Bell cranks!

[Neville Legg]

I thought bellcrank  was one word? (is it one word or two?   the spellcheck keeps putting a red line under one word  ) Anyway, there was an article in the Aeromodeller mag some years back, (can't find it now) that showed a bellcrank that reduced the sensitivity around neutral, t'was a weird shape, anyone remember it? Also has anyone ever tried a circular crank in a stunter? I know they work in team racers and  speed models,

Cheers      Neville

[Dallas Hanna]

I thought bellcrank  was one word? (is it one word or two?   the spellcheck keeps putting a red line under one word  ) Cheers      Neville

If history is correct, then it's bell crank.

"A bell crank is a type of crank that changes motion around a 90 degree angle. The name comes from its first use, changing the vertical pull on a rope to a horizontal pull on the striker of a bell, used for calling staff in large houses or commercial establishments"

HH

[john e. holliday]

Ah the good ole American language, can't call it english anymore as I see it.  Remember when "aint" wasn't a word.  And look at how many words we have now a days that we didn't have when I was in school.  Like "cyber space", e-mail and so many others that have different meanings now than before.  I will have to go look again, but, I think I have seem "bell crank" and "bellcrank" on plans and in articles.  So who cares as long as we know what it is talking about.  Have fun, DOC Holliday

[Neville Legg]

Actually spelling wasn't the main thrust of my of post  ! But has anyone used a circular control system, or the crank that gave a smooth linear response? I must see if I can find the Aeromodeller article!

Cheers      Neville

[George]

I thought bellcrank  was one word? (is it one word or two?   the spellcheck keeps putting a red line under one word  ) Anyway, there was an article in the Aeromodeller mag some years back, (can't find it now) that showed a bellcrank that reduced the sensitivity around neutral, t'was a weird shape, anyone remember it? Also has anyone ever tried a circular crank in a stunter? I know they work in team racers and  speed models,

Cheers      Neville

Thanks, but since it ain't on a bell...I'll call it bellcrank.

I don't read Areomodeller, but what you describe was published in Stunt News some years ago as the "Expocrank". It never seemed to catch-on, probably because of its complexity. Now if someone produced and sold it, that might be another story.

George

[John Miller]

Actually spelling wasn't the main thrust of my of post  ! But has anyone used a circular control system, or the crank that gave a smooth linear response? I must see if I can find the Aeromodeller article!

Cheers      Neville

Ted Fancher was a promoter, and user of circular bellcranks in years past. I'll let him explain why he no longer uses them, as I might get my facts mixed up.

The Expo crank, invented by Fred Bachle, was also a featured article in Stunt News about 10 or 15 years ago. Larry Cunninham has done some work with it, and other than the inventor, may well be the definitive scource for information on this interesting control system.

Igor Burger also has a non-linear system designed to improve aspects of the flight envelope. I'm not sure, but he may have information on his system on his web site.

In my personal opinion, I see little real value with these systems, as with the feed back loop to the pilot, it is hard to percieve any differences to most of us. I believe it's far more important to get the geometry corrected, and when done, most of the problems that can be cured with only the control system, fall way into the background noise.

Having said that though, such ventures into control dynamics can, and do, lead to better understandings, and are worth while in that regards.