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Author Topic: OS 40 FP - set up Q's  (Read 2679 times)

Offline Vince Mankowski

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OS 40 FP - set up Q's
« on: August 14, 2007, 07:48:23 PM »
I have a few OS 40 fp's. All are converted r-c motors with OS venturi & OS nva installed.
First one was typical, (after break in) mounted & flown.....then various props later, I am using an 11-4 or 5. All my fuel  is approx 7 1/2 % nitro & 25% oil, from castor that I add to SIG Champion. FP lap times are a little zippy, and at the end of the tank, very quick for several laps. After fiddling with tanks (plastic uniflow seems the best) I decided -right or wrong- it's the motor that needs additional fiddling. By the way, I do not look forward to useing fuel mix "this" for this motor and fuel mix "that" for that motor. I have used this basic formula since the 50's. I still fly a Fox Black Head I bought in High School... same fuel, it works.

So anyway, I added a head shim to the 40fp. No big change, dropped a couple hundred rpm but still a run-away at the end of the tank. Same behavior, just a tad slower. Not any real added control over the motor rpm or the resident fp charastics.
I have found that a tongue muffler does not have enough volume, and the stock chamber runs better.

After reading some on-line stuff. I took a new 40fp and milled .020 off the top of the intake. By the way the boost ports are HUGE and operate very early! Then assembled with a head shim. OS shims seem to be .38mm (.015"), which seems like a lot, I was hoping for .005 or .010 increments.
With the intake raised and the (robust) head shim, my test stand rpm is 9500 with an 10 X 6EW cut down to 8 3/4. Pinch the fuel line & it quits. I can needle it to just under 10,000 but it is very touchy between running rich or not running. So, I removed the shim, and it runs just under 10,000 but quits on any suggestion of running faster.
I do have some sport stuff that I fly and an OS 40fp is great. But they love speeds of 69-75 mph, not the mid-50's.
My experience with the 35Fp is different. I can get a nice wet-two and no run-away, no needle sensitivy. Drop in the 40 & the 40fp characteristics are ll there.
Anyone have any better 40fp experience? If so, How'd ya do it?
Vince
Vince Mankowski

Offline Bob Hudak

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Re: OS 40 FP - set up Q's
« Reply #1 on: August 14, 2007, 08:11:28 PM »
Try doing a search in the box at the top right of this screen. This topic has been covered so much that you will find your answers in old posts. THE 40 fp in my opinion is a very tameable motor.
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Offline Jim Kraft

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Re: OS 40 FP - set up Q's
« Reply #2 on: August 14, 2007, 08:20:15 PM »
I don't know if you just raised the transfers or if you also raised the boost port. Anyway; Probably the best thing you can do at this stage is to block the boost port. My 40 FP's run pretty well after blocking the boost port, but run much better on profiles than upright or inverted. Some people seem to get them to run well either way so maybe they will chime in here.
Jim Kraft

Offline Mark Scarborough

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Re: OS 40 FP - set up Q's
« Reply #3 on: August 14, 2007, 09:07:17 PM »
My 40 FPs, well they can be a love hate cant they? I like mine, (until I was introduced to the LA 46!) Still love my FP, I run mostly a 11.5 x 4 APC prop with a .282 venturi and Supertigre needle assembly. Most of the time I end up using the stock mufffler but I open the stinger up. the biggest problem IMHO is that they are heat sensitive, If you let them heat they will run away. I do a minor mod to mine, I raise the top of the boost port and change the shape, then just mildly radius the edges of the ports . I fly typically at 2500 feet and in temps up  to 95. When loaded with enough prop and enough oil, I dont hardly ever have a problem. the stock .282 venturi seems to be on the upper limit, I have used several layers of panty hose over it to restrict it and it seems to mellow it a bit more. I launch at 9600 which is right on the crackling edge of going 2 stroke. Oh fuel, I use Powermaster 10-22 (11% synth and 11% castor)to which I add 6 oz of castor. Its what I use in all my motors EXCEPT Fox .35. Uniflow tanks no muffler pressure. I have had them in profiles and my Oriental, it seemed a touch more sensitive in the oriental but not unmanagable, on it I use a wood 11.25 X 4.5 that was cut from a 13 x5 so it has really wide blades and a touch of undercamber sanded in the back side. The blades are thinned significantly too. and it generally launches at a few hundred lower rpm but still crackling on the break. The only comment there is that I had a judge tell me it breaks to hard (?) As a side not, the older ones, distingueshed by having the case with the inset on it, as opposed to the flat side, seem to run just fine without any mods, something about the ports being different, it also has an iron piston I beleive I was told.
My experience FWIW, yours may vary,I have 8 of them and not enough planes to run them in, lol, cant build fast enough. Latest is my Vector that will be powered by n older FP40
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Offline Andrew Hathaway

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Re: OS 40 FP - set up Q's
« Reply #4 on: August 14, 2007, 09:25:22 PM »
I've got about 4 of the 40's and 5 35's and for a while they seemed to work ok until I really needed them to work.  About the most dependable attribute was that when it was an official flight they'd run 11 minutes.  After losing landing points, pattern points, etc at the majority of contests I was entering I finally gave up.  Everyone was saying how much better the LA works so I got one of them too.  It does the same thing.  There are so many solutions, tips, fixes, for making the 35/40fp work, it's pretty obvious that they don't.  They start easy, have plenty of power, last forever, etc but you never know when they're going to pick up the FP runaway. 

Offline Mark Scarborough

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Re: OS 40 FP - set up Q's
« Reply #5 on: August 14, 2007, 10:02:13 PM »
Andrew,
with all due respect, engines are a mechanical device, they will operate consistantly. If they perform differently it is because there is a variable that has not been accomodated, air temp, humidity, ect ect,, I dont beleive that if things were the same the engine would perform different. At least that is MY opinion. The .46 LA is a MUCH more docile engine. I think I was told because in teh process of making it larger displacement, they have much smaller ports (?) the LA 40 is basically an FP in a heavier case from what I am told, same porting ect.
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Offline Andrew Hathaway

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Re: OS 40 FP - set up Q's
« Reply #6 on: August 14, 2007, 10:33:52 PM »
The LA 40 just seems like a poorly made, less attractive FP.  It has all the same bad habits that the FP's have combined with a cheap plastic backplate, foreign fasteners, and a lackluster remote needle.  But that's not really the point.  The problem with the FP's are that they might run exactly the same way for flight after flight, nicely breaking from a 4 to a 2 and back to a 4, and then randomly without any warning they'd take off in a screaming two and never come back.  That 4oz of fuel that was consistently good for 7 minutes would run for 11.  The vinyl ama number and sometimes the dope would tear off the wing, etc.  Usually it happened at a contest when it really needed to work right.  I've tried more fixes then I could type here in the next hour, and none of them worked for long.  When many other engines work exactly how they're supposed to without fixing, the 35/40fp just aren't worth the trouble.  I don't run them anymore, so I'm not looking for anyone to provide me with a solution, just voicing my opinion.  There isn't anything that will fix their inherent flaws.

Offline Ward Van Duzer

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Re: OS 40 FP - set up Q's
« Reply #7 on: August 15, 2007, 09:28:10 AM »
Easy! Send them to Randy!

He'll preserve your horsepower, and give you a stunt run. Tell him how you want it to run, and you'll get it. I like a "high speed" run (without the runaway!) similar to pipe runs with low pitch props. But he'll give you a 4-2-4 run, if thats what you want. Most home made .40's I've seen give up lots of horsepower in order to make it "behave".


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Offline Vince Mankowski

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Re: OS 40 FP - set up Q's
« Reply #8 on: August 15, 2007, 05:44:12 PM »
I really appreciate the responses, both here & in emails. Thank you all.
I can sorta summarize..........
The 40fp run-away is real. Apparently some re-workers can tame that trait. There are even those that will give you choices between 2-4-2 and a constant wet-2 (apparently a timing and/or head change).

To those who suggested I do a search of an over-solved problem, I did. Some guys use an APC 10 1/2 X 4 1/2, & some use 12 X 6 woods (a power loading difference of almost 60%!). The fuel varieties and hot vs. cold plug advocates, venturi sizes, all vary. However, spray bar diameters were limited to just two. There is quite a collection of different opinions, but none with more then one vote.
However, a couple of guys noted the running difference between upright/inverted and side mounted.... which makes me wonder is this a volume flow/efficiency thang? (the Fox 35 crowd knows the drill)

I was really hoping someone had put a degree wheel to work and found some numbers, or worked squish bands, or piston draft below the wrist pin, Ve... something repeatable.

The best tip seemed to be the boost ports (they are HUGE, the "main" intake is miniscule in comparison). I will do that on both a "stock" sleeve and on the one I trimmed the top of the intake port .020.
If I follow with more, I may degree the engine and start noodling to see if the "stock" intake/exhaust openings & ports may be made more compliant.
Thanks again,
Vince Mankowski

Offline Kim Mortimore

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Re: OS 40 FP - set up Q's
« Reply #9 on: August 15, 2007, 05:56:27 PM »

I have been told that the LA.40 piston/cylinder is a drop-in fit replacement for the FP without the boost port.  Does anyone know if this is true?

If so, for those of us who have FP.40s lying around and want a quick fix for $29 + shipping from Tower, that might be the way to go.  If you enjoy experimenting and trying your hand at rework, then maybe not.

Kim Mortimore
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Offline Steve Helmick

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Re: OS 40 FP - set up Q's
« Reply #10 on: August 15, 2007, 06:24:05 PM »
One of the easiest setups for the FP's and LA's is to use the MACS muffer (#6650 fits the .35FP, .40FP/LA and .46LA). It can interfere with the LG on a profile, or the wing on an upright or inverted installation. There is said to be a #6652 that is better on a profile, tucks between the LG struts, but it's custom order from MACS. There's not much discount via Tower anyway, so it would be a good option, perhaps.

The setup is pretty simple, fuel economy is excellent, it runs 'one speed'. You need a tachometer, because you have to launch from 10k to 10.5k rpm, and you need about 1k more at peak, so you don't go lean overhead. The right prop is the key, and the known 'sekrit' prop WAS the Tornado black 10-4 3 blader, which may or may not be available. The 10.5 x 4.5 APC, 11-3 APC, 11-4 APC, or any other 11-4 you can find is fair game. Clip and carve to find a prop that works. There is a carbon/epoxy copy of the Tornado 10-4 3 blade, but I am not sure where to find them. I believe Mikey Pratt was involved?

A bunch of guys have run this basic setup here in the PNW and other areas, and all seemed happy. The "pipe" seems to regulate the rpm on the downstrokes (dives), the thing only weighs 2 oz, and it makes a nice carrying handle... LL~...after cooling down.... VD~  No muffler pressure, stock compression, normal venturi bore, uniflow tank, set by tach, plug & play...except for that prop! When you get this setup running right, it makes a funny rattle, like the wheels are going to fall off...they may, but if they don't, that just means your setup is working right.  :X Steve
 
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Re: OS 40 FP - set up Q's
« Reply #11 on: August 15, 2007, 08:16:59 PM »
Hi Vince. My family has had great luck with fp40's. My nephew Arch won the nats as a senior flying a 74oz 680 sq in plane with one. They do work very well. The only mod that has to made in my opinion is blocking the boost port. The port timing is fine as is. (cylinder liner timing is vastly over rated as an issue for stunt engines) The best p/c combo for max power  is the original steel design.  Early in the development process I noticed an issue that is fundimental to the design. With the twisted liner alignment the exhaust gasses impinge on the case casting and cause a "bind" when the engine begins to two stroke which I believe enhances the engines descent into the run away.. I decided with Big Art that we needed to machine the exhaust flange to clear the way for the exhaust gases. We used a special Big Art muffler that had an adaptor machined to match and picked up about a thousand rpm at peak to boot. We tried a lot of mods and found the biggest bang for the buck is filling the boost port. The combustion chamber is too shallow too. Try a short reach plug. and don't go beyond about .010 head clearence if you can. Don't load it up with a lot of oil. Oil lowers the octane of the fuel and causes detonation which can lead to heat. My nephews engines have never been run on more than 18%  pure ucon. fp's hate castor.......... We also use an assymetric combustion chamber which runs a cleaner four cycle. We use venturi dia's from .281 to .312 depending on the power required with St needles. Props have been easy: 11x6 Power Prop (no longer available) to very special: 10.5x5.25 Eather three blades. Uni-flo tanks with muffler pressure. K&B idle bar or Fox four cycle plugs. 10% nitro I can go on...

Offline Dennis Moritz

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Re: OS 40 FP - set up Q's
« Reply #12 on: August 15, 2007, 08:35:37 PM »
Many of us in our club, the Philly Flyers, run FP40s and FP35s.  Our basic system is a large venturi, one or two extra head gaskets, 10.5x4.5 apc, 22% (50/50) Powermaster 5%, free flowing tongue muffler. It's quite possible that the run-away you're experiencing is a function of vibration, frequently a problem with ARF Profiles. See the ARF section. I ran down the involved process of debugging a Primary Force ARF powered by an FP40. The soft nose caused inconsistent engine runs and run-aways. The engine behaving much like the ones described by Andrew. As we reduced vibration the engine ran better and more consistently. The engine now works extremely well. In this case an 11x5 Zinger wood prop also helped to tame the engine. At the Middlesex, NJ, contest last weekend I used the PF/FP40 in Intermediate. It had a crackling nasty 2x4 or 2x2 switch back in level flight powering up quickly when doing the tricks. The engine combo was as effective as any good running 40 at the contest including the plus $200 engines.

Jack Weston, Dan Banjok and Mike Palko (in the past, before he became ELECTRO-CUTE) have used and continue to use FP40s in competition. The combination of power and break is the equal of any non-piped engine we've seen.

Note: we set these engines by ear, not by tack. Sneaking up on the sweet needle opening click by click, going from a slightly over rich setting to one that works well in flight. Depending on the airplane, the engine may run richer or even slightly leaner on the ground than in the air. Allow the engine to heat up on the ground running for thirty seconds or so before making a final adjustment for flying. Observe engine as it goes through the pattern. Reset needle, if needed, on the basis of the flight performance. So, in other words, if a slight lean run on the ground meant a good flight setting, go with that. Or visa versa. Sometimes the ground setting and flight setting are very similar. Often they are not. I had a Twister that ran dead lean on the ground. After take off the prop would unload and the engine would settle into a crackling switch back break in level flight. Usually we run muffler pressure to a non-uniflo vent, which means the engine will lean out gradually, which is usually a positive, providing more boost for the high and overhead maneuvers. Uniflo can be problematic, depending upon the airframe. Some of our planes do quite well on uniflo. The needle setting will vary somewhat depending on temperature and air density, even varying during the day. Extreme heat usually means less O in the air making for a richer setting. High humidity also means less O. Denser cold air means a leaner run at the same needle opening. It's important to richen the mixture when this happens. Running an FP40 on the lean side is usually not the way to go. IC engines, even the big buck stunt specials, also need adjustment to suit air conditions. Final note, a good running FP usually has a harsher sound than the typical LA, Brodak or dedicated stunt engine.





« Last Edit: August 15, 2007, 11:10:34 PM by Dennis Moritz »

Offline Dennis Moritz

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Re: OS 40 FP - set up Q's
« Reply #13 on: August 15, 2007, 11:20:36 PM »
Interesting how the above three posts offer three different methods that proved successful.

Dave Adamisin

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Re: OS 40 FP - set up Q's
« Reply #14 on: August 15, 2007, 11:38:17 PM »
Absolutely Dennis. Three different solutions, three different needs, all filled with the same engine. The point is that you should learn to get the engine to do what you need it to do using the most repeatable and simple methodology.

Offline Bill Little

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Re: OS 40 FP - set up Q's
« Reply #15 on: August 16, 2007, 01:40:57 PM »
Absolutely Dennis. Three different solutions, three different needs, all filled with the same engine. The point is that you should learn to get the engine to do what you need it to do using the most repeatable and simple methodology.

Hi Dave,

I well remember the OS 40FP that Todd had on the Shameless Profile that he did a product review on for Flying Models.  That was the "oddest" looking muffler I ever saw! ;D  Coming off the engine at about a 45* angle towards the rear, but it made perfect sense!  A very sweet running engine that was definitely NOT down on power!
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Dave Adamisin

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Re: OS 40 FP - set up Q's
« Reply #16 on: August 16, 2007, 07:14:44 PM »
Great eyes Bill y1. The mod wasn't "necessary" but it did make a difference. That was also a steel p/c engine.

Online RandySmith

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Re: OS 40 FP - set up Q's
« Reply #17 on: August 16, 2007, 07:29:30 PM »
""My nephews engines have never been run on more than 18%  pure ucon. fp's hate castor.......... """


 ;D   HI  Dave   good  luck convincing  some  people of that   LOL     HB~> HB~> HB~>


Regards
Randy

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Re: OS 40 FP - set up Q's
« Reply #18 on: August 16, 2007, 07:32:09 PM »
""""The best tip seemed to be the boost ports (they are HUGE, the "main" intake is miniscule in comparison). I will do that on both a "stock" sleeve and on the one I trimmed the top of the intake port .020. ""'

HI Vince
The  2 intake ports  front and back are the main ports,  the one port across from the exhaust is the boost port, If you block any of these ports this would be the one to block, not the 2  main ports

Regards
Randy

Dave Adamisin

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Re: OS 40 FP - set up Q's
« Reply #19 on: August 16, 2007, 07:43:36 PM »
""My nephews engines have never been run on more than 18%  pure ucon. fp's hate castor.......... """


 ;D   HI  Dave   good  luck convincing  some  people of that   LOL     HB~> HB~> HB~>


Regards
Randy
Thanks for the tip ;D We tried ucon at the urgings of Harry Roe in the late 60's and have never looked back. We actually ran the oil content down to 12% for fuel economy when needed with no side effects. The strongest reason we had at the beginning (late 60's) was we were flying rat race and carrier as well as stunt. Castor had that old 30% nitro problem. You needed nitro benzene to get the castor to stay mixed with the nitro. This was not only dangerous it was a pain. No such problem with ucon or Klotz. Fuel problem solved and no more gunk loading up the racing engines.

Offline Kim Mortimore

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Re: OS 40 FP - set up Q's
« Reply #20 on: August 17, 2007, 11:17:49 AM »
""""The best tip seemed to be the boost ports (they are HUGE, the "main" intake is miniscule in comparison). I will do that on both a "stock" sleeve and on the one I trimmed the top of the intake port .020. ""'

HI Vince
The  2 intake ports  front and back are the main ports,  the one port across from the exhaust is the boost port, If you block any of these ports this would be the one to block, not the 2  main ports

Regards
Randy

Randy,
Do you know if the LA.40 piston/cylinder is a drop-in replacement for the FP, an alternative to blocking the boost port?

Thanks,
Kim Mortimore
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Offline L0U CRANE

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Re: OS 40 FP - set up Q's
« Reply #21 on: August 17, 2007, 11:31:25 PM »
Hey Vince!

Good to see you in here!

If you are into computer stuff, at least, into MS Excel, I might be able to help you some. I KNOW you can handle the machining.  After leaving Omaha in 1975, I got charmed by computers. Long story. Short answer: Using a good vernier caliper you can get to 1/5th of a degree accuracy for sleeve port timing. I've never been confident to +/-3 from a degree wheel...

I did a few Fox 35s while with the Orbiting Eagles, and worked out some spreadsheet-suitable formulae that paid off about 10 years later. ALL measurements needed come from lengths that a decent vernier caliper (~0.001 accuracy) can give you. NO slack from bearing slop...

The thing I developed started as a hand calculator nightmare - key the wrong number and it all goes blooey - and has settled into a current Excel spreadsheet.  You know me, I enjoyed translating it from one computer dialect to another...

I could attach my current version to an email to you, if you are equipped for that. My magic numbers for the Fox 35 were Exhaust Duration of 130, Bypass Duration of 120 - for use around 10,000 - 11,000 RPM. Fine torque, good economy, dependable 4-2 break, no burp, consistent needle, NO runaway. I've used the same approach to dial engines for different RPM bands...

Could prove useful for your 40FPs...
\BEST\LOU

Offline Air Ministry .

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Re: OS 40 FP - set up Q's
« Reply #22 on: November 30, 2019, 08:03:51 PM »
Just put these on to illustrate Dave Adamisins  post there .

Just purchased a Used ' Big Art & Sons " FP 40 .

Asked the bloke I got it from , if it was useless . He said " No, It was good " . Havnt flown , run , or whatever , as yet .

But couldnt avoid a look inside , for the ' Set Up ' . The HEAD plus the Blocked Boost passage .

The HEAD will interchange with the F S R 40 , despite the 35 degree offset , as its a ' Button ' set up . So can rotate infinately .

A few pictures then . Not Cleaned . Sorry . No wear . looks Good . A B C tho  apparently . Early case type .

Hopeing theres no offense , from the Adamisins , for releasing ' Trade Secrets ' . assuming not as out of production for some time .
They could in fact bathe in the glory of achivements , there . We Hope . Leeme know if you want the pictures removed if not so .


Offline Air Ministry .

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Re: OS 40 FP - set up Q's
« Reply #23 on: November 30, 2019, 08:14:36 PM »
Twomore .


Online Robert Zambelli

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Re: OS 40 FP - set up Q's
« Reply #24 on: December 02, 2019, 11:34:51 AM »
Am I missing something or is the head shown in the photos for a baffle piston engine?

Offline Air Ministry .

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Re: OS 40 FP - set up Q's
« Reply #25 on: December 02, 2019, 08:53:10 PM »
I hope not ! .

I assume its the ' assymetric ' head Dave Adamisin refers to , in his post previous here . ! .

Meant to do a picture of the piston crown , so you can see the ' flame pattern .' .

The scorch on the piston lid  S?P LL~ on most schnurles gets a line or patch , usually Ex Port side , initially .
Id think ' assymetric ' chambers would be rather usefull .

This Hers a SPUTHE head , of the same Era as the ' Lean Burn ' Raymond May V -12 H E JeeGuar heads ,
Notwithstanding it has valves & things ,


The principal of Squish , shock wave ' charge concentration & one or two other things , apply to Two Strokes equally . !

Will try it on My FSR too , as itll bolt straight on . Lean Burn on the wallet at the moment tho, after recent indulgances .  :-X


The 40 has the front of the rod ' X'ed , a .281 ! venturie .
Engine was super clean inside , but wrist pin super frozen . Needed heat to shift . Cleaned & oiled . Seems the pistons lightened too ,
out above the wrist pin lands , full circle .
« Last Edit: December 12, 2019, 08:01:49 PM by Air Ministry . »

Offline baum58

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Re: OS 40 FP - set up Q's
« Reply #26 on: December 10, 2019, 04:02:04 PM »
Hello to all,
I am new to control line (not new to model airplanes).
I did not want  have to fuss with engine setups or with linkage setups. I needed  all the help I could get. So I called the "Two Toms". Tom Dixon for  engines, Tom Morris for bellcranks and linkages.
Send your OS LA and FP  to Tom Dixon (Controline  Sales LLC) with $85 BUCKS he will modify it with a ventury, needle valve and small muffler. Use his setup. Perfect 4-2-4 run. Its a no brain-er. HB~> The same with the other Tom. I am building my first flapped stunter. I like the idea of adjustable linkages. Remenber, I am new to this. Now I can spend time to build a true and straight plane and have have a leg up on my learning curve  S?P

Peter

Offline Al Ferraro

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Re: OS 40 FP - set up Q's
« Reply #27 on: December 10, 2019, 07:11:16 PM »
I really appreciate the responses, both here & in emails. Thank you all.
I can sorta summarize..........
The 40fp run-away is real. Apparently some re-workers can tame that trait. There are even those that will give you choices between 2-4-2 and a constant wet-2 (apparently a timing and/or head change).

I was really hoping someone had put a degree wheel to work and found some numbers, or worked squish bands, or piston draft below the wrist pin, Ve... something repeatable.

The best tip seemed to be the boost ports (they are HUGE, the "main" intake is miniscule in comparison). I will do that on both a "stock" sleeve and on the one I trimmed the top of the intake port .020.
If I follow with more, I may degree the engine and start noodling to see if the "stock" intake/exhaust openings & ports may be made more compliant.
Thanks again,
I dove into the Tower 40 which is a clone of the FP 40, that I have mounted upright on Chief.  I could never get a good run with it in stock trim. My engine would runaway unless it was set to rich to do any maneuvers. Here are the numbers I came up with.
Crank opens 137 close 34
Exhaust 146
Intake side ports  118
Intake large boost port  90
The exhaust timing is close to the Brodak 40, and I like the way the Brodak 40 run in the planes I have, so I used its numbers on the intake, by carefully grinding the intake ports on the liner. My final numbers are.
Exhaust 146
Intake side ports 128
Intake large boost port 122
I now have a great 424 running engine using a APC 11.5x4 prop, Sig p2003 plug, PA .156 spaybar, .283 OS Venturi, Powermaster GMA 10/22 fuel. I also add a head shim to soften the break when it goes into a 2 stroke. I use a LA 40 muffler with the back half remove and the center baffle JB welded back and drill to except a .400 ID x 1 1/4 long aluminum  tube.
Brodak 40 new style numbers
Exhaust 144
Intake side 132
Intake boost 124
Crank opens 133 close 46
Al

« Last Edit: December 12, 2019, 09:32:02 PM by Al Ferraro »

Offline Geoff Goodworth

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Re: OS 40 FP - set up Q's
« Reply #28 on: December 12, 2019, 03:35:58 PM »
The venturi dia is important. The attached article from Stunt News years ago my be useful.

Back in the day, OS used to supply two venturis in the box for the FP 35 and FP 40. The smaller one is 6.75mm and the larger, 7.1mm. I've run FP 40s with the FP 20/25 venturi (6.55mm dia.) and I've reamed out the FP 20/25 venturi to 6.75mm because the 6.75mm dia part is no longer available.

These venturis are used with the OS NVA (3.5mm dia).

My best running FP 40 has the FP 20/25 venturi and a Bob Zambelli hemi head (see attached).

Online Robert Zambelli

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Re: OS 40 FP - set up Q's
« Reply #29 on: December 12, 2019, 09:20:40 PM »
Hi, Geoff.
The head mod you show was the first version as I recall.

I did some work on the squish band as show and it made a noticeable difference.
The break became a bit more gentle and more consistent consistent.

Bob Z.

Offline Air Ministry .

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Re: OS 40 FP - set up Q's
« Reply #30 on: December 14, 2019, 06:47:07 PM »
Told it'd been run on straight Cool Power Synthetic , 20 or 22 % , 10 5 Nitro .
Clean as a whistle in the bottom end . been stored for some years . dated 5 - 87 build . No 111

however the wrist pin was froze in the piston . The Heat Gun was a pre requisete  for freedom. or to extract the #*^! thing !
Clean & oil. includeing a twist of the 3M green scourer pad , thru the wrist pin holes in the piston , and the rod .
Came up bright & straight , no trouble . Though was securely ' glued ' with dry whatever lacquer .

The ' Big Art '  " X "  the rod front face - Big end , trick . and the Big Art bung the bypass trick . Both in appalling resolution .

This bit came out of in there somewhere . Will have to see if it goes o.k. without it . Or try & put it back in somewhere .  ;)


Offline Harold Brewer

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Re: OS 40 FP - set up Q's
« Reply #31 on: March 15, 2020, 12:58:32 PM »
I am planning on using an FP 40 in my kit bashed Top Flite Tutor (making it look like a P-51 C Mustang).  How long of a run can I expect on a 4 oz. fuel tank?

Thanks, Brew

Online Dan McEntee

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Re: OS 40 FP - set up Q's
« Reply #32 on: March 15, 2020, 02:05:09 PM »
I am planning on using an FP 40 in my kit bashed Top Flite Tutor (making it look like a P-51 C Mustang).  How long of a run can I expect on a 4 oz. fuel tank?

Thanks, Brew

   If you are running a reduced venturi as descried in this thread, plus a low pitch prop, 4 ounces will run a looooooong time, like probably in the 9 minute range in 70-80 degree temps and depending on your flying site altitude. A 4 ounce tank will be plenty,and you can always short tank it. Testing and timing each flight with the different fuel loads will tell you what you want to know.
   Type at you later,
    Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

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