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-   -   Throttle Springs Again (https://vansairforce.net/community/showthread.php?t=79102)

JBPILOT 11-21-2011 07:17 PM

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

Andy J 11-21-2011 07:18 PM

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.

rgmwa 11-21-2011 08:38 PM

Replacement springs
 
Quote:

Originally Posted by Andy J (Post 598340)
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.

Mich48041 11-21-2011 08:55 PM

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:
Quote:

. . . wrestle with the stiff, spring-assisted throttle to keep the idle speed in the desired range."
And on page 14 it says, "
Quote:

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

MartySantic 11-21-2011 09:11 PM

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!

Ausflyer 11-22-2011 12:05 AM

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

MartySantic 11-22-2011 06:32 AM

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.

BigJohn 11-22-2011 07:03 AM

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.

Mich48041 11-22-2011 07:09 AM

Here is a quote (with name deleted) from an email that I just received.
Quote:

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.
Quote:

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

Walt Shipley 11-22-2011 07:14 AM

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


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