gas throttle set up question
11-17-2014, 05:20 AM
#51
There are some quite strong opinions on this subject. I personally extend the carb throttle are to a minimum of 1.25" then run as short of a servo arm as I can with the TX ATV settings almost maxed out with a throttle opening of 90%. ( That last 10% does nothing ). Then I set up the linkage and servo arm position so that everything is as symmetrical as I can get it. Any fine tuning is done with the TX throttle curve based on what is observed in flight. I have won many IMAC competitions using this set up. Myself I see no advantage to Jodi's diagram other to soften the throttle response at just above idle. I believe this has been done to actually compensate for poorly set up airplanes. Although it leads to the throttle being all in by the time you get to little more then half stick. Imagine an airplane with the CG slightly off, the engine thrust line slightly off and wing incidence slightly off. What's going to happen is that on landing approach when the pilot gets a little excited and bumps the throttle the airplane is going to become unsettled. Having the power come on very softly will act as a Band-Aid for that scenario. Kudos actually for Jodi as he appeared to be smart enough to know that the diagram would make most guys happy and be far less work then trying to describe to guys that their airplane is just out of trim and then try to explain how to trim different airplanes so they react less to airspeed changes. Obviously this is just one man's opinion based on the experience of close to 100 IMAC contests under his belt. I'm sure others will explain why they do what works for them. Weigh the options and do what makes most sense to you.
11-17-2014, 06:28 AM
#52
Personally, I don't really care if 50% throttle is exactly 50% power. I just use a setup with my linkage that allows max throw to be used in the radio for good resolution. Then I add in some exponential to slow the opening and avoid a hesitation or stall if the throttle is opened quickly. Most engines have to be set too rich at idle to get good throttle response. Slowing down the throttle opening helps with that problem. If you go too far however, it will slow down throttle response enough to bother 3D pilots.
I've used Jodi's diagram on a couple of setups just for fun, but I found it made the throttle too soft and imprecise at idle and low throttle.
AV8TOR
I've used Jodi's diagram on a couple of setups just for fun, but I found it made the throttle too soft and imprecise at idle and low throttle.
AV8TOR
11-17-2014, 06:32 AM
#53
My Feedback: (2)
Having perfectly linear linkage is not going to help one iota if the problem you're trying to resolve is about the actual throttle response! Linear linkage does not assure linear throttle response. That's a fact! Period! No Way!
A perfectly linear linkage will not have any more power available at 3/4 or full stick than it does at 1/2 stick. THAT'S THE ISSUE WE"RE TRYING TO FIX!!! What most of us are trying to do is spread that first half of the THROTTLE arm's travel across the entire STICK (servo) travel (and I get where a contest flier might be wanting to do something slightly different).
This throttle thing doesn't have anything to do with a poorly set up plane.... though I can see SRT's point regarding a plane set up improperly.
What we're trying to accomplish through whatever means (I really don't care how you do it), is having 1/4 of the engine's available power at 1/4 stick, 1/2 power at half stick, 3/4 power at 3/4 stick, and full power at full stick. This diagram is about how you might get very close to what we're trying to accomplish mechanically.... using mechanical differential. For those that don't have a throttle curve available on their radio, this is for you!
Some may be able to look at that diagram and see what it is we're trying to do. The throttle arm is very sensitive regarding the amount of power available, through the first few degrees of it's travel. Those that have leaf blowers might be experiencing the same thing - a hair trigger? Trying to maintain something like 1/4 power is pretty difficult? Same issue...
This is all based on the fact that the butterfly type carb design that we're stuck with is complete garbage when it comes to this. If you were to carefully observe the throttle arm's position, noting available rpms at different openings as it opens, you would see very little gain in rpms over about 60% of it's travel. 70%, 80% and more will net you very little more than 60% while looking at a tach. This is why LINEAR linkage setups will produce very little extra power (rpm) past half (60%) stick on the transmitter.
The take away point here, is that using a linear linkage like you would use on a control surface, is going to set you up for a super sensitive throttle right off the idle, and nothing extra available over 50 or 60 percent stick travel. If/when you get tired of dealing with that, you'll need to do something like we're talking about here, or setting something similar up using a throttle curve. We're taking that first 60% of the CARB arm travel, and spreading it out over 100% of the transmitter STICK travel. Hard to get your head wrapped around this if you've never considered it before, but once you have it, pretty easy, and you'll never fly without it again.
Last thought, trivia, though JediJodi was/is a big proponent of this, he didn't do the diagram. A fellow that goes by JoeAirport (or something close to that) on another forum did it, and has no issue with those that want to share it. FYI
A perfectly linear linkage will not have any more power available at 3/4 or full stick than it does at 1/2 stick. THAT'S THE ISSUE WE"RE TRYING TO FIX!!! What most of us are trying to do is spread that first half of the THROTTLE arm's travel across the entire STICK (servo) travel (and I get where a contest flier might be wanting to do something slightly different).
This throttle thing doesn't have anything to do with a poorly set up plane.... though I can see SRT's point regarding a plane set up improperly.
What we're trying to accomplish through whatever means (I really don't care how you do it), is having 1/4 of the engine's available power at 1/4 stick, 1/2 power at half stick, 3/4 power at 3/4 stick, and full power at full stick. This diagram is about how you might get very close to what we're trying to accomplish mechanically.... using mechanical differential. For those that don't have a throttle curve available on their radio, this is for you!
Some may be able to look at that diagram and see what it is we're trying to do. The throttle arm is very sensitive regarding the amount of power available, through the first few degrees of it's travel. Those that have leaf blowers might be experiencing the same thing - a hair trigger? Trying to maintain something like 1/4 power is pretty difficult? Same issue...
This is all based on the fact that the butterfly type carb design that we're stuck with is complete garbage when it comes to this. If you were to carefully observe the throttle arm's position, noting available rpms at different openings as it opens, you would see very little gain in rpms over about 60% of it's travel. 70%, 80% and more will net you very little more than 60% while looking at a tach. This is why LINEAR linkage setups will produce very little extra power (rpm) past half (60%) stick on the transmitter.
The take away point here, is that using a linear linkage like you would use on a control surface, is going to set you up for a super sensitive throttle right off the idle, and nothing extra available over 50 or 60 percent stick travel. If/when you get tired of dealing with that, you'll need to do something like we're talking about here, or setting something similar up using a throttle curve. We're taking that first 60% of the CARB arm travel, and spreading it out over 100% of the transmitter STICK travel. Hard to get your head wrapped around this if you've never considered it before, but once you have it, pretty easy, and you'll never fly without it again.
Last thought, trivia, though JediJodi was/is a big proponent of this, he didn't do the diagram. A fellow that goes by JoeAirport (or something close to that) on another forum did it, and has no issue with those that want to share it. FYI
Last edited by ahicks; 11-17-2014 at 06:56 AM.
11-17-2014, 09:14 AM
#54
My Feedback: (19)
I only have a few of points to add to this old discussion. First, the diagram that illustrates differential for throttle is an extreme example at best. It can be softened a bit and still accomplish what one wants to accomplish .... in a mechanical only manner. Second, throw away the tach when trying to get a fairly linear throttle. Engine RPM does not relate exactly to thrust! So half speed in RPM is not exactly half thrust or half power. As an example, adding 500 RPM at the top end of the throttle changes thrust a lot more than adding 500 RPM at the low end just above idle. Fly the plane and adjust throttle linkages accordingly rather than trying to do it with a tach. Third, mechanical differential can work extremely well and can create a very linear throttle feel but I no longer use that with our modern radios. Using a good throttle curve in the transmitter coupled with a quality, precise throttle servo accomplishes the same task with far less work.
I disagree with some statements that there is no increase in power at the upper end of the carb throttle movement. In many cases when carbs are a bit oversized, indeed the increase is very small but there is still a change even though slight. When carb sizes are closer matched to engine size the throttle response is more linear. Every kind of carburetor or fuel injection, from our engines on through automotive applications have similar non-linear characteristics when a simple butterfly throttle valve is incorporated.
I disagree with some statements that there is no increase in power at the upper end of the carb throttle movement. In many cases when carbs are a bit oversized, indeed the increase is very small but there is still a change even though slight. When carb sizes are closer matched to engine size the throttle response is more linear. Every kind of carburetor or fuel injection, from our engines on through automotive applications have similar non-linear characteristics when a simple butterfly throttle valve is incorporated.
11-17-2014, 10:04 AM
#55
My Feedback: (2)
Regarding the diagram, it's the concept that's important. Whether you're going to accomplish what it's illustrating electronically, mechanically, or a combination of both is your call. As already mentioned, half stick doesn't need to be exactly half throttle, and the other points don't need to match either. If it feel right, fly it!
It's easy to pick apart that diagram once you get your head wrapped around what it's illustrating. If you look at the very low end, you can see that adjusting your idle, or idle shut off, is very difficult or maybe impossible? Starting the servo arm a few degrees away from pointing directly at the carb arm would help allow for that.
So much of this is so subjective, up to pilot's preferences. The important part, for those new to this, is the fact you can do something about that sensitive throttle (especially right off the idle, possibly making it difficult to flare using just a few hundred rpm, if you are used to doing that), as well as having some/more throttle control/response above half stick.
And yes, I think the perfect setup would have the throttle plate wide open at full stick as well, but not going to enter a debate about how much of a power increase there is available between 60 and 100% throttle opening.
It's easy to pick apart that diagram once you get your head wrapped around what it's illustrating. If you look at the very low end, you can see that adjusting your idle, or idle shut off, is very difficult or maybe impossible? Starting the servo arm a few degrees away from pointing directly at the carb arm would help allow for that.
So much of this is so subjective, up to pilot's preferences. The important part, for those new to this, is the fact you can do something about that sensitive throttle (especially right off the idle, possibly making it difficult to flare using just a few hundred rpm, if you are used to doing that), as well as having some/more throttle control/response above half stick.
And yes, I think the perfect setup would have the throttle plate wide open at full stick as well, but not going to enter a debate about how much of a power increase there is available between 60 and 100% throttle opening.
11-17-2014, 10:41 AM
#56
My Feedback: (19)
Regarding the diagram, it's the concept that's important. Whether you're going to accomplish what it's illustrating electronically, mechanically, or a combination of both is your call. As already mentioned, half stick doesn't need to be exactly half throttle, and the other points don't need to match either. If it feel right, fly it!
It's easy to pick apart that diagram once you get your head wrapped around what it's illustrating. If you look at the very low end, you can see that adjusting your idle, or idle shut off, is very difficult or maybe impossible? Starting the servo arm a few degrees away from pointing directly at the carb arm would help allow for that.
So much of this is so subjective, up to pilot's preferences. The important part, for those new to this, is the fact you can do something about that sensitive throttle (especially right off the idle, possibly making it difficult to flare using just a few hundred rpm, if you are used to doing that), as well as having some/more throttle control/response above half stick.
And yes, I think the perfect setup would have the throttle plate wide open at full stick as well, but not going to enter a debate about how much of a power increase there is available between 60 and 100% throttle opening.
It's easy to pick apart that diagram once you get your head wrapped around what it's illustrating. If you look at the very low end, you can see that adjusting your idle, or idle shut off, is very difficult or maybe impossible? Starting the servo arm a few degrees away from pointing directly at the carb arm would help allow for that.
So much of this is so subjective, up to pilot's preferences. The important part, for those new to this, is the fact you can do something about that sensitive throttle (especially right off the idle, possibly making it difficult to flare using just a few hundred rpm, if you are used to doing that), as well as having some/more throttle control/response above half stick.
And yes, I think the perfect setup would have the throttle plate wide open at full stick as well, but not going to enter a debate about how much of a power increase there is available between 60 and 100% throttle opening.
11-17-2014, 03:00 PM
#57
I agree that there is some personal preference involved here. Even at the upper classes of pattern and IMAC I have flown other guy's airplanes and have not been overwhelmed by their overall setups. In most cases we learn how to do things a certain way, get accustomed to the way it feels and never find a reason to change. I once was loaned a 100cc Extra 260 to compete with for a single contest. I picked up the airplane a week before hand and few every evening prior to the contest. I was given the OK to make any necessary adjustments which I did. The result was a third place finish in Unlimited. I returned the airplane with my " improvements " intact. A few weeks later I saw the owner of the airplane ( basic class competitor ) flying the airplane and it appeared he was fighting the airplane through his sequence. When talking to him about the way the airplane was handling he had admitted that he changed everything back because he didn't like the way the airplane was flying. He made this call after a single flight. Now at the time I was a bit put off as I was thinking about how happy he was going to be with an airplane that was set up " Correctly ". He had grown accustomed to the way the airplane flew before I got my hands on it so the new setup felt awkward to him. I tend to classify this throttle curve deal into this same category.
11-17-2014, 09:38 PM
#60
Having perfectly linear linkage is not going to help one iota if the problem you're trying to resolve is about the actual throttle response! Linear linkage does not assure linear throttle response. That's a fact! Period! No Way!
A perfectly linear linkage will not have any more power available at 3/4 or full stick than it does at 1/2 stick. THAT'S THE ISSUE WE"RE TRYING TO FIX!!! What most of us are trying to do is spread that first half of the THROTTLE arm's travel across the entire STICK (servo) travel (and I get where a contest flier might be wanting to do something slightly different).
This throttle thing doesn't have anything to do with a poorly set up plane.... though I can see SRT's point regarding a plane set up improperly.
What we're trying to accomplish through whatever means (I really don't care how you do it), is having 1/4 of the engine's available power at 1/4 stick, 1/2 power at half stick, 3/4 power at 3/4 stick, and full power at full stick. This diagram is about how you might get very close to what we're trying to accomplish mechanically.... using mechanical differential. For those that don't have a throttle curve available on their radio, this is for you!
Some may be able to look at that diagram and see what it is we're trying to do. The throttle arm is very sensitive regarding the amount of power available, through the first few degrees of it's travel. Those that have leaf blowers might be experiencing the same thing - a hair trigger? Trying to maintain something like 1/4 power is pretty difficult? Same issue...
This is all based on the fact that the butterfly type carb design that we're stuck with is complete garbage when it comes to this. If you were to carefully observe the throttle arm's position, noting available rpms at different openings as it opens, you would see very little gain in rpms over about 60% of it's travel. 70%, 80% and more will net you very little more than 60% while looking at a tach. This is why LINEAR linkage setups will produce very little extra power (rpm) past half (60%) stick on the transmitter.
The take away point here, is that using a linear linkage like you would use on a control surface, is going to set you up for a super sensitive throttle right off the idle, and nothing extra available over 50 or 60 percent stick travel. If/when you get tired of dealing with that, you'll need to do something like we're talking about here, or setting something similar up using a throttle curve. We're taking that first 60% of the CARB arm travel, and spreading it out over 100% of the transmitter STICK travel. Hard to get your head wrapped around this if you've never considered it before, but once you have it, pretty easy, and you'll never fly without it again.
Last thought, trivia, though JediJodi was/is a big proponent of this, he didn't do the diagram. A fellow that goes by JoeAirport (or something close to that) on another forum did it, and has no issue with those that want to share it. FYI
A perfectly linear linkage will not have any more power available at 3/4 or full stick than it does at 1/2 stick. THAT'S THE ISSUE WE"RE TRYING TO FIX!!! What most of us are trying to do is spread that first half of the THROTTLE arm's travel across the entire STICK (servo) travel (and I get where a contest flier might be wanting to do something slightly different).
This throttle thing doesn't have anything to do with a poorly set up plane.... though I can see SRT's point regarding a plane set up improperly.
What we're trying to accomplish through whatever means (I really don't care how you do it), is having 1/4 of the engine's available power at 1/4 stick, 1/2 power at half stick, 3/4 power at 3/4 stick, and full power at full stick. This diagram is about how you might get very close to what we're trying to accomplish mechanically.... using mechanical differential. For those that don't have a throttle curve available on their radio, this is for you!
Some may be able to look at that diagram and see what it is we're trying to do. The throttle arm is very sensitive regarding the amount of power available, through the first few degrees of it's travel. Those that have leaf blowers might be experiencing the same thing - a hair trigger? Trying to maintain something like 1/4 power is pretty difficult? Same issue...
This is all based on the fact that the butterfly type carb design that we're stuck with is complete garbage when it comes to this. If you were to carefully observe the throttle arm's position, noting available rpms at different openings as it opens, you would see very little gain in rpms over about 60% of it's travel. 70%, 80% and more will net you very little more than 60% while looking at a tach. This is why LINEAR linkage setups will produce very little extra power (rpm) past half (60%) stick on the transmitter.
The take away point here, is that using a linear linkage like you would use on a control surface, is going to set you up for a super sensitive throttle right off the idle, and nothing extra available over 50 or 60 percent stick travel. If/when you get tired of dealing with that, you'll need to do something like we're talking about here, or setting something similar up using a throttle curve. We're taking that first 60% of the CARB arm travel, and spreading it out over 100% of the transmitter STICK travel. Hard to get your head wrapped around this if you've never considered it before, but once you have it, pretty easy, and you'll never fly without it again.
Last thought, trivia, though JediJodi was/is a big proponent of this, he didn't do the diagram. A fellow that goes by JoeAirport (or something close to that) on another forum did it, and has no issue with those that want to share it. FYI
The top 1/2 of the carb travel does make a difference, just not as much as the bottom 1/2 does. That's what all the modern radio benefits are for.
One thing I disagree with is the linear linkage does not give linear throttle statement. It is the case for most engines, but the YS 185, CAN be set up with linear throttle linkage that gives linear throttle response.
11-18-2014, 04:57 AM
#61
Yep, I agree with pretty much everything you said. Having a so called "perfect linkage set up"', is neither here nor there. It's mostly a waste of time, as with the radios these days, you have expo, throttle curves and mixes that all can be utilised to get the exact throttle response you want.
The top 1/2 of the carb travel does make a difference, just not as much as the bottom 1/2 does. That's what all the modern radio benefits are for.
One thing I disagree with is the linear linkage does not give linear throttle statement. It is the case for most engines, but the YS 185, CAN be set up with linear throttle linkage that gives linear throttle response.
The top 1/2 of the carb travel does make a difference, just not as much as the bottom 1/2 does. That's what all the modern radio benefits are for.
One thing I disagree with is the linear linkage does not give linear throttle statement. It is the case for most engines, but the YS 185, CAN be set up with linear throttle linkage that gives linear throttle response.
Works for me.
11-18-2014, 05:25 AM
#62
Yes being able to throw a curve in there is very helpful and allows fine tuning but IMO the more important thing is to lengthen the throttle arms on the carb. I personally go just about as long as I can get away with. Then I max out my throttle ATV and use the shortest servo arm I can get away with that yields 90% of carb opening. What this does is add to the systems resolution and makes the servo position very precise. The mechanical differential also tends to slightly slow the throttle arm movement. The result is a throttle that is not jumpy right off idle, a rock steady idle and a power change for each ratchet of the throttle stick. The attached video is a bit long ( Sorry guys ) but about 2/3 in is my 150cc Extra. Not a great example of throttle control as I was attempting to do more of a performance then boring contest flying but it does illustrate the nice idle and transition during take off and landing. Small field but feel free to tease me about having to make a second landing attempt. LOL...................www.youtube.com/watch?v=2mekGZo3pqQ
Last edited by speedracerntrixie; 11-18-2014 at 05:34 AM.
11-18-2014, 05:42 AM
#63
My Feedback: (2)
Yep, I agree with pretty much everything you said. Having a so called "perfect linkage set up"', is neither here nor there. It's mostly a waste of time, as with the radios these days, you have expo, throttle curves and mixes that all can be utilised to get the exact throttle response you want.
The top 1/2 of the carb travel does make a difference, just not as much as the bottom 1/2 does. That's what all the modern radio benefits are for.
One thing I disagree with is the linear linkage does not give linear throttle statement. It is the case for most engines, but the YS 185, CAN be set up with linear throttle linkage that gives linear throttle response.
The top 1/2 of the carb travel does make a difference, just not as much as the bottom 1/2 does. That's what all the modern radio benefits are for.
One thing I disagree with is the linear linkage does not give linear throttle statement. It is the case for most engines, but the YS 185, CAN be set up with linear throttle linkage that gives linear throttle response.
11-18-2014, 05:53 AM
#64
My Feedback: (27)
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Not knowing much about engines except how to start them, I've often wondered why the manufacturers can't come up with their own carb instead of everyone using the walbro. I figured it was just easier.
11-18-2014, 06:39 AM
#65
On the bold, not being familiar with the YS, I have to wonder if it's using a pumped butterfly type carb? If it's using a barrel type carb (as in a typical glow engine), those are dramatically more "linear" than a butterfly type. If we had those available for gas, linear throttles wouldn't be an issue.
11-18-2014, 06:46 AM
#66
Cost, cost and cost. Walbro's are cheap, especially if you are buying thousands at a time. Back in '06 while having a conversation with Dave Johnson he told be DA was shipping an average of 85 engines per week. That's a ton of Walbro carbs. Now throw in the mix of Chinese made engines and Walbro clones. A good number of guys have enough issues justifying the price difference between a DA and DLE let alone a DA or 3W with an in house carb that raises the engine cost yet another 75.00 to 100.00. If i'm not mistaken both DA and 3W have fuel injection that their Mil Spec engines are delivered with.
11-18-2014, 12:03 PM
#68
Yes... if it works for you. What didn't work for me was throttle control when landing and trying to maintain just the right amount of power for various winds. The throttle resolution just wasn't there and hence this whole discussion about how to increase the resolution at low settings.
11-18-2014, 05:16 PM
#71
The yellow arrow is the fuel pump and works between a 2 piece inlet push rod. The red arrow is the fuel pressure regulator.
This is the DZ175cdi.
11-18-2014, 08:02 PM
#72
Ok thanks for the info, I have had only 2 YS 4 strokes, a 91 AC and currently a 115 WS. Both of those are pressurized system. I did see Chip Hyde fly one of his F3A models not too long ago and I assume it was the 185 in the nose and it was very impressive. The transition was like silk and it had power to spare.
11-18-2014, 08:23 PM
#73
Ok thanks for the info, I have had only 2 YS 4 strokes, a 91 AC and currently a 115 WS. Both of those are pressurized system. I did see Chip Hyde fly one of his F3A models not too long ago and I assume it was the 185 in the nose and it was very impressive. The transition was like silk and it had power to spare.
I just received the DZ70cdi today.
11-19-2014, 05:16 AM
#74
Nice, I have to pick up a 70 myself this year. I have an old Rivets F1 kit that I'm going to power with a 70. It's almost a shame but I use the 115 for pylon. That little beast will spin a 14X13 at close to 10K on 30% nitro. Tried a tank of 55% in the last race and threw a prop blade. No damage to the engine but although I landed the airplane on the runway, the airframe was torn up too badly to repair. I just can't enough good about YS. Tatsu Yamada even fly's in from Japan once a year to race with us. He is quite the pilot.
11-19-2014, 01:07 PM
#75
Nice, I have to pick up a 70 myself this year. I have an old Rivets F1 kit that I'm going to power with a 70. It's almost a shame but I use the 115 for pylon. That little beast will spin a 14X13 at close to 10K on 30% nitro. Tried a tank of 55% in the last race and threw a prop blade. No damage to the engine but although I landed the airplane on the runway, the airframe was torn up too badly to repair. I just can't enough good about YS. Tatsu Yamada even fly's in from Japan once a year to race with us. He is quite the pilot.
