mtntopgeo

My Feedback: (12)

What is the relationship actually, I forget. I just took the square of the rpm change based on drag increase, but is it a cubic relationship?

MJD
[/quote]


Yes cube is correct, so that was a pretty decent increase. Only ways I've gotten increases (in any of these small engines) were by swaping out factory muffler, & play with shims/nitro content. Whenever I got remotely close to doing what Andy does, the RPMs always go in the wrong direction. ...............George K.

MJD

My Feedback: (1)

Well then, like you say that is a very respectable increase, not to be sneezed at. Seems the turbo plug favors higher rpm performance, logical considering the normal application I guess.

combatpigg

My Feedback: (3)

700 = what % of 14,600? Not to quibble, but I come up with a little bit less than 5%. The more impressive way to look at it is thrust goes from 2.62 pounds up to 2.88, which is a 10% improvement.

ZoomZoom-RCU

[8D]What exactly are you shimming mtntopgeo? The head or the crankcase? Just curious as to what your rpm gain might have been. I've been following this cause I have an OS.25LA., and as you all likely know, the LA in this series stands for "LAME". Dont get me wrong, I love OS engines, just the La's are a little on the enemic side of the equation. Anyway, I'm currently flying a 5lb bipe with this particular .25 (Not bad for a little la .25 I must say!) but could use a touch more power if I can get it. I'm not using the stock muffler, so I guess thats good, but if I can squeeze a few more hundred rpms out of her by just some shimming, I might try it.

Thanks!!!

ZZ.

mtntopgeo

My Feedback: (12)

Never have played with the OS LA engines, Just been trying to get a little more out of the .09 Enyas. Mostly shim the head, & play with nitro %. Not repeatable, at all, from engine to engine. Next is to try to shim the cylinder to get a few degrees more opening on the ports. A real pain cutting out the shim. Probably won't get me anything, but keeps me busy! ................. George K.

MJD

My Feedback: (1)

Not rpm increase, but power increase. The rpm increase is indeed a factor of 1.0479 aka 4.8%, but the horsepower increase required to do that is 1.0479^3 = 15%. I thought at first it was rpm increase squared, thinking of the drag equation, but apparently the relationship is rpm increase cubed. The thrust increase figure seems intuitive, lift is proportional to v^2 therefore the thrust increase should be about 1.0479^2, or 9.8%.

MJD

AndyW

My Feedback: (1)

Today was a very productive day. Steve's performance figures had me dig up an APC 7 X 3 and give it a try. The results were mixed and that forced me to have another look at the stock head and the turbo head.

After much contemplation, I decided that the stock head was undercompressed compared to the turbo. So I really went to work to trim it down and modify the combustion chamber to try and duplicate what I had with the turbo. Just to complicate things, I also rounded off the edge between the chamber and the squishband on the turbo head. It seemed a little overcompressed and this took some of the edge off that. Plus, it seemed to me that this would smooth out the burn.

Whatever I did, it seemed to work in both cases.

On the 7 X 4 Tornado prop and 10% Cool Power, we now got 15.25K (compared to 14.6) on the stock head and 16.25K (compared to 15.3K) with the turbo head. It looks like there IS value in using a turbo plug over a standard glow plug. A decent 1000 RPM advantage, same fuel, same prop.

We are now considering the turbo portion of our experiment a success.

At the same time, Steve's report on his stock engine on 10% and an APC 7 X 3 had me wondering. What is this engine going to deliver once we're through with all our mods. Well, we already did up an OS .10 a few years ago. This has the innards of a Hornet .15 installed.

So we gave it a run on the APC prop and 10% Cool Power. Here, http://www.youtube.com/watch?v=xjH2hTO41J0 we have this bored, OS .10, doing 19.7K on the APC 7 X 3 and 10% Cool Power.

Here, http://www.youtube.com/watch?v=Xseov35rRQM we went with 25% Omega fuel and the result, after adding a shim, was a solid, 21K. Ouch. It got scary so I got behind the engine.

I don't want to do much of that any more. I want to save this one for a special, diesel project.

Our cylinder is larger on the bore but it was thinned down in crossection to fit a bored out case. The piston is also larger but it IS aluminum. I didn't weigh the original engine but I'm confident that we haven't gained much weight.

I'm pretty happy with just a bored out OS .10 as this one is.

The subject of our thread though, is to bore AND stroke the .10 by stuffing the piston and liner from a .15 along with the crank from another .15. That crank is only marginally larger so we won't be gaining that much weight there either.

burtcs

Andy:

Atta boy. I like the 7-3 APC on this engine. The APC 8-4 works pretty well on a .15fp by the way.

regards - Steve B.

AndyW

My Feedback: (1)

Yeah Steve,

I was impressed. Thanks for the stimulating input. Never thought I'd see a ten honk like an 0-six. Nineteen K on an .06 is fun. On a 7" APC slicer, well,,,, [X(]

Been going slow for so long, I forgot how neat fast was.

That reminds me. I've got to run that LM .06 on 40% fuel and a 4.5 X 2 prop. Can I get 30K? [>:] Are there earplugs effective enough?

CP,

What prop/fuel do you run to get 30K on a stock engine? I got several of these for 25 bucks so I don't care much if I blow one up while learing something.

burtcs

Andy:

As an aside, having nothing to due with this venture, even a Gillbert .11 with turn 16,000 with a 7-3. It's kind of an over the counter magic prop for .10's and .11's. with no cutting required.

regards - Steve B.

AndyW

My Feedback: (1)

Steve,

Gilbert .11? RC? Tell us more. Can you post a picture?

burtcs

Andy:

The Gillbert s aren't R/C, they're CL/FF engines. I've got a couple. They would be easy enough to modify for
a throttled carb and mufflers could be fabbed in a pinch but it's strictly a sport engine.

regards - Steve B.

combatpigg

My Feedback: (3)

Andy, I don't think a 4.5x2 has any application with .061 engines, If you want some thrust in return for a lack of speed, the 6x2 is the way to go. The way that I've seen 28-30,000 rpm with a stock AME is with a 4.2x4 APC on 40% nitro, open exhaust. You'll need a real small and clean plane to make good use of this prop, though.

Dan Vincent

Andy,

I posted some Gilbert .11 pix a while back.

http://www.rcuniverse.com/forum/m_19...tm.htm#1911088

Fox. .09 & .10, Hustler .10 and Cox .15 heads have the same size glo-head thread so there may be some power available with another head.

AndyW

My Feedback: (1)

Dan,

Thanks for the link. That is a great looking little engine. Innovative features, sideport, twin ehaust stacks, hmmm, single bolt mounting on each lug. I just might get me one. Reminds me of the Fox .049 I got some years ago. I put my standard, 6 X 3 Tornado on 25% fuel and it spun up to 19K. Far better than any Cox I owned. And it was a long stroke.

CP,

Yes, I tried that glass prop the other night on my Low Stick. Didn't pull as well but it sure did sound mean in the air. [X(]

Steve,

A sideport with a throttle. That would be interesting. No shortage of throttles around here to stick on to it. Neat. [8D]

Japanman

Hey Andy,
Whats that crank next to the TD crank?

S

AndyW

My Feedback: (1)

Stefan,

That's out of a CS .049, early vintage. Yes, it's massive. The picture was taken in reference to a thread discussion about the merits of short versus long stroke. The Fox engine has a narrow piston compared to a TD so to maintain the cubes, the stroke is longer. Ditto the CS. You may know of the Holland Hornet, a real screamer but decidedly short stroke.

This project to bore the .10 with a .15 cylinder makes it a shorter stroke than the original. And as the original intent of this thread but in retrospect, I had already done that with the .10 and that project was deemed a success.

So this time, I'm going to stuff in the Duramx innards for the OS .12. This will allow me to show how it's done and will hopefully display the advantages of true ABC compared to AAN. The piston is only marginally larger so the advantage won't be so much in cubes but in metallurgy. The Duramax product has decent pinch at TDC as opposed to the FP and this usually helps a lot. After that, the idea is to stuff the crank from the old OS .15 and in this way we create a long stroke of sorts. We've already seen what over bore does, now we are looking at what just stroking can do for us.

Finally, we can always stuff another .15 crank into the (.15) overbored .10 and see what a bored AND stroked OS .10 looks like.

BTW, I got your .15 P/L set on Friday. PM me with your address and I'll fire it off to you on Monday.

StanDouglas

I just stumbled on this thread and it's been a while since anyone posted here, but haven't you tried boring out the carb? I don't know how the OS .10 compares to the OS FP .20 but years ago there was a writeup on the .20 by Mark McCool:
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After disassembling the carb and noting the needle valve position in the venturi,
The next step requires a ¼" carbide drill bit for the .20 FP carburetor and a 3/16" carbide drill bit for the .15 FP carb respectively.
Clamp the carburetor body into the drill press (or mill) fixture upright and 90 degrees to the table. With plenty of cutting oil and the sharp drill bit at LOW speed, drill the venturi completely through from the top to the bottom of the carb body (GO SLOW and use plenty of oil). Clean and debur all edges across which the bit has passed with a half-round needle file and/or emery cloth. Run the carburetor retaining screws that were removed in disassembly in and out of their holes in the bottom of the carb body to rethread the inside of the larger opening. Remove all metal flakes and thoroughly clean the carburetor body with brake cleaner then lube it with WD-40. Test fit the carburetor into the front case, adjust the carb accordingly (if necessary), clean it, and remove it.

The carburetor barrel is made from a strange grade of tempered steel and requires special treatment because the metals tend to mushroom and flake (this process is not for the faint-hearted which is why I suggest a machine shop).

For those well-equipped brave souls…With torch and vise-grips, heat the carburetor barrel red-hot to take the temper out of the material. After it is slowly cooled, clamp the carburetor barrel into the drill press (or mill) fixture with the throat upright and 90 degrees to the table.

IMPORTANT—The next step requires a ¼" carbide ream for the .20 FP carburetor and the 3/16" carbide ream for the .15 FP carb respectively!

With plenty of cutting oil and the sharp carbide REAM at HIGH speed, ream the throat HALF WAY through from the top. Turn the carb barrel over in the fixture and repeat the process from the bottom, this time reaming all the way through. (REMEMBER--GO SLOW and use plenty of oil). Clean and debur all edges across which the ream has passed with a half-round needle file and/or emery cloth. Reinstall the plastic throttle arm and retaining screwinto the end of the carburetor barrel.
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Next there was a tuning method to move the needle assembly as far out of the venturi as possible to allow for more flow through it.

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With the exception of the needle assembly, reassemble the carburetor and recheck, adjust, and clean it for a snug fit and smooth operation. Return the low-speed idle screw to its original setting. Assuming you are ready to run the engine, reinstall the needle valve so that the outlet is only half as deep into the venturi. The purpose of this exercise is to maximize the airflow through the venturi by removing all obstructions. Reinstall the carburetor onto the front case. The carburetor is finished! Now its time to tweak your .20 FP!
If you tach the engine now, you’ll be very pleased with the results. Test the idle reliability and if not satisfactory, adjust the low-speed screw accordingly.

Once idle reliability is achieved and high speed is satisfactory, turn the engine off, loosen the needle assembly and back it out, splitting the difference between where the needle outlet was in the venturi and the edge of the venturi. Tighten the needle assembly, run the engine, and repeat the tweaking of adjusting the high-speed needle, testing and adjusting the low-speed for reliable idle. The farther out you back the needle outlet, there seems to be a tradeoff with reliable idle, so the purpose of this exercise is to find the optimum point so you achieve maximum RPM at high speed without sacrificing satisfactory idle.
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Don't know if any of this applies to what your doing or not.

Regards,
Stan Douglas

AndyW

My Feedback: (1)

Hi Stan,

Yes, good thought, thanks for the input. If we have more cubes we really should be feeding them more fuel and air. This WAS on the agenda but circumstances took me out of town for most of the summer. I'm back at it and will be finishing up doing THREE OS .10s in various combinations. A nice bonus is that the ABN liner of one of the .10s is going into a Norvel .074. Waste not, want not.

1QwkSport2.5r

Reviving an old thread - I have interest in boring and stroking a 10FP. I have one I got NIB and I also was able to obtain the Duratrax 1522 piston and cylinder kit. Curious if there was a crankshaft found to pull a little longer stroke than the .10 crank can do in addition to the .15 cylinder and piston.

Mr Cox

I haven't looked for any replacement cranks for the OS .10 engines, so don't really know. I do have a peeling liner on a .10 FP though...

Will the Duratrax fit the .10 engine, or do you drill out the crankcase and/or turn down the cylinder outer-diameter?

Turning down the outerdiameter is a little tricky to do. I once used an ASP .12 cylinder and piston set to replace the stock one in a Webra .12, but I wasn't quite happy with the result. As the thickness of the brass in the liner is turned down, it seemed too loose a little of the pinch at TDC. The true chrome in the ports are a bit tricky do deal with too. I think the best way is to manually remove the chrome in the channels first (with a dremel and diamond stone, working only on the outermost part) before the lathe work can begin. Thereby the lathe will only work with brass material. From memory I had to make a holder to grip the liner well and the top lip needed to be reworked (reduced thickness) to in order to get the correct timing and deck height. It might be better to rework the crankcase instead.

1QwkSport2.5r

I haven't measured the case and liner yet as the engine is still in an airframe and I've been crazy busy (just had twin babies at the end of June). According to this thread, the liner needs to be turned down and possibly the case opened up to fit the liner.

As for the chrome fade in the ports - removing the chrome fade will alter the port timing. Just removing the chrome will increase the timing by 1-3 degrees - at least it did on the Novarossi and Picco engines I modified recently. The Duratrax liner has chrome fade on only about half of the inner edges of the ports, so turning it down won't be a problem I don't think.

Im gonna try getting the FP out of the plane and get some measurements off of it to see how it's all gonna work. If I can get the Duratrax liner fitted, I'm going to pull the OS piston and liner and sell them. They only have about 20 minutes runtime on the set.

aspeed

Mr. Cox needs a piston/cyl. I don't think I would bother changing liners and cranks, you may as well just get a .15 IMHO. I am all for doing mods, but because of my upbringing with speed planes, I go with an engine size and work with that. Not like cars with .060" rebores-no replacement for displacement attitudes. If you have a peeling liner and want to replace it with a possibly better ABC one, well that is fine, or just want to play around that is ok too, and I support that effort.. To stroke it may require a wider case, so you are pretty much stuck with a fairly stock size crank. An AP cylinder has a 15.5mm bore, while most .15s are 15mm. That was done because they wanted a .15 out of an .09 case. They did not change the crank in that instance. The exhaust and carb are the weak part in the rebored motor with that change. It is a fairly easy fix though.

1QwkSport2.5r

Firstly - I am like the antichrist of OS nickel liners. I don't really like OS engines in general. I don't like Fox either, but got a Fox engine running more reliably with an MDS piston/cylinder than the OEM parts could do. The OS will peel eventually. Why not out a cylinder into it with an actual pinch and that won't peel. Maybe even make more power? Besides - OS fans will pay money for good parts since the distributor discontinues stocking parts for engines the moment they are discontinued (it seems). As for the stroker crank, that would be only if I could find one that fit the .10 case. Otherwise I'll stick with the stocker and just modify the bore and timing of it. I'm putting the ABC cylinder into the OS because I can. I'll guarantee it'll run better, last longer, and probably make more power since it's a liner designed for a car engine which are almost always timed higher than airplane engines.

Ultimately its a because I can thing, but also because I got the Duratrax p/l for a steal.

aspeed

I am sure the results will be good. A stroked crank, will likely not work easily. If the stroke is, say 1mm longer, then .5mm will need to be removed from the case at least where the rod is located and maybe where the backplate is too. That would mean a new backplate needs to be made, or the crank OD turned down...... I am always wary of the OS nickel too. I down't like to mill the exh. port higher for fear that it will peel easier than even normal. I have never had one peel on me but have bought one SX .32 for parts that was starting. I would estimate that I have maybe 30 nickel ones? All I have bought used or new at swap meets for a deal. I have got good service from the ones I have flown. About half of them. The rest are kept NIB or for spares, as parts are a bit pricey here. You guys in the US complain about a $70 liner, but here we add 38% dollar exchange, and shipping in US$ and the price can get close to double the US list.