controlliner

Duke chose mehanite for pistons and leaded steel for liners, on purpose as they have expansion coefficients that are nearly identical.

Sport_Pilot

Not a heck of a lot of variation between the iron alloy's. Mostly because all but the stainless steels and expensive alloys are all mostly iron. Where as aluminum allows might have as little as 50% pure aluminum and bronze and brass alloys might have less than 50% copper. If he could have afforded a higher tech alloy he probably would have use a material with a higher expansion rate for the piston or a lower one for the sleeve. With the same rate the gap between piston and sleeve grows larger.

Lou Crane

Sport Pilot and controlliner,

Our discussions of the concepts of metallurgy may be rather simplified.

Alloys of iron show great and varied results from fairly small additions of other substances. Aluminum has very different possibilities and can accept larger alloy material %s.

When Duke settled on Meehanite and leaded steel the advanced techniques of alloying aluminum either had not yet even been tried or were still in the development of the technology, and of the precision processes needed to get it to work reliably.

One great gain in using aluminum alloys is the weight reduction possible. Reciprocating weight is a major factor in single engine vibration. Aluminum pistons with (cast) iron rings were used 'back then' but were more costly than producing simply machined piston/sleeve pairs.

Other difficulties existed, too. Rings wear and need occasional replacement, for example. Those rings often showed slack compression at prop flipping "RPM." Their seal relied on the compression and power forces 'blowing' the ring working surface into contact with the sleeve. Broken rings could and did cause major damage. Ports needed to be bridged - like the multiple small port windows on ringed McCoy engines. Too wide span could allow a ring to hang up on a port edge.

Dykes rings are much more supple, but still feel like slack compression seal on hand flipping the prop. They also wear and are subject to damage or distortion.

Metallurgy advances help most of the problems, but still need to be used "properly." Definite advantages, AND they usually include less messy exhaust deposits on the models.

Besides, we are used to replacing rather than repairing. Easier, and not much more expensive - considering the cost of replacement parts...

Aaron L.

Very interested. PM sent.

Sport_Pilot

Varied results, but not great. Iron alloys such as low carbon steel, leaded steel, and cast iron only vary about .0005 in/deg F.

hsukaria

I am looking for a throttle barrel with a 0.29 venturi (if not available, I'll take a 0.312) for a MKx carb. Would anyone happen to have a spare to sell? This is for another Fox 45 I recently purchased.

hsukaria

Updates on my Fox project engines:

The compact 40 that had overheated due to dirt behind the prop driver on a hot day has been successfully run on the bench. I did replace the glowplug too. I had drenched the engine with transmission fluid to flush out the dirt, but I think that caused some tuning and glowplug issues even after cleaning out most of the oil.

The Fox 45 with excessive axial movement of the crankshaft is mostly disassembled. I had tried all the tricks to loosen it. In the end, I had to freeze the engine, then heat the prop driver with a torch, AND pull it out with a modified battery terminal puller. However, the crankshaft was still not passing through the main bearing, so I heated the engine and the crank and front bearing came out. However, the main bearing won't budge. I am re-heating it in a crockpot with antifreeze to see if it would come out this evening. I have never worked on an engine that was so tight. The engine was coated with castor varnish everywhere. Any tricks to removing the main bearing? I have replaced bearings on other engines before, including a Fox 74, but this 45 has been the toughest so far.

I will order the bearings today for the Fox 45. Any recommendations? I would like to have a shielded front bearing to reduce the messiness a little.

Determined in Detroit.

aspeed

I made a bearing remover tool in desperation one day. Others are like a collet and commercially available. Maybe for a Jett or something? It was for an old crusty Supertiger .40 that was used in combat. It is shown on an OS just to see. I naturally heated up the case and gave it a good cleaning with carb spray first. It was nasty, and I should have left the motor on the garage sale table. I did get a couple other SPAD combats with good motors though.

hsukaria

Unfortunately, there is no way i can use a tool on the main bearing. The inner race is flush with the forward crankcase. I will have to get it somewhat loosened and slam the back of the crankcase on a piece of soft wood. I am hoping that the impact will pop it loose. If that doesn't work, I will freeze the engine with the bearing in it and then heat the crankcase. That is my next step.

1QwkSport2.5r

Get it hot. If the oil isn't smoking, it's not hot enough. I've had some engines that were really glued in good from oil varnish. Heating it up good and hot and giving a few good whacks on a piece of wood did the trick. I've been using a heat gun capable of 1400F on he really hard ones. In rare circumstances, a propane torch may do the trick. One must use caution using a torch - getting the aluminum too hot can distort the case.

hsukaria

I have been using a heat gun for heat shrink covering. But I also have a paint stripping heat gun that is a lot hotter. That could be an option if all else fails.

I just ordered the bearing set from Boca Bearings, part # ENK-037. No sense paying extra for stainless or ceramic.

aspeed

I heated and banged on wood until I was blue in the face. This tool grabbed between the chamfers in the bearing and the case. It was really stuck in good in that case. The carbon hardened on the lip of the case not allowing the bearing to slide out.

hsukaria

I guess that is a disadvantage of using castor oil over the long run, you get all that buildup inside the engine, making it hard to disassemble.

hsukaria

I am also looking for a tilt-down muffler for a C-case Fox 40 if anybody has one to sell.

1QwkSport2.5r

I think I have a brand new one..

Sport_Pilot

Well I guess you don't have to worry about forgetting to knock on wood for a while.

hsukaria

Do you need it or are you willilng to sell it? If so, how much?

1QwkSport2.5r

I don't need it - the tilt down mufflers don't fit my test stand and I'd use a quieter muffler anyway.. Let me see if I still have it and I'll send a PM when I'm off work.

hsukaria

Ok thanks

Those mufflers are really loud but my MACS one-piece muffler with adapter plate doesn't work. It interferes with low speed needle and shakes loose if you have a not rigid enough engine mount.

hsukaria

YAY!!! I got that 45 main bearing out finally. I had to resort to making an extraction tool similar to aspeed's. I froze it, I heated it (but not as much as others suggested because I was worried of damage), slammed the case against wood. But all it did was move a little, enough to be able to wedge this tool into the tiny gap and tap it with a mallet. Only 2 small mallet taps removed it. I am expecting the new bearings to show up tomorrow.

Aaron L.

Good job! Adapt and overcome.

hsukaria

Actually, that screwdriver had a damaged tip before I modified it. I did not sacrifice a good tool for this. It was already bad.

fiery

My Feedback: (2)

Nice solution.

wnewbury

I'd like to buy a part for a late production Fox 46 RC. The drive "washer" that touches the rear of the propeller. The inside is tapered to go over a split "collet". Thanks.

hsukaria

I received the new bearings for my Fox 45 from Boca Bearings yesterday. I knew I was getting a shielded front bearing, but the main bearing also came shielded. Is it ok to have both bearings shielded on both sides? If not, how easy is it to remove the shields on the main bearing? Also, can the front bearing be shielded on both sides? Thanks.