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Post  poorbs on Sat Oct 13, 2012 11:55 pm

I've been running Conquest .15s for decades, and wonder which prop others have found to be the best performers. I tried the Rev Up 7 X 5N, which I think was used in quarter midget racing, but have found that a Top Flight 6 X 7 1/2 gives best acceleration and top end performance. It got even better when I replaced the carb with the venturi, using a bladder for fuel, and a tuned pipe. Is this engine still popular for flying, or has it become a collector's item? I don't get around to other clubs much, and am the only one I know of who still flies with these engines.
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Post  RknRusty on Sun Oct 14, 2012 12:00 am

Hey, Poorbs, welcome to CEF. It's pretty quiet in here on the weekends, but someone around here will get an answer for you. A few conquest owners hang out here.

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Post  Cox International on Sun Oct 14, 2012 2:02 pm

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Post  Surfer_kris on Sun Oct 14, 2012 2:13 pm

An 8x4 is fine for the RC version but something around 7x5 is better in a fast plane. No one around here are using these as intended (.15 pylon) anymore, they are mainly a curiosity and are treated thereafter i.e. with TLC rather than all out performance.

If you really want to have performant conquest then try to get hold of the ABC piston and liner.
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Post  SuperDave on Sun Oct 14, 2012 2:39 pm

IMO. prop selection depends not only upon the engine used but the airplane to be flown.

There are no hard and fast rules. That's why most of us experiment with different prop pitches and diameters.

Certainly do.
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Post  Kim on Sun Oct 14, 2012 8:15 pm

Hi Poorbs,

And welcome to the forum! It sounds like we may be able to benefit from YOUR experience with Conquests! I've got two that are slated to power a couple of Mattney's Models Rivets, but flying them as sport hot-rods rather than actual racers. I've test-run them, but will have to get them on their intended planes in order to have any idea of their performance.

I believe Ken has had some direct experience with these engines as free-flight power-plants, and figure that he ought to be checking in here in a bit.

Again, Welcome ! Kim


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Post  poorbs on Sun Oct 14, 2012 11:54 pm

Kim wrote:I've got two that are slated to power a couple of Mattney's Models Rivets, but flying them as sport hot-rods rather than actual racers. I've test-run them, but will have to get them on their intended planes in order to have any idea of their performance. Kim

Kim,

It's been a while since I worked on my .15s but as I recall, my best performing engine was sent to CA, where bearings with bigger balls were installed by one of the quarter midget guys - Ron Miller? (this was back in the early 80s). I also drilled out the venturi, don't remember which drill bit, but it was just slightly larger than the original hole. I also found that using the venturi like this required a bladder to feed fuel, as the engine could no longer draw on it's own. I filled the bladder with a syringe, used a hemostat to pinch the fuel line, got the engine turning with an electric starter, and then removed the hemostat, and it instantly revved up. I just used the mini pipe at first, and the acceleration with the 6 X 7 1/2 prop was breathtaking. I flew it on both a Sig Wonder and a Sig Doubler for sport, and later added the tuned pipe for some extra rpms on the Wonder.

One of my favorite things to do when flying was to try to cut off dandelion seeds as the Doubler followed the contour of the field, a few inches off the ground. I remember in Formula One flying Polecats with the left wing almost touching the ground as they rounded pylons 2 and 3 (this was before the rules forbid flying below the pylons), and I always loved flying really low at high speed. Anybody remember Pete Reed (hint: bare feet)?
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Post  John Goddard on Mon Oct 15, 2012 3:30 am

SuperDave wrote:IMO. prop selection depends not only upon the engine used but the airplane to be flown.

There are no hard and fast rules. That's why most of us experiment with different prop pitches and diameters.

Certainly do.

Ditto David
Trial and error it's the only way.
Very Happy
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Post  iskandar taib on Fri Nov 02, 2012 1:37 pm

There was a time when these were used in FAI Combat (control-line). I had one I bought used, back then people generally ran 7x4 nylon props cut down to maybe 6 1/2" to 6 3/4". Taipans worked well, but my favorite was the white Tornado. The modern Master Airscrew Scimimars would probably work as well.

You can still find Conquests on e-bay, they're fairly expensive as far as .15s go - around $90-120 depending on condition.

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