modern vs.vintage

It seems also that old kits are still being manufactured and sold with labels that have not been updated to reflect these changes. The Jnr Ringmaster being a good example. I've seen several posts re this particular model.

Can someone help by summarizing what size motor is appropriate for the different model weight and wing area categories?

Also, a lot of what you guys talk about zips right over my head! Could someone expalin about engine "break" 2/2, 4/2 etc?

Thanks,

Chris

Ps. I've joined PAMPA so I'll get the mag, but I'm curious now!

Modern 15 - 350-400 square inches, up to 35 oz, 8-4 or 9-4 prop
Modern 20 - 400-550 square inches, up to 40 oz 9-4 or 10-4 prop
Modern 25 - 450-575 square inches, up to 45 oz 9-4, 10-3, 10-4, 11-4
Modern 35 - 550-650 quare inches, up to 60 oz 11-4, 12-4
Modern 40 - 550-700 square inches, up to 65 oz. 11-4, 12-4

This is assuming a STOCK sport-type motor like the OS FP, run as intended by the manufacturer. Most re-works are intended to improve the run characteristics at low revs (to better match with the older engine sizes and run characteristics).

Most old stunt planes are designed to be run with vintage motors like the Fox 35. This is about the same as a 20. A Twister/Banshee, example, flies very well (way better than with a Fox) using a 20 or 25 FP. A Ringmaster, needs about a 15FP. I don't know of any modern motors appropriate for a Jr. Ringmaster. If I had to build one, I would be sorely tempted to lighten it up as much as possible, and use a Norvel .061 or similar. Stock, I think it's too heavy for the Norvel, and way too heavy for it's size.

>Also, a lot of what you
>guys talk about zips right
>over my head! Could someone
>expalin about engine "break" 2/2,
>4/2 etc?
>

You can set a 2-cycle engine (the normal kind) so rich that it misses every other cycle, actually running in a 4-cycle. If you work it right, you can make it fly around in level flight just 4-stroking, and then when you start maneuvering, the extra load makes it start running in a 2-stroke. The added power tends to keep the airplane from slowing down as much as it would have if the engine ran at constant power. George Aldrich popularized this way of running in the late 40's/early 50's, and it was the most common way of running engines until the 90's.

It depends on the fact that the propeller transmits loads to the engine. There's a lot more resistance to turning on the prop when the airplane slows down than when it's at full speed. This load difference changes the run characteristics of the engine.

In the 90's this method was replaced almost completely by tuned pipe engines. The pipe creates a similar effect without necessarily requiring the 4 to 2 stroke transitions. The pipe boosts the power, but only at a particular RPM. If you run the engine faster than this in level flight, when the load on the prop changes, and drags the RPM down, it puts out more power, and tends to inhibit further speed loss. If airplane speeds up, the load on the engine drops, making the rpm rise, and the power drops, tending to inhibit the increase in speed.

An additional factor is that the piped engines are also (for the most part) designed to run at higher speeds to begin with. To get a decent airspeed from the airplane, the propellor pitch has to be less. Lower-pitched props tend to have better speed-control characteristics even without the engine helping out. This is at least 50% of the advantage that was found with piped motors.

4-strokes actually have valves, pushrods, etc, and can only run in a 4-stroke. They have the advantage of running at a very constant RPM/power, which feels nice at the handle. The optimum setup has yet to be found, with most running 5-6" of pitch or so, and a few running in the 4-5 range. The disadvantage so far as been the difficulty of adjusting it for conditions - tiny mixture/rpm changes make huge differences in the run time. And weight, which is probably not a significant factor when it's properly accounted for.

ALL, repeat, ALL, 2-stroke glow motors that I've seen will run a 4-2 break if loaded and set properly. You can even hear D Speed motors go back and forth from 2 to 4 and back if they are not set right.

The fact that a lot of schnuerle motors are not run that way is that they are so much more powerful that the break point (which for a Fox/Top Flite 10-6 on 5% nitro is around 8000 rpm) is at too high an rpm for the props you want to use. Schnuerle engines with the break point intentionally set at a usable range, like the PA61 on a muffler or pipe, click back and forth between a 4 and 2 like you flipped a switch. If you set it up like Randy says, it will do this, and most people in fact run them with a 4-2 break just like Foxes at the '65 NATS.

Just like uniflow tanks, people seem to think there's some magic potion poured into the Fox 35 crankcase mold to make it do a 4-2 break.In fact, it's just that it happens to do it at a useful rpm with a useful prop. This was not an accident, and neither is it an exclusive province of Fox 35's, baffle-piston engines, or stunt motors.

1) Where does vintage motor era end and modern begin?

2) Is a Fox .35 produced today a straight replica of a Fox .35 from 30 years ago?

3) I figured out what BB means but how about ABC?

As for the Jnr Ringmaster, it is slated to take an AP Hornet .09. I hope this works 'cos this is what I've bought! If not I guess I'll just have to keep buying and building until I find a suitable combo...darn

I suppose vintage is pre- or non-schnurle porting.

Your 09 should be fine for a Jr Ringmaster. I've seen one fly on a vintage OS 10 and it did fine.

It's not necessarily a date. "Modern" engines are the ones that are built to modern standards with modern power outputs. If you had to pick a date, somewhere in the late 70's-early 80's would be about right. The widespread use of schneurle porting, modern metallurgy. Examples are OS FP's, FSR, VF, VF, LA's or OPS SPP/SPA, or Precision Aero PA40, 51, 61, or 65. They tend to have high power outputs at relatively high rpm.

As an example of not-modern but recent motors are the Double Star, Stalker, Moki, etc. The double-star and stalker 35 and 40s tend to put out no more power (in fact usually less) than 50's-era motors like the Fox, McCoy, etc despite their superior internals. The only improvement is tolerance for low-oil-content fuels. I you run a Fox on the fuel recommended for the Stalker (16% all-synthetic), it would probably seize before it ran out the prime.

An example of not-modern and vintage are the McCoy Red Head, Fox 35, ST 46/60, Veco, etc.

>
>2) Is a Fox .35 produced
>today a straight replica of
>a Fox .35 from 30
>years ago?

Almost identical in every respect. There are a large number of aftermarket parts available to replace the head, backplate, cylinder/piston, needle valve/spraybar, to make it more like newer motors, but as delivered it's essentially identical. It's a good engine in a lot of ways, having won tons of contests in the 50's, 60's and 70's. It's a waste of time trying to run it on a profile, but in a full-fuse airplane it has a lot to offer.

Frankly, I have recommended the Fox recently to several people running Stalkers and Double Stars, since at least the examples I saw didn't have enough power to fly a Nakke and Geiseke Nobler respectively. A Fox is not a killer in these, but I guarantee Bob wouldn't have won 5 championships the way the Double Star 40 flew that Nobler!

The worst characteristics are the vibration, and the requirement for mail-order-only fuel. It absolutely, positively, requires 28% call castor oil. Going to the local R/C car, dollhouse, and "Razor" scooter store and asking for this will likely result in blank stares.

>3) I figured out what BB
>means but how about ABC?
>

"ABC" refers to the metallurgy of the cylinder/piston assy.

The Fox has an iron piston with an iron liner. When it heats up, the piston expands more than the liner, and it gets tighter and, if hot enough binds up. That's why it takes so long to break in, and you have to be so careful. One hot run, before it wears the parts to have enough clearance, and the piston and/or liner is ruined. It also requires huge amounts of oil, mostly to keep it cool. The oil carries away the heat better than the mostly-cosmetic "cooling fins". Most engines used to be made this way. The iron piston had another problem - it was heavy, and it made the engine shake tremendously.

Somebody (Mr. Garofali of Supertigre) figured that having the engine get tighter as it heats up was bad. He had the idea to use brass, which expands a lot when hot, for the liner, and aluminum for the piston. Problem is, that brass is soft and will wear quickly. He decided to chrome-plate the cylinder, which provided a super-hard wear surface. Aluminum slides on it nicely. Thus the ABC (Aluminum piston -Brass liner-Chrome). It quickly became obvious that the cylinder got hotter at the top, and so it needed to be tapered to be tighter at the top than at the bottom, so that when it heated up it had the proper clearance. The technique of being able to hone a tapered cylinder was the necessary breakthrough. If they got too hot, they loosened up, and thus did not seize.

The resulting engines (ST X29 was among the first) could be run as hot as you wanted with little chance of seizing up, and thus put out tremendous power. Additionally, they hot-restarted extremely well. When cold, they were super-tight and squeaked when you turned them over, but hot they fit much better than the older engines. A few commonly-used stunt motors still using this is the GMA-Jett 50 and 60, along with the Stalker and Double-Star, and the Thunder-Tiger OS FP clones.

Later on, someone (probably the Soviets, or someone like Bugl) figured out that if you picked your materials carefully, you could make the piston and liner expand at the same rate at the same time, so it always fit perfectly. Of course, aluminum and aluminum matched pretty well, and by picking a particular type of high-silicon aluminum, it was just right. The chrome stayed, thus the AAC (Aluminum piston, Aluminum liner, and Chrome plating). This is used in the PA motors, among others.

The most modern of all of these is another variation. Chrome is a difficult material to plate onto anything. Aluminum oxide is easier to put on aluminum, and is harder too, hence the AAO (Aluminum piston, Aluminum Liner, with Oxide (hard anodization)). I think the Norvel 15 may be the only consumer motor using this so far.

OS had a more practical solution, replace the chrome in the ABC with nickel. It's not as hard, but it's a lot easier/cheaper to produce. Hence ABN. The resulting motors are very friendly to break in, and last more than adequately long. Most, if not all OS motors are like this now, 4-strokes excluded.

An alternative to the vibration problem with the iron piston, and to obviate the need to careful fitting of the piston to the liner, there are also ringed engines. These have iron piston rings (usually one, but sometimes two) to make the tight fit, and usually an iron or chromed iron liner, and a light aluminum piston. The ST46 and 60 are like this. They run well, and the ring is easy to replace. The problem is that the ring wears out relatively quickly unless there's some magic combination of ring alloy characteristics. The result can be some inconsistencies in the running characteristics. Get a good one, and it's fine, get a bad one, and you'll have to replace it after 20 flights. This is one reason that ringed engines are mostly a thing of the past.


>As for the Jnr Ringmaster, it
>is slated to take an
>AP Hornet .09. I hope
>this works 'cos this is
>what I've bought! If not
>I guess I'll just have
>to keep buying and building
>until I find a suitable
>combo...darn

Go ahead an build it. The key to any Ringmaster is making it light enough, making the controls very slow, and getting adequate but not overkill power. I have no idea about the AP Hornet, I've never seen one, but it seems like a potentially good choice.

By slow controls, I mean +- maybe 20-25 degrees of elevator motion for a full range of hand motion. Any more and the wing or elevator will stall, with dramatic and bad results. There's no point in having more than you need for "emergencies", because stalling makes it less likely to recover. The stock control system on the Ringmaster Jr (and full-size, for that matter) is about a factor of 3 too fast. The best solution is to use at least a 3" span bellcrank, drill a hole closer to the pivot for the pushrod, and have a taller and multiply-holed elevator horn to be able to dial in just the right amount.

If you want a perfect combination, I have found the Sig Skyray 35 with an OS 20FP/APC 9-4 to be nearly ideal as a primary trainer. I loaned mine out to someone last weekend, and he finished 5th in Advanced at the Golden State Championships with only one practice flight. Bear in mind, this wasn't "Eat Chili and Fly" day, this was The Big One in the most populous state in the nation! It may have been his best placing in a big contest.

The SIG Twister, with the mods recommended by Ted, and an OS 25FP/Tornado 10-4 is an excellent secondary trainer that I think, if built and trimmed correctly, I could qualify at the NATS with. But I'm not going to try to prove it!

Funny you mention Merco in relation to the Double Star motors. Since the US distributer of DS motors used to distribute Mercos, maybe you are onto something. As far as Bretts observations regarding the DS motors, they seem to do ok here in the southeast. I don't personally own a DS 40 but those I have observed seem to run pretty good, with a bit more power than a typical Fox 35. What the DS has going for it seems to be a consistent level of power from engine to engine. A comparison of Fox 35s (of which I have many) would indicate that some Foxes are more equal than others, I suppose due to both the vagaries of production and breakin. If you have a strong Fox you are in great shape, but get a dud one and you have a powerless shaker. (To Fox enthusiasts this is not a diatribe against Fox, I love the Fox 35 and am currently building a Gieske Nobler to give another one a home)
I have observed that DS users are often fiddling with venturis and head shims more than one might expect, but that may just be the people I see at the contests.
I have to say that the DS 60 and DS 50 look like pretty damn good motors for those who miss the big ST motors, but I'm still too poor to try one out.....

Steve

Likewise. However if one goes for a Fox with all the whiz-bang like stuffer backplate, hemi-head and ABC piston/liner then that will likely run the price up to or past the DS. The much lighter piston undoubtedly helps tame the shakes and the bit of increased power probably makes up for having to use a muffler. I must've got some good motors back in the sixties when I was building Fox/Noblers because they had all the power I needed and then some or so I thought at the time.

There's nothing really wrong with the run characteristics of the DS 40, it just doesn't seem to have the ponies to fly typical Fox 35 airplanes. I mean, if it has to be in a solid 2-stroke out with a 10-6 on a Gieseke Nobler to get 5.4 seconds laps, that's not much power.

The Stalker 35 and 40 were even less powerful. The two 35's and the one 40 RE that a local guy had in his Nakke had to be peaked out lean with a 10-6 to even get through a pattern. Nothing, including 30% nitro, really helped much. The 40RE in particular, was just dismal.

Once again, I emphasize that these were just the 6-7 examples I have seen. It's at least possible that these were just all the runts of the litter.

> I have to say
>that the DS 60 and
>DS 50 look like pretty
>damn good motors for those
>who miss the big ST
>motors, but I'm still too
>poor to try one out.....

The larger motors seem to be perfectly reasonable. The two Double-Star 60's I've seen were pretty decent. The Stalker 46 is about the same as a ST46, but with a longer-lasting piston fit. The Stalker 60RE also runs pretty good, my buddy John Sunderland had one and it ran fine and had plenty of power.

The quoted HP is hard to believe; something like .38 HP at 22K!

I've been talking to Currell about these things because I have a similar problem--except my model is finished--a gift from some really nice people to my son.

I'm not questioning his opinions on other stuff, but when Currell speaks on the Norvels, I trust him.

> Couple more things...
> 1) Where does vintage motor era end and modern begin?

There was a major overlap from the point at which the Schneurle Ported technology began to be used and the point at which only the Fox 35 (among higher production items) was left behind as a baffle piston motor.

> 2) Is a Fox .35 produced today a straight replica of a Fox .35 from 30 years ago?

It's supposed to be better in a variety of ways, particularly quality control. But my personal experience with an "infamous" fault for that engine (an interesting burble in power delivery at high altitudes in outside turns) has been minimal and my use of the most recent production versions is equally limited. I've wondered if this fault might be worse now than it was when I had half a dozen Fox 35's that were all still on hand and running regularly.

> As for the Junior Ringmaster, it is slated to take an AP Hornet .09. I hope this works 'cos this is what I've bought! If not I guess I'll just have to keep buying and building until I find a suitable combo.

I've used Cox TD .09's and Medallion .09's that were an excellent match to the little Ring Jr. (weightwise, at least - the TD might've made it a little speed demon at the time we had that, but I can't recall clearly). I have one right now with a Fox 15X on it that is slightly overpowered, but a nice match anyway. Whatever engine is used, about 4 ounces of engine weight is about all that works very well. Heavier engines than that aren't a good idea.

When matching the model kits to the engines, since most of the kits were designed when baffle piston engine technology dominated, subtract 30% of the displacement to compare engines. A modern type .10 would equate to a .15, if the weights of the engines are also on a par (more important for small size model planes).

Thus, a modern .15 should produce a bit more power than the average old .19 did, and a .20 should be roughly where the old .29's were. Depending on the .25 (and there seems to be a greater variation in power there than at the .20 level), the power should be greater overall than the typical older 35's, with a few of the 25's (my FSR models with BB cranks being among them) being as strong as "hot" 36's from the Way Back days.

Some of the kit makers were rather "loose" with their engine size suggestions (such as PDQ), and quite recently we've seen some idiot style labelling appear on the old Ringmaster Jr's "1A" kit when it was sold by Estes as a "Stuntin Ringmaster 19" for which there was never but a couple of .19's small enough in power and weight to be a match (Arden and OK Cub).

Further, not all of the modellers on the Internet Forums are straight Aerobatics types. My own orientation was always toward the faster, hotter end of C-L. Flaps on the wings don't seem to be some special magical device to allow me to build a model that weighs twice what it ought to. Therefore, any time I see anyone's list of model sizes as suggested ranges for this or that engine size, I tend to name my own matching set of slightly smaller wings, but UNFLAPPED, or with fixed flaps on the wings.

Modern 15 - 350-400 square inches, up to 35 oz, 8-4 or 9-4 prop

That's with coupled flaps. (With a matching good baffle 19, perhaps), and no flaps, build a smaller and lighter 300-350 square inch sport plane that weighs no more than 25 Oz.

Modern 20 - 400-550 square inches, up to 40 oz 9-4 or 10-4 prop

No flaps, 350-450 squares, 30 Oz.

Modern 25 - 450-575 square inches, up to 45 oz 9-4, 10-3, 10-4, 11-4

There's not often much in the way of appropriate models, other than Old Time Stunt, that will have wings larger than 450 square inches without having coupled flaps, but you certainly could use either the modern 25 or the classic baffled piston 35 on the planes in the 400-500 squares sizes while keeping the weights down to about 35 Oz.

Kiwi

I have mixed feelings about Norvels. Lots of power, sometimes very easy to start, sometimes need the spring, very thirsty, of course.

Confession: I have an oft-crashed one with an Enya 15-III that weighs 19 ounces!