yellow color, that's the fast way we had to tell they weren't Piper Cubs. Haw.

Bill.

spec36

looks like the picture on my wall [img][/img]

spec36

thanks for the help on mixture on the 72 I ended up at 1 1/2 and did not mess with the low speed yet but most of my fly time is under 1/2 power so i will work on the low speed next thanks again it helped





245#

powerlines

Do you guys EVER sleep. We are sitting around a fire on the patio in the back yard.. I got the 125. Had to get a gold knight. It will be in the Funtana cowl so it won't be seen. That is sad. I would like to put it on the Ultra Stick.. LOL.. Got that too. I will put the 100 on the stick and the 125 on the Tana.. That I can not wait to tinker with tomorrow!!

I just have to make my mind up on the 120 now that the 125 is ready. I may put it on the Four Star 60!! That would be AWESOME!!



LATER

krop

My Feedback: (19)

I have a SAITO 82A in my Goldberg Tiger-60 and it runs like a dream come true.
I recently purchased a SAITO 125 for a P-6E Hawk that I am building.
What else do I need to do to join your Club SAITO?