Ram Jet

Darn, thanks for that photo. Saitos look like 1/9th of a Pratt Whitney Wasp.

Bill

Ram Jet

[sm=thumbs_up.gif]
I couldn't agree with you more. Like that?[sm=thumbs_up.gif] I think I get it now.

Cheers,
Bill

NM2K

My Feedback: (14)

What about the intake negative pressure that is being lost to the carb when a high pressure area (cam box) is inserted before the carburetor? Fuel draw is already barely adequate without bleeding off even more vacuum.

This is where a pump would come in handy and then the oil could be forced into the muffler's high pressure chamber without losing fuel draw, or even a low pressure collection chamber (bottle). It would be so easy to make a pump and sell it as an accessory that I'm surprised that someone hasn't thought of it before. Replace the drive washer with one that has been equipped with multiple cam lobes and have that drive a diaphragm to pump oil. Or go the geared oil pump route as with automotive oiling systems. Nice bit of third party created product to sell. Lots of folks would be tempted to buy one just for the brag factor.


Ed Cregger

Ram Jet

Interesting that you should mention a pump. I have been in touch with Perry Pumps about just this matter. Two of their pumps were recommended but I have too many projects to get into this experiment now. Vacuum loss in the intake tract? Adjustable by soldering the nipple hole in the fitting and starting with maybe a .025" numbered drill and adjusting from there. Any minute loss of vacuum can be compensated for by high and low needle adjustment.

Bill

proptop

My Feedback: (8)

Just to go back to this post for a minute...

If the passages (filed, cut, or cast in during manuf. ) in the lifter bores were of the right size/cross sectional area, the backplate vent (or wherever else it might be ) could be eliminated. The blow by oil would wash over the cam and lifters, then go up the pushrod tubes and then over the rockers and valve stems then out the rear of the valve cover(s ) to be dumped overboard or recycled PCV style.
FWIW though, I am not however a fan of diluting the fresh fuel/air charge with waste oil...nor causing a (albeit somewhat controlled ) vacuum leak.

The new O.S. 4 strokes do something along these lines I think, don't they? Maybe they read "Club Saito" about 4 years ago

NM2K

My Feedback: (14)

It just goes to show you, Proptop, that those original ideas that we think we have are mostly repititions of older conversations. There's nothing new under the Sun.

While in the Air Force, we had a retired government civilian mechanic, well into his eighties, that worked on our fire trucks. A few specialized vehicles (Crash Cardox trucks) were so old that no one knew how to fix them. Why? Because they did things differently, they had to. Many metal working machines and casting techniques hadn't been invented as yet when these old fire trucks were produced.

I used to buy him a soda and try to get him started talking. What a wonderful resource he was and he could surely tell some good stories. God bless you, Mr. Painter.


Ed Cregger

proptop

My Feedback: (8)

Quotes below by Bill Robison...curiosity made me go have a look in Club Saito...

"Two reasons for the move of the breather. First, it does force more lube to the cam shaft and tappets, but I think the main reason was going to the plastic back plate. If the breather nipple were in the plastic it would be relatively fragile."

"One of my experiments has the breather moved to the top of the cam box, from there to the exhaust rocker box and then across to the intake rocker box. Finally, the actual atmospheric vent is from the intake rocker box. Why? This forces the oil past the cam and tappets for better lubricatjon there, and ensures positive lubrication to the rockers and valve stems. This is mainly for upright engines, when they are inverted the rockers seem to get plenty of oil. Upright they are almost always dry."

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.





Hi Ed
I guess so, aye? It's good to have at least one person like that in our lives...[8D]
I had an instructor at A&P school named Mr. Hamm...he joined the Army Air Corps in 1933 and worked on everything from B-10's to P-80's...then 727's after getting out of the A.F. in the early 60's. He was an inspiration to me too.

I found the early post by Bill on pg. 7 of Club Saito...that started our conversation about doing it all internally, without the fuel tubing running up from the cam box...utilizing the pushrod tubes instead.

gkamysz

My Feedback: (19)

I don't know guys. OS introduced the car four strokes in 1999. These had the passages in the lifter bores, but nothing into the intake port.

proptop

My Feedback: (8)

I didn't know the O.S. 4 stroke car engines went back quite that far Greg...

Even still, with a sealed rocker cover, I wonder how effective the upper end lube was/is?
Those 4 stroke engines will turn waaayyy more r.p.m. than an airplane 4 stroke will, I know that, so valvetrain lubrication would be even more important.
If the top end of the motor is sealed, how much can actually get up there?

We have a rather famous (in the R/C car world...CRC Racing ) bunch of guys here in Rome, and I recall seeing a few of the .26's in buggies, and one .40 in a truck several years ago, but IIRC they had durability problems of one sort or another.
Next time I'm over there guess I'll have to ask what happened to the O.S. 4 strokes in this area.

http://www.teamcrc.com/crc/

FLAPHappy

My Feedback: (209)

If this error by Saito engines, they should re-disign the engines so they work properly. Saito engines are just about the best made, but if there is a problem with their design, they should fix it. Why should hobby people redesingn their engines for them? What worries me is ,if you make any modification to the engine, they won't repair it under warranty. So here we go.......They should work correctly right out of the box period. No modifaction, no new engineering, just make the engine work correctly.

42etus

My Feedback: (2)

I agree. One spends good money for the engine, he shouldn't have to re-engineer the thing. I do belive that this is a design error on Saito's part, but I doubt if they will admit to it. In the future, I am going to store all my Saito equipped planes in a nose down attitude, hanging from the tail feathers. My thinking is that oil in the crankcase will find it's way to the cam while the plane is hanging with the engine down.
Paul

Hobbsy

My Feedback: (102)

All this is much ado about nothing, I have at least 18 Saitos dating back from 1991 to two new .62s and have never had any issue with the cams getting lubed, I think w8ye can say the same. I have both front vented ones and rear vented ones and there is no difference in the way they run or their longevity.

w8ye

My Feedback: (16)

I feel the same way

proptop

My Feedback: (8)

Hey...I'm just thinking out loud here, so to speak. If it works for you, and iffn it ain't broke, then don't fix it

I was just having a flashback to a couple of conversations I had with a mutual friend of (several of ) ours here...

There seems to be a certain % of 4 stroke engines though, not only Saitos, that have dry valvetrains.

If you're a tinkerer like me, then... it might be a fun and interesting experiment. That's the way I look at it anyway, and if the engine is out of warranty, then......

w8ye

My Feedback: (16)

The last I looked, this was a hobby. And what do most hobbyist do?

Hobbsy

My Feedback: (102)

That is exactly what I did about a year ago. I drilled and tapped the cam box of my HighCompression Saito 150S and put a pressure tap on both sides. I ran a piece of fuel tubing from the back plate to the left side of the cam box and put a 3" long piece of tubing on the right to serve as a vent. My thinking was that oil would flow up from the backplate to the left side of the cam box and come out the other side. I was wrong, no oil flowed up from the back plate but all the oil came out of the right side of the cam box instead of out through the back plate. The meaning of all this. Plenty of oil can get to the cam area with no help from us.

If you look closely you can see the socket head screw blocking the tapped hole in the left side and a piece of tubing with a ball joint ball blocking the right side. I thought this cam was worn after 18 years of use but the new one is identical.

42etus

My Feedback: (2)

Hobbsy, I think your reasoning is flawed. With the back plate vent connected to the cam box, they would be under the same pressure at the same time. Hence nothing there to cause oil flow. I think you got oil flow out the right side vent because the back vent was effectively blocked and the right side vent was the only crankcase opening that was open to atmospheric pressure, so that's the path the oil took. That's close to the way it works in the engines with the forward vent. Bottom line is that you're getting oil to the cam area. I may make a similar mod to my Saitos once they're out of warranty, but 'till then Saito owns them.
Paul

Hobbsy

My Feedback: (102)

My reasoning is not flawed as I did not try to explain why it didn't flow up from the backplate vent, it just didn't. What I expected to happen didn't, that is all. However it was obvious that oil can get to the cam and as the 18 year old cam shows, it did.

42etus

My Feedback: (2)

Well I guess the bottom line is that most guys don't seem to have any problems, which is good. I do know two things though.

1. My first 115 had a failure that was due to lack of lubrication, even while using the recommended fuel.

2. My 2nd brand new 115 had absolutley no lube when shipped from the factory.

Either one or both could just be a fluke, who knows. All I know is from now on my Saitos are going to be stored hanging from the tail feathers, nose down.
Paul

42etus

My Feedback: (2)

BTW, I love your sig line. I chuckle every time I read it.

XJet

Just a word of warning about hanging your models nose-down.

If you're not using a good ARO then the somewhat acidic oil that gets blown past the piston ring will then do a wonderful job of corroding your bearings when you store engines this way.

I store all my models nose-up, I hang them from the prop on hooks placed on the walls of my hangar. That way, the corrosive combustion contaminated oil in the crankcase drains *away* from the bearings.

So long as you start the season with a good pre-lube (as I've previously described) then you don't have to worry about the oil draining out of the cambox or bearings during the flying season - well that's been my experience anyway.

Ram Jet

The rocker cover area is not really sealed, oil will migrate to the valve guides and tappets and surely escape there which I think is a good thing.

Bill

Ram Jet

With all due respect to any and all I think there is room for improvement on ANY of the four cycle engines on the market today with respect to crankshaft and valve train lubtication on four cycle model engines. I took ownership of a used Ebya .46 recently and tore it apart and saw no abnormal wear in the valve train. "If it ain't btoke, don't fix it." Who said that? Anyway, I guess I'm more of an engine tinker than a flyer. Being new to four cycle model engines maybe I'm coming into this arena with a fresh perspective. I will say that I'm darn glad that the engineers who designed the valve train on the auto and motorcycle I use for daily transportation gave significantly more thought to proper valve train and bottom end engine lubrication than model engine designers. Lubrication by piston ring blow by? Whew!

Bill

Ram Jet

Now you're talkin' my language.

Bill

Ram Jet

Right on!

Bill