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RE: Throttle connections - 2/29/2012 3:29 PM   
acdii


 

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Oops I forgot to set the email notice and forgot I had posted this. 

The servo setup I have posted in the Deweyville thread over in Vintage. I have the servo link on the innermost hole on the arm    I need to figure out how to setup my Futaba 8FGS now so the throttle is more linear to the stick movement.  Right now I have it smooth from trim down to full throttle and trim up without binding, so the servo throw is good, now I just need to match the stick up to it. 

My biggest concern though that I posted about is the slight bend I had to put into the threaded rod to make it smooth open to close.  I really dont want to have to tear it all apart again to put new rods in since I have everything neatly assembled now. Getting the tank in place was a pain with the rods in the way.  I highly doubt heat will be an issue, there is no cowling and the gap is larger than it looks in the picture.  It also swings a 17" prop. Plenty of air movement. 

With the size of this planes wing, I most likely will be flying at half throttle or less, and the plane is not very heavy for its size, I still need to weigh it, but it balanced out pretty good front to back and side to side. 

3 items left before ground testing and maiden, balance the prop, repair and recover the elevators, and fine tune the radio throws. 


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RE: Throttle connections - 2/29/2012 4:01 PM   
a1pcfixer



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quote:

ORIGINAL: catflyer

Why not offer him a little advise on setting the end points that he can use on the rest of the servos in the plane so he can at least get it running then move on to theory about setting the correct geometry for the linkages instead of having a perfectly linear feeling throttle that did him no good as the plane became a gas powered lawn dart after the receiver battery failed.



Because first & foremost the throttle linkage geometry should be your very first step. Adjust end points &/or throttle curves come later on.
Btw it's NOT a theory either.

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RE: Throttle connections - 2/29/2012 4:15 PM  1 votes
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quote:

ORIGINAL: acdii

The servo setup I have posted in the Deweyville thread over in Vintage. I have the servo link on the innermost hole on the arm    I need to figure out how to setup my Futaba 8FGS now so the throttle is more linear to the stick movement.  Right now I have it smooth from trim down to full throttle and trim up without binding, so the servo throw is good, now I just need to match the stick up to it.

My biggest concern though that I posted about is the slight bend I had to put into the threaded rod to make it smooth open to close.  I really dont want to have to tear it all apart again to put new rods in since I have everything neatly assembled now. Getting the tank in place was a pain with the rods in the way.


If you use a tach and run to WOT, you'll notice that for roughly the last 20-30% of carb arm movement there's little increase in eng rpm.
Like ahicks stated, most eng response is in the throttle arm's first 1/4 of movement. At roughly 1/4 carb arm movement, you'd be shooting to have your tx throttle stick at/near 1/2 throttle.

You got step one done (throttle/servo arm linkages), now just fine tune it in the tx, might not need much.
Your on the right path!

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RE: Throttle connections - 2/29/2012 5:30 PM   
speedracerntrixie


 

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quote:

ORIGINAL: a1pcfixer


quote:

ORIGINAL: acdii

The servo setup I have posted in the Deweyville thread over in Vintage. I have the servo link on the innermost hole on the arm    I need to figure out how to setup my Futaba 8FGS now so the throttle is more linear to the stick movement.  Right now I have it smooth from trim down to full throttle and trim up without binding, so the servo throw is good, now I just need to match the stick up to it.

My biggest concern though that I posted about is the slight bend I had to put into the threaded rod to make it smooth open to close.  I really dont want to have to tear it all apart again to put new rods in since I have everything neatly assembled now. Getting the tank in place was a pain with the rods in the way.


If you use a tach and run to WOT, you'll notice that for roughly the last 20-30% of carb arm movement there's little increase in eng rpm.
Like ahicks stated, most eng response is in the throttle arm's first 1/4 of movement. At roughly 1/4 carb arm movement, you'd be shooting to have your tx throttle stick at/near 1/2 throttle.

You got step one done (throttle/servo arm linkages), now just fine tune it in the tx, might not need much.
Your on the right path!


You can eliminate some of this by proper needle settings. Most guys want their engine to transition from idle with little to no warm up so the idle screw is usually set up a bit rich. As a result of this they eliminate the mid range burble by squeezing down on the high speed needle too much. This shows up as no additional fuel getting to the engine past 3/4 to 7/8 throttle. I usually set mine up where they require a short warm up before they will transition. Not usually a big deal as we don't run our gassers at wide open for very long but it does show up as a dead spot at the end of the throttle stroke.


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RE: Throttle connections - 2/29/2012 5:49 PM  1 votes
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Oh I know T.O.M has to be lurking out there like one of them big catfish on MUD CATS His info is priceless but but it comes with a price It helped me get it right, 4-40 rod, bolt on ball link on both ends and proper geometry will work everytime. I'm no expert but I do search RCU


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RE: Throttle connections - 2/29/2012 5:58 PM   
a1pcfixer



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quote:

ORIGINAL: raptureboy *

................I'm no expert but I do search RCU


Good for you!
Just for that, you get a gold star!

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RE: Throttle connections - 2/29/2012 9:27 PM   
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Thanks Scott. the Mcmaster ones look like winners. Dan

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RE: Throttle connections - 3/2/2012 3:24 AM   
ahicks


 

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quote:

ORIGINAL: speedracerntrixie


quote:

ORIGINAL: ahicks


quote:

ORIGINAL: speedracerntrixie
adjust the length so that at 1/2 stick and with the servo arm at 90 degrees to the servo and the throttle butterfly is 1/2 open or just slightly more.


Realizing this is off topic, but this exact thing has been the problem causing many discusions recently from guys having trouble here. This plan is almost guaranteed to lead to a WAY sensitive throttle stick, especiall just off the idle, making adding any kind of throttle adjustment during the short final/flare an exercize in correcting a big balloon in your landing.

The engine's power is not delivered in the same percentage relative to the throttle opening. The engine is making nearly full power at half open throttle! You need to compensate for that using your linkage geometry. See the diagrams in post #21 in the sticky at the top of the gas engines heading. Do NOT set your linkage up as above!



Wow, I just got a big laugh here. Seems I have been setting up my throttle all wrong for oh........about 15 years. Maybe if I had set it up correctly I would have done better then 2nd place In IMAC advanced class in my region in 2006. Maybe instead of finishing the season with a contest record of 3 first, 3 second and one 3rd finish, I could have won them all.

Ok All kidding aside, yes gassers tend to hit the wall at around 3/4-to 7/8 butterfly opening. Thats why I told him to set it up so that at 1/2 stick he would more likely be at about 3/4 power. This is where most guys, especially new guys to gassers tend to fly. Being that it is half stick, it will be easier to find that '' Cruise setting '' on the TX. If it needs further adjustment, it can easily be done from here with a throttle curve if his TX has that function or with a sub trim. Either way the method I described will get him closer to final settings then what he is currently doing or some of the other things I have read here.



Maybe, the differnce in our approaches to throttle setup comes from different objectives? You sound like you may be searching for a soft "cruise setting"? The approach I'm suggesting sets up a soft spot that allows one to add power in the flare without so much fear/likelyhood of balloning? If your normal landing is a power off approach, you may never need/notice what I'm suggesting. Not trying to be critical, only understand what you're doing. Been flying a while too - and one of the things I enjoy most about contributing to strings like this - is learning something new all the time. I used to set my nitro engines like you're suggesting, but gassers proved that method wasn't going to work pretty early on - for my purposes anyway. -Al



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RE: Throttle connections - 3/2/2012 4:13 AM   
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I think we are reaching for the same result just in a different manner. My needs are a smooth linear throttle response. What I have not seen in your description and the description in the stickey is where the servo arm is positioned in relationship to the throttle arm position. If you note I described that at roughly 1/2 throttle, the servo are is 90 degrees to the servo. This means that at half stick is where the throttle is going to be most responsive. As the servo arm travels in either direction away from center, the response softens. The more travel, the more softening. So one thing that we can agree upon is that it is best to sort out the travel with ATV being set at 100% or better. Not always possible depending on throttle arm length.  I have posted up a link Of a landing with my 33% Laser. You will notice that I do work the throttle quite a bit for decent control once AOA has been established. Even though it is in a confined area, there is no balloning and the flare is minimal.


http://www.youtube.com/watch?v=bpm4cwaFrAg


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RE: Throttle connections - 3/2/2012 1:07 PM   
ahicks


 

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quote:

ORIGINAL: speedracerntrixie

I think we are reaching for the same result just in a different manner. My needs are a smooth linear throttle response. What I have not seen in your description and the description in the stickey is where the servo arm is positioned in relationship to the throttle arm position. If you note I described that at roughly 1/2 throttle, the servo are is 90 degrees to the servo. This means that at half stick is where the throttle is going to be most responsive. As the servo arm travels in either direction away from center, the response softens. The more travel, the more softening. So one thing that we can agree upon is that it is best to sort out the travel with ATV being set at 100% or better. Not always possible depending on throttle arm length. I have posted up a link Of a landing with my 33% Laser. You will notice that I do work the throttle quite a bit for decent control once AOA has been established. Even though it is in a confined area, there is no balloning and the flare is minimal.


http://www.youtube.com/watch?v=bpm4cwaFrAg




No 50cc experience here. Mine, other than a Quadra 42, are all 20-30cc. Wondering if the care and feeding of a 50+cc engine might be different than the smaller ones? That might account for our different setups as well. The setup I prefer is done with the stick and throttle both on idle, servo arm pointed nearly straight at the carb (assuming carb arm is pointing at the engine when at idle, not away from it). Your "soft spot" emphasis will be mid throttle, mine, idle.

Also, to lend credence to the potential for differences 50cc vs. 20-30, I saw your low speed needle adjustment would give one of my engines fits, almost certainly lead to the dreaded throttle "hang" so many guys are having trouble with. These little guys I have need to run very rich down low so they cool off very quickly when throttled back. They'll run OK as you describe, but take their darn sweet time cooling off to the point where they will come back down to a full idle. Not being critical of your adjusting method, only pointing out it's way different than what seems to work well on the smaller engines I run. -Al

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RE: Throttle connections - 3/2/2012 4:59 PM   
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quote:

ORIGINAL: acdii

I had posted a thread a while back, but can't seem to locate it.  I have the DLE20 mounted and all hooked up, but wonder if I will have a problem. Picture tells it all.   Another thing, the thottle is wide open at 3/4 stick on my Futaba 8 FGAS, and I dont have a clue on how to adjust it so the stick is at full when the actual throttle is. I have the link on the innermost hole on the servo.

    I see in your photo's you have your Ingnition Sensor wire tightly Zipped tied to the motor mount  (NOT GOOD) The fine copper strands will fray due to the vibration and  suddenly your engine will die at the worst possable moment , been there done that, found out the hard way a few years ago. Most are using strips of Vecro to secure the sensor wiring loosly, also on the plug lead i have inclosed a photo not the best but you'll get the Idea.

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RE: Throttle connections - 3/2/2012 6:01 PM   
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Al, you may be onto something with the displacement differences. The origin of engine may have something to do with it too. The engines that I have owned have been DA, 3W and D&B, 50cc being the smallest. I currently have a DLE 55 mounted in another Laser build but it is still a few weeks from covering. Maybe I will run into the same thing when I fire that one up. Sounds like you have a handle on the smaller gassers but there are a couple things I would check into if I had the hang up issue before going to a rich needle setting on the low end. You are correct that the smaller engines will retain heat more then the larger ones. This would lead me to running a higher oil content then what I would run on a 100-150cc engine. After 2 gallons at 40-1 Penzoil I switch to 50-1 and stay there the life of the engine. I have tried a number of synthetics at the recomended ratios and always seem to go back to the Penzoil. Not that I think it is better then anything else. I just feel the synthetics at their super low ratios don't work well for heat dissipation. The other thing that I learned from a go cart race team is that they run 24-1 for two reasons. One is they claim more power, the other is that I have been told that the Walbro's have been calibrated for the higher viscosity fuel. Made sense to me as I do see a difference in throttle transition when using more oil.

The other thing I would look at with an engine that hangs up on the low end is timing. I would check to see where it is and make sure it is no more advanced then 28 degrees.

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RE: Throttle connections - 3/2/2012 6:48 PM   
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Re: oil mixture, yes, on top of that. Everyone suggests running 32:1, so that's what I'm running. Not going into oil brand/type discussion, but at that ratio we're running plenty through them.

I learned about using fuel for the "cool down" on snowmobiles. Exact same issue, only they're 30 times bigger. They'll hang the same way after being run hard, then pulling up to a stop sign. Not wanting to settle down right away or until you blip the throttle or hit the choke for a second. Then they act like nothing ever happened, but will repeat that process over and over again for the entire day's ride. Or, you can set them up fat on the idle, killing that wierdness. We run Iridium plugs to help handle that fat idle mixture too, but not wanting to start a war here regarding running them in the model engines. Just tossing that out as a side note.

Re: Timing, DLE 20 and 30 both have a big "step" in the timing curves, right about where you don't want them. Not going into that either, as that has been well thrashed previously. I will say though, that with correct linkage geometry and carb adjusted rich as we've been discussing, the effects of that big timing step have been minimized/eliminated. The Syssa does not have that big timing step (probably about the same curve as the DLE 55?)- yet responds well to both the geometry and rich low speed carb adjustments - for whatever reason. Don't care about the reason really, it's running as advertised. Great engine. -Al

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RE: Throttle connections - 3/2/2012 7:52 PM   
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quote:

ORIGINAL: jerrysu29


quote:

ORIGINAL: acdii

I had posted a thread a while back, but can't seem to locate it.  I have the DLE20 mounted and all hooked up, but wonder if I will have a problem. Picture tells it all.   Another thing, the thottle is wide open at 3/4 stick on my Futaba 8 FGAS, and I dont have a clue on how to adjust it so the stick is at full when the actual throttle is. I have the link on the innermost hole on the servo.

    I see in your photo's you have your Ingnition Sensor wire tightly Zipped tied to the motor mount  (NOT GOOD) The fine copper strands will fray due to the vibration and  suddenly your engine will die at the worst possable moment , been there done that, found out the hard way a few years ago. Most are using strips of Vecro to secure the sensor wiring loosly, also on the plug lead i have inclosed a photo not the best but you'll get the Idea.


Thanks for the tip, I didnt consider the zip tie rubbing the wires, but you have a good point. I have plenty of velcro strips for this exact reason too. The module is well packed in foam inside the plane so it should be nice and snug. 



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RE: Throttle connections - 3/2/2012 9:16 PM   
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I don't know about the DLE ignition module, but some other brands will get hot and stop working if wrapped in foam. No matter what the brand I make a tray and velcro it down and back it up with a single velcro strap. Usually someplace where it will see some airflow.

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RE: Throttle connections - 3/3/2012 4:14 PM   
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Zip ties will work OK when they are wrapped around the tubing twice and then latched. This keeps the force mostly equal around the tubing like a hose clamp. I also solder a piece of brass tubing on the end to make a homemade barb then put the zip tie behind that. A carb arm extension equal to or longer than the servo arm will reduce the sensitivity of the throttle response. I make my own arm extensions. Do everything you can mechanically before messing with the radio adjustments. I use the 50% method then set the end points where the servo stops humming. I use Viton inside the tank.

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RE: Throttle connections - 8/30/2012 7:53 AM   
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quote:

ORIGINAL: ahicks

It sounds like you've already figured out it's a geometry issue. This should help:

The sticky at the top of the gas section (http://www.rcuniverse.com/forum/m_8673009/tm.htm) go to that and scroll down to the diagrams near the bottom of post #21.





The diagrams are at the end of Post #22, not post #21. Took me a while to find them.



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RE: Throttle connections - 8/30/2012 3:26 PM   
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My apologies sir. That's the second time I've done that....
That happenned so long ago I'm not able to edit the post to correct it.

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RE: Throttle connections - 9/28/2012 7:56 PM   
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adjust the ATV

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RE: Throttle connections - 9/29/2012 12:34 AM   
Ernie Misner



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>>> First set your tx throttle trim right down as far as it will go and make sure your throttle stick is at full throttle off rest position.

Make sure you have extended the length of the carb arm as far as you can, use the extension provided by your engine manufacturer, or make one or buy a after market one , does not matter how you do it as long as it gets done.

Fit the throttle servo arm on the throttle servo so it points directly at the extended carb arm hole/connection point when the carb is at full closed position with idle screw removed.

Now connect your linkage arm to this exact length making sure you do not move the carb from its stop or the servo arm from its pointing directly at the carb arm hole/connection position.

Set your throttle trim to mid point now, start your engine and admire your perfect throttle set up. >>>
-

I want to get this but am getting lost in the translation here somehow.
Set throttle trim all the way down and throttle stick at full throttle. Okay.
The arm on the carbs tend to come from the factory too short, so extend the length.... as far as you can? You mean to match the length of a long arm on your servo?
Fit the throttle servo arm on the throttle servo so it points directly at the extended carb arm hole/connection point when the carb is at full closed position with idle screw removed.....? Do you mean so it is parallel to the carb arm, or? You loose me when saying point it directly at the carb arm hole somehow.
Now connect your linkage arm to this exact length making sure you do not move the carb from its stop or the servo arm from its pointing directly at the carb arm hole/connection position. Okay, I think you mean to make up the pushrod to this exact length without moving anything.

Sorry for the confusion, thanks,

Ernie

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RE: Throttle connections - 9/29/2012 1:26 AM   
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The DLE 20's are shipped with a fiberglass looking kind of carb arm that should be installed. If you don't have it you can probably make something that will work out of an unused servo arm? The length of this arm is generally a little shorter than the servo arm, but not much. It's not that critical.

The big point being made is that the servo arm is installed so it's pointing nearly straight at the carb arm when looking at it from above?

Have you checked out the diagram showing this setup? It's post #22 here: http://www.rcuniverse.com/forum/m_8673009/tm.htm

With the throttle arm closed (idle speed adjustment screw removed!), throttle stick all the way down, the servo arm is installed and connected so it's pointed nearly straight at the hole in the carb arm you're planning on using.

In actuality, you probably want to allow for some adjustment here if you plan on being able to shut the engine down with a throttle shut off position on your transmitter. If that's the case, install the arm so it looks more like the diagram showing 20 degrees servo travel and you'll be close enough.

Not the easiest thing to describe, so if you are still not following, holler and I'll have another go at it. -Al

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RE: Throttle connections - 9/29/2012 2:50 AM   
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Thanks again, will go back to post #22.

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RE: Throttle connections - 11/1/2012 11:17 AM   
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I agree with getting all the wrench and screw driver stuff done first then go to the TX for fine tuning.

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RE: Throttle connections - 11/1/2012 5:56 PM   
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I get it now, thanks. Good point about the servo throttle arm NOT being parallel to the carb arm like usual. Normally on glow, you'd want the carb arm to move proportionally right in sync with the servo arm. Gas is different though because having a butterfly type carb instead of barrel, the main throttle response is in the first part of the butterfly opening. The last part does not do much. So by setting the servo arm pointing at the carb (at idle) as the servo arm starts to move, the carb arm moves SLOWLY at first. In reality that gives you a proportional power curve.

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RE: Throttle connections - 11/2/2012 3:24 AM   
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That's it! You have it now....

That should leave you close enough where the rest can be done with the radio.

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(in reply to Ernie Misner)
       Post #: 50

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All Forums >> Glow Engines, Gas Engines, Fuel &amp; Mfg Support Forums >> Gas Engines >> RE: Throttle connections
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