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Cox .074

Old 03-16-2014, 01:13 PM
  #26  
MJD
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I think the concept of using a milder larger displacement package to produce a 1/2A sized RC engine is a nice one. The Norvel .074 is the only one in the crowd that seems to suffer from the side effect of good performance.
Old 03-16-2014, 05:32 PM
  #27  
GallopingGhostler
 
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Originally Posted by MJD View Post
I think the concept of using a milder larger displacement package to produce a 1/2A sized RC engine is a nice one. The Norvel .074 is the only one in the crowd that seems to suffer from the side effect of good performance.
What you say, MJD is true, but with a sense of irony, no? From what I've heard of the Norvel 074, I think that it is a very sweet running engine, plus it is lightweight. Even the Norvel 40 seems to be a really sweet running engine. Will I go for them? I think not for now at least. I've got enough of old iron that I need to put them to use. I enjoy taking something and putting it to good use.
Old 03-17-2014, 05:48 AM
  #28  
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Originally Posted by aspeed View Post
A Turbo plug wouldn't work with a 1/4 - 32 hole in already? That is how mine was. I used the .09 TD plug, and it seemed ok. I forget which one I used for my test, and the difference in rpm. It is too cold to check things now. A burned out TD head could likely be used for the Turbo plug. Is that what you used?
No, the heads which are threaded for a regular plug cannot be converted to a Turbo plug, the hole is too large. A burnt out cox TD09 head could be converted I guess, I haven't taken of the insulator off one to check what they look like "inside".

I have used a dedicated Turbo head (cannot remember where I got if from now...) but the regular TD09 head should also work, might need some shims for a proper compression ratio though. Oddly enough they also put the regular plugs on the TD09 RC engines. Sure you get a nice and low idle but that is because they don't make any power with the regular plugs...

I've put an RJL .09 diesel head on the Queen Bee too, it runs very smooth...

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Old 03-17-2014, 07:23 AM
  #29  
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I had good experience with the QB .074. I used it on a canard pusher because I needed an engine that wasn't restricted on running direction. I used an APC 5.7 x 3 with great results, and ran it both with and without the muffler. It ran fine both ways - cleaner with the muffler. This motor simply does not like the loads of larger props - the result with a 7 x 3 was quite poor. All of this was on the standard head.

Scott
Old 03-17-2014, 02:49 PM
  #30  
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Mr Cox-you've beaten me to the draw as it were-sitting on a bench in the back room (along with far too many other test candidates) is Queen bee 074 with the Mecoa head-still to be run! How did yours perform? I've had this experiment in mind for some time-not the least because of the early success of reed valve diesels right back in the mid 1950s (Taifun Hurrikan, Blizzard, Hobby RS; Elfin 149,1.8 and 249; Frog 149 Vibramatic, Enya 06D, and the Jena 2 and 2.5cc to name a few)-the question seems not to have been asked as to WHY the Queen Bee is such a poor performer as a glow. We know by analogy with the other Cox 049 reed valve and front induction 049s that the induction and cylinder porting determines the ultimate power-and the TDs win because of their freer induction porting and more generous transfer volume (and that you can raise the reed valves' performance by fitting a TD cylinder and head-but not to the same level as the TD itself. Implicit in this observation is the deduction that the reed valve system itself provides a significant limitation to performance.............and essentially the issue is getting sufficient mixture past the reed and into the crankcase fast enough to charge the cylinder adequately to develop the maximum power it can.
So-given that diesels use a higher energy fuel, in lesser quantity than glow ignition-I'm speculating that the restrictions imposed by reed valve induction might not be as limiting in the case of a dieselised version as they are on the glow. Certainly the historic diesel examples I name above were (with the exception of the Hobby RS) outstandingly good performers compared with other front induction engines of the day (the 1.47cc Hurrikan was one of the most powerful 1.5 diesels around in its day (1956) until the advent of the PAW149-and the revised Oliver Tiger Cub appeared around 1960)
So the question I was hoping to answer is : Does the Queen Bee 074 make a better diesel than it does a glow?
.......there are of course other considerations-acquired from painful practice with the 049 reed valves-the crankshafts often break under the stresses of diesel operation-but the Queen Bee has a bigger crank with a thicker web, so will be proportionately stronger

ChrisM
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Old 03-17-2014, 04:38 PM
  #31  
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I think the reed valves certainly have a place and mated up to the right airframe they do quite nicely. They are certainly not racing engines except for the classes from which they are specified. Back in the early 1970's I found the Cox .020 Pee Wee would pull a small R/C plane at the same speed with better economy on a TF 5.25x3 prop as it would the Cox specified 4x2 prop. At elevation, the .049 Black Widow would haul my Q-Tee at 6,500 feet (1,981 m) on a 6x4 prop. (But it struggled with anything less, 5x4, 6x3, etc.) At that elevation I was within its power curve with the wider prop.
Old 03-18-2014, 12:24 PM
  #32  
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Originally Posted by ffkiwi View Post
So the question I was hoping to answer is : Does the Queen Bee 074 make a better diesel than it does a glow?
I have only fired it up on a prime a few times, to get a feeling for how it runs. It seems to run very smooth, but I have not tached it to get a proper power estimate. I need to get some fresh fuel and then I'll give it another go.

The read clamp was/seemed a little restrictive, I just stretched that out a little and with the Turbo head there doesn't seem to be anything seriously wrong with the engine apart from the high weight. But surely they could have gotten more power out from it if they had used the regular TD tricks, such as boost flutes for the transfer ports and a tapered cylinder etc.
Old 03-27-2014, 10:01 PM
  #33  
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I have a queen bee ran it in a boat it had more torque than a TD low end for sure no stalls on launch. Weight in a boat was not an issue was why I tried it. I have another one now in mint condition and have read 25% nitro with a 6x4 can get it running happy at 18.4k static. I have ran the QB in a plane back in the 90s the plane flew fine just not a speed demon. If you add a pressure tap on the tank a nelson plug and 35% nitro I would imagine a modern design 6x4 could have the right plane design flying reasonably fast. Has any tried a .09 cylinder and piston to see if it will work the the crank and case?
Old 03-30-2014, 09:34 PM
  #34  
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Ok had to do it took apart one of my TD.09's and a QB to review the piston rods. A queen bee can accept a TD piston cylinder screwed in its crankcase. A steel tube shim could be press fitted into the .09's piston rod or over the cranks pin and may stay put. Here's a pic.
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Old 03-31-2014, 01:53 AM
  #35  
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Yes, the QB and the TD09 have the same threads in the cylinder towards the case and glowhead. A brass bushing could be made for the low-end, I guess, but one would also have to consider timing and compression ratio. I haven't checked the stroke, are they the same?

Considering how hard it is to find a good piston liner for a TD09, one might as well use the TD engine and put throttle on the exhaust. Even the TD09 RC is in fact slightly lighter than a Queen Bee...!

Last edited by Mr Cox; 03-31-2014 at 01:56 AM.
Old 03-31-2014, 06:41 AM
  #36  
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Then there is the counterweight needed to balance the bigger piston.
Old 03-31-2014, 04:37 PM
  #37  
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lol poor ol QB..

Aspeed I thought about that too but was already horizontal for the evening. My conclusion was to cut out the opposing side of the flywheel to mimic the TD triangle mod inducing more weight to compensate. Also could bore out the front crankcase to enjoy the benefits of a front bearing.
I wanted to mod the thing to freak out my fellow flyers as they scoff at the well known weak QB .074
The modified QB .09 would scream on a pipe. Here is the conceptual pic.
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Old 03-31-2014, 05:02 PM
  #38  
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Dr. Cox you are correct what a shocker lol. You would think the extra steel with the 09 carb cylinder size piston would have the 09 further apart but not so the numbers dont lie
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Old 03-31-2014, 05:16 PM
  #39  
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Not sure what a reedy does on a pipe. The pressure wave would go back into the cylinder, hit the reed, push it back, SPI, something to try maybe. Reedies usually start to float at around 18,000 rpm.
Old 03-31-2014, 05:38 PM
  #40  
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I did not see the bottom of the QB cylinder clearing the exhaust port appears to have no SPI.

I think if you removed the muffler, intake screen, add nelson plug and bored out the front end to accept a bearing the QB could snarl enough to be liked on 30% nitro. As a diesel with a front bearing no screen or muffler the engine could swing a 8x4 prop and shine in the sky.

Last edited by Pond Skipper; 03-31-2014 at 05:45 PM.
Old 03-31-2014, 06:04 PM
  #41  
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I don't think it would be worth the effort for the bearing, but a bigger carb might help a bit if it could be engineered in.
Old 03-31-2014, 06:23 PM
  #42  
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Yes the bearing would only be worth doing if you go diesel to swing a big prop. I did think about the carb issue a while back and bought a carb rebuild kit. Notice the plastic ring to keep the screen on, without it the carb shows big improvement for performance could run without the pipe and file out the two drill holes to allow the engine to breath with some goo control leaving the muffler body on. Here's a pic. Note taper in the inside wall of the venturi. Note you save 14.6g thats tad over a half oz just removing the muffler pipe.



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Last edited by Pond Skipper; 04-01-2014 at 11:21 AM.
Old 03-31-2014, 06:48 PM
  #43  
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Yep yep Aspeed a pic is worth a thousand... er or so rpm
With a simple throttle sleeve you can keep it RC and allow it to breath for a few more rpm.
Pic of a TD 09 venturi and needle
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Last edited by Pond Skipper; 04-01-2014 at 11:19 AM.
Old 04-01-2014, 04:50 AM
  #44  
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How much does a muffler cut down the performance of a TD? Especiall since it has sub porting. I suspect that works well with a tuned pipe, but nor sure about a normal muffler.
Old 04-01-2014, 06:47 AM
  #45  
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I dunno, in my limited experiences with mufflers, .020 and .049 reed valve engines and my Tee Dee .020, mufflers did remove some of the top end RPM. It's why that I usually flew without mufflers. Unless it is a tuned pipe, I think it reasonable to expect some power losses on the Tee Dee. Whether that is significant enough, best test is to simply try it on an airplane.
Old 04-01-2014, 07:07 AM
  #46  
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I ran a cox 074 on a eclipse glider at 5280 ft elevation. It flew well on it, throttled well. I ran 20% nitro with 25% oil. These engines were never designed as high performance, but work well as designed. I have a NIB 074 that is going on a Q Tee. will post performance when I fly it.
Old 04-01-2014, 07:39 AM
  #47  
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I recall trying to fly a 2m glider on one at 6200' elevation - marginal climb. Substituted a TD and tank mount and off to the races. But all that aside, it is a sport engine designed to produce "1/2A power" in a small throttled RC engine package. It does that reasonably well without any particular standout feature or performance I guess.
Old 04-01-2014, 12:49 PM
  #48  
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I've got an unbuilt House of Balsa 2x2 two meter wingspan glider, that I plan to in future to power with nitro, most likely my Fuji 099S-II ABC cross scavenge RC engine. I couldn't imagine using less power than that, although some have told me I ought to get by with an .049 reed valve due to the glider's aerodynamic efficiency. Being at 4,300 feet elevation does make upsizing more feasible.

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