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Fox .45 diesel engine conversion

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Old 05-30-2011, 06:32 PM
  #1
earlwb
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Default Fox .45 diesel engine conversion

The weekend holiday here has been something of a wash due to the high wind speeds. It make it not worth trying to fly a RC model when the winds are 25mph and gusting to 40. So far this year, it has been super windy all most all the time. Especially on my time off.

So today, I took care of my RC fix needs and bench ran my venerable 1980's vintage Fox .45 wart engine. I had actually bought the engine fromFox many years ago when I visited their Fox Manufacturing factory in Fort Smith, Arkansas. It was a new engine, so I bench ran a few tanks of fuel through it to limber it up some and run it in for a while too. Then I put on my old style Davis Diesel Head so it could be a diesel engine now. I also replaced the old style butterfly carb with a new editionFox carburetor as well, as the new Fox 2 needle carb works really nice.

I am pretty impressed as to how well the Fox .45 engine ran as a diesel engine. It idled really well considering I hadn't added muffler pressure to it yet. It tended to be a little sluggish on the run up from idle, but I think that was more a function of it having to spin up the big heavy Haster Airscrew 12x8 propeller though. It might be a touch too rich on the low end, but it still ran pretty good as is though. The new Fox carb worked great.

When I first got ready to run the engine, I unscrewed the adjusting screw on the head, as it seemed to be down really low into the head. But when I started trying to start the engine, I would screw in the screw a little at a time, and eventually I wound up having the screw pretty much back to about where it was when I first opened up the package.

As a glow engine it turned a 11x6 Master Airscrew prop at 12,400 RPMs. As a diesel engine it turned a 12x8 Master Airscrew Prop at 9,400 rpms. It would idle as low as 2,100 RPMs well too. I used Davis Diesel fuel as well. I have a video clip of it running, but it is going to take a long time to upload it though. So I'll post it later, if anyone is interested.
As another thought, my old Saito .80 four stroke glow engine turns a APC 12x8 prop at a little over 10,000 RPMs, so the Fox .45 diesel is developing some pretty good power there in comparison to a larger 4 stroke engine.





















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Old 05-30-2011, 06:57 PM
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Default RE: Fox .45 diesel engine conversion

Good job Earl, I need to get a couple of those new carbs.
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Old 05-30-2011, 07:54 PM
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Default RE: Fox .45 diesel engine conversion

Looks like quality is ageless, and very powerful 45 conversion, sure Earl is happy with this one martin

Do not know what camera he is using pix are great too they leap off the page
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Old 05-31-2011, 02:53 AM
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Default RE: Fox .45 diesel engine conversion

Eghad, I see Phillps head screws on it Earl, you'll have to lose those quick.
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Old 05-31-2011, 03:04 AM
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Default RE: Fox .45 diesel engine conversion

Yeah those Phillips head screws were standard stuff way back then on the engines.

I am using a Panasonic Lumix Digital Camera, a older 8 megapixel version. It can take closeups and videos as well along with image stabilization.
I then use a image editor to shrink the pictures to 640x480 so as to not overwelm anyone still using dial-up. On some closeup pics I select a block and copy it to a new image, so that I can blow up the size of the smaller item to make it look like I took the pic a inch away from the object.

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Old 05-31-2011, 03:37 AM
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Default RE: Fox .45 diesel engine conversion

Earl, every time I see something like this my mind goes into the comparo mode. That .45 is pretty strong, my .50 turns a Graupner at 9,650.
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Old 05-31-2011, 04:04 AM
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Default RE: Fox .45 diesel engine conversion


This was the peak RPMs I recorded at the time. I think it will improve after the engine gets run in real good.



Here is a video clip of me messing around with the engine:

[youtube]http://www.youtube.com/watch?v=WTp3Lkr9pSw[/youtube]

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Old 05-31-2011, 08:32 AM
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Default RE: Fox .45 diesel engine conversion

That's very good and will improve as you say. I'll bet its smooth as silk too. Does that .40 have a crankpin that is a little smaller than the .50s crankpin. Thanks, Dave
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Old 05-31-2011, 09:35 AM
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Default RE: Fox .45 diesel engine conversion

it is hard to say, I don't think so. But the engine was a 1975 design large case engine. it first came out as a .40, then later they bored it out to a .45 and it was offered as a .40 and a .45 for a long time. The first engines had the shiny silver aluminum look to them. Later Fox started bead blasting the engines to give them the gray color look. I think that was in response to the Japanese engines at the time having the bead blasted gray look to them as well. The early engines had the two muffler mounting holes about 2mm closer together than the later models did. So you couldn't easily use the newer versions mufflers. Then in the late 1980's or early 1990's Fox came out with the .50 engine. In these cases they simply kept boring out the engine crankcase to accommodate the larger cylinder sleeves (and change to the head button of course), but everything else stayed the same. Later as the molds wore out, Fox changed the molds to what we see today with the engines. They incorporated the side port on the engine better and opened it up more, so it didn't have the "wart" like bulge on the side. I have some vague memories of Fox changing the crankshaft and stuff when the molds were changed on the newer ball bearing engines, but I can't be certain. I haven't tried to mix and match the parts on the engines yet.

Now in the late 1970's and early 1980's Fox did manufacture a lower cost bushing version of the engines. This engine had a smaller crankshaft and it had a smaller crankpin as well. The connecting rod was more thin and not as wide as the ball bearing engine crankshaft. It also used a slot to help provide oil lubrication, whereas the bal bearing engines had a hole drilled in the rod for that purpose. Fox might have timed the engines a little different, but I think any timing changes was due to the smaller crankshaft having a smaller intake port hole in it.

I think the .50 engine might have been on the cusp of being too large of a bore as it impinges on the port passages making them smaller, which would affect how much air fuel can flow through the engine. The .45 was pretty close to optimum, but maybe something like a .47 or .48 would be the ultimate size to go with. So the .50 could be a bit flow challenged for higher RPM running, but it can take a larger prop than the .45 can.


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Old 05-31-2011, 12:26 PM
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Default RE: Fox .45 diesel engine conversion

I have interchanged the .46 ABC sleeve with the .50 sleeve with no issues. The .46 sleeve is thick and heavy.
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Old 04-18-2012, 03:24 AM
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Default RE: Fox .45 diesel engine conversion


Quote:
ORIGINAL: Hobbsy

I have interchanged the .46 ABC sleeve with the .50 sleeve with no issues. The .46 sleeve is thick and heavy.
Dave

Have you run the engine in this configuration? I am very interested in learning how it compares to the stock 50.

Joshua
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Old 04-20-2012, 03:00 AM
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Default RE: Fox .45 diesel engine conversion


Quote:
ORIGINAL: N99JH


Quote:
ORIGINAL: Hobbsy

I have interchanged the .46 ABC sleeve with the .50 sleeve with no issues. The .46 sleeve is thick and heavy.
Dave

Have you run the engine in this configuration? I am very interested in learning how it compares to the stock 50.

Joshua

Hi Dave

This posting of mine may have gotten lost in the shuffle. Can you please comment on how the engine performed with the .46 sleeve? I assume you also used an ABC piston in the set-up?

Thanks
Joshua
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Old 05-14-2012, 11:36 AM
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Default RE: Fox .45 diesel engine conversion

I have a 1980's vintage Fox .45 and want to put a Davis Diesel conversion head on it.
I contacted Bob Davis and he tells me that they no longer make that head.
Is there anyone out there who has one for sale?
Does anyone know of a source for a Fox .45 Diesel conversion head?
JoeJ


















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Old 05-14-2012, 11:40 AM
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Default RE: Fox .45 diesel engine conversion

Earl,

I'm looking for a Davis Diesel convesion for my 1980's vintage Fox .45.
Bob Davis tells me he no longer offers the product for the Fox .45.
Where did you get yours?
JoeJ
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Old 05-15-2012, 03:14 AM
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Default RE: Fox .45 diesel engine conversion

Quote:
ORIGINAL: jeffrey_joe
Earl,
I'm looking for a Davis Diesel convesion for my 1980's vintage Fox .45.
Bob Davis tells me he no longer offers the product for the Fox .45.
Where did you get yours?
JoeJ
I got my DDD head off of Ebay a few years ago.

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