cox1989

Hi all,

I purchased my first DLE 20RA gas motor recently for my Hangar9 Sbach 342 build but noticed something rather unusual:

My motor did not come with the expected throttle control arm that I've seen in all other pics of both the side exhaust and now rear exhaust version of the DLE 20. Mine did come (in a separate bag) with a longer metal throttle arm extension that has two set screws for tightening. Before assuming that mine is missing the stock throttle arm (the smaller one that fits snugly on the slotted axle), I wanted to post a pic and ask you all to see what you think.

Could this be an updated version which only includes the longer throttle arm? If I do go with that longer one I'd need to first align it properly, then use a dremel to flatten the axle so the set screws bite properly and don't slide. What do you think?

Thanks!
cox1989

pilotpete2

My 20RA did come with the stock Walbro installed, but it's pretty much useless for RC use, so off it came.
No need to make flat spots on the throttle shaft, it's brass, and the set screws will bite the shaft just fine. It would also be a good idea to use some blue Locktite on the set screws.
Unfortunately they leave you on your own as far as the choke lever goes. You'll want to considerations an accessory arm for the choke as well. I used a nosewheel steering arm I had laying around, but a gas engine dealer like Valley View will have them. You'll have to grind off the stock arm to upgrade the choke arm, but that's what happens when the carbs we use on our gassers are mass produced in the millions for the power equipment market.
Best of luck with the Sbach!
Pete

speedracerntrixie

My Feedback: (29)

Pete is correct here, the stock Walbro arm is just way too short for our use. The longer arm that is supplied is a step in the right direction but IMO still too short. For setting up the throttle linkage on a gasser I like to use all of the servo travel. In most cases I set the travel volume to 125% and use a 5/8" to 3/4" servo arm and adjust the length of the throttle arm until I get the carb to go from fully closed with trim all the way down to about 85% open at full stick. The reason for the long carb arm and the short servo arm is to give you the highest amount of resolution and it will help make the throttle curve feel more linear. Then when out at the field use your throttle curve to adjust your cruise speed at half stick. Generally this will have you at approx 60% of available power at half stick. Then use the throttle curve to smooth out the points above and below the half point. Pictured is the throttle curve for my 40% Extra and you can see how it is a smooth arc. It tapers off from 1/2 throttle to full throttle due to the Walbro carb design that has little power increase from 3/4 to full opening. That is why the curve is there and I suggest only opening the carb to 85%. There is no power loss at 85% open but it makes the throttle response above half stick feel much more linear. The idea is to feel and hear a power increase with each notch of the throttle stick all the way to full stick.

As a side note, if that is your install pictured, you will want to cut a 1" to 1.5" dia. hole in the firewall directly behind the carb.

Good luck, I hope this will help you out some.

cox1989

Thanks for the quick replies Pete and Speedracer!

Pete,

I'll definitely go with your advice on the throttle arm set screws and blue loctite. I agree on the choke. There was a H9 Sbach build thread over on RCGroups with a DLE 20 that had a good little trick with the choke rod going through a large plastic servo horn. The horn was then attached to the motor mount, near the front. I didn't attach the link here since I wasn't sure if it's against forum policy (I'm a first time poster, long time reader). You're absolutely right about the carb issue (clone, walbro) these little motors have but I'd venture a guess that it's also the reason the prices are kept so low...

Speedracer,

Thank you very much for the details on both the throttle arm lengths and curve setup on the Tx. Your post confirms what I recall reading somewhere mentioning that, in general, these walbro type carbs on the DLE motors are different and going beyond something like 60% does not net the same increase in power like you'd see in a glow motor's carb (i.e. a linear power curve all the way to 100% open throttle). I'll carefully test this, as you suggest, to see if I can get the best resolution with a longer arm on the throttle and a small one on the servo. Your pic will help me immensely.

For the longer throttle arm, do you mean something like these? www.rcgroups.com/forums/showthread.php?t=1880750 I measured the longer one that came with mine (that I pictured in my post) and it's 3/4" spot-on.

I have a follow-up question: Would a metal 2-56 rod with a plastic ball joint on either end still be ok to use for my throttle rod? Or, should I go and get myself a Sullivan gold-n-rod all plastic type of push rod tube setup for this? I just want to be sure there is no chance of electrical feedback from the motor or ignition.

I've also attached a pic showing the firewall hole diameter behind my carb. In my previous pic, it was fully obscured. Is that diameter enough in your opinion? I'll also dremel out more space for the choke arm, crankcase bolts (You can see they almost touch the firewall) and muffler before I fuel proof the area...

Thanks again,
Frank, a.k.a Cox1989

speedracerntrixie

My Feedback: (29)

Frank, those arms will work just fine. As for pushrod a 2-56 rod with ball links will work just fine. As you mentioned the other threads, some will have you beleive that by half stick you are all in power wise and just have to live with it. I do not buy into this philosophy and you can get it sorted out to have throttle response throughout the full stick travel if you want to put in the additional work. IMO it does make the airplane easier to fly. Then again it all depends on what your expectations for the airplane are. If you just want to throw it about the sky then just about any throttle curve will work but if you are looking for more of a precision setup then go the extra mile, not only with throttle setup but the airplane as a complete package.

ahicks

My Feedback: (2)

Frank, just an FYI, it's not just the DLE engines that are pretty much "all in" at about 60% throttle opening. It all of them. It's pretty typical for anything using a butterfly type carb. Point being, there's a lot of info out there regarding what is called a differential linkage (vs. a linear). that does what we need to do from the mechanical side of the equation. Many will start out with a good mechanical setup, then trim as/if required with their throttle curve. If you're doing anything in the way of precision flying, or you value the ability to add just a few rpm deep in your flare out just prior to touching down, this setup is pretty much required. In the diagram you can see the servo arm has much more travel than the throttle arm early on. Also, from a practical standpoint, you can see that the first illustration in the diagram may not leave you much in the way of good control over your idle speed setting. A better setup would be to start with the throttle arm about where you see it in the second part of the illustration.

Second pic is a typical throttle and choke setup, shown w/throttle closed and open choke. Other end of choke rod arranged to be accessible from one of the cooling air inlets. Simple effective setup used in a lot of planes.

speedracerntrixie

My Feedback: (29)

Over the years Ahicks and I have agreed to disagree on this topic. We have different flying styles and setups, mine being aimed at competition ( IMAC ) flying. At the end of the day what matters is that you are happy with your setup and it meets your expectations regardless of the approach taken.

Truckracer

My Feedback: (19)

Just a side note regarding throttle settings. Many people believe that half stick should be half the available engine RPM or half power / thrust which is not the case at all and experienced flyers quickly learn this. Half RPM will be a power setting quite a bit less than half thrust as that is just the way propellers work. As suggested above and whether using a throttle curve in the radio, linkage differential or a combination of the above, it is important to set up the throttle so it has the feel you want in the air. One person's preference may not be that of another, etc. but do take the time to optimize the throttle feel for personal taste. Personal taste will also change with experience.

I've flown way too many planes set up by other people where the throttle felt more like a toggle switch than a proportional throttle. It can be very uncomfortable and even dangerous to fly a plane like this.

speedracerntrixie

My Feedback: (29)

I could not not agree here more. This is exactly why I reccomend the longest throttle arm possible and the shortest servo arm possible. This greatly increases resolution and gives the throttle a much larger window of operation.

The issue I have with the Jodi diagram is that while or solves having the power come on too quickly at the bottom, ( which IMO has more to do with poor airplane trim then anything else ) it has the power full on at half stick. You end up trading one issue for another. Granted some guys are perfectly happy with that setup, I just know I would not.

Truckracer

My Feedback: (19)

The Jodi diagram is extreme! I usually use a bit of differential in my throttle linkages (old school as that's the only way we could do it in the past) but not to the extent shown in the diagram. It does get the point across though so it serves a purpose. I would be nice if someone could come up with a new diagram that showed less extreme differential.

ahicks

My Feedback: (2)

More background for anyone interested - SRT, though sometimes slow to admit, is generally flying MUCH bigger stuff than I fly, and as an IMAC type, the emphasis for his "sweet spot" is around half throttle, where the majority of his maneuvering is done.

I fly the smaller stuff (20-30cc) and am more about sport and 3D flying. My emphasis is more about low and mid range control - which responds well to the diagram shown pretty much as is.

The bigger point here, is that a linear linkage (like you might set up for your flying surfaces) will NOT give the throttle response most are looking for. That's the on/off switch setup Truckracer is talking about. We ALL agree, as will anyone else that's flown anything like that, is that it's no fun to fly like that. Especially after having flown something that works as it should.

"The issue I have with the Jodi diagram is that while or solves having the power come on too quickly at the bottom,
(which IMO has more to do with poor airplane trim then anything else ) it has the power full on at half stick."

IMHO, for the many that are unfamiliar, that have been able to use this diagram to get an idea of what a linkage like this might look like (including Jedijody and the guy that took the trouble to illustrate this originally), it gives a fair representation of something that will work, or at the very least, get you into the ball park. With minor tweaking (including the note about idle mentioned above), this linkage will result in noticeable, mostly linear engine response from the top to bottom of the transmitter stick travel (similar to a glow engine). A LOT of people have been using it for quite a while. The thing about being all in at half stick is not true at all.... -Al

Last thought: note that this diagram was never intended as a schematic, to be followed to the degree, guaranteeing a perfect setup. Further, the take away point, might be to start your setup with the carb closed, and your servo arm pointed nearly straight at the end of the carb arm. That will generally get you pretty close....

Truckracer

My Feedback: (19)

I've been flying a DLE 20 powered Velox quite a bit this season. Being a smaller gasser than I'm use to, the throttle requirements are completely different than what has become normal for me. The engine / airplane combination requires the throttle be more open to produce the necessary thrust for the relatively large airframe. I had to adjust my curves quite a bit to create a comfortable feel and to get the stick where I wanted it for the necessary power while maintaining a comfortable stick feel. Darn nice plane I might add.

speedracerntrixie

My Feedback: (29)

The last thing I care to do here is to start another argument I would like to correct a statement here. Flying IMAC well requires use of the entire throttle range. Looking at the sequence that I flew this year you can see a few maneuvers that requires the airplane to come over the top and into a vertical or 45 degree down line. This requires a gradual decrease from a high power setting down to idle. One MUST have linear throttle response throughout the entire range. The key to this is to increase resolution. If your throttle arm moves 5 degrees for every click of throttle and it seems too sensitive then the fix would be to lengthen the carb arm and/or shorten the servo arm so that you get 2-3 degrees for each click. Think of it like expo that works on the whole range not just center. If anyone doubts this I would suggest you download the IMAC sportsman sequence and start flying it. You would soon discover a handful of issues with your airplanes setup as a whole including the throttle response. There need not be a difference between IMAC and 3D setup on throttle curve as the TOC and now TAS have pilots flying both styles.

ahicks

My Feedback: (2)

Shawn, regarding the center throttle comment, I didn't say you were flying only on the center of your travel. I'm not either! I was simply repeating something you told me a while back in one of our other conversations. At the time (years ago now!), I was struggling to understand how your emphasis could be SO different from my own, and others I fly with.

Regarding your IMAC routine, from this desk, there's as much interest on how you might accomplish that as I would imagine you would have regarding a rolling Harrier. Can we try and go/stay with more generic info? As mentioned, that diagram is not intended as a blueprint. It's illustrating differential - extreme differential as Truckracer pointed out, and I agree. Please, let's not getting into splitting hairs here?

Point taken regarding arm length. The ratio of one to the other is important. I am able to get away with both about the same length (3/4" or so). Final adjustments are then handled with throttle curve. Understand though, that's me. If you have specifics regarding what you're using, tell us. Not really interested in whether you think what I'm using won't work.

Regarding how much travel you get per click, if that's an issue, just disable the clicker! -Al

Edit: I should have mentioned end point adjustments. Final settings established through throttle curve and end point adjustments.

Truckracer

My Feedback: (19)

I've preferred smooth friction only over a clicker / ratchet on throttles for years. It probably comes from flying helis and it stuck with me. Looking at some of my old, old transmitters, I couldn't imagine how course those clickers were. In some cases, just one click could make the difference between landing and taking off with a fairly high climb rate .... they were that course.

I really like the newer transmitters where you can introduce both friction and / or a bit of click in the amounts you prefer.

cox1989

Gentlemen, thanks again for all the advice! I'll carefully examine all of your tips and will try a hybrid approach using the second position on Jody's image above + throttle curve adjustment.

Frank, a.k.a Cox1989