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Throttle Springs Again

Steve, this may be dumb question category, but I need clarification on your comment:

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.

Does this mean you can move throttle w/o unlocking? Or do you have to precede the move with release of the lock?
Dick Seiders
 
Mine is number 336 and I have no problems so far. I just tighten it to the point that is stays put and at that setting I can still make minor or major adjustments. This is hands down, the best flight video I have seen. Even though I live on the opposite side of the country, that is my favorite part of this grand country that we call home. Thanks for making it. It really is the coolest video I have ever seen!
 
Yes

Dick,

Yes, I can move the throttle without unlocking it. With the friction as tight as I can get it, at leaset with my fingers - not using pliers here - I can still move the throttle without excessive drag. So I don't change the friction setting (ever) and don't really have a creep problem (at least not throttle creep):D.
 
Mine as I have mentioned before has no creep, and I too just set the friction and fly, without any inflight friction adjustments. If I unscrew the lock ring the knob is slowly pulled in by the carb springs.

Last time I was in the plane I unscrewed the throttle control's lock ring to see what was actually causing the friction and saw two leather washers in there, one conical shaped, and one flat.

Although mine is not any issue for me, I am curious why others are not the same. My throttle is a Mcfarlane and says not to oil. Are all of them Mcfarlane? Has any one called Mcfarlane and asked about this? Anyone with problems oiled theirs? It would be neat if two planes could get together and compare hardware - One that creeps, and one that doesn't.
 
I have seen - -

3 other planes that were newer, and they did have a different throttle. I flew one of them recently, and did not do other than I usually do, unlock before adjusting. It was different than mine, but it did not slip, so not sure. I have not asked that owner how he adjust his throttle, and may try to next time I talk to him.

John Bender
 
Steve, thanks for the clarification. This thread gets more interesting by the hour. Next flight I will see if I can operate the throttle w/o releasing the lock. If it works I guess we can call that pilot controlled creep?
Dick Seiders
 
Throttle Spring Orders

All of the throttle spring orders are being shipped out today, via USPS.
There is one exception, I still do not have an address for Mark Henderson.

Don't forget to modify your new springs according to Joe Gores posts.
Care should be taken to prevent stresses with tight kinks and tool marks.

Again, my email address: [email protected]

Good luck guys, Tom

Mission Accomplished!
 
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McFarlane Aviation

FYI

I contacted McFarlane Aviation, which supplies the throttle control and this was their reply:

" The throttle springs that come from Rotax are two strong of a pull to be used with a friction lock control. They are more suited to a non locking throttle control. I will send you two new throttle springs to install. This should take care of the throttle creeping problem you are having. I will also send you a throttle control friction lock service kit. Just in case you are still having trouble after you install the new springs. "

Gary
 
McFarlane's Memo

Now you tell us. :)
Seriously, let us know what you get, what the part number is, and how they compare to the ones that I just sent out.

Tom
 
KRAUSEGB said:
FYI

I contacted McFarlane Aviation, which supplies the throttle control and this was their reply:

" The throttle springs that come from Rotax are two strong of a pull to be used with a friction lock control. They are more suited to a non locking throttle control. I will send you two new throttle springs to install. This should take care of the throttle creeping problem you are having. I will also send you a throttle control friction lock service kit. Just in case you are still having trouble after you install the new springs. "

Gary
Click to expand...

It would be a good idea to let Vans know.
 
Its logical when I think about it

Who should be the engineer to guarantee the safe operation of the throttle mechanism, in good times and bad? Rotax? Vans? the throttle manufacturer?
Gary, thanks for doing that. It will be good to get this sorted for all those RV-12s with crook throttles. And to have an engineer behind the necessary mods.
Rod
 
Those trouble some springs!

Really if there is a issue with the throttle on the 12 then if enough people report it to Vans then they should come up with a fix for every one.:confused:
 
Yay! A real fix!

Just called McFarlane. Talked to Starr. She is on top of the situation and told me their engineers have been working with Van's folks on this issue. I ordered two replacement springs for about 8 bucks apiece. Starr said they will be shipped out on Monday.

Since I never got around to installing the springs I got from Joe, I will hold those in reserve and try out these semi-official replacements and report back.

Apparently there has been action going on in the background that we did not know about. Thank you Gary for contacting McFarlane and getting the word out on this. It could be a while before we get this through "official" channels.
 
Throttle springs

Although I could personally live with the creepy springs, my wife cannot. she is very slight and when the throttle lock is tight enough to defeat the creep, she does not have enough strength in her wrist to unscrew the throttle lock. Consequently she has to fly with her hand always on the loose throttle to prevent creep. Hard to put the flaps down that way.
 
New springs are here!

I just opened yesterday's mail and I now have a set of the new springs, Part No. 6536, from McFarlane. They also sent along a big thick catalog of all their aviation goodies that might come in handy in the future.

As soon as we get a decent day here I will install and test fly. WX here today is 20's and snowing.
 
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Spring strength?

John, I think it would be interesting to know how strong these new springs are compared with the originals and the ones Joe has ordered.

"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." Joe Gores
 
Measuring spring strength

An easy way to compare the strength of two springs is to hook them together and pull. The weakest spring will expand first. Another way is to use a fish scale to measure the strength of each spring.
Joe Gores
 
Mcfarland Part Number

I tried the 6536 part number for the Mcfarland spring. Not successful. Can anyone verify the part number
 
Joe, how much elongation did you use to measure the force in your springs? Someone else would need to know this detail, I suspect.
 
Spring elongation

Joe, how much elongation did you use to measure the force in your springs? Someone else would need to know this detail, I suspect.
Click to expand...
Sorry that I can not remember. Might have been 3/4". One could measure the length of the original spring at idle and again at full throttle and subtract to get the difference.
Joe Gores
 
you guys have me scratching my head...

What is the problem?

If the spring is the problem, go fix the spring.

If throttle creep is the problem, go fix the throttle creep.

Don't change the spring to fix the throttle problem,
and don't change the throttle to fix the spring problem.

If spring is the problem.. go ask Rotax to fix the spring. Have you contacted Rotax?
Why are you taking upon yourself to do the patch work.

Do you know the mathematics of springs? (Hooke's law, wiki and youtube is a good place to start)
How could you know the spring you selected/manufactured has the required combination of rigidity and elasticity to meet the job?
or do you think a spring is a spring and that any "slightly" weaker spring will solve your problem?
What kind of engineering test are you going to do before flying?
eg. would the spring work in -20c? (some would say the temp would never go that low inside the cowl)



If you are going to change the spring (which I won't),
you should do at least the following:

1. measure the carburetor lever travel.
2. measure the force needed to enable such lever travel (under various environmental conditions)
(eg. when the cab is iced up)
3. measure the current spring travel (length vs extension)
4. measure the current spring strength (constant, deflection, ...there is a whole science to this)
5. determine if the spring is overpowered? If so, by how much.
6. design a spring that can deliver the travel and strength for the task.
(there are gauges that you can use to make a scientific decision)
7. make sure the spring you manufactured can meet your new specification in terms of MTBF, travel, strength, repeatable performance, etc.,


Whatever you do, good luck.




ps. when I ask "Have you contacted Rotax?", I was not implying that you have not tried. It was just a question. Sorry if I sound as if I was implying you have not explored all your avenues.
 
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Very well said and from my very limited knowledge on the subject correct, but then there is this nasty little "Catch 22" we are required to first build the RV-12 just the way Van's tells us to and we do, to get it certified as an ELSA (yes some go EAB and can do as they like) and when we get a Rotax engine with springs on the carburetors that requires that the friction lock on the throttle assembly be hard locked, provided by Van's, to keep the throttle from moving on its own, we do think that this is an unsafe condition that needs to be fixed. Rotax can not be contacted by anyone from America so it would be hard to get any information or help from them and there well meaning distributors can not help for fear of upsetting Rotax. Van's thinks the RV-12 is perfect and has not been interested in providing a fix for any of the problems that have been filling these threads. Just one small example, people have been complaining about trying to use large heavy duty spade connectors on number 22 wire for the trim motor and the auto pilot since the first few kits and several years later and past kit number 550 they are changing to a reasonable connector with pins that work better on number 22 wire, I will not waste our time with more examples.

So we either find some one with the skill to fix the problem or we hack at it our selves, which is what is happening here. It would be great if you or someone with the engineering skill would solve this problem or perhaps it could be solved by a vernier throttle set if that ever got past the drawing board from the vendor who was talking about it at Oshkosh last year. In any case it is a real problem that needs a real solution, wish us luck until the safe solution is found.

Best regards,
Vern

RVnoob said:
you guys have me scratching my head...

What is the problem?

If the spring is the problem, go fix the spring.

If throttle creep is the problem, go fix the throttle creep.

Don't change the spring to fix the throttle problem,
and don't change the throttle to fix the spring problem.

If spring is the problem.. go ask Rotax to fix the spring. Have you contacted Rotax?
Why are you taking upon yourself to do the patch work.

Do you know the mathematics of springs? (Hooke's law, wiki and youtube is a good place to start)
How could you know the spring you selected/manufactured has the required combination of rigidity and elasticity to meet the job?
or do you think a spring is a spring and that any "slightly" weaker spring will solve your problem?
What kind of engineering test are you going to do before flying?
eg. would the spring work in -20c? (some would say the temp would never go that low inside the cowl)



If you are going to change the spring (which I won't),
you should do at least the following:

1. measure the carburetor lever travel.
2. measure the force needed to enable such lever travel (under various environmental conditions)
(eg. when the cab is iced up)
3. measure the current spring travel (length vs extension)
4. measure the current spring strength (constant, deflection, ...there is a whole science to this)
5. determine if the spring is overpowered? If so, by how much.
6. design a spring that can deliver the travel and strength for the task.
(there are gauges that you can use to make a scientific decision)
7. make sure the spring you manufactured can meet your new specification in terms of MTBF, travel, strength, repeatable performance, etc.,


Whatever you do, good luck.
Click to expand...
 
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Vern,has anyone tried Rotax owners forum ? Fairly good opportunity to get wider Rotax owner feed back there maybe. Just a thought.
Dick seiders
 
Hi Dick,

No I have not and that is a good idea. As I am one of the lucky few waiting for Skyview I have not been working this problem, I was hoping that someone would have a good solution.

Best regards,
Vern


dick seiders said:
Vern,has anyone tried Rotax owners forum ? Fairly good opportunity to get wider Rotax owner feed back there maybe. Just a thought.
Dick seiders
Click to expand...
 
Update on the new spring from McFarlane

I installed and test flew the new springs this afternoon. Before I swapped springs I measured the amount of pull required to move the throttle out, using my highly calibrated fish scale. ;) Approximately 6 pounds of pull required. Then I swapped out the springs and re-measured: between 3 and 4 pounds.

Then taxied and flew. Big difference. I can now actually set the friction free enough to allow power changes without backing off the friction every time and retightening it. Still takes a bit of finesse to find exactly the right setting. On final at idle the power did not creep back on as it had before.

The new springs definitely have enough strength to achieve the desired fail-safe operation. They appear to be of good quality, although the wire is visibly a smaller gauge.

I took side-by-side pictures for comparison , but of course left the camera in the hangar.
 
Rotax Form!

I have posted on the new Rotax form a few times. All it is is a form hosted by Rotax. You get no expert advise from Rotax! There is a moderator but he is only there in case someone breaks the rules. I wish there was a Rotax Tech rep available but no luck. You get more info right here at this from which is a lot better.:)
 
Steve, as I stated earlier that I planned to try your method today I had the opportunity and so tried the throttle lock/still able to move w/o unlocking today, and essentially I find I can do as you stated in an earlier post. I was very pleasantly surprised. I had to learn how tightly to set the lock or the push pull force is pretty stiff. Once I found the tightness setting I could change throttle settings w/o loosening the lock. The key is tight enough to move the handle in/out, while also tight enough to avoid creep. This is an acquired skill, but not difficult. I will continue the drill till I have the skill! Given what I experienced today I see no problem with the existing setup, and no reason to change the springs. I realize this is a matter of individual preference so I am not saying those changing springs are wrong, but I would hope most would try the method you use as it's always a treat to find the designed system works effectively without modification. This assuming of course that most RV12's have the same or similar setup.
Dick Seiders
 
Who Should We Follow?

Dick, I understand your position, but when the throttle cable manufacturer, In this carse, McFarlane, makes the statement that the original Rotax spring are too strong for their throttle setup, I think we need to look at changing them, very closely.
 
Maybe I missed it but - -

Does anyone know why they went to the second design. Again, my 'early' design throttle works great. Locks VERY firmly. ? ? ? ? ? :confused:

John Bender
344.0 hours
 
BigJohn said:
I installed and test flew the new springs this afternoon. Before I swapped springs I measured the amount of pull required to move the throttle out, using my highly calibrated fish scale. ;) Approximately 6 pounds of pull required. Then I swapped out the springs and re-measured: between 3 and 4 pounds.

Then taxied and flew. Big difference. I can now actually set the friction free enough to allow power changes without backing off the friction every time and retightening it. Still takes a bit of finesse to find exactly the right setting. On final at idle the power did not creep back on as it had before.

The new springs definitely have enough strength to achieve the desired fail-safe operation. They appear to be of good quality, although the wire is visibly a smaller gauge.

I took side-by-side pictures for comparison , but of course left the camera in the hangar.
Click to expand...

Thanks for posting your mod.

removing ~50% of the spring force is a lot (my 2c only, YMMV).

one more measurement people can take:

after removing the old spring and before installing your new spring,
pull your throttle to idle, tighten the throttle as much as you can,
then take a measurement from the engine side to see how much force is required to move it.
(ie. how much force is needed to create the throttle creep).
It would be interesting to see different airplanes' measurements.

Thanks again for your report. I hope we can all learn from it and make a better (safer) airplane out of this discussion.
 
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RV12Photos


Here is a picture comparing the original Rotax spring with the replacement from McFarlane. At least I think you might be able to see it if you follow the link. I just spent a couple frustrating hours trying to make it show up in this post. I don't know why that has to be so hard to do, at least for me.
 
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Having flown with the stock springs for 35 hours, removing 50% of the tension is not a negative. I have 2 choices. Live with creep, or crank it down to where throttle movements are a chore. I have been amused with all the comments about "if the cable breaks, you will crash" Yeah, maybe.

The cable is a very simple mechanical contrivance. It is a knob, a cable, and a sleeve. Using my standard vision, I can inspect it with ease. If it is rusted, or frayed, I have a problem. Are the nuts tight? If all of the above are negative, what is the big problem? I've driven for 43 years. I've never had a cable break. Half of this time was with old MG's. Everything breaks on MG's, except the cables. I don't know anyone who has had a throttle problem, be it in a car or a plane.

Engine problems, that is another story. I am much more concerned with the engine failing. It has lots of moving parts. I can't see most of them. It needs electricity, fuel, air, timing,and pressure. These are a lot harder to monitor. On a relative scale the risk of a cable failing compared to the engine is abouut .000001. With good maintenance the risk os the engine failing is small. The odds of a maintained cable failing is zilch. Hey, it takes about 1-2 lbs to move the throttle. 1/16 cable has a breaking strength of 480 lbs, give or take. I'm guessing 2 lbs of tension would work fine on our systems.

Relax on the whole subject of springs. What is average of tension on a Piper of Cessna. A whole lot less than 16 lbs.

Just my 2 cents.
 
Here's the picture...

John,
Yes, there is some sort of weird protection on the picture, you must have right-click copy protection enabled on your albums. I took a screen shot, used Paint to edit and saved as a jpeg. To post, I use a pay-for web photo sharing service that lets me easily control the use of my pictures.

BTW, I really enjoyed your web pictures of the Alaska trip in the 195, fabulous.

i-SvNqTG4-M.jpg


Tony
 
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Careful with the comparisons

Mark Henderson said:
Relax on the whole subject of springs. What is average of tension on a Piper of Cessna. A whole lot less than 16 lbs.
Click to expand...

Everyone will have their own take on this and what they are willing to do in terms of changing the stock system. However, it is not possible to compare the throttle system of a Cessna with that of the Rotax. Cessnas use a solid cable that is equally capable of both pushing and pulling the throttle arm on the carb. Absolutely different from the very small, twisted strand cables employed with the Rotax in the RV-12 which have very little capacity to push the throttle arm without buckling. And the Rotax has 2 carbs that like to be perfectly in sync- break a cable or lose a connection on one side and you have a very rough time ahead unless you can somehow get them back in harmony. Now this is not saying a set of springs that generate less tension could not do the job. I have just yet to see someone with engineering knowledge around the Rotax weigh-in (and recognize we may never see that).

Would I like to have a solid, more robust cable system like a Cessna so that the springs could be totally eliminated? Absolutely! However, that would necessitate a completely different throttle cable design.

Jeff
 
jte65 said:
.....Now this is not saying a set of springs that generate less tension could not do the job. I have just yet to see someone with engineering knowledge around the Rotax weigh-in (and recognize we may never see that).
Jeff
Click to expand...

Jeff,

You make good points all the way around. All I have to go on, as to the engineering of the new springs, is that I was told by McFarlane that their engineers worked with Van's engineers to come up with a more suitable spring. And - they look good to me visually, install solidly, and make the throttle, at least on my airplane, a lot easier to control.

John
 
For me, the throttle set up in the Flight Design CT is perfect. Instead of a push-pull, they use a throttle quadrant. the pilot does not set it in flight, friction is set on the ground. I've only had to adjust mine once in 5 years. It's easy to move and never moves again unless I move it.

Of course this is a completly different set up than the -12 and with my limited skills I have no idea about how, or if, the CT throttle concept could be adapted to the -12.
 
Vans problem

Replacement of these springs is Vans responsibility. Hide as they may behind a wall of official silence, third hand reports of collaboration between Vans and Mcfarlanes is credible. To keep faith with their customers, I think Vans needs to announce a free replacement program. This is a safety issue, despite their deafening silence.
I am trying to fix the problem for my aircraft by getting springs from Tom. But I would rather have the McFarlane springs. And I dont see why I should have to buy them.
Rod
 
BigJohn said:
RV12Photos


Here is a picture comparing the original Rotax spring with the replacement from McFarlane. At least I think you might be able to see it if you follow the link. I just spent a couple frustrating hours trying to make it show up in this post. I don't know why that has to be so hard to do, at least for me.
Click to expand...

John,

Had the same problem with Picasa and spent the same couple of hours! It appears if the link has an https:// prefix, it will NOT be displayed as a photo on VAF. When I tried, Photobucket (link had an http:// prefix), did not have a problem. VAF must not be able to handle the secure link.
 
Throttle quadrant?

As long as we are hoping for a 'fix' for this, I would like to see Van's offer a Piper type throttle quadrant as an option. I suppose that that is unlikely due to the restrictions of LSA but I'd sure like to see it offered.

Another business opportunity for the right person?
 
Enable Picassa downloads...

John,

There are Picassa albums without the secure (https) protocol. You must have downloads enabled. It appears the album owner (as well as visitors) cannot download unless you have enabled this in your download settings. This apparently applies to links to VAF.

See Picassa Help here. Looks easy enough, but I haven't tried it because I have not signed up for Picassa.

Sorry about the thread drift.

Tony
 
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I flew Sweetie for 25 hours. Then swapped to the springs obtained by todenhal. A GREAT improvement! The functionality is the same without the annoyance factor. Recommended!
 
I think I was the second

or third person to buy/install the new McFarlane springs. Functionally. they're about the same as the ones I bought from a forum member; however the bends are much smoother than those I made (less likely to break) and the arms are longer making them easier to install. I'm approaching 50 hours on them. Do I like them? I have a second set so if one does break I won't have to go back to the originals! In the big picture of RV-12 costs, the cost of these springs is miniscule and the airplane is a lot more fun to fly without worrying about sudden power surges. Yes, if the throttle is unlocked, they'll open it wide-- but slowly. not instantaneously.

Wayne 120241/143WM
 
Flying happily with the McFarlane springs....

....... since November 2011. No problems. I would never go back!
 
Best Spring I have Found

Guys, Joe Gores at [email protected] sent me several Century Springs that he had modified from PN 5553 and worked great on two airplanes that I have used them on. The minimum buy on those springs caused him to order a bunch, and I am sure he has some left over at a very good price if anyone is interested.

With the new spring there is no throttle movement with friction off and engine not running. With the vibration from a running engine the throttle slowly opens to full, but with just a little friction it remains in place. What a difference it makes. Jim
 
In my opinion you don’t have to install extremely weak springs to get good throttle control. I disassembled the friction lock on the standard RV-12 throttle to see why the lock is so hard to tighten sufficiently to prevent throttle creep. There is a fiber washer locking element that conforms to the 30 degree taper on the knurled friction knob. The fiber material gets compressed with use and shines up to a glossy finish when rubbing on the throttle shaft. I think the fiber material is a bad choice for this application.

I made a new locking element from Delrin. Nylon or PVC could also be used. See sketch below. This new element locks and holds the throttle very well to the point where it acts very nearly the same as throttles on Lycoming and Continental engines.

I use a full length coil extension spring - see carb pic below.

24357k0.png
ur2oj.png
 
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