Quiz - what don't I know about reedies (easy)
03-20-2017, 06:50 PM
#1
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Quiz - what don't I know about reedies (easy)
I'm not sure what to expect from this engine, but I thought it would be more..
The cylinder has what I am sure is a small 4 under one of the ports. It has the triple cut ports, open exhaust, milled top fins, SPI. According to the cylinder charts I've seen posted/linked to here, that's a TD cylinder. Using a TD head, 2 gaskets. Crank and bottom end standard. Red "Killer Bee" backplate. Grey 5-3, 25% nitro, 22% oil. Best I have seen after a few minutes run time is about 18,500 rpm. A steady setting I would leave it at, hmm maybe 18,100-18,200.
Isn't that kind of anemic for this setup? That's slower than the Tarno carbed, muffled TD I ran earlier this week, same fuel, same prop.. meaning it came off the TD then went on this. It was pushing 19k.
The fuel draw and needling with that JK Slikmount is great, will say that.
p.s. mylar reed
The cylinder has what I am sure is a small 4 under one of the ports. It has the triple cut ports, open exhaust, milled top fins, SPI. According to the cylinder charts I've seen posted/linked to here, that's a TD cylinder. Using a TD head, 2 gaskets. Crank and bottom end standard. Red "Killer Bee" backplate. Grey 5-3, 25% nitro, 22% oil. Best I have seen after a few minutes run time is about 18,500 rpm. A steady setting I would leave it at, hmm maybe 18,100-18,200.
Isn't that kind of anemic for this setup? That's slower than the Tarno carbed, muffled TD I ran earlier this week, same fuel, same prop.. meaning it came off the TD then went on this. It was pushing 19k.
The fuel draw and needling with that JK Slikmount is great, will say that.
p.s. mylar reed
03-23-2017, 01:35 PM
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I thought a stock TD would turn those well over 20k. Is a reedie with a TD cylinder and head down that much by comparison? Could be, mostly I just realized I don't have any reference points to clue me in.
03-24-2017, 07:34 AM
#8
Sounds about average. Imagine how boring a single port cylinder is on a tanked Baby Bee when the O rings leak, and it won't hold a steady peak. You can see my attitude for reedies. I used to race them, but never really was crazy about them.
03-24-2017, 12:32 PM
#9
I mainly ran reed engines as a kid and didn't have any tach back then, so I cannot really help with any tach numbers. But yours sounds good to me for a reed engine.
I you take a look at the Cox forum, they run "Tack Races" regularly and the numbers they get are all over the place. Showing how sensitive these engines can be to the set-up. Plus, I think even a TD will only just beat 20krpm on the grey 5x3 prop.
I you take a look at the Cox forum, they run "Tack Races" regularly and the numbers they get are all over the place. Showing how sensitive these engines can be to the set-up. Plus, I think even a TD will only just beat 20krpm on the grey 5x3 prop.
03-24-2017, 04:59 PM
#10
I have some numbers with the TD .049 '.051 with the Skorch I
But can't compare to the Lil Speedy being so light the prop really unloaded.
With the Skorch being more typical weight / size for 1/2A:
Stock .049 with APC 4.75 x 4 / RC cox carb and car muffler with standard glow head,
best pass 18,476 rpm20,900 rpm on APC 4.75 x 4 no muffler with HC cox plug
Gave up on that engine and broke in a new in the box version from the late 1960's:
APC 4.75 x 4 / 19,380 rpm in the hand static 25% nitro 21.4k into the wind to 23.3k rpm
down wind 2 shims HC plug. cox carb.
Then I converted the first TD used a RC high performance crank (lighter flywheel) and a
Killer Bee piston and cylinder the real deal actual lighten piston. Best pass jumped up to 24,160
after one in flight break in running rich, I reset the needle to sing mode and back off a hair and launched.
Cox rc carb and Nelson plug. On the third flight it was running just under 25k best pass the following weekend
I had a AP .061 on the plane ending the Cox testing in the air for the Skorch I
Later I revisited the TD of course with the Lil Speedy busting 30,492 rpm pass with a carbon / nylon
4.1 x 4.1 E prop with back cut.
Later I revisited the tuned pipe setup and achieved a static bench test
with a RC .050 / 25,193 rpm with a carbon 4x4.5 prop. I made a mistake
using the heavy aluminum bullet spinner could have hit 25.5k +
https://www.youtube.com/watch?v=zpkuNUdWjCQ Published on Aug 3, 2016
Cox TD .050 / Profi Tuned Pipe / 25,193 Static - HQ Prop 4 x 4.5
Static 7.3 oz thrust / .132 hp / 99w / 107.3 mph
Compared to the all mighty:
Published on Aug 10, 2015
.061 AME Norvel on a Profi Tuned Pipe
Non SPI version with 150 deg exhaust timing
APC 4.2x4 2oz of bench running prior to first flight
In the hand 25,436 / 96F summer day
Best level pass 27.683 / 105 mph
12oz all up weight 5ch plane with flaps
88sq. in 28in span
So far this is the fastest 3ch RC vid document stock TD .049 in the world with throttle sleeve.
HC cox plug but does have a KK aftermarket fine NV : With a HQ 4x4.5 and the pipe as shown
in the bench test it will fly faster this summer my guess around 130+ mph.
https://www.youtube.com/watch?v=5bCto2zdGUY Published on May 7, 2016
TD .049 /SPI / Throttle Sleeve Ports Allow SPI function / Prop 4.1 x 4.1N / 30% Nitro
Static 24,790 rpm / 7.4oz thrust / .127hp / 94.74w / 96.2 mph / 6.19oz RTF
Unloaded 30,492 best on Vid 1 / 118.4 mph per prop calc.
Doppler reading has it at 117mph per pass at 1:47mins into the vid.
Hard tank no pressure tap.
But can't compare to the Lil Speedy being so light the prop really unloaded.
With the Skorch being more typical weight / size for 1/2A:
Stock .049 with APC 4.75 x 4 / RC cox carb and car muffler with standard glow head,
best pass 18,476 rpm20,900 rpm on APC 4.75 x 4 no muffler with HC cox plug
Gave up on that engine and broke in a new in the box version from the late 1960's:
APC 4.75 x 4 / 19,380 rpm in the hand static 25% nitro 21.4k into the wind to 23.3k rpm
down wind 2 shims HC plug. cox carb.
Then I converted the first TD used a RC high performance crank (lighter flywheel) and a
Killer Bee piston and cylinder the real deal actual lighten piston. Best pass jumped up to 24,160
after one in flight break in running rich, I reset the needle to sing mode and back off a hair and launched.
Cox rc carb and Nelson plug. On the third flight it was running just under 25k best pass the following weekend
I had a AP .061 on the plane ending the Cox testing in the air for the Skorch I
Later I revisited the TD of course with the Lil Speedy busting 30,492 rpm pass with a carbon / nylon
4.1 x 4.1 E prop with back cut.
Later I revisited the tuned pipe setup and achieved a static bench test
with a RC .050 / 25,193 rpm with a carbon 4x4.5 prop. I made a mistake
using the heavy aluminum bullet spinner could have hit 25.5k +
https://www.youtube.com/watch?v=zpkuNUdWjCQ Published on Aug 3, 2016
Cox TD .050 / Profi Tuned Pipe / 25,193 Static - HQ Prop 4 x 4.5
Static 7.3 oz thrust / .132 hp / 99w / 107.3 mph
Compared to the all mighty:
Published on Aug 10, 2015
.061 AME Norvel on a Profi Tuned Pipe
Non SPI version with 150 deg exhaust timing
APC 4.2x4 2oz of bench running prior to first flight
In the hand 25,436 / 96F summer day
Best level pass 27.683 / 105 mph
12oz all up weight 5ch plane with flaps
88sq. in 28in span
So far this is the fastest 3ch RC vid document stock TD .049 in the world with throttle sleeve.
HC cox plug but does have a KK aftermarket fine NV : With a HQ 4x4.5 and the pipe as shown
in the bench test it will fly faster this summer my guess around 130+ mph.
https://www.youtube.com/watch?v=5bCto2zdGUY Published on May 7, 2016
TD .049 /SPI / Throttle Sleeve Ports Allow SPI function / Prop 4.1 x 4.1N / 30% Nitro
Static 24,790 rpm / 7.4oz thrust / .127hp / 94.74w / 96.2 mph / 6.19oz RTF
Unloaded 30,492 best on Vid 1 / 118.4 mph per prop calc.
Doppler reading has it at 117mph per pass at 1:47mins into the vid.
Hard tank no pressure tap.
Last edited by Pond Skipper; 03-24-2017 at 05:28 PM.
03-24-2017, 09:43 PM
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Good numbers for sure.. but I can't extrapolate from those. I think I have one more black 5x3 somewhere, I'll see how it compares, and maybe fire up a good running BW on the same props.
03-31-2017, 10:33 PM
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MJD, I don't think those numbers are bad at all for what you've got. The reed is a big limiter on these things. The TeeDee cylinder is helping because I believe that you're up over what a "product" engine will do normally with the same prop and fuel. So you are likely gaining somewhat.
Tuning the stuff you have can help too. I've always found that my best running reedies had really loose piston to cylinder fits. Like with a prime a few ounces of pressure on the prop will cause the piston to leak up and past TDC and back down to an open exhaust in something like 5 to 7 seconds. And I suspect that most who don't realize that is the high RPM setup of choice would likely consider them worn out and toss 'em. Note that this leakage is due only to the fit. Otherwise the piston and cylinder are warp and scratch free.
And no, I don't know why this is. Just that the highest soprano reedies of mine all leak like seives. It's so consistent that when I'm setting up a Cox reedie I look for the clean but leaky combos.
So if the cylinder to piston fit on your engine is free turning but close fitting it might be holding you back a little.
Tuning the stuff you have can help too. I've always found that my best running reedies had really loose piston to cylinder fits. Like with a prime a few ounces of pressure on the prop will cause the piston to leak up and past TDC and back down to an open exhaust in something like 5 to 7 seconds. And I suspect that most who don't realize that is the high RPM setup of choice would likely consider them worn out and toss 'em. Note that this leakage is due only to the fit. Otherwise the piston and cylinder are warp and scratch free.
And no, I don't know why this is. Just that the highest soprano reedies of mine all leak like seives. It's so consistent that when I'm setting up a Cox reedie I look for the clean but leaky combos.
So if the cylinder to piston fit on your engine is free turning but close fitting it might be holding you back a little.
04-01-2017, 07:49 AM
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Well, the slow leak in static conditions over a second or two is one thing, but at speed with oil flying around I can't imagine that amounts to anything other than a nice free running fit with a good dynamic seal - kinda makes sense.
One update, I thought the ball socket was fresh, apparently not, so I reset that and will see what that does.
This is really a case of being a fairly independent sport flier, running these engines all these years but never diving into these details any further than mild familiarity. The internet changes how we look at some things I suppose, when you get curious sit down in front of the oracle and start searching.
And it's refreshing to know there are still interesting things to learn about Cox reedies.. after all these years.
One update, I thought the ball socket was fresh, apparently not, so I reset that and will see what that does.
This is really a case of being a fairly independent sport flier, running these engines all these years but never diving into these details any further than mild familiarity. The internet changes how we look at some things I suppose, when you get curious sit down in front of the oracle and start searching.
And it's refreshing to know there are still interesting things to learn about Cox reedies.. after all these years.
04-05-2017, 10:37 AM
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I think you hit the nail on the head with the idea of a dynamic seal while running. And in truth when I think back on my reedie days I thought the same thing. But it has been a while.
