SrTelemaster150

Yes, the "boxer" is smoother but it is more expensive & in a small displacement engine, the single throw twin would be a bit lighter & more compact W/O a severe penalty as far as smoothness.

It's a trade-off. Once displacement grows, the smoothness of the boxer twin becomes more relevant.

AeroFinn

Hi SrTele

With the winter weather still going on I ask myself if I should move to somewhere outside the Nordic Countries EU..Especially having spoken to my great uncle who lives in Solvang,CA. Well, to be honest I'm doing just fine where I live but I wouldn't mind having spring already.

But thanks for the offer in anyways!

Here's a picture of my "flying field" next to my house from a flying session a week ago. (Yeah, I know it's not a Saito..but stilla nice model & engine)

Artto

SrTelemaster150

Well, I'm just 13 miles from Canada eh?

Still snowing & still cold here too.

BTW: Nice engine. (& plane) Is that a Laser?

Cougar429

My Feedback: (3)

Well, I'm IN CANADA!

Love it here, but it would be nice to be able to fire up my Saitos and fly comfortably more than 3-4 months of the year. If anyone follows radar it seems every weather system in North America is funneled through the Great Lakes, (and over our field).

AeroFinn

Yes, It's a laser 240v that I'm running in.
So we are in the same bout then what comes to waiting for the spring, then..
I hope to get my FA-125a rebuilt and run in within the caming two or three weeks and then convert it to the CDI with the CDI module I ordered from CH Ignitions. It's easier to be patient and carfull now than when the summer season has started..

hsukaria

Well, I have to say something since I am next door to Canada. Our Springs are terrible for flying here, too wet and too windy. It is better to fly in the winter when there is powdery snow than on fields that are soaked with melted snow or rain.

SrTelemaster150

You're a LOT further South than me!

I'm where the US/Canadian border crosses the St. Lawrence..

Ontario across the river, Quebec on this side.

hsukaria

Yeah, but he's got easier access to Canadian beer!!

AeroFinn

I would be very happy to visit Canada. I have been to US twice but never visited Canada. A friend of mine who lived in Finland, Turku now lives in Toronto. He's shown me picures on where he lives and from what I can say the landscape with lakes looked very much similar to what we have here. I do think the climate must be nice in Toronto woth relatively hot summers & and not too cold winters (compared to Sascatchewan, for instance)

Cougar429

My Feedback: (3)

Sometimes wish that were true, but neither the wife or I drink except for a glass of wine at Christmas.

The problem is the moisture. I've worked up in the bush, (personal record -56F) and the same -20F feels much colder down here in the "Banana Belt".

I think it's that same moisture I try so hard to keep from rotting the insides of my engines.

Hobbsy

My Feedback: (102)

One would think the boxer to be smoother but the reality is that it isn't, the 1.30 and the 1.82 are very smooth.

SrTelemaster150

You should see where I live. I thought you might like to see our version of "Nirdic Skiing".

This bulk of this clip was taken about 32 miles (50 Km) from my place in the foothills of the Adirondac Mountains.

Click on the image to start the clip..

SrTelemaster150

From "The Complete Saito Notes by Bill Robison".

Vibration, singles and twins, causes and comparisons.

The Saito twins with dual cam shafts have, lacking only a second crank shaft, twice as many moving parts as the equivalent size single cylinder engine. As a result they also have almost twice the friction losses. Seventy to seventy-five percent power of the single is s good approximation.

There are two classes of Saito twins, the even fire, and the odd fire. The even fire engines have one firing point every 360 degrees of crank rotation, the odd fire engines will fire one cylinder, then after 180 degrees of rotation the second cylinder will fire, then there is 540 degrees of crank rotation before the first cylinder fires again. The different feel is obvious when turning the propeller, and looking from the top the odd fire engines have the cylinders directly across from each other, while the even fire engines have the cylinders slightly offset.

From an engineering standpoint the odd fire engine is easier and less expensive to manufacture, it has only one crank pin on the crankshaft, and uses a “Fork and Blade� assembly for the connecting rods. One rod has a much wider big end with a slot in the middle, the con rod for the opposite cylinder fits into the slot, both rods riding on the single crank pin. This also allows both con rods to be made in one piece, no bolted joint in the big end.

The even fire twins have two throws on the crank, with one con rod on each. There are several ways to assemble the crank and rods for this type. Using one piece rods the crank can be built up from several pieces with field service capability, several pieces supplied only as an assembled unit, or a one piece crank shaft with the rod big ends bolted together. Saito even fire engines use the bolted big ends.

Let’s compare the FA-91 single, the FA-90T odd fire twin, and the FA-90TS even fire twin.

FA-91 single. For reasons I wont get into here it is not possible to have a single cylinder engine fully balanced mechanically. The mechanical vibration can be minimized with a heavy crank shaft and flywheel, but this weight is not good in an aero engine, mechanical balance will always be a compromise. Also, since the engine is developing power (in a four stroke engine) only ¼ of its running time and coasting for the other ¾ of the time, there is a dynamic imbalance as well. The resultant vibration can not be eliminated, there will always be an amount of vibration we can’t get rid of.

FA-90T odd fire twin. The odd fire twins have both pistons going to the left, they stop, then both pistons go to the right, stop, and the cycle repeats. They are, from a mechanical balance standpoint, the same as a single cylinder engine. With the two power strokes overlapping the peak torque is less than the single cylinder equivalent, the dynamic imbalance is lessened.

FA-90TS twin. This is an example of the even fire engines. With both pistons going in opposite directions they each balance the other. The rotating parts can be brought to almost complete balance, the mechanical vibration is almost totally eliminated. With the power strokes evenly spaced the power-coast ratio is now 1:1. This basic design is the smoothest common model engine, but being more complex mechanically it’s more expensive to make.
Summary: If you can stand the weight (and price) of the larger twin for the equivalent power of the smaller single, the even fire twin is the best engine to use. The odd fire twin is a compromise for reasons stated.


From Clarence Lee's article on the FA182T.

Hobbsy

My Feedback: (102)

One more time, as I said

One would think the boxer to be smoother but the reality is that it isn't, the 1.30 and the 1.82 are very smooth

Bumble.bee78

My Feedback: (11)

Anyone interested in a Saito 180.  Practically new.  I don't think it had more than a gallon thru it.

SrTelemaster150

So Bill Robison & Clarence Lee are wrong?

Hobbsy

My Feedback: (102)

I just said that their experience was different than mine, that doesn't make anybody wrong except maybe in making it more important than it is.

w8ye

My Feedback: (16)

I have a 182T and it is smoother than a 180 single.

SrTelemaster150

That's exactly what both articles say, smoother than a similar displacement single yet not as smooth as a similar displacement opposed (boxer) twin.

hsukaria

Hobbsy, in your picture of the opposed twin, are those fuel pressure regulators that looki square?

Rudolph Hart

Lets have a group hug just about anything is smoother than my 220!

arthur sun

i am RCHelicopter enthusiasts,if you need heep,i think i could help you .

Hobbsy

My Feedback: (102)

H-man, those are Cline regulators, I just did that having a little fun however it worked really well. As an experiment I placed the fuel tank as far as I could at the back end of the bench and it didn't change a thing. The Cline regulator is relatively unheralded product that will cure any kind of tank placement problem. Its not adjustable so there is no learning curve beyond reading the instruction.

SrTelemaster150

Proper Valve Lash Settings For Saito Engines

There have been some heated discussions in the past about the proper valve lash settings for Saito engines. I have even been warned by the post moderators on this site that I was "arguing" when I tried to point out that most are adjusting the valves on their engines W/too much lash.

Many misread the .04mm as .004" and use the (included W/the engine) .1mm (.0039") gauge that is intended as a "no go" gauge to check for excess valve lash, to set the lash. If you use the .1mm gauge supplied W/the engine, you will be, in essence, setting your valve lash on the verge of being excessive.

Up until now, I have not found any text from a "Saito authority" to support my theory that minimal valve lash is the best way to go W/saito enginers since the cylinder will grow more than the pushrods/valvetrain, resulting in more lash as the engine warms up.

I found just such information from the very respected Bill Robison. His "Notes" are posted in a "sticky" @ the top of the "Glow Engines" forum index page.

The following is a cut & paste from "The Complete Saito Notes by Bill Robison" linked below.

http://www.rcuniverse.com/forum/fb.asp?m=5843163

Old and new cams

"...this engine has not been run in ten years." This could mean the engine was new ten years ago, or it could have been an older engine even then. The point here is that it could have an early or late type cam shaft in it.

The older one responds very well to a valve clearance setting of 0.0005" while the later should be set at 0.0015" lash.

If the engine's real age is at least fifteen years try the half thousandth setting. If it runs fine there keep it set there. If it doesn't run well or if you're not sure of the age then use one and one half thousandths clearance. In either case you wont hurt the engine with the tighter setting.

In any case the engine will run fine with the 0.0015" setting, even as much as 0.002" lash is OK, but you get better power with the tighter setting.

Feeler strip for valve adjust

Most feeler "Sets" other than the basic ones have a 0.0015" strip included. As you can see in the attached picture this is also 0.038 mm, just 0.002 mm under the desired minimum clearance for the late cam grind.


If you set the clearance to 0.0015" and then tighten the lock nut, there will be enough distortion of the adjuster screw threads to get you the 0.04 mm clearance.


TDC Again

If you are at TDC either of two conditions will hold, assuming the valve adjustment is reasonably close.

1) Both valves will be slightly open, this is TDC between exhaust and intake strokes, the cam is in the "Overlap" position.

2) Both valves will be fully shut, with clearance in the pushrod/rocker gear. This is TDC between compression and power strokes, and is the correct position for adjusting the valves. Both rockers should be free to wiggle a little bit at this point, and the free clearance between the rocker end and the top of the valve stem should be no more than 0.002" - as I said, this is where I use the 0.0005" setting.

Hope this makes it more clear.
More on ½ thousandth clearance
Decreasing the valve clearance increases the valve open time, similar to putting a hot cam in your car. It allows the engine to breathe more freely and develop more power, but the idle does sometimes get a little lumpy. So don't be surprised by a slight increase in idle roughness. Closing the lash doesn't give you that hot a cam, but it's hotter than it is with loose valves.

Now go down to 1/2 thousandth clearance and you'll get even more, the idle still wont be bad.

As I said, the folks who have tried my 1/2T lash don't want to go back.


Quieting ramps

Since my post of 4/11/04 I have profiled several different Saito cams. See attached chart. While I did it out of curiosity about the actual valve timing, the dial indicator showed me that some of the Saito cams also have "Quieting ramps" in their grind. It is a "Lump" in the lobe intended to take up the clearance in the valve train, it eliminates the hammering of the parts when the lash is adjusted correctly. The correct adjustment is the height of the quieting ramp. If the lash is too great the ramp wont take up all the clearance, if too tight the valve will open too soon.

Attached graph is typical quieting ramp, degrees of rotation to the right, amount of lobe lift is vertical.

The 1/2 thousandth lash adjustment is still the best for engines without the quieting ramp, engines with the quieting ramp will work best at 0.0015" to 0.002" clearance.

Mike:

It is very hard to maintain engine heat to check the difference in the valve lash between ambient and running temperatures, but the crude measurements I've been able to make indicate the Saito engine's clearance opens about 0.0005" while running. That's why I can use 0.0015" clearance with the 0.002" ramp height.

Finally, having found no consistency in later checks concerning the quieting ramps I no longer recommend the 0.0005" clearance setting. You (I) have to check each cam individually to see if it does or does not have the ramp. Without the ramp the best running is with the tight adjustment, but the 0.002" is safe with either. If you don't know, stay at 0.002" lash.

Note that Bill points out that valve lash INCREASES as the engine warms so any lash, no mater how minimal when the engine is cold is suffecient as it will open up as it warms.

Hobbsy

My Feedback: (102)

Hey OF, how about this for a group hug?