FP Backplate on LA15

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Dawg
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FP Backplate on LA15

Post by Dawg »

I recently installed the FP aluminum backplate on a couple of my LAs. I had heard of good and bad results. I flew both Saturday and they turned 17,4000 on 15% Powermaster without trying to lean them out.

If you could post you experience here, I will appreciate it. You don't have to post facts and figures, just whether you use them now or not, and if your LA performs the same without having to worry about the backplate leaking.

Thanks

David McGinnis
SSC McGrizzBat Flyer
http://www.hilltopflyers.com
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Lou Melancon
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Post by Lou Melancon »

David,
Don and I tested the same engine with both types of backplates one morning several months ago. We noted a 200 rpm drop in overall rpms with the metal backplate.

Since most of my engines have to be run on lower nitro to make the max rpms it is not a problem. The better seal and not having to worry about them loosening is well worth the three bucks.

If I remember correctly the metal backplate is about .1 inch shorter and does not fill the crankcase quite as much. Also its shape is probably not as efficient at getting fuel to the intake bypass which is what I attribute its slightly lower performance too.

Lou Melancon
Alpharetta, Georgia
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lightning
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Post by lightning »

Lou, I think you're off by a decimal place!! I measured the FP backplate at 0.02 (or 20 thou) shorter than the original plastic LA!
I concur with the 200 rpm loss, but I have not had a leaker since I did my conversions. (And, for Tim's benefit, I don't have to retighten them every two or three flights either!)
As there is no gasket on the LA I simply used gasket cement with the aluminum FP backplate, held by cap head screws.
For $3 it's a cheap fix!!

Keith J (member OGC)
Radio Control Club of Detroit
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THend
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Post by THend »

Do we have a Tower Hobbies Part number for this back plate? I got a 50$ gift certificate for Tower, and this sounds like money well spent. I have one OS LA and have yet to run it. Might cut to the chase and get it right.

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Lou Melancon
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Post by Lou Melancon »

Keith,
Instead of a gasket or sealant I smeared toothpaste on the backplate and lapped it to the crankcase by hand turning it back and forth about a quarter turn back and forth till both surfaces were equally shiny with no flat spots. Total time? 5 minutes, priceless.

Terry its an East Coast secret but I'll give you a hint, go to the parts section of Tower's web site and search for .15FP.

You nuclear dudes all need too much documentation. Do you keep manuals in your flight box?

Lou Melancon
Alpharetta, Georgia
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lightning
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Post by lightning »

The backplate is Tower Part #LXCF83 - here's the link http://www2.towerhobbies.com/cgi-bin/wt ... LXCF83&P=7 I see the price has jumped to $3.39 [8D][8D]
You do have to make other arrangements for a RNV if you have not yet cut the original off the POS plastic backplate. I use the OS housing from the LA40/46/65 part: http://www2.towerhobbies.com/cgi-bin/WT ... &FVPROFIL= - they cost $7.49 and use the original LA15 Needle, "O" ring and ratchet spring.
Good luck with your motor(s).

Keith J (member OGC)
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THend
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Post by THend »

Actually, yes I do keep manuals in my flight box! Rules too! LOL!

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lightning
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Post by lightning »

Speaking of rules I do believe we have an unintentional limitation in the "new for 2004" engine mod rules:
Section C (under engine modifications) says: <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">c: The back plate of the engine may be exchanged for the back plate of another manufacturer’s SSC legal engine.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> A strict interpretation of this rule would render the FP backplate on the LA <b>ILLEGAL</b> as it is from the same manufacturer.
I think we need to get this fixed so that a backplate from any other SSC legal engine may be used, regardless of who the manufacturer was. (Not that there are too many that will actually fit!!)
Technically I also violate the RNV rule as the needle valves I use are OS (from the LA40). The rule reads the same as "C" <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">d. The needle valve and spray bar may be replaced with another engine manufacturer’s needle and spray bar.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> I know it's kinda petty, but I know a few folks who are pretty hot on the rules' interpretation and right now all my SSC planes could be deemed illegal!
Comments anyone [?][?][?]

Keith J (member OGC)
Radio Control Club of Detroit
RCCA #622

[:)][:)]Edit 9/12: Exchanged emails with Lou Melancon who agrees this needs to be addressed. It's on his "to-do" list for action (by whoever the president is) after the elections. - Keith J
thojo
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Post by thojo »

IMHO the engine mod rule should be thrown out. 17,500 and 8x3 should be enough to keep things in check. The engine mod rules just adds more debate and controversy. We've had enough experience over the past year to show its not required....

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lightning
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Post by lightning »

Thojo, provided we keep the muffler limitations I'm inclined to agree with you. Why mufflers? If the stock muffler rule was eliminated I'd expect to see tuned pipes that would run 17,500 on the ground, but <i><b>REALLY</b></i> unload in the air.
Once again, let's think of the newbie who wants to get into this stuff. The more it's "Stock", the less deterred he will be by "What else do I need?"

Keith J (member OGC)
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thojo
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Post by thojo »

So what happens to the tired old .15's after a couple of years of hard service? Some of mine won't hit anywhere near 17,500 any more. Do I just scrap them? No mods, means having to buy new motors, instead of moding the old ones to pump any life left into them...

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lightning
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Post by lightning »

I guess, if it's OS LA15s you're talking about, you spend $24 on a new piston & cylinder assy. and hope the crank bushing is OK[:(][:(]
http://www2.towerhobbies.com/cgi-bin/WT ... H=OSMG4821

Keith J (member OGC)
Radio Control Club of Detroit
RCCA #622
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