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Throttle Springs Again

todehnal

Well Known Member
I've not seen any posts from users of weaker throttle springs since March. By now, there should be some experienced users who would be comfortable in commenting on them. Another item of interest would be to let us know where you purchased your springs? Was there a minimum order requirement and the approximate cost? I'm not flying yet, but I have a friend who is and is dissatisfied with the current heavy throttle springs.
Thanks, Tom
 
Here is a link to my original post about weaker throttle springs:
http://www.vansairforce.com/community/showpost.php?p=492537&postcount=51
Century Spring had a minimum order of $40 when I ordered mine. I do not have any more left after selling the extra ones to other builders. I have an account with Century Spring and could order another batch to share with others. Or you can order some and sell the extra. They cost about $5 per pair. I think that I sold a pair for $8 or $10 to cover my cost and shipping and hassle. I have about 30 hours on my springs with no problems. I still have to tighten the throttle knurled knob quite a bit to hold the throttle , but I can still move the throttle without having to loosen the knob. Here is a message that Denny from AZ sent me,
"I installed the reduced-force throttle springs on my RV-12 several weeks ago and they work great. No more throttle creep. Thanks for this wonderful mod."
I was thinking about replacing the flap handle spring with a weaker one. If anyone has that spring handy, I need to know the parameters: free length, wire diameter, coil diameter, number of coils, installed compressed length with button pressed, and force required to press button. That force can be measured by setting the spring on a bathroom scale and compressing it the same distance as if it were in the flap handle with the button pressed.
Joe Gores
 
Watching for feedback

Thanks Joe, I wouldn't mind ordering a batch, if I thought there was enough interest to recoup my costs. I sure don't need 8 sets of them. We'll see how much activity this thread gets, and we'll go from there. No sense in everybody ordering a batch, that's for sure.
Tom
 
I forgot to mention that the Century Spring part number 6049 is too long and needs to be shortened. I could not find an exact replacement with the required characteristics, but the 6049 was the closest. Music wire doesn't need any heat treatment.
The picture below is from Century Spring's catalog.
Joe Gores
Spring%252520Loop%252520Forming.png
 
Tom
If you get a run of them I would like 2 sets (ie for 2 engines). I am in Australia and would pay for the extra postage.
John
 
Ordering a Batch of Springs

Monday, I will go ahead and order a batch of springs.

I will try to save the forum names of those who have responded with interest.
Although, I have never done it, I'm sure that I can figure out how to send packages to Australia. Can't be rocket science. Hay, If I can build an airplane.........
Tom
 
Although, I have never done it, I'm sure that I can figure out how to send packages to Australia. Can't be rocket science. Hay, If I can build an airplane.........
Tom

Nothing fancy. A padded envelope via UPS will do just fine.
 
Nothing fancy. A padded envelope via UPS will do just fine.
Tom
I hope he means USPS - much cheaper than UPS.
USPS is a remarkable service.
As rgmwa said, an envelope with some padding will be fine.
It's not like it's the other side of the world! - just kidding.
John
PS Thanks in advance for doing it.
 
USPS

Tom
I hope he means USPS - much cheaper than UPS.
USPS is a remarkable service.
As rgmwa said, an envelope with some padding will be fine.
It's not like it's the other side of the world! - just kidding.
John
PS Thanks in advance for doing it.

Arrr.. yes I do. USPS not UPS. Big difference. Thanks John.
 
Throttle knob friction

Here is another aussie complaining about the throttle set-up. I hate the throttle creep too, but dont want to blame the springs necessarily. They are just part of a poorly designed sub-system (sorry Vans) which puts unnesessary stress on the pilot. I reckon its a safety issue.

Are the springs too strong, or is the friction mechanism inadequate? I have tried out a few things eg put a little leather dressing on the dry-as-a-chip leather washer to make it more pliable - no change. Greased the knurled knob thread with nickel antisieze - no difference. The next idea is to cut leather washers from better leather, of greater diameter to improve the friction . Maybe I will try a synthetic material washer. After that I plan to get a knurled knob with larger diameter (x2) from the manufacturer, or make a adaptor that does the same thing.

I dont buy the argument that you need a strong grip and bulging forearm muscles to set the throttle (or hold it on idle on late final). My partner wants to learn to fly this plane, and I doubt if she could fly it safely as it is, with the current throttle design. Not good enough.

Has anyone managed to solve this throttle problem from the cockpit end?

Rod
 
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Lighter is Better

Rod, I think you may be over thinking, and over engineering a fix. Instead of more resistance, use less spring. Van has designed a very smooth and friction free throttle system, as is typical for most RV control systems. Rotax, on the other hand, installed heavy throttle springs, to compensate for throttle systems that are less free. The goal is to have enough tension to safely move the throttle to the full power position, in the event of cable breakage. We don't need these strong springs to accomplish that goal. So.....

Tom
 
The throttle spring is the fault of Rotax, not Van's. If Van's made changes to the engine, they would be liable for any mishaps. Rotax does not know how their engines will be installed. In this litigious society, Rotax has to make sure that the throttle will fail open regardless of the throttle linkage. So they used very strong springs to cover their A $ $.
Increasing the holding power of the friction knob is not a solution. If the friction is great enough to hold those two powerful springs, weak hands or fingers will not be able to move the throttle. I see two possible solutions: use weaker springs, or replace the throttle cable assembly with a different design. For RV-12s that are currently flying, replacing the very strong springs with weaker ones is the easiest fix.
The replacement springs that I used are still strong enough to open the throttle in case the cable breaks, even though the springs are only half as strong as the originals. When I loosen the friction nut completely, the throttle knob is still pulled fully forward. And that is without any vibration, the engine off.
Companies that make springs are willing to make custom springs with any desired characteristics. However, they charge a setup fee. If Van's ordered a large quantity of custom springs, the setup cost per spring would not be much. For individual purchases, it is more economical to purchase stock springs and shorten them to fit.
Joe Gores
 
Has anyone considered leaving the original Rotax springs in place but adding counter balance springs from the same fixed position to the opposite end (aft) of the the throttle arm 'bellcrank'?
 
Springs Vs friction

Tom and Joe, thanks for your comments. Joe, I take your point that even with the friction easier to set, you still have to pull against the friction + spring tension to reduce revs. That is the nub of the problem. Reduce the spring tension and you can operate the throttle with a lower and safer level of friction. Got it. Shame Vans doesn?t see it that way.
Tom, I would like to join the list of builders buying replacement springs from you. I will PM you.
Rod
 
Been flying a lot with the original springs. NO PROBLEM here. Just something you have to get used to. Not hard to pull to the min RPM when landing. Consider this another user preference.
 
Another user preference...

Agree with Marty, no problem here either. The stock springs can be counted on to deliver power when needed.

Exercise care, it is not a push/pull throttle system.

Tony
 
My 2 cents also - -

Recently did BFR in a 172, and found myself not putting the throttle where I needed it. With the 12, just release it, and you take off. 172 didn't want to go ! ! ! ! :D Just takes time to get used to. I don't even think about it now.

John Bender
today - 330.7 hours
 
And another user preference...

I haven't had any trouble with the stock springs and throttle friction adjustment. Even landing I don't notice any creep problems, although my hand is on the throttle as it should be.

Perhaps there are minor difference in throttle/cable friction from plane to plane? I haven't flown but two RV-12s, mine and 412RV.

I would recommend current builders try the stock configuration before making any changes.
 
Replacement springs

I would recommend current builders try the stock configuration before making any changes.

That's what I plan to do, at least until the end of the Rotax warranty period. After that I'll make a decision, however I'd like to have some unofficial `stock' replacement springs on hand in case I decide to change.
 
There is an article in the December 2011 issue of Kitplanes Magazine about the RV-12 that Dave Martin built. Here is a quote from page 10:
. . . wrestle with the stiff, spring-assisted throttle to keep the idle speed in the desired range."
And on page 14 it says, "
I'd noticed on the flight north that Martin had been resetting the throttle often. His RV-12 is fitted with the normal push/pull throttle and screw-down lock, not a vernier-style control. The Rotax's twin Bing carburetors each have strong return springs that are always trying to pull the throttles open; the idea is that a cable break would give full power instead of no power. Unfortunately, the springs are strong enough to overcome the throttle control's friction lock. Every few minutes, you have to nudge the throttle back and reset the lock. What a pain. If the RV-12 were mine, I'd substitute a vernier control . . .
The Author of the article, Marc Cook, must think the throttle nuisance is important enough to mention in a national aviation magazine. Admittedly not everyone has the problem. Either those pilots have a strong grip or their throttles work better, or both. My throttle crept forward even with the friction lock tight. Rather than complain about it, I searched catalogs for a suitable replacement spring. I was as apprehensive as a test pilot on the first few flights with the new springs. Now with 30 hours on the new springs, I have confidence in them. Of course that is not long enough to prove the new springs are fail safe. But so far the springs do their job. If I loosen the friction knob, the new springs pull the throttle full open. They do not need to be strong enough to pull the throttle knob out of my hand.
Joe Gores
 
Maybe something has changed. The position of my throttle does NOT creep one bit once locked. Pulling the throttle out of your hand is an over-statement. FAR from FACT!
 
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too much variation

There must be something going on here. Different RV-12s should not give pilots such different experiences. Perhaps we should be looking for the variable. My money is on the leather washer. In my aircraft it is a very loose fit in the tube, and literally as dry as a woodchip. The cone to compress it hardly marks it.
I suspect the quality of leather used is far harder to control than other materials. Perhaps some of us got dodgy leather washers.
Rod
 
I just learned, thanks to Mike Tea, way back, Van's DID start to send a different throttle cable. The very early kits had a different model and that MAY be the reason for the differences.
 
I'm going to change my springs

I've been lurking, watching this thread with interest, and now I feel inclined to comment. Marty, Tony, and John B. are all friends of mine, and I respect their opinions on everything RV-12. However, my experience has been different than theirs. I have over 50 hours on my '12, and the throttle creep is a constant annoyance. In cruise in order to hold a power setting I have to crank the friction knob down as hard as I can, to the point I am afraid of breaking something. With this much tension the throttle it is impossible to move. On landing approach, I can't keep the engine down to idle unless I do the same, setting up a bad situation if I need power in a hurry.

When Joe got his first batch of replacement springs I had him send me a set, but I did not want to install them until I gave myself sufficient time to get used to the original springs and for the mechanism to "break in". After watching this new thread I have decided to install the weaker springs. I think I have given the originals a fair trial.

My advice to newer builders is to live with the originals for a few hours before changing. Your installation may have different characteristics than mine and be trouble free.

Joe, as always, thanks for your thoughtful analysis of this issue, and for your research in finding a replacement spring that can be adapted to our use.
 
Here is a quote (with name deleted) from an email that I just received.
Joe, One aspect to the springs issue not yet mentioned is this: Were it not for the fact that the 12 uses the full-size RV brakes, I think we would have had some ground accidents. I know that prior to switching to your springs, that throttle popped forward a couple of times on me. The strong brakes saved the day.
Another thing I don't have to deal with is managing descent in the pattern while removing your right hand to drop the flaps. Maybe I had one of those bad friction locks but I had to clamp down so hard some times that when I went to release it, the outer boss rotated with the lock ring, making things very interesting on base leg. There is a limit to which you can tighten the assembly to the panel without compressing the friction mechanism. I had to keep a Crescent wrench in the side pocket for in-flight adjustment.
I understand how Vans cannot change Rotax's setup but I cannot understand how anybody could find the stock setup acceptable long-term. BTW, I keep the original springs in an envelope in my glove box...at least until Warranty runs out.
30+ hours on replacement springs.
Some throttles are creeping forward and some are not. Maybe Mike Tea has the right idea that some RV-12 have a different style of throttle. We are comparing apples to oranges.
Pulling the throttle out of your hand is an over-statement. FAR from FACT!
Sorry Marty, I have been told a million times not to exaggerate! :D
Joe Gores
 
Throttle Springs

Joe, add me to the list of those wanting throttle springs. I think $10 is more than a fair price, considering the hassle you have to go through to handle.

Walt Shipley
 
I agree with BigJohn, and Marty may have a good part of the answer. My first RV-12 had the original throttle set and you had to lock the friction control to stop throttle movement, if you did not have it locked it would move forward when you removed your hand, say to pull on flaps and this made it a little hard to use in the pattern. It made formation flying all but impossible and that has made the aircraft a lot less popular here. I do not know how the second RV-12 will turn out, still waiting for avionics, but I am buying the springs so that after a trial with the newer throttle set we can change the springs if this one is as bad as the last one. This is a good reason to think about the fuel injected modification as it may permit the return to what most of us think of as normal operation of the throttle, where it can be moved at any time and it does not have to be hard locked to keep it from moving on its own.

Best regards,
Vern


I've been lurking, watching this thread with interest, and now I feel inclined to comment. Marty, Tony, and John B. are all friends of mine, and I respect their opinions on everything RV-12. However, my experience has been different than theirs. I have over 50 hours on my '12, and the throttle creep is a constant annoyance. In cruise in order to hold a power setting I have to crank the friction knob down as hard as I can, to the point I am afraid of breaking something. With this much tension the throttle it is impossible to move. On landing approach, I can't keep the engine down to idle unless I do the same, setting up a bad situation if I need power in a hurry.

When Joe got his first batch of replacement springs I had him send me a set, but I did not want to install them until I gave myself sufficient time to get used to the original springs and for the mechanism to "break in". After watching this new thread I have decided to install the weaker springs. I think I have given the originals a fair trial.

My advice to newer builders is to live with the originals for a few hours before changing. Your installation may have different characteristics than mine and be trouble free.

Joe, as always, thanks for your thoughtful analysis of this issue, and for your research in finding a replacement spring that can be adapted to our use.
 
Joe, add me to the list of those wanting throttle springs. I think $10 is more than a fair price, considering the hassle you have to go through to handle.
Walt Shipley
Walt,
I am not buying this batch of springs. Tom Odehnal aka todehnal is. I assume that he will read your request. I have no financial interest in this issue, just trying to help others by sharing my success.
Joe Gores
 
springs

I would like to get on the list for springs. I am having the same problem as others.
Where and how do I get on the list?

Thanks,

Gary Krause
N117GB
 
Safety issue

From the stories that are now coming forward, it is clear to me that throttle creep is a safety issue for many RV-12 pilots. I think Vans needs to investigate this and come up with an engineered fix for aircraft with the fault. I hope they add it to the list.
Rod
 
just in case anyone who is planning on the mod, but has not read this...
Thanks for reminding everyone of the danger. I had read similar warnings that made me apprehensive on the test flights with the weaker springs. The Zenith 701 builder mentioned that strong springs are needed to overcome a binding cable. I had not thought of that, but was only thinking about a cable breaking. Regardless of which throttle springs are used, it would be a good idea to loosen the friction nut during the pre-flight inspection and make sure that the throttle is pulled fully forward. The weaker springs still pull my throttle all of the way with the friction nut loose. The 701 builder did not mention the pulling force of his springs or how he chose them. I spent lots of time reading spring catalogs to find the one that I wanted: 4 pounds of tension compared to 8 pounds for the original springs. The accident airplane had 2 1/2 hours. I have 30 hours on my weaker springs with lots of touch & goes. A couple of other RV-12 builders have even more time on their springs. Of course there could be failures in the future. It is scary deviating from what is known to work. But so far, so good.
For those who still intend to replace the springs with Century Spring part number 6049, here is some advice:
The springs must be shortened. They come with extended hooks on both ends. Since an extended hook is only needed on the top end, the bottom hook can be cut off and a new hook formed. Be careful bending with pliers so as not nick the wire. Doing so will create a weak spot.
The nice thing about springs is that they stretch. It is better to make the spring too short rather than too long. The spring needs to remain in tension even when the throttle is in the fully open position.
The final length measured from inside of hook to inside of hook should be less than 1.75". Shorter is definitely better than longer. The springs have plenty of stretch; it will not hurt to have them on the short side. If you make them too short, it is better to leave it rather than bending back and causing metal fatigue. After bending, you will need to cut off excess wire to make room for installing the spring. Do NOT use heat. The springs do NOT require heat treating after bending. The long end goes up. Proceed with caution.
Joe Gores
 
Look at the picture of the springs in the accident airplane.
http://www.ch601.org/stories/Croke%20Crash/Springs.JPG
Notice how much smaller the replacement spring is in both coil diameter and wire diameter compared to the original spring next to it.
Now look at this picture of the springs that I am using.
https://lh6.googleusercontent.com/-ITSEibj6kEk/TQJMvIybhjI/AAAAAAAAAIE/3_y3lOJi_GI/s640/DSCN4567.JPG
It is hard to tell much difference between my replacement spring and the original on the left, even though it is only about half as strong. It would be interesting to know the properties of the throttle springs in the accident aircraft.
Joe Gores
 
Joe's springs-- I'd like more too

I have about 50 hours on the weaker springs (78 total). I still have to use the friction lock; the weaker springs will pull the throttle open all but the last 1/4 inch or so of cable travel. If you forget and take your hand off the throttle it will still increase the engine RPM but it doesn't SNATCH it all the way forward the way the original springs did. I was concerned about two things-- inadvertant WOT during ground operation and same when trying to bring flaps up for increased braking in short field operations. It's still a concern but much less of one now. Whoever is doing the order list, please put me downh for a "spare pair".
Wayne 12o241 143WM
 
I think if I were having this trouble I would investigate why the throttle friction won't hold, after all this throttle and cable assembly was made for this engine alone and seems to work fine on some of our planes. I haven't heard of different springs coming from Rotax, so I see the throttle as the variable here. Maybe there have been changes in materials, or defects in assembly of these throttle controls?

Has anyone contacted the manufacturer of the throttle cable assembly? I think mine is a Mcfarlane. The stock springs are strong for a good reason, and the throttle control can hold them if it is working correctly. Seems like a lot of folks are working around the real problem.

Just my opinion of course.
 
Throttle Creepy!

This seems to be a case that should be reported to Van Engineering. My serial Number is 120079. I have noticed that my throttle is different than from later models. My friction lock works fine with the original/stock springs that came on the Rotax. If the later version of the throttle does not lock when the friction is applied then this should be reported to Vans. Even though we are talking about it here doesn?t mean they know about it. So everybody who?s friction lock allows the throttle to creep please send a email to Vans asap.
Email: [email protected] Also there is,?already a specific process in place (required by the ASTM for S-LSA certification) for submitting a service difficulty or report a safety issue via Mail, Fax, or E-mail. Look in Chapter 17 of the Maintenance Manual?. As quoted by Scott McDaniels in previous posts. So I?ll go one better, here is a reprint of the page for all to see and use. Sound off on this thread after you send in your report.;)

Rev.1 4/16/10
17-1
CHAPTER 17 - FEEDBACK &
REPLACEMENT PARTS
FEEDBACK

To maintain the highest level of safety the FAA requires and Van?s Aircraft Inc.
requests notification of any safety of flight issue, service or maintenance difficulty that
could compromise airworthiness of the RV-12 aircraft. A feedback form is provided in
the Supplement section of this manual.
A valuable description will include:
?Specific flight condition if applicable.
?List of the parts identified as affected by the anomaly.
?Description of the apparent condition of the parts prior to the anomaly (de-burred,
primed, modified, etc.)
?Statement as to whether the aircraft has remained within the operating limitations
defined in the POH.
?Brief description of the type and frequency of aircraft use (may include; runway
conditions, flying conditions, storage methods, etc.)
REPORTING METHODS
Mail to:
ATTN: RV-12 Safety Alert
Van's Aircraft, Inc.
14401 Keil Road, NE
Aurora, OR 97002 USA
Fax to:
'RV-12 Safety Alert' (on cover page)
503.678.6560
Hours: 24 hours per day
E-mail to:
'RV-12 Safety Alert' (in subject line)
[email protected]
 
Message to Vans engineering re creeping throttle

My report is sent. I looked up the date of the PWR plant packing list for my kit and included that.
Rod
 
Throttle Spring Orders

I need shipping addresses for the following orders:


Only one name left, Come on Mark!! Give it up. :)


Mark Henderson


Thanks. Send to: [email protected]
 
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I checked this thread as I was curious. I will recheck what I am doing with the throttle on next flight, but I don't recall a problem with it. I of course release the lock on takeoff and then lock it in wide open position (likely unecessary to do that part, but it's a throwback to other airplanes throttles). On leveling off I reset to 5400 and lock it again. Don't think I have a creep issue. Only time I get rpm up/dn is when I change pitch. In pattern I lock it at 4000 or so and there is no creep. On approach I hold the throttle with the lock released so I can make any small adjustments required. The spring tension in that case is noticeable, but not a problem. I, like others may have just gotten used to it. I suppose it's possible also that later kits sold had a different spring/throttle set up, but I am number 120093 which is not far down the line from start.
Dick Seiders
 
Another data point

I bought my (standard) engine from a UK Rotax agent, but assume the springs are the same as everyone else's. The throttle assembly came from Vans.

If I tighten the throttle lock as much as I can, the throttle won't creep above 4700 rpm. Anthing below that and the friction cannot overcome the springs.

Cheers...Keith
 
I'll jump in too - -

Since I flew yesterday, I can say the early throttles must be different. I have never had a problem locking the throttle in ANY position. I don't have to lock it hard either. ( original springs ). Must be something with the later versions.

John Bender
332.6 hours
 
Message to Vans engineering re creeping throttle

Our aircraft has the same problem, throttle won't hold using friction lock. Report has been sent to Engineering.
 
While everyone else is watching the pretty scenery in the video of the RV-12 flying around Mt. Baker, I was watching the pilot's hand and the throttle. It seemed like he adjusted the throttle 4 or 5 times. He might have been making adjustments to climb or descend. Or the friction lock might not have been holding. Now I will have to watch that video again to see the pretty mountains that I missed. :D
Joe Gores
 
Adjustment, not creep

I was making power adjustments in the video. At first I was approaching too fast so I wanted to slow down. Then I wanted to go a little upper so I added a little power.

S/N 18 and I only have creep issues (though I've been called a creep on plenty of occasions) at idle. At cruise there're no issues. On a long cross country I set the power and don't touch it until it's time to come down.

I will admit that I do have to hold it out on short final as it will try to increase 100 RPM or so at idle, but for ground handling or anywhere else, I have no problem with it. Yes, I do have the friction lock as tight as it will go, but I find in that configuration, with my cable at least, I get the best of both worlds. It only moves when I want it to, but I can move it without much effort.

This is just the opposite of my 150 which would have the throttle slowly close from full if I didn't keep my hand on it in a climb.

While it is obvious that there are people who have an issue in this area, I am not one of them.

I did at one time entertain the idea of redesigning the whole throttle mechanism using push/pull rods, more like a conventional throttle cable, with a "mixer" at the firewall to control both carburetors exactly the same amount, but decided that I would rather just fly it.
 
Another thought - -

I have never tried to adjust the throttle with it 'locked'. I ALWAYS unlock it to move it even slightly. Not sure if that can change things or not, but that's what I do. On takeoff, I just more or less let it go, and do not lock it until I am ready to level off and set it where I want it.

John Bender
 
Steve,
It is good to hear that your throttle works OK. Since I am the one who suggested weaker throttle springs for those throttles that creep, I take an interest in how the throttle works in other RV-12s. I really enjoyed the beautiful scenery in your video and want to fly out west sometime.
Joe Gores
 
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