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Throttle Springs Again
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/communit...7&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, Quote:
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 ![]() |
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 |
Me too..
Tom,
I'm in Australia too, and would take a set if you decide to order. |
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 |
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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
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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 |
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 |
Tom - I want a set please. billhollifield at iname dot com
Bill Hollifield |
I'll 'spring' for a set!
Tom - PM'd you.
Thanks for putting this together! |
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'?
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springs
Tom,
I sent you an email. Hal-san |
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.
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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
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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:
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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.
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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.
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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 Quote:
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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...
http://www.ch701.com/webmaster/Jon/d.../jon_crash.htm |
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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/-I...0/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: engineering@vansaircraft.com 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) engineering@vansaircraft.com |
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