News:



  • June 21, 2025, 08:08:30 AM

Login with username, password and session length

Author Topic: Johnson & Fox questions  (Read 935 times)

Offline CharlesF

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 46
Johnson & Fox questions
« on: June 12, 2007, 09:43:30 AM »
Hi

I have two questions:

1) I have a Johnson 35S in my Thunderbird. Tank is uniflow. Fuel is 25% castor, 5% nitromethane, 70% methanol. Prop is 10 x 5 Zinger wood. My problem is, the motor won't two-speed. It just seems to run at constant speed, either slow and rich or fast when leaner. Same speed on insides, outsides and inverted. WILL the 35S do a two-speed run? It's 35 years since I last ran a Johnson 35 in a Thunderbird, but very vague memories tell me that that motor gave a good two-speed run, peaking in manouvres. That altitude though was around 6000' ASL - but now it's more like 100' ASL.

I was flying this morning, but stopped after 4 flights because it was getting very windy indeed.

2) I bought a new ABC picton/liner for my Fox 35. I favour running it in a few minutes at a time fast and rich on a 9 x 6. Would the experts agree? Fuel same as above. I had two gallons made up for me yesterday.

As a comment, I also bought a new HOT plug from the fuel people (Model Technics) and put it in my Torpedo 19 greenhead. Now, it does not sag when I take the battery off  :)

Charles
Canterbury
UK

Offline Dick Fowler

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 487
Re: Johnson & Fox questions
« Reply #1 on: June 13, 2007, 05:34:23 PM »
Hi Charles, I'll throw my two cents in on this. The Johnson should do a very nice 4-2-4 break. The fact that it runs consistent is a blessing but the engine might need more engine load. Try using a bit more prop like a 10" X 6P or an 11" X 5P. Most stunt motors won't break unless they see some load increase. The large prop will put more load during maneuvers and it should then break.

I would not run an ABC engine too rich during break-in.  I like the idea of 2 minute runs but I also like to hear the engines stuttering between two  and four stroke during the run.
Dick Fowler AMA 144077
Kent, OH
Akron Circle Burners Inc. (Note!)
North Coast Control Liners Size 12 shoe  XXL Supporter

Offline wmiii

  • 2014 Supporters
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 187
Re: Johnson & Fox questions
« Reply #2 on: June 13, 2007, 08:51:13 PM »
 That's how I remember my .35S running, constant speed, just what we seem to be asking for from current engines.

 Walter
walter menges

Offline CharlesF

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 46
Re: Johnson & Fox questions
« Reply #3 on: June 14, 2007, 04:40:42 AM »
Hi

Jim Ivey, who worked with Hi Johnson says they just run at a constant speed - that's what they are supposed to do!

So that's OK

Thanks guys  :)

Charles


Advertise Here
Tags: