Two Gilberts with mufflers

I was amazed in some of the old Aeromodeler articles, that they would run in the engines for 1.5 to 2.5 hours prior to testing them, to ensure they were well broken in. It was possible for a tight engine to require more time, a half hour sometimes was insufficient.

Sometimes contrary to logic, a lighter inertia prop made of wood will work wonders with these older engines during hand flipping and running.

Eric,

8-10K is about normal for those things. it may need more breaking in as suggested or more nitro to help with the needling.

In the end, don't expect much. You will have to build something that is light yet will handle the weight of the engine. A twin might be a good compromise.

They are pretty little things, just not much in the power department.

Ron, those numbers you state might be on no nitro or FAI fuel. I think these Gilbert engines are better adept at turning greater RPM's than the 8 to 10k. At least when I was bench running mine, it certainly seemed stronger than those figures on 15% nitro fuel.

Sceptre Flight: Fox Rocket 09 Side Port Review

is the same side port technology, 13,000 RPM was achieved on a 7x3 prop and 20% nitro fuel. The Fox engine has a displacement of 0.0974 c.i., just shy of .10 c.i. It achieved a brake horsepower of 0.11 at 14,000 RPM.

EarlWB obtained 15,120 RPM on his Gilbert .11 with a 7x4 prop (black, may be a Masters?) on 1/2-A Glowboy fuel. I don't know the nitro content, but imagine it is at least 25%, may be 30%, higher than the Fox under test. Being the Gilbert is slightly larger in displacement would help it to be slightly stronger.

(See Post#4 in RC Universe: Club A.C. Gilbert )

Others who have tach'ed their Gilbert .11's more or less have supported 12,500 to 15,000 range, or so I have gathered. They do seem to peak out better after they get well broken in.

As props vary according to thrust even though they may state the same diameter and pitch, a 7x4 could be another's 7x3 (i.e., possibly Masters 7x4 [Texaco] = APC 7x3).

My Enya .09-III TV was rated by the manufacturer as 0.16 brake horsepower and confirmed by Peter Chinn at a touch above 14,000 RPM. It turns a 7x6 prop with ease. I use that as a comparison to the power of the Gilbert on a 7x3.

The Gilbert .11 is definitely more powerful than a Cox Black Widow (0.08 HP on a 6x3), but less than the Enya and OS 09's and 10's of the day. (0.08 Cox BW < 0.11 Gilbert < 0.16 Enya.) Conclusion, they fit in between, somewhere perhaps a touch over half way mark toward the Enya .09-III TV, or as others would say, like a very mild .09 engine.
Anyway, that's my 2-cents for all its worth.

I don't know what I will do with the engine yet other than mount it back up and run it in some more . I tried the 15% fuel I have had for awhile it would not stay running / switch to the sig 25% got it running without as much flipping !! 1.5-2.0 is a lot of breakin sounds like a enya I have no idea how much run time is on it , it does seem to not have much compression are your the same way or just get better as you go with break in ? Eric

Back in the fifties there was a debate on whether an iron/steel engine needed break-in. The CL guys said yes, and the FF guys said no. Well it turned out both were correct. For CL guys, the engine needed break-in or it would overheat and wear out fast. If run extremely lean when new, it could cause thermal runaway and sometimes severely shorten the engine's usable life. The best way I have found to break-in an iron/steel setup is to give a rich first run to flush out any junk left in the engine after you cleaned it. Next give it some heat cycles. That is run it on the rich side of peak for about a minute then shut it down by pinching (or disconnecting) the fuel line. Let it cool to air temp. Heating plus cooling is one heat cycle. A series of perhaps a dozen heat cycles relieves internal stresses without so much wear. Steady running is not the same as heat cycles. When it will hold a steady needle without slowing down (sagging) it is ready.

For FF guys, one flight = one heat cycle so they were breaking engines in just by the way they run them. That's why their engines improved as you run them.

Although it is not always necessary, a proper break-in will allow your engine to be all that it can be.

Most iron/steel setups used a straight bore in the cylinder and straight sides on the pistons. These took the longest to break-in. VECO came up with a tapered piston and advertised it as TCC (Temperature Controlled Clearance). Others soon followed with either a tapered piston or tapered cylinder.

As metallurgy progressed, methods needed for break-in changed also.

Apologies, I did not intend this to be so long.

George

George that sounds good and makes since , a lot better than just running tank after tank of fuel through the engine . That 09 enya I have would get hot on a rich run and would not start back until it was dead cold . I will give this a whirl , Thanks for the heat cycle lesion . Eric

getback wrote:George that sounds good and makes since , a lot better than just running tank after tank of fuel through the engine . That 09 enya I have would get hot on a rich run and would not start back until it was dead cold . I will give this a whirl , Thanks for the heat cycle lesion . Eric

When you run the Enya check if the crankcase is hot on the bottom, beneath the venturi . If it is, perhaps there is castor varnish or maybe the crank needs to be polished.
OTOH older Enyas were sometimes tight and needed some heat cycles before they would run right. These are the ones that seemingly last forever once broken-in.
I have some Enya ,09's...two Mk III, one MK IV, and a MK III parts engine. All ('cept the parts engine) run well.
Good luck with your heat cycles.

George

I've got 4 Engine .09-III engines, two RC (TV) and two CL. They all have extremely good compression, all but one were previously run. Enyas, they just seem to not want to quit. Even the .15-III TV parts engine with worn piston/sleeve will run if I squirt a few drops of fuel into the combustion chamber to provide a seal. Seems to provide same power as the good ones after started.

Regarding heat cycling, George, I use a 1 oz. tank on my bench setup. I used this approach on the unrun Enya and for the larger engines. I didn't short cycle it as your method, which BTW makes very good sense, although naturally with the larger engines 1 oz. provides a decent short cycle, which unknowingly I was doing. Ran the .09 rich first couple tankfuls, when it loosened up then could wet 2 run it until it would hold it leaned out.

Seems after about a half dozen more or less tankfuls on the larger engines, they start to loosen up. In my limited experience, after continuing these smaller tankfuls, once they can hold a wet 2 cycle, I feel they are ready to be mounted. Nice thing about CL is one can run them 4 cycle or wet 2. If it starts to slow down, then its not ready. But I've run them on the bench enough that I haven't seen that happen yet.

Personally, I see no reason to bench run them on larger tanks, such as say the 10 or 12 oz. But that's me.

BTW, the Enya .09-III TV is a very economical engine. I haven't timed my flights, but in a foamy RTF cabin, they have a decent flight time just on a 1 oz. fuel tank. I'll have to get my Gilbert .11 into a suitable airframe. Still leaning toward a DeBolt 26" All American.

Just wanted to add, the Gilbert because of its unusual side port configuration with rear venturi and longer crankshaft shares similar problems with the Cox .074 Queen Bee. Finding a plane to put this engine on adds challenges.

Engine mounts that are long like for the QB are hard to come by, because they have been discontinued. About the only ones that might work on the .11 Thunderhead is Sig's 2 piece small "T" motor mount and the same by Great Planes. The Chinese have similar, too. These are for .10 - .25 engines. Haven't checked width, but engine mount for the QB might work, too.

I thought a good CL plane would be the 1951 profile Testors Sophomore-9 with 24 inch (610 mm) wingspan. Plan shows an older McCoy .098, which powerwise would be close to that of the Gilbert. Alas, would have to relocate fuel tank to behind the wing leading edge. Since engine is heavy, making it stick out further forward is not an option.

No matter the plane, some definite reworking of the original design is in order to make it work for this engine.

rsv1cox wrote:I received the pair of Gilbert .074's yesterday.  Nice people included an unexpected unopened blister pack needle valve assembly.  



These show no indication of the problem that I encountered in the single scratch built from parts engine where the piston hits the head with authority.  That seller is sending me more gaskets along with other parts and another engine.

The two Gilberts have recoil spring starters that work great.  A small movement of the prop results in an energetic spin.  One has a 7/4 Master airscrew prop that will have to be replaced for something more appropriate.

I have a profile Brit Mosquito and a L-10 coming.  Will have to make a choice as to which one to use them on.  

The starters will make the Gilberts rather heavy, although they are handy as they work well and prevent the backwards starting which plagues these engines.
They run well on their original 6" prop. I would use a 6X3 to allow them to wind up to where they're happy. The 7X4 would really make them labour. When these were used in the "Wing Thing" they ran a narrow 5 1/2" fine pitch pusher. Many condemn them as not being very lively, but allow them to wind up & they really sing. Having said that, I still think they will be too heavy for the Mozzie with the starters.
Rod.

rsv1cox wrote:The engine mount problems that GG and Rod alluded to have got me thinking.  Perhaps another scratch built twin will make an appearance.  Something that would allow me to blend the engines needle valve assembly back into the fuselage.  I don’t think I would use the heavier muffler/spring starter Gilberts but use instead these two without those features.

Bob, I've noticed the latest engines I bought from Steve have only a standard narrower diameter prop hub, not the heavier starter hub with coiled spiral steel spring. Two engines I bought from Tower Hobbies 13 years ago had the starter hubs but were absent the coiled spring and articulated steel catch tabs to make the starter work. I don't think the spring itself adds much weight, less than 1/4 oz. I guess Steve ran out of spring parts some time back. Two E-Bay buys, .074's had fully working starter springs. One was slightly damaged so I removed the coiled spring. Those I gathered were probably donor engines from wrecked RTF's.

Some serious running in and evaluation would be in order before doing so.  The simple route would be to just mount a couple of Golden Bees but I have been there, done that. Bob

I'm thinking along the same route you are, Bob. A scratch build is definitely in order. Personally I just want the satisfaction of successfully running these engines, having successful flights that make the best use of these engines. It is easy to take a more powerful engine and bore holes in the sky. A greater challenge is to select and build an airframe with the appropriate modifications to accept the engine, which flies exceptionally well with its lower power.
This is what vintage flying, whether RC, FF or CL is all about.

That's Cool That was all it needed to get her straightened out , except for running hope that works out OK , still got some questions on mine ,, Say that old RC would have enough room for the Gilbert ? I wish I woukld have stuck with RC till I got better other than out . But that's life Eric

Here's something that might work better with a pair of Gilbert .074's.

http://www.outerzone.co.uk/plan_details.asp?ID=2905