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Post by tperry2054 on Sept 27, 2004 16:18:43 GMT -7
Dan,
The engine is packed and should be in the mail tomorrow. If the USPS is to be believed you should have it by this weekend. The head and backplate are secured by socket head bolts and are really tight. Just a warning as I stripped my only 2mm hex wrench when attempting to remove them. It could be that someone used Loctite on them so you may have to use heat to remove them.
My address is on the label but please don't feel obligated to send me anything. If we ever meet a diet coke would make us even.
I lent one of my FP 20s to Steve Fitton to try. He had pretty good results with his FP 25 on a Tomahawk. We should have some results from him soon as to how it did.
Tight lines,
Tom Perry
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Post by tperry2054 on Sept 28, 2004 6:18:55 GMT -7
While we are on the subject of 20FPs
Dan,
Why don't you put the formula here so people don't have to go elsewhere to dig it out? What prop, NVA, venturi size, muffler etc. It might help for the folks here to know the background of your and BBs history on debugging this engine. It would also allow me to ask you some other questions, like... When the engine is too much power for a plane you install it on will a smaller venturi that allows less mixture work well and keep the engine in a happy run? If you try a smaller venturi do you reccomend a prop with less pitch? I hope you understand what I'm getting at.
I think it is important for all to know that the formula for a good running 20FP is solid and it is an excelent base to retire to when experimenting fails.
Tom
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Post by dirtydan on Sept 28, 2004 13:08:40 GMT -7
Tom, Good point on detailing 20FP setup. It just seemed self-evident to me in that there has been a lot of discussion on SSW, current and previous Stunt News where I slammed in copious amounts of information. However, should anyone want to go to the source, try www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=8202&forum=DCForumID1I *do not* suggest going beyond posting N.6; the whole deal got turned into a big fur ball and I was part of it. In any case, the recipe is quite easy: 1) Stock 20FP; 2) Stock O.S. NVA; 3) Stock 20FP venturi, .257 bore; 4) Bru-Line "fine" air filter; 5) Stock "E-2030" muffler; 6) Stock cone-shaped insert installed in muffler; 7) APC 9-4 prop; 8) Any good 10% fuel, I have used both SIG 10% Champion and SIG 10% with 25% all-castor; 9) Three- or four-ounce clunk tank, plumbed per supplied instructions; 10) Muffler pressure; 11) Ground settings of 11,200 to 11,400; 12) SIG Skyray 35, ARF Flite Streaks, Super Combat Streak and similar models are ideal--Ringmaster and like models fly too fast, use 15FP. While off and on there has been a certain amount of resistance to a setup with this much specificity, this is also what is **known** to work. If you absolutely insist, for example, on using a tongue muffler, for whatever reason, just as well blow off the whole concept. You'll only be wasting your time. On the other hand, if a flyer uses exact setup above, gaining some experience with it, feel free to change stuff around as now you will at least have a benchmark to use in evaluating improvements to the quality of the runs, i.e. speed regulation, the strong point of the 20FP. In a best-case situation all involved will learn quite a lot about proper Stunt runs, how it might be that PTG and others are having such superb results with the $70.00, *stock* Magnum 36XL. As to specific questions, there are some answers on a current SSW thread being tossed back and forth. Still, the 20FP likes to, indeed wants to, run in a certain rev range, just like piped engines. Brett says this is due to stock muffler functioning as a 1/4-wave pipe; I cannot confirm this from the theoretical side, but can definitely confirm it from the operational side. Noting that muffler/pipe cannot be "adjusted" in any meaningful way, if you've got too much power in my view limiting things with the air filter is about as far as I want to go. For example, were I to be flying a Ringmaster I would not even try to make the 20FP work, I'd just get a 15FP. By the way, I think Steve said he ran out of time to compare your 20 to his 25. From his description, and the reactions of others to him 25/Tomahawk combination, one can hardly blame him. Dan
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Post by dirtydan on Sept 28, 2004 13:22:19 GMT -7
While I do not think this fair, a friend sent an e-mail several days ago and I am dropping my answer to him off in this post. Fair or not, I have had some really interesting experiences with the 20FPs and one of the most interesting--not dealt with on any other forum--is included:
"Sounds like you're set. The only thing I have learned since first article and that in Sep/Oct Stunt News is to be a little suspect of bought-used 20FPs. I had one that started and ran nicely, but did not exhibit Goodness and Light run characteristics. New piston/cylinder set improved this drastically.
Check your APC for correctly drilled center hole. Easiest way to do this is to put 'em on a good balancer. If they are very far off, use better tools to check. I have whittled out a .375 rod (drill guide) with a .281 hole in center. All my 9-4s get drill guided plugged into rear of prop, are drilled to .281. Inserts fabricated from 9/32 tubing are used in prop to center it on prop shaft. A touch of thin CA helps.
A new motor will need at least three ounces, possibly more. After it is nicely run-in 2.75 ounces is about what I use. Well, actually I will use less, as my ideal is to get out there, do the pattern and land with only four or five laps to spare. In contests the judges like it, when practice flying I like it. It is cutting things a bit close, however.
Don't worry about the weight of your FS. My modded Skyray really is 34.5 ounces all-up, no fuel and 450 square inches. And as you will soon tire of hearing, I used model to win in Expert PA. In *very* serious and turbulent wind.
I do think your lines should at first be 60' center-to-center, especially if no leadout adjustment and using .015s. The lighter .012s are really nice on this sort of model, just not legal for contest work.
Fuel can be almost anything. Yes, including Kool-Aid fuels, although I like my engines too much to do this. I use SIG 10% Champion. Or the equivalent. SIG 10%, 25% castor is also good; a little more power, noticeably better fuel mileage. Yes, engine will become varnished eventually. Big deal. And as they run in a rich to medium two-stroke, this is much less of a concern than with a 4-2-4 O.S. 40FP, for example.
If I were to use SIG 10/25 for any length of time I would be sorely tempted to add 3% Klotz just to get the cleaning effect of this oil, probably increasing varnish-removal intervals from two years to three. As I said, no big deal...
Finally, I have noticed a pattern when I let people fly what we call my "demo" ARF FS. A lot of these folk are ones I wish to see flying Stunt. Their near universal reaction seems to be, "That's nice, really nice. But don't they all fly that way?" As in, don't all Stunt planes fly around at the same speed, no herky-jerky from breaking into a two-stroke, for example. I need another demo model! This one fitted with a 25FP or 25LA tuned to Old School way of thinking. The difference is stunning, but if all you're flying on a particular day is the 20FP the effects are not near as salient as I would like, although the ability to "see" them does come around eventually.
Experienced Stunt guys are a slightly different case, as with Neil Rogers who used the demo in Classic at VGMC contest in Vancouver, B.C. His reaction--not his words--was, "Well, of course it runs super. It's one of Dan's models and engines. Ever see him with an engine that was out of tune? I haven't!"
Neil missed it. No tricks, no hours spent fiddling. In fact, I arrived in Canada on Friday with the demo having a freshly rebuilt 20FP on the nose. I ran 5 or 6 3-ounce tanks through it on the ground that afternoon. Did not fly it.
Next day Neil expressed interest in using it, he had no Classic model. His single test flight was the *first* in-air run on the rebuilt engine, I set the needle, it was one click rich, an hour or so later he put up an official, it was perfect. Second official, ditto.
Honestly, to this day I don't think he gets it fully and completely, that he was using *exactly* what I say to use, that it was the equivalent to a brand-new engine on Friday that gave him such good runs on Saturday. All with no fiddling from me, other than going in a click on the needle."
Dan
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Post by eklee on Sept 28, 2004 20:21:53 GMT -7
Disclaimer: I am a rank beginner aiming to learn the pattern manuvers by following Brett's FP20 setup FS/Skyray combo.
The problem I had was that I could not get a stock E-2030 muffler w/ baffle cone insert for my FP 20s. From reading Brett's postings, the muffler with the cone insert is critical to the type of engine run that he is describing. The muffler/cone combo behaves like a 1/4 wave mini pipe.
Well, I speculated that the cone and its location is what's required to generate a 1/4 wave resonnance so I improvised with a washer (5 cents) with a 1/4 in. hole inserted in place of the cone. I went flying with my ARF FS FP20 combo and I observed a VERY noticable improvement in the consistancy the engine run with the washer baffle. With the washer in place, the engine run has a coarse "pipe-like" sound at certain rpm. I don't have a tech nor any pipe engine experience so my experience is purely "hearsay".
I can not compare my cheap mod to the engine run with the original cone but I will not run any of my FPs (20 & 25) without the washer insert anymore. I would love to try out a real cone insert to compare.
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Post by dirtydan on Sept 29, 2004 10:58:30 GMT -7
EKLee,
Yep, we don't get the full effect of 20FP/stock muffler without cone-shaped insert (baffle) installed.
Unfortunately, you are making me look a little silly as I just ordered a stock "E-2030" muffler, mainly to get the baffle as they are not sold separately. While I did not pay 20 bucks just for baffle, can indeed use muffler on a model and engine that is complete less muffler, I have been chastised.
Hmmm, I am assuming you installed what the hardware guys call a fender washer. Neat trick. However, I cannot analyze the changes this ought to make in how the engine runs. I'm fixin' to ask Brett to consider this.
Also going to take a muffler down to local hardware store, seeing what fits, giving it a try.
Great idea.
Dan
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Post by tperry2054 on Sept 29, 2004 11:26:15 GMT -7
Dan,
I don't have the muffler with the cone either. Thats one of the reasons I gave my engine to Steve to test. His 25 does. It looks as if I am going to have to obtain said muffler my self. Did you order yours through Tower?
I'll tell you one thing though, this will be the last one I buy just for the cone. I plan on manufacturing some cones after I have an example to work with. I bought the engine that is on its way to you cheap enough that even if it didn't work I would at least have a muffler with a cone. Wrong thinking, the cone wasn't in there dammit!
I did however save the shell and liberated the thrust washer and nut off off of it and it sounds as if you can make good use of the crankcase so it turned out to be worth it.
Tight Lines
Tom
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Post by dirtydan on Sept 29, 2004 13:31:39 GMT -7
Tom,
Yes, muffler/cone assembly ordered from Tower.
In the early days of fiddling with a 25FP I was told they didn't come with the cone, only 20FPs did. But mine had one, how else could I have come to run across one in my box? Of course I was too smart to use it, modifying an RSM tongue muffler to fit.
Tilt...!
While this probably won't help a bit, common practice with the RC Guys was to toss insert. No do doubt more of these pieces laying around in people's shops than usable 20FPs, if only we could figure out how to find them.
As we've got a contest coming up, I need mufflers. But when the season ends in a few weeks I will send you a cone for your edification.
The fender washer idea would seem to have merit, even if not as elegant as stock convergent cone. While I don't own any (yet), I seem to remember CL Stunt pipes are fitted with flat baffles. In appearance would look just like a fender washer, although (I assume) fabricated from CF.
I have mentioned this cheap and easy substution to Brett in recent e-mail. We'll see if he gets a chance to offer his opinion as to what can be expected.
Dan
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Post by StuntMaster on Sept 29, 2004 18:21:42 GMT -7
The pipes that I am most familiar with ones used on the 40 VFs.
The pipe is molded in two pieces with the baffle being inserted into the main body of the pipe, before the tail section and Stinger are added.
The baffle consists of a thin aluminum disk, with two relatively small holes drilled one next to the other.
In that particular application, it appears as if the only purpose for the baffle is to reflect the wave back up the pipe.
It sounds as if the fender washer idea is a good one and an afternoon's comparison flying should tell the tale one way or the other.
I would be interested to find out what Brett had to say about this!
BIGS
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Post by Brett Buck on Sept 29, 2004 21:12:24 GMT -7
Da Dirt noted this thread to me, so I am responding - but never fear, I will endeavor to keep this forum a Brett Buck-free zone....
As far as the fender washer goes; that's an interesting idea. I have been assuming that the primary reflecting surface is the tail cone of the muffler, not the "baffle cone". This may tend to contradict this.
However, when we were trying to debug the 25, we looked in the muffler, and hey, no cone like the 20! Got a "baffle cone" out of a different muffler, put it in the 25 muffler, problem solved - or so we thought until we flew it. It ran somewhat different, and sounded different - but the "homing in" feature was still there unchanged. From that, I concluded that the tail cone was the reflecting surface we were using. And it matched the 4th harmonic of the run RPM reasonably well, unlike the baffle cone distance.
I would also point out that the flat fender washer would be expected to return a *very sharp* tuning point. Probably too sharp to be used effectively. Same thing happened when I tried to run a standard pipe, with the baffle section cut out of it*. The steeper the cone (i.e. . larger included angle/the closer to a flat surface) it gets the "sharper" the reflection gets. Conical surfaces, presented with a sharp "crack" of the exhaust pulse, reflect the sound back at different times. The closest parts of the cone return it first, and the "peak" of the cone later. So a "crack" goes out, and a "thud" comes back as the reflection is smeared out over time. The longer the cone, the more smeared, and the shorter the cone, the less smeared. The more "smear" there is, the shorter the boost effect, but it will occur over a larger range of revs. A flat surface has maximum boost effect, but this occurs over such a short range of RPM that you can't effectively use it. The fender washer would likely have the same effect.
If it works well, by all means, use it. If it doesn't then try something else. But I suspect it's not because of a tuning effect.
Brett p.s. By the way, nice finally meeting you this weekend, BIGS!
*A standard Billy pipe has about a 30-35 degree cone half angle. I had a pipe that wouldn't work properly any more (sped up quite a bit during the flight, no matter where I set it, probably cost me a top 10 at the '95 NATs). But it had no external flaws, or leaks. I replaced the pipe with another ostensibly identical pipe, problem solved - the weekend AFTER the NATs. Since I didn't know what the problem was, I decided to cut it open and see it there was something else wrong. Sure enough, one of the baffles had come loose. How that caused my problem is still a mystery to me. But now I had a good front half, and a good back half, of a tuned pipe, and it looked a lot like the drawing in the Two-Stroke Tuner's Handbook, with similar recommended tail cone angles.
So I glued it back together, and set it to the right length (calculated based on Frank William's EGT measurements, the exhaust duration, etc.) and flew it. One, it was inconceivably loud. Two, it held the engine in extremely tight regulation in level flight and in the round manevuers. Any tight maneuver made it drop off severely and frequently quit, and in dives (like descending leg of the hourglass) it sounded and acted like someone had stuffed a potato in the exhaust. It was also almost completely immune to needle adjustments. No matter what you did, it would run the expected speed, even dead lean or almost quitting rich, until it burped once, then it would splutter to a halt.
I knew that Frank's no baffle pipe worked just fine (but was also really loud), but it had a much, much shallower tail cone. I made another tail cone and replaced the standard pipe cone with it. It was much more reasonable to deal with (although it was will really loud and fell apart in a few flights due to crappy worksmanship (guess I should have spent MORE than 10 minutes on that job)).
It's also well-known that the baffles in the regular Billy-style pipes returned multiple return waves. I think that the net effect of the baffles in the regular pipe is to cause some "smear" through a combination of damping and multiple return waves.
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Post by eklee on Sept 30, 2004 15:12:28 GMT -7
"but never fear, I will endeavor to keep this forum a Brett Buck-free zone...."
Brett I hope you are joking. Your participation will greatly contribute to the value of this forum.
Please do check in frequently.
Eric Lee
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Post by Brett Buck on Sept 30, 2004 20:02:17 GMT -7
"but never fear, I will endeavor to keep this forum a Brett Buck-free zone...." Brett I hope you are joking. Your participation will greatly contribute to the value of this forum. That's very nice of you to say, but I'm sure some of your board-mates wouldn't necessarily agree! That's fine with me. I have a pretty clear idea what I want to do by posting, and that definitely rubs some people the wrong way. I have enough outlets, and I don't want to stuff my presence down someone's throat. Brett
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Post by minnesotamodeler on Oct 1, 2004 7:34:43 GMT -7
Hey, if we can put up with Dirty Dan we can certainly tolerate you! Jump in with both feet... --Ray
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Post by TreeTopFlyer on Oct 1, 2004 8:47:15 GMT -7
Brett,
While I don't always agree with you, I always value your opinion. Say on.
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Post by dirtydan on Oct 1, 2004 12:53:15 GMT -7
Tom,
Your postal guy lied to you. The 20FP arrived yesterday. Many thanks! Look for something in return, probably ship next Monday.
However, your postal guy is not only a liar, he is a thief. That poor ol' 20 came in stripped! No thrust washer, no prop driver, no washer, no nut, no NVA, no venturi, not even a scrap carburetor.
Yes I know, as advertised...
Do not let owner previous to you work on your engines. Back door was ninety degrees off. Big end of rod has goat-roper knicks in it. And while no thread-locking compound was found, all fasteners appeared to have been installed with no lube whatsoever. One of the head screws was a *very* close call; I was just fixin' to reach for Dremel tool when I tried it one more time.
Also discovered why it apparently had decent compression: layers of crud on both psiton and cylinder.
Ah well, all is hardly lost. I now have some perfectly serviceable parts, none of which are particularly cheap to buy new.
Tell ya what I'm up to. Tom Morris asked me to find a 20FP for him, get it setup and/or rebuilt, sending it along to him. I said I would but that my first priority was in getting four good 'uns for myself, as soon as my back-ordered wrist pins come in, that will be a done deal.
So your engine will serve as the major donor piece for a 20FP for Mr. Morris, to whom we all owe one heck of a lot more than one inexpensive engine.
With the engine rebuilt, I'll fly it some just to be sure all is up to specification, gather up some props, tanks and so on, passing it all along to Tom.
So thanks a lot!
My best,
Dan
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Post by tperry2054 on Oct 1, 2004 13:39:59 GMT -7
Dan,
I didn't think it had compression worth a damn and that’s why I sent it to you instead of working on it. Possibly it may have started but run reliably? I doubt it. I saw your acute need of a crankcase, and thought, well I know that’s good and if the wrist pin were ok that would be a bonus for you.
The engine I sent you was a package deal from dabay and was basically a parts engine. As you astutely noticed, and got it right away, I kept some of the parts. I have another engine that had the thrust washer boogered with a set of pliers and I like the black color of the original nut and prop washer so I used them on yet another engine to replace perfectly functioning bright shiny hardware store replacements.
I really do have a trashed carb for you if you want it. And if you really wanted one I have a good carb. I also have a box of assorted carbs from other various engines. Dammit! I may be a packrat but at least I have some tradin' material for the RC guys.
I did find a lead on some muffler cones, I forget if it was you or someone else that mentioned they thought the RC guys threw them away. Whoever it was, GOOD HINT.
Do ya think Tom can handle that engine?
Tight lines,
Tom
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Post by dirtydan on Oct 1, 2004 15:43:17 GMT -7
Tom,
Engine arrived in the exact condition you stated; I was just trying to be funny.
It was indeed I who mentioned the RC guys just automatically toss the muffler insert. Sounds like it worked for you.
Thanks, but I do not need any more RC carbs...!
I don't know if Tom can handle a 20FP, but when he asked me about it, he was hot to trot. And thanks in large part to you he'll be taken care of quite soon.
Dan
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Post by Brett Buck on Oct 1, 2004 17:02:12 GMT -7
I did find a lead on some muffler cones, I forget if it was you or someone else that mentioned they thought the RC guys threw them away. Whoever it was, GOOD HINT. I would think that the fender washer, a big socket from a socket wrench set, some sort of punch, and a big hammer will make all the baffle cones you could ever need. Brett
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Post by tperry2054 on Oct 1, 2004 17:41:28 GMT -7
Thanks, but I do not need any more RC carbs...! I don't know if Tom can handle a 20FP, but when he asked me about it, he was hot to trot. And thanks in large part to you he'll be taken care of quite soon. Dan I was also trying to inject a little humor on both. You're the one that don't like the smileys ;D Wasn't kidding on the cones though, I called the dealer over on the other side of the water from me. He thinks he's got some. I'll go over and check this weekend. I ordered some stuff from him a while back and it came in this week. New subject; althogh I'm not as passionate on the MAX 30/35 S as you are on the 20FS, I do like them and have a batch of them. I have some that need rods and Leonard got his order in on them. So if any read this give them a check out. Hijacked the hell out of this thread didn't I? I do have an interest in getting some more 15 thru 30 FS though but am trying to get them on the cheap from flea markets, yard sales etc. I will keep an eye out for more junkers too though. What was it they used to say on the chicken nuggets ads, "parts is parts"? I already have more engines than I need. SWMBO tells me it is a sickness. I think shes right. Tight lines, Tom
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Post by fox4ever on Oct 1, 2004 18:32:29 GMT -7
I run a Magnum 25 on my Tomahawk and like it just fine. It runs like an electric motor, constant at all times an in any manuver. Its probably one of the most fun planes that I fly. ;D
Lee TGD
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