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Twin Engine Firestar 2

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Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Mon Jun 26, 2006 9:40 pm Post subject: Twin Engine Firestar 2

Several months back, I posted my intention to install two Hirth F-33 engines on my Firestar 2.  The design goal was to end up with an aircraft that could at least maintain altitude on one engine and get to a landing spot if one of the engines failed.  The main issues I anticipated were vibration and the possible interaction of the overlapped propellers.  The engines were mounted on two struts that were secured to a flat plate that was mounted on the original Lord engine mounts.  In turn, the engines were flat plate mounted on their own set of mounts.



The right engine uses a prop extender to put the 53 inch Powerfin two blade prop 4 inches behind the left engine prop and allow the overlap.  Each engine is mounted 16 Â½ inches from the aircraft center line, and each propeller clears the aileron on its side by several inches.  The whole installation including the mounting system (excluding battery) weighs almost exactly the same as the Rotax 503.



The interaction of the two propellers crossing each other in opposite directions at the overlap was pretty much a gamble.  I couldnâ€™t find any information whether or not it would work.  In the early 80â€™s, I had the chance to do some thrust tests on the twin engine setup of the â€œPara Planeâ€ powered parachute.  The Para Plane installation was very well designed with two small single cylinder (Solo, if I remember correctly) engines mounted on both sides of a central set of concentric prop shafts.  The engines were connected to each shaft with a belt drive, and the props counter-rotated several inches apart.  We wanted to find out if the two counter-rotating props would affect each other at various RPMâ€™s of the two engines.  Interestingly enough, there was no measurable affect.  With both engines running at full RPM, the thrust (150 lb) was twice that of when one engine (75 lb) was run alone.  With that knowledge in my pocket, I figured overlapping props crossing in opposite directions would probably not interact appreciably.



It took several months of part time work to get the mounts set up and the throttles/choke, fuel system, and electrical system set up.  When all that was complete, I tied the Firestar securely, and started and broke in the engines.  I had some jetting issues because of being at 5,000 feet density altitude.  Matt Dandar, the owner of Recreational Power Engineering (where I purchased the F-33â€™s) gave me good technical support, and I got the engines running quite well.  With a spring scale tied to the tail wheel area, each engine measured about 150 lbs of static thrust when run alone.  The vibration level was about what you would expect from a single cylinder engine â€“ not unreasonable at all.  However, when both engines were run together at high RPM, the thrust was only a little over 200 pounds, and the vibration level was high.  It appeared that the area where the props overlapped and crossed was too turbulent for the props to work efficiently.



I had to wait several weeks for the local winds to drop below 10 mph, but finally had several days with light winds.  I trailered the Firestar to the Waimea Airport, which has almost a mile of paved runway.  My grass strip at home is only 700 feet long, and is not ideal for testing a modification of this magnitude.  Takeoff confirmed the static thrust test info.  The thrust was not nearly equal to the Rotax 503, and it should have been greater.  I climbed to a couple of thousand feet above the airport and alternately put one engine to idle, and the other to full throttle.  The yaw was easily controlled with rudder and I could just maintain level flight.  Vibration was about the same as with the Rotax 503.  



With both engines anywhere above 4,500 RPM, the vibration was severe enough that eventually something on the plane would fail.  I did a touch and go, and a full stop and called it a day.  The experiment was a failure, and I really donâ€™t see that there is much I can do to fix it.  I think it would work if the engines could be moved far enough apart to eliminate the propeller overlap, but that would require bigger struts (more weight and drag).  Also, the aileron gap would have to be extended (shorter ailerons) to provide sufficient clearance for the props.



I hate to post the details of a failed experiment for the world to pick apart, but believe it is good to get the info in the archives in case someone else in the future has the same idea.  I think it could be made to work with a concentric shaft counter-rotating setup like the Para Plane, but I donâ€™t have the machine shop resources available to build it.  Guess Iâ€™ll remount the Rotax 503 and go fly.  Mine has never missed a beat, and hopefully will continue in that mode.  In the meantime, Iâ€™m looking at the HKS 700E.



As a footnote, the Hirth F-33 engines are beautifully engineered packages, and Iâ€™m in no way being critical of them.  They are good engines, and Matt Dandar of RPE backs up and supports his product.  They would be my first choice as a light weight compact package for a single place trike, powered parachute, or other Part 103 legal ultralight.

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_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

rp3420(at)freescale.com
Guest

Posted: Tue Jun 27, 2006 6:28 am Post subject: Twin Engine Firestar 2

Dave,

Thanks for posting your report. I found it very interesting and appreciate your pioneering resourcefulness.



Tim Gherkins

FSII

--

jimhefner

Joined: 11 Jan 2006
Posts: 91
Location: Tucson, AZ

Posted: Tue Jun 27, 2006 6:49 am Post subject: Re: Twin Engine Firestar 2

Dave, I second Tim's comments.  Thanks for posting the results of your experiment.... very interesting indeed!   The engine mount setup looks impressive so you obviously put a lot of work into it.   Sorry it didn't workout like you hoped.

_________________
Jim Hefner
Tucson, AZ
Do Not Archive

biglar

Joined: 14 Jan 2006
Posts: 457

Posted: Tue Jun 27, 2006 10:31 am Post subject: Twin Engine Firestar 2

Sounds like a great effort, Dave.  Good on you.  I'll second the comment 

that it's too bad it didn't work out.                    Lar.



---

_________________
Larry Bourne
Palm Springs, CA
Building Kolb Mk IIIC
"Vamoose"

WhiskeyVictor36(at)aol.co
Guest

Posted: Tue Jun 27, 2006 6:36 pm Post subject: Twin Engine Firestar 2

In a message dated 6/27/2006 10:29:36 A.M. Eastern Standard Time,  rp3420(at)freescale.com writes:

  	  Quote: 	
		  With a    spring scale tied to the tail wheel area, each engine measured about 150 lbs    of static thrust when run alone.  The vibration level was about what you    would expect from a single cylinder engine Ã¢â‚¬â€œ not unreasonable at all.     However, when both engines were run together at high RPM, the thrust was only    a little over 200 pounds, and the vibration level was high.  It appeared    that the area where the props overlapped and crossed was too turbulent for the    props to work efficiently 	


 

 Dave,

  

 Food for thought.....

  

 Many years ago when I was young lad, I rode a small 2-stroke  motorcycle with point ignition.  Not knowing much mechanically, I messed  with the points and got the timing way out of kilter.  The engine would  sometimes run backwards!  So, maybe you could adjust the timing on one  of the two engines so it would turn in the opposite direction.  Maybe this  would help the props develop more thrust.  Just a weird idea, possibly  good for a few laughs.   

 Bill  Varnes

Original Kolb FireStar

Audubon NJ

Do Not  Archive

jspc78(at)yahoo.com
Guest

Posted: Wed Jun 28, 2006 10:40 am Post subject: Twin Engine Firestar 2

Hi Bill, Dave/All



I think Bill is onto something:  having the props

counter-rotate would have the props pass,moving in the

same direction with respect to the individual blades. 

Said another way, if the issue is the coverage of the

two blades, in the current config, with one descending

and one ascending causing a turbulent cavitation

‘zone’ then counter-rotating blades would smooth that

zone providing thrust in the zone where they cross.



Some two strokes can be set to run either way, but

must be supported by the manufacturer since there can

be many gotcha’s that could cause trouble—not readily

apparent to the us pilots.  Hirth engines tend to be

robust, straight forward designs, so if any two-stroke

will run the other way, I would expect a Hirth to.  



The final issue is the belt drive; the belt AND

sprockets must be able to transmit the HP going the

other way.  Again I would check with your engine

vendor.



Naturally you will need to somehow swap/reconfigure

the blades the make thrust the other way.



I suspect you might be able to solve this interesting

issue, please keep us posted whatever you decide. 

Your efforts have made for some of the more

interesting posts I have seen in awhile, thanks.



Jim Clayton        

California

Mark-3X, 912ULS.....Building

www.quantumwrench.com/Kolb.htm 

--------------------------------

--------------------------------

Food for thought.....

 

Many years ago when I was young lad, I rode a small

2-stroke motorcycle with point ignition.  Not knowing

much mechanically, I messed with the points and got

the timing way out of kilter.  The engine would

sometimes run backwards!  So, maybe you could adjust

the timing on one of the two engines so it would turn

in the opposite direction.  Maybe this would help the

props develop more thrust.  Just a weird idea,

possibly good for a few laughs. 

 

Bill Varnes

Original Kolb FireStar

Audubon NJ

Do Not Archive

Jim Baker

Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA

Posted: Wed Jun 28, 2006 11:49 am Post subject: Twin Engine Firestar 2

 	  Quote: 	
		   Some two strokes can be set to run either way,


	


Why go to all that trouble. 



_____________



  |--O     O---|

_____________

The above represents two engines, back-to-back on the 

mounting plate with the counter-rotating shafts mounted below 

the crankcases. 



 

 	  Quote: 	
		   The final issue is the belt drive; the belt AND

 sprockets must be able to transmit the HP going the

 other way


	


Not a problem...see above.



Jim Baker

580.788.2779

Elmore City, OK

WhiskeyVictor36(at)aol.co
Guest

Posted: Wed Jun 28, 2006 8:04 pm Post subject: Twin Engine Firestar 2

In a message dated 6/28/2006 2:41:44 P.M. Eastern Standard Time,  jspc78(at)yahoo.com writes:

  	  Quote: 	
		  www.quantumwrench.com/Kolb.htm 	


 

 Jim,

  

 What a great personal web page you have put together.  I just finished  looking over your page pertaining to your Kolb building project.   Wow!  You are really doing it right.  With all of the metal prep it  should last a lifetime.   

 Bill  Varnes

Original Kolb FireStar

Audubon NJ

Do Not  Archive

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Thu Jun 29, 2006 1:21 am Post subject: Re: Twin Engine Firestar 2

Thanks for all the positive feedback and brainstorming.  Here's my take on two of the ideas presented:



Turning one engine around and using belt drives to drive concentric drive shafts to counter-rotating props is an elegant solution, and I'm sure it would work.  The thing that bothers me about this method goes back to the original design criterion, that being to fly on one engine when the other "craps" out.  If one of those belts fails (and they do), it would most likely go through both of the counter-rotating props and take them both out.  Perhaps the belts could be enclosed or guarded somehow.



Changing the prop direction on one engine by reversing the engine might cut the interferance.  You would have to modify the timing plate inside the flywheel so the ignition advance would be correct for the change in rotation.  Right now, the sparks come at some number of degrees before top dead center, and if you just reversed the direction of rotation, the sparks would come at the same number of degrees after top dead center.  The engine might run with that degree of retardation, but wouldn't have much power.



Every solution I can come up with seems to bring a whole new set of problems.  I think I just have to look in the mirror and tell the guy there, "You blew a lot of work and money on that one - move on!"

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Thu Jun 29, 2006 4:17 am Post subject: Twin Engine Firestar 2

Reversing the rotation on a two-stroke is not as simple as just  

changing the ignition timing.



Sure, a two-stroke  can be caused to run backwards but making equal  

power in the opposite direction will require changing the cylinder  

ports to the opposite side also.



Because normally the crankshaft acts as a rotator of the fuel/air  

charge in the crankcase providing a supercharger effect to throw the  

fuel/air charge towards the open intake port side of the cylinder.



Changing the rotation will cause the fuel/air charge to be thrown  

towards the opposite side of the crankcase away from the intake port  

side. This greatly hinders the ability of the engine to "breathe"  

properly.

On Jun 29, 2006, at 5:21 AM, Dave Bigelow wrote:



 	  Quote: 	
		   

 <up_country(at)hotmail.com>



 Thanks for all the positive feedback and brainstorming.  Here's my  

 take on two of the ideas presented:



 Turning one engine around and using belt drives to drive concentric  

 drive shafts to counter-rotating props is an elegant solution, and  

 I'm sure it would work.  The thing that bothers me about this  

 method goes back to the original design criterion, that being to  

 fly on one engine when the other "craps" out.  If one of those  

 belts fails (and they do), it would most likely go through both of  

 the counter-rotating props and take them both out.  Perhaps the  

 belts could be enclosed or guarded somehow.



 Changing the prop direction on one engine by reversing the engine  

 might cut the interferance.  You would have to modify the timing  

 plate inside the flywheel so the ignition advance would be correct  

 for the change in rotation.  Right now, the sparks come at some  

 number of degrees before top dead center, and if you just reversed  

 the direction of rotation, the sparks would come at the same number  

 of degrees after top dead center.  The engine might run with that  

 degree of retardation, but wouldn't have much power.



 Every solution I can come up with seems to bring a whole new set of  

 problems.  I think I just have to look in the mirror and tell the  

 guy there, "You blew a lot of work and money on that one - move on!"



 --------

 Dave Bigelow

 Kamuela, Hawaii

 FS2, Rotax 503 DCDI





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=43694#43694

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Thu Jun 29, 2006 5:11 am Post subject: Twin Engine Firestar 2

One more idea before you decide to throw in the towel - The Rotax A 

drive gearbox relied on an adapter plate to mate the gearbox to the 

engine. If you could mate a gearbox to the Hirth, then you would get 

your prop turning the other way.

Or just substitute a Rotax 277 with gearbox for one of the Hirths? The 

277 makes 28 hp.

(Easy for me to say, since you are the one spending the money...)



Richard Pike

MKIII N420P (420ldPoops)



Dave Bigelow wrote:

 	  Quote: 	
		   



 Thanks for all the positive feedback and brainstorming.  Here's my take on two of the ideas presented:



 Turning one engine around and using belt drives to drive concentric drive shafts to counter-rotating props is an elegant solution, and I'm sure it would work.  The thing that bothers me about this method goes back to the original design criterion, that being to fly on one engine when the other "craps" out.  If one of those belts fails (and they do), it would most likely go through both of the counter-rotating props and take them both out.  Perhaps the belts could be enclosed or guarded somehow.



 Changing the prop direction on one engine by reversing the engine might cut the interferance.  You would have to modify the timing plate inside the flywheel so the ignition advance would be correct for the change in rotation.  Right now, the sparks come at some number of degrees before top dead center, and if you just reversed the direction of rotation, the sparks would come at the same number of degrees after top dead center.  The engine might run with that degree of retardation, but wouldn't have much power.



 Every solution I can come up with seems to bring a whole new set of problems.  I think I just have to look in the mirror and tell the guy there, "You blew a lot of work and money on that one - move on!"



 --------

 Dave Bigelow

 Kamuela, Hawaii

 FS2, Rotax 503 DCDI





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=43694#43694

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

slyck(at)frontiernet.net
Guest

Posted: Thu Jun 29, 2006 5:39 am Post subject: Twin Engine Firestar 2

Push-pull?????



do not archive

On 29, Jun 2006, at 9:08 AM, Richard Pike wrote:



 	  Quote: 	
		   



 One more idea before you decide to throw in the towel - The Rotax A 

 drive gearbox relied on an adapter plate to mate the gearbox to the 

 engine. If you could mate a gearbox to the Hirth, then you would get 

 your prop turning the other way.

 Or just substitute a Rotax 277 with gearbox for one of the Hirths? The 

 277 makes 28 hp.

 (Easy for me to say, since you are the one spending the money...)



 Richard Pike

 MKIII N420P (420ldPoops)



 Dave Bigelow wrote:

> 

> <up_country(at)hotmail.com>

>

> Thanks for all the positive feedback and brainstorming.  Here's my 

> take on two of the ideas presented:

>

> Turning one engine around and using belt drives to drive concentric 

> drive shafts to counter-rotating props is an elegant solution, and 

> I'm sure it would work.  The thing that bothers me about this method 

> goes back to the original design criterion, that being to fly on one 

> engine when the other "craps" out.  If one of those belts fails (and 

> they do), it would most likely go through both of the 

> counter-rotating props and take them both out.  Perhaps the belts 

> could be enclosed or guarded somehow.

>

> Changing the prop direction on one engine by reversing the engine 

> might cut the interferance.  You would have to modify the timing 

> plate inside the flywheel so the ignition advance would be correct 

> for the change in rotation.  Right now, the sparks come at some 

> number of degrees before top dead center, and if you just reversed 

> the direction of rotation, the sparks would come at the same number 

> of degrees after top dead center.  The engine might run with that 

> degree of retardation, but wouldn't have much power.

>

> Every solution I can come up with seems to bring a whole new set of 

> problems.  I think I just have to look in the mirror and tell the guy 

> there, "You blew a lot of work and money on that one - move on!"

>

> --------

> Dave Bigelow

> Kamuela, Hawaii

> FS2, Rotax 503 DCDI

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=43694#43694

>




 http://www.matronics.com/Navigator?Kolb-List

 http://wiki.matronics.com

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Thu Jun 29, 2006 6:12 am Post subject: Twin Engine Firestar 2

No - On the Kolblist website you can see he has two 28 hp engines 

mounted side by side a couple feet apart. Replace one of the Hirth 

engines with a geared Rotax 277, and then one prop turns one way, the 

other prop turns the other. Or put a gearbox on one of the Hirths, and 

then that prop turns the opposite direction from the other engine. (Belt 

drive, the prop turns the same rotation as the engine, but with gearbox, 

the prop turns opposite from engine rotation) He keeps his same basic 

setup, but eliminates the problem caused by both props turning the same way.



Richard Pike

MKIII N420P (420ldPoops)



robert bean wrote:

 	  Quote: 	
		   



 Push-pull?????



 do not archive

 On 29, Jun 2006, at 9:08 AM, Richard Pike wrote:



> 

>

> One more idea before you decide to throw in the towel - The Rotax A 

> drive gearbox relied on an adapter plate to mate the gearbox to the 

> engine. If you could mate a gearbox to the Hirth, then you would get 

> your prop turning the other way.

> Or just substitute a Rotax 277 with gearbox for one of the Hirths? 

> The 277 makes 28 hp.

> (Easy for me to say, since you are the one spending the money...)

>

> Richard Pike

> MKIII N420P (420ldPoops)

>

> Dave Bigelow wrote:

>> 

>> <up_country(at)hotmail.com>

>>

>> Thanks for all the positive feedback and brainstorming.  Here's my 

>> take on two of the ideas presented:

>>

>> Turning one engine around and using belt drives to drive concentric 

>> drive shafts to counter-rotating props is an elegant solution, and 

>> I'm sure it would work.  The thing that bothers me about this method 

>> goes back to the original design criterion, that being to fly on one 

>> engine when the other "craps" out.  If one of those belts fails (and 

>> they do), it would most likely go through both of the 

>> counter-rotating props and take them both out.  Perhaps the belts 

>> could be enclosed or guarded somehow.

>>

>> Changing the prop direction on one engine by reversing the engine 

>> might cut the interferance.  You would have to modify the timing 

>> plate inside the flywheel so the ignition advance would be correct 

>> for the change in rotation.  Right now, the sparks come at some 

>> number of degrees before top dead center, and if you just reversed 

>> the direction of rotation, the sparks would come at the same number 

>> of degrees after top dead center.  The engine might run with that 

>> degree of retardation, but wouldn't have much power.

>>

>> Every solution I can come up with seems to bring a whole new set of 

>> problems.  I think I just have to look in the mirror and tell the 

>> guy there, "You blew a lot of work and money on that one - move on!"

>>

>> --------

>> Dave Bigelow

>> Kamuela, Hawaii

>> FS2, Rotax 503 DCDI

>>

>>

>>

>>

>> Read this topic online here:

>>

>> http://forums.matronics.com/viewtopic.php?p=43694#43694

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

>

> http://www.matronics.com/Navigator?Kolb-List

> http://wiki.matronics.com

>





 http://www.matronics.com/Navigator?Kolb-List

 http://wiki.matronics.com

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

David.Lehman

Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA

Posted: Thu Jun 29, 2006 6:29 am Post subject: Twin Engine Firestar 2

Or fly a Kolb Flyer...

 



 

 On 6/29/06, Richard Pike <richard(at)bcchapel.org (richard(at)bcchapel.org)> wrote:  	  Quote: 	
		  --> Kolb-List message posted by: Richard Pike <richard(at)bcchapel.org  (richard(at)bcchapel.org)>



No - On the Kolblist website you can see he has two 28 hp engines

mounted side by side a couple feet apart. Replace one of the Hirth

engines with a geared Rotax 277, and then one prop turns one way, the 

other prop turns the other. Or put a gearbox on one of the Hirths, and

then that prop turns the opposite direction from the other engine. (Belt

drive, the prop turns the same rotation as the engine, but with gearbox, 

the prop turns opposite from engine rotation) He keeps his same basic

setup, but eliminates the problem caused by both props turning the same way.



Richard Pike

MKIII N420P (420ldPoops)



robert bean wrote: 

 	  Quote: 	
		   --> Kolb-List message posted by: robert bean <slyck(at)frontiernet.net (slyck(at)frontiernet.net)>



 Push-pull?????



 do not archive

 On 29, Jun 2006, at 9:08 AM, Richard Pike wrote: 



> --> Kolb-List message posted by: Richard Pike <richard(at)bcchapel.org (richard(at)bcchapel.org)>

>

> One more idea before you decide to throw in the towel - The Rotax A 

> drive gearbox relied on an adapter plate to mate the gearbox to the

> engine. If you could mate a gearbox to the Hirth, then you would get

> your prop turning the other way.

> Or just substitute a Rotax 277 with gearbox for one of the Hirths? 

> The 277 makes 28 hp.

> (Easy for me to say, since you are the one spending the money...)

>

> Richard Pike

> MKIII N420P (420ldPoops)

>

> Dave Bigelow wrote: 

>> --> Kolb-List message posted by: "Dave Bigelow"

>> <up_country(at)hotmail.com (up_country(at)hotmail.com)>

>>

>> Thanks for all the positive feedback and brainstorming.  Here's my 

>> take on two of the ideas presented:

>>

>> Turning one engine around and using belt drives to drive concentric

>> drive shafts to counter-rotating props is an elegant solution, and 

>> I'm sure it would work.  The thing that bothers me about this method

>> goes back to the original design criterion, that being to fly on one

>> engine when the other "craps" out.  If one of those belts fails (and 

>> they do), it would most likely go through both of the

>> counter-rotating props and take them both out.  Perhaps the belts

>> could be enclosed or guarded somehow.

>> 

>> Changing the prop direction on one engine by reversing the engine

>> might cut the interferance.  You would have to modify the timing

>> plate inside the flywheel so the ignition advance would be correct 

>> for the change in rotation.  Right now, the sparks come at some

>> number of degrees before top dead center, and if you just reversed

>> the direction of rotation, the sparks would come at the same number 

>> of degrees after top dead center.  The engine might run with that

>> degree of retardation, but wouldn't have much power.

>>

>> Every solution I can come up with seems to bring a whole new set of 

>> problems.  I think I just have to look in the mirror and tell the

>> guy there, "You blew a lot of work and money on that one - move on!"

>>

>> --------

 >>> Dave Bigelow
	


 	  Quote: 	
		  >> Kamuela, Hawaii

>> FS2, Rotax 503 DCDI

>>

>>

>>

>>

>> Read this topic online here:

>>

 >>> http://forums.matronics.com/viewtopic.php?p=43694#43694
	


	


-- 

ô¿ô  "Attitude is everything ~ pick a good one"...

_________________
Ã´Â¿Ã´

"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."

--- George Bernard Shaw

Jim Baker

Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA

Posted: Thu Jun 29, 2006 6:57 am Post subject: Twin Engine Firestar 2

If one of those belts fails (and they do), it would most likely go 

through both of the counter-rotating props and take them both 

out.  Perhaps the belts could be enclosed or guarded somehow.



Belts? Belts??? We doan need no steenking belts!!! Wonder 

what the ratio of that big ring gear would be driving another 

gear? A whole other set of problems now......backlash/chatter 

among them. Unless one were to soft couple the driven gear on 

the shaft.



Jim Baker

580.788.2779

Elmore City, OK

jimh474(at)earthlink.net
Guest

Posted: Thu Jun 29, 2006 7:13 am Post subject: Twin Engine Firestar 2

Who says you have to mount the engines on top of the wings? The creator of  the Kolb Flying Machine who has a bunch of multi-engine experience in  ultralights always mounts his multi-engines below the wing. Must be a big reason  why he does this.

  

 Ed, may pay for you to spend a dime and call Homer  and have a chat with him about multi-engines.

  

 He may save you a bunch of grief and  dollars

  

 Jim Hauck

  

 Do not archive

 

[quote] 

 

 

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pj.ladd(at)btinternet.com
Guest

Posted: Thu Jun 29, 2006 7:27 am Post subject: Twin Engine Firestar 2

eliminates the problem caused by both props turning the same way.>>



Hi,

didn`t the Wright Bros, whom some say flew first, just cross the drive 

belts.



Cheers



Pat



 do not archive





--

contrabassoon

Joined: 31 Aug 2006
Posts: 2
Location: Sausalito, CA

Posted: Thu Aug 31, 2006 11:50 am Post subject: Re: Twin Engine Firestar 2

Dave,



Great work, and kudos to you for it. I had the same idea for a 503 to F33 modification - but I have a slightly different idea. Since you have the F33's already in your possession, perhaps you might be interested in my idea? 



Basically, the idea is to have the engines mounted 30" off center and use 28" props on the F33's using direct drive (no belts). This will admitedly result in less prop efficiency, but save the cost / liability / and maintenance of the belts while virtually removing cross-prop interaction since there will be a few inches between them - even with them mounted in-line!



This is similar to the lazair of many years ago, but in a pusher configuration. 



Let me know if you are interested in trying this alternative, or perhaps interested in taking an offer for those F-33's???



My email is airfields at westerling dot com



Again, kudos on the good work and execution. My opinion is that redundant two strokes is indeed the way to go and much safer than the 503. I suppose the other alternative is to find a cricri (Cricket) that someone is selling   



Fair skies and smooth landings to you sir - Jonathan

Dave Bigelow

Joined: 29 Jan 2006
Posts: 103
Location: Kamuela, Hawaii

Posted: Fri Sep 01, 2006 1:08 am Post subject: Re: Twin Engine Firestar 2

Jonathan,



I have the two F-33's with Matt Dandar at RPE in Ohio for sale on consignment.  You can give him a call at 419-585-7002.  They are great little engines - really like the design and construction.



I'm working on an HKS conversion for my Firestar.  Should be getting the engine in several weeks.



Do not archive

_________________
Dave Bigelow
Kamuela, Hawaii
FS2, HKS 700E

contrabassoon

Joined: 31 Aug 2006
Posts: 2
Location: Sausalito, CA

Posted: Fri Sep 01, 2006 8:10 am Post subject: Re: Twin Engine Firestar 2

Dave,



Thanks for the quick reply. I'll call about those engines on Tuesday when I return. Good luck with the HKS engine. If I had the room in the engine compartment I'd be giving that a shot too!



- Jonathan

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