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Author Topic: Fox 35 Disassembly  (Read 2808 times)

Offline Tim Wescott

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Fox 35 Disassembly
« on: November 23, 2009, 06:36:10 PM »
I'm about to degunk a Fox 35, but I'm having trouble disassembling it.

With the OS Max, and I understand in general, the disassembly procedure was to remove the cylinder liner, then ease the connecting rod off of the crank pin.  It's worked great on my OS Max 25s.

But with the Fox I get the con-rod all the way to the back of the engine, and the piston to the back of the bore, and I still need about 30 or 40 mils to get the rod off the pin.

Is there a trick to this?  Whenever I think "just pull hard" it makes me think "embarrassing conversation with Fox service department".

Thanks in advance.
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Offline Marvin Denny

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Re: Fox 35 Disassembly
« Reply #1 on: November 23, 2009, 08:17:08 PM »
  With the sleeve out, rotate the shaft so the crank pin is inthe 7 to 8 oclock position as viewed from the rear. (about 45 degerrs from bottom toward the bypass side).  In that position, grasp the rod with a pair of needle nose pliers (with the jaws protected with some masking tape) and pull the rod rearward and roll the rod inward toward the center od the case opening.  It SHOULD roll right off.  If it doesn't try rocking the shaft back and forth while trying to pull/roll the rod off.  IF it still doesn't come off, it may be that the rod is not sliding to the rear of the wrist pin  in the piston.  If that is the case,  place the sleeve back into the case enough to block the wrist pin and piston and take an allen wrench and pry the rod rearward on the pin then remove the sleeve and try again.  If it STILL won't come off, you may have to heat the case to about 250 degrees in an oven and while still hot try the  pulling/rolling operation again.  Be sure to use oven mitts or some sort of hand protection for this last try.
  Les us know how it comes out.

  Bigiron
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Offline sleepy gomez

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Re: Fox 35 Disassembly
« Reply #2 on: November 23, 2009, 08:28:34 PM »
Please, no pliers on the rod.  I have an engine done by a reputable shop that has pliers marks all over it.  Use an appropriate sized allen wrench.  Slip the short end behind the rod and pull.   You may want to use vise grips as a handle on the allen wrench. 
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Offline Tim Wescott

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Re: Fox 35 Disassembly
« Reply #3 on: November 24, 2009, 03:55:14 PM »
Quote from: Marvin Denny on November 23, 2009, 08:17:08 PM
  With the sleeve out, rotate the shaft so the crank pin is inthe 7 to 8 oclock position as viewed from the rear.  (snip)

Tried that - still doesn't work.  I'm taking a rest from it -- I don't want to hurry myself into any permanently deformed engine parts.

I've sent email to Fox and they've promised a reply from the engine guy -- perhaps that'll have some guidance, perhaps not.

The motor was only used lightly -- I may bag the complete disassembly and _total_ cleaning and just brush it down in isopropyl.  Or I may go borrow the oven for a bit.

I _do_ want to get the plane in the air!
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline L0U CRANE

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Re: Fox 35 Disassembly
« Reply #4 on: November 24, 2009, 04:56:05 PM »
Tim,

A last resort type of solvent to soften the gummed castor on the wristpin/conrod fit may be naphtha (lighter fluid). IF, that is, the problem is at that point. ...Probably is...

Oil it as soon after as possible, too.

Luck!

Also, curious what "degunking" you have in mind. If it is external, yeah, sure looks better without the scorched, darkened castor. Internally, though, some apparent gunk can be healthy. Hot castor, so the story goes, is driven into the somewhat porous cast iron piston material, and helps maintain seal with the sleeve clearance... Looks dark, but how many people are going to examine the piston skirt through the exhaust port?
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Offline Tim Wescott

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Re: Fox 35 Disassembly
« Reply #5 on: November 24, 2009, 06:19:16 PM »
Quote from: L0U CRANE on November 24, 2009, 04:56:05 PM
Tim,

(snip)

Also, curious what "degunking" you have in mind.

Ethylene glycol antifreeze and a crock pot.  One reason I'm thinking of not bothering is because after getting it open it doesn't look at all bad -- there's a bit of old oil in there, but it's not all varnished up the way some of my engines were.  As you said, yes, it'll look prettier on the outside, but I don't think I'm going to impact performance or life much if at all by not cleaning it at this point.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Marvin Denny

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Re: Fox 35 Disassembly
« Reply #6 on: November 24, 2009, 07:04:16 PM »
 Lou is 100% right on that.  Only one other thing--- be sure the rod slides easilt forward and backwards on the wrist pin because if it is frozen to the wrist pin, excessixe wear will occur on the piston and also the engine will not run smoothly..
  Bigiron
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Offline Jim Kraft

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Re: Fox 35 Disassembly
« Reply #7 on: November 24, 2009, 07:26:49 PM »
If you do not get the rod unstuck from the wrist pin, it may push out one of the circlips in the piston and ruin the sleeve. Most old Fox 35's that have not been run for a while without after run oil are stuck. I never run an old engine that has not been run for a long time without cleaning and freeing up the rod.
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Offline Russell Shaffer

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Re: Fox 35 Disassembly
« Reply #8 on: November 24, 2009, 07:53:40 PM »
Try a propane torch.  Just play the flame into the bottom of the piston but not for too long.  Or, if you have a heat gun use it.  It didn't take too much on the last old engines I tore down.  A little heat loosens up the old castor very quickly. I used a heat gun on a couple of Veco 45's and some old Foxes.  You do not have to get the piston or the pin red hot by any means - just way too warm to touch. 
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Russell Shaffer
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Just North of the California border

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