The Steel Guitar Forum

That's absolutely silly, Chris. A steel guitar can't violate the laws of physics. We don't need "scientific evidence" to prove that. Nobody is claiming magic.

Now, if I may, I'd like to address the issue of "two distinct axis of rotation". There are not two axis of rotation when using the bent crossbar. The axis is a line between the endpoints. Each puller intersects that line at a different point, so each has its own axis. That axis is above the crossbar on the E9th neck and below the crossbar on the C6th neck.

The net result is that there is slightly less vertical movement of pull rods on the E9th (since the center of rotation is above the crossbar), and slightly more vertical movement of pull rods on the C6th. I honestly don't know whether this is an advantage to the player or not. I'm just pointing out that there are not "two axis of rotation" as has been claimed. The axis is vertically different for each rod puller, depending on its distance from the end points of the crossbar. The axis are points on a diagonal line.

The double-U-joint solution would create two level axis.

The trouble is, Bob, the ends of the shafts and the correspoding bearings are not in align with the line you drew.

Bob,
I'm sure Dell turns the ends of the cross shafts to the proper diameter before he bends them. Once the cross shafts are bent the ends will not be parallel with the lines you drew. The ends with have to be positioned in some sort of self aligning bearing in order not to bind up when rotated.

In an IDEAL situation, one would prefer two distinct and PARALLEL axes of rotation. The bent rod concept does not support this. The two universal joint solution does. Erv's "pillow block" solution allows for the nonlinearity in the bent rod scheme.

Bill Stroud wrote:Let me tell you, I've got one of the most Pulls on a Steel that you would ever want, 10 Floor pedals 7 Knees that raises and lower strings on both the E9th & C6th neck at the same time.

b0b wrote:Now, if I may, I'd like to address the issue of "two distinct axis of rotation". There are not two axis of rotation when using the bent crossbar.

Chris Lang wrote:That's all well and fine, but the laws of physics are still around, being applied today! (except in the case of the mysterious bent rods)

Chris Lang wrote:
That's all well and fine, but the laws of physics are still around, being applied today! (except in the case of the mysterious bent rods)
Chris, It sure seems you are stating that the "laws of physics" don't apply to the "bent" cross-shafts in this response .

Chris Lang wrote: The laws of physics are still in play, but not in the case of the Mullen "bent" crossrod.

Chris Lang wrote: Have you tried the "hanger" experiment?

I thought Chris didn't mean to say that before, because there was no response to my question about which laws of physics are being broken in this case.

There is only ONE way this can work:
If you please go back to Bob's (b0b) post on page 5 where he outlined in RED a common axis, THEN the bearings or collars/bushings holding MUST be inserted into the rails at a 90Deg. angle to THAT (average inclined) RED line (IN Axis with that line)... in other words NOT "flat" relative to the rails. BUT, BOTH tips which insert into the bearings or collars/bushings would have to be bent IN LINE with that (Bob's) RED average axis!



If the bearings holding these bent cross shafts are inserted "flat" (axis at 90Deg) into the rails, TWO parallel axis will result. IF one or the other would "win" the result would be that the other section would NOT ROTATE but MOVE back and forth following a RADIUS which center is the axis which would "win". Obviously, both axis seek to win which, if there is not a substantial (mechanically inappropriate) amount of play in between the cross bar's shaft and the bearings or bushings/collars it is logged logged in would result in them being locked (or only able to turn as far as "play" would allow).


Another option would be -if we assume that the level difference between the two decks may be around 1/4"- to drill the rods off-center by an 1/8" so that both meet at a common horizontal axis and used pins to connect the shafts to the rails.


Physics is physics. There is no such thing as "bad" physics, you can't prove physics wrong or disregard it just because it's a steel guitar. Physics lead to mechanical results or, if not followed to bad mechanics.

Given the fact that I hope that I may assume that the good folks at Mullen Steel Guitars are dedicated to produce a mechanically sound instrument, I am inclined to suspect that they have indeed aligned their cross shaft's bearings or bushings IN LINE with the average slanted axis as suggested by Bob (b0b).

Self aligning bearings as suggested by Erv on page 5 too, MAY be able to meet that average axis. However, let me tell you this: In mechanics, self aligning bearings, just like universal joints (cardan) are not regarded as an adequate tool to transpose the axis of rotations at different angles, but merely meant to help adapt/compensate for minor, usually tolerance induced misalignment of an axis to be at 90Deg to the bearing's radius.

I find the Mullen approach "interesting" as long as it does not thrive on excessive "play" or on the premises that the shaft needs not to be able to fully rotate freely (which evidently would be "bungle").

... J-D

Chris Lang wrote: Mullen is trying to make their "bent" rods work, without regard to physics.