Bellcrank bolts

I notice nowadays that there is only one bellcrank nut included in the kits we buy (also when we buy just a bellcrank assembly). I always use two- the first one goes on to compress the bellcrank platform between the head of the bolt and the nut. This makes for a very sturdy post to put the 'crank on. But if there's only one to be used after the 'crank is installed on the post, stresses/wear will eventually erode the hole in the platform. (I hope this is clear- it's tough to describe). Didn't bellcrank assemblies (Veco,etc)once come with 2 nuts and an assembly drawing showing how to use them? I think some C/L ARF problems (and others)could be alleviated by using the two nut system. I'm referring to 15-40 size planes- Busters, Rmasters, etc.

LAST EDITED ON Nov-06-03 AT 12:15 PM (CST)
 
Two nuts are really not needed......Although having two nuts gives a certain sense of security. Simply because if you were to lose one nut you always have a back up nut. I just don't know about jamming two nuts together???? Why would you want to do that?

But on a more serious note. I use a nylock to hold the bellcrank on or I use the single nut and put a bead of JB Weld on the top of the exposed thread. The JB Weld if mixed properly will never fail!

I think Dale was talking about putting the bellcrank on top of the first nut, with the second nut above the bellcrank...

Thats how read the question also...I cant really imagine doing it with only one, unless the platform is epoxied well enough around the bolt to make it as rigid as using the nut.

I suppose something other than a nut for the crank retainer function could be used as well but I've always used the two-nut system.

I knew that!

It's seems like placing a nut under the bellcrank would raise the crank to high in some installations. I'm not sure how that would add strength to the mount by using a nut under the bellcrank. Would a washer not accomplish the same thing?

LAST EDITED ON Nov-06-03 AT 02:44 PM (CST)
 
At my house the nut is attached to the bellcrank through ....about 65 feet of .015!

Crist Rigotti
"A driver trying to be a pilot."

>Two nuts are really not needed......Although having two nuts
>gives a certain sense of security. Simply because if you
>were to lose one nut you always have a back up nut.

I've always found that thought to be a great comfort...

J

I haven't used a bolt and single bell crank plateform since the mid 80's. I use 1/8" wire and a small,long plate on the top and bottom, attached to the wing spares,ribs and sheeting. Never had one of these fail and it's easier to align your controls.

Dale,

...like Larry F. I've used the pivot pin a la mounts in foamies. Surface plywood pads on the sheeting (or in spars for built-up) to hold the 1/8" or 9/64" wire. Solid!

I also, still, use traditional plate-mounted bellcranks. The advantage of using a nut between the 'bottom' of the bellcrank and the ply plate may simply be a tad more clearance for the pushrod and leadouts.

As far as wearing on the plate, most good bellcranks have/had bearings arranged so that one part could be bolted fast to the plate with the other was free to turn on or in it. There was clearance, in other words, for the mounting washers and nuts... BTW, the ARF TF Nobler does use a nut under the bellcrank, and it is needed, to provide clearance for the pushrod.

If the pushrod rubs on the plate, wear may never become a problem. You are more likely to lose the model long before that due to stiff controls!

Lou
I don't use bolts in any bell crank. On a built up wing I use 3/32 bass wood about 1&1/2 inches wide and tapered to 1/4 inch at the ends. These are laid into the ribs, three ribs out both ways and against the spare. I then set my bell crank where I want it and solder washers to hold it in place. The bell crank mounts also double as a torsion spar, greatly increasing the strength of the wing.
This also makes bell crank alignment easier and installing the two mounts this way distributes the load threw out the wing spares and sheeting. Making it much stronger.

I do not use bolts or nuts in my bellcrank installs I use two 1/16 plywood plates . Here are some photos of my last bellcrank that I made I use 3/32 music wire and I with a brass bushing and I lube it with powdered graphit.

Lets try this.

LAST EDITED ON Nov-06-03 AT 09:29 PM (CST)
 
one last try.

Carl, that looks really fine! What is that bellcrank made of? Really "high-zoot".

Tim

The bellcrank is 1/8 fiber glass circuit board.

Nice work Carl

Dale,

Trying to answer your question here. Veco and old Fox bellcrank kits came with the bolt, two fiber washers, one metal washer, one lock washer and two nuts. The assembly was one fiber washer, bellcrank platform, one fiber washer, one nut, bellcrank, metal washer, lock washer and finally the other nut. These are the old ones we used in the 50's and I still use them on my profiles. I also have some Sig nylon from long ago. This wasn't a discussion about the best system but a question.

No offense intended for those who went someplace else. There are a lot better systems now but each of us use what we feel best for the application and construction.

If it's a plain nut you can squeeze it in a vise and make it a lock nut, it doesn't take much.

A better way would be to get a nylock nut or an all metal aircraft lock nut or crimp nut as it's called by some. The aircraft lock nut would be a higher quality grade 8 nut and comes in regular or a low profile version called a shear nut for use in shear only applications like bellcranks.

I use a 6-32 grade 8 socket head cap screw then a thick large area fender washer, bellcrank plywood drilled, tapped and glued with a drop of CA, a large area brass spacer to get the bellcrank height I want, the bellcrank with brass hub .025" thicker than the bellcrank bushing, lock washer, aircraft lock nut torqued on with blue loctite and, then I bung the threads with wire cutters. After all that I realize the pushrod's on backwards lol.

Giffy

Skip the bolts and nuts...Larry and Carl are doing the best thing for free moving bellcrank installations.

John Ashford has the answer I'm talking about. The old kits DID have 2 nuts-as I thought I remembered them. With only one it doesn't give a "post" to hold the bellcrank solid. During a pull test, if there's a stack of components-washers, bearing,'crank and the single nut on top, the pull-force will tend to "tip" the bolt and elongate the hole. This couldn't happen if the bolt (post) had a nut run down it to secure it to the platform first. I'm just being a BOM showing how things were so much better in the "good 'ol days! Also I'm feeling guilty for not learning to send pix in to the forum to explain my rambling.

LAST EDITED ON Nov-07-03 AT 00:16 AM (CST)
 
Hmmmm...

I suppose putting one nut under the bellcrank works if the bellcrank isn't of the bushed sort (like SIG and Brodak/Top Flite ones), but is it really necessary with bushed bellcranks? The same applies to metal bushed bellcranks like the Perfect (I don't trust these - I've seen them butterfly) or Fox (much sturdier) - wouldn't a washer underneath provide more of a mating area for the bushing?

I use a nylon insert lock-nut to hold the bellcrank down.

Some of my classic planes sort of demand the single shear mounting on a single platform. I prefer double-shear any time it is possible, for, as Isky mentioned, the 'Butterflying' of a Bellcrank on a pulltest. Carl, are you installing two plywood platforms (over & under) and are you attaching them to the fuse? Is the 3/32" pin removeable from some 'capped' vertical bore, and how is it retained? Noting the length of installed bushing, I surmise the distance between upper & lower platforms to be 1/2-3/4". Could you provide some insight here? Thanks, guys, very astute thread.
Mike

Or worse.. in a Combat match. In one particular instance, this also prevented the shutoff from working, since it was built into the bellcrank.

Another 2c worth...

Big difference between a Ringmaster and a full blown Stunter. The screw with two nuts assembly is great for a Ringmaster. I also like to have the bolt held to the plywood plate with a nut, fender washers and CA. You can tighten the second nut without needing to get to the bolt head and that sucker isn't going anyplace without tearing out the ply support.

The suspended bellcrank is the only way to go on a full stunter, plywood plates holding the music wire shaft on top and bottom of the wing, large enough to tie into the fuselage sides.

Works great, paint it green, won't rust..

Hi there,
I use a 4/40 blind nut,remove the spikes with pliers,light file to remove burr and this will act as the first nut installed onto the bellcrank mount which will give you your solid post.Make sure this nut is fitted with the centre cylindrical part showing as this is your bearing surface for your bellcrank.Next step is drill bellcrank out to 4mm and fit to bearing surface,use thin washers to shim assembly so as when you fit the other nut it just leaves the slightest movement for a friction free setup.

>Another 2c worth...
>
>Big difference between a Ringmaster and a full blown
>Stunter. The screw with two nuts assembly is great for a
>Ringmaster. I also like to have the bolt held to the plywood
>plate with a nut, fender washers and CA. You can tighten the
>second nut without needing to get to the bolt head and that
>sucker isn't going anyplace without tearing out the ply
>support.
>
>The suspended bellcrank is the only way to go on a full
>stunter, plywood plates holding the music wire shaft on top
>and bottom of the wing, large enough to tie into the
>fuselage sides.
>
>Works great, paint it green, won't rust..

Seems like that would be heavy, I've done three Ring Masters this way.

Dale
The bellcrank mount that Al Rabe designed for the BBQB and
Snaggletooth 2003 is what I am putting on all my new airplanes.
It's simple,Very strong, light, and no nuts to vibrate loose
over the years. IMHO
Andrew Raney