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Author Topic: Hot/Cold plugs for FOX 35X  (Read 1760 times)

Offline Timothy Payne

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Hot/Cold plugs for FOX 35X
« on: May 30, 2013, 09:44:45 AM »
Need some tips on the best glowplug to use for a Fox35X. - I ran this recently aquired engine in after rectifying a small problem with the liner using a no3 short reach plug on 25%castor, 10% nitro fuel.

It ran fine for a while with a 10*6 prop, but started to overheat towards the end of on a full tank. I've since discovered how and why different plugs in different engines affect ignition timing; and am wondering whether I should stick with the Fox longreach plug which has given no real problems in any of my nitro collection? Also am I right in thinking that these motors were designed for a longreach plug anyway, primarily FOX?

Any ideas?

Tim
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Offline Brett Buck

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Re: Hot/Cold plugs for FOX 35X
« Reply #1 on: May 30, 2013, 06:24:08 PM »
Quote from: Timothy Payne on May 30, 2013, 09:44:45 AM
Need some tips on the best glowplug to use for a Fox35X. - I ran this recently aquired engine in after rectifying a small problem with the liner using a no3 short reach plug on 25%castor, 10% nitro fuel.

It ran fine for a while with a 10*6 prop, but started to overheat towards the end of on a full tank. I've since discovered how and why different plugs in different engines affect ignition timing; and am wondering whether I should stick with the Fox longreach plug which has given no real problems in any of my nitro collection? Also am I right in thinking that these motors were designed for a longreach plug anyway, primarily FOX?

   I am far from an expert but I think it uses long reach plugs, and the plug heat range is unlikely to cause it to overheat.

   For give my ignorance, but what is a "nitro collection"? I can envision a few meanings for that, but none that apply here.

    Brett
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Offline kenneth cook

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Re: Hot/Cold plugs for FOX 35X
« Reply #2 on: May 30, 2013, 08:25:34 PM »
   Hello Tim, the engine was designed for 20% oil content. One may feel that 25% oil won't do any harm, but it can ultimately do so. Seeing that the shaft is partially raced with a bearing be it needles or balls, your not dealing with a bushing like the stunt .35. Too much oil can take out a plugs due to upping the compression. Due to it's age and the notorious quality of the Fox, I wouldn't try pushing the nitro too much unless you have spare crankshafts. Keeping the nitro in the 10%-15% range will give good runs. Many of these were run hard back in the day. I see no reason a hot plug wouldn't suffice. If you start taking out plugs go to the next heat range or add an additional gasket. I personally use Thunderbolt R/C longs in my engines.

What plane are you using this engine on? You are aware that this engine is a combat engine? I'm questioning your prop choice of 10x6. The engine is designed to turn up a bit and the 10x6 isn't going to be happy on this engine. A 9x6 master Airscrew will work far superior. Another option is to use a 9x7 Master Airscrew and clip a 1/4" off each prop blade making the prop a 8.5x7. I've run these engines successfully with props like 8x7's and 8x8's. as well. ken
« Last Edit: May 30, 2013, 09:00:31 PM by kenneth cook »
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Offline RandySmith

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Re: Hot/Cold plugs for FOX 35X
« Reply #3 on: May 30, 2013, 08:29:10 PM »
Quote from: Timothy Payne on May 30, 2013, 09:44:45 AM
Need some tips on the best glowplug to use for a Fox35X. - I ran this recently aquired engine in after rectifying a small problem with the liner using a no3 short reach plug on 25%castor, 10% nitro fuel.

It ran fine for a while with a 10*6 prop, but started to overheat towards the end of on a full tank. I've since discovered how and why different plugs in different engines affect ignition timing; and am wondering whether I should stick with the Fox longreach plug which has given no real problems in any of my nitro collection? Also am I right in thinking that these motors were designed for a longreach plug anyway, primarily FOX?

Any ideas?

Tim

Hi Tim

The normal best plugs for the  FOX 35 X in a stunt or sport mode are these:
Glow Devil #300 (RC long)
T Bolt RC Long
SIG RC Long
FOX RC Long
T Bolt  Big Bore

There are others both idle bar and  non idle bar  but normally you want a long hot plug , These keep the FOX 35 running cleaner in manouvers while in a 4/2 or in a rich 2 cycle. IF  you are running them harder in a 2 cycle , then these do not  apply
This assumes your running it in a sport or stunt mode, if your using it for combat or racing then you want to use a cooler plug like a K&B  or a McCoy

Randy
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Offline Brian Hampton

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Re: Hot/Cold plugs for FOX 35X
« Reply #4 on: May 30, 2013, 09:09:58 PM »
Generally speaking the first step in finding the correct plug is choosing the length which should have the end of the plug level with the combustion chamber surface. For the Fox this is likely to be a long reach plug. The next step (heat range) is a bit more iffy. Heat range is part of what determines the ignition point, along with compression, fuel type, prop load etc, and really only becomes a consideration when tuning for peak performance. Heat range, like hot, warm, cold etc, doesn't refer to the actual temperature of the coil but more its ability to how easily it'll ignite the mixture. A "hot" plug fires the mixture easily so advances the ignition compared to a "colder" plug which has more difficulty. Essentially then the best heat range for peak performance is the one that gives the highest revs although there may only be a few hundred revs difference.

For an engine that's run quite rich and well below peak then heat range isn't nearly as critical in which case a hot plug is usually used.

There's quite a good read on the affect of different heat ranges in various engines and fuel changes at http://www.modeltechnics.com/glowplug/firepower.html
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Offline Timothy Payne

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Re: Hot/Cold plugs for FOX 35X
« Reply #5 on: June 12, 2013, 08:38:38 PM »
Cheers guys, that's helped me out. - (By the way it'll be used in a 46" Ironmonger FA1 - scaled up, on 35ft lines!)

 I'm even considering mounting the engine vertically; see main photo on 'Barry Baxters Plans Service' website. - I figure it's the only way I'll get enough fuel into the engine, as it'll be carrying probably around a 3 oz tank.=-O
« Last Edit: June 19, 2013, 06:52:58 PM by Timothy Payne »
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Offline Steve Helmick

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Re: Hot/Cold plugs for FOX 35X
« Reply #6 on: June 16, 2013, 12:05:15 AM »
Thirty five foot lines? Looking to get dizzy, are we?! That ought to do the job. And no hangover!  :-\

All Fox's .19 and above use a long reach glowplug. If you're running the .35X peaked, a "standard" or "medium" heat glowplug will work fine. I'm not a fan of Fox glowplugs at all. Not sure what you can get over yonder, but if you list what you can get easily, it would be a start. OS & Enya glowplugs are good but pretty spendy over here. I know there was a good brand of English glowplugs a long time ago, but I can't recall the brand name.  H^^ Steve

Edit: "Taylor" or something similar?
« Last Edit: June 17, 2013, 04:56:21 PM by Steve Helmick »
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