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  • November 11, 2019, 04:02:55 PM

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Author Topic: Which is better, OS or HP .40 for Stunt/ Sport use?  (Read 657 times)

Offline frank mccune

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Which is better, OS or HP .40 for Stunt/ Sport use?
« on: July 11, 2019, 07:52:53 AM »
          Hello All:

           In my “Junk” Drawer, I have seven OS LA.40 and .46 engines.  Also in there there are also seven HP .40 engines both Silver Star and Gold Cup.  Which engine would you choose and why?

            Not wanting to stir the pot, but I am curious to have feedback from those who have used both.  My impression is...

                                                                   Tia
         

Offline Peter in Fairfax, VA

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #1 on: July 11, 2019, 11:51:13 AM »
LA .46, because I know they work.

Online Brett Buck

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #2 on: July 11, 2019, 12:12:18 PM »
           In my “Junk” Drawer, I have seven OS LA.40 and .46 engines.  Also in there there are also seven HP .40 engines both Silver Star and Gold Cup.  Which engine would you choose and why?

    This is a no brainer. The Silver Star made a decent stunt engine, stock, and was a good choice - *40 years ago*. The Gold Cup was not a good choice 40 years ago, a few people ran them but they require modification for stunt, which makes them no better than the Silver Star.

   The 40LA is a good engine *for today*, the 46LA is a better engine *for today*.

    All this presumes they are STOCK.

      Modified, "improved", "custom", who can tell? I have seen brand new straight-from-the-reworker 46LAs that would have been blown away by a stock Fox 35, and were utterly worthless. I am sure the reworker is a good guy with the best intentions but they have, generally, no idea what they are doing when it comes to stunt engines. In that case, I would probably have been looking for a stock Silver Star or Gold Cup.

   An 46LA *does not need modifications*, it's better than any engine anyone used back in the good old days straight out of the box. If you engines have been modified in any way, go find stock parts and put it back the way it came, then you can be pretty sure it's OK.

     Brett

Offline Peter in Fairfax, VA

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #3 on: July 11, 2019, 02:43:32 PM »
I just bought a "new" LA .46 off eBay.  It has what I think is the "stuffer" backplate (aluminum.)  Is the stuffer backplate any good?

Offline Air Ministry .

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #4 on: July 12, 2019, 08:33:00 AM »
Theres about three LA 46s there now .Ones ive seen handle 55 inch / 50 Oz planes no sweat .
However , extropolateing , a M A artical had Werwage try a HP front on a FSR OS 45 , stated he thought the smaller shaft limited the output . Tho was a 8 Oz motor so saved near 3 .

BUT the RPR rear induction suffers no such qualms . Profile youd likely need a inboard tank . Mine had the liner dropped 36 thou or the 0.7 mm , std stunt mod. 0.8 on the gold cup .
THEY SAY . but you need to check the deck high Vs. piston Posn. at max tdc before S P I appears . Look across from tansfer & or shine a flashlight up it , to see limit .
Measure & faff about . But youll find .7 mm , , or 36 1/2 thou. is about it , then + that on the head gasket . The RPR is something like O 40 C 60 on a less restricted intake passage .

Mine ran 1/4 bore venturie . Nylon . I think a 3.5 mm MVVS 15 spray bar . The later thickened end needle one .( like a S Tigre almost )
a 11 x 5 Master Prop , or in hurricanes a 11 x 4 Tornado , or my custom wonder prop . 57 Span 57 / 60 Oz ( muffled ).
The plane liked 65 Ft on .016 solids . A memorable flight at dusk off a beach , its third . Just enough breeze to keep it moving through the pattern on a low power setting .
( New motor , stale dregs of no nitro fuel , touchy needle , conservative setting . )
However its regularly coped with 20 knot steady & gusty air . And Ive now FOUR ready to assemble. Total . Shaving the case aint a good idea . To short an Ex screw thread .
Was donated the pieces to do one front intake , but Ive not tried that . RPR gives good load response so it keeps a steady airspeed . Almost telepathic in its efforts .

SO , we think the HP maybe will pull a bigger plane . Some cooked rings in hot weather , so a tongue muffler might not be a good idea for longivity .
For Noblerish size / weight devises the LA 46 will give noble service . Samuri Blood ? . Theyve no bypass port . If the 40 has , blocking it might get it as dependable .
Seems like FP 40s , opinions vary , on the 40s . One in the 60 + Oz mewgull on I think a 12 x 4 was pretty good tho . Maybe a bit less pitch & more rpm on the OS's
for heavier planes . Now how does that sound familiar .

The ABC OS's are maybe ? less likely to get upset running a fair dose of nitro , too . So really maybe theres nothing in it .
 Differant coloured Horses . Dunno if that effects things or not

Tho your ABC HPs wont burn up , running Nitro , Either . Try a 12 x 4 prop , maybe trim to 11 1/2 or 11 . so a ' E W ' find the load its happy at . Dont think 6 in pitch is it , with them .

Online Brett Buck

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #5 on: July 12, 2019, 11:15:19 AM »
I just bought a "new" LA .46 off eBay.  It has what I think is the "stuffer" backplate (aluminum.)  Is the stuffer backplate any good?

  I think that is not intended to "stuff" anything, it's there to replace the stock GRP blackplate, because people overtighten and crack the plastic ones. It doesn't need to be "stuffed" and there's no reason to think the "stuffing" it would improve it anyway.

     It's probably OK -  if that is the only supposed improvement. After many many years of watching this sort of thing go on, I would be at least be nervous that this was not the only "improvement" made, like they replaced the venturi/spraybar with a "better" one, or added extraneous head gaskets, machined the head to create a "hemi",  replaced the "laggy" rear needle system,  "corrected" the exhaust timing to "stunt numbers", or "blueprinted" it (even though no one outside the OS factory has any blueprints and the "blueprint" is almost certainly a DWG file on a CAD/CAM system).

    All of those "improvements" are unnecessary and probably undesirable. Once you have the engine, you have it, and there's nothing to do but inspect it for indications of rework; if so, take off the backplate and clean it out (since at least some of the rework experts routinely leave machining debris in the engine), replace any modified or erzatz parts, put it back together, and run it.

     If it looks otherwise stock, just leave it alone and run it as shown in post after post here. There's some chance that this will cause a problem - because *someone took it apart* - but most people can usually manage to just replace the backplate without wrecking everything else. Not all, unfortunately.

    Brett

Offline Dave Hull

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #6 on: July 12, 2019, 03:09:28 PM »
Laughing hard here. Got my stress relief for the day:

     "...since at least some of the rework experts routinely leave machining debris in the engine...."

This reminded me of an engine I bought from a guy right here on the 'hanger. I got it in the mail and was excited to open the box. All was not well, though. In fact, a Dremel Artiste had shoved a carbide burr down the venturi, with the engine still fully assembled, to "port the crank." There were so many chips inside it was crunchy when it was turned over....

And the beat goes on....

Divot McSlow

Offline RandySmith

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #7 on: July 12, 2019, 05:20:09 PM »
Laughing hard here. Got my stress relief for the day:

     "...since at least some of the rework experts routinely leave machining debris in the engine...."

This reminded me of an engine I bought from a guy right here on the 'hanger. I got it in the mail and was excited to open the box. All was not well, though. In fact, a Dremel Artiste had shoved a carbide burr down the venturi, with the engine still fully assembled, to "port the crank." There were so many chips inside it was crunchy when it was turned over....

And the beat goes on....

Divot McSlow

Dave

that was  a  guy who had  NO CLUE what he  was doing, I have  done  over  7000 CL Engines for the  Stunt Community, and  NO MATTER  what  Brett says, There  is  ways  to improve  engines, some need nothing  some need a little  and  some need a  bunch!, But also as Brett said  there  are some  who  are disasters, and  ruin motors  over and over  again.   So regarding  the question asked , the  la 46 is best all around but heavy when compared to the  HP, the hp is  second and the  LA 40 is  3rd.  All of this  in assuming the engines  are setup correctly, It is possible to have  wrong factory parts, or  have  better factory parts on some engines.  One of the  nice things about the  HP 40 is the  small  light package with so much power.  The nice thing about the  lA 46 is  power and  the wide range of styles it will  run in, and  I see  people  using  12x 5 ,  11 x 4.5  Cyclone , and  apc  12.25 x 3.75 props  all with great success .
I have also built 100s  of LA 46s  for  people, they seem to love them

Randy

Online Brett Buck

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Re: Which is better, OS or HP .40 for Stunt/ Sport use?
« Reply #8 on: July 12, 2019, 05:51:35 PM »
Laughing hard here. Got my stress relief for the day:

     "...since at least some of the rework experts routinely leave machining debris in the engine...."

This reminded me of an engine I bought from a guy right here on the 'hanger. I got it in the mail and was excited to open the box. All was not well, though. In fact, a Dremel Artiste had shoved a carbide burr down the venturi, with the engine still fully assembled, to "port the crank." There were so many chips inside it was crunchy when it was turned over....

   Simple matter, leaving it assembled tends to be self-jigging. Put a prop on it, stick the tool into the venturi, turn it around so it drops in the port, turn on the Dremel tool, and then turn the prop to push the edge of the prop up against the tool, until your carefully calibrated eyeball determines that it's "just right*. Remove and test fly, if it's not quite good enough, try again. If you have a battery-operated Dremel, you can do it at the field! 

     You don't need all this egghead stuff about micrometers and milling machines, that's the elitists keeping the regular Joe down.

   By the way - that's all parody, nobody do that!   I haven't seen quite that, but I have definitely seen multiple example of "precision port work" from guys with Dremel tools sitting on a picnic table at the field. And people "breaking in" their ball-bearing conversion by attaching a cordless drill to the shaft, and spinning it over while pouring carborundum powder into the venturi, slosh some fuel in it, and fly. Loosened her right up.  Either which is not a big problem, it's their engine -  aside from the fact that they *sold the engine for a premium price* as a "reworked for Lucky Best Stunt Run" at the end of the session.

  I can easily guess who the perpetrator was in this case, since I have seen something like it on multiple occasions.

   I know!  Just send the original expert reworker an email.

  Brett
   


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