Mr Cox

The Norvel is stronger than the OS...

The stock carb is very restrictive on the Norvel. The actual bore is fine but the spray bar in the center is comparatively large. This give a great idle (around 2500rpm all day) but it also limits the top end. The MVVS .15 carb is direct drop-in though and will give you an extra 1400rpm or so at the top, mine went from 14400rpm to 15800rpm on an 8x4 prop. The only other .15 engine I have that can rival that is the Cox Conquest.

AndyW

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That reminds me that the Norvel .25 throttle is a drop in for the .15. Could it really be that the Norvel .15 was just under throttled? I routinely bore out throttle barrels for more power. Occasionally that causes the need for some throttle tweaking but not always.

Gosh darn test stand, wish I could find it, that would allow testing each engine, one after the other allowing same day, same temps, same humidity conditions. This may have to wait till I make another. Cr*p.

PS,

What brand of 8 X 4 ?

aspeed

My Norvel BB .15 really woke up with a bigger control line carb I made up. I ran it with no muffler to make sure that it was really just the motor for comparing other motors. I tested a bunch of .15s and .09/.10s in the Tachometer Reading section about a year ago. It was a windy year, and I needed to hear some noise. I used a 7-5 Master Airscrew because that is what I normally use, and 10% fuel

Mr Cox

There have been report also of misaligned exhaust ports and restrictive mufflers. Japan man worked and wrote about that sometime ago. On my engine the muffler didn't have any baffles and there was no obstruction from the crankcase at the exhaust either. The only "error" I found was the carb being too restrictive from what we are used to. It does give the engine a great throttling and super stable idle, but comes with a sacrifice at the high end.

The figures given earlier were all on the APC 8x4, with 10% nitro and 20% all castor in the fuel.

Pond Skipper

Alan did you ever do anything to the Thunder Tiger GP -10 ? I recall muffled it only put out 13.5k on the MA 7x4
I have one myself too bad no bearings, spec sheet states practical RPM: 2,500 ~ 18,000 - 0.27 BHP / 17,000 RPM

GREG DOE

AndyW. Just to jog the old memory, yours and mine. Super Fuel was a Fox product, NOT Cox. Cox sold fuel in a blue can, and fuel in a red can. So guess what, we all called it Blue can, or Red can. I believe the blue can was 25% nitro, and the red can (Cox Racing Fuel) was 50%. I'm enjoying following this thread. You guys keep up the flow of information. At Henry Nelson's suggestion I put a Mac Wizard muffler (part # 1820) on one of my Nelson .15 rear exhaust engines. I don't think it helped, or hurt, but might benefit from raising the exhaust trimming.

aspeed

I played a bit with my TT .10 and .15 The .10 would barely get my plane off the ground if it wasn't leaned out all the way. It had standard size servos. It wouldn't respond much to the turbo head I made for it either. I spent a lot of time on it, and it was a dud. I am not real happy about the TTigers at all. My .07s were pretty slow too, although 2 of the three picked up well with the turbo head. Still one was a dud. They were all used though. Idle was great on all of them. I had an old TT .25 that would not hold full throttle too. My .40 Pro seems good just on a run up on the plane though.

aspeed

There was a club in Ajax that raced a sport club type pylon using .15 to .25 motors. The .15 seemed quicker according to the one gentleman I talked to. He seemed to favour the LA .15 with a drilled out exh. stinger. I have drilled out most of my mufflers that seemed small on a lot of motors. I also turn or grind an undercut so I can mount a slobber collector on the end of the muffler. Just something I do. The .10 and .15 muffler has a baffle in which I bored completely out on about half of them. I would post results, but I will not have time for a few months, as a big move and construction project is under way. I may be able to sneak something in on the long weekend when the boss/wife is away, I will see. I got a Supertiger G .15 I want to run up too.

Mr Cox

The GP series from Thunder Tiger is a bit of a dissapointment I think, the BB Pro version are better but they only make, or rather made, them in larger sizes.

The older classic cross scavaging ones, with baffle on the piston, are not too bad though in terms of power to weight ratio. I have one of the .15 ones that does 14200rpm on the APC 8x4 prop, while the total weight is a about the same as the OS .10FP engine...

AndyW

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Thks Mr Cox,, OK with a bigger throttle and an APC 8 X 4, just under 16K is something to shoot for. Thanks to all for the great comments, much to ponder.

So, I detect that the bearings have a bit of drag in them. Time to replace, before running to make all things equal if we're going to compare to the other brands. So, I take the Taipan apart.

Well, I'll be an uncle's monkey. It's an iron/steel engine. ??? Who would think that this metallurgy was applied to true Schneurle porting? That it delivers the goods, despite that, says a lot for Taipan's engine design. Shoot, that was in 1972 when it came out. Were ABC Schneurle engines readily available back then?

BUT, Mr. Burford used PHILLIPS head screws. Predictably, I mucked up two on the head. Usually, I'll use a Dremel disc to make a slot. But this time, I didn't want to mess up that beautiful head, I tried something new. I used a carbide, round burr, to take out the Phillips slot. A suitably sized drill is then used to take out the screw head. Worked a treat.

Now to get new bearings and put her back together.

Greg,

You're right, yes, FOX Superfuel and the term Racing Fuel from Cox resonates. I may even have an old, (empty) can somewhere. Many thanks. So, with 50% nitro, no wonder my Babe Bee loved it. Of course, they didn't give you the nitro content on the can, so we thought that maybe Cox fuel was superior. It may have been and used AAA de-gummed Castor (25%) that gave us that true, sweet smell of burnt Castor oil. I haven't experienced that in a very long time. It sure would be nice to find an old, unopened can.

MJD

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The Cox fuels were 15% and 30% respectively. Fox Superfuel is a gooey concoction of 5% nitro, 29% castor oil (I've seen it listed as 28% and 29% - it's one of those anyways).

GREG DOE

MJD Thanks for the clarification on the Cox fuels. AndyW, Have you ever tried left hand drill bits? You would be amazed at how easily you can remove damaged screws. In practice you start a hole in the screw head, and then bear down hard enough to make the drill "bite" hard, and it will usually back the screw out. Worse case is, you drill the head of the bolt. Left hand bits are a little hard to find. I have a selection of 4 in the 3/32" to 1/4" range. I've had them for 30 years, and even used them on some stubborn screws when I restored my '57 Chevrolet.

AndyW

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MJD,, gooey is right.

Back in the day, 25% and more oil was the norm. I suppose that's because of tighter fits and ferrous technology. You were required to carefully break in your engine for that oh so perfect fit. Best result was with a highly polished look on the cylinder, like a mirror,,, at least Cox engines.
Curiously, the Taipan doesn't have that. Looks like no break in necessary was the goal by Mr. Burford. Personally, I like to get a slightly tight fit. The MP Jets, steel/iron was done that way to the point of overkill.

Greg,

I can get left hand drills and that sounds like a great idea. Many thanks.

Japanman

Hi Andy!
It's great to see you back, I had been wondering what you were up to.
I am, of course, very sorry to hear about the passing of your family.
I hope to see more of your experiments up soon.
regards,
Stefan

Cross Check

Hi Andy,

I knew it would not take any time for you to 'check the innards' of the Taipan !

Were there any Head shims?
I long forget...

The castored piston looks 'broken in'... to me !

New bearings might give it a chance against the OSFP !

Have fun Andy !

Cheers,
Dave'crosscheck'Fallowfield

AndyW

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Thanks Stefan. To be honest, it's a struggle but it IS still early summer. Seems I do best in the fall, though, cooler weather, longer nights for the shop and well, the beach beckons a lot. My haven during the hardest times, go for a vigorous swim float in the middle of the lake taking in gobs of clean, northern air. After a swim I feel more energized than drinking a strong cup of coffee. Amazing what oxygen can do for you.

At this latitude, we have daylight until 10PM at the peak and the still evening air takes me out to the park for some late flying sessions. I got back from the field just an hour ago, flying, an EFlite Mustang. Yes, I have dipped my toe into the wacky world of electrics. This one has an under cambered wing,, yuck,, so I got a spare wing set and made the wing fully symmetrical by gluing a left wing panel to the right wing, (on the bottom and vice versa. As soon as I get a video done, I'll be posting that to my YT channel.

Not to worry though, I've got projects bagged, waiting to be tackled.

AndyW

My Feedback: (1)

Hi Dave,

Well, if I hadn't detected the drag in the bearings, Ida just run the dang thing but you got to be fair to compare so with a new, BB Norvel and bushed LA and FP, just the right thing to do.

One head gasket, actually, and it's pretty thick at .020"

About the piston. Yes, I wouldn't argue with success. The fit seems perfect with no break in required, a rarity for the time, Mr. Burford knew what he was doing. A lot like Cox where Leroy invented machines that gave fits that didn't need but a bit of run in. Amazing guys, those two, we owe a lot to their genius and inventiveness.

hllywdb

I still mix up 30% castor fuel for my 60's era motors. The metallurgy requires it. Break ins were painfully slow and slobbering rich at first. The term "4 cycle" is common. I recently replaced the motor on my grandfather's Lou Andrews H-Ray with an identical 1969 OS 30 that I came across NIB. I broke that one in on the bench as I saw no good reason to subject a 45 year old airframe to that much of an oil soaking. They don't produce the power of today's motors but once properly broken in they run like a Timex.

AndyW

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I agree about the steel/iron, OS engines. The one pictured is from over 50 years ago. I just happened to find it today. And it just happens to be a .15,, how cool is that?

Notable is that the case is bushed at the crank and it's as smooth as you could want, no wear at all. The piston looks a lot like the Taipan with just a 1/16th band of polished metal at the top. Compression seal is still very good.

As I vaguely recall, this one was used in the only control line plane I ever had. I can't even remember the plane but I flew it a lot and had a lot of fun with it. There is really something about the feedback you get through the lines. You really feel that you're in control. I think that was before I could afford a radio and when I could, well, there was no turning back. If I can find a picture of the plane it was in, I may just build another.

No muffler in the box but there are two, threaded holes down inside the exhaust port part of the case as though a muffler could be attached. There's also a single threaded hole in the center. I think that's when they used exhaust baffles connected to the throttle.

ffkiwi

Andy-your engine is the OS Max-III 15-probably the most numerous of all OS engines other than the Pet 099-and in production from around 1962 until 1975 (which explains why its numerous! ) Your deductions are correct-the centre hole in the exhaust is where a pivoting exhaust baffle was attached in the RC version-which was supplied minus a muffler......mufflers were an accessory in the mid 60s not part of the standard engine equipment. The two holes were for mounting the OS Jetstream muffler-which came in several sizes-the one shown here fitting the OS Max 10 and 15. It was offered with an optional extension-shown in the second pic, allowing you to fit the muffler further off from the engine for clearance. They were/are a pain to fit, as the attachment screws are located on the INSIDE of the left side (the muffler consist of two half shells plus a removable outlet-so you have to disassemble the muffler to attach it then reassemble it on the engine....needless to say it wasn't terribly popular with users, and the OS 702 muffler rapidly replaced it-this of course had an external strap type mounting, so the tapped holes in the exhaust duct became redundant...
You will also discover if you choose to look, that the engine has a counterbalanced prop driver-another OS innovation (I'm not aware of any other manufacturer attempting anything directly comparable) tried out on the Max III-15 and the contemporary Max-19 but subsequently dropped-either because it was a pain to make-or most likely because it made no difference to running at all....!

AndyW

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That's great info, thanks. I recall the 702 muffler now, strap and all.

We flew off of an old, mine tailings dam way out in the boonies. The squirrels and fox never complained aboot the noise so we didn't use mufflers. Not at first, anyway. I owe a painful, right ear to this day because of that. Ouch, hurts with any high pitch or loud noise. I wear earplugs to the movies.

I wonder if I've got that muffler somewhere,,, neat.

MJD

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I'd love to see the service life of a McCoy Red Head on Cool Power fuel..

Less than 1000 revolutions?

MJD

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Pet .099 - my first engine > Cox .049

Max .15 - my second engine > .049

The final home of the .15 was.. hmm, circa 1976 age 15?, on front of a Mini Fledgling 1/2A model, 2 channel with full size gear and a small tank, maybe 1 or 2 oz. Went great but eventually ripped the elevator off pulling out of, or trying to pull out of, a power dive.. strained itself through a tree. Oops!

ffkiwi

Here's the self same counterbalanced prop driver mentioned above-I suspect that one of the reasons they dropped it from subsequent production use fairly quickly was they tended to crack through the thin walled section on the hollowed side.-the succeeding model the Max 15-with a full depth crankcase, drop in flanged liner arrangement, used a prop driver largely indistinguishable from the later 10FSR/FP/LA and 15FP/LA series. I suppose the counterbalanced prop driver might have added some improvement in helping to assist smooth idling-the R/C version was tested in Aeromodeller October 66-and they achieved a 2000rpm idle-which for such a small engine is pretty outstanding. That same test (available on the Sceptreflight website at: http://sceptreflight.net/Model%20Eng...sts/Index.html ) also mentions-which I omitted in my previous post-that the Jetstream muffler was also available in an R/C-S model which had a pivoting circular baffle internally-which took the place of the exhaust baffle in the unsilenced version, and could likewise be connected to the throttle arm to operate as the throttle is closed to idle. [the picture I posted above is of the standard Jetstream S muffler] IIRC there were only two sizes of Jetstream-small 'S' and large 'L" I don't know what the large OS engines of the era such as the 50 and 58 used, as the 'L' Jetsream seemed to be intended for the 29/35/40 size range...
I suspect OS put a lot of R&D into their throttle designs-more than may be obvious at first glance-as Mr Cox noted earlier-and I have also commented on elsewhere-the very first OS Max 10 of 1966 has a throttle with no airbleed-nor adjustment-but idles extremely well-yet the throttle casting has a 'pip' or a bulge on the throttle housing for both a bleed hole and an adjustment screw. The most logical explanation is that OS found it wasn't necessary-and what isn't there can't go wrong or get lost.....

..

ChrisM
'ffkiwi'

ffkiwi

MJD-Peter Chinn is on record (I forget which magazine it was) as stating that OS introduced the Pet Mk3 (the final model with the full length case and drop in liner) because the crankcase dies for the Mk2 were completely worn out and 300,000 examples had been produced (presumably of the Mk2-but the figure might also have included the Mk1 as well)-that's a lot of engines!.....but not unreasonable-in the UK ED produced 300,000 ED Bee 1cc diesels over its lifetime-so those quantities are not unknown for a 'beginner's' engine [ie read 'cheap' cheerful, simple to operate and reliable-but not necessarily possessing much in the way of refinements...] I imagine the Max-III 15 probably had similar production figures......as it had about the same length of time in production as the Mk2 Pet

I had several Pets pass through my hands as a junior-over the 1970-75 period-and they were available new in my home town of Dunedin-in a rather unattractive maroon-brown box-which contrasted with the deep royal blue box all the other OS motors came in. I remember them as pigs to start when cold-and absolutely impossible when hot-but that was in the pre electric starter days-and on straight fuel! these days-show them something like a Sullivan Hornet and 5 or 10% fuel and they behave quite happily. The plain unknurled prop driver was also a bit of a pain-as nylon props seemed to slip on them quite easily.

My first R/C model was a David Boddington 'Tyro' with a Max 10 R/C up front, an Agfa 35mm film canister (all aluminium-remember them? ) for a tank and proportional rudder with sequential throttle. The odd thing-I still have the R/C gear-but absolutely no idea what became of both the engine and the model...!

Currently I have 4 or 5 Pets and the same number of Max-III 15s-plus a couple of the later Max 15, and the earlier Max-! and Max-II models-the latter reserved for Nostalgia power use. About the only thing that seems to wear out with them (given sensible use) is the rod-and I have a few spares-plus gaskets-enough to keep them operating for the forseeable future!


ChrisM
'ffkiwi'