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Topic: Aftermarket bell-cranks: a possible 'fix'? |
Roger Rettig
From:
Naples, FL
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Posted 21 Apr 2024 8:50 am |
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How did you manage that, George???
Yikes!
My guitar's on the bench as we speak...
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Roger Rettig - Emmons D10s, Quilter TT-12, B-bender Teles and old Martins.
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George Webb
From:
Mississauga, Ont, CAN
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Posted 21 Apr 2024 9:05 am
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Roger,
I don't have to tell you it's always an adventure.
Actually I removed the 2 knee lever mounting screws, pulled it up and it was easy from there.
Cheers
George |
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Wayne Brown
From:
Bassano, Alberta, Canada
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Posted 21 Apr 2024 11:33 pm steel guitar parts
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Thanks George those pictures really do help. Any chance anyone could get a couple of close up Pictures with the original rod etc installed on the guitar. So I can see how everything is originally placed.
thanks
wayne
_________________
Owner Out West Music,Seats,Parts and accessories
www.outwestcountry.ca |
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Roger Rettig
From:
Naples, FL
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Posted 22 Apr 2024 6:21 am
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Wayne
Here's my RKR before it broke under the strain. Hopefully, you can see what you need in this photo.
Later (see earlier post), I doubled-upped the BC and connected them with screws. Bobby Jones was kind enough to fabricate two heavy duty BCs; I'm in the process of fitting at least one but I think I will have to drill a hole in it and connect it that way to the resident 14-hole crank.
I need a drill-bit first!
I just checked my post; the photo shows RKL, but you can see the base of RKR and the rod coming up at 45 degrees.
_________________
Roger Rettig - Emmons D10s, Quilter TT-12, B-bender Teles and old Martins.
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George Webb
From:
Mississauga, Ont, CAN
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Posted 22 Apr 2024 7:44 am
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Hi Wayne,
Sorry, I should have sent these as well.
The knee lever has a thin section with the rod hole in it.
George
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George Webb
From:
Mississauga, Ont, CAN
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Posted 22 Apr 2024 7:53 am
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Roger,
Here's my 'fix'. I added a second bellcrank similar to yours and put screws and nuts between them. The screws go through to the half stop bellcrank as well.
So the 'push' force from the knee lever now gets to the shaft via 3 bellcranks.
Cheers,
George
.ps You're not the only one who had a Meccano Set as a kid!!
Last edited by George Webb on 22 Apr 2024 9:37 am; edited 1 time in total |
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Wayne Brown
From:
Bassano, Alberta, Canada
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Dave Magram
From:
San Jose, California, USA
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Posted 25 Apr 2024 9:45 am
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Many years ago, I worked as a machinist making parts for aircraft, mostly out of aluminum because of its light weight. Aircraft-grade aluminum is quite strong, but rather soft, compared to steel.
Machined aluminum parts that receive forces from two different directions—as bell-cranks do—are prone to stress fractures if their corners are machined as simple 90-degree angles.
To reduce the possibility of stress fractures, such vulnerable aircraft parts had a concave “fillet” machined in their corners, as shown in the diagram below…
Not all steel-guitar manufacturers make such vulnerable parts with fillets. Several years ago, I replaced a knee lever on Bobby Black’s Carter D-10 that had developed a stress fracture similar to the drawing above—and was rather surprised that the company was not using fillets for added strength on such a high-stressed part.
For more info:
“What Is the Purpose of a Fillet?
Fillets reduce stress concentrations in changes of section and direction on a part. They increase the part’s load-bearing capacity and fatigue life. Fillets accomplish this by distributing stresses over a larger area...”
https://www.xometry.com/resources/3d-printing/fillet-vs-chamfer/
-Dave |
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Dan Galysh
From:
Hendersonville, Tennessee, USA
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Posted 25 Apr 2024 10:19 am
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| The infamous RKR bellcrank split. I kept a couple extra bellcranks in my seat because this happened more than once. |
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Roger Rettig
From:
Naples, FL
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Posted 25 Apr 2024 11:55 am
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Dan:
My RKR has protested much more often since I added the 10th string B to A lower.
Before that, I went 18 years on this LeGrande without it letting go. 
_________________
Roger Rettig - Emmons D10s, Quilter TT-12, B-bender Teles and old Martins.
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