OS FP ENGINES

[Dudley Lang]

I read on the forums about OS FP control-line engines, in particularly the 20 fp and the 25 fp.  However I can not seem to find a website to buy one.  How do you find them?

[Bill Little]

I read on the forums about OS FP control-line engines, in particularly the 20 fp and the 25 fp.  However I can not seem to find a website to buy one.  How do you find them?

Hi Dudley,

Welcome to the site!  I know you will enjoy it here.

As to the OS FPs, they are welll out of production.  Swap meets, local R/C fliers and ebay are the usual sources.  The R/C and C/L engines are the same except for the carb versus the venturi/NVA.  Sometimes you can score a NIB one, but usually a used one.  They are long lived engines so if not really abused, they still run well.  Tower Hobbies still stocks the sleeve/piston sets just in case!

[Leester]

Dudley: Welcome to the hangar. As far as the FP's go make sure you ask here if the price is fair and the condition is good. We have alot of engine experts and we don't want you getting screwed.

[Bill Little]

Dudley: Welcome to the hangar. As far as the FP's go make sure you ask here if the price is fair and the condition is good. We have alot of engine experts and we don't want you getting screwed.

Great point, Lee!  THANKS!

[Chris Wellington]

A few r/c and one stunt version have come up on the UK ebay site recently all New in Box at around the 30 - 35 pounds mark : probably $ 70 so guess that's not a bargain for US buyers 

[Mike Pick]

Hi Dudley,

You could always buy a clone, like the Thunder Tiger 25, which is a well made engine and you can get venturis for them.  They do use a carb with a ST type bolt but this shouldn't be  a problem.

[don Burke]

The only problem with the TT is the location of the hole used for the needle valve when using the TT sprinkler venturi.  It's on the forward side of the venturi bore, puts the needle VERY close to the prop.  Alternatives are to use a remote needle (which some people don't like), an after market with the through NVA above the venturi spigot, or the R/C carb wired open.

[Bill Little]

The only problem with the TT is the location of the hole used for the needle valve when using the TT sprinkler venturi.  It's on the forward side of the venturi bore, puts the needle VERY close to the prop.  Alternatives are to use a remote needle (which some people don't like), an after market with the through NVA above the venturi spigot, or the R/C carb wired open.

Hi Don,

Your fixes work, but I like to use Tom Lay's method, and drill the case right below the venturi, trying to keep it 1/2" above the level of the mounts.  A *touch* extra work, but it seems to be easier to set up tanks that way.

BTW: I remember someone doing a study of NVA mounting *heights* inj relation to the mounts.  It concluded that the positiong height had little to no effect on the tank height setting.  This was backed up by using the same engine,. tank mounting height and NVA in the same plane, just moving he NVA to above the case inthe venturi, at the *stock* "hole" (ST engine), and in the case.  I would not have believed it, but it pointed to some center of volume in the crankcase and not the NVA position as being the determining factor in tank height.

[don Burke]

Probably the best way to do it.  Although some people come down with a severe case of hives when drilling a hole in an otherwise perfectly good engine is suggested.

Spraybar position does have an effect in a profile (sidemount) installation.  One of the racing tuning procedures is tank position inboard and outboard, affecting takeoff and rich/lean in the air. 

[Geoff Goodworth]

The criticism of the Thunder Tiger where the hole for the NVA is forward is valid but the difference is less than 3/8".  Is it that hard to be careful?

Also, the latest generation Magnum engines all seem to have the holes in the crankcase for an OS-type venturi with the NVA through the venturi.  Is there a useful .25 in that range?

Cheers, Geoff