Author Topic: O.S. LA .46 RC to CL (Read 10489 times)

Chris Fretz · « **on:** February 22, 2016, 06:23:17 AM »

I have a .46 LA that is RC an I would like to get a CL venturi an needle valve assembly for it. I can only find 40Fps venturi 7mm an 40 Fps needle valve assembly on Ebay, I see a venturi an a spray bar only not the needle at Tower Hobbies. Any help on what I need an were to get it?

Dave_Trible · « **Reply #1 on:** February 22, 2016, 09:21:31 AM »

Scroll down to vendors corner here and find Lee's Machine Shop. Jim is the prime source for this stuff. He has converted dozens of RC engines for me alone.

Dave

Brett Buck · « **Reply #2 on:** February 22, 2016, 10:33:49 AM »

Quote from: Dave_Trible on February 22, 2016, 09:21:31 AM

Scroll down to vendors corner here and find Lee's Machine Shop. Jim is the prime source for this stuff. He has converted dozens of RC engines for me alone.

Dave

Make sure you get a venturi and spraybar conforming to the *stock parts*. Jim will fix you up.

Brett

Tim Wescott · « **Reply #3 on:** February 22, 2016, 10:52:46 AM »

If you want it to be "stock" 46LA then you'd get the 40FPS venturi, a "O.S. Nozzle 20-40FPS RN", and you'd use the stock rear needle valve.

Most people will use the "conventional" needle valve -- I think that the 25FPS works, but I don't know for sure, so don't go trusting me on this.

Opinion on the rear needle valves range from loathing to acceptance. Folks that loath them complain of uneven runs. I've found that if you don't have big bubbles in your fuel and you don't have any leaks between needle and spraybar (what Tower calls a "nozzle") then the only downside to the remote needle is that it's much easier for the fuel to break surface tension in the spraybar and empty the fuel line back to the tank. This can be overcome by learning to prime the engine just enough to start readily and run long enough to start pulling fuel again.

The main reason I like a remote needle valve is that with a bit of cleverness you can mount it more or less behind the cylinder and parallel with it. On a profile this protects it in the event of a crash -- if you're in the "always crashing" stage of learning to fly, this means that whenever you perpetrate an "unconventional landing" that's anywhere between straight down or upside down, then instead of worrying about needing to replace the needle valve, you just scrape off any moss or dirt and carry on.

Tim Wescott · « **Reply #4 on:** February 22, 2016, 10:59:56 AM »

Your other option, if the O-ring between carburetor and engine is in good shape, is to just nail the throttle down (you can use a pushrod to an engine screw, or to a screw behind the engine) and go fly.

Take this with a grain of salt: I've got one example and it runs fine. But Brett has a lot more experience than I do on this and says that it leads to uneven running.

My one example of this was put together with Brett's comments in mind, and I made sure to close up every avenue for air leaks in the carb to engine mounting that I could. I cleaned the carburetor thoroughly, I put a brand new O-ring between carburetor and engine, and I put gaskets between the carburetor boss and carburetor screws when I assembled the thing. At the moment it's the best-running "CL" engine I own (which isn't saying much -- all my engines are repurposed RC engines that I either bought used or which were given to me when I was simultaneously trying to get back into the sport with no equipment, and suffering from the recent economic woes).

Jim Svitko · « **Reply #5 on:** February 22, 2016, 12:40:18 PM »

If you prefer the conventional venturi-needle set up, Jim Lee probably has a venturi on hand for the LA 46. I don't know if he has the needle assembly. The OS needle assembly that I use is OS part number 22311000. "Shtterman" on e-bay might have some.

Some might say to also replace the plastic backplate, if it came with a plastic one, with a metal backplate. I have run the engine with both and can see no difference but some say the plastic distorts and causes leaks. Other than that, there is no need to do anything else to the engine to make it suitable for CL.

Tim Wescott · « **Reply #6 on:** February 22, 2016, 12:47:45 PM »

Quote from: Jim Svitko on February 22, 2016, 12:40:18 PM

The OS needle assembly that I use is OS part number 22311000. "Shtterman" on e-bay might have some.

Putting that number into the Tower Hobbies search bar pops up with the 20-25FS needle. I had dimly recalled it being the right one, but couldn't remember for sure.

Quote from: Jim Svitko on February 22, 2016, 12:40:18 PM

Some might say to also replace the plastic backplate, if it came with a plastic one, with a metal backplate. I have run the engine with both and can see no difference but some say the plastic distorts and causes leaks. Other than that, there is no need to do anything else to the engine to make it suitable for CL.

Any backplate will leak if you over-tighten it. "Over-tight" for a plastic backplate is just a lot less tight than for aluminum. I, too, have both aluminum and plastic backplates, and no problems with either. I've never taken one off, but the guidance on putting a plastic one on is to be gentle. If you feel like you're putting any effort at all into it, you've probably bent the thing.

Dane Martin · « **Reply #7 on:** February 22, 2016, 12:51:33 PM »

"Putting that number into the Tower Hobbies search bar pops up with the 20-25FS needle. I had dimly recalled it being the right one,"
That is the correct one. I have bought several for myself and club members. Goes up to 46 la.

I can get pics up in a few hours if anyone would like. I have at least one unopened. They're pretty versatile. In fact that's what i used to modify a UHP manifold to convert my Saito 72. I used an OS venturi and a 22311000 nva.

Jim Svitko · « **Reply #8 on:** February 22, 2016, 01:07:57 PM »

I kept the label from the needle assembly for future part number reference. The label for the needle assembly, OS part number 22311000, says "20-40FP-S". No mention that it will fit the LA 46 but it will fit and it works well.

Chris Fretz · « **Reply #9 on:** February 22, 2016, 03:00:51 PM »

Im new to Stunt Hanger an I already like it. Thanks for all the replys!

All the parts I have found wether needle valve or venturi's have the part number 22311000, just some of the parts say for 20,25 FP-S an some just say 40FP-S. Makes it look like two different sizes available.

I learned to fly CL from my dad in the late 80s into early 90s then for some reason stopped flying for 20yrs an got back into last year. We used Fox .35, Red Heads, an you guys will probably laugh but then we started using Testors series 21 McCoys. I loved those they would just keep going, heavy yes. Anyway all those engines would hit a point were you could hear them winding up when adjusting the needle. I was messing around with a LA 40 last year an adjusting the needle an it like the engine never wants to hit that peak wind up like Fox's or McCoys. This .46 LA I just ran the other day seems the same way (I am not running mufflers on any of them) Is it just me or is this how these LA's are?

Chris Fretz · « **Reply #10 on:** February 22, 2016, 03:03:54 PM »

Quote from: Tim Wescott on February 22, 2016, 12:47:45 PM

Any backplate will leak if you over-tighten it. "Over-tight" for a plastic backplate is just a lot less tight than for aluminum. I, too, have both aluminum and plastic backplates, and no problems with either. I've never taken one off, but the guidance on putting a plastic one on is to be gentle. If you feel like you're putting any effort at all into it, you've probably bent the thing.

Where do you get aluminum backplates?

Dane Martin · « **Reply #11 on:** February 22, 2016, 03:09:02 PM »

Quote from: #Liner on February 22, 2016, 03:00:51 PM

Im new to Stunt Hanger an I already like it. Thanks for all the replys!

All the parts I have found wether needle valve or venturi's have the part number 22311000, just some of the parts say for 20,25 FP-S an some just say 40FP-S.

There are different sizes of venturi available. Right now there are probably only 2 available, but there were three. The outer diameter that fits into the engine intake is the same whether it's a 25,40 or 46. So there's some adjustability there

Tim Wescott · « **Reply #12 on:** February 22, 2016, 03:27:43 PM »

I've seen a lot of people recommend using the 25FP venturi on the 46LA. This may not be a bad thing.

However, my preference is to put layers of pantyhose over the venturi to effectively decrease it's diameter. I like this method for three reasons: one, I can easily tune it in the field, to match the particular airplane that I'm flying; two, it's a filter; and three, any fuel that's flung out of the venturi gets caught by the "filter" and sucked back into the engine, for a more regular run and better fuel economy.

Jim Svitko · « **Reply #13 on:** February 22, 2016, 04:31:33 PM »

I believe Carl Shoup made aluminum backplates for the LA 46. He might still have some or he might still be making them. The metal backplate from a 40 FP will also fit, if you can find one.

For the LA 46 with the OS spray bar of 0.137 inch diameter the venturi should be about 0.282 or so. That is what the venturis measured on the CL versions that I bought in the past. No carb, just a venturi and conventional needle assembly. I have heard of some 46s coming from the factory with a venturi of 0.256 which might be OK for the 25 but I think it is too small for the 46.

That needle assembly part number (22311000) might have been intended only for the 20-25 but over time it was discovered that it would work on other engines. Maybe the application lists were never updated to show all the engines it would fit and therefore we have this confusion.

There is a good deal of experience on this forum with the LA 46. Many different combinations of parts will work as the engine is so versatile and user friendly.

Geoff Goodworth · « **Reply #14 on:** February 22, 2016, 05:01:05 PM »

If you want to retain the rear needle setup, use the standard rear NVA and the OS Nozzle 20-40FP-S, Tower stock number LXMU30 $6.29, OS part number 21381980 if it is still available.

For a front NVA setup, use the factory NVA 20-25FP-S, Tower stock number LXCR49   $13.49, OS part number 22311000.

There are now only two factory venturis—

FP 20/25 Venturi   LXCW99     9.49   22312000
FP 40 Venturi   LXCX05   11.99   23312000

The FP 20/25 venturi is 6.55mm ID, the FP 40 venturi is 7.1mm ID. This is the larger of the two that were supplier with the FP 35/40 when the factory supplied two venturis. It is also the venturi supplied with the 46LA-S. The smaller FP 35/40 venturi is 6.75mm (17/64") ID. I have reamed out FP 20/25 venturis to 6.75mm ID.

Depending on model weight, prop, etc, you will probably find that the LA will be happiest with the 6.75mm or the 7.1mm venturi. There is no single answer.

Chris Fretz · « **Reply #15 on:** February 23, 2016, 09:27:44 AM »

Thank you all for the great information!

Tim Wescott · « **Reply #16 on:** February 23, 2016, 10:26:35 AM »

Quote from: Geoff Goodworth on February 22, 2016, 05:01:05 PM

Depending on model weight, prop, etc, you will probably find that the LA will be happiest with the 6.75mm or the 7.1mm venturi. There is no single answer.

That's why I like the adjustable nylon filter idea -- I just need to start with a venturi that I know is as big as I'll ever need, and neck it down from there.

Chris Fretz · « **Reply #17 on:** February 23, 2016, 01:53:45 PM »

Quote from: Tim Wescott on February 23, 2016, 10:26:35 AM

That's why I like the adjustable nylon filter idea -- I just need to start with a venturi that I know is as big as I'll ever need, and neck it down from there.

Do you have any picture of this little trick?

Tim Wescott · « **Reply #18 on:** February 23, 2016, 02:32:54 PM »

Quote from: #Liner on February 23, 2016, 01:53:45 PM

Do you have any picture of this little trick?

Here.

Chris Fretz · « **Reply #19 on:** February 23, 2016, 06:22:05 PM »

Quote from: Tim Wescott on February 23, 2016, 02:32:54 PM

Here.

Do you have multiple layers of pantyhose on them? The Ringmaster looks like it has a interesting story to be told...

Tim Wescott · « **Reply #20 on:** February 23, 2016, 07:49:49 PM »

Quote from: #Liner on February 23, 2016, 06:22:05 PM

Do you have multiple layers of pantyhose on them? The Ringmaster looks like it has a interesting story to be told...

Each has as many as it needs. Between one and four, although the purple stuff isn't quite pantyhose material -- it's woven instead of knit, which makes it easier to handle (and besides, it's purple -- who wouldn't want that?).

One layer doesn't impede airflow much at all, but it does keep the engines from blowing fuel out the intake. Two layers starts to slow the engine down, four definitely does.

Basically, with a too-big venturi you have to run very rich, using a lot of fuel, and the engine has a tendency to run away. So you pile on layers until the engine isn't threatening to run away, but still has good power and picks up on the up lines (or at least doesn't sag).

If you have to lean it out so much that it fades on the up lines or at the tops of maneuvers then you've gone too far and you need to remove a layer.

Chris Fretz · « **Reply #21 on:** February 24, 2016, 05:13:19 AM »

Quote from: Tim Wescott on February 23, 2016, 07:49:49 PM

Basically, with a too-big venturi you have to run very rich, using a lot of fuel, and the engine has a tendency to run away. So you pile on layers until the engine isn't threatening to run away, but still has good power and picks up on the up lines (or at least doesn't

What do you mean by run away?

Tim Wescott · « **Reply #22 on:** February 24, 2016, 09:55:55 AM »

Runaway is when you start a flight with over 5-second laps expecting to fly for six minutes, then you fly for over ten minutes with 3.5 second laps, all the while wondering if your right arm will still be the same length as your left arm once you land.

Chris Fretz · « **Reply #23 on:** February 24, 2016, 10:05:50 AM »

Quote from: Tim Wescott on February 24, 2016, 09:55:55 AM

Runaway is when you start a flight with over 5-second laps expecting to fly for six minutes, then you fly for over ten minutes with 3.5 second laps, all the while wondering if your right arm will still be the same length as your left arm once you land.

Ok, so basically you get it adjusted on the ground where it sounds good an it leans out in the air running like crap or too fast. I think I follow you now. Been there many times.

Tim Wescott · « **Reply #24 on:** February 24, 2016, 10:33:49 AM »

Quote from: #Liner on February 24, 2016, 10:05:50 AM

Ok, so basically you get it adjusted on the ground where it sounds good an it leans out in the air running like crap or too fast. I think I follow you now. Been there many times.

That's runaway. Engines always speed up a little bit from launch to flight (even piped engines), but a good stunt run means that you experience no, or no appreciable, increase in speed over the duration of the flight.

I have engines that, when improperly handled, will start just fine, get halfway through the pattern, and then ZOOM! they'll take off like bandits. One of them is in my "pretty good" pile because the best I can do with it is about an 0.1 or 0.2 second/lap speed up about half way through, without too much thinning out on the tops of maneuvers.

Both of my 46LA engines run nice and solid through the pattern, BTW.

Brad LaPointe · « **Reply #25 on:** February 24, 2016, 11:21:44 AM »

Too high of a pitch prop will cause a runaway also . 11-4,11-5 is a good place to start .

Brad

Chris Fretz · « **Reply #26 on:** February 24, 2016, 04:45:03 PM »

Quote from: Tim Wescott on February 24, 2016, 10:33:49 AM

That's runaway. Engines always speed up a little bit from launch to flight (even piped engines), but a good stunt run means that you experience no, or no appreciable, increase in speed over the duration of the flight.

I have engines that, when improperly handled, will start just fine, get halfway through the pattern, and then ZOOM! they'll take off like bandits. One of them is in my "pretty good" pile because the best I can do with it is about an 0.1 or 0.2 second/lap speed up about half way through, without too much thinning out on the tops of maneuvers.

Both of my 46LA engines run nice and solid through the pattern, BTW.

The last flight I had at the end of summer I had this ZOOM problem, Its a O.S. Max-H 40S. Ive never had it run triple turbo on me like that

. I finally started balancing my props last year, boy does that change things. I guess thats what added to it over revving. I hope I didnt burn her up.

Chris Fretz · « **Reply #27 on:** February 24, 2016, 04:49:23 PM »

Quote from: Jim Svitko on February 22, 2016, 04:31:33 PM

I believe Carl Shoup made aluminum backplates for the LA 46. He might still have some or he might still be making them. The metal backplate from a 40 FP will also fit, if you can find one.

It was Curtis Shipp

Mark Scarborough · « **Reply #28 on:** February 24, 2016, 05:06:26 PM »

Quote from: #Liner on February 24, 2016, 04:45:03 PM

The last flight I had at the end of summer I had this ZOOM problem, Its a O.S. Max-H 40S. Ive never had it run triple turbo on me like that . I finally started balancing my props last year, boy does that change things. I guess thats what added to it over revving. I hope I didnt burn her up.

your fuel mix can add to the problem of run away as well,, more castor can help in my experience,,
its all a system, you change one aspect and it all changes,,

balancing props is paramount to your airframe surviving, and your engine running properly, vibration will disintigrate the nose and vibration will also cause fuel foaming which can cause a lean condition ...

Brett Buck · « **Reply #29 on:** February 24, 2016, 06:32:02 PM »

Quote from: #Liner on February 24, 2016, 04:45:03 PM

The last flight I had at the end of summer I had this ZOOM problem, Its a O.S. Max-H 40S. Ive never had it run triple turbo on me like that . I finally started balancing my props last year, boy does that change things. I guess thats what added to it over revving. I hope I didnt burn her up.

Note Brad's comment above. Most of the problems come not from the engine itself, but from trying to run the engine too slowly (like, in a 4-stroke). Most of the modern RC engines were never intended to run that way, and they don't do it very well. That's just as well, because the sort of slow, 8500-RPM with a 10-6 style run hasn't been used in competition stunt for many years, with some exceptions. I would not even bother trying 6" pitch propellors on most current RC engines - even if you can get it to work, you are stuck with 1975 levels of engine performance, instead of the current VAST IMPROVEMENT.

Even with 3.5-4" of pitch, the airplane can end up too fast. That's a problem that can be solved a variety of ways that maintain modern levels of performance.

Brett

Chris Fretz · « **Reply #30 on:** February 26, 2016, 10:21:11 AM »

Quote from: Brett Buck on February 24, 2016, 06:32:02 PM

Note Brad's comment above. Most of the problems come not from the engine itself, but from trying to run the engine too slowly (like, in a 4-stroke). Most of the modern RC engines were never intended to run that way, and they don't do it very well. That's just as well, because the sort of slow, 8500-RPM with a 10-6 style run hasn't been used in competition stunt for many years, with some exceptions. I would not even bother trying 6" pitch propellors on most current RC engines - even if you can get it to work, you are stuck with 1975 levels of engine performance, instead of the current VAST IMPROVEMENT.

Even with 3.5-4" of pitch, the airplane can end up too fast. That's a problem that can be solved a variety of ways that maintain modern levels of performance.

Brett

So what rpm do you run these newer RC engines? An what pitch are you getting at? Maybe I should just ask what are the variety of ways?

Tim Wescott · « **Reply #31 on:** February 26, 2016, 11:24:15 AM »

Quote from: #Liner on February 26, 2016, 10:21:11 AM

So what rpm do you run these newer RC engines? An what pitch are you getting at? Maybe I should just ask what are the variety of ways?

I launch at 9500 to 9800, depending on plane, motor & prop. I've measured flights, and in the air the RPM rises to between 10,000 and 11,000. This is with props with rated pitches ranging from 3.75 to 4.5 and diameters ranging from 11 to 12.25.

Some people try to run them like the "old days", with a 6-pitch prop running deep in a 4-stroke. There seem to be a few that are successful at this, but no one local to me does this that I know of, and they're certainly not the ones smiling in the winners circle at the end of the contest.

Brett Buck · « **Reply #32 on:** February 26, 2016, 11:39:44 AM »

Quote from: #Liner on February 26, 2016, 10:21:11 AM

So what rpm do you run these newer RC engines? An what pitch are you getting at? Maybe I should just ask what are the variety of ways?

You want to be able to run them in the range that 4" of pitch or so gets the right airspeed. Depending on the airplane and the prop diameter, and how the engine runs, that could be ground RPM of anywhere from about 92-9300 to about 11,500. I can have more later...

Brett

Chris Fretz · « **Reply #33 on:** February 26, 2016, 01:22:02 PM »

Quote from: Brett Buck on February 26, 2016, 11:39:44 AM

You want to be able to run them in the range that 4" of pitch or so gets the right airspeed. Depending on the airplane and the prop diameter, and how the engine runs, that could be ground RPM of anywhere from about 92-9300 to about 11,500. I can have more later...

Brett

Does the LA 46 count as a newer RC engine?

Tim Wescott · « **Reply #34 on:** February 26, 2016, 01:44:09 PM »

Quote from: #Liner on February 26, 2016, 01:22:02 PM

Does the LA 46 count as a newer RC engine?

Absolutely.

Daniel_Munro · « **Reply #35 on:** February 28, 2016, 06:41:01 PM »

I've got two LA46 engines here I am going to convert soon. One is well used the other is NIB. RSM appear to have a delrin venturi and ST46 NVA which should work well together.

I've caught the electric bug, but figure these engine will be good on a couple of stunt trainers I will build for teaching our club juniors.

Chris Fretz · « **Reply #36 on:** March 14, 2016, 06:42:11 PM »

Everone raves about the LA so how does the .46FX fit in? And whats the story with the 40FP? Also do the venturis from the LA fit on the FX or FP?

Tim Wescott · « **Reply #37 on:** March 14, 2016, 07:17:57 PM »

Quote from: #Liner on March 14, 2016, 06:42:11 PM

Everone raves about the LA so how does the .46FX fit in? And whats the story with the 40FP? Also do the venturis from the LA fit on the FX or FP?

The FX series are ball-bearing engines that are designed to turn much faster. They're considerably heavier and they're ported differently. You may be able to get one to run nicely, but it'd be its own adventure. I suspect that you'd end up with a setup more like the 40VF, but I have no real clue.

The FP series is the direct predecessor to the LA series, and basically addressed the same market (the beginner RC pilot, really). I don't have any 40FP engines, but my understanding is that they are more or less "LA-ish", if perhaps a bit better than the 40LA when run correctly.