Fox 35 engine

[Bootlegger]

  I have a fox 35 set up with hemi head, stuffer back plate aluminum piston running in a ceramic liner.
  What fuel should I use to run in it? 10% nitro with 22% oil half & half, or more castor?
  I don't want to damage the engine in any way, but want to get the best use from it.

   Thanks for your advise...

[Lyle Spiegel]

i have same Fox  setup and run only the 100% castor 29 % with 10% Nitro, Runs like a sewing machine. Guess I am old school, but I believe extra oil is needed so the front bushing get adequate lubrication.

[RandySmith]

Use  28% oil  with part synthetic,   can be  half n half, or  quarter synthetic , the engine will be lubed better, and last much longer
who's  fuel do you buy?


Randy

[Garf]

I mix my own fuel and would use 20% castor plus %5 klotz oil and 5 to 15% nitro.

[Lyle Spiegel]

I have few gallon remaining Powermaster GMA 10%/ 29 , and 1 jug Brodak 10% nitro- 29% oil I picked up last year at the store in June.
 .
When my inventory is gone, not sure what I will do. Powermaster web site still lists GMA 10/29 so maybe its not discontinued? Would have to get a LHS to order it. LHS in Lee Mass is now closed down so will need to find alternate source.
l.
Might also phone up S&W , their web site says they will sell custom mix. I would need to drive there to pick up to avoid shipping charges.
As last resort, maybe I need to head to the local  dragstrip ( opens in April)  and get a 1/2 gallon nitro, and some methanol, mix my own.
I will need to find castor oil.

[Bootlegger]

 Randy,
  Right now I'm using P/M 10-22 fuel in everything, sometime I cut it in half and use that..

 Thanks for your help...

[Fredvon4]

Lyle

I admittedly do not burn the qty of fuel some here do practicing
But do NOT have ANY local source for good stunt engine fuel

I buy Sig Quarts to cover most of my engines.. specifically the Cox and Norvel 1/2as
I got Riche's brew for some specialty combat engines
I can source low cost methanol locally but not Nitro--- so I order Nitro from Torco by the gallon
There are a lot of good places for rather inexpensive Oils

I got a close out deal ($9.99 /Gal) on some 5 gallons of 35%N 17% oil car racing fuel

With all the on line calculators and deciding to use metric volumes, I can blend any mix Randy or others recommend for a particular engine

While I would never disagree with Randy Smith on a Fox Iron lung needing 28% oil... I did deviate some and experimented with his recommendation and a reduction of total oil down to 23 %.. 20% Castor and 3% Ucon LB625 and a dash of his Aero 1 additive... Where I thought 15% N 28% Oil was the best, I can now start and run the old Fox on 5% N and it runs and needles just fine with the lower Oil content mix

Disclosure.... I might only ever put 10 to 20 ---3 to 6 min ---flights a year on any one engine

That said I do not think any of my engines will ever be in danger of wearing out from the fuel.... Dorking and too lean a run are currently being mitigated...with practice

[C.T. Schaefer]

Despite the modernish piston and cyl. the hottest spot is the small end of the rod/wrist pin/piston and thats where the higher oil content fuel is well worth the trouble and mess.

[RandySmith]

HI Fred

People run many fuels in their Foxes, they will  run  OK on 22%, and you can run whatever blend you want,  but  they will  not last as long, the Fox 35  has a very  tiny case bushing, a cast small rod with  no bushings at either end, and a very small  piston pin boss . these areas  ALL  need  lots of lube.  all the more so when you run  15% nitro,
15% is approaching the territory  where  Fox 35s  start  shooting  cranks out the front of the motor, the extra oil will  not hurt  there  either

The high % oil  also not only helps lube the  Fox, it helps to cool it too.

Randy

[Fredvon4]

Randy...trust me sir, I heed your advice a LOT..

And re-reading my poorly written missive above, I see I was not very clear

I have several Fox .35 .40 examples that were initially Broken in using Your and others advice

In each case the engines ran well, but I soon found that various amounts of Nitro yielded a significant difference in Needle sensitivity...  all exclusively have Your PA needles

I got the notion that the preferred initial set up was with 5% N expecting to increase the %N with weather or elevation changes

So here I am at 600'+/- elevation and Wx (when I fly) from 60F~98F  +/-  and 35%~74% RH and never fly anywhere else

When I was breaking in and re-learning how to fuss with these Fox engines ---I noted that the 10% N and 15%N fuel gave me a much broader and easier to set needle

So considering what you wrote above, I think this year I will dial back the N to 10% but feel pretty confident with the 23%~25% using the Castor/UCon and Aero 1 mixture

I will also note I do ONLY use the very cheap car fuel for bench running--- but since I have no idea of the real vs claimed 17% oil-- I add-- what I think-- brings the oil into the 28~32% range for the iron engines and when running, they seem relatively cool and smoke a lot, even when pinched to short fast bursts...

I am a heat cycle believer so very fast 4 breaking into 2 stroke and brief (15~20sec pinches to lean) for each 4 to 5 min run cycle

If anything about my use.. (remember I do NOT run ANY engine for 100s of flights a year) please school me

Back to Gils question...I get the idea that having a ceramic liner and alum piston is not the issue BUT the oil content still needs to be high due to con rod configuration as well as case bushed bearing

[Brett Buck]

Randy...trust me sir, I heed your advice a LOT..

When I was breaking in and re-learning how to fuss with these Fox engines ---I noted that the 10% N and 15%N fuel gave me a much broader and easier to set needle

   That's definitely true. It's much *louder* as well. I wouldn't even bother with 5% any more. Heed well the caution about 15% and higher  - unless you have a Randy super-crank, you are going to break one eventually.*

    But at least for stock engines, adding castor can sometimes act like adding an equivalent amount of nitro. I am not sure why, maybe it cools it better so you can run it harder, or maybe it fills up the gaps and improves the compression, but it can be very effective. And even on the engines with most of the internal parts replaced, you still use the same conrod, which needs lube. I am less convinced about the bushing, they seem to last a pretty long time, and you want it to be pretty loose, because IMHO, you need it loose to get clockwork 4-s breaks. I have seen people retire engines or get new crankcases for bushing wear that I thought were just getting right.

     Brett

*I got a PM not too long ago accusing me of shilling for Randy, partly because of the discussion of the high-zoot Fox 35 crankshaft. That's absurd on several levels (since I spend a lot of time on Randy's poo-poo list for various possibly-justifiable reasons), but the super-crank definitively resolves both the breakage issue, and usually/frequently greatly reduces the vibration over the stock crank. I think it's more then the counterweight, since plenty of people have added tungsten slugs to stock cranks without having much effect. I think the stock cranks are frequently eccentric or crooked, and Randy's are straight.

[Joseph Patterson]

   Randy, I see you no longer have the H-Z CRANKS, BUT OFFER THE STOCKED BALANCED CRANK. Still have any of those in stock?
        Doug

[RandySmith]

  Randy, I see you no longer have the H-Z CRANKS, BUT OFFER THE STOCKED BALANCED CRANK. Still have any of those in stock?
        Doug

Hi Doug
Yes  i have a couple  left

Randy