Club FOX!
07-06-2015, 02:57 PM
#4178
Join Date: Mar 2007
Location: tipp city,
OH
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Anyone here anything out of Fox lately? Website is still down. I see Tower Hobbies still has stock on their glow plugs and a few other small items. Is Fox still making glow plugs? My LHS still has Fox plugs and I didn't think to ask about continuing to get them. A lot of people use their plugs even when the don't have a Fox engine so that can still be a source of business.
07-06-2015, 06:18 PM
#4179
Fox still makes the glow plugs. But they sell them through the distributors. Their website hasn't been updated in a long time. So it is probably good that it is down.
Fox is not making engines at this time and they are out of parts for everything too. They might go back to making engines if the conditions improve in the future though.
Fox is not making engines at this time and they are out of parts for everything too. They might go back to making engines if the conditions improve in the future though.
07-08-2015, 04:16 PM
#4183
Even the crappiest 4-strokes are nice, IMO.
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07-08-2015, 05:57 PM
#4186
I meant the 4-2-4 setting for control line stunt. I just have one 4stroke, yes a surpass .90 as well. It is ok, I just seem to like the little .15s. They scream at you instead of farting around. Ya I know I am a minority.
07-08-2015, 08:06 PM
#4188
I have a fox 74 sitting around and I was wondering if it would be a good candidate for glow/gas with the new OS glow plug for gas. Being that the 74 is already a fairly high compression engine, would that work? I know there is the issue of port timing, etc... But what do you guys think? If I can't have a Fox 4-stroke, a glow/gas is the next thing on my list of preference.
07-08-2015, 08:11 PM
#4189
I like screaming 2-stroke glow on fast and sleek airplanes, farty 4-strokes on 3D planes and scale planes, and smelly gassers for the big planes. I seem to have lost interest in electrics. I traded off my electrics a couple of years ago and strangely, I don't miss them. At least Fox did not prostitute themselves and sold electric stuff like OS and Super Tigre did.
07-09-2015, 01:02 AM
#4190
I have a fox 74 sitting around and I was wondering if it would be a good candidate for glow/gas with the new OS glow plug for gas. Being that the 74 is already a fairly high compression engine, would that work? I know there is the issue of port timing, etc... But what do you guys think? If I can't have a Fox 4-stroke, a glow/gas is the next thing on my list of preference.
07-09-2015, 04:50 AM
#4191
You woujld lose too much power using gas, especially when the engine is timed for glow. If you mix your on fuel you don't really save that much anyway. When all gas powered planes were large I used to chuckle when the owners claimed it was cheaper than my smaller glow planes because the gas was cheaper. Then over the course of a season they would completely destroy one or more. Even if the engine and other gear is salvageable the cost of the crash would more than offset the cost of fuel.
07-09-2015, 11:27 PM
#4192
If you check the exhaust timing you see why they are so timid, I guess they were only meant to be sports engines. It is a little strange when they have the large machined transfer ports and double BB etc. I haven't tried, but it might be worth reworking the exhaust timing a little and changing the muffler for something with a little more volume. A clamp-on header might fit, rather than using the angled screws for the exhaust.
07-10-2015, 03:22 AM
#4193
If you check the exhaust timing you see why they are so timid, I guess they were only meant to be sports engines. It is a little strange when they have the large machined transfer ports and double BB etc. I haven't tried, but it might be worth reworking the exhaust timing a little and changing the muffler for something with a little more volume. A clamp-on header might fit, rather than using the angled screws for the exhaust.
Last edited by 1QwkSport2.5r; 07-10-2015 at 03:28 AM.
07-10-2015, 05:30 AM
#4194
If you check the exhaust timing you see why they are so timid, I guess they were only meant to be sports engines. It is a little strange when they have the large machined transfer ports and double BB etc. I haven't tried, but it might be worth reworking the exhaust timing a little and changing the muffler for something with a little more volume. A clamp-on header might fit, rather than using the angled screws for the exhaust.
07-12-2015, 09:43 PM
#4195
aspeed,
You may be able to reduce pre-igniting with another head gasket (spacer?) or two. Unless you have really important reasons for a specific shape to the upper combustion chamber, raising the deck clearance should not cause problems. Some of the turbo threaded buttons I've seen had little meat to carve away outside the plug threads, but if there is some such space, rounding it from its squish surface to nearer the actual threads, might work.
Years back, I "tamed" a large frame Fox 40 Schneurle BB Schneurle by cutting a conical taper into the button, from full stock depth at the cylinder wall to the end of the plug threads. Much smoother running. Didn't seem to cause much if any power loss. That was my first stunt engine that I used in all-2-cycle mode, wet, low in the extended 2-cycle RPM range. (a mode which has become fairly popular for CL stunt using RC-based ABC/AAC/ABN engines since.) Improved economy, too.
Button cut to a broad conical hat shape (coolie hat?). It somewhat resembles the cone form in shaped-charge explosives, which direct the explosive force pretty much straight-line, towards the 'target' surface. Before I increased combustion chamber volume this way, the head button showed a charred 'bowl' and little evidence of exposure to combustion products or heat across the squish face. After, the entire conical surface had a pretty uniform light yellow tint, probably hot castor residue short of charring.
I think its reduced vibration was due to the difference between the stock squish and bowl form and the broader, open slightly reduced compression ratio conical head. The engine was/still is very sturdy. The ring benefitted from an occasional (every 75 flights or so, or when cold compression seemed to drop a bit) brief bench run on a small prop at higher RPM to break any cyl wall glaze and 'exercise' the ring in its land and make sure it remained clean and properly free. Logged several hundred 8 minute CL stunt flights on it, then the model broke.
Just a thought...
As far as glow/gas... tried it once on an old Fox 19. Needle was very critical, wouldn't keep running unless the plug stayed connected, entire engine got much hotter than on glow fuel.
Possible reasons:- As mentioned the range of fuel/air ratio tolerated by gasoline is much narrower than for methanol fuels. Glow plug metals may not be the best catalyst to ignite the gasoline/air charge? Methanol evaporative chill DOES assist cooling, gasoline apparently doesn't, or does to much less extent. Port volume rework to fit flow to the smaller weight of gasoline that would match the engine's breathing capacity could help, too. (Similar problem with kerosene-base 'diesel' fuels in designed-as glow engine conversions.)
And that's another problem - gasoline yields about twice as much combustion heat per unit of weight, when burned properly, as methanol does. Methanol can tolerate, and run well, on fuel/air ratios several times as rich as the more critical gasoline. THAT limit on how much gasoline we can burn well could turn out to mean there's NO power benefit to running a gasoline/oil fuel. (And gasoline is much more dangerously flammable than kerosene, and open flames seem hotter than for methanol...)
You may be able to reduce pre-igniting with another head gasket (spacer?) or two. Unless you have really important reasons for a specific shape to the upper combustion chamber, raising the deck clearance should not cause problems. Some of the turbo threaded buttons I've seen had little meat to carve away outside the plug threads, but if there is some such space, rounding it from its squish surface to nearer the actual threads, might work.
Years back, I "tamed" a large frame Fox 40 Schneurle BB Schneurle by cutting a conical taper into the button, from full stock depth at the cylinder wall to the end of the plug threads. Much smoother running. Didn't seem to cause much if any power loss. That was my first stunt engine that I used in all-2-cycle mode, wet, low in the extended 2-cycle RPM range. (a mode which has become fairly popular for CL stunt using RC-based ABC/AAC/ABN engines since.) Improved economy, too.
Button cut to a broad conical hat shape (coolie hat?). It somewhat resembles the cone form in shaped-charge explosives, which direct the explosive force pretty much straight-line, towards the 'target' surface. Before I increased combustion chamber volume this way, the head button showed a charred 'bowl' and little evidence of exposure to combustion products or heat across the squish face. After, the entire conical surface had a pretty uniform light yellow tint, probably hot castor residue short of charring.
I think its reduced vibration was due to the difference between the stock squish and bowl form and the broader, open slightly reduced compression ratio conical head. The engine was/still is very sturdy. The ring benefitted from an occasional (every 75 flights or so, or when cold compression seemed to drop a bit) brief bench run on a small prop at higher RPM to break any cyl wall glaze and 'exercise' the ring in its land and make sure it remained clean and properly free. Logged several hundred 8 minute CL stunt flights on it, then the model broke.
Just a thought...
As far as glow/gas... tried it once on an old Fox 19. Needle was very critical, wouldn't keep running unless the plug stayed connected, entire engine got much hotter than on glow fuel.
Possible reasons:- As mentioned the range of fuel/air ratio tolerated by gasoline is much narrower than for methanol fuels. Glow plug metals may not be the best catalyst to ignite the gasoline/air charge? Methanol evaporative chill DOES assist cooling, gasoline apparently doesn't, or does to much less extent. Port volume rework to fit flow to the smaller weight of gasoline that would match the engine's breathing capacity could help, too. (Similar problem with kerosene-base 'diesel' fuels in designed-as glow engine conversions.)
And that's another problem - gasoline yields about twice as much combustion heat per unit of weight, when burned properly, as methanol does. Methanol can tolerate, and run well, on fuel/air ratios several times as rich as the more critical gasoline. THAT limit on how much gasoline we can burn well could turn out to mean there's NO power benefit to running a gasoline/oil fuel. (And gasoline is much more dangerously flammable than kerosene, and open flames seem hotter than for methanol...)
07-13-2015, 03:28 AM
#4196
The combustion chamber shape is really what one tunes the fuel to - the conical shape is condusive to higher nitro (not only the larger volume of the head, but the shape more so) as is a narrow squish band. A more hemispherical shape with a wider squish band is more condusive to lower nitro. This is all assumed with a tight head spacing of around .012"-.015" or so. This is based on what I've been told over the years - it very well could be BS. I tried running a .015" head spacing on an engine with custom made head buttons based on the suggestion of an "expert" and it resulted in a bent rod from being over compressed. An electric starter wouldn't have a chance starting it either. YMMV.
FWIW, I later sold said engine that had custom buttons made for it to the "expert" who drew up the "perfect" head button design for said engine. He threw me under the bus for every problem the engine had when it was sold to him "as-is" and as a "parts" engine. The morale of the story is be careful who's advice you put into practice.
FWIW, I later sold said engine that had custom buttons made for it to the "expert" who drew up the "perfect" head button design for said engine. He threw me under the bus for every problem the engine had when it was sold to him "as-is" and as a "parts" engine. The morale of the story is be careful who's advice you put into practice.
Last edited by 1QwkSport2.5r; 07-13-2015 at 03:34 AM.
07-13-2015, 05:01 AM
#4197
The combustion chamber shape is really what one tunes the fuel to - the conical shape is condusive to higher nitro (not only the larger volume of the head, but the shape more so) as is a narrow squish band. A more hemispherical shape with a wider squish band is more condusive to lower nitro. This is all assumed with a tight head spacing of around .012"-.015" or so. This is based on what I've been told over the years - it very well could be BS. I tried running a .015" head spacing on an engine with custom made head buttons based on the suggestion of an "expert" and it resulted in a bent rod from being over compressed. An electric starter wouldn't have a chance starting it either. YMMV.
FWIW, I later sold said engine that had custom buttons made for it to the "expert" who drew up the "perfect" head button design for said engine. He threw me under the bus for every problem the engine had when it was sold to him "as-is" and as a "parts" engine. The morale of the story is be careful who's advice you put into practice.
FWIW, I later sold said engine that had custom buttons made for it to the "expert" who drew up the "perfect" head button design for said engine. He threw me under the bus for every problem the engine had when it was sold to him "as-is" and as a "parts" engine. The morale of the story is be careful who's advice you put into practice.
). Regarding head buttons and combustion shapes, why is it that the big gassers don't deal with that? Those big gas engines are nice with a one-piece cylinder/head and some are liner-less. Can't glow engines be designed and built that way? Seems to allow the engine to ligher, sturdier, and fewer parts count. Plus you get better head dissipation without a liner and cylinder to head interface.
07-13-2015, 05:19 AM
#4198
Yeah, I put more time into that engine than it was worth. I don't care what he says, that engine was a novelty at best. Hardly an economical solution for a large scale plane today. Back in the 80s it might be different. The head buttons took half a day to make and would never have worked as the drawing was made. The engine was way overcompressed. If I knew then what I know now, I'd have made the heads with about .035" head spacing. I went off what the "expert" said to do. Whatever. It's his problem now.
The higher parts count on modern engines probably has to do with repairability in the event of a crash. If you break a bunch of head fins, replacing just the head or head clamp is a lot cheaper than replacing the whole cylinder jug/head. It adds weight, but a cheaper repair. Modern gasoline engines that make the cylinder/head one piece is a production cost thing. Cheaper to make in one piece. Most of our glow engines weren't designed for a price point but form and function. Most gasoline engines are made to a price point. IMO.
The higher parts count on modern engines probably has to do with repairability in the event of a crash. If you break a bunch of head fins, replacing just the head or head clamp is a lot cheaper than replacing the whole cylinder jug/head. It adds weight, but a cheaper repair. Modern gasoline engines that make the cylinder/head one piece is a production cost thing. Cheaper to make in one piece. Most of our glow engines weren't designed for a price point but form and function. Most gasoline engines are made to a price point. IMO.
Last edited by 1QwkSport2.5r; 07-13-2015 at 05:21 AM.
07-13-2015, 05:31 AM
#4199
Sounds like you put in a lot of time and efffort into that junk pile. I was beginning to get into some engine projects, not head buttons but pumps and regulators, and I think I am going to quit that idea. I would rather go flying instead (and repair the planes I crashed ).
Regarding head buttons and combustion shapes, why is it that the big gassers don't deal with that? Those big gas engines are nice with a one-piece cylinder/head and some are liner-less. Can't glow engines be designed and built that way? Seems to allow the engine to ligher, sturdier, and fewer parts count. Plus you get better head dissipation without a liner and cylinder to head interface.
). Regarding head buttons and combustion shapes, why is it that the big gassers don't deal with that? Those big gas engines are nice with a one-piece cylinder/head and some are liner-less. Can't glow engines be designed and built that way? Seems to allow the engine to ligher, sturdier, and fewer parts count. Plus you get better head dissipation without a liner and cylinder to head interface.
07-13-2015, 05:34 AM
#4200
The one piece head/cyl. is a great idea. Just a bit hard to machine with a lap. It would be hard with ABC, but ringed could work alright. Th Russian motors all seem to have a screw in button, much like the Cox, which gives a good seal. I think this is a performance gain over the stepped head which seems normal in the last 50 years. My Fora has kind of a double bubble combustion chamber shape. Very shallow. That is what made me think about changing the Fox .15, as it was a deep bowl with .040" headspace. The Fora was quite a bit higher compression (they seem to thrive on 30,000 rpm too) I have noticed the better 1/2A heads seem to use just a chamfer shape from the plug bottom to the squish band. It really made my one little CS .049 sing compared to the Nelson plug head that I made 25 years ago. I have been thinking of maybe trying a head made of a material that expands faster than the brass liner, so it seals better when hot. The aluminum heads normally used would tend to be looser IMHO. I think running gasoline is hard, but could be diluted like some of the Glow/Gas mixtures of 1/3 glow to gas. I will stick to glow thanks, it doesn't stink up your fingers for a day when you spill some. I can mix my own if needed for economy if I can find the cheap methanol I keep hearing about. The oil seems like the expensive part, especially at 20%. Other than economy, I see no reason to use gasoline, and I seem to enjoy the little motors better than the gassers. Yes I am a minority. Hmm, it seems like everyone types at the same time in the morning after breakfast.