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What gear ratio are you running?

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akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Sat Jun 13, 2009 6:27 am Post subject: What gear ratio are you running?

For the guys still loving the smell of 2 stroke smoke, what gear ratio and prop are you running?



I took someones advice and went to 3:1 instead of the 2.62:1 and was very disappointed in the results.  I lost about 5 mph on cruise, a couple hundred FPM on climb and fuel burn went up about 1 gallon an hour to cruise at the same speed.  I was just gonna live with it till I was out a couple days ago with the guy that bought my brothers KF II.  The KF on FLOATS out cruised my Avid on wheels.. He was running 5500 and I was at 5900 with him slowly pulling away.  I know I am pretty nose heavy and the 24" tires I have are more drag than normal, but to be out performed by a KF on full lotus floats was a down right embarrassment!

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Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
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Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Sat Jun 13, 2009 6:44 am Post subject: Re: What gear ratio are you running?

Classic 4, 503 Rotax, 3:1, 72" Warp 2 blade square tip.  Cruise at 5800 RPM is 85 mph true AS.  Climb is 750 ft/min at 1500' DA and 780 pounds gross.

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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sat Jun 13, 2009 8:12 am Post subject: What gear ratio are you running?

At 07:27 AM 6/13/2009, you wrote:

 	  Quote: 	
		  For the guys still loving the smell of 2 stroke smoke, what gear 

ratio and prop are you running?


	


Kitfox IV-1200, 582 grey, 3:1, 70" Warp 3 blade "constant speed", 

6800rpm WOT (at) 4500' density altitude (at)about 105 mph, very roughly 

6000rpm WOT ground static at 1500'. I've been told my plane's fast 

for a 582. It's pretty clean, aerodynamically.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 300 hrs. and counting

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Deceased K-IV 1200
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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun Jun 14, 2009 1:43 am Post subject: Re: What gear ratio are you running?

Leni,



You must be talking about me reco'ing those gears ?   



My Kitfox IV 582  3 to 1 Gearbox 68" Warp Square tip with 21" tires cruises  90 to 92 mph   5800 to 6000  rpm . fuel flow 18 litres per hour Summer, 20 litres a hour in winter

On Aerocet amphibs  cruise is 85-86  mph. 



I did try 2.62 gears once and lost at least 5 mph cruise if i recall.  I actually  thought I might gain some speed and was surprized otherwise. 



I think that you might find Skystar found the gain with going to 3 to  1 on a C box  from the 2.58 :1  B box was a huge improvement. 



You never did say what prop and settings that you used when you made the gear change?  I only made my pitch finer.

Dave

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dwight purdy

Joined: 10 Feb 2006
Posts: 85

Posted: Sun Jun 14, 2009 6:24 am Post subject: What gear ratio are you running?

That is impressive for a 503. I Just bought a two blade hub for my GSC 68 

in. tapered tip blades. Was trying to get more take off rpm, verses the 

three blade set up. I did but lost about 3mph at cruise.

  You must not have the same exhaust as the model I,II, and III. Your 

getting the full HP. I went from 85mph to 72 mph when I switched to a 503 

from the 532.

  Also saw about 2-3 mph difference between the tundra tires verses a 

standard tire. Are you running the large tires?



Dwight Purdy

Model II

---

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dwight
model II

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun Jun 14, 2009 9:10 am Post subject: Re: What gear ratio are you running?

68" big for a 503 but5 in two blade it might be better



Do you have strut fairings ?

dwight purdy

Joined: 10 Feb 2006
Posts: 85

Posted: Sun Jun 14, 2009 11:19 am Post subject: What gear ratio are you running?

Yes on the strut fairings.



Dwight Purdy

model II

---

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dwight
model II

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Sun Jun 14, 2009 6:15 pm Post subject: Re: What gear ratio are you running?

 	  Quote: 	
		  You must not have the same exhaust as the model I,II, and III. Your 

getting the full HP. I went from 85mph to 72 mph when I switched to a 503 

from the 532. 

Also saw about 2-3 mph difference between the tundra tires verses a 

standard tire. Are you running the large tires? 



Dwight Purdy 

Model II 	




Dwight, the exhaust elbow on my 503 has not been cut and shortened like I see on the 582's.  The builder's manual says it will all fit inside the cowl.  Mine does not.  I had to cut a hole for the exhaust elbow to stick out.



The prop is pitched for 6200 static and it goes to 6250 at best rate of climb which is 60 mph indicated.  Wing struts and landing gear are faired.  Tires are 18 X 8.50 X 8 Nanco.

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Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Mon Jun 15, 2009 8:18 am Post subject: Re: What gear ratio are you running?

 	  dave wrote: 	
		  Leni,



You must be talking about me reco'ing those gears ?   



My Kitfox IV 582  3 to 1 Gearbox 68" Warp Square tip with 21" tires cruises  90 to 92 mph   5800 to 6000  rpm . fuel flow 18 litres per hour Summer, 20 litres a hour in winter

On Aerocet amphibs  cruise is 85-86  mph. 



I did try 2.62 gears once and lost at least 5 mph cruise if i recall.  I actually  thought I might gain some speed and was surprized otherwise. 



I think that you might find Skystar found the gain with going to 3 to  1 on a C box  from the 2.58 :1  B box was a huge improvement. 



You never did say what prop and settings that you used when you made the gear change?  I only made my pitch finer.

Dave 	




Hmm Maybe lol.



I used my 72" IVO 3 blade when I first swapped, then took the 68" brolga off Bobs plane and tried it.  Same results.  Slower and higher fuel burn.  I have not put the fairings on the struts yet, but I flew all winter without them.  I did note that it is not as smooth with the 3:1 either, you feel every impulse.  Going back to 2:62 today and will post numbers later.

369PL

Joined: 08 Sep 2006
Posts: 20

Posted: Mon Jun 15, 2009 6:43 pm Post subject: Re: What gear ratio are you running?

I am running 3to1 with a 3 blade GSC prop. At 6000 rpm I indicate 110mph but I think the actual airspeed is 90mph.

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Tue Jun 16, 2009 2:09 am Post subject: Re: What gear ratio are you running?

I run  WOT  102 mph  at  2000 asl  with 21 " tires

Dave



 	  Guy Buchanan wrote: 	
		  At 07:27 AM 6/13/2009, you wrote:

 	  Quote: 	
		  For the guys still loving the smell of 2 stroke smoke, what gear 

ratio and prop are you running?



	


Kitfox IV-1200, 582 grey, 3:1, 70" Warp 3 blade "constant speed", 

6800rpm WOT (at) 4500' density altitude (at)about 105 mph, very roughly 

6000rpm WOT ground static at 1500'. I've been told my plane's fast 

for a 582. It's pretty clean, aerodynamically.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 300 hrs. and counting

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Tue Jun 16, 2009 2:16 am Post subject: Re: What gear ratio are you running?

Leni,  I am curious to how you got performance loss here. 



What  speeds did you have prior too and now ?    3 t o 1 should give you better take off and climb.   The Ivo Med 72" 2 blade  i find 6400 to 6500 static works well.



I have a set of 2.62 gears here , maybe I should try again but It hard for me to swap out from 3 to 1 that run ultra smooth with awesome performance. 



Dave

 	  akflyer wrote: 	
		   	  dave wrote: 	
		  Leni,



You must be talking about me reco'ing those gears ?   



My Kitfox IV 582  3 to 1 Gearbox 68" Warp Square tip with 21" tires cruises  90 to 92 mph   5800 to 6000  rpm . fuel flow 18 litres per hour Summer, 20 litres a hour in winter

On Aerocet amphibs  cruise is 85-86  mph. 



I did try 2.62 gears once and lost at least 5 mph cruise if i recall.  I actually  thought I might gain some speed and was surprized otherwise. 



I think that you might find Skystar found the gain with going to 3 to  1 on a C box  from the 2.58 :1  B box was a huge improvement. 



You never did say what prop and settings that you used when you made the gear change?  I only made my pitch finer.

Dave 	




Hmm Maybe lol.



I used my 72" IVO 3 blade when I first swapped, then took the 68" brolga off Bobs plane and tried it.  Same results.  Slower and higher fuel burn.  I have not put the fairings on the struts yet, but I flew all winter without them.  I did note that it is not as smooth with the 3:1 either, you feel every impulse.  Going back to 2:62 today and will post numbers later.

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Tue Jun 16, 2009 9:11 am Post subject: Re: What gear ratio are you running?

Mine is IFA so I tweek for 6500-6700 RPM on take off then tweek as needed to run the EGT's at 1100 for cruise.  



2.62 I was cruising 85 at 5800.  Now 5800 gives me about 72-74 MPH.  At take off 2.62 I was burning 6.5 GPH now take off is 7.6 GPH.  I could economy cruise at 5600 RPM for 70-72 MPH and burn 4.4-4.6 GPH, now a 5600 cruise gives me about 65 mph and 5.3 GPH.

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Tue Jun 16, 2009 10:22 am Post subject: Re: What gear ratio are you running?

 	  akflyer wrote: 	
		  Mine is IFA so I tweek for 6500-6700 RPM on take off then tweek as needed to run the EGT's at 1100 for cruise.  



2.62 I was cruising 85 at 5800.  Now 5800 gives me about 72-74 MPH.  At take off 2.62 I was burning 6.5 GPH now take off is 7.6 GPH.  I could economy cruise at 5600 RPM for 70-72 MPH and burn 4.4-4.6 GPH, now a 5600 cruise gives me about 65 mph and 5.3 GPH. 	




OK My  flow meter is in litres so I converted fro you. 



I got 3 to 1 numbers only  and US gallons 

all flights s (at) 2000 ASL or less

I run  1150 - 1200 EGT  on average in cruise

My prop is still at winter setting ( a bit finer than normal , but adequate right now )  

Also I run a tuned pipe which gives me more HP and better burn that the stock Rotax pipe which will run a bit rich.  Kitfox Exhasut is chopped as well costing a few more HP which I have gained back plus some.  A stock 582 Kitfox is likely about  58 HP rather than the 64 with a totally stock pipe that is not cut to fit cowl.  Your Avid might be different again -- who knows .



6000  rpm =   4.9 to 5 gal / hour  88 mph with 21 inch wheels.

5800  rpm =  4.5 to 4.7 gal / hour  86 mph

WOT    6400 climb out  30.1 litres hour =  7.93 gal hour



Gotta remember I am flying a Kitfox IV  and you have a Avid uncambered wing so  we not apples to apples here.

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Wed Jun 17, 2009 9:08 am Post subject: Re: What gear ratio are you running?

you are getting a better burn than me.  do you have the speed wing?  Thanks for posting the numbers!  Your numbers are alot closer to what I was getting running the 2.62:1.  I have been busy working on everyone else's projects so I have not had a chance to get my gears changed yet.  Hope to get them swapped in the next few days.

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Wed Jun 17, 2009 9:17 am Post subject: Re: What gear ratio are you running?

 	  akflyer wrote: 	
		  you are getting a better burn than me.  do you have the speed wing?  Thanks for posting the numbers!  Your numbers are alot closer to what I was getting running the 2.62:1.  I have been busy working on everyone else's projects so I have not had a chance to get my gears changed yet.  Hope to get them swapped in the next few days. 	


Not a speed wing,  just a  regular IV wing. Not undercambered but it has the leading edge cap on it  and strut fairings.  Also it has those not liked Droop tips  but I never heard anyone say that the hoerner tips have any performance gains really.



My fuel flow comes from navman which has proven to be fairly accurate over the last 3 or 4 years i had it .  



I actually was surprised that with 2,62 gears i slowed down . I likely posted it a few years ago when I did it and might be some numbers there.

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