Author Topic: 4" Bellcranks, are they necessary in Classics?? (Read 4591 times)

Jim Pollock · « **on:** June 23, 2007, 09:24:15 PM »

Guys,

I have used and others have used 4" Bellcranks in .35 sized airplanes that were originally flown with
3" Bellcranks. I have even made a 3.5" Bellcrank and used it in a Classic airplane. I think that 3.5" is
really as large of a bellcrank that is needed for a 50-56" span classic. I think the more important value
in a bellcrank is that amount of control throw built into it. Example, a slow enough control system can be
built with a 3.5" bellcrank and a 9/16 throw. What do y'all think, anway........

Bill Little · « **Reply #1 on:** June 24, 2007, 12:14:41 AM »

Hi Jim,

For some reason, I like Tom's 3 1/2" bellcranks in the "standard Fox .35 size" Classic plane.

I found it interesting when a couple weeks ago, Kent Tysor flew my "restored" Charles Parrott P-47. A pretty good sized "35 Classic". I built it in '94, flew it in Classic for a year or so with a Fox 35. Not enough engine, so I left it alone until a little over a year ago. When I built it, I used a 3" Sig nylon BC, and some Top Flite horns I had. It is now about 4 oz. lighter, and has a T&L McCoy 40 in it.

Anyway, after Kent flew it, he remarked that he just couldn't fly it himself on a regular basis. The controls were just too fast! I was used to it, so it didn't bother me.............. but everything I have built of a serious nature in the past 10 years has had at least a 3 1/2" BC and "modern horns".

Dennis Adamisin · « **Reply #2 on:** June 24, 2007, 07:35:07 AM »

Jim:
A lot of the classic plans show very short horns, sometimes on inner holes of bellcrank... mechanically they are a disaster! Thus I think one of the best things you can do for most classic designs is to give them a modern control system. For me that includes using the 4" cranks with the 15/16" (outermost) throw to a 15/16" elevator horn, flaps usually slower. If the classic bird did not have room for a 4" crank then..... I guess I would readjust everything so the outputs came out the same.

Dennis Adamisin · « **Reply #3 on:** June 24, 2007, 10:03:37 PM »

Jim P:
Thanks. I believe in the early 1960's you will also find the name of a Mr. Gerry Cipra, who I believe earned the trophy as a JUNIOR. And yes, he WAS that good!

I won Junior in 1969 with my Hawker Typhoon, in 1972 I flew my Fouga Magister in Senior & the Walker Cup. Al was then, and still is the leading proponent of semi scale CLPA, we spent a lot of time chewing over this and that. I still think the Sea Fury was the single most impressive CLPA model ever, but his new Bearcat looks pretty good too!

My tag line just lets me trash talk a little..!

OK back on topic & CASE IN POINT: I am looking over Sheeks Swinger plan and the one thing I MUST change will be the controls. The plans show the Pushrod going from #2 hole in the bellcrank to the middle hole of the flap. Weak mechanically but not unheard of. The killer is that it shows the elevator driven off the innermost hole off the flap, to the middle hole of the elevator; meaning the elevator travel will be 1/2 the flap travel - don't think Jack built his that way, and I for sure will not! I will stuff a 4" bellcrank into it, reversed so front line is up (per Al!), and run a rod from the outer hole of the crank to the outer hole of the elevator. I will then run a second rod from #2 hole in the crank to the outermost hole in the flap. This should result in a 2:3 flap to elevator, and some pretty light bearing loads at all points. However, I will also probably have to put a "hump" on the top of the fuselage to cover the longer horn!

John Miller · « **Reply #4 on:** June 25, 2007, 04:19:59 PM »

Quote from: Tom Niebuhr on June 25, 2007, 01:11:59 PM

There is no doubt that the larger horns and Bellcranks, are much better because they have a better mechanical advantage. just remember that that the actual movement of the surfaces are due to the relative distance between the holes.

The only restricting factor, in some cases, is the available space.

snip

I can't agree more with Tom. In most cases, a little figuring, as far as ratios go, and you can have about anything you want, with either size bellcrank. It's just more "automatic" with a larger BC.

Should be able to get what you want, Dennis, without having to have a bulge to clear the horn.

John Miller

Dennis Adamisin · « **Reply #5 on:** June 25, 2007, 04:46:34 PM »

do I have pix... don't encourage me!

Just teasin Jim, thanks for asking!

Dennis Adamisin · « **Reply #6 on:** June 25, 2007, 05:04:17 PM »

John & Tom:
You are right, I can get the correct ratios, but to do so inside the low Swinger fuselage means using a 1/2" horn on the flaps, with corresponding short output off the bellcrank. However, I get real anal about maximizing the mechanical advantage and reducing bushing loads. Thus I intend to use the 3/4" output from the bellcrank to a 1" flap horn. Unfortunately that is about 1/4" ABOVE the top of the fuselage, thus the "radome" bump, which should look right at home on the jet anyway. You know the Type 13 radar used on the second production batch of the F111b... - HONEST!!!

Dennis Adamisin · « **Reply #7 on:** June 25, 2007, 08:45:44 PM »

BTW, just checked out the plans for Sheeks Ryan SC and Bob Millers "extended Gee Bee" Both show the elevator pushrod set up to give LESS elevator than flap throw. This cannot be right (can it???)

John Miller · « **Reply #8 on:** June 25, 2007, 09:16:07 PM »

Ya know, Dennis, in the old days, we simply used 1 to 1 ratio for the flaps and elevators. Nowadays, with planes with a reasonable wing loading, we've found that we don't need as much flap as we used to use.

I was speaking with Gordan Delaney about this very subject, the other day. He and I both agree that most of our planes have about a 6 or 7 degree difference, at full throw. The degree readouts on my most recent plane is about 24 degrees flaps, and about 32 degrees for the elevator. It's a very good idea to use an adjustable elevator horn. Too much flap can make "swoopy" turns, as I'm sure you already know..

John

Bill Little · « **Reply #9 on:** June 25, 2007, 11:06:19 PM »

I remember hooking up a few planes back inthe day with the flap rod below the elevator rod on the flap hoen. Seemed to work.......... Billy told me he always used more elevator than flap on his old I-beamers.

Dennis Adamisin · « **Reply #10 on:** June 26, 2007, 07:17:59 PM »

Yup. Kinda hard to explain it was a model of a French trainer in Belgian Airshow Team colors. However, one guy called it a Nobler....

Ward Van Duzer · « **Reply #11 on:** July 12, 2007, 09:26:14 AM »

At the '92 Nats I was flying a "scale" Navy Nobler in heavy wind. During the build I was told that a Sig 3 inch BC and a Sig Horn (plastic upright, steel flap arms) was good enough for a 35 powered Nobler. Well, being inexperienced in flying in heavy wind I got caught in a heavy "wind-up" on my inside loops. As heavily as I could lean on my UP line it wasn't enough to keep the airplane in the tight loop, and it figure-nined on the pavement. THE END! Examination showed the plastic upright on the flap horn broke at the push rod hole. But even had that not happened, I am sure that I didn't have enough leverage on the BC to keep that loop from opening up. Probably would have pancaked anyway.

I will NEVER use a control system that "is good enough" again! If a four inch BC has more leverage than a 3, or 3 1/2 incher, guess what I'm going to use? And if it doesn"t fit, Move it! Wild Bill says it doesn't matter where the BC pivot is, The airplane flies off of the leadouts!

Ward

Bill Little · « **Reply #12 on:** July 15, 2007, 07:38:46 PM »

Quote from: Jim Pollock on July 01, 2007, 08:32:20 PM

Bill,

Yes he did look quite exceptional in the Picture. I don't know if he had already won the walker cup or not,
but he looked the part even if he looked a little young. Also, for Dennis, I remember hearing stories about
Gery Cipra and that he could have been as dominate as Mr. Walker, but I guess he found girls and such.
Happens to lots of great flying young folk. My buddy Derek Berry has gone through the girl stage and is now
back flying and getting better. I expect him to win a Nats very soon.

Jim Pollock,, every time I watch Derek fly a pattern these days my eyes look like this........

Little Buddy (Derek) has gone through the marriage stage and is out of that now. These guys are over 30 now! I cannot believe it! Aaron was talking with him Friday night, and I can't believe my son is 31.............. Derek's SON is winning contests now!!!!! Let's see...... his Dad (Derek) is a NATS Jr., Sr., (Adv.??) and Jr. World Champ, his Grandpa (Dale) is a OTS and Adv. Nats Champ....... good "pedigree" I would say.

I was on the phone with Todd Lee today. His son AJ will be going to the field with Dad(Todd) before long. Then he can have two Grandpas with him (Archie Adamisin, Jim Lee) and a Great Grandpa (Big Art) and of course his own "Dad" (Todd), a multiple Nats winner and WC Sr. Team member. These kids will not lack for the "help" they can get if they choose to be CLPA pilots.

My poor old son and grandson are REALLY behind the 8-ball!

Randy Ryan · « **Reply #13 on:** August 10, 2007, 07:07:58 PM »

For my part, I don't think its so much a 4" bellcrank being too big as it is what works for you. I've gone to all 4" bellcranks because I've found is smooths out my maneuvers. It may not for someone else, but slow controls are what the Dr. ordered for me. I really like the fine resolution you get with the longer arms too.

Here are some shots of the control system I built for a GB Nobler I'm working on. I know, overkill, but with this setup I can adjust throws from absolute zero, so I can find out what the optimum differential and flap deflection are.

Jim Oliver · « **Reply #14 on:** August 11, 2007, 03:56:50 PM »

Randy,

I am impressed with the extent of the work you did to achieve full adjustability.

I think it would be great if you would write up the details and results for guys like myself.

Cheers,

Jim

tom hampshire · « **Reply #15 on:** August 13, 2007, 07:27:49 AM »

The above posts are all correct. BUT... It is humbly submitted that the missing part of the analysis so far is the ergonomics, meaning the hand movement necessary to generate a given control deflection. Clearly, a 3 incher will give more angular bellcrank deflection for a given hand movement than a four incher. This excess bellcrank rotation generates two undesirable effects, the first being that over rotation. Once the bellcrank is past 20 or 30 degrees, the effective moment arm of the bellcrank gets noticeably shorter. The shorter the arm, the more force is required, and the less tolerant the whole system is to minor corrections. Which leads to the major difficulty with 3 inchers, the controls are too quick. Think of it in terms of control deflection per length of leadout travel, not per the angular rotation of the bellcrank. Most of us have experience with some plane which had ultra quick controls. Try one again sometime, and see how difficult it is to fly accurately with quick controls. The slower controls make the whole setup easier to fly accurately. So most of the poster so far haven't thought of it in terms of flyability, e.g. the comfort of the pilot.

Bill Little · « **Reply #16 on:** August 19, 2007, 07:54:43 AM »

Quote from: tom hampshire on August 13, 2007, 07:27:49 AM

The above posts are all correct. BUT... It is humbly submitted that the missing part of the analysis so far is the ergonomics, meaning the hand movement necessary to generate a given control deflection. Clearly, a 3 incher will give more angular bellcrank deflection for a given hand movement than a four incher. This excess bellcrank rotation generates two undesirable effects, the first being that over rotation. Once the bellcrank is past 20 or 30 degrees, the effective moment arm of the bellcrank gets noticeably shorter. The shorter the arm, the more force is required, and the less tolerant the whole system is to minor corrections. Which leads to the major difficulty with 3 inchers, the controls are too quick. Think of it in terms of control deflection per length of leadout travel, not per the angular rotation of the bellcrank. Most of us have experience with some plane which had ultra quick controls. Try one again sometime, and see how difficult it is to fly accurately with quick controls. The slower controls make the whole setup easier to fly accurately. So most of the poster so far haven't thought of it in terms of flyability, e.g. the comfort of the pilot.

Hi Brother Tom,

I totally agree that the "old systems" are vastly inferior now that we have become familiar with the "new" systems"!

How many of us learned to fly with a 3" bellcrank, Veco horns, and an E_Z Just or Hot Rock which in relation to "modern systems" gave us HUGE handle spacings, relatively speaking. It is SO MUCH easier, IMHO, to go to the new 4" BC and 1" to 1 1/2" horns than for a young flier to go to the "old set up". A couple weeeks back, Kent Tysor flew mty Parrott P-47 complete with 3"BC, Veco Horns...... He said, "it looks real pretty in the air"! (and that "he" couldn't fly it, too quick!)

Given that, there must be something to the "new" systems, right?

(and don't tell me it's just because I have gotten older! I don't wanna hear that!

)

tom hampshire · « **Reply #17 on:** August 20, 2007, 06:39:22 PM »

Hi Alan & Bill - I don't know why a narrow handle spacing doesn't feel right to me... only that it doesn't. If you want to slow down a set of to fast controls, usually you wind up with a front slider bar handle. Funny thing, I wandered into the team trials about 15 years ago and got drafted by Mr. Tiahrt to be pit boss. I learned that none of the entrants at that level used a handle with a slider bar. All of the handles had the control hardpoints as close to the knuckles as could be. My guess is that the excess overhang (Having the handle arms too far from your knuckles) gives excessive sensitivity around neutral. Other opinions welcome. Tom H.

Dennis Adamisin · « **Reply #18 on:** August 20, 2007, 08:04:34 PM »

I think Lou's comment on long horns and lower pushrod loads really nailed the issue.

Lower bearing loads = long lifed control systems.

Whether you use a 1" or 5" bellcrank, it is POSSIBLE to get the correct ergo relationship between hand movement and control surface movement, but you mght have to take some extreme measures. I just find that with my fixed spacing handle, a 4" crank works pretty darned good - so I will continue to use those cranks and the longest feasible control horns I can.

BTW I use a DIFFERENT (smaller) handle for a bird with a 3" crank and just got another handle ready for a bird wih a 2" crank. Then there's the Goldberg handles for the 1/2A's!

Ward Van Duzer · « **Reply #19 on:** October 09, 2007, 02:41:54 PM »

Uh, the longer the lever, the less torque (muscle) required to move it. (other things being equal)

3 inch BC = manual steering.

4 inch BC = power steering.

among other things!

W.

Ron King · « **Reply #20 on:** October 10, 2007, 05:44:06 AM »

When I built my first Oriental, after returning to the hobby, I calculated the angular deflection of the 3 inch bellcrank versus the 4 inch bellcrank. I determined where I needed to drill the push rod hole based on these calculations to make the control systems equal and built the plane with a modified 3 inch bellcrank.

To this day, I cannot tell the difference at the handle when I'm flying. The controls in my classic Oriental move the same as the controls in my big ship. I want and need this similarity because I don't want to waste time getting reacquainted with each plane.

My .02,

Ron

Paul Smith · « **Reply #21 on:** October 10, 2007, 09:18:27 AM »

Quote from: Alan Hahn on August 18, 2007, 06:05:02 PM

Tom,
Why doesn't simply going to narrower leadout spacing on the handle doesn't fix this?

In theory this would work:

Use a 1" BC and 1" handle spacing, or use a 3" BC and 3" handle spacing.

The problem is that the smaller system developes more torque and wears out faster. If a small system developes 1/32" of slop, it's worn out. A big system can tolerate a much looser fit.

On a bellcrank, the input needs to be limited to +/- 45 degress, otherwise the output side goes flat. It easier to keep big bellcranks within a smaller angle of movement. However, this is why HUGE bellcranks don't work either. A 6" BC would have such a small angle of motion that it would have no output, unless you used a 6" handle.

phil c · « **Reply #22 on:** October 10, 2007, 02:06:13 PM »

the biggest thing I see is that using a larger bellcrank gives you the OPTION of slowing down the controls and, even bigger, reducing the pushrod and bearing loads. If you use the exact same geometry on a 3 in. bellcrank setup and a 4 in. bellcrank setup the 4 incher puts a lot less load on the pushrods. Also, as Tom points out, the smaller bellcrank reacts faster to a standard 4 in. handle and going to an adjustable handle with the lines attached outside your knuckles makes the control forces you feel go way up. The overhang between the handgrip and the lines is just another lever- the longer it is, the harder it is to move the controls. The old EZ Just got it almost exactly right for most people with only an inch or so of overhang.

Leo Mehl · « **Reply #23 on:** October 18, 2007, 10:36:05 PM »

In the 60's we used very fast controls which meant that we had to stay at a constant attention during maneuvers. The total leadout pull from neutral was about one inch or less. I have built two classic planes lately and I went from an inch to about 2". What a difference this made as far as flying a classic plane. I have seen some of the Orientals that Don McClave has built and he still makes his controls fast. In any case the classic plane flys better with slow controls. Also most classic planes have shorter tail moments.

doug coursey · « **Reply #24 on:** December 13, 2021, 07:50:06 PM »

don still used 2 3/4 inch bellcranks in his stuka stunt with 45 degrees of flap and elevator....i know its old but i had to post this because im building a stuka stunt and going with an Okie 3 1/2 inch bellcrank. the wing is on the small side 47" wing span.

phil c · « **Reply #25 on:** June 22, 2022, 04:40:41 PM »

Quote from: Tom Niebuhr on June 25, 2007, 01:11:59 PM

There is no doubt that the larger horns and Bellcranks, are much better because they have a better mechanical advantage. just remember that that the actual movement of the surfaces are due to the relative distance between the holes.

The only restricting factor, in some cases, is the available space.

Dennis,
Can't to wait to see your progress on the "Swinger"
I talked to your dad.. sound like you and Archie are both back! Boy, is that great!

One "moment arm" that hasn't been mentioned is the natural movement of pilot's wrist and how far the lines actually move. A lot of people have somewhat limited wrist movement and can barely generate 1 in of line movement without using at least some elbow, or even shoulder movement. ps. a fair number of flyers also sometimes use wrist, elbow, shoulder together. This makes it heard to figure out what is causing them difficulities. I try to keep the forearm pointed at the plane, using mainly the wrist to get controlled movements.