Blanton bell crank

[Bill Ladd]

...As things are - for reasons that have nothing whatsoever to do with steel-building, I may never do either, and may never build, or even really play, a steel or any other instrument again in my life...

Oh man. I certainly hope that whatever is going on works out so that you are able to do all of that and more.

[Georg]

Sure, Bent. No problem. Didn't really see a serious one in the first place, but some clarification between friends is always good.

Will take me months to get my workshop/studio up to fully operational level again, and so far I can't even decide if it's worth bothering with. Consequently, I better leave all this stuff to the rest of you for the time being, since I can't/won't construct anything anywhere but in my mind anyway.

Have fun..

[Bent]

Georg, your mind is the most valuable of all tools and I am sure I speak for all of us when I say that your 'tool' is needed here.

Let's just let unfortunate words be exactly that and get back on track.

Bill, everything's cool. Thanks for your concern

[Ross Shafer]

I was pondering the adjustable bell crank conundrum a couple of months back and and managed to snag the very last one that Linkon had in stock to see how they skinned the cat.

The subject went off my radar until the last couple of days when I saw Bent's Blanton threads. My wife and I took a nice walk this morning and while we didn't end up talking all that much (that's OK we don't need to be yakking to enjoy each other's company), I did manage to finger out a way to skin adjustable bell crank cat that I think addresses some of the issues encountered. Lemme know if I'm missing something that will prevent this from working.

I've attached a pic of the Linkon version and a couple of pics of the parts I came up with in Solidworks. The assembly I've come up with is only .375" wide and the rods can be stacked up so the pull remain straight. The assembly I'm showing here uses a rod that is held to the pivoting pin using a set screw, but it could just as easily be a right angle bend on the rod with a circlip...doing it this way would allow a liitle size reduction. For various anal retentive reasons, I prefer the straight rod/set screw system better myself. A small circlip under the bell crank body at the top of the height adjustment screw and an unthreaded recess for the tip of the same screw keeps it in place.

I'm not sure I'm happy with the access to the bell crank/cross shaft binding bolt, but it takes care of twist issues...it does require that the cross shaft be a bit further from the underside of the body though. I'll be chewing on that....

Happy Thanksgiving!

adj bell crank.JPG (37.68 KiB) Viewed 1380 times

adj bell crank 2.JPG (31.47 KiB) Viewed 1380 times

Linkon.JPG (40.76 KiB) Viewed 1379 times

[Bent]

Ross, your adj. crank looks good! The .375 - is that the widest point? I guess that's the rod clamp.
The square hole for the cross shaft - I can't see much of a problem bringing it around so that the clamp screw is available from above? Also, what about the unique Blanton clamping for a round cross shaft? I am sure it will work on a properly desgned shaft, and not the smooth hard stainless shaft that I used. Milder steel would make for better clamping with a set screw.

[Ross Shafer]

Thanks Bent,

As currently modeled this puppy is .375 at the base and at the rod pivot. Thats using a .125" rod, so it could be a bit narrower with a smaller diameter rod. Even with the .125" rod, the whole thing might be able to be slimmed down...just depends on how much flex (if any) there is in the upright portion o the bell crank.

Definitely not a prob to put the binder on the side instead of the bottom. I like the idea of using a method that eliminates any twist potential...not that a bit of twist really messes with anything (except my admittedly anal aesthetic sense, hey I like looking up the skirts of these things as much as looking at the tops!). Just this morning on the SGF, I saw some Zum bell cranks that are done this way.

The Blanton cross rod attachment using the angled slot, works just fine I'm sure. I just prefer a clamp that doesn't scar up the cross rod if its not necessary. "Different stokes for different folks 'n all that.

I've got an idea I like even better for the cross rod attachment, but it necessitates a slot or dovetail cut into the cross rods....besides the extra machining, it would would have some impact on the cross-rod torsional strength. Probably not an issue. The bulk of my life's design/manufacturing and business life has been centered around the bicycle biz, which is a heavily liability prone industry. This has left me with a bit of a tendency to overbuild things.

Have a great weekend!

[burt]

This is an idea I've had for an adjustable bellcrank.
It will allow a straight pull, but, alas, any other rods off the same finger will have to go around this bellcrank.
First, cut this blank out of 1/16" steel plate

[burt]

Then bend it to this shape

[burt]

Now cut a blank for the roller holder/sliding element

[burt]

Bend it up so that it can slide in the bigger bracket, and weld a length of threaded rod (about 1/8" diameter) as shown in the diagram