Limited B engines

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AIM
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Limited B engines

Post by AIM »

Does anybody have any input on motors up to .29 that works for LimB. I'm looking for a list of basically box stock motors that will turn the 14500 with a 10/4 on standard 10% or 15% fuel without any mods to speak of. I see alot of oddball motors on ebay that sell pretty cheap but I don't know if they will work or not. I know from personal exerience that the Mag 28 and the FX 25 do just fine. I also know the Mag 25 does not work well.
I have a new Norvel that I am pretty certain will be OK but I have yet to run it.
PS. I'd like to include E motor setups on this list as well so if anyone wants to chime in that would be great.
sgilkey
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Post by sgilkey »

Supertigre .29, Como .29, OS 28F and 28F-H. The OS 28F (especially the heli version) is still widely available in the second hand market, and is a smooth running and very user-friendly engine. With the heli head it is only slightly heavier than an FX, with a standard head it's actually lighter. It has the same mounting and muffler bolt patterns as the FX. Like an FX, it seems to find turning low 14k on the spec prop very routine. Some are higher. As long as you are in the low 14k range you're in the hunt and will be just fine. If you drop below 14 you will start to notice a performance deficit to most of the pack, I think. The ST is a real torquer and may get you over the limit. I used to use STs when the "old" limit of 15.5k was there and they would turn in the 15s easily. Now with the 14.5k limit I don't usually run the STs because I dislike having to shut the carb down, it's easier to just run the FX or 28F. The ST is about the same weight as the 28F and has the same mounting pattern, but has a different muffler spacing (which happens to be the same as the 25FP). All these engines are very durable and have excellent carbs, about the only maintenace item is the rear bearing which is the same size on all of them, and readily available. With the LimB setup it seems that they never wear out or break, unless you eat some dirt (not that that ever happens in combat!).

As you have observed, the Norvel and FX are good picks. I like the RNV/swept NV on those engines for combat- conventional, straight, carb-mounted NVs have been known to get broken off in midairs and dirt naps. The FX NVA will break off but it's not usually going to stop the engine, unlike a normal carb.

The Mag 28XL also seems to be a great choice, but be aware that I have seen at least three different carb choke sizes (anywhere from .239 to .270) on the Mag 28. The bigger carb definitely gives more power in a conventional Open B setup, i'm not sure if the smaller carb is a problem for LimB. It might be fine- what size is your carb, and what rpm have you been getting (and with what % nitro?). The Mag 25XL is a bit of a wheezer although it comes with a small carb and performs noticeably stronger with a larger .28 carb (mine turned 14.3 on the spec prop with a bigger carb). The Enya .25X and SS engines are really nice running but only turn about 14k max, which is still pretty adequate but not up there with the FX. They also have weak carb-mounting areas so I would avoid them for combat. I have three, and two have cracked carb mount bosses. They're repaired with JBW and still run great but it's a hassle to break the carb off in a dirt nap! The K&B 28 sportster is kind of weak, only turns upper 13k range. It would get someone in the air if that's what they had laying around, but I'd avoid it if there were other choices.

The Fox .25BB Schneurle engine has a reputation for being a strong running engine. I have one but have only run it on B props, where it was not up to an FX (and being an iron-piston engine, it is a vibrator at high rpm). I haven't yet tried mine on a LimB prop but based on its performance on a 9x4, at this point i'd say there are better choices. It ran fine for me, though.

The OS 25 FSR is very weak and I would not recommend it. The 25SF is a nice runner but not as strong as an FX. The Thunder Tiger PRO 25 is a wheezer, weaker than a plain-bearing 25. Any plain-bearing .25 (i.e. OS25FP/LA clone, NOT counting the Norvel) is not up to competitive Limited B demands in box-stock form. I have also run Royal and Leo .28s (basically the same engine), and the Brat .28 and all are rather weak. I mention these because they show up on places like eBay all the time, usually described as "screamers" but as Keith Jones would say, they can't pull the skin off a bowl of rice pudding. And finally, the Webra .25, for all its might in Open B, is a weakling on a stock muffler and limited B prop!

Hope that helps!
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Ed Kettler
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Post by Ed Kettler »

Stock OS .25FX seems to work well in 2548 and Limited B. Cash and Chris Handegard use Norvels, so they can comment on them.

The best I got from a 25LA was 13.8, which is not competitive.
RH
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Post by RH »

Personnaly I would not buy a used engine for competition. There is a huge difference in the way an engine performs depending on how it is broken in. The published break in proceedures will give you a suitable sport engine. The small prop, high rpm, heat & cool cycle technique is what you need to do right out of the box to get the most out of whatever engine you decide to run in competition.

I have run Norvels but can you get parts any more?

I currently run the OS FX and would run nothing else.

r
CStein
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Post by CStein »

Aaron just get a fora .29 for every plane!! Then u will never need to worry about not
making rpm limit and u will have something to fly in open
Fred420
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Post by Fred420 »

How about an MVVS? I have to fly what I have and I am going to try it on one of my B's
AIM
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Post by AIM »

I'm curious as well about the GMS motors. I've seen a couple of these sell pretty cheap on the internet. They are only $55 new so even that isn't to bad.
I know Corey had a couple of these for open and seemed to like them but I think they don't perform anything like what he is running now but hey, we are only worried about 14500 right.
I also see on towers sight that the Thunder tiger is only $55 also.
sgilkey
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Post by sgilkey »

Aaron, I'd suggest walking past the GMS. They are VERY inconsistent. The Canadians who used to fly with us bought a lot of them (because OS engines were so expensive in Canada) and maybe one out of five ran decent. They seem to have really bad carbs. As to the Thunder Tiger, the GP (plain bearing) won't have the stones to break out of the 13s and the PRO (ball bearing) is even weaker, believe it or not!

For reliability and power, I think you're going to have a hard time beating either the FX or the Mag 28XL if you're going to buy new.

The Norvel will make the power in "stock" form but Norvels are among the most finicky engines you'll find. Their big advantage for B was they made tremendous power on a pipe, at low weight. BOth advantages are nullified in LimB (the light weight is no help as even you can build a plane to the min weight of LimB!) and the foibles of the Norvel just aren't worth the fuss if you can't take advantage of their few "plus" factors.
AIM
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Post by AIM »

Thanks for all the info. I hope that others interested in LimB will benefit from this as well.

I just aquired another Mag 28 so this brings my fleet up to 2-28s 1-Fx and 1-norvel. That should be adequate for this season.
mark s
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Post by mark s »

Aaron,

With the way you fly, maybe an LA .15 would work best for you. We all know that your round times would increase for 15 seconds to 45 seconds. You might just have a round when you get past the engagement line.

Better yet, I’ll let you have one of Peyton’s gliders. They almost always fly longer then Aaron.

Roid
AIM
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Post by AIM »

OHHH boy!!! How do I respond to that other than to say that you better keep your eyes on your planes.... Spinner nuts have a nasty way of coming loose at the worst times.. Of course I'll bet with Peytons gliders I could pretty much whip your butt! I've just been sandbaggin the last couple of years.
Fred420
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Post by Fred420 »

Hey Scott .......... I have been looking for the Mag 28XL and the OS 28f engines that you are talking about being on e-bay. I either do not know how to search there, this is my first time on e-bay, or there are none.

Do you know where I can purchase either of these new or in good used condition? I am using an MVVS 25 and it just does not want to stay tuned, it is about 15 years old.

Thanks
Rabbit Leader
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Post by Rabbit Leader »

My experience with Norvels is that they want a real break in, at least 3-5 tanks on the bench, with the alternating rich/lean needle to get it hot and then cool to let everything settle in..I also tighten the backplate and head button after each run. I've never had to reseal either my ball bearing or plain bearing engines.

Both of these engines will make 14500 esy enough, the BB engine will break out in good weather. The midrange is just okay, they tend to load up if your'e not careful, but I don't think we worry much about that in combat anyway.

Once you get the engine tached, make SURE you launch it pretty "fat", about 1/4 to 1/2 turn from peak, and let it fly..Norvels like to be launched pretty rich,as they lean out considerably in the air.

I'll probably mothball my Norvels for the time being, as I have 1 good running BB motor and 1 good plain bearing, and a few spares...I'll see if anybody picks up the brand or not..

Cash
sgilkey
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Post by sgilkey »

Dave, I've been off the Bay for awhile now, I was buying too many old engines that i didn't really need (but really wanted!). There were always several 28F heli engines, i guess they were really popular castoffs from guys who upgraded to 32s in their helis. Now all the heli guys are upgrading to .37-.39s so the 32s are readily available second hand. The Mag 28XL is also pretty commonly available second hand and of course is also available new. Though at Tower's asking price of $70 I'd walk right by it and buy the 25FX, which is simply better in every regard. You used to be able to get the 28Xl for 55-60 bucks. Magnum has gotten pretty proud of their engines lately!

The 28F was available in three versions (aside from the heli and aero versions, that is. The heli and aero are identical except for the larger heat sink head which adds around an ounce to the weight of the engine): ABC, dykes ring, and iron piston. By far the most prevalent is the dykes ring. It will often feel like it has little compression when you flip it over, but will still run fine- that's a design attribute of the dyke's ring. If the ring is truly shot, replacements are available (not from OS). The ABC speaks for itself, similar in construction to today's FX. The iron piston engine runs great but at high rpm (ie Open B range) it does vibrate more. For limited B rpm it will probably not be an issue (and will almost certainly be smoother than a Mag28XL which is a bit of a vibrator too, despite being ABC). However the added vibration may cause fuel foaming if your tank installation is not good. You can tell an ABC by the brighter color of the piston- the iron piston is a dark/dull gray. I'd say any of the versions would make a good LimB powerplant, as long as they're in good shape! Being an old design, probably out of production for over a dozen years, any that you get are going to have been sitting around awhile, which could mean rusty/pitted bearings/cranks, stuck rings, etc. I've gotten some really clean sweethearts, and some gooped up ones that needed a good scrubbing and new bearings (which are readily available) and everywhere in between!
sgilkey
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Post by sgilkey »

Dave, forgot to address the MVVS 25. Several years ago the MVVS 21 and 26 (and even the occasional 28) were quite popular in combat. They made bodacious power but were heavy and inconsisent- some ran like gangbusters, some not. I've never run across a 25 but would assume that it is like the 21 and 26 in that the carb was troublesome. Don Veres used to run a lot of MVVSs and he invested in OS 32 carbs for them, which completely tamed them. The OS carb was a drop-in with a 13mm neck (same as the 25FX, 28F, 32F, 32SX, etc). So if you can find an OS carb, it might solve your problem. If you bring the engine to Hillside I'd be happy to have a look at it and see if I can see anything wrong with it. One thing to look for is the NVA- a tiny sliver of fuel tank plastic or fuel tubing can get lodged in the spraybar and wreak havoc as it alternately covers and uncovers the orifices. Even if you use a filter, you can get these tiny little pieces of debris. Also look for air leaks around the NVA and fuel nipple, and also the engine backplate.
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