Throttle pushrod
 

Hi again. Seems the topic on the airfoil got a bit heated as RCKen stated. Anyway I have a question regarding the pushrod which operates your carb/throttle.

Little background. We went flying today - made it a picnic day. I ran out of my 5% fuel and put in a friends 15%. Adjusted the engine etc. Anyhow, I took it off and in the middle of the flight I had no control over my throttle - nada. It was running full throttle and I couldnt cut it - used trim and throttle cut, but none would work - which we found out why after landing. Well there was just one way out of this one and that was to fly it until it runs out of fuel. So it did after about 10min in flight. Deadsticked it in, for a pretty decent landing if I may add.

What happened was, the little screw/plug thingy which is on the carb where the pushrod gets tied down to broke off - at WOT can you believe. Now, does one need to have that plug thingy (have no idea what it is called) or can one just use a Z bend?

RE: Throttle pushrod
 

Z-bends are actually preferred. EZ connectors might be EZ, but they're rarely reliable.

RE: Throttle pushrod
 

While a Z bend will work in many cases, it can also be a source of problems for two reasons. First, it can cause RF interference (metal to metal contacts rubbing or vibrating) and two, it is soon to be a sloppy connection as the holes are wallowed out by the poor fit between the Z bend and throttle. You will be much better off with a nylon clevis or a ball joint connection. If a slight angle between push rod and throttle arm, the ball joint is preferred.

RE: Throttle pushrod
 

.....and I could add, EZ connectors might be EZ, but they're NEVER reliable next to a vibrating engine.

http://www.airfieldmodels.com/inform...le_linkage.htm

http://www.airfieldmodels.com/inform...ware/index.htm

RE: Throttle pushrod
 

You're actually lucky the engine was at WOT when you lost your throttle linkage. You can always fly at WOT and you burn the fuel out faster. I was landing my Phoenix pattern ship and lost the throttle linkage (EZ connector on the engine I might add) when I was throttling down on final. Now I found myself in a difficult spot, too much throttle for landing, barely enough to stay airborne. I chose to stay airborne. When I landed I replaced my ez connector with a nylon clevis.

My preferred throttle set up is to use a cable as I often have to route the linkage around the fuel tank and sometimes around the cylinder head. If I use an ez connector, it will be on the servo end and I use a nylon clevis on the engine side so I don't get metal/metal contact.

RE: Throttle pushrod
 

Nothing wrong with EZ connectors, though I agree that they are not great for the motor side of the throttle linkage.

The ball connectors are a good idea instead.

I use the EZ connectors on the servo side of the throttle linkage all the time. It simplifies field adjustments.

For those who buy into the negative hype about EZ connectors, remember that all you have to do is to add a small wheel collet behind the connector ( and in front if you want to go even further ) to catch the pushrod if the connector let's go or slips.

Properly installed, I've never seen one slip, exhibit slop over time, etc.
If anything the star wheels are impossible to remove or loosen without destroying them.

RE: Throttle pushrod
 

I think I use pretty much every type of connector ever thought up, either now or in planes past. I like the EZs but I try to always use the metal keeper and not that little round plastic/rubber one. They do develope slop after a time though just like the Z-bend. I like to solder on a dubro clevis to one end of a cable then either use an EZ on the servo arm or solder on the threaded brass extension on one end and a threaded Dubro on that. Most anything you think of will work but you will want to look at other peoples set up to get some ideas of your own to try. I do like cable instead of solid rods though, I use the nylon or Nyrod on my gas engines, it works great for glow throttles too.

RE: Throttle pushrod
 

Yeah, as opjose suggested, I also use the ball-socket for my throttle. There is not a lot of torque with operating the throttle, so the ball socket is probably the best (in my opinion) for the throttle.

One thing you might take a look at is if there is a bind in the throttle linkage... is the servo trying to push the throttle arm further than it can go... which would involve a look at a throttle movement adjustment. I did an in-depth explanation of how I do my throttle to insure that once the servo stops moving, the throttle is at the exact end of the travel movement. I can post that again, if you would like.

CGr.

RE: Throttle pushrod
 

When using an EZ connector do you use a spot of Loctite blue on the threads of the adjusting screw?

RE: Throttle pushrod
 

Absolutely!

When I've seen people having problems with EZ connectors, I most often find that they have failed to put on lock-tite.

I think this is a MUST with them.

Most grub screws do a pretty good job at digging into the metal rod, making it immobile, so I've never had to try grinding a tiny bit of metal off, to form a flat spot, as a may do with axles.

On planes that I worry about possible slipping, I may add the second collet/collar for safety.

On pull-pull tail assemblies with the servo on the tail, I don't bother as if one were to slip, the other is there to hold the rudder for landing.... as in the following image...

http://origin-images.rcuniverse.com/.../lg-200508.jpg

I do periodically check for slop and tightness just to be safe.

Frankly the EZ-Connector is much stronger than the clevises on the rudder above.

RE: Throttle pushrod
 

opjose - very tidy, very tidy indeed! Thanks for sharing. What size is the pictured plane? I like the tailwheel assembly. Who makes it?

RE: Throttle pushrod
 

definatly if properly installed with the metal keeper there not coming off, you need to destroy the keeper to get it off a servo horn,I use the rubber keepers for temporary installations to make sure the push rod is working properly, so its easy to adjust from hole to hole, when I am satisfied with the operation I then use the metal ones.

RE: Throttle pushrod
 

The plane is a CMP Pro Marathon 20-24cc. I have a 26cc gasser in it.

The tail wheel assembly is one of these: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLKN8&P=7]Click me![/link]

That is correct $1.98 for the assembly AND the aluminum wheel... and it is almost trivial to install.

The plane has a 230oz/in servo on the tail @ 6v. The blue aluminum bell crank type horn is provided.

RE: Throttle pushrod
 

Thank you - it's now on my Tower WishLIst. Now, how to apply bellcrank technology - yet another NEW (old) idea. Ya just gotta love the options.

RE: Throttle pushrod
 

Got to agree, The EZ wth the metal keepr on the Servo, and a ball joint on the throttle arm. Cable inbetween.

Ilike to make adjustments to rod/cable length at the servo, not on the engine.For the reasons stated before, I really don't like the Z bends. An L bend with the clip over and latch on the wire keepers are much tighter and easyer to fit. I fly four strokes, and throttle arm to firewall distance is always an issue. A cable vs wire pushrod, with a solder on 2-56 adaptor cut short on both the thread end and the solder end, along with a nylon ball socket cut short on the thread end is what fits best for me. Because everythign is shortened up for Firewall clearnace, adjustments need to be made at the servo, not the engine end, and there the EZ conector fits the bill quite nicely.

Don

PS

Gene, how did those red L bend conectors work our for you?

Don

RE: Throttle pushrod
 

I don't think the servo is trying to push to far. I adjust my throttle setup as follows:

I open up my throttle to wide open on the Tx so that the servo goes the full travel and I open up the carb to where it is suppose to be when fully opened, then I tigthen the pushrod onto the servo and close it at the Tx - usually I then adjust my end points on the servo so that when I'm "closed" it will only travel to that point and not further. I will have a look into the ball-socket. Thank you

RE: Throttle pushrod
 

cgretired posted this on setting up your throttle servo, might help you

http://www.rcuniverse.com/forum/m_83...tm.htm#8375449

RE: Throttle pushrod
 

Ray:

Thanks for finding that. I was looking for it myself so I could save it in a document on my PC and use it in the future.

Good stuff.


One point, Korps: When using end points to do the adjustments, you may tend to lose resolution. It's best to get the most out of your mehcanical setup prior to doing any end point stuff. Just think about the throttle setup's before computer radios and no end-point adjustments. That's what you are trying to achieve.

CGr.

RE: Throttle pushrod
 

Please do! I am all ears! Thanks!

RE: Throttle pushrod
 

opjose wrote "If anything the star wheels are impossible to remove or loosen without destroying them. "

I discussed this issue with the DuBro rep at the AMA show one year.
He emphatically stated to NOT reuse the clips. Then you are asking for trouble.

I use the easy connectors regularly, I've never had a problem and I do follow his advice.

Good Luck,
KW_Counter

RE: Throttle pushrod
 

See post # 17 above. It has the link.

CGr.

RE: Throttle pushrod
 

Just a quick question. I spoke to someone today and mentioned to him my situation. Now does his statement seem true...he said that since I'm flying 2.4 that the vibration and friction causes by the metal to metal will not have an influence on the radio system and frequency?

RE: Throttle pushrod
 

Sure. Not only can I believe it but I have come to expect it from those little failure points. I check mine after every trip to the field. Throttle and nose-wheel steering is the only place I use those. And even then I shy away from them. But for some applications they certainly are handy.

RE: Throttle pushrod
 

I'd say that is accurate. Most vibration occurrs at a much lower frequency. But I still try and eliminate it in my aircraft.

RE: Throttle pushrod
 

Yup, I agree. Why invite problems?

The point of the statement though was how hard they are to remove even when you do not want to re-use them.

I find that I have to cut off the star wheels to remove the EZ connector from the horn.