Compare and contrast 50's and 70's Fox .19 and .25 engines

[frank mccune]

    Hi All:
   
    While searching through the goodies in my attic, I came across a stash of these old engines.  There are some of the 50's engines with the three screw back plates and some with the later 70's engines that have the 4 screw backplates.

     Does anybody know if one engine was better than the other for power handling etc.?  I have a old copy of an Engine Test of the three screw Fox .25 that was published in a 50's M.A.N. that claimed that they got well over 12,000 rpm with a 10X6 prop.  This is  about 2000 more than what the Fox .35 Stunt delivered in another test! The explanation was that the .25 had much larger gas passages than the .35.  The 70's engines are the ones that are a bit larger than the Stunt .35 looking .25 engines.  The 70's models also had the vertical venturm with a larger cases.

     If I remember correctly, the .19, .25 and the Stunt .35 all had the same mounting patterns.

     I am planning to use these engines on Goldberg Shoestrings that are left over from my Foxberg days.

     Anybody ever use these engines?  What are your memories of these engines?

                                                                                    Tia,

                                                                                    Frank McCune

[dennis lipsett]

Frank,

I've used the 4 bolt 25 on a few older models with excellent results. They are more than capable of flying a Goldberg shoestring or any other similar models. the 3 bolt 25 was said to have as much power as the Fox 35 which speaks volumes about the Fox 35 and is a nice runner. I never cared much for the 3 bolt 19.
I have a few 4 bolt 19/25 NIB and apparently there is little interest in them.

Dennis

[Air Ministry .]

reading Peter Chin's ' engine tests ' in muddling mags , theres TWO 4 bolt 25s .
about 81 they put muffler lugs at the end of the stack ( front and rear ) and wilderised the timing .

Late 19s have a 1/4 shaft and some a Blackened STEEL prop driver , which saves the nastyness with sloppy thin alloy ones .

Shoestring'd want to be light , but theres always NITRO .

[dennis lipsett]

reading Peter Chin's ' engine tests ' in muddling mags , theres TWO 4 bolt 25s .
about 81 they put muffler lugs at the end of the stack ( front and rear ) and wilderised the timing .

Late 19s have a 1/4 shaft and some a Blackened STEEL prop driver , which saves the nastyness with sloppy thin alloy ones .

Shoestring'd want to be light , but theres always NITRO .

The earlier engines had a 10-32 threaded shaft. The flimsy 3-48 bolts that were used to hold the bits together were in a word really cheap. I replaced all of them with 3-48 socket screws.

[frank mccune]

      Hello:

      Thanks for the replies.

      I have engines that I consider better than the Fox engines but like the Sherman tank, not the best but I do have a large number of them.  This is also true off my stash of old McCoy engines.  I would hate to go to my grave without having the pleasure of having the Fox or McCoy experience. Lol

     I also have a collection of good O.S., Enya and S.T. engines that are capeable of providing me much pleasure without the problems of difficult starting short life etc.  I did pick up a Brodak .25 which is a great engine!  No problems with this one!

      Since my return to model airplanes after a 30 year hiatus, I have been less tolerant of using engines that are difficult to start.  If it does not start in a few flips and I can not rectify the problem, I switch to an enging that will!  Back in the day, I pitted for two Foxberg fliers.  I could start their Fox .35 Stunts with one flip hot or cold!  Perhaps I just have lost the touch! Lol. Perhaps my cranking speed like other things, has slowed down over the years. Lol

                                                               Stay well my friends,

                                                               Frank MCune

     

[Bill Little]

Hi Frank,

I have used both Fox .25s and like the old 3 bolt back plate the best.  Power level seems to be close running a wet 2, but the 3 bolt does a hugely better 4-2 run.  Don Still ran the 3 bolt back plate in his WC Stuka.  They fly the Goldberg profiles, Ringmasters, etc., very nicely.  I really like the three bolt Fox .25.

Thanks!
BIG Bear
RNMM/AMM

[Steve Helmick]

I had a Fox .19 (3-bolt backplate version) that I really liked. I don't remember having any difficulty with starting it, or even any complaints about the NV Assy. being junk. But I must admit that it was stamped ".201" on the case, although that was just an expedient for Duke to provide the FF guys with an A > B swap. It was later discovered, except for that .201 stamped on the case, that all parts were identical.

I seem to recall that the .25 came about from the .19 being modified with a .29 piston. Does anybody know if it's possible to change a .29 stunt to a .35 stunt, with a simple piston/cyl change, like the 20/.25FP and .35/.40FP? Or change a Fox .19 to a .25?    Steve

[Bill Little]

Hi Steve,

Although the 3 bolt .25 is made from the .19 crankcase casting, it takes some doing to convert a .19 to a .25, it isn't a simple piston/cylinder swap.

Thanks!
BIG Bear
RNMM/AMM

[Air Ministry .]

Running the suckers in Twins , I FILL the Intake with the port closed . Belt it through so its good and free , hook up the electrickery
and if the battery's up to it ( essential with a sopping wet cylinder ) , a good belt ( like a diesel ) can fire them off first try . as often as not .

You wont get it with a half baked battery set up though .

Chin said of the later 4 bolt 25 " the most powerfull plain bearing 25 theyed tested .

Was surprised when I put the OS's in the Whirlwind instead of the Foxes , that it WASNT as good or reliable . So the FOXes are back in .
the 25s ( early 4 bolt - no fore & aft silencer lugs ) work good on zinger 9 x 5s . With a 19 & 25 i run Top Flite 9 x 4s , fkin good .
Ive some Mi T Gorrie ( narrow blade ) 10 x 4s too , look like TEAK . Ive furniture oiled two , as they must be 500 years old , give a zero or two .
Excellent might be used in referance to these .The 25s'll ' Shift Gear ' maybe in preferance to ' 4 - 2 ' the booming deepens .

The advantage of a 19 & 25 is the 19 yaps or yowls , where the 25 booms or rumbles , - so you can tell which needs a notch on or off the needle .
You just get dull stares and shrugs if you ask which was stuttering etc these days. So it pays to do it yourself . uneven runs often get uneven cuts
so engageing the brain cell and noteing which ones still going then riping over and seeing which has cooled off if you cant tell sorts it out on two matched injuns .

Twins clearing the fuel lines and needles pre flight & individual run up & tune saves having to do it when it doesnt go right . USUALLY 6 or 7 turns on the needle
is right with the cheap & nasty NVA , std tube mufflers & 10 or 15 % nitro .

SO clear the fuel line & set nose up just rich hot , for starters . Blow down line to check needle hole is clear - or push fuel through .