Author Topic: Two Sided Bellcrank (Read 1208 times)

Ken Culbertson · « **on:** June 12, 2020, 12:51:31 PM »

Does anybody make a 4" two sidied bellcrank? I am designing a Canard and I think i am going to need one.

Ken

bob whitney · « **Reply #1 on:** June 12, 2020, 05:39:18 PM »

Sorry, what is a 2 sided Bellcrank

Peter Nevai · « **Reply #2 on:** June 12, 2020, 06:20:52 PM »

I am thinking it is something that looks like an X instead of a T ?

George Truett · « **Reply #3 on:** June 12, 2020, 06:40:42 PM »

I may be missing what you're trying to do, would this connector from DuBro work for you?

Tim Wescott · « **Reply #4 on:** June 12, 2020, 06:53:25 PM »

Whack one out of 1/8" phenolic, and it can be whatever shape you want. I make all my own bellcranks these days.

Ken Culbertson · « **Reply #5 on:** June 12, 2020, 09:29:32 PM »

Quote from: George Truett on June 12, 2020, 06:40:42 PM

I may be missing what you're trying to do, would this connector from DuBro work for you?

I am designing a Canard and I need to drive the surfaces from both sided of the bellcrank. "+" shaped vs "T".
I need the Canard and elevator horns on the bottom, flaps on the top. Only way to do that is to drive them from opposite sides of the BC. I would make one but I don't have any tools.

Ken

PerttiMe · « **Reply #6 on:** June 13, 2020, 01:23:20 AM »

Are you thinking 3 control surfaces: canard, flaps, and conventional elevator?

Are you sure it needs flaps?

John Park · « **Reply #7 on:** June 13, 2020, 01:52:36 AM »

On my last two flapped profile models, I've used home-made X-shaped bellcranks - mainly for aesthetic reasons, to avoid the sight of that big flap-horn, complete with elevator push-rod, sticking out above the wing. I link the inboard pushrod hole to the flap horn (on the underside of the flap) and the outboard pushrod hole to the elevators with the pushrod emerging from the underside of the wing. I make all my own bellcranks: I have a good stock of 1/8" phenolic ("Paxolin") material that I've always found satisfctory.

Keith Renecle · « **Reply #8 on:** June 13, 2020, 03:56:18 AM »

Hi Ken,

Do you mean something like the Big Tiger from Claus Makis?

George Truett · « **Reply #9 on:** June 13, 2020, 06:52:30 AM »

I think I would give Russell at Okie Air a call.

Avaiojet · « **Reply #10 on:** June 13, 2020, 07:03:47 AM »

Quote from: Ken Culbertson on June 12, 2020, 09:29:32 PM

I am designing a Canard and I need to drive the surfaces from both sided of the bellcrank. "+" shaped vs "T".
I need the Canard and elevator horns on the bottom, flaps on the top. Only way to do that is to drive them from opposite sides of the BC. I would make one but I don't have any tools.

Purchase two 4" bellcranks and place one on top of the other just in different directions. There's your +.

Use small bolts at each end to hold the lines.

Ken Culbertson · « **Reply #11 on:** June 13, 2020, 07:10:44 AM »

Quote from: Keith Renecle on June 13, 2020, 03:56:18 AM

Hi Ken,

Do you mean something like the Big Tiger from Claus Makis?

That is it. I no longer have a shop or I would make one. Thanks for posting the link.

Ken

Ken Culbertson · « **Reply #12 on:** June 13, 2020, 07:13:04 AM »

Quote from: Avaiojet on June 13, 2020, 07:03:47 AM

Purchase two 4" bellcranks and place one on top of the other just in different directions. There's your +.

Use small bolts at each end to hold the lines.

I may have to do that. I don't know of any 4" metal ones. The composite ones are too thick.

Ken

John Park · « **Reply #13 on:** June 13, 2020, 07:15:21 AM »

Quote from: Keith Renecle on June 13, 2020, 03:56:18 AM

Do you mean something like the Big Tiger from Claus Makis?

I thought I'd invented the idea - until one day, looking through back numbers of AeroModeller, I came across that plan. Of course, it had lodged in my subconscious, to resurface as called for!

Ken Culbertson · « **Reply #14 on:** June 13, 2020, 07:37:47 AM »

Quote from: PerttiMe on June 13, 2020, 01:23:20 AM

Are you thinking 3 control surfaces: canard, flaps, and conventional elevator?

Are you sure it needs flaps?

I have considered that. I am using Wolfgang's research and he says yes to the flaps. I am trying the Canard for one reason only - getting the plane to fly tangent to the turns at the visual center. I have done that without the canard but the CG is too far back for my 73 year old reflexes making level flight too intense to lock. This looks like a solution and I am one of those fliers who is always open to trying something new. The traditionalists are already on my case but that is OK, if it doesn't work I can just cut it off. It is electric and there is a 3" section that can be easily removed.

Just for the record, there is absolutely no competition benefit for me to do this. In fact, it might actually hurt with some judges. I am doing it just because, and that is enough reason for me.

Ken

Ken Culbertson · « **Reply #15 on:** June 13, 2020, 07:58:29 AM »

Quote from: Motorman on June 13, 2020, 07:53:18 AM

$12 shipped Double throw X bellcrank 1/8" phenolic with 3/8 center hub. 5 x 1/8 holes to your specs. 4" x ?

Motorman

Worth it. I will draw it up next week and send you a PM with the specs.

Ken

Avaiojet · « **Reply #16 on:** June 13, 2020, 08:05:53 AM »

Quote from: Ken Culbertson on June 13, 2020, 07:13:04 AM

I may have to do that. I don't know of any 4" metal ones. The composite ones are too thick.

Ken

The thickness makes no difference. You could argue about weight?

See what Okie Air has. A good place to start.

You do know 3" ballcranks were once popular. 3" bellcranks will get the job done and there's plenty of 3" FOX bellcranks available.

That's all I use and I layer one on top of the other.

I've never seen/handled a 4" bellcrank.

I don't even know what the advantage is? My guess, just a guess, the advantage is at the wrist and not in the model? Good or bad guess?

Do you have a drawing of your model?

Ken Culbertson · « **Reply #17 on:** June 13, 2020, 11:48:41 AM »

Quote from: Avaiojet on June 13, 2020, 08:05:53 AM

I've never seen/handled a 4" bellcrank. I don't even know what the advantage is? My guess, just a guess, the advantage is at the wrist and not in the model? Good or bad guess?
Do you have a drawing of your model?

Trust me it is huge. Considerably more leverage meaning less wrist pressure on the corners. Although you can trim for a 3" the additional leadout movement you get with a 4" makes adjusting the line spacing much easier. I have a pix on my build thread but I will repeat it here for you. III is a 3" nose extended II with the Canard.

Ken

Avaiojet · « **Reply #18 on:** June 13, 2020, 04:51:30 PM »

Quote from: Ken Culbertson on June 13, 2020, 11:48:41 AM

Trust me it is huge. Considerably more leverage meaning less wrist pressure on the corners. Although you can trim for a 3" the additional leadout movement you get with a 4" makes adjusting the line spacing much easier. I have a pix on my build thread but I will repeat it here for you. III is a 3" nose extended II with the Canard.

Ken

Oh my gosh!

I love it. I also love those that step outside the box. Congratulations!

Well, in this case you could say step outside the circle.

I wish there were something I could improve there but there isn't.

I do have a question though, hope you don't mind.

Do you think the model will balance as it currently is drawn, or do you think you should add a bit of length to the tail moment?

Charles

Ken Culbertson · « **Reply #19 on:** June 13, 2020, 08:47:46 PM »

Quote from: Avaiojet on June 13, 2020, 04:51:30 PM

Do you think the model will balance as it currently is drawn, or do you think you should add a bit of length to the tail moment?

Wolfgang Nieuwkamp ran the design through his modeling program that tests the forces at play against the C/G and he said to not change a thing. The tail movement is 19 1/2 now and the stab is 30%. Both are a bit aggressive. I am going to make the nose removable so that I can remove the Canard if it turns out to be a flop and not lose the plane.

Ken