Author Topic: Brainstorming Question for Bob Reeves (Read 12566 times)

PatRobinson · « **on:** July 22, 2009, 01:41:54 PM »

Hi Bob,
In the August,2009 Model Aviation Joe Wagner had an article "Saito's Four-Stroke CL Engines". Joe added a 2" extension to the carb intake and indicated that it increased the engines prop turning ability by a couple hundred RPM.

It occured to me that if you threaded the end of the extension you could create an end cap that would serve the same engine run adjustment purpose as your nylon bolt. The advantage is that it would create a self-contained and very compact unit that would only require a hole in the fuselage or cowl to provide a means to fine adjust the engine run and also pick up a little more power.

So Bob, what do you think of this idea? I am not a machinist and I am not even sure who to ask to do this kind of work but it would be interesting to try.
Pat Robinson

Bob Reeves · « **Reply #1 on:** July 22, 2009, 02:38:12 PM »

Hi Pat,

Must have missed Joe's article, will have to check it out. (Hope I didn't just glance through that issue and put it in the round file like I normally do) If he was working with the CL version it wouldn't surprise me at all he was able to make more power. Anything one can do to help the engine draw fuel better will make more power and be more consistant.

I'm beginning to rethink the intake choke thing, I still firmly believe an adjustable choke is almost a necessity but starting to believe it would be best if the adjustment was at the spray bar instead of the intake. Adjusting the intake works but I believe it can be made better. This hasn't really been an issue with the larger engines as we are not asking them to preform to the max. I am asking a couple of 40's to give me all they got and the result is what prompted the below venturi thread. I believe if I can make the 40 better applying the same ideas to the larger engines will work just as well.

Anyway I haven't really addressed your question, can't quite visualize what you are describing but it sounds like it should work. Right now I'm in the middle of painting a durn old golf cart and pretty well devoting every spare second to getting it finished (bigger job than I thought). Next project after the cart is to look at Saito intakes and try a couple different ideas floating around in my head plus a couple given to me by others.

Bob Reeves · « **Reply #2 on:** July 24, 2009, 07:45:12 AM »

Almost have the Golf Cart finished and received the August MA yesterday..

Read Joe's article and have to say Hummmm... Hate to knock anyone's opinion but in my opinion I wouldn't put much faith in his conclusions. First off he was compairing the 56 on a Cardinal with a Brodak 40.. He should have put a 40a on the Cardinal. Putting a 56 on a Cardinal is like putting a ST 51 in a Nobler. Also he came to the conclusion a long intake extension is the way to go when he only tested it on one engine with a 12 inch prop under ideal conditions on an airplane that could be flown with a 40. The 56 will turn a 13 inch 6.5 pitch 3 blade and fly a 68 ounce <~700 sq inch stunt ship just fine.. Guess I'm just not sure what he proved if anything.

Brett Buck · « **Reply #3 on:** July 24, 2009, 11:00:46 PM »

Quote from: Bob Reeves on July 24, 2009, 07:45:12 AM

Almost have the Golf Cart finished and received the August MA yesterday..

Read Joe's article and have to say Hummmm... Hate to knock anyone's opinion but in my opinion I wouldn't put much faith in his conclusions. First off he was compairing the 56 on a Cardinal with a Brodak 40.. He should have put a 40a on the Cardinal. Putting a 56 on a Cardinal is like putting a ST 51 in a Nobler. Also he came to the conclusion a long intake extension is the way to go when he only tested it on one engine with a 12 inch prop under ideal conditions on an airplane that could be flown with a 40. The 56 will turn a 13 inch 6.5 pitch 3 blade and fly a 68 ounce <~700 sq inch stunt ship just fine.. Guess I'm just not sure what he proved if anything.

I read this too, and as I mentioned on SSW, it's a little strange.

However, I think there is some potential advantage of having a long intake stack (4-stroke or 2-stroke). I would be very surprised if it adds torque or power in a general case, although it probably does sometimes. But a long intake stack has one big advantage - it straightens the flow into the spraybar/sprinkler/spigot. That alone seems to help the consistency of the engine run tremendously. With the spraybar, etc. too near the intake end of the stack, it's too prone to changing the atomization and flow state right where it matters, thus changing the mixture and other run characteristics. I got much better results with the "long" version of the Jett venturi, and better still with a diffuser, just because the flow was more consistent during maneuvering. I think even better would be a plenum or airbox that isolated the spraybar even from the effects of external flow (like Sergei Belko's "bottom intake" engine where the fuselage formed a plenum over the "buried" intake.

4-strokes have this almost for free since the venturi is in the back, way down inside the cowl. A front-intake engine just sticks the venturi inlet right behind the prop in the worst possible place.

Brett

dave shirley jr · « **Reply #4 on:** July 25, 2009, 12:14:57 AM »

"Intake in the worst possible place"
especialy if you fly around bees!
in the other article on engines he noted that in stunt tuned pipes aren't worth the extra weight that they add.(not a direct quote but the general idea).
so i'm not sure he has seen a lot of current setups for stunt. the nats entrants seemed to have a few tuned pipes near the top of the results.
Dave jr.

Martin Quartim · « **Reply #5 on:** July 25, 2009, 09:21:34 AM »

The problem with the venturi in the back of the engine inside the cowl is that it picks up hot air. Most of us down here use a silicone tube, a trimmed exhaust extension, plug it in the venturi and route it to the outside of the fuselage to get fresh air.

I have thought about the air box before but haven't had the opportunity to make one the way I think it will supply fresh air without creating all sorts of pressure waves over the venturi entrance.

One day my friend was bench running a Saito 72 and I put my finger very close to the venturi to feel how fast air flows in and for my surprise I felt bursts of back flow. These burst indicates that waves of pressure is hitting the spray hole and I am wondering how that affects the dynamic of fuel flow. I thought about using a check valve near the NVA to see if that would help the fuel flow a bit more constant. Perhaps the restriction of the check valve could hurt more then it can help, if any. Perhaps some on with more time than me can better evaluate this.

Martin

RandySmith · « **Reply #6 on:** July 25, 2009, 11:18:13 AM »

I have done extensive testing on restrictor and venturie length's, A really tall venturie will result in a power loss,so you will just make it a larger diameter to get back the lost power.It acts smaller the longer you make them. One of the biggest problem is our front intake engines don't lend themsleves to really tall venturies and the airplane cowling at the front end interfere somewhat with them, if they get too long they get really close to the prop.
The best way to make them is to keep about a 3-4 to 1 ratio above the place the fuel enters..ie if you have a .200 hole you would want close to .600 to.800 inch above the fuel delivery hole, it doesn't hurt to have it a little longer. It doesn't have any big effect if the are 3-4.5 to 1 ratio, if it has to be a bit shorter you will not loose much but if it gets too short you can get a lot of fuel over the top , and may get inconsistant runs. Also in shorter restrictor type venturies the rubber Bru-line filters with there bell shape helps smooth the airflow and can make for a more consistant run if you have a short stack venturie.
Four strokes don't suffer from the pulse as much as 2 stroke do but they benefit greatly from anything you can do to help fuel suction,flow,delivery, I would like to try a side pickup ram-air type system with them, this would be an extension larger than the venturie that routed the venturie to the side bottom or top of the outside of the plane to pickup fresh air and keep a postive airflow. You could do this wil a piece of clear tubing or you could mold an extension piece to do this. I have recently bought a lot of RC car and heli intakes and filters, these are molded in many sizes and would be used to route the intakes to fresh air of the side or top, these are made in L shapes, U shapes and others, and could even work as an air box.

I have also tested air boxes with the conclusion of they don't do anything noticeable to improve run quality on my systems...two stroke engine.... This maybe because of the air pulse coming back thru from the engine from the bottom of the venturie back out of the top.
One thing I used I did like was a extention of clear tygon tubing slipped over the outside of the venturie and routed around the side of the engine to pickup air from the side of the airframe. This stopped the fuel from leaking over the front of the engine from the waves coming out of the short venturie I had to run in that particular plane. Sometimes if you run a pipe short it will pump fuel over the top of the venturie.
The best setup of induction I have seen or tested is a true venturie with proper angles and curves, and the fuel delivery holes top.(the top edge of the hole), just at the point where the smallest diameter is cut to angle out the other direction of around 14 degrees, Note I am referring to a real venturie and NOT a venturie tube.
I have made and tested about every induction system you can think of, on many many engine types, with them using all of the induction systems, you can make most all of them work but a real true venturie (not a venturie tube) delivers the most power with added bonus of they prime much easier .

The comment about tuned pipes not adding their worth in weight in stuntships is laughable,and is based on total ignorance of the system. CF pipes will weigh from 1 to 2.2 ounces which is way lighter than most all stock mufflers even adding the weight of the header,and not much more than ultra light tube aftermarket mufflers, also they add weight much closer to the CG of the airframe than a heavy muffler hanging on the front of the ship. Pipe add so much better power delivery in bad conditions than a muffler ever could , Plus add the fact they are quieter and keep huge amounts of oil out of the flaps ,hinges, horns,elevators and off of the airframe in general, resulting in planes lasting much much longer than they would normally.

Regards
Randy

proparc · « **Reply #7 on:** July 25, 2009, 07:41:21 PM »

There was a very long and in-depth thread in the RC forums concerning "velocity stacks" in four strokes. As most of you know, Saito's used to come with long velocity stacks that looked just like the old stacks on early Ferarri's etc. The new OS Max four strokes also now have them.

Most of the RC cats felt that an injustice was done to them by Saito in eliminating the V stacks from their product line just to save a couple of bucks. Extensive testing was done on the Saito velocity stacks by their Saito RC guru and, the difference was found to be quite profound in one area, AND ONE AREA ONLY! The Saito velocity stack SIGNIFICANTLY decreases fuel consumption. No other change was found.

As a result of that study, and the low price of a Saito V stack, Horizon Hobbies became instantly back-ordered on Saito velocity stacks,(they still sell them as a part). I plan to pick up some V stacks for my Saito's in the near future. Now, just exactly how that velocity stack would effect a Saito CL version is something I would like to see,(or I plan to find out myself LOL). Just imagine one of these things on a Saito 40A CL. By the time you get through a gallon of fuel, you will be ready to take on the Chinese team!!!

Bob Reeves · « **Reply #8 on:** July 26, 2009, 04:53:22 AM »

Quote from: proparc on July 25, 2009, 07:41:21 PM

<snip> the difference was found to be quite profound in one area, AND ONE AREA ONLY! The Saito velocity stack SIGNIFICANTLY decreases fuel consumption. No other change was found.

Personally I'm not sure decreasing fuel consumption is necessarily a good thing as it also decreases the amount of oil being ran through the engine. Considering the way 4 strokes are lubed I want as much fuel running through it as it will take..

Fuel economy has never been a concern in my experiments and testing other than discovering a correlation between great fuel economy and crappy engine runs. My 56/62's use ~4 ounces and the 40's use a little less ~3.5 ounces. If I get over 7 minutes on this amount of fuel I also typically see what is commonly referred to as burn down. Sagging on top and slowing down in the sq8.

RandySmith · « **Reply #9 on:** July 26, 2009, 09:58:09 AM »

"Extensive testing was done on the Saito velocity stacks by their Saito RC guru and, the difference was found to be quite profound in one area, AND ONE AREA ONLY! The Saito velocity stack SIGNIFICANTLY decreases fuel consumption. No other change was found. "

If the above is true I would stay far away from the stacks, andf never think of using them

proparc · « **Reply #10 on:** July 26, 2009, 10:58:34 AM »

If the above is true I would stay far away from the stacks, andf never think of using them

[/quote]

If you are not comfortable with certain elements related to 4 strokes then, well you should avoid testing them. I for one, study everything I can about the motors going all the way back to the beginnings with Bob Zambelli. I can personally tell you that a former United States National stunt champion told me to my face that 4 strokes don't work in stunt,(yes its' true).

Of course that was before the Chinese and French and the Americans rocked and rolled with it. I have tried and or tested just about everything damn thing I can think of with my Saito's and have developed a body of knowledge that surprises even me!!

While my ST 46, which I purchased brand new and have had since I was 14 years old, still sets the standard for me for reliability and consistancy, my Saito's are pretty darn close. Most of what I have done to the motors I don't discuss, but I can tell you that they run they way they do because of an attitude and willingness to study everything I can about them and try it out. I do this because I personally feel that the Saito's are worth EVERY PENNY I spent on them, and that they are more than worth the time and effort to experiment.

RandySmith · « **Reply #11 on:** July 26, 2009, 11:12:22 AM »

Quote from: proparc on July 26, 2009, 10:58:34 AM

If the above is true I would stay far away from the stacks, andf never think of using them

If you are not comfortable with certain elements related to 4 strokes then, well you should avoid testing them. I for one, study everything I can about the motors going all the way back to the beginnings with Bob Zambelli. I can personally tell you that a former United States National stunt champion told me to my face that 4 strokes don't work in stunt,(yes its' true).

Of course that was before the Chinese and French and the Americans rocked and rolled with it. I have tried and or tested just about everything damn thing I can think of with my Saito's and have developed a body of knowledge that surprises even me!!

While my ST 46, which I purchased brand new and have had since I was 14 years old, still sets the standard for me for reliability and consistancy, my Saito's are pretty darn close. Most of what I have done to the motors I don't discuss, but I can tell you that they run they way they do because of an attitude and willingness to study everything I can about them and try it out. I do this because I personally feel that the Saito's are worth EVERY PENNY I spent on them, and that they are more than worth the time and effort to experiment.

Hi Milton

I am comfortable testing anything, 4 stroke not withstanding, I buy , sell, test and run 4 strokes so I am very familiar with them,however It seems you didn't;t get what I was saying, There is no good reason to try to decrease the fuel burn on a CL stunt setup on a 4 stroke that is already very very fuel efficient, All you will do is add to premature wear and push the burn down scenario closer .
If it IS TRUE that the ..ONLY..thing stacks do is reduce fuel burn what will you have to gain?
My statement had nothing to do with me not being comfortable or Chinese ,French ,ST 46s or anything else

Regards
Randy

Bob Reeves · « **Reply #12 on:** July 26, 2009, 02:51:57 PM »

Randy said what I was trying to, but did a much better job..

proparc · « **Reply #13 on:** July 27, 2009, 12:03:46 AM »

Quote from: RandySmith on July 26, 2009, 11:12:22 AM

Hi Milton

All you will do is add to premature wear and push the burn down scenario closer.

Regards
Randy

Explain

RandySmith · « **Reply #14 on:** July 27, 2009, 10:49:45 AM »

Quote from: proparc on July 27, 2009, 12:03:46 AM

Explain

In simple terms, you will have considerably less oil going into an engine that is lubricated to a point by "blow by"
less oil will result in more heat more friction, more wear, and this will get you closer to the edge of the 4 cycle going into a sagging lean mode. Using less fuel in an already very fuel efficient motor will result in a much more critical needle sensitivity to adjustments. It is easier, with many of the 4 stokes, to get a "proper" "steady" and "consistant" needle setting when your burning 4 ounces instead of 3 ounces of fuel

I think Bob has enough flights on 4 strokes to tell you what the burndown scenario is and how it makes for a critical engine run, and it is a good idea to stay away from it

Randy

proparc · « **Reply #15 on:** July 27, 2009, 12:41:37 PM »

This is the part in question that Saitos used to come with. This the part number and the cost is $6.75. It has gone up 75 cents. It is a stock part designed by and manufactured by Saito for Saito motors. You can go to the Horizon Hobbies site and confirm for yourself. I will tell you what the results are and whether they concur with your findings.

RandySmith · « **Reply #16 on:** July 27, 2009, 01:04:46 PM »

Quote from: proparc on July 27, 2009, 12:41:37 PM

This is the part in question that Saitos used to come with. This the part number and the cost is $6.75. It has gone up 75 cents. It is a stock part designed by and manufactured by Saito for Saito motors. You can go to the Horizon Hobbies site and confirm for yourself. I will tell you what the results are and whether they concur with your findings.

Hi Milton

I do not need to confirm that from Horizon, my statement had nothing to do with Horizon what they sell for or even what price or what I think they did. I was making a comment on this:

posted by Milton
"Extensive testing was done on the Saito velocity stacks by their Saito RC guru and, the difference was found to be quite profound in one area, AND ONE AREA ONLY! The Saito velocity stack SIGNIFICANTLY decreases fuel consumption. No other change was found. "

I never did any type of testing on this product, I was just telling you
my thoughts based on the conclusions that you posted. I think you will find my comments to be right on "if the testing you posted was correct.

Regards
Randy

Alan Hahn · « **Reply #17 on:** July 27, 2009, 01:12:59 PM »

Quote from: RandySmith on July 27, 2009, 10:49:45 AM

In simple terms, you will have considerably less oil going into an engine that is lubricated to a point by "blow by"
less oil will result in more heat more friction, more wear, and this will get you closer to the edge of the 4 cycle going into a sagging lean mode. Using less fuel in an already very fuel efficient motor will result in a much more critical needle sensitivity to adjustments. It is easier, with many of the 4 stokes, to get a "proper" "steady" and "consistant" needle setting when your burning 4 ounces instead of 3 ounces of fuel

I think Bob has enough flights on 4 strokes to tell you what the burndown scenario is and how it makes for a critical engine run, and it is a good idea to stay away from it

Randy

I really am not trying here to be argumentative, but here goes anyway.

The fact that 4-strokes are lubricated by blow-by makes me question the statement that they need a lot of fuel. Mainly because if there is oil already in the engine crankcase, then isn't the "blow-out" (through the breather) a function of how much oil is coming in and how much oil is already in the crankcase. If less oil is coming in via the blow bye, then not as much oil is being forced out. In other words, there is still a level of oil inside the internal guts of the engine.

I would also argue that CL is a tiny epsilon of the usage of 4 strokes, so one shouldn't completely dismiss what the RC guys are doing.

Now you certainly need a quantity of "starter" oil in the crankcase to begin with.

My impression, with my Saito 40A, was that it actually wasn't blowing a lot of oil out. I began to be concerned that perhaps the blow-by was somewhat lower than it had been in my older 4 stroke engines---like OS 40's, a Saito 80, and a Saito 30. The older ones just seemed to "bleed" oil all over the place from the bleeder. Anyway I thought it was a good idea to load up the engine with afterrun oil, and my impression was that it seemed happier (and more came out the bleeder).

Now to completely change subject to stacks, if the stack is improving the fuel economy of the engine, I can only conclude it is because the fuel is being mixed better with the air. What other reason is there??

And if the mixture is better, it would imply that the burning is making a hotter flame. Now I would be worried about the synthetic oil being consumed in the hotter combustion.

I can tell you, electric motors are a breeze compared to IC engines (2 or 4 stroke)!

proparc · « **Reply #18 on:** July 27, 2009, 01:25:28 PM »

Here are pictures of OS Max's new line of 4 strokes designed specifically to compete with Saito,(Saito is the market leader in 4 stroke motors). One of the selling lines is that "it comes with velocity stacks as standard". This is a direct jibe at Saito for removing their velocity stacks to save a couple of bucks,(that is why they did it).

RandySmith · « **Reply #19 on:** July 27, 2009, 01:51:37 PM »

Quote from: Alan Hahn on July 27, 2009, 01:12:59 PM

I really am not trying here to be argumentative, but here goes anyway.

The fact that 4-strokes are lubricated by blow-by makes me question the statement that they need a lot of fuel. Mainly because if there is oil already in the engine crankcase, then isn't the "blow-out" (through the breather) a function of how much oil is coming in and how much oil is already in the crankcase. If less oil is coming in via the blow bye, then not as much oil is being forced out. In other words, there is still a level of oil inside the internal guts of the engine.

You can question that statement all you want ,but I am convinced when you have a very small amount of oil lubing and cooling a motor ,reducing it to a even smaller amount is not the direction you want to go in

I would also argue that CL is a tiny epsilon of the usage of 4 strokes, so one shouldn't completely dismiss what the RC guys are doing.
I didn't see anyone dismmising the RC guys findings

Now you certainly need a quantity of "starter" oil in the crankcase to begin with.

My impression, with my Saito 40A, was that it actually wasn't blowing a lot of oil out. I began to be concerned that perhaps the blow-by was somewhat lower than it had been in my older 4 stroke engines---like OS 40's, a Saito 80, and a Saito 30. The older ones just seemed to "bleed" oil all over the place from the bleeder. Anyway I thought it was a good idea to load up the engine with afterrun oil, and my impression was that it seemed happier (and more came out the bleeder).
so your statement of more oil in and more oil out made the engine seem happier??? see my statement I think you may find them to be more alike than your stating

Now to completely change subject to stacks, if the stack is improving the fuel economy of the engine, I can only conclude it is because the fuel is being mixed better with the air. What other reason is there??
Could be many more reasons, how about the taller the stack the more friction there is, and that makes the stack flow less air and act smaller, if the stack is tall enough to straighten the airflow, making it taller may do no good what so ever

And if the mixture is better, it would imply that the burning is making a hotter flame. Now I would be worried about the synthetic oil being consumed in the hotter combustion.
which again brings us closer to the burndown run many people get when running lean and using smaller amounts of fuel

I did not test the stacks, but I would think that if they saw better fuel milage, then I would assume that I would see a little less power and a leaner running engine, they may not have noticed this in a Throttle equipped engine

Regards
Randy

Bob Reeves · « **Reply #20 on:** July 27, 2009, 02:13:36 PM »

Durn it, had a big ole 4 paragraph post written then hit the wrong key.. Oh well Randy already explained most of it, was just trying to put it in a little different light. If you are still in the dark about burn down or oil I'll try to rewrite the thing. The more fuel thing may be a matter of opinion but burn down is real and observable.

Couple quick observations.. OS adding velocity stacks may very well be a marketing gimmick more than a performance decision. As we know RC users have a whole different prospective on what a good engine run is, most of what they do simply doesn't apply.

One question for Milton, you said "Most of what I have done to the motors I don't discuss". Why not? Most of us that run 4 strokes spill our guts every chance we get in hopes it might help someone and/or to get an idea we haven't tried or thought of. Can't imagine your reasoning...

Alan Hahn · « **Reply #21 on:** July 27, 2009, 02:44:05 PM »

Well,
I've never had a burn down, so I'm not sure what you guys are talking about. I am not even sure you know what you are talking about. I doubt that a "stack" causes a burn down.

If there is oil in the crankcase, then what I was saying is that you need only to replenish it, not flood it. It isn't like a 2 stroke that depends

Why is it that 4 strokes seem to bring out the mumbo jumbo? Every year there is a new mumbo jumbo.

I remember the comments about (from some years ago) about how cg didn't matter with heavy 4 strokes. "It turns like the nose weight doesn't matter"

Then standard tanks (no uniflows) and high rpms were the way to go.

The only constant seems to be that eventually the guru's go back to 2 strokes.

Now I actually like 4 strokes, but the mumbo jumbo is driving me crazy!

RandySmith · « **Reply #22 on:** July 27, 2009, 02:44:35 PM »

"If you are still in the dark about burn down or oil I'll try to rewrite the thing. The more fuel thing may be a matter of opinion but burn down is real and observable."

HI

My point I was making about this was that taking ..away.. fuel charge and oil , was ..not.. better than adding more fuel and oil , when your already dealing with very small amounts, it just looks like that is the wrong direction to go in

Randy

proparc · « **Reply #23 on:** July 27, 2009, 02:50:23 PM »

One question for Milton, you said "Most of what I have done to the motors I don't discuss". Why not? Most of us that run 4 strokes spill our guts every chance we get in hopes it might help someone and/or to get an idea we haven't tried or thought of. Can't imagine your reasoning...
[/quote]

A while back I posted pictures and text of work that I was doing with the original Saito 72,(later ones are different) - all HELL BROKE LOOSE. I don't post my work anymore. But, I did post pictures of the "Blown" Saito 72 in response to the comment I made that the RC boys were way ahead of us on 4 strokes. Those pictures settled the issue LOL.

I actually know quite a bit more about 4 strokes than I let on to but, most of what I post is on the RC forums. They tend to be a bit less uptight and hang-loose,( "I came in 10 feet off the deck inverted at 100 mph and I got confused and stuffed it", response "you are such an asshole", "response yeah I know I am").

PatRobinson · « **Reply #24 on:** July 27, 2009, 05:23:26 PM »

Hi Guys,

Wow!!!

This thread has expanded far beyond my original question so I guess I will add a few more comments.

First: In fairness to Mr. Wagner the reason he extended his intake was to project through a profile fuselage so he could choke the engine for hand starting and not to change the engine run characteristics. However, he did say the engine picked up a couple hundred rpm and that is what I quoted.

Years ago I saw a free flight engine with a long intake and I asked a CL speed engine guy about it.
He said that if you want a 2-4 break a short intake like a Fox 35 is best but if you are running a one-speed type of engine run, using a longer intake may help improve the consistency of your needle setting capability. However he also said if you make the intake too long you will lose power just like Randy Smith said.

A 4-stroke engine doesn't have a 2-4 break so a longer intake may not hurt the engine run but it also may not help that much either. I just don't know.

Second: Bob Reeves questioned the validity of flight test results from Mr Wagner bolting a Saito 56 to a Brodak Cardinal & I agree. The 56-62-72 can haul big heavy Strega size planes with no effort at all so using a Cardinal profile for flight tests would yeild somewhat doubtful results. The mental visual of bolting a Tigre 46 to a 1/2A Pinto comes to my mind.

Third: Milton, The results that the RC guru you mentioned was for using an intake stack for a throttled application but when you are using a non-throttled control line stunt application the guru's results may not apply or be true.
The best than can be said is that the result of using an intake stack for stunt is an Uknown and Unproven outcome.
This is comparing apples to unknown oranges without further results so it is at this time a moot point. That is unless you have already done the testing because I just remembered you said you had done a lot of testing with 4-strokes so you may already have test results. If so please share your results.

Anyway,to illustrate my point that 4-stroke stunt setups may suprise you look at Bob Reeves. He used a screw to reduce the intake size and it increased fuel consumption and improved power an engine run which is counter-intuitive to what "should work", but it worked for him.

So Milton, I look forward to your results for using intake stacks on a stunt setup to see what you discover.
Does it use less fuel? Does it effect prop turning power? Does it effect the engine run ? or could you increase the oil content of the fuel to compensate for using less fuel? I am just getting started with a Saito 62 so I would be very curious about your results.

Fourth: I started this thread because I saw the possibility of creating a compact and self contained (meaning attached only to the engine and not the fuselage) way to provide adjustment to the engine run the way Bob Reeves has been doing. In addition I want to adjust it without removing a cowl so an intake extension could be useful to provide easy access.

Yes,I do know that several flyers have acheived good 4-stroke engine runs without using any adjustable feature. However,one of the best features of a pipe-setup is the ability to adjust the engine run for the conditions. So the idea of having more adjustability for my Saito appealed to me. Bob is looking at another way to adjust the run so see his thread on venturi configuration.

I do find Randy Smith's idea of a ram-air-itake intriguing. I wonder if you could make it adjustable?? Humm-mm?

Anyway, Thanks guys this has been a most interesting thread,

Pat Robinson

Bob Reeves · « **Reply #25 on:** July 27, 2009, 05:30:36 PM »

Quote from: RandySmith on July 27, 2009, 02:44:35 PM

"If you are still in the dark about burn down or oil I'll try to rewrite the thing. The more fuel thing may be a matter of opinion but burn down is real and observable."

HI

My point I was making about this was that taking ..away.. fuel charge and oil , was ..not.. better than adding more fuel and oil , when your already dealing with very small amounts, it just looks like that is the wrong direction to go in

Randy

I agree, in all of my testing with intakes I've found if it gets exceptional fuel mileage it also runs like crap. When it's right, the exhaust is smoking and it's burning fuel without the needle being set overly rich.

Willis Swindell · « **Reply #26 on:** July 27, 2009, 08:40:52 PM »

What Randy said about loosing fuel out the top of a short intake makes more of a difference then you would think. Aldrich did a strobe light test on venturies and the blow back was what looked like 1/2 0r 3/4 inch high. Most RC carbs lose a lot of fuel out the top. I think the tall venturies or extensions use all the blow by fuel, that is the reason for better fuel millage.
Willis

Bob Reeves · « **Reply #27 on:** July 28, 2009, 05:14:22 AM »

Quote from: proparc on July 27, 2009, 02:50:23 PM

One question for Milton, you said "Most of what I have done to the motors I don't discuss". Why not? Most of us that run 4 strokes spill our guts every chance we get in hopes it might help someone and/or to get an idea we haven't tried or thought of. Can't imagine your reasoning...

A while back I posted pictures and text of work that I was doing with the original Saito 72,(later ones are different) - all HELL BROKE LOOSE. I don't post my work anymore. But, I did post pictures of the "Blown" Saito 72 in response to the comment I made that the RC boys were way ahead of us on 4 strokes. Those pictures settled the issue LOL.

I actually know quite a bit more about 4 strokes than I let on to but, most of what I post is on the RC forums. They tend to be a bit less uptight and hang-loose,( "I came in 10 feet off the deck inverted at 100 mph and I got confused and stuffed it", response "you are such an asshole", "response yeah I know I am").

Understand what you are saying but you'll never convince me that one can apply anything from what the RC guys do to what we need out of our engines. Whole different ball game..

Think the real hard part of discussing this is defining in words what a "good" engine run actually is. I'll try to explain what I'm looking for and have mostly accomplished with my 4 strokes. If I miss anything I would like someone to tell me what it is...

First off I don't want the airplane slowing down in any maneuver or speeding up when it gets windy. I want it to be able to go vertically over the top into a 15+ MPH breeze (think vert and overhead eight) without loosing line tension and not be doing 80 at the bottom. I want it to run the same and use the same amount of fuel from 70 deg mornings to 95+ deg afternoons and I want to be able to go from Pennsylvania to Texas and not have to do any major changes to the set up. I want the engine to be reliable and consistent, I do typically carry a back-up engine but so far haven't needed it.

My 4 strokes are real close to meeting all these wants but it's taken me almost 3 years and many test flights to get here. I have a pretty good shop set up plus my shop is about 150 yards from our flying site. This makes it pretty easy to experiment.

If I ever get my poor Score back in operation it just so happens I have one of Saito's velocity stacks. It came on a 56 Golden knight that now has a UHP manifold so it isn't being used. After my findings with the 40 (see the other thread) I plan on applying this to a 56 by modifying an RC carb. This would make it pretty easy to try it with and without the velocity stack to see what the results actually are as it applies to our needs.

Now Bob get off this darn computer and get that Score back in the air.

Bob Reeves · « **Reply #28 on:** July 28, 2009, 05:27:39 AM »

Hi Pat, ya this thread kinda went off on several tangents but interesting discussion.

I still don't have allot of input on your idea as at this point I'm not sure if an extended intake is a good thing or not. Like I said above I need to get off my butt and get my Score back in the air so I'll have a test bed. Just don't have enough room in the fuselage of the Latency to do much experimenting. Besides it's working so well I'm half afraid to mess with it.

Stand by, some day I'll have some answers...

proparc · « **Reply #29 on:** July 28, 2009, 10:25:11 AM »

Quote from: Bob Reeves on July 28, 2009, 05:14:22 AM

"Understand what you are saying but you'll never convince me that one can apply anything from what the RC guys do to what we need out of our engines. Whole different ball game."

Four strokes were not developed for control line stunt. They were developed and manufactured specifically for the RC market and community-yet!!! Plastic tanks were not developed for the control line stunt crowd. They were developed and manufactured specifically for the RC market and community-yet!!! YS Helicopter fuel was developed for you, guessed it!! The OS Max 4 stroke plug seems to coming on even among the 2 stroke stunt crowd-thats a surprise. Composite radial engine mounts, (Great Planes, Kraft etc) were not developed for our needs, but there is a hell of a lot of Top Flite Scores out there with them. Somebody say Fox RC long in a Supertigre 46-oldey but goody. RC ball links means just what it says!!

I have driven plenty of motors in FULL RC configuration through the pattern with totally acceptable results. The one exception seems to be the remote backplate mounted needle valve setup seems to consistently suck. Apparently it sucks for them too as it seems the RC engine manufacturers are moving away from it. A lot of complaints on the RC forums about inconsistent runs-humm.

I am not aware of any Stunt specific electric powerplant being manufactured as of now. Virtually all of the electric CL stunt technology is being derived from RC specific applications. To my knowledge, I would see this as the most drastic or dramatic example of RC\stunt cross pollination that I am aware of.

"I have a pretty good shop set up plus my shop is about 150 yards from our flying site". Can I have permission to hate you?

john e. holliday · « **Reply #30 on:** July 29, 2009, 09:09:18 AM »

I have been to Bob's place and pictures have been on this forum. It is one beautiful site and one circle is on his neighbors property. I can see why he has the cushman modified to carry his stuff. It is a little distance from the shop to the main circle. If had a set up like his I would be out there now flying my Cardinette. Have not done much on getting the little 4S setup as it is running so sweet when I leave the needle alone. DOC Holliday

Bob Reeves · « **Reply #31 on:** July 29, 2009, 11:15:22 AM »

Quote from: proparc on July 28, 2009, 10:25:11 AM

Four strokes were not developed for control line stunt. They were developed and manufactured specifically for the RC market ................

Guess I didn't say it quite right.. Wasn't saying we couldn't make use of stuff made for RC what I was trying to say is 99% of setup and configuration info gained from RC simply doesn't apply to CL.

Ya you can hate me but all it takes is persistence in striving for your goal, a little luck and good friends. My wife spotted this place and we were lucky enough to catch the previous owner in need of money, we didn't have any and trying to finance bare land with only a shop building is pretty difficult. In step the friend with financing and we were able to put the deal together.

Dave Adamisin · « **Reply #32 on:** August 02, 2009, 07:28:52 PM »

Quote from: Willis Swindell on July 27, 2009, 08:40:52 PM

What Randy said about loosing fuel out the top of a short intake makes more of a difference then you would think. Aldrich did a strobe light test on venturies and the blow back was what looked like 1/2 0r 3/4 inch high. Most RC carbs lose a lot of fuel out the top. I think the tall venturies or extensions use all the blow by fuel, that is the reason for better fuel millage.
Willis

Bingo. We have a winner. Four strokes engines are big spit back artists. The intake cam doesn't close till ABDC. The piston on it's way back up pushes charge back out added to the fact that intake ports usually flow better backwards it's pretty straight forward. Same amount of fuel burned less spit out. This is a big issue on autos because this "stand off" fuel dilutes the air in the manifold plenum and pushes all the way back out to become an evep emissions issue. It also causes transient mixture problems as the throttle is opened and the plenum is cleared. We don't have plenums to fill so if the spit back charge isn't "trapped" in a long intake runner it just blows out. Or so I would guess.....

Bob Reeves · « **Reply #33 on:** August 03, 2009, 04:38:53 AM »

One would think if the engine is spitting back a significant amount of fuel we would have raw fuel in the cowl and on the fuselage (in the case of a profile). I haven't found this to be the case but you never know till you actually try it.

I just finished modifying a 56 carb for the big test and while I was at it documented the modification. Am going to write a step by step article and post on the Gluedobber's web site when I get it finished. Here is the completed carb and with a velocity stack.

Dennis Adamisin · « **Reply #34 on:** August 03, 2009, 08:17:30 AM »

Quote from: Bob Reeves on August 03, 2009, 04:38:53 AM

One would think if the engine is spitting back a significant amount of fuel we would have raw fuel in the cowl and on the fuselage (in the case of a profile). I haven't found this to be the case but you never know till you actually try it.

I just finished modifying a 56 carb for the big test and while I was at it documented the modification. Am going to write a step by step article and post on the Gluedobber's web site when I get it finished. Here is the completed carb and with a velocity stack.

Good point. And I wonder how your throttle screw plays into the picture? You'd think it would backpressure (restricting?) the "spitting" some what. Also your preference for side-mounting would orient the engine in such a way to counter-act the spitting.

Historically (don't know it this is still the case) Saito 4-strokes were known for being more powerful and somewhat less fuel efficient than OS's. Could be a combination of effects incuding different cam profiles and (possibly) different intake schemes?

Dave Adamisin · « **Reply #35 on:** August 03, 2009, 08:47:31 AM »

Quote from: Bob Reeves on August 03, 2009, 04:38:53 AM

One would think if the engine is spitting back a significant amount of fuel we would have raw fuel in the cowl and on the fuselage (in the case of a profile). I haven't found this to be the case but you never know till you actually try it.

I just finished modifying a 56 carb for the big test and while I was at it documented the modification. Am going to write a step by step article and post on the Gluedobber's web site when I get it finished. Here is the completed carb and with a velocity stack.

Hi Bob. I was just opining (sp?) that in that particular case that the increase in FE could have been caused by the trapping of fuel that was being lost before the extension and used the large 4 stroke analogy as a model for comparison. Any sudden change in area will have a simular effect. I was able to improve the FE on the Evo's by eliminating the taper on the bottom of the vent insert. The idea being that the sudden change in area along with the cross flow caused by the sharp edge would cause the liquid to fall out of the backflow and be available for the next cycle. It seems to work. Thanks for sharing your experience here.

Willis Swindell · « **Reply #36 on:** August 03, 2009, 09:23:47 AM »

Bob
Yes there is raw fuel especially on profiles but you have to look closely, it sort of mixes together. I was going to suggest that you taper your adjustment screw, that might help air flow? Oh yea here is some handy work this Sunday.
Willis

Bob Reeves · « **Reply #37 on:** August 03, 2009, 09:38:18 AM »

Dennis & Dave... Thank you for your input.. I'm a rank amateur compaired to you guys and really have no idea of what I'm doing other than knowing what I want in the way of how the darn thing runs. I just try things till it works, kinda like Bill Little's blind hog.

Could be wrong but I believe my 4 strokes will run with the best and are much better than most I've seen at contests. The experimenting I'm doing now is mostly just to see if it's possible to make them any better, even though I'm not real sure what "better" is, hopfully I'll know if I accomplish it.

Bob Reeves · « **Reply #38 on:** August 03, 2009, 09:41:27 AM »

Quote from: Willis Swindell on August 03, 2009, 09:23:47 AM

Bob
Yes there is raw fuel especially on profiles but you have to look closely, it sort of mixes together. I was going to suggest that you taper your adjustment screw, that might help air flow? Oh yea here is some handy work this Sunday.
Willis

Ouch! Which airplane?. From the looks of the engine the airplane must have been hurt bad. Sorry to see it..

Willis Swindell · « **Reply #39 on:** August 03, 2009, 10:44:06 AM »

Bob
The airplane sort of pancaked in from a hourglass onto soft grassy ground. We think the cylinder caught some tough crab grass. We found a streak of engine parts up to 10 feet in front of the Strega. The Strega belonged to Jim Welch. He has another one almost ready to go but has a decision to make about repairing the Saito.
Willis

Dave Adamisin · « **Reply #40 on:** August 03, 2009, 12:06:58 PM »

Quote from: Bob Reeves on August 03, 2009, 09:38:18 AM

Dennis & Dave... Thank you for your input.. I'm a rank amateur compaired to you guys and really have no idea of what I'm doing other than knowing what I want in the way of how the darn thing runs. I just try things till it works, kinda like Bill Little's blind hog.

Could be wrong but I believe my 4 strokes will run with the best and are much better than most I've seen at contests. The experimenting I'm doing now is mostly just to see if it's possible to make them any better, even though I'm not real sure what "better" is, hopfully I'll know if I accomplish it.

Well once the blind hog finds the acorns he can eat till the tree stops droppin em.. Bob I have a couple of Saito's I will be playing with for another reason for both stunt and rc. I was also going to play with the intake in a uhhhhh unique (I believe) way. What average cross sectional area do you end up with at the choke? Thanks. And by the way, we're all amatuers at least once.....

Bob Reeves · « **Reply #41 on:** August 03, 2009, 04:05:40 PM »

Hi Dave, Often wondered if I could calculate the resulting choke area of a working setup and simply make an intake with that area.

Problem is I'm not sure if it can be accurately calculated, the two big engines I have working at this time have screws straight down the throats and no way to see or measure exactly how much of the intake is closed off. I can see on the 40's that the 10-23 screw protrudes about 2/3rds into the intake but trying to figure the effective area of a threaded screw is more trouble than I wanted to tackle.

Once I get the above intake on an engine and get it all set I'll pull it off and shoot another picture. It might be easier to guesstimate as the 1/4-20 screw is almost the same OD as the ID of the intake hole with fewer threads for air to get around.

Dave Adamisin · « **Reply #42 on:** August 03, 2009, 07:03:45 PM »

Thanks Bob. I was just looking for a ballpark number. Would you guess that you use maybe halk the area of the stock intake? Once you get the choke set what is the range you work in? Like with a 13x6 do you usually use about a 1000 rpm range.

Bob Reeves · « **Reply #43 on:** August 03, 2009, 08:12:57 PM »

What might work would be to use the RC carb and see how much of the intake is closed off. Only 13-6 I've had work is a CF 3 blade, on the Score I was running a Rev-Up 13-7.5 that actually measured about a 7. With this prop on a 56 I was launching at around 81-8200. With the 3 blade CF 13-6 on a 62 I'm launching at around 83-8400. I say "Around" because I do the final tweaking for lap times and don't always note or remember the actual tach reading.

Dave Adamisin · « **Reply #44 on:** August 04, 2009, 11:02:49 AM »

Quote from: Bob Reeves on August 03, 2009, 08:12:57 PM

What might work would be to use the RC carb and see how much of the intake is closed off. Only 13-6 I've had work is a CF 3 blade, on the Score I was running a Rev-Up 13-7.5 that actually measured about a 7. With this prop on a 56 I was launching at around 81-8200. With the 3 blade CF 13-6 on a 62 I'm launching at around 83-8400. I say "Around" because I do the final tweaking for lap times and don't always note or remember the actual tach reading.

I think I have it. Thanks Bob.

Bob Reeves · « **Reply #45 on:** August 08, 2009, 11:38:08 AM »

OK some real test data...

Decided to break in my spare 62 and as I already had the modified carb thought I would run a couple tests after I had enough time on the engine to be able to remove the RC carb.. I use the RC carb to meet Saito's "keep it under 4 grand for the first 5 min" break in then usually run it at around 8 grand for a gallon or so..

Anyway after about 1/2 gallon I stuck on the modified carb above and the Rev-Up 13-7.5 I had been flying on the Score. Put in a couple ounces of YS 20-20 to give me enough time to get the choke screw and needle adjusted as if it were on the Score.. Couple clicks on the rich side of peak and turning right at 8 grand..

Let the tank run dry and put exactly one ounce of 20-20 in, started the engine checked to be sure it was still turning 8 grand and timed the run with a stop watch. I then installed the velocity stack being careful not to touch the needle or choke screw, put another ounce of fuel in and started it.

The results were..... Drum roll please.....

Absolutely no change in the RPM, at first I thought it gained a couple hundred but after a second it settled down right at the 8 grand it was running before. Without the velocity stack it ran for 1 minute 21 seconds with the velocity stack it ran for 1 minute 25 seconds, 4 seconds longer.

Before I installed the stack I stuck my finger under the intake and sure enough it came back a little wet which confirms fuel is being blown back out.. On 4 ounces the stack would increase the run time by about 16 seconds.. I didn't do the finger test with the stack in place and now wished I had.

This was my test stand findings now we will have to wait till I get something in the air to see if it makes any difference in the run..

Dave Adamisin · « **Reply #46 on:** August 08, 2009, 03:43:41 PM »

Thanks Bob. As a guy that spent 19 years in testing, I love real data. Makes my cockles swarm......

Chris Wilson · « **Reply #47 on:** May 05, 2011, 10:43:22 PM »

Quote from: Bob Reeves on August 03, 2009, 04:38:53 AM

One would think if the engine is spitting back a significant amount of fuel we would have raw fuel in the cowl and on the fuselage (in the case of a profile). I haven't found this to be the case but you never know till you actually try it.

I just finished modifying a 56 carb for the big test and while I was at it documented the modification. Am going to write a step by step article and post on the Gluedobber's web site when I get it finished. Here is the completed carb and with a velocity stack.

I can see that the nylon bolt used here would create a slight plenum chamber underneath of it and this is akin to something that I have seen in control line team racers - there is a theory that an expansion chamber under a spray bar will emulsify the fuel/air mixture all the better and at the same time limit the amount of fuel being thrown back.

Sorry for necromancing an old thread but I found all of this interesting and this is one of the slower types of forums for net traffic.

Thanks

Author Topic: Brainstorming Question for Bob Reeves (Read 12566 times)

Alan Hahn

Alan Hahn

Willis Swindell

Dave Adamisin

Dave Adamisin

Willis Swindell

Willis Swindell

Dave Adamisin

Dave Adamisin

Dave Adamisin

Dave Adamisin