Bell Crank

I have been told not to make bell cranks out of aluminum the cables will ware a slot throught the bell crank. I have been told not to make bell cranks out of steel they are too heavy and the steel will ware the cables and they will break. I have been told not to make bell cranks out of brass, wood, fiberglass, plastic.

What are you making your bell crank out of?

What type design do you have?

Linen phenolic flat-stock.

3/16-5/16thk.

Curt

Dont use the paper phenolic material it isnt strong.

>Linen phenolic flat-stock.
>
>3/16-5/16thk.
>
>Curt
>
>Dont use the paper phenolic material it isnt strong.

If the phenolic stock is good (circuit board material) then G-10 fiberglass sheet stock would be great. Unless of course there is some concern that the glass fibers might wear the leadout cables...

Andy

Quite abrasive and I believe heavier.

I don't know who put all those restrictions on your creativity, but I would not agree with at least some of them.
Bellcranks can be made out of aliminum (not recycled beer cans, make sure it's 6061 or 7075 or similar), thickness depends on geometry and plane weight, but varies between 1/16" and 1/8". Never loop lead-out cable through any bellcrank; use music wire instead (see recent post by Igor Burger with lots of pictures).
I've heard that road signs are a good source of 1/8" aluminum. But please check with your local DOT (Department Of Transportation) before taking down that stop sign on the corner.
I've also used 1/4" phenolic (for the lack of 3/32") and 3/32" nylon, all with great success.
Steel can probably be used for bellcranks, but would require very intricate machining or bench file work to make them light enough, and those might flex some.
Wood, brass is not recommended, agreed (although I've seen plywood bellcranks on very low-end budget .15-size aircarft).
"Plastic" is too broad of a term - there are thousands of types of plastic, so if you don't know what exactly you're looking at, I'd avoid it. Nylon has been tested and works, as I said before.

My latest bellcrank is made from two layers of 032 alum, sandwiched around 1/4 hard balsa. Then I run a grade 8 steel 4-40 allen bolt with shoulder down through it at each end. Then wrap a brass eyelet on lead out wire just like the enf of a control line. The wearing surface is now brass on steel. Its not particularly light, but its strong and friction free.

Mike,

My latest one is made out of 3/8" aluminum. But it's machined down quite a bit. It's a horseshoe arm type like I've been making for 10 years. I like them thick to give some bite for the "ears", but they are hogged out quite a lot. Final weight for this last 4" job is less than the phenolic ones I've had.

... Nothing wrong with ANY material for bellcranks, IF the characteristics of the stuff are properly dealt with...

I use aluminum, bushed snug, but free, for cable leadouts. Reasons? Easily worked, reasonably available, custom sizes simple to make.

I'm just starting to try J-B Weld (slow) to hold the leadout bushings together. No track record, yet, but looks good so far. The bushings are, in effect 'spools' formed of short brass tube and fitted washers.

The J-B Weld 'glues' washers, brass tube and cable into one piece. The loose end of the cable is served-off per usual practice... Lately, I've wicked in 5-min epoxy to the binding wrap. Seems good, too, but again, no long term track record, yet.

Check out Small Parts, Inc. They have an online catalog, and they sell small quantities of all sorts of materials, including 1/8" sheet nylon.

I've made expocranks from 1/8" Lucite, which worked perfectly well, but actually bent noticeably under 45 lb pull tests. 1/8" nylon is more difficult to machine, but is more satisfactory.

There are several similar useable materials, like nylotron or PVC.

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"If you don't want to work, you have to work to earn enough money so that you won't have to work.." -Ogden Nash

>I have been told not to make bell cranks out of brass, wood, fiberglass, plastic.

Good advice! 4 packs of 3" Sig nylon bellcranks are available from Melvin Schutte of Topeka KS for $2 a pack. They are very adequate and durable bellcranks and work with either solid or stranded leadouts-6-32 bolts and nuts not furnished but cheap at hardware store.

This reminds me of the local economy conscious modeler who decided to make his own tanks out of balsa sealed with epoxy.
They were cheap and light. Unfortunately, they also did not work a lick.
This is the same guy who just wires open his RC carbs for CL use not realizing that the carbs will frequently sell for more that a proper venturi and needle valve.

BTW-he also made his own needles out of music wire. They didn't work either.

>
>Good advice! 4 packs of 3" Sig nylon bellcranks are
>available from Melvin Schutte of Topeka KS for $2 a pack.
>They are very adequate and durable bellcranks and work with
>either solid or stranded leadouts-6-32 bolts and nuts not
>furnished but cheap at hardware store.

Who is Melvin Schutte?

Is a "3 bell crank the total length or the length between the lead out holes? How thick and wide and strong is it? Is this for 1/2a or a larger airplane? How much is postage?

Most of the places that sell this stuff online have no pictures, not enough detail for me to know if this is what I need or not. Its sorta like gambling I won't take a chance and get something I don't won't.

Sig is the only place that has a bell crank picture in the book. Problem with sig is after postage 1 bell crank is $11.00.

Gary:

The Sig 3" bellcrank is good for 40 size planes. Try the Brodak site there are pictures of some bellcranks. Lonestar ( www.lonestar-models.com ) sells the 3" unit in bulk $6.00 for a dozen, plus shipping. They are listed under miscellaneous.

Sig produces a reinforced 4" model as does Brodak.

>Who is Melvin Schutte?

>Is a "3 bell crank the total length or the length between the lead out holes? How thick and wide and strong is it? Is this for 1/2a or a larger airplane? How much is postage?

Try MBS model Supply, PO Box 282, Auburn, KS 66402-0282 e mail [email protected].
Ask for a price list. Lots of good stuff reasonably priced. Very good bulk control lines. A good source for CL racing stuff.
The bellcranks are about 3/16" thick nylon, quite durable, for .15 through .40 size models. Actually would be OK on larger stuff as well. The 4" bellcrank is no "stronger", it just provides more leverage to the pushrod for a given amount of hand movement-sorta like power steering.

I would guess the 4 pack of bellcranks could be put in a small padded envelope and mailed first class for around $1. MBS says they charge actual postage rather than gouging you on shipping and "handling" as some shippers do. Very nice people.

Order from our host, Leonard Neumann. He stocks Brodak products, including bell cranks, i'm sure. He ships for next to nothing! He has lots of useful stuff.

>>Who is Melvin Schutte?
>Try MBS model Supply, PO Box 282, Auburn, KS 66402-0282 e
>mail [email protected].
>Ask for a price list. Lots of good stuff reasonably priced.
>Very good bulk control lines. A good source for CL racing
>stuff. Very nice people.

Melvin is a long time CL modeler who flys racing, carrier, and other events. His wife Brenda has been the CL Event Director (I think that is the title they give her) for the AMA Nationals for several years. I agree they are good people. They also carry some hard to find things like bladder fittings if you are flying combat and a great little handle for about $7 that I now have 2 of.

Bob Furr

My favorite bellcranks were the ones I made myself from 1/16" chrome-moly 4130 aircraft steel. I got some nice little ball bearings from Jerry Howell in Colorado Springs, and these were silver soldered as pivot. Of course, the braided cable leadouts had to be bushed with some aluminum tubing in the usual fashion. The job was labor-intensive, but they were simply great!

I got creative one day and made a bellcrank from 3/8" thick 2024 T3 aluminum. Then I pressed in a ball bearing removed from a small blower. Smoothest controls I ever had.

Her official title is Nationals Control Line Manager. The events directors are the ones who go to her for help when needed. Later, DOC