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throttle linkage for gas engines - 11/26/2003 4:02:57 AM   
sparkplug


 

Posts: 113
Joined: 7/10/2002
From: Canada
Status: offline 		Well keep in mind that I am new to gas but I have probably a silly question.

I noticed on my ZDZ engine that the throttle spring is very tough and would probably drain my battery needlessly during flight since the throttle servo is always under load.

Do people still use the carb with the spring or do you remove the spring so that the servo for throttle is not under continous load.

In the nitro world we do not have springs on carbs so I was just wondering.

Enjoy!
       Post #: 1

RE: throttle linkage for gas engines - 11/26/2003 7:56:22 AM   
TomCrump



Posts: 2200
Joined: 4/7/2003
From: Traverse City, MI, USA
Status: offline 		I take the springs off my gas engines. The spring is a hold over from the chainsaw or weed eater the engine was designed for.

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RE: throttle linkage for gas engines - 11/26/2003 12:18:54 PM   
H. Wayne S


 

Posts: 1147
Joined: 7/18/2003
From: Gray, GA, USA
Status: offline 		Throttle servo always under load ? does it buzz at mid throttle? I have three gas engines, all have the springs on the throttle. The spring on my ZDZ is not that strong, I personally would keep the springs on in case of linkage failure, Servo arm come off due to one forgetting to tighten the screw, Servo gears strip, arm brake, linkage break, end come off, there are at least five elements in the throttle set-up, thats a minimun of five things that could fail. Most gas engines we use today are manufactured for R/C use, and the manufacturer has elected to leave the springs on, SOME EVEN WARN AGAINST REMOVING IT BECOUSE IT HELPS HOLD SOME PARTS OF THE LINKAGE SYSTEM ON THE CARB. PLEASE READ YOUR MANUAL BEFORE YOU ENTERTAIN THE IDEA OF REMOVING IT.

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       Post #: 3

RE: throttle linkage for gas engines - 11/27/2003 12:22:57 AM   
Stick Jammer



Posts: 2251
Joined: 11/21/2002
From: Crete, IL, USA
Status: offline 		On a ZDZ that spring should be removed. As mentioned above, Walbro carbs are made for general purpose use, (chainsaws etc.) that's why the spring is there. I suppose you could leave it on if you want but it does put unnecessary strain on the throttle servo. You'll probably get smoother throttle operation without it. As far as any failures listed above, you should have at least one other way of killing the engine anyway. A choke servo is the easiest.

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       Post #: 4

RE: throttle linkage for gas engines - 11/27/2003 12:46:14 AM   
RickP



Posts: 1679
Joined: 1/1/2002
From: Levittown, NY, USA
Status: offline 		No Spring (DA-100) / Fiber optic kill switch....

RickP

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RE: throttle linkage for gas engines - 11/27/2003 1:32:55 PM   
vkmaynard


 

Posts: 96
Joined: 4/14/2003
From: Apex, NC, USA
Status: offline 		The ZDZ happy medium is to let the spring unwind 1/2 turn and land on the other side of the stop. That way you have a very very mild spring action that will mostly close the throttle in the event of linkage loss. I also have a choke servo. Be sure to remove the throttle stop screw. It simply causes problems.

Victor

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       Post #: 6

RE: throttle linkage for gas engines - 11/27/2003 5:15:55 PM   
TerrellFlyer


 

Posts: 1631
Joined: 3/19/2002
From: Terrell, TX, USA
Status: offline 		I throw the springs in the trash.

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       Post #: 7

RE: throttle linkage for gas engines - 12/23/2003 3:33:16 AM   
Aero-Junkie



Posts: 21
Joined: 1/24/2003
From: Lower Pottsgrove, PA, USA
Status: offline 		I had just bought a fuji 50 sb (Ya) the spring on the throttle was very tight and I said the same thing. I ask my local hobbie shop and they said that when a weed wacker / chain saw engine is converted they should pull the spring off! that no rc engine should have a spring on it. this will draw juice. (my 2 cents) often I hear poeple putting battery backers and extra rx bat. pacs to be cautious. thus ,defeats the purpose. A good day at the field I loose more battery juice than throttle linkage. have faith throw it out..................

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       Post #: 8

RE: throttle linkage for gas engines - 12/23/2003 9:48:52 AM   
BigBird1



Posts: 758
Joined: 2/26/2002
From: Knoxville, TN, USA
Status: offline 		If you take the spring off all together at full throttle plate will rattle in the throat, wearing the brass disc...It's better to take off the spring cut the hooks off of it and reinstall it...they use the spring to keep the disc centered..

If in doubt, pull up and down on the throttle arm with it at idle, it won't move up and down..move the arm to full throttle and pull up and down on it..their will be slack and will move up and down..

Just my two cents worth..

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RE: throttle linkage for gas engines - 12/23/2003 12:53:47 PM   
stomper


 

Posts: 2249
Joined: 12/13/2001
From: Clayton, NC, USA
Status: offline 		For Walbro carbs just unhook the spring but don't remove!

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RE: throttle linkage for gas engines - 12/23/2003 5:17:14 PM   
BobPhx



Posts: 211
Joined: 9/25/2002
From: Mesa, AZ, USA
Status: offline 		Agree with Stomper.
I had removed the spring from my DA100, worked fine. Unfortunately, had to send the motor in for a post-crash checkup. They put the spring back on and told me it was OK to not have it tension the butterfly, but it needed to be there to act as a spacer. According to DA, removing it can cause the butterfly to wear on the side of the venturi and eventually result in a rough idle. That's my .02.

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RE: throttle linkage for gas engines - 12/24/2003 12:37:41 AM   
Stick Jammer



Posts: 2251
Joined: 11/21/2002
From: Crete, IL, USA
Status: offline 		Hmmm. Interesting. I know a couple of people that have TONS of hours on their ZDZ's without the spring. No idle problems or any other for that matter.

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       Post #: 12

RE: throttle linkage for gas engines - 12/24/2003 2:13:16 AM   
mglavin



Posts: 5201
Joined: 11/29/2001
From: Elverta, CA, USA
Status: online 		OK, so lets consider all this unnecessary tension and or load on the throttle servo, SO WHAT! Lets draw a comparison as to what a servo realizes, a rudder servo gets a good workout and seems to hold up just fine... SO why wouldn't a throttle servo with much less load live through it. I mean come on how much load do you think that little spring really represents anyway. In any case leaving the spring in place offers several advantages, removing it doesn't seem to offer anything to me...

Or how about this. The spring puts tension on the arm or preloads the linkage, this keeps everything all warm and fuzzy and tightened up, and in return offers a very precise repeatable results for throttle control, together with an accurate precision servo you have a desirable setup. Even if your using low budget cheapy servo with geartrain slop there is some advanatge, IMO.

And yes the spring also preloads the throttle shaft preventing unwanted vibration and subsequent wear of the metallic surfaces within the bore of the carburetor...

< Message edited by mglavin -- 12/23/2003 9:15:41 PM >

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RE: throttle linkage for gas engines - 12/24/2003 7:38:34 AM   
BigBird1



Posts: 758
Joined: 2/26/2002
From: Knoxville, TN, USA
Status: offline 		Anyone done a pull test on a throttle arm with the spring on it to see what it takes to move it???
I'm not an engineer, but it would depend on the length of the arm as to how much juice that the servo would have to use to move it..and wouldn't the servo want to return to neutral much faster with the spring helping it?
Me, I throw away the idle screw..

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RE: throttle linkage for gas engines - 12/24/2003 7:18:49 PM   
sparkplug


 

Posts: 113
Joined: 7/10/2002
From: Canada
Status: offline 		I have added a longer control arm on the throttle and now it takes much less of the servo to move the throttle so it seems to be a good middle. I have a spring in case the ball link lets go so the engine will go to idle and I have some tension to keep things tight and I have little power drain due to the mechanical advantage of the longer arm.

All in all I think that should be ok. I am now breaking in my engine. This will be the first gallon of fuel which seems to be the most critical.

I have to say that I was very surprised by the power these little engines have compared to smaller glow engines like a .46ttpro. For such a small engine it really turns a 22x8 and creates tons of static thrust.

enjoy!

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       Post #: 15

RE: throttle linkage for gas engines - 8/14/2005 8:46:18 PM   
Crusty



Posts: 356
Joined: 11/9/2004
From: Metropolis , ARUBA
Status: offline 		The way to get the least torque requirement out of the setup is to use the biggest throttle lever length that you can still attain full throttle range with atv (epa) maxed out on that servo
im still on the fence re spring hooked/unhooked, currently been using unhooked, but there are definate advantages to a SMALL return tension,im gonna try to lighten the spring on a setup im doing now
edit...oops, sorry, I posted in a thred very old that my seearch threw up, sorry long day

< Message edited by Crusty -- 8/14/2005 8:50:36 PM >

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