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Throttle cables/Rotax 912

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jpspencer(at)cableone.net
Guest

Posted: Thu Apr 23, 2009 5:48 pm Post subject: Throttle cables/Rotax 912

I have had a lot of problems keeping the carbs  synched on my 912 ULS equipped 701. I first installed the Zenith issued setup  with the torque tube and cables and never was able to keep the carbs synched  with that for very long. I found a pushrod setup that a fellow Zenith builder  came up with( can't remember his name but he was a prof from Texas). That design  used pushrods from the torque tube on the firewall forward to the carbs. I  doubted that would work for me cause every time the motor torqued in the mounts  I was afraid it would change the synch, but I tried it anyway, and found it as I  expected. So I abandoned that rig and tried to find a way to mount the torque  tube to the motor and actually did, using the 2 threaded bosses on the top rear  of the rear cylinders, and down braces from the rear of the carb cable holder.  But I abandoned that cause I was afraid the bosses would crack out; there isn't  much meat there; and that vibration would be transmitted to the carbs from the  downbrace. So I am back to square one and I guess about to go back to a cable  setup; after all that is what most of these things are running, and have since  forever ago, so that must be the "best" setup out there, right? My original  cables were spring loaded wide open as they came from ZAC; that was aggravating  as hell, fighting the throttle springs all the time and having to lock it every  time you wanted to take your hand off it.I am thinking about going to the spring  loaded idle type...have any of you done that? Seems like that might be a lot  more convenient particularly in the pattern. I don't worry about it quitting and  going to idle. I figure if it does then it was probably just "my time".If any of  you have experience with the spring load idle please pass it along. Also is it  essential that the cable housing/wires be exactly the same length as the ones  going to the other carb? I haven't seen anything on that, and it doesn't seem  necessarily that they should be but maybe so. I was using the vacumn gauge set  from Lockwood, which I found near useless because of gauge fluctuation, which on  my particular pair couldn't be adjusted out with the valves. I am using a  plastic tube loop with oil in it now which I think is reliable but am wondering  if it isn't way too sensitive. Your experience appreciated, and sorry to be so  long winded here. Thanks

 Joe in Mississippi

   [quote][b]

craig(at)craigandjean.com
Guest

Posted: Thu Apr 23, 2009 6:34 pm Post subject: Throttle cables/Rotax 912

Have you considered using this:  

   

http://www.mcfarlaneaviation.com/Details.aspx?ID=11744352&Article=199  

   

Throttle Control for Dual Carburetor Rotax Engines  

Innovative design allows a neat, clean installation without a clunky splitter box  

      [img]cid:image001.jpg(at)01C9C452.5AD264F0[/img]    Super-smooth      friction lock   
All      metal construction   
Teflon      lined for smooth, consistent control   
Available      in 4, 6, and 8 foot lengths      Measured from panel fitting to end of conduit,       wires extend 6 inches beyond conduit    
Easily trimmed to length    
Longer controls available upon request   
  
Two      knob styles available: Standard or Ball   
Manufactured      to the same quality standards as McFarlane's FAA-PMA parts    

   

      Specifications:    Panel      Fitting: 1/2-20 UNF x 0.67 inch thread   
Slip      Fit Conduit Terminals: 2 each with 1/4-28 UNF x 1.00 inch thread   
Conduit:      0.188 inch OD Teflon lined wound conduit   
Inner      Wire: Heavy duty 0.062 inch diameter, 1x7 stainless steel twisted wire per      MIL-DTL-87161   
Travel      (stroke): 3.75 inch maximum   
Design      Work Loads:       Push: Not Applicable (designed for pull loads       only)    
Pull: 10 lbs maximum   
  
Typical      Locking Force: 1 to 10 lbs (locking force dependent on friction lock      engagement)   
Operating      Temperature: -65 to 450 F    

   

-- Craig  

       

From: owner-zenith701801-list-server(at)matronics.com [mailto:owner-zenith701801-list-server(at)matronics.com] On Behalf Of Joe Spencer

 Sent: Thursday, April 23, 2009 7:48 PM

 To: Zenith701801-List(at)matronics.com

 Subject: Throttle cables/Rotax 912  

  

  

     

I have had a lot of problems keeping the carbs synched on my 912 ULS equipped 701. I first installed the Zenith issued setup with the torque tube and cables and never was able to keep the carbs synched with that for very long. I found a pushrod setup that a fellow Zenith builder came up with( can't remember his name but he was a prof from Texas). That design used pushrods from the torque tube on the firewall forward to the carbs. I doubted that would work for me cause every time the motor torqued in the mounts I was afraid it would change the synch, but I tried it anyway, and found it as I expected. So I abandoned that rig and tried to find a way to mount the torque tube to the motor and actually did, using the 2 threaded bosses on the top rear of the rear cylinders, and down braces from the rear of the carb cable holder. But I abandoned that cause I was afraid the bosses would crack out; there isn't much meat there; and that vibration would be transmitted to the carbs from the downbrace. So I am back to square one and I guess about to go back to a cable setup; after all that is what most of these things are running, and have since forever ago, so that must be the "best" setup out there, right? My original cables were spring loaded wide open as they came from ZAC; that was aggravating as hell, fighting the throttle springs all the time and having to lock it every time you wanted to take your hand off it.I am thinking about going to the spring loaded idle type...have any of you done that? Seems like that might be a lot more convenient particularly in the pattern. I don't worry about it quitting and going to idle. I figure if it does then it was probably just "my time".If any of you have experience with the spring load idle please pass it along. Also is it essential that the cable housing/wires be exactly the same length as the ones going to the other carb? I haven't seen anything on that, and it doesn't seem necessarily that they should be but maybe so. I was using the vacumn gauge set from Lockwood, which I found near useless because of gauge fluctuation, which on my particular pair couldn't be adjusted out with the valves. I am using a plastic tube loop with oil in it now which I think is reliable but am wondering if it isn't way too sensitive. Your experience appreciated, and sorry to be so long winded here. Thanks  

    

Joe in Mississippi  

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jpspencer(at)cableone.net
Guest

Posted: Fri Apr 24, 2009 7:16 am Post subject: Throttle cables/Rotax 912

Craig

 thanks for the link. I called them this morning  with questions. Looks like that may be the simplest solution yet. There is still  the problem of the springs but I am hoping to be able to go with a lighter one  with this cable setup; they thought so, and maybe be able to rig a simple spring  load idle control. I ordered one and will give it a try, and then report  back here to all the folks. It's a new production item and won't be available  for 1-2 weeks, but I will be glad to wait if it solves some  problems. 

 Thanks again. This internet thing is sumpin  else

  

 Joe

 will report.

  

   [quote][b]

arno7452(at)bellsouth.net
Guest

Posted: Fri Apr 24, 2009 7:23 am Post subject: Throttle cables/Rotax 912

Joe,

 You might want to talk with Jon Croke re:  lighter  throttle springs.

 Ken

  

  

  

  

  

 [quote]   ---

John Bolding

Joined: 23 May 2006
Posts: 281

Posted: Fri Apr 24, 2009 8:05 am Post subject: Throttle cables/Rotax 912

You guys from Mississippi are easy to impress   !!    

  

 LO&SLO   John

 [quote]   ---

jpspencer(at)cableone.net
Guest

Posted: Fri Apr 24, 2009 8:09 am Post subject: Throttle cables/Rotax 912

>You might want to talk with Jon Croke re:  lighter throttle  springs.

 	  Quote: 	
		  Ken

  
	


 Ken thanks. I will. I had tried lighter springs  early on and they wouldn't pull the slack out of the cables good enough to keep  the sync. Will see how they work with this new gizmo. BTW to use the new cable I  will give up the right side throttle control, but the few times I need it from  the pax side I can just reach across...

  

 Joe

 

   [quote][b]

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Fri Apr 24, 2009 9:19 am Post subject: Re: Throttle cables/Rotax 912

After a couple of instances of having my throttle wanting to creep up during warm up I switched from a friction system to a Vernier throttle system. It was a safety issue with me. Now it will not move unless I push the button and move it. It's nice in flight too as I just need to turn the knob to get small throttle changes. I only have one throttle now, but it is easy to reach from the passenger side if necessary.

_________________
Ron Lee
Tucson, Arizona

randy(at)rjhebertassoc.co
Guest

Posted: Fri Apr 24, 2009 9:41 am Post subject: Throttle cables/Rotax 912

Ron

Where do you have it located can you post a photo?



Do Not Archive



Randall J Hebert

Randall J Hebert & Associates, Inc

Consulting Engineers

Ph 337-261-1976  Fx 337-261-1977



--

dougsnash

Joined: 14 Apr 2008
Posts: 281

Posted: Fri Apr 24, 2009 10:16 am Post subject: Throttle cables/Rotax 912

Joe, I'll be a little more insistant about the not using lighter throttle springs.  Here is the link to Jon's story on the ch701.com website.



http://www.ch601.org/stories/croke_crash.htm



I agree that the throttle system on the 701/912 is a little wierd but it does work and modifications can be dangerous.



Doug MacDonald

CH-701 Scratch Builder

Final assembly.

NW Ontario, Canada



--- On Fri, 4/24/09, Joe Spencer <jpspencer(at)cableone.net> wrote:



 	  Quote: 	
		   From: Joe Spencer <jpspencer(at)cableone.net>

 Subject: Throttle cables/Rotax 912

 To: Zenith701801-List(at)matronics.com

 Date: Friday, April 24, 2009, 10:16 AM

 Craig

 thanks for the link. I called them this morning with

 questions. Looks like that may be the simplest solution yet.

 There is still the problem of the springs but I am hoping to

 be able to go with a lighter one with this cable setup; they

 thought so, and maybe be able to rig a simple spring load

 idle control. I ordered one and will give it a try, and then

 report back here to all the folks. It's a new production

 item and won't be available for 1-2 weeks, but I will be

 glad to wait if it solves some problems. 

 Thanks again. This internet thing is sumpin else

 

 Joe

 will report.

bobkat

Joined: 07 Sep 2008
Posts: 143
Location: Bismarck, ND

Posted: Fri Apr 24, 2009 10:51 am Post subject: Throttle cables/Rotax 912

I would have put a vernier type of dual cable throttle on had one been 

available, so I put the ordinary one on.  Doesn't creep, in fact I haven't 

adjusted it for months.

I got mine from ?Aircraft Spruce? or maybe it was Skystar themselves and I 

think they had them custom made.

On my 701 I used basically the same sytem as suggested by Zenith, but 

instead of that T-handle on both sides I put a regular friction  throttle 

cable on the left, left out that goofy friction block on that common rod 

and put on the stock T-handle to the right in case I ever wanted to fly much 

from there.  The Kitfox has the throttle control in the center so a second 

set up isn't an issue.

Rigged up like this you still have those safety springs on the carbs but 

never are aware they are there.  Anything happen to the throttle control 

mechanism and it'll get you down.   At altitude it may not be any big deal, 

but over water, trees or near the ground it could be a life saver!

---

bobkat

Joined: 07 Sep 2008
Posts: 143
Location: Bismarck, ND

Posted: Fri Apr 24, 2009 10:51 am Post subject: Throttle cables/Rotax 912

Don't worry about the springs, Joe!  I almost  pranged my kitfox because the original builder had removed them and installed a  solid cable push/pull system.  Worked perfectly until one day I had taken  just taken off when one of the solid cables broke and the carb on that side went  to idle.  I was able to slip it back in to the very short field with trees  on the far end, stopping with the spinner inches from a tree!    

 So the first thing I did was redo it to the  original system.  Those springs are there for a reason!    

 If you use that double cable system above pictured  (I put that one on the kitfox) you can easily adjust the throttle tension so you  are not aware that the springs are there.  And the carbs stay  balanced!  

 But those springs could save your life  someday.  Isn't there a picture somewhere of a 701 in a grove of trees  because lack of those springs?  

 The original system, especially using those two  cabled throttles works really well.  If it ain't broke, don't fix it.   But for safety's sake leave the springs in.  

 A bit off topic, but I heard that Rotax was working  on a single point throttle tttchemnt system.  That will make discussions on  the annoying double cable throttle problems and keeping the carbs balanced  obsolete!   Yeah!

  

  

  

 ---

jpspencer(at)cableone.net
Guest

Posted: Fri Apr 24, 2009 11:21 am Post subject: Throttle cables/Rotax 912

Ron, thanks. I originally had a vernier on mine from ACS  and the Zenith/Rotax supplied springs were so strong they somehow overcame the  vernier lock,... pulled the throttle forward! If I could get that to work on  mine that would be fine. I ran weaker springs(but not a whole lot  weaker) on mine for a while and if I remember correctly, the vernier  throttle would hold them, and I didn't have any problems with the throttle not  advancing, but did have trouble with carb sync..The only thing is it makes a  right seat throttle not usable, but I am ok with that, at this point. I still  have the vernier here, I might get it back out and try it again...thanks  again

  

 Joe

  

 >After a couple of instances of having my throttle  wanting to creep up during warm

up I switched from a friction system to a  Vernier throttle system. It was a

safety issue with me. Now it will not move  unless I push the button and move

it. It's nice in flight too as I just need  to turn the knob to get small throttle

changes. I only have one throttle now,  but it is easy to reach from the passenger

side if  necessary.



--------

Ron Lee

Tucson,  Arizona



   [quote][b]

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Fri Apr 24, 2009 4:26 pm Post subject: Re: Throttle cables/Rotax 912

I suspect something is not right with the Vernier throttle you have. Mine WILL NOT move unless the button is pushed. I have the original springs on my 912uls.

_________________
Ron Lee
Tucson, Arizona

jpspencer(at)cableone.net
Guest

Posted: Fri Apr 24, 2009 5:03 pm Post subject: Throttle cables/Rotax 912

>I suspect something is not right with the Vernier  throttle you have. Mine WILL

NOT move unless the button is pushed. I have the  original springs on my 912uls.



--------

Ron Lee

Tucson,  Arizona

  

 Don't know, could be...it was brand new from  ACS when installed...that would be my luck lately, it seems.

 I have come up with a new idea that may work  reliably w/o springs. Have some more parts on the way from ACS. Will  report.

 Good weekend all

 Joe

 



   [quote][b]

ggower_99(at)yahoo.com
Guest

Posted: Fri Apr 24, 2009 5:28 pm Post subject: Throttle cables/Rotax 912

about 240 hrs in my 701 with the plans throttle,  no problem at all.

  

 KIS.  Add only lightness and simplicity to any airplane.

  

 Saludos

 Gary Gower

  

 What can you fill a bucket with and make it weight less?

  

 Holes.  



--- On Fri, 4/24/09, MacDonald Doug <dougsnash(at)yahoo.com> wrote:



  	  Quote: 	
		  From: MacDonald Doug <dougsnash(at)yahoo.com>

Subject: Re: Throttle cables/Rotax 912

To: zenith701801-list(at)matronics.com

Date: Friday, April 24, 2009, 2:14 PM



 	  Quote: 	
		  --> Zenith701801-List message posted by: MacDonald Doug

<dougsnash(at)yahoo.com>

Joe, I'll be a little more insistant about the not using lighter throttle

springs.  Here is the link to Jon's story on the ch701.com website.



http://www.ch601.org/stories/croke_crash.htm



I agree that the throttle system on the 701/912 is a little wierd but it does

work and modifications can be dangerous.



Doug MacDonald

CH-701 Scratch Builder

Final assembly.

NW Ontario, Canada



--- On Fri, 4/24/09, Joe Spencer <jpspencer(at)cableone.net> wrote:



 	  Quote: 	
		   From: Joe Spencer <jpspencer(at)cableone.net>

 Subject: Throttle cables/Rotax 912

 To: Zenith701801-List(at)matronics.com

 Date: Friday, April 24, 2009, 10:16 AM

 Craig

 thanks for the link. I called them this morning with

 questions. Looks like that may be the simplest solution yet.

 There is still the problem of the springs but I am hoping to

 be able to go with a lighter one with this cable setup; they

 thought so, and maybe be able to rig a simple spring load

 idle control. I ordered one and will give it a try, and then

 report back here to all the folks. It's a new production

 item and won't be available for 1-2 weeks, but I will be

 glad to wait if it solves some problems. 

 Thanks again. This internet thing is sumpin else

 

 Joe

 will report.


	




      





	
	


         [quote][b]

ggower_99(at)yahoo.com
Guest

Posted: Fri Apr 24, 2009 5:32 pm Post subject: Throttle cables/Rotax 912

Sincerely I dont understand wht, in the first place they designed the engine with two carbs...

 Could be so simple to do as Jabiru, one single carb (same type)



--- On Fri, 4/24/09, BokKat <bobkat(at)btinet.net> wrote:



 [quote]From: BokKat <bobkat(at)btinet.net>

Subject: Re: Throttle cables/Rotax 912

To: zenith701801-list(at)matronics.com

Date: Friday, April 24, 2009, 2:30 PM



    Don't worry about the springs, Joe!  I almost pranged my kitfox because the original builder had removed them and installed a solid cable push/pull system.  Worked perfectly until one day I had taken just taken off when one of the solid cables broke and the carb on that side went to idle.  I was able to slip it back in to the very short field with trees on the far end, stopping with the spinner inches from a tree!   

 So the first thing I did was redo it to the original system.  Those springs are there for a reason!   

 If you use that double cable system above pictured (I put that one on the kitfox) you can easily adjust the throttle tension so you are not aware that the springs are there.  And the carbs stay balanced!  

 But those springs could save your life someday.  Isn't there a picture somewhere of a 701 in a grove of trees because lack of those springs?  

 The original system, especially using those two cabled throttles works really well.  If it ain't broke, don't fix it.  But for safety's sake leave the springs in.  

 A bit off topic, but I heard that Rotax was working on a single point throttle tttchemnt system.  That will make discussions on the annoying double cable throttle problems and keeping the carbs balanced obsolete!   Yeah!

  

  

  

 ---

jpspencer(at)cableone.net
Guest

Posted: Sat Apr 25, 2009 6:53 am Post subject: Throttle cables/Rotax 912

>KIS.- Add only lightness and simplicity to any  airplane

  

 Amen. In fact KISS is the 2nd reason(spring fight  is first) I would like to get away from the ZAC throttle design...if I can  make 2 Cessna type push/pull cables from a common throw work then I can get away  from the springs and torque tube, and all those bicycle type cables. That may  not work either but will give it a try. When mine was rigged without springs it  was so much nicer to fly...just like a normal airplane. But the  carbs wouldn't stay synched.Some of all this I think depends on your  expectations, as some are perfectly happy with the plans rig. Others  not.

 As to why 2 carbs on the 912...mainly I think it is  for high power/weight. But it does add a lot of complexity, as does  the water cooling and the external oil tank and all those oil lines and the  gearbox. Complicated and fussy...it's kinda like automatic that when you  decide to go with a Rotax you are giving up simplicity. I would have much  rather had a Continental or Lycoming but they are too heavy and won't  perform...that is if you are interested in radical, optimal STOL, anyway.  So I reluctantly bought the Rotax cause, for me anyway, radical STOL is about  the only reason for this plane's existence. There are better choices if  good all around performance and nice flying qualities are what one wants...but  man will it ever come out of the hole!! 

  

 Joe

 the green one on utube

   [quote][b]

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